I am wondering, what are the choices as to NEW speakers if one has a preference for sealed (acoustic-suspension) speakers, instead of the rather more usual, bass-reflex type?
the NSR Sonic Research D-3 was the best by far in any sealed enclosure I have ever heard,for a loudspeaker under 4ft tall to play cleanly below the range of any insrument which is a grand piano I believe around 27hz that is saying a lot, Hyperior,von SCH vr4mk2 are muddy in compare, with the patented APL system and this speaker is 93db efficient and disappears in the room. On the east cost you can get a listen at http://hifidelityaudio.com I have mine on order this is the best loudspeaker I have ever heard in the $5k range and I have heard a lot.
You buy the New NSR Sonic Research with their patented APL lens which is a sealed system that refocuses the soundwave for incredible tight Bass that is at least in the mid to low 20hz region cleanly for a speaker under $5k to do that and sound so cohesive on top is a breakthrough IMHO and many others at the shows including reviewers agreed.
One reason I would never get rid of my gorgeous Avalon Ascent MKII's.Sealed 175 lb box,with two outboard 55lb crossovers.Very easy load(6 ohm),and amazing detail retrieval and timbres.Yes,I have added a big REL sub,as I have these speakers 8-9 feet out into room,and can use a drop of low end slam/depth,but the integration is flawless. I truly believe the partnering electronics of the day was not up to this "classic" speakers performance match.Even the A/C power conditions are dramatically revealed with this wonderful design,which sounds a bit like a big Magico Mini.Every bit as revealing as the new(very nice,btw)Avalons,but better midbass,and lower midrange.It's the BIG external crossovers that proved to not have the best WAF,but the speakers(and crossovers,to me,anyway)are absolutely gorgeous in my tropical olivewood. These appear once in a long while on the used market,and are a steal,at the usual asking price.Build quality is in the "heirloom" range. Best!
In conclusion, look for any loudspeaker that uses a sealed box, seemingly stupidly large magnets, and an outboard bass processor. You'll be on the right road...
Agreed. Sealed box active sub woofers with large drivers that have large magnets...sounds like the ticket to me!
The TRW design scares me a bit due to turbulence of the blades creating audible noise above LF frequencies ...but it sure is innovative and that it works at DC I can well believe!
In another thread, the TRW sub concept from Bruce Thigpen of Eminent Technology was supported by a very thorough examination of WHAT IS WRONG with ported subwoofers. Since a full range system must have a woofer that includes much of the range that a subwoofer is supposed to augment, its a useful discussion for stand alone "big" speakers as well. Its a long read, but worth it. While I don't agree 100%, he's got the gist like few other designers I know or have read about.
http://iar-80.com/page142.html
Think of it this way; There is no way that the air in a port can PREDICT that the backwave of the woofer diaphragm needs to push it forward in time with the innitial transient of a low frequency envelope of sound, such a drum whack or bass string pluck. Thus, instead of SUPPORTING this first cycle of sound energy, it CANCELS it from entering the air load outside of the box, storing it in the resonant system that is the 4th order bass reflex, adding the mass/spring system behavior of the driver to that of the Helmholtz resonator of the ported enclosure. The touted efficiency so long expressed by enthusiasts of ported speakers is largely illusory, since THIS EARLY TRANSIENT PORTION is missing at the critical tuning frequency, and below that frequency even sustained sine waves suffer the same fate. Careful examinations of area-under-the-curve during transient events (90% of music) for sealed vs./ ported designs show that gains are far less than the 6dB theoretical advantage. Yes, certain organ-type sounds will seemingly not be harmed by a ported design at first listen, but their PACING will be off, in terms of aligning their tempo with the rest of the voices in a performance.
