Current Trends in multi thousand dollar speakers

GregM-
"Ultimately, I respectfully submit that:

1) choose the speakers by concentrating on timbre, tonality, (and ultimately phase) characteristics in the range down to ~60Hz MAX."

You've just described my Hales Revelation Two's to a tee! ;-) I hope they last a looong time.. -jz

Agreed - I would add that higher impedance also almost always results in lower distortion in power amps.

Sean's assertion that an increase in impedance results in 'less power, less control' is incorrect. In fact 'control' (which is a poorly defined term and can only be related to damping factor) increases with impedance. Furthermore, many tube amplifiers will have lower distortion and greater power into higher impedances.

I think Sean is done w/ Audiogon. I've gotta say it's weird to know that my speakers on paper should sound a bit bass heavy or have some bass slop. I can't stand bass slop or low-end muddiness. It's actually one requirement for me in a speaker that the bass is articulate and well defined, not overbearing. If you want to hear heavy bass, try some of the new Martin Logans (Vantages or Summits)... now THAT is some serious bass slop!

Whatever happened to Sean anyway?

As this astute individual points out selecting the optimum speaker at the high end is difficult. And only a few points were made and as Sean has said there are many others. The problem is that there is no direct correlation between price and performance. I have not trusted ANY reviews ANYWHERE for the last 20 years. My suggestion is spend some money on a decent condenser mike [B&K] and stand, connect it to a laptop based spectrum analyzer and with some test CDs measure the response of the desired speaker yourself in the showroom. Mostly you will be shocked and very occasionally pleasantly surprised. When the objective measurement and subjective listening are both positive[a rare thing in the real world] it might be worth auditioning in your listening environment. The biggest ally of purveyors of big buck scam boxes is the ignorance of consumers. I found the best education was building loudspeakers and a sound engineering course. I have found fault with EVERY speaker I have ever listened to, Tannoy HPD & Monitor Gold 15in great imaging and good bass & mids in the right cabinet but early roll off and peaky ragged response in the treble and lacked the type of microdynamic detail a good planar can give. ESL III Aussie customs about the size of a large door had like the Quad 57 a distinct mylar coloration and beamy imaging in the treble Quad ESL 63 were like being punched with a feather. Great detail but no visceral impact.Finally with all electrostats ,snap crackle and pop are things I enjoy in my rice bubbles not my speakers. Apogee mini grands were one of the best but a pig for any amplifier to drive and the Bass modules were poorly integrated,I found them bloated and boomy. Klipshorns surprisingly good but rolled off at the extremes and a distinct horn coloration but was at least to my ears not honky or unpleasant. Home made Beyema based horns that were good enough to find fault with my test CDs but had early overload and intermodulation distortion issues and the treble although excellent drew attention to itself through poor positioning. Manger Zero boxes were detailed like electrostats but had a dip in the upper midrange and lacked impact but very good overall. Multi- driver loudspeakers have several issues 1. They need a complex crossover that is hard to correctly design and match as stereo pairs given the variability of manufacturing tolerance for dynamic drivers and crossover components 2. As previously mentioned unless they are located in a large dedicated correctly proportioned listening room with the correct acoustic treatment they can overload a room in the bass. 3. Distinct colorations between the different drivers handling different parts of the frequency spectrum and unless cleverly designed will always lack the imaging coherence of a point source like the Tannoys. The exeption being wide range line arrays. I am currently considering some Ambiance Reference 1600s that despite a slight comb filtering effect of the long ribbon and the slight artificial sparkle of the aluminum material used and an early roll off in the upper tip of the treble I find it very pleasant to listen to. I could go on but this would turn into a book. The bottom line is EVERY loudspeaker has some kind of issue and it is simply a question of finding one that annoys you the least or what it does best outweighs what it does least for YOU and that all comes down to individual taste regardless of price.

Sean, your comments remind me the owner's manual of Avalon Radian HC, where I read a lot about sealed vs vented, Q factor and transient's response, muddy bass of vented speakers, superior accuracy of sealed etc etc... Try a search. How Firebat said, Avalon also changed from sealed to vented and I'm curious if this change is a gain or a mistake for the bass accuracy and speed. Thanks, Luca.

Firebat: I'm not real familiar with these speakers, so i'll refrain from putting my foot in my mouth. At least on this occassion : ) Sean
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Sean:

What's your take on Neil Patel's Avalon designs? He changed from sealed to vented enclosures in 1998 but has them tuned below 20HZ. According to Avalon literature, the speakers are designed with respect to room acoustics, etc.

Sean, you're right, but there's that hint of condescension in your post that just doesn't feel right to me, as I've always been an advocate of FFR, for example, and AM a musician, for example. But I won't belabor this....

Pbb, I agree too, but must remind us that the holy grail here is often a PERSONAL spectral tilt! Since many types of listeners have different preferences here, it's reasonable to expect that assembling components (especially transducers) into a room is not necessarily simply a matter of buying a bunch of flat-response nice products. A study done a while back (was it noted in Dickason? I forget) noted that the general public preferred a 2db/octave downward spectral tilt (THAT'S warm!), musicians preferred a 1db/octave roll, whereas audiophiles preferred a 0 to 0.5dB/octave roll. How these populations were matched for sex and age would be interesting to note, as the aging male audiophile loses sensitivity up top...so is there a compensaory preference here, or is it just that cleaner, high res equipment is more easily "acceptible" if the top octaves aren't rolled.
It's pretty clear that once speaker/room setup is completed, and electronic components are set up, we chase minor spectral flavorings in cables to attain our personal "tilt". Hence the common tendency to chase rolled-top cables that are not-so-mysteriously labelled as "smooth" or "fat-bottomed", or more musical (warmer tilt?).
That speaker manufacturers all have their "house" reference tilts that they prefer is no mystery. As long as the resultant sound of these boxes IN YOUR ROOM agrees with the manufacturer's voicers then success can be had without much secondary tweaking.
Being a Bostonian, I've followed Aeriel's history, and having briefly used the same cabinet maker as Kelly, and can attest to the difficulties he had with QA of the 10T bass cabinets. I remember seeing 10T cabs lined up, seeing the minor variations in each. Must've driven a technical design engineer like Michael nuts. I jokingly offered to consult with him on QA, but had enough of a hard time getting just 20 pair of my cabinets made consistently from Pine & Baker. That Aeriel was able to get a scandinavian high precision cabinet maker with state of the science CCM to manufacture nice complex cabinet clones for him is only a credit to their manufacturing excellence. I can't comment on Aeriel's price points...nor Michael Kelly's preferred spectral tilt, but I would expect that his design work is top notch, and perhaps Aeriel's speaker components are pretty tightly controlled, yielding reasonably matched pairs that are close to design reference. Such manufacturing precision is not just the realm of the high end, bien sure, as Boston, Snell, Revel et al have sucessfully controlled manufacturing processes tightly. Although I don't generally like the voicing of most Boston speakers (except the VR-MX surround), they DO take care to make quite nice, cloned tweeters that are much better than expected. Too bad they don't know how to implement them to my liking....
Sorry for this messy post...got interrupted by Ellen's matzoh pancakes!

Sean, I have to agree with you. You are rowing against the current though, since audio is now firmly in the "subjectivist" camp where belief replaces facts. I keep reading more and more that flat frequency response in-room is not where it's at. I remember Thiel being slammed for that "flat in-room" thing. Dr. Toole has been slammed on numerous occasions for applying science to speaker design and his work, following that of Roy Allison, in taking the room into account in the design of speakers, has been ignored. The prices are insane, but most everyone thinks that more money means better sound. Who is the writer in Stereophile, not long ago, who opined that since microphones used in recording are not linear, why should the rest of the chain be. So what hobbyists actually want nowadays is to mix and match a bunch of equipment that colours the sound this way or that way and when they are either too poor to continue, fed up with incessant "upgrades" or have gained the peer group acceptance they crave, they declare their system "done" and move on to another hobby. It simply is boring to think in factual terms and have a decent speaker system that costs too little. Strangely enough, the myriad of speaker “manufacturers” (more rightly called “assemblers” IMHO) is based on the fact that speaker design is now pretty well formulaic and that building boxes to put drivers and x-overs in is not that hard a business to get into, so that what you have are “coffin makers” building speakers and going for high margins. Aerial seems to go one better: an outside company builds their cabinets to order. So now what you have are true “assemblers” who buy drivers from one company, cabinets from another, electronic components from another, put it all together and go to market asking 30K for a pair.

