Constant Power

[amirm]

The missing piece of the puzzle is what the speaker's frequency response curve is like up there. Take a look at the second graph in this link, which shows the effects of the brilliance control:http://www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-measurements

With the brilliance control max'd out we get the impedance curve that you posted, along with a 10 dB peak centered on about 17 kHz (when driven by a voltage paradigm amp)!

In this case, power paradigm amp + very low impedance in the high treble + 10 dB peak in the high treble = beautiful high treble!!

You see, the speaker's impedance curve zigs where the frequency response curve zags, and that's a recipe for potentially wonderful synergy with a power paradigm amp.

You are better than me in optical curve matching . I had to resort to Photoshop. This is what I get when I adjust the aspect ratios and overlay the impedance curve on top of frequency response:

I don't see the inversion you speak off. The two massive peaks in impedance < 1 Khz don't have corresponding dips in response. As a result, if I am following your arguments, they would cause sharp increases in frequency response in those regions, adding significant low-mid frequency colorations to a speaker that was already bass heavy.

I don't see how any speaker with such wild variations in impedance would have been designed with "constant power" amps in mind. Or any tube design with that super low high frequency characteristics. In that regard, I think the recommendation you heard from SoundLab folks was not based on any of this. But rather, as I pointed out to Ralph, was a preference the listener had developed for the heavily modified frequency response and not any sense of accuracy.

Isn't that virtual dead short at 20 kHz going to damage Ralph's amp? Nope, not even with a 20 kHz sine wave! Instead of frying its output stage trying to dump nearly infinite wattage into a dead short, like a "constant voltage" amp would, Ralph's amp delivers essentially no wattage into a dead short and so nothing overheats. In other words, into a very low impedance load, it starts to behave like a "constant current" amp.

Well, that constant current times the output impedance equals dissipated power in the output stage of his amp. Ralph, can your amp sustain short circuit this way? The reviewer's tube amp blew up even when just driving 1-4 watts.

 

[KeithR]

This one strikes me as an (even more) esoteric installment of the old musical vs accurate argument. One extremely small subset of the high end, based in mid 20th-century technology, seems to be claiming musical superiority to all. The "superiority" doesn't show in the numbers. The "technology" (so unique it requires its own language) has failed to achieve broad acceptance (indeed we seem to have the one manufacturer here, in this discussion), even in the highest of the high end where the bizarre is often lauded. And arguments in its favor are put forth with statements that dismiss the best products in the business as sounding like "good hifi" vs. "real music."

Remove the great technical detail put forth to explain the objectively poor performance but failing to explain why all these distortions and limitations would sound more like "real music," and we could be talking about five-figure turntable feet. This hobby has sold bits of pottery you stick to the walls to make "good hifi sound like real music," why not an amp? Even if you are required to play it through Lowthers or Kilpsch?

There will always be a few who will embrace this stuff, wrap themselves in the fuzzy blanket of THD and call it musical. There will always be the many designers, engineers, music makers, music lovers and audiophiles who will prefer "good hifi."

No one ever changes sides, and if I'm the only one who found the "good hifi vs. real music" remark too arrogant, ridiculous and predictable to even be effectively offensive, few are even paying attention. Carry on.

Tim

Please define "objectively poor performance" and "distortion" as it relates to your argument. Bose has "broad acceptance," so we know that isn't the right answer at times. Here are the recent measurements on Ayre AX-5- a no global negative feedback design (to escape the manufacturer on this thread, albeit one he spoke about for SS):

http://www.stereophile.com/content/ayre-acoustics-ax-5-integrated-amplifier-measurements

does this show a "blanket of distortion" that is "musical?"

btw, I assume you think Nelson Pass is a competent designer, so here is his white paper on the subject. I would be curious to hear your critique.

https://passlabs.com/articles/audio-distortion-and-feedback

 

[andy_c]

GE showed that humans have a high tolerance for even ordered harmonic distortion, not odd ordered. Keep that distinction in mind.

Let's clarify this a bit. What you are saying is this, "I, Ralph Karsten, claim that someone who happened to work at GE in the 1950s made a claim during that time period about the relative audibility of even- vs odd-ordered harmonic distortion components. I won't tell you the name of that person, nor give you a reference to the article. I will, however, state that this claim is attributable to GE as a whole, rather than the unspecified person who wrote the unspecified article, and that the claim can be considered as gospel truth, and applies once and for all time. Trust me."

 

[FrantzM]

Hi

I must say that at this stage f the discussion I don't see anything to support the claims of a Power Paradigm.. All the contrary. If it is a preference by all means carry on, just don't insist on making of what I have read so far, a technically valid and superior "paradigm".
I would have also preferred to see less attacks on the poster as exemplified by assertions of "not reading " or "not understanding" I , insisting on "I" read, understood, and am not convinced , I am hardly alone .