Since there is no precession function in the port air, and no direct signal to it from the amplifier, it's behavior is only "loosely" based on the original waveform. Interestingly, a sealed box woofer design that has sufficient extension into the lowest octave commonly associated with the "bottom" of human hearing (20Hz - 40Hz; see Thigpen) actually uses a high mass cone and underdamped woofer motor system, for a high Qts of well over 0.4. Otherwise, the ratio under a Qb of 0.707 for a 2nd order Butterworth (B2) alignment is too high, and the resonance requirement of the woofer driver will become ludicrously low, and the Vas will become equivalent to the interior of a city bus. Suspensions this loose tend to have a hard time staying centered or linear. Energy storage of such high mass systems also present a problem. You simultaneously have weak brakes from the driver motor and a big chunk to slow "downhill" into the source- intended decay of the transient.
My solution has been a proprietary analog active circuit (from design work in 1993) that provides minimum phase compensation in front of the power amplifier for earlier than desired roll-off of extremely low Qts drivers sporting massive magnets. Imagine a minimum phase design that uses a single differential gain block and 8-12 passive parts, that can give arbitrary extension below F-3 for any sealed woofer! It's even skimpier than Linkwitz's design... This circuit opens the door to the use of high acceleration capable drivers that are highly overdamped in the eyes of standard T/S models. A specification used by Audax of France, the calculated GAMMA values of some of my subwoofer drivers exceed 1000. I've read carefully the proposition to rate driver acceleration using voice coil CURRENT exclusively, and it holds no water in my estimation. Bl is calculated against earth's gravitational pull at a given input current. The mass of the diaphragm, statically or dynamically loaded (turns out not to matter much due to the partial inclusion or exclusion of the surround/spider and or air load) , gives the other half of "power to weight ratio". When rating a sports car's performance, the 0-60 time is given by the same factors. Worrying about crankshaft torque but ignoring the mass of the car is missing the question. Thus GAMMA is the ratio:
GAMMA = Bl/Mms(or Mmd) For proper scaling, mass is in kg.
Thus a really good sealed design for a SUBWOOFER will begin its 12dB/oct attenuation at 60-120Hz, and the output will occur BELOW SYSTEM RESONANCE. There are high mass designs that go for this, and our brother Bob Carver tried to take some credit, but I and others were using similar practice for decades before. I remember in the mid 80's using a Henry Kloss driver from the mid SEVENTIES, that had a crazy magnet on a long throw 7" woofer, that was originally used in a sealed box with an outboard analog processor.
So why a GAMMA that high? Because the brakes are a secondary function of the back EMF absorption as provided by the output impedance of a power amplifier, coupled with the damping rate of the driver motor. If the damping factor is poor on the amp, or the driver has a wimpy magnet (to get a good F(-3) in a full range box), the GAMMA will be in the 100-200 range, and thus the ACCELERATION PROVIDED TO SHUT THE DRIVER BABBLE UP will be lacking the ability to do so with authority. What you get is a speaker that goes "BONG" after each time it is asked to move, and it bongs at system resonance, and it bongs AUDIBLY and it bongs for a LONG TIME for small magnet drivers. Sure, you can make the bong thing better (higher Bl and lower Qts) with a shorter voice coil, but then you get less excursion, and you're arguing about a midrange speaker being a good subwoofer. Also a shorter coil leads to lower moving mass, thus higher Fs, and you lose the 20-40Hz battle.
In short, no ported speaker can be considered "high fidelity" from a waveform measurement standpoint. For a long time, the step function test was ignored as a measure of system performance because so many designs measured so poorly against it, that it was too glaring a repudiation of the bass reflex approach.
I'm surprised no one mentioned ADS as a candidate for classical speakers that were SEALED. Now, take the 8" or whatever woofer out of an ADS speaker and eyeball it. The magnet on it will be a TINY 12-16oz. The Qts will be very high. And the bass, while better time-wise than a ported design, will still be sickly sounding and unconvincing.
If the silences between notes are filled with the complaining of the speakers trying to play precisely nothing, the dynamics of 24bit recordings will be reduced, just as surely as by a high signal noise floor. There is hugely important timber information at low levels following large signal transients, and if these aural clues are buried under the struggle to regain composure of a typical sealed box design, significant enjoyment is lost.
In conclusion, look for any loudspeaker that uses a sealed box, seemingly stupidly large magnets, and an outboard bass processor. You'll be on the right road...