Ernie said: "Your posts are voluminous and helpful in reciting the liturgy, but in so doing sometimes mask objectivity. We know what we hear...and how it measured."

I guess that this is why "audio" will remain subjective forever. I know what i hear and know what i like. I'm sure that everyone else does too. The fact that what constitutes "poor sound" to me typically measures as such while others enjoy that sound makes the purchase of gear a personal decision, regardless of the facts involved. Knowing this, that's why i've stated many times over "buy what you like as you are the only one listening to it".

As a side note, there is gear that i like / is enjoyable to listen to even though it is highly "flavoured". Then again, i also realize this and would never consider such a presentation to be "accurate". Such a system would probably be owned and operated by a "music lover" more-so than an "audiophile". I don't think that either "label" is derogatory, they just signify different goals and listening preferences.

My comments were aimed at those that are interested in the "high end" reproduction of musical recordings i.e. those that seek both accuracy with musicality. Musicality by itself has many enjoyable flavours, but is only half the picture. If that is what someone prefers, so be it. I'm not here to tell them that they are wrong, i'm simply posting observations, comparing data and sharing a point of view. The fact that various points of view end up in debate is nothing new and is part of human nature.

I think that many folks have found themselves in one camp or the other, not by their own doing or ears, but by misguided suggestions from the press and marketing hype. Introducing facts into the equation may initially confuse and upset them, but in the long run, i was trying to help them become more informed and capable of making better long term decisions. After all, the more that you know about a subject, the more likely you are to be happy with the choices you make. Sean
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Sean, I DID read Dickason a decade ago, and contributed to the design of a couple of vented 2 ways with two pro designers. We ended up with a VERY fast and tight 2 way with a 35Hz vent. Was supposed to be an OE for Roland Digital Pianos, but never got past the first 40 pair or so.
The bottom end alignment was done by an old student of Peter Walker, using a dandy Peerless $40 woofer. I don't remember the electrical particulars, but it was a very quick, non-bloated design that was VERY dynamic, and impressed the handful of dealers I demo'd it to on the East Coast. It was a bit lean in free-space, so had to revoice it (damp the tweeter), but with a bit of normal boundary support (atop a piano or nearer a front wall) it sounded great for a modest 2-way with $300/pr total manufacturing cost....
Duke, you're absolutely correct...building a fast, damped, efficient vented design isn't that hard, although you're correct, Sean, it isn't done often due to market motivations. And what's wrong with poor performance below 30-32 Hz? These, and other well-designed modest vented two and three-ways are for MUSIC, not helicopters and earthquakes! Your posts are voluminous and helpful in reciting the liturgy, but in so doing sometimes mask objectivity. We know what we hear...and how it measured.
Cheers.

Sean, thank you for the kind words, but I think you are more than capable of taking care of things here. You prove yourself here on Audiogon on a day in - day out basis. You demonstrate knowledge, experience, curiosity, truth, and passion when it comes to audio. And, you probably know that that statement right there is the highest praise I can ever bestow on anyone here on Audiogon.

Incidentally, my initial impressions of the TL speakers I have right now are incredibly favorable. While "only" sporting an 8" woofer, the size of the cabinet is pretty large, and I am quite impressed with the bass response. In my room, it is probably as good as things can get. I think we sometimes lose sight of the fact that a room will support a certain level of low frequency response, and again, I believe these speakers are putting out as much as the room will allow.

The AtmaSpheres are having no trouble at all with these speakers. Despite the "conventional wisdom" that TL drops efficiency by about 3 db, these relatively unmuscular amps are driving them to very high sound pressure levels, with explosive dynamics, without any strain whatsoever. I now subscribe to the other theory, that a TL actully presents a kind load to an amplifier. OTL amps do not normally take a hold of a woofer's voice coil, but in this circumstance, I have no complaints. In fact, the sensitivity is quite close to my Coincidents, which are incredibly easy to drive. My Line Tunnel Fried A/6 are not as efficient as these.

I will nevertheless try other amplifiers just to see what more they coax out of these speakers.

Overall, I am now more convinced that TL bass is the best one can get. There is a unique rightness to it, in addition to the weight and thunder. However, I will say that the Coincident Troubass subs(with a larger woofer, in a good sized cabinet) that I have do not take a backseat to these speaker's low frequencies, and I wonder if the added complexity of a TL is required. Perhaps in a different room the superiority of this design would be allowed to come forward, if it is there.

So, in the end, I think that while the TL reigns supreme, one should see if the design merits a purchase for them.

I use to sell the Hegeman model one speaker...back in the early 70's....I think thats what it was called. It did have a metal cone woofer mounted at the top on an angle with the tweeter mounted separately above the woofer dust cap. The tweeter I believe was a Philips dome ..These speakers had the best bass of any in that store..Even at my young age then..I new there was something special going on, the bass was fast and tuneful..though easy to overdrive..these speakers were maybe less than $400 a pair..Tom

Duke: Traditional vent systems typically tune the vent at the same appr frequency that the woofer resonates at. This produces two smaller "humps" rather than one larger hump. Bandwidth is increased and overall bass sensitivity also climbs over a wider region.

By doing so, you've now got two resonant points, which are really nothing more than undamped oscillation from the driver and the vent. These are two points of oscillation that the amplifier can't load into or control ( due to impedance peaks ), producing twice the potential for music to excite them with the resultant increase in "slop" i.e. undamped / uncontrolled output. Couple this with the elevated output due to the increased sensitivity in this region and the "room gain" that naturally takes place and you can see why we've ended up where we are today with MOST vented designs.

The other alternative to tuning a vent is to let the woofer resonate where it wants to in that cabinet and then tune the vent for whatever frequency that you want to try and extend output to. While this does increase extension somewhat and produce a shallower roll-off ( with resultant improvements in transient response ), the lowest region isn't as efficient as the upper region. This "can" produce a more natural presentation IF properly implimented, BUT, you've still got the associated phase shifts, lack of damping below the vent tuning frequency and reduced power transfer / lack of control associated with higher impedance peaks that vents typically demonstrate. In plain English, we've still got plenty of side-effects / problems to deal with using such an approach, even though they aren't as prominent as the more conventional designs.

As far as various alignments offering a different set of trade-offs, I know this and you know this, but in order to educate and share with those less familiar with the subject, you have to start with a base-line that they may be familiar with. As you mentioned, this type of tuning is not commonly used. That is why i didn't base my descriptions / argument on this type of vented design i.e. it's not widely used. Having said that, there is one very well known ( but NOT widely respected by audiophiles ) manufacturer that advocates such designs. That manufacturer is Cerwin-Vega.

