Pros and Cons of built-in amps?


I would be interested in any experiences and opinions on speakers with built-in amps. There are some from well regarded companies like ATC and Genesis.
It would seem to me that running the source through a quality balanced cable directly to the speaker would be the way to go if possible. Thanks.
ranwal67
It would seem to me that running the source through a quality balanced cable directly to the speaker would be the way to go if possible.

Yes it is the way to go if you want professional quality fidelity and low distortion. If you prefer a more forgiving or nice sound then you may find it too much of a straight jacket to live with. Each recording sounds completely different (more different then you will have been used to ever hearing)...so you lose some of the flexibility to tailor the sound. Room modes can become more problematic because of low distortion => basically any issues become more noticeable....so it is not without frustrations, bad recordings and distortion that makes it way on to a recording will more easily grab your attention - this can actually spoil some of what may have been long time car stereo favorite tracks...

Pros
Much Lower IMD (each amp drives a separate narrower band and basically has an easy life compared to a regular amp driving a difficult speaker load)
Greater Dynamics/SPL (no lossy crossover, amp tuned to load)
Phase compensated => good impulse response = good on drums/percussion
Less background noise hiss if you use balanced XLR cables and source gear
ATC's use Class A amps up to two-thirds power
Much less chance to ever blow up the speaker drivers(momentary gain reduction is possible in each amp which is specifically designed for each driver)
Low cost - overall since it is easier to design amps that drive an easy load over a narrow bandwidth then you not only get better amplification but it can cost less too.
No need to worry about speaker cables or run lengths

Cons
Nead an AC plug for each speaker
Speakers are even heavier - shipping for resale can be a problem!
Repairs may be more costly if you have to send speakers back to get amp packs refurbished/recapped/calibrated (usually every 15 years or so)
Resale to audiophiles is limited so you may not want to get the "Anniversary" editions with stunning veneers but a black ash box or a pro model instead (active is only popular in pro markets and pros care very little for ultra expensive veneers...)
Troubleshooting - obviously integrated packages are harder to nail down to the root cause.

Listen to this lecture(bear in mind Meridian sell Active Speakers - so take everything said with a grain of salt)
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Do yourself a big favor and find a PMC dealer. Then listen to a pair of properly broken in AML-1's with music with which you are familiar. I replaced Avalon Eidolons with these and, as fine as the Eidolons are, I would never consider anything other than transmission line bass with active dedicated electronics and no speaker cables.
Yes these PMC's should be on your audition list - I would add the Genelec 8050A's too - a real bargain when you consider what you are getting for around $4500 new - I am impressed with their bass response - so much so that I could not believe that these small speakers were actually ported! Overall a very nice balanced articulate presentation (you can easily hear every detail in the recording but it is not torn apart as some studio gear is known to do). They also image like there is no tomorrow. The metal dome is not to my taste but many people love the clean crisp sound!
Try ATC 19s or 20s--really great speakers for the money--slay all the competitors in their price range. Like all British products, you will be hampered by the low dollar to Euro.
The PMC website is www.pmc-speakers.com. Meanwhile, try to pick up Hi-Fi+ Issue #30. The have several articles on active loudspeakers including separate reviews of the PMC AML 1's and the ATC Active 20. Then there is a separate article comparing the merits and shortcomings of both. This issue is indispensible if this is where your interest is. I hope this helps everyone.
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Ussarn,