 

[Phelonious Ponk]

Please define "objectively poor performance" and "distortion" as it relates to your argument. Bose has "broad acceptance," so we know that isn't the right answer at times. Here are the recent measurements on Ayre AX-5- a no global negative feedback design (to escape the manufacturer on this thread):

http://www.stereophile.com/content/ayre-acoustics-ax-5-integrated-amplifier-measurements

does this show a "blanket of distortion" that is "musical?"

btw, I assume you think Nelson Pass is a competent designer, so here is his white paper on the subject. I would be curious to hear your critique.

https://passlabs.com/articles/audio-distortion-and-feedback

The THD numbers and output impedance disqualifying the amp from use with the overwhelming majority of even high-end speakers are enough to define "objectively poor perfromance" for me. YMMV.

Bose does not have broad acceptance in high end audio.

I don't have time to read the Pass article right now. Does he find 40% THD acceptable? Does he say that designs other than his own are "good hifi," and his sound like "real music?" Those are the two statements I was responding to.

Tim

 

[microstrip]

(...) I think as a society, we have decided what is old, is once again cool. It is also the case that every audiophile seems to wake up in the morning and decide to set up shop making speakers or amps. Whether they have any design expertise, or resources to properly measure and evaluate what they have built or not. So such proliferation to me is not evidence of some approach being right from technical point of view. I had a local designer bring some tube amps to us to sell. I was horrified how distorted and bad they sounded. They looked very pretty and such with glowing tubes but there was nothing euphoric about the distortions it produced. Even when they offered to leave them at our shop for free I refused to take them up on the offer. Stuff like this should not be in the market. Anyone seemingly can get a schematic for a tube amp, build a few with fancy components and call it the day. Bad idea all around.

Amir,

I can only conclude that your views on tubes are now strongly biased by your poor experience. But just think that some other people decide that what is modern and scientific is cool and must sound good. It helps keeping world equilibrium.

BTW, can I also conclude from your posts that your local tube audio designers and boat technicians are a disaster?

 

[mep]

mep, if the amplifier imposes a coloration (in this case, brightness and harshness) then if the speaker is worth its salt it will also reproduce that. So if there is such a coloration the speaker will never sound like real music no matter how good it is. This is simply a matter of understanding that a speaker can't sound like real music if the amp driving it doesn't either. It really is that simple. Go back and read my comments again and you should be able to see that this is what I was saying all along.

Ralph-You need to go back and reread what you said and I will summarize it as follows:

1. If a speaker requires an amplifier that uses negative feedback to sound its best, it's a flawed speaker design and will never sound real.
2. If an amplifier uses negative feedback, it is a flawed design.

 

[microstrip]

Just FIY:

Euphonic Distortion: Naughty but Nice?
By Keith Howard • Posted: Apr 30, 2006

I read several articles by Jean Hiraga on this theme long ago. Unhappily the references were not easily accessible.

http://www.stereophile.com/reference/406howard

 

[amirm]

Amir,

I can only conclude that your views on tubes are now strongly biased by your poor experience.

One sample story should not amount to drawing conclusions about one's views . It is true that the recent samples I have heard in our showroom have all been horrible. But I also have heard good tube sound from Steve's room to say, VTLs at CES. I firmly believe that people who have tube amps do enjoy their sound more than equiv. transistors. The simple explanation of that, which is re-enforced in my mind in this thread, is that the improvement comes from implicit EQ created in this combination of amp+speaker which in that room and with their ears is a positive. I believe it is less accurate to what is in the source but that may not a priority for the listener. To wit, I doubt very much any music we listen to was produced using constant power paradigm amps. They were all probably created with amps using negative feedback and therefore what the talent heard was not have been "real music." Sorry Ralph .

But just think that some other people decide that what is modern and scientific is cool and must sound good. It helps keeping world equilibrium.

As you know, those people, have a ton of objective and subjective data to show that such designs come far closer to a "wire with gain" paradigm of an amplifier. It is that which compels many to think their equipment "sounds good." The other camp doesn't have this so the camps are not equally situated.

BTW, can I also conclude from your posts that your local tube audio designers and boat technicians are a disaster?

All boat technicians are a disaster . Local or otherwise. When I bought my last boat, I made a list of 86 items that violated safety or electrical rules! And this was a brand new, high-quality boat. I gave the list to the company owner and he was so impressed, he doubled my boat warranty as a token of appreciation! I can instantly find quality problems with any boat at a boat show. So let's not get into that .