The new NHT Classic Three that graces the cover of the latest TAS looks to be a very interesting sealed speaker. Instead of the standard two way monitor, it's a three way plus very attractive sculpted styling. It's refreshing to see a stand mount speaker than is different than the standard square box and not ported either. The price is also right at 800.00 pair.
Another manufacturer that uses sealed designs is Snell. The Series 7 C7 looks most interesting to me.
I too use Hales speakers, Concept Twos. Play them full range on high powered tubes and use a good sub for the last octave and with the right cabling they are very impressive.
Many ported designs I've listened to never made it past an initial audition. A few that did I've tried at home. The results were very one sided in favor of the Hales. I would like greater effeciency to play louder cleanly and a nicer looking speaker. I even tried Avalons Avatars. (also sealed) They were nice, even and tight, very focused. The Hales were close, maybe not as refined, but clearly more open and "organic"? (real) sounding. They also image like crazy. and are more spacious sounding.
It's oversimplifying the issue. Sealed spkrs will have a higher F3 than the, otherwise identical, ported design but fall off there after with a shallower slope. POrted drops faster.
There are many other considerationa, one of which is that ported design used to be notoriously badly designed. THis is no longer true -- or at least, it doesn't have to be true. You can compute the port parametres (for those designers who are too lazy to do the math -- or can't, which is more often the case).
I have a pair of Hales Revelation III speakers which I love because of the incredibly tight bass they produce. The speaks are sealed. My Watt Puppy's on the other hand are ported and, although they reproduce bass at a reported 20hz, don't have bass that hits you in the chest like the Hales do.
Is it correct to assume then that this is the chief difference between the two enclosure designs, or is this oversimplifying the issue?
Yes this is the main difference when the port is used to extend bass response, as in the majority of designs. In these cases, a ported design will generally have a poorer transient response but will have more energy at lower frequencies (although the roll off will be sharper and there will be more distortion in the LF).
A sealed box is always better in transient reponse
Just wondering what it is that you like so much about sealed cabinet designs. I have a pair of Hales Revelation III speakers which I love because of the incredibly tight bass they produce. The speaks are sealed. My Watt Puppy's on the other hand are ported and, although they reproduce bass at a reported 20hz, don't have bass that hits you in the chest like the Hales do.
Is it correct to assume then that this is the chief difference between the two enclosure designs, or is this oversimplifying the issue?
The Avalon Monitors are *not* sealed. They have a vertical port directed downwards just behind the speaker terminals. They are gorgeous speakers though, with the classic Avalon sound, comparable to the Avatars, just a little less body into the lower end ...
You are definitely on the "right path" imo. Magico Mini should be on top of your list. In fact, all Magico speakers are sealed designs. Once you hear properly executed acoustic suspension designs, there's no going back to the ported ones.
its easier to find used fullrange acoustic suspension models, but there are still some out there. some to consider which are currently in production are shahinian, duntech and fj......older models such as hales, ar, and dunlavy are out there. its pretty hard to go wrong with these brands. the comeback of allson acoustics was shortlived, and they are hard to find. good luck...they are worth seeking out.
Some of NHT's speakers are bass reflex such as the 2.5i's, the model 4's and some of their subs for example. Their big 3.3's and 2.9's were some of the better designs they created. Vandersteen speakers are sealed designs except for the 1C which is a transmission line design. The 2Ce Sigs, 3A Sigs, Quatro's and 5A's are sealed designs with some interesting twists. Most speakers now are ported but they're other sealed designs around. The Spendor suggestion is a good one.
Most, if not all, NHT speakers are acoustic suspension.
Although NHT might not have as blue blood a high end pedigree as the speakers Seantaylor99 mentioned, they do have some claim to lineage from the Golden Age in the U.S. -- one of NHT's founder's, Ken Kantor, used to head R&D at Acoustic Research, the birthplace of the acoustic suspension design. (Granted, he was there about thirty years after AR first developed the design.)
I think NHTs do some things quite well and are reasonable values. Worth checking out.
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