Have you managed to compare the AML-1 active to the TB2S-A? I have noticed a few comments by AML-1 users and those who have heard these speakers and the larger active ones. According to them, once we listen to active speakers, it will be extremely difficult to go back to any passive speakers. Reasons cited were greater dynamics and more resolution. Maybe the removal of the passive crossover in passive speakers have got something to do with the sound improvement.
Ryder, I never compared the AML-1's to any other PMC speaker. I would like to add two reviews if any of you are interested in the PMC AML-1's. The 6 Moons website did a very detailed review with a complete description of the construction and circuitry. It is in their archives and was posted in August, 2005. The other is in Audio Ideas Guide, a quarterly Canadian publication. They have a website and an archive section. The speaker was reviewed in Fall, 2001 and it has measurements. These reviews together should answer many questions. Check out Audio Circle under "Bryston" for even more information. There was a thread running there for these speakers with some pictures as well, it is about 4 or 5 pages in.
Thanks for the tip Usarrn. Actually, I have toyed around the idea of transforming my PMC LB1 Signatures into active speakers a while back as one of the forummers in Audiocircle suggested that it might work by removing the passive crossover in the speakers and getting the Bryston 10B into the mix. The use of ETF software and balanced mic are needed to measure post installation. I figured out this move is not viable as a pro is needed to perform this task. Furthermore, James Tanner of Bryston has advised against this move due to careful considerations that need to be taken into account in taking a passive design and turning it into an active system. Hence, I have scrapped the whole idea.

Since you have replaced the formidable full-range Avalon Eidolon's ($20,000 retail) with these small little actives, that shows a lot. Just out of curiousity, are you using any subwoofer with the AML-1's?
Hi Ryder: No subwoofer, not necessary. I am hearing all i need to without complicating the system. Frankly, the bass is equivalent in depth to the Eidolon's, minus about 2db. I have a dedicated listening room conducive to lower frequencies. Perfect bass integration with dissimilar cabinets and drivers can be quite illusive! I must note I listen primarily to Classical & Jazz.
Hello again Ryder! I should qualify the previous post. I measure to 30 Hz in my room at about 2 db down. The Eidolons ($25,000 with the Walnut Burl upgrade) measured 1 db down and 3 db down at 28 Hz in the same room. Now, you know the size of the AML-1's. They use a flat piston instead of a cone for the low frequencies. The motor assembly is about the size of the piston. This is feeding into a 5 1/2 foot transmission line from the rear of the piston. You cannot visually detect the piston moving at loud listening levels! The Eidolons weighed 150 lbs, were a 3 way with an 11" woofer and a vertical port with a very complex passive crossover network and a costly cabinet. I think the AML-1's are now about $10,000 due to the falling dollar. In this context however, they are still a bargain considering you get the amplifiers, electronic crossovers, equalizers and do not need to pay for the glorified fixed frequency tone controls called speaker cable. Plus, I feel the overall performance is improved. As a bonus, my friends need not fear a hernia whenever I decide to re-arrange the listening room where I now have more square footage left over!
Hi Usarrn, I concur in that the AML-1's can be considered as a bargain for their price in that we are getting so many things in one box and still able to save money on exotic speaker cables. This can be said for other good active speakers such as ATC. The only thing that amazes me is the 6.5" flat piston woofer constructed from carbon fibre/Nomex honeycomb that enables large linear excursions down to 33Hz from those rather small boxes. And I'm surprised you managed to get 30Hz-2db! James Tanner had previously measured the response of two units of his TLE1 subwoofer in his room and he also got about 30Hz. Considering each TLE1's have dual 6.5" woofers, I think there is something special going on in that flat piston woofer of the AML-1.

Anyhow, there is the SB100 subwoofer to match the AML-1 for surround monitoring. I am using the TLE1 subwoofer for my LB1's with great effect. It's good to note that you are getting excellent bass response from the AML-1 without the employment of a subwoofer.
You know, you can get all the benefits and none of the downsides of active speakers in other ways - either an active crossover or no crossover.

The big problem with active speakers is that any one that has decent bass response is going to be shaking the crap out of its amps. That is, you know, real bad for sonics.
To Paul: What about soundwaves traveling through air or floor hitting the tubes in free standing amplifiers? I do not detect any evidence of "shaking" electronics, Doppler distortion or distortion of any kind in the PMC AML-1's. I would assume any design requires proper implementation to succeed. Audiophiles just will not give an active speaker system a chance. Could it be that it is not about the music, as they are fond of saying, but the new equipment of the month that they are so passionate about? Find a PMC dealer. Listen to a properly broken in pair. Then fairly criticize if you can.
Usarrn,

The thing is those vibration sources can be and typically are taken care of. That's why we spend money on good racks and isolation platforms.

