Stereophile | January 2017 Issue

[andromedaaudio]

To add to the set story ,i mainly sold the zanden because i t couldnt drive/ control those 11 and 12 inch woofers properly
With double 8 inchers it worked fine.
If the zanden would have accomplished it ,IT would have been a nice simple " cheap "system
Would Love to hear a lamm set once on the speakers

 

[morricab]

OK I won't bow out.
It is most probable that most cones are not pistonic over the whole frequency range they are used for. Those made from traditional materials definitely are not. What I wrote was that the material does not matter if the cone is in its pistonic range, and this is true.
It may well be that there are loudspeakers today with stiff enough light enough cones and steep enough crossover filters for each driver to remain in its pistonic zone for the whole of the range it covers. This would give less colouration and distortion than other speakers (all other engineering aspects being dealt with properly).

There is not much understanding of vibration, resonance and its excitation, my field of research before I went Formula 1 motor racing, even amongst otherwise experienced and knowledgeable engineers never mind people who have never studied it. My second boss when I was a young research engineer could only visualise things as a quasi-static way and whilst he accepted what the maths showed he never understood or could solve vibration based problems. Pretty well every engineering catastrophy I and my group came to troubleshoot (and we were the last resort after everybody else had tried to solve it) was caused by unanticipated resonance.
It is an interesting subject and I have used it all my career, though much less in Formula 1, though it was part of my design of the Williams active suspension system used on several World Championship winning cars until it was banned. I am very proud of that

Ironically the materials stiff and light enough to produce pistonic mid range and high frequency units divide opinion strongly in the hifi community. Maybe resonance which should not be are being excited (easily measured) maybe we are so used to the low level of extra harmonics being added in conventional speakers we are disquieted by its removal. I don't know, or even care that much since I probably won't be buying any more speakers ...

And what was often the root cause of those unanticipated resonances? Was it unanticipated because it was outside standard theories or was it due to ignorance of best practice with regard to vibration and resonance control?

 

[morricab]

To add to the set story ,i mainly sold the zanden because i t couldnt drive/ control those 11 and 12 inch woofers properly
With double 8 inchers it worked fine.
If the zanden would have accomplished it ,IT would have been a nice simple " cheap "system
Would Love to hear a lamm set once on the speakers

Why should the size of the woofers matter? In the old days, all the woofers were huge and SETs did just fine. Were they low sensitivity?

Wilson X1 has a big 15 inch Focal sourced woofers (and a 12 incher as well) and works great with SET. So does JM Lab Grande a Utopia Be EM, which also has a 15 inch woofer.

Maybe the cabinet design is poorly damped and needs a high damping amplifier?

 

[andromedaaudio]

Did they drive them with 8 300 B Watts?
All i can say is a large piston needs a strong motor.
Im talking properly driven with full maximum dynamic impact
And yes the ones i use have high efficiency iirc at least as good as the focal audiom woofers used in big Wilsons
Looked at them and didnt use them because of other reasons mine have lower resonance freq 19 Hz for the 11 inch.
The amp never clipped .as i tried in my situation
But if it worked good for them
There are other reasons of course as the focals have a different motor design

 

[f1eng]

And what was often the root cause of those unanticipated resonances? Was it unanticipated because it was outside standard theories or was it due to ignorance of best practice with regard to vibration and resonance control?

Always due to ignorance about vibration.

 

[morricab]

Did they drive Them with 8 300 B Watts?
All i can say is a large piston needs a strong motor.
Im talking properly driven with full maximum dynamic impact
And yes the ones i use have high efficiency iirc at least as good as the focal audiom woofers used in Wilson
Looked at Them and didnt use Them because of other reasons mine have lower Fs resonance freq 19 Hz for the 11 inch

8 watts may be borderline but probably a bigger issue may be the output iron

 

[f1eng]

If you look at the distortion characteristics of darTZeel amplifiers there is no way that there is not a significant amount of character coming from the amplifier. It might not be "warm" or "sexy" but there is something there for sure. Based on psychoacoustic measures within a good designed SETs limits the distortion they produce should be largely inaudible because of the relative lack of high order harmonics. KR SXI review is a good example from Australia. At 50 watts, it of course measures quite high in distortion (6%) but still with low orders dominant. However, at 1 watt there is only 2nd harmonic at about 0.5% and 3rd harmonic at 0.01%! No other harmonics were above the noise baseline. What is clear is that you don't want to push it to 50 watts if you can help it. However, for brief peaks it is probably not so bad and probably not even audible. Why? Well, because as Cheever rightly points out, the tolerance of the ear/brain for distortion increases with increasing volume...so the louder it is, the less sensitive to distortion you get. Could be why the darts sound more capable when pushed because what they do wrong is less audible as it gets loud...it seems their character doesn't change much as the level increases, which is s a good thing.