As a side note, Stewart Hegeman used a very unique approach when designing vented speakers that some might consider to be similar to the above. I can see how it could have quite a bit of merit if properly applied. There is only one "manufacturer" that i know of using such an approach and that is Don Morrison Audio. While i've never heard these speakers, they do seem to try and tackle quite a few important aspects of speaker design. Don has been working with this design over time and seems to be on the right track from a technical perspective. If interested, Don also makes a small two piece preamp that some rave about. I am NOT "endorsing" or recommending either of these products although i will say that Don seems to be more than technically competent. Having said that, his preamp should go lower in frequency response though : )

Other than that, i know that Richard Shahinian of Shahinian Acoustics has acknowledged that Stewart Hegeman was a primary influence on his designs. Given that Hegeman was also one of the first that i know of to use metal cones ( not just for tweeters ) in his speaker designs, i would have to say that his thinking was ahead of many others. The first speaker that i know that used actual "metal" in it ( but not the whole cone / piston area ) was the Ohm A. While this was a revolutionary design in itself, i could be wrong here and there might have been others using "metal" in their drivers prior to the first Walsh based design. Sean
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Good points Joe. Once again, you've added a brief but very cogent analysis of the how's and why's. In the future, i'll run my mouth / stir things up and you do the final presentation, okay ?? : )

Honestly though, the fact that you typically remain a "third party" in many of these posts and then summarize both points of view expressed sometimes helps me to see things more logically. There have been many times that you and a few others have added to the thread in such a manner that makes us think about the "big picture" and not just the subjects that we've gotten emotionally tied up in discussing in that thread. For that, i am grateful for your input and everyone else that contributes their thoughts. Even if they disagree with my thoughts : )

If anyone didn't follow what Joe was getting at, it looks like "high end" is following a logical progression. Some that never ventured into or just dabbled in a specific part of the "sonic stream" would actually call it "de-evolution" or "moving backwards".

If we think about things logically, most folks traded their warmer and more liquid sounding vinyl rigs as the primary source for more convenient digital based systems. Digital sounded like hell, but we somewhat got used to it over time. In most every case, digital was hard, bright, lean, lacked "PRAT" and was "soul-less" sounding, so in many systems over a gradual period of time, more and more tubes were introduced into the equation. This was done to try and make things both more listenable and "musical" again.

Given the added warmth and natural tendency to soften the treble response, this worked out pretty well. Only problem is, unless you have some of the best and most expensive tube gear available, tubes typically lack power output and current capacity. A such, the end users that didn't have "mega-dollar" / "built like a tank" tube gear ended up with bass was not what they were used to hearing.

To counter the shift in products being used, the manufacturers shifted from speakers that required a good amount of power with a more linear response to those that required less drive. While shifting to more sensitive i.e. "vented" designs, they also found that it was easy to artificially inflate the last few octaves of output. By doing so, the end users now had more bass, albeit all the time with less control, but their amps didn't have to work as hard to deliver low frequency output and current. This is because the speakers were already "hyped" in that region AND sensitivity is up. It was a "win/win" situation for those users that had systems that weren't balanced in operation and manufacturers / retailers that wanted to sell products.

The end result is that tonal balance was returned to sounding "warm & musical", even with using a digital source, but such results were achieved by introducing TONS of errors along the way. One "solution" created other problems that required further "solutions".

Same goes for those that stuck with digital and didn't use tubes. In many cases, they were using SS gear that was high in negative feedback, lacked both bandwidth and high current capacity and sounded "sterile" i.e. lean and hard. By adding quite a bit of measurable bass "weight" with the "new breed" of "audiophile approved" speakers, one didn't tend to notice how bright and piercing the treble was. Manufacturers were able to "kill two birds with one stone" i.e. both tube fans and those using lower grade SS electronics were satisfied.

As such, it would appear that the "high end" industry, their marketing departments and the "paid for by advertising" audio magazines aren't about "accurate musicality" at all. They are about selling complimentary colourations / sonic band-aids and telling you that they are accurate / sound "wonderful". Those that know how to read and interpret spec's know what is going on, but since the mass majority of user's don't know how to do this, the "audio guru's" were and still are "safe". Given the fact that we've been led down the path where "all amps sound the same" and "digital is perfect", most "critical" audio magazines have dropped test procedures and now rely stricly on subjective opinions. Those that can read spec's and interpret data on their own have been further alienated from finding out the "truth" and become disheartened with the industry as a whole.

As a side note, as much as i "bad-mouth" Stereophile, i still LOVE the fact that they provide some type of test bench measurements. Having said that, i still can't understand how someone could listen to a product and NOT know what they are hearing?!?! If all of this were not true, how could you explain someone ( end users & reviewers alike ) NOT noticing that a speaker has phenomenally bloated bass? To them, it doesn't sound "bloated" or out of place. This is probably because they've never heard a "linear" system with "accurate" tonal balance to begin with.

How could such a thing have happened? That's easy. They never had good vinyl rigs / proper phono stages "way back when" and were raised on "perfect sound forever". It's also possible that over the years, they've lost perspective due to lack of familiarity i.e. non-use of a good vinyl system. Obviously, this could skew one's perspective quite a bit.

As such, it seems like the culprit for all of our "troubles" and "major design changes" in the audio industry boils down to the introduction of sonically inferior digital technology some 20+ years ago. The audio industry and end users had to shift gears at that point in time, and looking back now, it would appear that it hasn't been a very smooth transition.

With all of that in mind, if you doubt that "digital is the devil" behind all of this, just ask Albert or Twl. They'll give you the low-down : ) Sean
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PS... If you like what you're listening to, that is what counts. As i've said before, "buy what you like as you are the only one listening to it". Saying and getting someone else to believe that is is "accurate" or "linear in reproduction" may be another story though.

Hello Sean,

Thanks for your reply. As far as how many production loudspeakers are using a slow-slope vented enclosure, the only ones I know of are the Classic Audio Reproductions models, though I expect there are more. I just haven't really searched for them.

Admittedly my post just above didn't address the topic of this thread, which has to do with trends in megabuck speakers. Rather, my point was that the standard set of generalizations regarding vented systems doesn't acknowledge the implications of more transient-optimized tunings.

One minor point - in tuning for a higher F3 and a more gradual rolloff, you actually use a much lower tuning frequency rather than a higher one - so the woofer is actually better protected against out-of-band signals causing overexcursion than with a more conventional vented tuning.

Improving the transient response of a vented alignment just makes it behave more like a sealed one, raising the F3 but lowering the F12, for instance.

Just for the record, my comments above are based on speakers I have built (or designed and someone else built) as well as on models simulated.

Having experimented with equalized sealed, vented, and transmission line systems, my opinion is that the frequency response curve is a fairly reliable predictor of subjective transient response. I'm under the impression that there's a mathmatical correlation between rolloff rate and transient response, which may or may not imply that it doesn't really matter how the rolloff rate is achieved (whether through enclosure design or speaker/room interaction or equalization). I'm not engineer enough to argue that point one way or the other.

Historically, I've preferred sealed over vented designs (and transmission lines and dipoles over both, though for different reasons). What has driven me to reconsider vented designs (in particular gradual-slope variations) is a heightened awareness of the advantages of very low power compression. You see, the woofers that offer the lowest power compression are best suited for vented or horn loading. And bass horns are just too big in my opinion.

Cheers,

Duke

I will have the good fortune of having a true transmission line loudspeaker in my main system for the weekend. It will allow me the opportunity to compare and contrast these two alignments in my room, using my system.

Heretofore, my experience with TL bass is that it has been able to achieve more realistic deep bass than ported speakers. Unfortunately, in only one circumstance have I heard them in what is a "good" room in the past. The pair I am considering did not impress me last year, which I in part attributed to the room, but it turns out the line was incorrectly damped and the crossover values were wrong. With the corrections, the bass was improved to a point, but I still feel they were up against the limitations of them being in a difficult room.

My room, being smaller, and possessing boundaries which should definitely show the speaker in a more favorable light, and also being familiar to me, will allow me to get a better handle on things.

One concern I do have is that the achilles heel of the AtmaSphere amps is there lack of low frequency sock. If I begin to feel this is taking away from the experience, I will be switching in the Jadis and/or NAD 2600A to get a broader picture of things.

Personally, despite all the discussion back and forth, I think Sean has laid out some very cogent arguments in this thread. The inherent benefits in the sealed alignment's ease of design and transient response make me wonder why the high end has gone so far in the direction of ported speakers in the past 15 years.