You certainly are not going to "detect" obvious things like doppler distortion or obvious effects of vibration, but they are going to be there, as anybody who's ever experimented with vibration control will tell you. It tends to affect about everything.

Inside the speaker itself is going to be the worst source of vibration. Even moving the crossover outside of the speaker pays dividends, which is why some manufacturers do it, and now we're just talking about a few caps and coils.

There's nothing at all wrong with active speakers, but the point is they come with trade-offs, like most things in audio. They're not, IMO, a stroke of genius and not the wave of the future. All of this also assumes that you buy into the mantra that digital amps are "just fine" and amplifiers don't really having any bearing on sound quality.

If you happen to be into open baffles, it's not so easy to make them active anyway. :) Well, there's duck tape...
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the obvious disadvatage is removing freedom of choice. i don't a manufacturer dictating what amp i should use.
it is a foolish marketing strategy.
Audiophiles just will not give an active speaker system a chance. Could it be that it is not about the music, as they are fond of saying, but the new equipment of the month that they are so passionate about?

I think there are certainly audiophiles that are guilty of exactly what you describe, but there are also plenty of us that are purely after the best sonic results possible- no matter how they are achieved.

The simple fact is that the best speakers and amplifiers to date have not been active. This has come up several times in various threads and the answer is still the same. On paper, active systems seem to have many advantages, but in practice and in the real world, they have failed to live up to those claims.

Don't get me wrong, they can be quite good as has been demonstrated by some of the Meridian active speaker systems, but few would argue that the Meridian cannot be beat by many combinations of separate amps and passive loudspeakers.

Much of this is common sense. The designers that have the most talent and expertise in loudspeaker design are not as good at designing electronics and visa versa. Perhaps more importantly, if you believe that the best amplifiers on earth are all vacuum tube designs (as I and many others do) then active speakers with their built-in solid state amps are at a huge disadvantage from the start.

In practice, active crossovers have also not been able to achieve the transparency of the highest quality passive crossovers using today's best film capacitors and air core inductors. Those who don't accept the superiority of vacuum tubes are probably not going to "get" this one either, but it happens to be true.

Active speakers, especially with good DSP, are going to bring very good (not the best) sound to many people at more affordable prices in the coming years. These speakers will be easier to set up and less finicky about room issues for people who aren't obsessed audiophiles looking to extract every last molecule of sound quality. Professional studios already reap these benefits and in exchange give up the ultimate sound quality for something that is good enough and revealing enough to get the job done.

Whether active speakers can ever rise to challenge the state of the art remains to be seen. Perhaps someday.
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Mr Tennis: When you are about to purchase a loudspeaker do you try every amplifier in the market to test its compatability with it? Or, when you buy an amplifier do you do the same with every loudspeaker manufactured? If not, how do you know you are making the best use of your monetary resources? Maybe there is still a better amp or speaker out there you haven't tried and would sound even better in your system than the component you settled on. I assume the designer of the active system is a degreed and experienced engineer who wants to maximize the potential of his design and has taken the strengths and deficiencies of both the electronics and drivers he has chosen into account before that system is put on the market. Your freedom of choice is limited by geography, cost and experience.
Dave thinks vacuum tubes make the best amplifier designs. Two of the greatest enemies of the longevity of electronics are heat and dust. What do we have with tube circuitry we do not have with solid state designs: heat, dust, microphonics, phase shifts from the output transformers, weight, degradation of the tubes which will continue to deteriorate everytime they are powered never sounding the same way twice, tubes acting as RF antennas, tube replacement cost, bias adjustments, a rise of ambient heat in the room, poor damping factor because of those same transformers, limited high frequency response, questionable resale value due to a very limited market, among other things. Yes, it is too bad tube circuitry cannot be incorporated into an active design! I guess active designs must be inferior and poor value. I wish my computer had tubes. I have an empty room i could use to contain it.
For Bob Reynolds: I like the way you think. I am intolerant of those who condemn an entire design on belief and prejudice exclusively and not on research and experience. Ultimately, sound appeals to taste but many circuitry implementations are nothing more than glorified and expensive tone controls. Worship often excludes truth, accuracy and adherence to an objective standard.
03-23-08: Bob_reynolds
I'm always impressed with the way Dave presents his opinions as absolute truths.