That tonality and timbral "sexiness" that you think is additive, well its not with a really good SET, its real tone of real instruments and with decent (they don't even have to be great) recordings this comes through clearly. Good SETs have low enough distortion and of the right type at moderate power outputs to be psychoacoustically inaudible. If they made 6% at 1 watt then you would likely have a valid point even if that 6% was pure 2nd harmonic...it would be likely audible then and "plumping" up the sound somewhat.

What you may have heard from many (maybe even most) SETs is distortion from transformer saturation...which is audible and results in a perception of bass looseness as well as a false "warmth". It affects most of them so I am not surprised if you haven't heard one without this issue or at least minimal issue. You do, however, have experience with OTL bass, which is actually quite good from a circlotron design (older Futtermans seem to have bass issues from stability points in the designs). I am familiar with this kind of bass as well, having had OTLs in the past and having heard at length the Tenor 75 watters. There are a few SETs out there that have bass like this but with more slam. Only a few, but they exist. I can understand if the distortion from saturation disturbs you...it bothers me as well and why I don't think all SETs are great. Problem is that a lot of PP tube amps have the same issue with the output transformer as well as number of other issues.

I have had true full range systems in the past (Infinity, Genesis, Acoustat(yes Acoustat I got flat in-room to 20hz) and with subs I get there now (18 hz anyway). I did not find that the extension of the system per se added to the beauty of the sound...I found going to better electronics that have less AUDIBLE impact on the sound did allow the beauty in the music to emerge.

From Fremer:
"Now that I've got a pair of Wilson's 92.6dB-sensitive Alexandria XLFs (I reviewed them in the January 2013 issue), I felt it was appropriate to review the ML3 with them, and even though I'm not a technical person, Lamm agreed. As JA pointed out in his measurements of the XLF, "Despite the Alexandria's imposing bulk, it will play at high levels with only a few watts. (During the in-room measurements, performed at a reasonably loud level, the darTZeel [NHB-458] amplifiers' meters never indicated more than 5W peak.). . . . [T]he speaker will not be a difficult load for the partnering amplifier to drive."

How many watts are you typically pushing out? Since the amps have meters you can relate this to us.

We are going to disagree again
The two things which definitely change the sound of an amplifier are its distortion characteristic and its output impedance.
The first changes the timbre of instruments, many people like this but anything above 0.1% is audible, not objectionable maybe, but definitely a change. A high output impedance alters the frequency response of speakers, considerably if the have high reactance and the output impedance is above 0.2 ohms.

Lots of people love this sort of equipment like you do though.

 

[microstrip]

We are going to disagree again
The two things which definitely change the sound of an amplifier are its distortion characteristic and its output impedance.
The first changes the timbre of instruments, many people like this but anything above 0.1% is audible, not objectionable maybe, but definitely a change. A high output impedance alters the frequency response of speakers, considerably if the have high reactance and the output impedance is above 0.2 ohms.

Lots of people love this sort of equipment like you do though.

Although both are true, they are not the unique and perhaps more significant parameters that define the main and unique sound characteristics of an amplifier. Take a solid state amplifier with negligible output impedance and insert a .3 ohm resistor in series with the output - it will not sound like a DartZeel, even in the bass.

Connect a Darzteel to a 84 dB/W, a 91 db/W or to a 103 dB/W speaker and play at the same sound level. The main sound characteristics of the amplifier remain. However if you look at the available graphs of distortion versus power and frequency you will see that the distortion characteristics with the different speakers are completely different.

IMHO the debate on amplifier sound is very complex and each of us focus in his favorite subject. Integrating them all is not easy.

Do you remember the Sterephile review of the Krell 300s and Cary 805 in the same issue? BTW, I referred to the Dart because I tried this experiment long ago with it.

 

[Believe High Fidelity]

I have my own viewpoint, which is that an SET 'adds' a bit of sexiness, tonal and timbre weight, which covers areas where it lacks. when pushed you find limits.

until one hears the full range approach check all the boxes I would not expect an SET lover to accept it can be done.

Not a matter of SS or SET when handling FR.