From memory, things were more balanced between sealed and ported in the past. I am unsure of how accurate the conventional wisdom of ported speakers gaining 3 db of loudness over sealed speakers is, but that is normally one of the first arguments thrown out there. I have been under the impression that the resurgence of tube amplification and musical tastes of late account for the scales being tipped in the way they have been, or at least a fair amount of it.

Duke: How many "exceptions to the rule" that you describe above do you know of that are being marketed?

Aside from the aspect of roll-off rates, changing the box alignment still doesn't deal with the lack of transient response / out of band port leakage / lack of damping / potential for over-excursion that comes with all vented designs. You simply can NOT take an out of phase signal and use it to reinforce the in-phase signal without multiple drawbacks / repurcussions. With that in mind, it is up to the designer to prioritize which trade-offs are most / least important. When one can avoid most all of these and achieve relatively similar / better results ( except for sensitivity ), there is only one reason to accept the trade-offs that come with vents. That reason would be a lack of available power, which is no longer applicable with modern day designs / technology.

As one tries to achieve greater extension via manipulating the alignment of a vented design, the transient response gets worse. If you want better transient response with a ported design, you have to limit the low frequency extension. Even if you take this approach, the woofer is still unloaded / lacks damping at frequencies below resonance. The fact that you've raised the F3 to obtain improved transient response now exposes the woofer to even greater potential for over-excursion due to having a higher resonant frequency. The higher the resonance, the more potential for woofer overload at frequencies below that point. On top of that, we still have out of band vent leakage to deal with.

One can play all day long with computer simulations, but you can't fight the laws of physics. There are trade-off's involved with every type of design. Rather than try to bend and twist the rules, developing even more problems with increased levels of complexity, why not choose the simplest design with the least amount of trade-offs and work towards optimizing that? It seems that man has a way of making the simplest things in life more difficult than they need to be. Sean
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Sean, methinks you paints with a wide brush:

"For sake of clarity, these figures are based on the accepted principles that vented systems fall at a rate of 24 dB's an octave and sealed designs fall at a rate of 12 dB's an octave..."

Either type can be tuned to have a different rolloff rate in practice. And especially in the case of a vented system, it's the exceptions to the 24 dB "rule" that are by far the most interesting.

Note that, given a 90 dB reference level (longterm exposure to which will lead to permanent hearing loss), a signal that's -12 dB at 25 or 30 Hz isn't much above the threashold of audibility. Of greater real-world interest would be the -6 dB frequency, in my opinion.

It really is quite easy to design a vented system with an approximately second order characteristic over the first octave or so of rolloff, below which what's happening is of relatively minor audible significance. Such a system would be about twice the size of a Qtc = .7 sealed box using a comparable woofer, but would have about 1/2 octave greater extension. Obviously this would involve a much lower tuning frequency than would be the "rule" for that size vented enclosure. But it's often the exceptions to the rules that are the most interesting.

If we're comparing equal-size enclosures, both with an approximately second order characteristic over the first octave or so of rolloff, having very similar -3 dB, -6 db and -12 dB points, then the optimal woofers would of course be very different. The sealed box woofer would be approximately 1.8 dB less efficient than the vented box woofer. In addition, the vented box woofer's parameters would be better suited for good midrange performance, which might make a significant difference in a two-way system. I know it's not quite as simple as I've made it out to be here (I've ignored the issue of minimizing coloration from the vent itself, for example), but my point is it's quite possible to design a vented system that embodies many of the desirable characteristics of a good sealed system.

Duke

El: If such is the case, why not just run an equalizer to fine tune the sonics to what one wants to hear? One can achieve such results without spending much money at all. What does it matter what the source of colourations are so long as one enjoys the final presentation?

I think that a lot of people that were striving for accuracy and thought that they were buying products that would give them that have been lead down the rose path, thorns and all, by the manufacturers and dealers that took their money. Of course, neither the dealer nor the manufacturer could have done this by themselves without some help, so that is where the audio press comes into play. Promoting the "flavour of the month" mentality surely hasn't helped the industry / end-users in the long run.

High end used to be about achieving accurate and musical reproduction of what is on the recording. Non-linear reproduction is not accurate and super-imposing excessive bass / treble or both onto every recording isn't exactly "musical" either. If one prefers such a presentation, so be it. I don't think that most people reading these forums would call such a presentation "high end" though.

Other than that, i think i've more than expressed my point of view on this one. I'll give it a break and leave those that are annoyed alone. Sean
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Sean...As you point out "pro" speaker systems are vented and produce lots of boomy bass. However, I notice that the majority of people on Audiogon seem to listen mostly to pop music. It is logical that their music should sound "right" to them through a boomy vented speaker.

Greg: Room gain is very difficult to calculate and will somewhat vary with size of the room and speaker placement within the room. This is why good engineers design a speaker for specific placement within a room. Bare in mind that i'm not just talking about bass loading characteristics either. That way, they can factor in specific low frequency reinforcement factors AND dispersion characeristics consistent with the placement that the speakers will be used in.

While many people don't take such things into consideration when making their purchases and can't figure out why their speakers don't sound good where they have them placed in their room, they may also be the same type of people that buy a 4 wheel drive SUV to drive around in the city and / or take long trips on the highway with. While one can argue "vehicles are a matter of personal preference", one can also say "mis-application of a product outside of its' intended use will deliver less than optimum results". One can use such a product and be happy with it, but that doesn't mean that something else that was more suitable for the task at hand wouldn't have worked even better.

This is why i've stressed factoring in room size and placement in varous threads. Great speakers in the wrong room and / or great speakers that are improperly placed soon become "bad speakers" that they can't get rid of fast enough. Too many folks end up buying speakers that were designed to operate in a different environment than how they want to use them and then end up paying the price.

Ernie: I would suggest that you read Vance Dickason's Loudspeaker Design Cookbook. Your understanding of cabinet size and bass extension / output needs some help. I don't mean this to sound rude, as i was under many of the same false assumptions when i first started reading / learning about speaker design myself*. The fact that there are loudspeaker designers / manufacturers that don't fully understand many of the variables involved speaks of how complex of an issue this really is.

Part of the extension / total output / lower F3 on a vented system comes from the fact that, with such a high amplitude peak at resonance, the output, which is frequency related, has to fall off quite a bit before going below the average output level.

For sake of an example, let's assume we have a speaker that averages 88 dB's across the band. Due to the undamped oscillation at resonance of the driver / vent combo, there is a +5 dB peak in the low frequency region. As we've seen, this high of a figure on a vented design is not unrealistic and is possibly even conservative on some designs. This means that at the point of resonance, the output of the speaker is at 93 dB's. It is only after the lowest tuning frequency of the vent occurs that the speaker begins to roll off. That means that roll-off starts AT the peak.

Starting off with such a high peak means that we now have to lose 5 dB's of output just to get back to the reference output level of 88 dB's. In order to find our actual F3 ( -3dB point ) of this design, we've still got to lose yet another 3 dB's of output. This would give us a total of an -8 dB drop before we actually made it to the frequency where F3 is measured.

As you can see, since roll-off occurs at the same rate that frequency is lowered, building in a bigger peak at resonance automatically gives you more extension. That is, as it looks on paper using a -3dB reference point. Other than that, one can introduce such a peak into a sealed system with an EQ and still enjoy the better transient response of the sealed box. If you want to mention the phase shifts that the EQ brings with it as being detrimental, i'd like to mention the phase shifts that the vent brings with it.

As to your question about "what's wrong with a 24 dB slope", that answer has to do with linearity, transient response and ringing. The sharper the slope, the poorer the transient response, the more ringing and the less phase accuracy. This is why most "high end" audio gear strives for wider bandwidth with gradual roll-off. Better out of band performance equates to better & faster in-band performance. Same goes for speakers.