Readers can look at our comments and decide for themselves. It's also not just my opinion. While there can never be consensus about what the best loudspeakers are, there is some general agreement by magazine reviewers and experienced audiophiles about the companies who make gear that often gets put in the top tier and none of the active studio speakers that you and shadorn constantly praise are regulars on those lists. Of course you are free to pose your theory about the meaninglessness of subjective reviews (professional or consumer) and I am free to disagree with you.

How is one speaker "better" than another? How is one "best"? Without defining the metrics, the terms have no meaning. If measured frequency response is the test and "flatness" is the metric, then better and best have meaning within that context. Likewise, if Dave's perception of good sound is the metric, then better and best have meaning within that context.

I'm sorry that you don't believe in the concept of something being better sounding or more musical than something else. Your obsession with measurements and total disinterest in discussing actual listening is puzzling to say the least. If that leaves you regurgitating specs and measurements in response to various questions, I don't see what value that brings to the table.

High end audio and forums like this one are entirely based on the idea of people exchanging their subjective opinions on gear and how well they believe each piece of equipment serves the music. Is there room for measurements too? Sure, but in your case it's the only thing you seem to be able to refer to. Remember, the whole purpose of this equipment is to bring you (the listener) closer to the intended emotional effect of the music. This makes discussions of how well the gear succeeds at that goal inextricably tied to listening and sujectivity- much like discussions about the music itself. I get the feeling that you would want to discuss Coltrane by pointing to charts and graphs.

If you disagree with my assertion that Meridian makes the best examples of active loudspeakers you are of course welcome to disagree. I would be curious to hear what you think sounds better. Have you spent much time listening to the Meridians?

How about my belief that the very best amplifiers are vacuum tube amps? I'm sure you and others disagree with that assertion also, but if you do, please tell us that you have actually had some real listening experience with the best tube amplifiers from ARC, VTL, CJ, Atma-sphere, etc... To often, I find that people on the other side of this agrument have not.

Everyone on Audiogon expresses their opinions about the sound of gear, and it's not necessary to preface each comment with "IMO" when we all know that nearly everything here is just that.
Professional studios already reap these benefits and in exchange give up the ultimate sound quality for something that is good enough and revealing enough to get the job done. Whether active speakers can ever rise to challenge the state of the art remains to be seen. Perhaps someday.

and

Those who don't accept the superiority of vacuum tubes are probably not going to "get" this one either, but it happens to be true.

and

On paper, active systems seem to have many advantages, but in practice and in the real world, they have failed to live up to those claims.

What Dave says is actually true of many small home studios and local smalltown outfits for TV and radio and making CD's for local talent. Like Hi-Fi - studios are tiered - for many "good enough" is indeed enough and many do everything as absolutely cheaply as they can.

However the idea that the Best or most Prestigious Studios in the World with extremely wealthy clients would use something "just good enough to get the job done" is surely laughable...many of these places have millions invested in just microphones (and they use plenty of tubes too)! They try to attract extremely wealthy clients (who are hard to impress) and suprise surprise quite a few of them use custom designed studios with main monitors that are active. George Massenburg, a legendary designer of equipment, uses actives for near-field and for far-field. Here is a pic of the studio he designed in Nashville Studio C. Do you think he cut corners on the sound - so that it was "just good enough"?
However the idea that the Best or most Prestigious Studios in the World with extremely wealthy clients would use something "just good enough to get the job done" is surely laughable...many of these places have millions invested in just microphones (and they use plenty of tubes too)! They try to attract extremely wealthy clients (who are hard to impress) and suprise surprise quite a few of them use custom designed studios with main monitors that are active. George Massenburg, a legendary designer of equipment, uses actives for near-field and for far-field. Here is a pic of the studio he designed in Nashville Studio C. Do you think he cut corners on the sound - so that it was "just good enough"?