As to all local designers, I consider Bob Carver a local designer and while I have not heard his tube amp, I suspect it sounds a lot better than others I have heard locally.

 

[Duke LeJeune]

You are better than me in optical curve matching . I had to resort to Photoshop.
I don't see the inversion you speak off.

I was talking specifically about the area north of 10 kHz. You'll see the inversion there.

The two massive peaks in impedance < 1 Khz don't have corresponding dips in response. As a result, if I am following your arguments, they would cause sharp increases in frequency response in those regions, adding significant low-mid frequency colorations to a speaker that was already bass heavy.

The frequency response curve you posted is conceded to be unreliable in the accompanying text:

"The sloping-down from the lower midrange to the treble is, I believe, due to the proximity effect featured by a large panel—ie, the diaphragm size is significant compared with the microphone distance—and should be ignored."

So I don't think the speaker actually started out so bass-heavy.

Something that I forgot to take into account when I made my post is this: SoundLabs have rather "aggressive" four-position level controls for the bass and midrange. I believe these controls switch between different taps on the low-frequency and high-frequency transformers, and at any rate they have a dramatic effect on the impedance curve. My guess is that the controls were set up optimally for the solid state amp (max'd out). We'd use very different settings with a power paradigm amp.

I don't see how any speaker with such wild variations in impedance would have been designed with "constant power" amps in mind. Or any tube design with that super low high frequency characteristics. In that regard, I think the recommendation you heard from SoundLab folks was not based on any of this. But rather, as I pointed out to Ralph, was a preference the listener had developed for the heavily modified frequency response and not any sense of accuracy.

Again, my bad for not taking the bass and midrange controls into account.

 

[Duke LeJeune]

I had a local designer bring some tube amps to us to sell. I was horrified how distorted and bad they sounded. They looked very pretty and such with glowing tubes but there was nothing euphoric about the distortions it produced. Even when they offered to leave them at our shop for free I refused to take them up on the offer. Stuff like this should not be in the market. Anyone seemingly can get a schematic for a tube amp, build a few with fancy components and call it the day. Bad idea all around.

Not all tube amps are created equal. Unless that designer learns from his experience, he is not going to be in business for very long.

What speakers were you using, if you don't mind?

Thanks.

edit: Also, what type of tube amp?

 

[ack]

The simple explanation of that, which is re-enforced in my mind in this thread, is that the improvement comes from implicit EQ created in this combination of amp+speaker which in that room and with their ears is a positive. I believe it is less accurate to what is in the source but that may not a priority for the listener.

It's hard for me not to come to the same conclusion...

 

[mep]

Not all tube amps are created equal. Unless that designer learns from his experience, he is not going to be in business for very long.

What speakers were you using, if you don't mind?

Thanks.

It might have been those bad kind of speakers that require an amplifier with some amount of negative feedback to sound their best.

 

[Duke LeJeune]

It might have been those bad kind of speakers that require an amplifier with some amount of negative feedback to sound their best.

It might have been.

What speakers were you using when you switched from tubes to solid state?

 

[mep]

It might have been.

What speakers were you using when you switched from tubes to solid state?

Definitive Technology BP7000SC. And they weren't any type of tricked out Phase Linear Series 2 amps. I have two of them. One is bone stock from the original owner and the other had been gone through by a local tech before I bought it. He replaced the power supply caps with some new caps that were bigger. Honestly, I can't tell any difference in SQ between the two amps. My Jadis Defy 7 MKII sounded great on my Def Tech speakers, but it liked to eat output tubes and cathode fuses and I grew sick of it. I found out how much bass with the Jadis I was missing when I installed the Phase Linear amp. I no longer use the Phase Linear amps, but they are still taking up space at my house and one of these days I will have to send them on to a new home. I have since moved on to the Krell KSA-250 that made two round trips to the factory to have the caps replaced and a hum issue sorted out. I am currently using a pair of KEF LS50 speakers with the KSA-250. I'm not sure if the LS50 are evil speakers that need an amp with negative feedback or if they are good speakers that I'm ruining because I'm using an amp that has negative feedback. It's quite a quandary after reading Ralph's paper which started this whole deal off.

 

[amirm]

Not all tube amps are created equal. Unless that designer learns from his experience, he is not going to be in business for very long.

Sadly I think they do stay in business long. The B&W speaker company is the most successful brand/company in high-end yet put them behind a curtain and they lose in fidelity to others half their price. They have a fundamental design flaw which at the same time, is their genius in marketing/look of the speaker. So again, none of these factors are proof points of good or bad designs. Market success hinges on many other factors.

What speakers were you using, if you don't mind?