The question here is does one want more total output with a lower F3 at the expense of added bass bloat aka "lack of control", reduced linearity, poorer transient response, etc.. or is a slightly higher F3 with improved transient response and linearity more desirable? Since F3 only tells a small percentage of the picture, take a look at this. For sake of clarity, these figures are based on the accepted principles that vented systems fall at a rate of 24 dB's an octave and sealed designs fall at a rate of 12 dB's an octave:

-3 dB's on a 40 Hz vented system
-12 dB's at 30 Hz
-24 dB's at 20 Hz.

-3 dB's on a 50 Hz sealed system
-12 dB's at 25 Hz
-24 dB's at 12.5 Hz

While the initial -3 dB point on the vented design looks better on a spec sheet, it actually offers LESS extension when all is said and done. This is true even though the sealed design looks "weak" at an honest 50 Hz rating. On top of that, the vented design has all of the other problems i.e. reduced transient response, increased ringing, more phase errors, out of phase leakage from the port into the upper bass / lower midrange region, etc... You have to deal with all of these sonic drawbacks as tis type of design tries to get you the limited extension that if does offer.

This is not to mention that the vented system is completely "unloaded" or "undamped" below 40 Hz. Any low frequency notes fed into the speaker below that point will only result in massive excursion with the potential for damage / increased distortion. If you've got vented speakers and play vinyl, DO NOT try to play massively warped records at high volume. This will cause MASSIVE "woofer flutter", possibly resulting in permanent damage.

As a side note, it is quite possible to design a bass hump / resonant peak into a sealed design. By increasing the Q, you get such a peak. Like the vent, the transient response is reduced and ringing is increased, but unlike the vent, the slope remains shallower and phase integrity is not damaged quite as badly. As such, it is possible to match the F3 of a vented design with a sealed design, but the benefits of improved transient response are partially negated.

Vented designs DO look "more impressive" on paper, but that is only because the spec's that we use to quantify the performance of speakers aren't quite as sophisticated as those that we use for electronics. On top of that, there is no such thing as electronics / room interphase like there is with speaker / room interphase.

Vents vs sealed boil down to quantity vs quality. Vents will almost always give you more total output, but at great expense. Sean
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*To be honest, i was under the impression that vented systems allowed smaller cabinet size and greater extension for many, many years. I could never understand why someone would want to buy a bigger cabinet that didn't play as low and took more power to operate. That's because i was reading spec's but didn't know how to interpret them, nor had i actually listened to a lot of sealed designs at that point in time.

The reason why the sealed cabinets were "bigger" was because they were properly designed and tuned for extension. The vented cabinets were tuned for more apparent bass and higher output i.e. the illusion of "deeper" bass via "more" bass. This is how most "Pro" speakers are also designed and you can see further evidence of this by reading Bill Fitzmaurice's articles in Audio Xpress.

Ernie, I'm piping in here:

what's wrong with a 24/dB drop below, let's say 30-40Hz (...) if a properly designed vented cabinet uses a nice low Fs, and the driver's happily within its excursion limits

It doesn't sound impossible -- BUT:
Problem seems, it's not very easy to do and COSTLY. The cabinet would be very large (and/) OR, the "clarity" of the bass reproduction, as in how many bass "notes" actually come across, could (still) suffer...
More to the point the COST of the appropriate driver(s) could easily skyrocket the retail price of the speaker. Example: an average Lambda woofer (they have good /reasonably priced woofers) costs $~280ea; say the manufacturer buys these at $150/pair --

So? We've just added $1500 to the retail price of the speaker for an improvement which, while laudable for US here, is UNlikely to:
a) move opinion-"leaders" (i.e. reviewers)
b) be appreciated & impress many potential buyers, when the speaker is auditioned within the confines of a dealer's (or the buyer's) average listening room and the response anomalies most rooms produce in the bass

So, it's not likely to skyrocket sales... which is what manufacturers need in the first place (I'm not saying that's a bad thing:))
Cheers!

The "thickening" in response when one tries to get more bass warmth by taking advantage of walls' reinforcement is more due to the automatic "revoicing" of the upper-bass/low-mids region due to the change from in frequency of the 2pi/4pi transition. MOST speakers sound muddy and congested when wall/floor mounted if they're designed to work in free space. It's interesting to note that the JM Labs and PSB surrounds seem to be their normal 2 way monitors stuffed into a different cabinet, without modification of the crossover, and hence these speakers sounded quite wrong when wall-mounted, yet very nice on stands. OTOH the Boston VR-MX surrounds, for example, sound very well balanced when wall-mounted, being voiced that way. Indeed some speakers do require some front wall support for proper bass response, but there's a pont where the boundary support frequency "lift" band goes up as the distance goes down, until when wall-mounted, the speaker usually sounds congested in the lower mids.
Sean, great post, but again, if a properly designed vented cabinet uses a nice low Fs, and the driver's happily within its excursion limits, what's wrong with a 24/dB drop below, let's say 30-40Hz? Of course "sealed" is easier to get right, but the total bass power response always requires a bigger cabinet.

Isn't it utopia (no pun) to expect full-range response from a commercial passive, dynamic speaker??

Ultimately, CAN there be such a thing as a passive, dynamic, FULL-range speaker within physical & electrical & COMMERCIAL reason???
Let's look at rule of the thumb parametres of a "good" speaker -- as we've discussed it 'till now.

Take good sealed box with a Fs say of 60 Hz (not bad!). Say we equalise it (we're making happy assumptions here, and considering an anechoic room) to reach 30Hz (i.e., we need to equalise ~12db/octave). Already, that one octave will require an extra 16x as many W to reach the same spl as the 60 (as in W=P^2/rho).
Now, the original 60 was quite impressive anyway, and probably required some equalisation in the first place (say, baffle step, etc) so there is some extra energy used there too. Say a 6db/octave loss from 120Hz -- so we need 4x the watts from 120 to 60.

In other words, for 1W at 120Hz, we'll use ~65W for our 30Hz. Looks OK? Think about 2W at 120 requiring ~130W for the 30Hz. And so on...

The results in W availability look staggering. Hardly atractive in a commercial product...

Or are my numbers wrong (which they could be:))?. Or does in-room compensation save the day -- by how much??? +2-3db?? Still, that doesn't save us from having to opt for Sean's kWatt amplification -- and Sean's only using that for his BASS drivers... other amps(s) drive the rest of the speaker...

No wonder some people in the past used Onken for the low bass... No wonder, bi-amping is in the air!

Cdc: While i personally believe it takes "big power" to do bass correctly with most "audiophile approved" type speakers, this is only a very small percentage of the big picture. None the less, i put my money where my mouth is and have 1000+ wpc driving my dual subs in my main system, 1200 wpc driving my HT mains with 1600 watts driving just the subs in that system, a dedicated amp rated at 100 wpc driving the subs in my bedroom system, 800 wpc driving the speakers in my office system, etc...

As you mentioned, dynamic compression, rise and fall times, ringing, phase shift, frequency response linearity, loading characteristics ( Z aka "impedance" at resonance, etc... are all other important factors. Given that vented designs typically have poorer rise and fall times with increased ringing, and vents introduce multiple phase shifts rather then the one that sealed designs offer, and typically have peaks at resonance whereas low Q sealed and stuffed designs don't, and vented designs typically have a higher impedance, which translates into less amplifier control and ability to load power than a low Q sealed design does, etc... Obviously, you can see where i'm going with this without me continuing any further.

As to your question about "playing with the damping of vent", this can be done. This is much the approach of a stuffed Transmission line and a Vario-Vent or "Aperiodic" design. Both offer many of the benefits found in sealed designs and may even surpass sealed designs in some areas. These are both somewhat "tricky" to design though. Some of the old Dynaco speakers were "Vario-Vents" and produced very good bass output AND definition for their size. That is, so long as you kept the spl range within reason.

As far as the JMLab's speakers go, i thought that the they sounded "barrel-chested". I think that much of this could be solved by adding damping material into the cabinet. The reason that it sounds like a "barrel" is that you literally have a large open wooden chamber resonating away. By adding damping material, you reduce both the excitation of the cabinet itself and absorb some of the energy that would otherwise be bouncing around in the cabinet causing a "bass echo" or "ringing".