To further add to the above, these are just a few prestigious recording studios and monitoring suites that use active speakers :-

BBC Maida Vales, UK uses PMC BB5XBD Active

BBC London, UK uses PMC MB2S-Active

BBC Radio Theatre, London, UK uses PMC MB2-Active

Asphodel Studios, San Francisco uses PMC MB2-XBD Active

Archer Records, Memphis uses IB2S-A Active

James Newton Howard Studio, LA California uses PMC Active

SoundMasters International, London uses PMC BB5 XBD Active

I do agree with Shadorne in that some of these studios may not have invested in a huge sum of money in equipment and active speakers just to "get the job done". These studios need to provide mastering services to companies looking for the highest quality mastering at a modest budget.
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Shadorne said:

However the idea that the Best or most Prestigious Studios in the World with extremely wealthy clients would use something "just good enough to get the job done" is surely laughable.

You misquoted me and completely misunderstood my point. Their use of what I consider to be less than the very best is not at all due to financial considerations. It is instead a combination of efficiency/practicality and an "measurements are everything" point of view that disbelieves all of the things that are necessary to achieve the very best results. Examples of things that these studios don't or won't consider are vacuum tube amplifiers and exotic audio cables. They are also often hindered by a misguided belief in the superiority of digital and DSP.

I would hope that there are a few exceptions to this in the studio world where vacuum tube amplifiers and superior cables are used for the main monitoring system. I have also seen pictures of the Massenberg studio in Nashville and the room is incredible. That, however, doesn't mean that their use of active studio monitors is as good as what could be achieved by separate vacuum tube amplifiers and passive loudspeakers. Again, it has nothing to do with cutting corners or saving money.
Dave, it should be clear by now, that I have no disagreement with any of your subjective opinions whether it concerns Meridian active speakers or vacuum tube amps. Your subjective opinions (or anyone else's) simply don't matter to me so on what is there to disagree.

I do disagree with you (or anyone else) making statements as absolute truths without providing evidence. If you can't provide evidence, then an IMO preface seems warranted.

Well that's where we disagree. Again, according to your view, the vast majority of posts on this site shouldn't exist. Furthermore, all subjective review publications which review audio, music, cars, wine, etc... are totally pointless.

I find subjective comments useful even when I disagree with them. One of the reviewers in the Penguin Jazz guide has polar opposite taste from mine, and reading his review of a particular jazz record tells me nearly as much as does a reviewer I agree with. I always recommend that people read a review or opinion but rely on their own ears, eyes, or palate to make a decision.

Judging by the number of emails I get daily asking me to describe the sonic differences between products X and Y, it seems many don't share your point of view on this matter.
hi usarm:

i am looking for a speaker at the moment.

if i listen to a speaker and don't like what i hear, i would want to to audition it with another amplifier.

since i have a specific preference for sound, most amplifiers won't be satisfactory. there are only about 3 or 4 speakers in production today that i would want to earn.

your conditions do nopt apply to me, since my taste is so narrow.

i find it interestiung that there are no full range active panel speakers. there are some hybrids which have a dedicated amp for the bass, which is usually a cone.

the point is, a speaker designer is not a mind reader. he can't select an amp and assume that everyone will like the combination of speaker and an amp chosen by the speaker designer.
Examples of things that these studios don't or won't consider are vacuum tube amplifiers and exotic audio cables. They are also often hindered by a misguided belief in the superiority of digital and DSP.