Revel speakers and in the past, Paradigm. I usually do my testing on the Revel Salon 2.

edit: Also, what type of tube amp?

I don't recall the type or even the brand. Maybe it was class AB with output transformers but I won't swear to it .

 

[Duke LeJeune]

Definitive Technology BP7000SC. And they weren't any type of tricked out Phase Linear Series 2 amps. I have two of them. One is bone stock from the original owner and the other had been gone through by a local tech before I bought it. He replaced the power supply caps with some new caps that were bigger. Honestly, I can't tell any difference in SQ between the two amps. My Jadis Defy 7 MKII sounded great on my Def Tech speakers, but it liked to eat output tubes and cathode fuses and I grew sick of it. I found out how much bass with the Jadis I was missing when I installed the Phase Linear amp. I no longer use the Phase Linear amps, but they are still taking up space at my house and one of these days I will have to send them on to a new home. I have since moved on to the Krell KSA-250 that made two round trips to the factory to have the caps replaced and a hum issue sorted out. I am currently using a pair of KEF LS50 speakers with the KSA-250. I'm not sure if the LS50 are evil speakers that need an amp with negative feedback or if they are good speakers that I'm ruining because I'm using an amp that has negative feedback. It's quite a quandary after reading Ralph's paper which started this whole deal off.

Thanks for the information, mep. I couldn't find an online impedance curve for the Definitive Technology BP7000SC, but based on your experience it's apparently designed to work best with voltage paradigm amps. As is the KEF LS50.

Seems to me the Def Tech's bass response would largely be a function of how its subwoofer's level is set, but maybe I'm missing something.

On the issue of speakers design, you and I are not so far apart. The Def Techs are bipolars, and your KEFs have an exceptionally well-controlled radiation pattern. My best designs are controlled-pattern bipolars. You and I would probably find more common ground in a loudspeaker thread.

 

[Duke LeJeune]

Sadly I think they do stay in business long. The B&W speaker company is the most successful brand/company in high-end yet put them behind a curtain and they lose in fidelity to others half their price. They have a fundamental design flaw which at the same time, is their genius in marketing/look of the speaker. So again, none of these factors are proof points of good or bad designs. Market success hinges on many other factors.

While I agree with your example in general, it doesn't apply to any small tube amplifier company because they do not begin to have the marketing muscle of B&W.

Revel speakers and in the past, Paradigm. I usually do my testing on the Revel Salon 2.

I don't recall the type or even the brand [of tube amp]. Maybe it was class AB with output transformers but I won't swear to it.

Swear to it or swear at it??

I don't see any thing in the Revel's curve that would induce distortion, so based on your experience sounds like that amp had major problems.

But its impedance curve says "voltage paradigm amps" to me. A tube amp would sound forward and bright maybe even harsh because it would be extra loud in the 2-4 kHz region, while being weak in the bass region and through most of the midrange. The higher the output impedance, the moreso.

http://www.stereophile.com/content/revel-ultima-salon2-loudspeaker-measurements

Conspicuous by its absence is the upper impedance peak of a typical reflex box. Normally we'd expect a tube amp to delivery pretty good wattage into that peak, but it's not there. Verrrry interesting! Do you know why it's not there?

BTW the Revels have very well thought-out radiation patterns in my opinion. Excellent speakers.

 

[mep]

Seems to me the Def Tech's bass response would largely be a function of how its subwoofer's level is set, but maybe I'm missing something.

What I and some others have discovered that even though you may have a pair of speakers with built in powered amps for the built in subwoofers, the amp that drives the main speakers becomes dominant in the total quality of bass. In the case of the Def Techs, the built in amps were getting their bass signal from the speaker input terminals which of course are connected to the main amp that drives the speakers. The second time I sent my Krell KSA-250 back to Krell to have the hum gremlin chased down and killed, I bought an ARC VS115 amp with KT-120 tubes to use. Surprisingly, I had to turn the bass down with the ARC VS115 from where it was set with the Krell which surprised me.

 

[microstrip]

Sadly I think they do stay in business long. The B&W speaker company is the most successful brand/company in high-end yet put them behind a curtain and they lose in fidelity to others half their price. They have a fundamental design flaw which at the same time, is their genius in marketing/look of the speaker. So again, none of these factors are proof points of good or bad designs. Market success hinges on many other factors.

Amir,

Just to say that I have listened to great sound from B&W speakers. Can we know why do you consider them the most successful and what is their "fundamental design flaw"?

Disclaimer : I still own their old Silver Signature SS25 speakers and, coupled with adequate solid state amplifiers, they sound great. And, having listened to the Nautilus active in great conditions would not mind owning it if I had the room to host it!