In terms of "tighter bass" sounding "lean", that is a common thought. That's why i've stated that people are just TOO used to "bass slop". When they hear what tightly controlled bass with minimal overshoot and ringing sounds like, the articulation and definition is readily apparent but they still can't get used to NOT hearing all of the overhang. Most equate "bass slop" with "bass weight", which isn't quite the same thing.

As to your specific questions, here goes:

1) As to your comment about Musical Fidelity gear, most that i've heard sounds noticeably lean. Haven't heard all of their models though, so can't answer that specific part of the equation.

As far as i'm concerned, you shoot for speed and neutrality throughout the entire system. If you try to go with any other approach, you're back to "complimentary colourations".

2) Properly designed speakers are designed to work with specific room boundary effects taken into account. If a manufacturer doesn't provide basic suggestions as to where the speakers should be placed, chances are, the speakers are going to sound VERY different from room to room. Since obtaining neutral response in a consistent manner should be the goal of most "audiophiles", speaker design and placement become key factors in what we hear and total system performance.

Other than that, most designs already suffer from bloated bass as it is. Adding further low frequency reinforcement by placing the speakers closer to a corner, rear wall or both, etc.. will only make the presentation sound thicker and slower. With that in mind, some high-tech speakers with a lot of research put into them are designed to be placed up against the wall. If you pull them out from the wall, you'll have too lean of a presentation.

3) It is not so much the roll-off that makes a speaker hard to set-up, it the "Q" of the peak at resonance. Q covers both the amplitude and bandwidth at resonance. Speakers with a lower peak at resonance will be easier to place because the bass sounds less "one notey". Speakers with a narrower bandwidth peak will also be easier to place because they have less chance of exciting the various multiple nodes spread over a wider frequency range that exist in every room.

What the shallower roll-off of a sealed design offers is greater usable output below resonance. Once a vent is done, it drops like a rock. Anything below the point of resonance on a vented system unloads ( minimizes damping ) on both the vent and the driver. Excursion of the driver increases and the bass becomes quite muddied due to the uncontrolled extension. Better vented designs, like that of the Merlin's, use some type of high pass filtering to minimize these problems.

As far as Thiel's go, the placement problems with them may be two-fold. First of all, they use passive radiators. Passive's are slower than ports in terms of transient response. Slower response sounds muddier, making it harder to find a position in the room where the "mud" is reduced AND nodes aren't excited. Couple this with treble response that may require slightly different speaker positioning to work optimally and you've got yourself a lot of work ahead of you finding a good compromise between the two.

This is why i said that properly designed speakers will take into account room reinforcement. The designer should be able to give you an idea of where the speaker will work best in your room. While every room is a little different and may require some trial and error, those suggestions should get you pretty much in the ballpark. After all, they are familiar with the bass peaks, roll-off rate and can factor in room reinforcement from there. On top of that, they should have taken into account these factors when designing the rest of the speaker too, so the mid / treble radiation pattern should be designed to compliment optimum bass reproduction.

As i've mentioned before, very few speakers take all of this into account. If they did, you would be seeing a lot more "oddly" shaped speakers with acoustic treatment on the baffles. Reducing diffraction of the baffle itself is one thing, but taking into account room interaction with that baffle is one step ahead of most designs. Sean
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So the conclusion to this post is that most people haven't been educated to the sound of high-end audio? The uneducated listener will look for big bass and how loud it plays? Probably true.
I may be a more educated listener now than 3 years ago when I got myself into this mess but I still miss the lack of bass, especially on drums.
Correct my mistakes here but I see bass as more than just frequency response. That is a steady state condition. In music apparent bass has attack, sustain, and decay.
I have not heard better bass than what an active speaker can do. My thought is the lack of **dynamic compression**. I think most amps clip and you aren't getting all the bass that is coming from the source in a passive speaker. A well-designed active amp/driver combination doesn't compress dynamically. So you get the sock-in the chest whump. This is not a steady state condition and is vital to perceived bass.
A slow decay can mask detail and make bass sound bloated. Can't a vented design use an overdamped design which will give the bigger bass of a vent while still keeping bass "tight" due to fast decay?
So I conclude that dynamic, uncompressed bass attack that is well damped/ controlled by the amp can give big bass that people desire without being bloated. Also the more air moved = more perceived bass. There is no inherent problem that multiple bass drivers = too much bass and if well designed would give less dynamic compression and be tighter than a single bass driver. Look at line arrays for example.
I heard JM Labs Alto Utopia recently and it had way better bass definition than my Nautilus. I would have sworn it must have been sealed from the way Sean described a seal design but JM Labs says it's vented. So vented designs can sound tight. But the downside was that it sounded very lean - the offset of getting cleaner bass.
Some questions I have:
1) Is it better to go with a sealed box and bass heavy electronics like Musical Fidelity 308?
2) If you put a speaker closer to the wall for more bass, would this make bass muddy the same as a vented design? It seem so to my ears.
3) First order bass rolloff is better than the 4th-order you get from a vented design? In an actual room bass will be boosted 3-6 dB/octave and a first order rolloff could give too much bass. Note how reviewers have a hard time setting up Theils. Fourth-order rolloff is much easier to set up

Some of you may find this discussion by Pat McGinty of Meadowlark interesting.

http://www.meadowlarkaudio.com/TC1.htm#top

Nothing is free. The trade-off with the "free" output is the increased roll-off rate below resonance ( 24 dB's per octave vented vs 12 dB's per octave sealed ), poorer transient response, increased potential for woofer damage when fed a signal below the tuning of the vent, out of band output leaking out of the port, etc...

In many cases, even though a sealed design may have a higher point of resonance than the vented design, the sealed actually has more usable output at a lower frequency. This is due to the shallower roll-off rate. Since the vented design rolls off twice as fast, the resonance of the vented design would have to be exactly half that frequency or lower to achieve the same output level at -12 dB down.

Even with the added "free" output, we've seen how most vented designs actually work in the real world. That is, they are far from "natural" sounding due to the peaks introduced at both the driver and vent resonance AND transient response is typically poorer. Is that "free" output really all that it's cracked up to be? This question becomes even more redundant when we consider how low the dollar per watt ratio of some pretty reasonable sounding amps are today. Sean
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Sean, not with the same total bass output. Vents = free extra bass SPLs, good or bad.

Ernie: Sealed and stuffed is smaller than vented when the vented systems are properly designed. Most vented products aren't designed properly, hence their smaller size / built in trade-off's right off the bat. Sean
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Sean, dude you should join forces with another paranoid audio critic: Artur Salvatore.

Hi Sean. Sealed is smaller? I think you meant compared to TL, of course, since manufacturers use vents specifically because of that free bass from a cheaper, smaller enclosure. And you know, given that the lower 2/3 of a speaker's height is relatively free aesthetic real estate, it's just too easy to fill a tower with woofers compared to selling monitors with stands at the mid-price points.
Your response to me above exhibits so much cynicism, Sean. It's been raining here in Beantown for 4 days. Let's all lighten up, eh? When my audio-naive friends visit and sit in the sweet spot I don't have to train them how to listen.
The music-lovers, especially, relax into deep rapture all by themselves. I think the market malaise is more about that most of the public simply doesn't want to be entertained by simple audio. I have several friends in the pro audio and musical instrument manufacturing biz who simply don't sit and listen to recorded music anymore. Busman's holiday? Hmmm...maybe somewhat, but lots of folks want a visual element. I cleave the two with separate high rez 2ch and HT systems, but most won't, as we all know.

Ernie: I am well aware that there are exceptions to the generalizations that i've made. From what i have seen and heard, they do exist. They just aren't commonly found or available due to going against the grain of the marketing hype that currently exists. Dealers don't want to carry products that don't sell and these products don't sell because the average consumer hasn't been educated or know what to listen for or how to listen for it.