Well it is a shame that these professionals are so hindered by their misguided beliefs. Pink Floyd use David Gilmour's studio "Astoria"....it has plenty of tubes and several miles of Van den hul (audiophile) cables as well as Shunyata. They even have different wiring to the woofers and mid range on their active speakers. So at the high end the lines do blur IMHO...both audiophiles and prestigious studios are seeking perfection in sound. Pink Floyd's sound engineer James Guthrie also uses active speakers along with EMMLABS gear (no tubes in the playback chain - but plenty of tubes in his studio of course).

So while we agree it is not about saving money as Pink Floyd have plenty of money... but I am not sure I would agree that Pink Floyd are hindered by misguided beliefs about active speakers driven by solid state power amps... David Gilmour Studio
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Judging by the number of emails I get daily asking me to describe the sonic differences between products X and Y

Not wanting to get involved in the bantering here, I find this statement to be pretty dubious although it may be exaggerated. I get an average of 2 emails a year(not daily) and it's getting pretty quiet lately. I guess Paul must be quite a knowledgable and renowned audio enthusiast having such good reception!~

Well, at the end of the day it doesn't matter whether state of the art passive-based systems will be better than active systems or vice versa. The most important is as long as any particular system brings enjoyment to the listener that truly matters. Furthermore, it is to my opinion that there is no rule of thumb to create a supposition in that the best systems today are passive speakers driven by tube amplification although all matters related to audio are entirely governed by subjectivity.

Let's not get too carried away with some responses here fuelled by contradictory ideas and opinions.
This discussion should be helpful and fun rather than descend into a heated debate between the members of The Flat Earth Society and National Geographic!
Pink Floyd use David Gilmour's studio "Astoria"....it has plenty of tubes and several miles of Van den hul (audiophile) cables as well as Shunyata. They even have different wiring to the woofers and mid range on their active speakers.

Great, so I guess Shadorne, David Gilmore and I all agree in the superiority of tubes and the value in exotic high end cables!

I'm glad Mr. Gilmore has learned enough about high end audio to have gotten that far. I doubt however that he is an expert in this area like he is in making music and playing guitar.
03-24-08: Bob_reynolds
Dave, do you work as an audio dealer or salesman or reviewer?

As I have stated in dozens of posts, I am an audio dealer. I am also an enthusiast and music lover just like many other people on this form.

03-25-08: Ryder
Not wanting to get involved in the bantering here, I find this statement to be pretty dubious although it may be exaggerated. I get an average of 2 emails a year(not daily) and it's getting pretty quiet lately. I guess Paul must be quite a knowledgable and renowned audio enthusiast having such good reception!~

There seem to be a few dealer haters here and people who make stupid statements like the one Ryder makes above. "Dubious"? How would you have any idea how many emails I get from Agon members on a daily basis? And what does your level of email traffic have to do with mine? And who in the hell is Paul?

Many of my responses here have been to questions about ARC gear, an area in which I have a lot of experience. So I do constantly get emails from Agon members asking about sonic differences, equipment matches, etc...
Here's the problem Bob. On another current thread you respond to a question where the OP asks about tubes vs. transistors. Your response:

03-24-08: Bob_reynolds
I also could not get around the tubes being noisy on some days and quiet on others. I didn't notice any sonic differences, so I chose solid state for convenience.

You couldn't hear or haven't ever heard "any sonic differences" between tubes and transistors?!?! You either have virtually no listening experience with the gear in question, or there is something very wrong with your hearing.

So why are you involved in a discussion with me about whether vacuum tube amplifiers and passive loudspeakers SOUND better than active speakers with built-in solid state amps? You don't have any experience to base a position on.

To a certain extent these comments apply to Shadorne, who in various threads has also indicated a serious lack of exposure to high end listening- especially of vacuum tube amplifiers, cables, analog vinyl, high end digital playback and I'm sure plenty more. Bob and Shadorne are not experienced listeners and I have made a point of chiming in and contradicting their incorrect and experience-less positions when possible.

In other threads, where the topic is of interest to other people like me who actually listen and have lots of experience with all of the gear in question, they have been quieted pretty quickly. But in threads like this one that appeal to them (b/c they both believe in active speakers) where others don't bother to read, they give out at limited if not flat out false advice.

Sorry, but someone has to present the other side.
There seem to be a few dealer haters here and people who make stupid statements like the one Ryder makes above. "Dubious"? How would you have any idea how many emails I get from Agon members on a daily basis? And what does your level of email traffic have to do with mine? And who in the hell is Paul?

To put things straight, I mistook you as "Paulfolbrecht" Davemitchell. And Dave, I didn't have the impression that you were an audio dealer all the while, so my assumption of the emails you are getting on daily basis. Also, please note that I am not a "dealer hater" as suggested in your post, and I have bought from quite a number of dealers here, although not from you. I did not expect your rather crude remarks, more so coming off from a dealer like yourself.
To put things straight, I mistook you as "Paulfolbrecht" Davemitchell. And Dave, I didn't have the impression that you were an audio dealer all the while, so my assumption of the emails you are getting on daily basis. Also, please note that I am not a "dealer hater" as suggested in your post, and I have bought from quite a number of dealers here, although not from you. I did not expect your rather crude remarks, more so coming off from a dealer like yourself.

I would have nothing but kind words for you Ryder had you not stated that something I said was "dubious" or "exagerated". So let's be fair about who made any crude remarks.
I'm glad Mr. Gilmore has learned enough about high end audio to have gotten that far. I doubt however that he is an expert in this area like he is in making music and playing guitar.

Well I'm glad that you treat me, Bob, Ryder and David Gilmour of Pink Floyd fame and many other audio professionals in the same condescending way (people hindered by misguided beliefs or simply inexperienced).

Perhaps David Gilmour and his guitar tech (who built most of the Astoria studio setup using reputed acoustic engineers and contractors) can one day hope to reach your wisdom - as for me, I fear there is no hope and I shall remain an amateur at these audio things.

FYI: I am glad that you are pleased there are tubes in the Astoria studio. These are all in a separate room - away from the direct sound of the monitors because, as even the inexperienced know, tubes are microphonic, which is a form of distortion.
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Anybody who does not hear diffrences between a SET amp (any one) and any class A or AB solid-state amp is either:

1) Listening to a very unresolving system.

2) Using the SET on inappropriate speakers (in which case it should still sound different, but bad).

3) Listening to very poorly recorded music.

4) Not listening carefully.

5) Does indeed have poor hearing or at least is poorly acquainted with the sound of live, unamplified acoustic music/vocals.

6) More than one of the above.

I will go far enough as to say this is a statement of fact. It certainly isn't intended to be inflammatory or personally degrading to anyone.

I would also say that the quality of the SET here is not too paramount as the poor quality ones will have problems - like rolled-off extremes or noise - that should still be *audible*, and will still have much or most of the characteristic single-ended tube sound.

I have listened to some push-pull tube amps *with moderate feedback* that do sound A LOT like a typical push-pull solid-state amp, but single-ended tubes with little to no feedback are quite another thing.
03-25-08: Bob_reynolds
In the system I was talking about I've had a tube SET amp and two different solid state amps. I heard no difference (except on some days the tubes made audible noise).

That statement summarizes everything that one needs to know about you Bob. You might make that quote your tag line. You bring nothing of value to this discussion.
Are we sure that studio use active speaker for sound quality reasons? Maybe it's for convenience or something else.

Try proaudioreview.com (?) and they commonly rave about the sound quality of passive speakers running Chord or Pass amps.
I prefer active speakers, but don't really think "sound quality" as audiofiles define it is what studios have in mind. More like:
1) Mixes that will sound good on a variety of stereos.
2) Elevated presence region to better hear faults in the recordings.
3) Ability to play super loud. Like 110-120dB all day.
4) Reliability: play at 110++dB ALL day without a breakdown.

Things like:
1)"truth of timbre".
2) grain-free sound
3) not bright highs
4) dynamic range
5) attack and decay
6) "air and space"
7) "fleshed out" sound

are important for home listening but less so in the studio.