For this, i blame the audio industry and the press. They are responsible for the "trick bag" that the "high end" audio industry has worked itself into. Due to their marketing games and the profit margins generated from under-designed products, the average consumer can't tell the difference from a "salon" speaker to a Best Buy speaker. That's because they all demonstrate severe forms of non-linearity. The only differences that they can tell is if one is louder than the others and if it produces more bass. I also forgot that they know how to look at the price tag, which has them scratching their heads and asking why they should spend THAT much more without getting measurably superior performance.

Duke: Given proper design, a TL will always be larger than a sealed design. To most people, size counts. Regardless of how many advancements have been made in TL design, they are infinitely more difficult to design / build / manufacture than an equivalent sealed design. Since manufacturers and DIYer's are less apt to venture into such waters, i've tried promoting a design concept that is both simple and cost effective to work with and produce while offering excellent sonic performance.

As i've mentioned before, i don't consider the simple sealed box to be the ultimate in design. I do consider it to be the best bang for the buck with the least skill and knowledge required. As Mr Dartford stated, the less potential to screw things up ( i.e. the simpler that you keep them ), the more likely you are to achieve a higher percentage of success.

Once one has achieved a high level of succcess through following sound ( as in "proper" ) design & engineering practices, refining the basic design and striving for the highest levels of performance enters into the world of diminishing returns. The last few percentile of measurable performance tends to cost more than what it would cost to build another system of similar stature.

As such, i would rather see folks get 80% - 90% of the performance out of their systems at a reasonable cost than to see them pay exhorbitant amounts for much reduced performance. The fact that many end up doing the latter rather than the former due to being fooled by advertising and marketing trends makes it harder to recruit civilians and keep this industry strong. It is difficult to justify added ( let alone exhorbitant ) expenses when the ends don't justify the means.

As with any type of system or project, should one choose to seek a higher level of performance than covering the basics with good design principles and proper implimentation, they should bring their wallets and valium with them. It is a steep slope that will have one stepping into uncharted territory. That is, as far as most audiophiles and even most "pro's" are concerned.

As such, getting past the marketing hype and high prices is only a small portion of why i promote sealed designs as heavily as i do. The fact that they have the potential to perform in both a measurably and sonically superior level compared to 95% of the designs out there while taking up less physical space could only be considered a benefit.

Either way, people can buy / build / spend their money on whatever it is they like. As i've said before, there's no sense in catering to someone else's preferences. As i've also said before, those that are interested in achieving optimum results without spending maximum cash need to educate themselves on the subjects. The more that an individual knows, the less likely that someone else ( me included ) is to steer them in the wrong direction. Sean
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Bombaywalla, well said and I appreciate your comments.

tdl,imf,fried,pmc all had it right.

Time has shown the difficulty in designing a good Transmission Line. Also, as the name has a certain magic to it, some have claimed their designs to be TL, when in fact, they are not. I think the problem is that it requires a unique personality to achieve the goal. One with intelligence, creativity, self confidence, and the right balance of objectivism and subjectivism.

The key to building a TL is experimentation, and the ability to do so. A "test mule" must be constructed, which allows access to the inside of the cabinet, in order to try different materials and varying amounts of said material. Two important things to first get right are the line itself and the driver to be used in the line. The driver's Q must be capable of matching the line, as line damping can accommodate some variation, yet only to a point.

In terms of line damping, this can be likened to the style of cooking or sauce one implements. We know we are eating beef - the TL, and that it will fried, then finished in the oven - the driver. However, the implementation of which can vary a lot - that is the damping.

I have found often that lines are overdamped, which phenomenally lessens the amount of bass the speaker will produce and makes me wonder why a TL was the choice in the first place. A TL that makes no bass is not worth the trouble in the first place. Hopefully, the cabinet has the abilty for the designer to get in there and alter the stuffing.

A TL isn't something that one will get right on their first, or even third attempt, and that is probably a reason they haven't achieved more market share. While it can be said that complexity and cost are big factors, and I do agree, we audiophiles have proven we are willing to pay the freight when it comes to expensive gear.

The fact that transmission lines are hard to execute well doesn't mean it can't be done. Indeed, it's being done right now by several manufacturers. And having built more bad transmission lines than you can shake a stick at, even an amateur like myself has learned a few tricks.

I've had fairly low-Q sealed enclosures and transmission lines side-by-side using the same drivers (KEF B-110 woofers, Dynaudio D28 tweeter), and even an amateur-built TL was (in the opinion of classmates who participated in informal blind listening tests) considerably more realistic sounding.

Regarding "pressure relief" enclosures, yes Sean I was talking about vario-vented (and homemade resistive vented) enclosures. I didn't use the term "aperiodic", as that term can also be correctly applied to a Qtc = .5 sealed box, and I didn't want to confuse things.

If excellent power transfer in the bass region (as indicated by a very smooth impedance curve, especially around system resonance) is a high priority, and if the only advantage of the sealed box is extreme ease of design, then why not consider the transmission line, or for that matter its ultra-simple cousin the pressure-relief box? They have much better power transfer - and by implication better linearity - in the bass region than a sealed box does, if indeed the impedance curve is an accurate predictor.

Not trying to be confrontational Sean; just tossing my favorite enclosure into the ring against yours....

Cheers,

Duke

Phew! Lots of reading....
Glad to see that "Q" was discussed. Balancing enclosure size, driver characteristics, vent frequency and sensitivity is certainly an art. Not having heard the 20T, I would nonetheless find it a bit difficult to believe that Mike Kelly would purposely let a bloated high Q speaker out the door at 23k. Likewise I've learned that JA's cut 'n patch fr curves can be a bit misleading...as are most such attempts at describing response in a real environment. My assumption is that the 20T is for LARGE roms, where the big bass plateau can be appropriate. These ARE big speakers in my book....
I think it may be a bit too easy to criticize vented designs. Certainly if the vent frequency is low, and the driver well-controlled with a very low Fs, in an appropriate nonresonant enclosure, excellent results can be had. I understand the nherent problems, yet had moderate success loading a 3-way (8+5+0.75, vent 32-35Hz) a while ago. The problem wasn't so much the bass response, but other issues higher in frequency (matching driver sensitivities with loose OE specs!). Yet the speaker did have characteristic "vent" sound. Maybe we're all too much used to it, and Sean is partly right....
So it was quite a shock to hear how clean and tight the response is from my now-3yr old Verity Ausio Parsifal Encores, for example (8+5+1). Stunningly fast bass response that matches its incomparably-quick midrange. I asked Pelchat et al at VA how they did it, and mentioned that the Encore was predominantly about getting an extremely "fast" woofer custom spec'ed from Dynaudio, for which they pay a fortune. Sounds it...really hard to believe there's a lagging vent huffing and puffing in this design.... I suspect a low Q keeps things quick and flat, too, as I measure fla response to 30Hz in-room, falling precipitously below that, of course, as is typical of a tuned vent. You should listen to this speaker, Sean, before castigating all vented designs further....
Comments about boom-cha favored response (the old West Coast saddle-curve...aka Bose?) I find intriguing, and can't comment upon whether current designers are influenced by unnatural bass level pop music tastes....
Some posters correlate that flat bass frequency response is somewhat correlated with price. certainly this is only slightly true, vis a vis enclosure size cost. It's really not harder to design a $1k speaker with a reasonably flat and "chosen-Q and vent freq" than a $20k one. Thiele/Small, Q, vent geo, etc., are givens, so Aeriel's $23k speaker doesn't have smoother bass than the $6k Legacy for THAT reason. Hell, my Spendor 3/1p ($1400) have a nice smooth bottom. It's just good design....
There's too much to comment on here later....
Cheers. Ern

In my opinion, and with 50 years of experience building speakers (mostly by the old fashoned trial and error method) transmission lines are the best boxes, but as sean says are hard to get right. Sealed boxes are almost idiot-proof, and so, in the real world, in most cases will outperform TLs. Furthermore, because of their gradual and well controlled roll-off, electronic equalization is effective. The key to speaker building is "don't screw it up". It's too easy to do that with a TL.

Re: transmission line speakers, mechanical & electrical modelling is now available for quarter-wavelength speaker design. Never tried it -- but thanks to a few audiophile engineers it looks like we've taken a large step forward from the trial & error situation of yesteryear. D Dlugos' site has general info on the subject and, of course Martin J King who actually developed the computer-based mechanical modelling.
Cheers

Transmission lines have potential but are phenomenally hard to build and fine tune. Given that most manufacturers can't design / build simpler products, i don't hold much faith in them getting a more complex product like a TL right.

As a side note, AudioXpress had some recent articles about a TL design. From what i walked away from that article with, my thoughts about them being very complex / hard to optimize were only reinforced. Tons of higher frequency rippling taking place, etc... along the length of the tunnel. Even more than a poorly designed port. Obviously, one would have to do a lot of experimenting with different types, densities and placement of damping materials to get things dialed in. As such, sealed and stuffed is hard to beat from either a mass production or hand built / tweaker point of view. In many cases, simpler really is better.

As far as "pressure relief" enclosures go, are you talking about Aperiodic's aka "vario-vents"? Sean
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Sean, what are your thoughts on transmission lines? Transmission lines have much smoother impedance curves through the bass region than most other enclosure types. One current commercial design that I'm familiar with uses an "8-ohm" woofer and the impedance peak in the bass region doesn't go over 11 ohms. There may well be others that do even better.

Or what about pressure-relief enclosures? No time-delayed output from the damped opening, and once again a much smoother impedance curve in the bass region.

Seems to me either of these approaches are inherently even less resonant than a sealed box.

Dawgbyte,

With due respect to you & to others on this forum - I do not wish to offend anyone as there is no need to. So, all that I write further is merely for purposes of discussion. I'd like to get that straight first of all.

I think that you might have missed the point in Sean's original post? I personally did not conclude him to be a Mr. Know-it-all. Rather, I found his post to express his extreme/emphatic frustration at the present trends in multi thousand dollar speakers. I found him to exclaim that designers of these multi thousand dollar speakers were NOT keeping in mind the fundamentals of speaker design. Rather they were just blindly feeding the consumer whatever he/she asked for. Now, one could say that "the customer is king" so the manuf. should make whatever the customer likes. True to a point. What if the customer goes hay-wire & makes an inordinate request? An inordiante request would one that degenerates the audio hobby. What is the manuf. to do? 2 things as I see it: (1) be true to the hobby & gently coerce the customer to see his flaw & (2) forget about the inordinate demand and simply consider revenue - to the hell w/ the audio hobby! REMEMBER, we are talking about multi thousand dollar speakers ONLY! Not the ones affordable many of us w/ our reasonable ranges of incomes.
What Sean has expressed is his frustration at seeing the manuf. choosing option (2), which in his mind (& to many others including myself) is not right for the greater well-being of the hobby.
If you look at History, look at Senior management, the President's office, leaders manufacturing, in sevices, etc. What do expect of them? We expect them to be true to their respective causes. We expect them to reformists to some extent where they will preserve the original mission statement.
We expect the same from audio manuf. esp. those of noteable reputation. We expect them to lead the speaker design & manuf. wave-front & to excel it to new heights.
I don't know why you got into this hobby (we never discussed it, I mean) but I got into it to reproduce live music into my listening room as best I could & with the limited budget I had. I know that it is only a dream but a well thought out system can be very convincing! If I am to remain true to this objective, these multi thousand dollar speakers are a totally failure!!! From their measurements, they are very likely to sound anything but real. Yes, measurements are NOT the be-all & end-all of speaker design BUT it is quite correct to say that flawed measured results do produce flawed performance. If one cannot hear it, it's because one's ear needs better training or one's electronics is flawed or one's room is untreated or one has an hidden agenda.
Many of us feel that charging multi thousand dollars for speakers that have very mediocre to bad performance w.r.t. reproducing live music in one's room as best one could is a serious blow to the long-term stability of the audio hobby. We feel let down by manuf. that should have been leaders in this art & science. They have razed the bar rather than raising it.
Would you accept sub-standard NEW products from leaders like Pfizer, Mercedes Benz, Rolls Royce, Rolex, General Electric, SAP or any other leader for which they charged you a PREMIUM price?
If the answer is "no" then WHY are you going to accept a sub-standard product from a speaker manuf that is SUPPOSED to be SOTA??? REMEMBER, we are talking about multi thousand dollar speakers ONLY!
There is a market for speakers that alters the music signal. People buy these speakers. Nothing wrong w/ that at all. If it floats your boat, please buy it.
However, if you are going to charge multi thousand $ for a speaker, call it SOTA & then have it perform mediocre to bad, what do you think you SHOULD get from the customer base??? Accolades? I think NOT! However, this is what we are giving them!
This might be a hobby for you & me but anyone in the business of making audio gear should be judged by business standards & not by hobby standards. It's not a hobby for these manuf. they are in it for real & not casually.
Maybe we don't push the manuf. harder to perform better 'cuz we, the audio hobby group, don't know what music should like in the home environment? Maybe our ears are not trained to register timbral accuracy of instruments & voices? I have made an observation over time that all those audiophiles who attend lots of live concerts of any sort mostly do NOT have any of the commercially know speaker brand names! Can you think why this is? See if you can come to the same conclusion yourself (or if you can refute my emperical conclusion). The speakers they have are either of esoteric brands or are DIY or are from real mom & pop speaker manuf. that seem to still hold the course of accurate, real music reproduction.
Anyway, I've rambled on long enough. Hope that this dissertation was useful to you & that you can see things in another light. I HOPE that you will find less reason to be contentious.
Of course, just my view-point. FWIW.

Newbee, Sean's "cause" is as complex as it is noble. I think in his own mind he believes he is doing us a favor in highlighting the dishonesty posed in speaker marketing advertisements and the lack of integrity found in stereo review magazines.

I share in your same objections and would prefer a more positive discourse designed to understand how and why some speakers are technically and experientially more successful.

I trace the "big bass" problem back over two decades, when pre-amp designers stopped including tone controls on their units.

Now "bass lovers" have to buy a big, fixed tone control, also known as a "big bass" speaker.

Dawgbyte, You refer to Sean's 'cause' therefor I assume you have it pinned down. When I first noted his posts on this issue I thought he would in fact be marketing a speaker in the near future sporting a design which was in some way inovative in solving the tradeoffs between sealed and vented enclosures. Apparently this is not to be (good for him). What I have found objectionable, especially in a forum where the majority of readers are very impressionable, is his categorical denegration, by direct comment or implication, of a speaker design which offers valuable tradeoffs for many audiophiles. I'm sure he feels that he is passing on valuable information - I don't question his motivation, just his tactlessness and style in dealing with this issue. If I shouldn't use a vented speaker because most of them are POS, and he can't recommend a sealed enclosure type which would satisfy me in stock form, then what am I to do? What am I to do? I want to be a member of this club!!!! Help. :-)

Bombaywalla, yesterday I spent over an hour reading through this thread and the thread Sean linked to entitled "Sealed vs Ported" over on AA. Sean provides some valuable technical insights, but IMO his approach leaves me cold and unsympathetic to his cause. I think he takes pleasure in luring speaker designers onto these boards, so he can debate design theories and make unprovoked attacks on their motives and products. His attacks and insults on the Adire Audio designer are a perfect example. Sean is the classic "know-it-all" who would rather sit on the sidelines and criticize others instead of jumping into the game and going into business for himself. I'm sorry, but I'm not a fan of people who like to listen to the sound of their own voice.

I think it's time for Sean to answer some questions I have posed for him in the Dynamic vs Electrostatic thread here on Gon... which I actually meant to post here on this thread, so unfortunately it will appear out of context.