What you may have heard from many (maybe even most) SETs is distortion from transformer saturation...which is audible and results in a perception of bass looseness as well as a false "warmth". It affects most of them so I am not surprised if you haven't heard one without this issue or at least minimal issue. You do, however, have experience with OTL bass, which is actually quite good from a circlotron design (older Futtermans seem to have bass issues from stability points in the designs). I am familiar with this kind of bass as well, having had OTLs in the past and having heard at length the Tenor 75 watters. There are a few SETs out there that have bass like this but with more slam. Only a few, but they exist. I can understand if the distortion from saturation disturbs you...it bothers me as well and why I don't think all SETs are great. Problem is that a lot of PP tube amps have the same issue with the output transformer as well as number of other issues.

I wholeheartedly agree with this being the cause of both the good and the bad in peoples experiences with SET amplification. Coloration in a beneficial way is associated with SET amplification and that is only applicable to substandard designs. Real SET amps do not have strong coloration, but present music in a natural sounding organic fashion. All components color the sound, but to the extent tube amplifiers are know for again is in substandard designs

I have heard a large number of systems and FR is more demanding that things be up to par. Some of the best systems used PP designs and do not have tube coloration in them anywhere. However, all components in the chain must be of equal caliber lest your imbalances be made apparent

 

[marslo]

Don't have the Walls anymore. They were good rather than great IMO. They were palpable, had nice tonality, and decently transparent but bass was not authoritative enough and some inner resolution was ultimately missing. This became clear compared to some other great SETs. I have now the Ayon Crossfire III, which is better all around.

I have a Mirage BPS-210 servo bipolar sub. It goes deep with low distortion and plays loud enough for my small room. It also has a good control box with nice adjustability for being all analog. I actually don't feel the need to use it so often though.

IMHO Ayon Crossfire III with Ayon's recti is one of the most underestimated SET' s available.
This recti makes a difference.
My Ayon can drive AG Duo Mezzo XD louder without audible distortion than any other tube amp I have auditioned at home. And give much more organic and lifelike sound than any other SS amp I tried.

 

[YashN]

Great SETs have no global feedback, great linearity, and simplicity of circuits, making them revealing of especially mid-range content, but also have excellent transient responses and recovery.

 

[SCAudiophile]

IMHO Ayon Crossfire III with Ayon's recti is one of the most underestimated SET' s available.
This recti makes a difference.
My Ayon can drive AG Duo Mezzo XD louder without audible distortion than any other tube amp I have auditioned at home. And give much more organic and lifelike sound than any other SS amp I tried.

Thanks for the response; the Crossfire and others above it in the line are fine amps, no doubt. Have thought about moving to them more than once in the last couple of years!

 

[bonzo75]

Marslo, which other SET amps have you compared to?

 

[morricab]

Thanks for the response; the Crossfire and others above it in the line are fine amps, no doubt. Have thought about moving to them more than once in the last couple of years!

Give one a go!! Or an Aries Cerat ! Both are great!

 

[morricab]

We are going to disagree again
The two things which definitely change the sound of an amplifier are its distortion characteristic and its output impedance.
The first changes the timbre of instruments, many people like this but anything above 0.1% is audible, not objectionable maybe, but definitely a change. A high output impedance alters the frequency response of speakers, considerably if the have high reactance and the output impedance is above 0.2 ohms.

Lots of people love this sort of equipment like you do though.

You are right, we are going to disagree again. Because it is clear that distortion of low order is inaudible up to much higher levels than 0.1%. 2nd order harmonic, in particular has been shown to be inaudible up to around 2% with pure tones. That means with real music the threshold will be higher. The dependence of harmonic order on that harmonics audibility is strongly non-linear and gets dramatically more audible as the harmonic order increases. This has been known at some level since the 1920s and 30s and begun to be defined in the 1950s. Recently, CHeever came up with a model that is dependent on harmonic order and SPL. It shows that even a little bit of high order harmonic distortion that is out of the expected PATTERN of the ear/brain's own harmonic pattern becomes very obvious, whereas an amp that can mimic the ear/brain distortion pattern...at all SPL...will for all intents and purposes be inaudible. According to Cheever, only the SET can approximate the natural ear/brain distortion pattern...push/pull and high feedback destroy the monotonic (exponential decay) pattern found in nature. Geddes came up with another metric, derived more from functions that make distortions, but had a similar conclusion that low distortion can sound much worse than high distortion depending on the content of that distortion.

It seems that humans are far more forgiving of linear distortions (like Frequency response) and these do not have serious impact on the realism of the sound as long as they are grossly out of whack. A damping factor of 5 or greater will be sufficient for an amp to have less than +- 1db FR, which is better than nearly any non-corrected speaker system. Only grossly underdamped speakers will be a problem for the bass.

What do you mean exactly by lots of people love this sort of equipment? You mean those who love natural sound or those who love listening to distortion? Or?

 

[YashN]

According to Cheever, only the SET can approximate the natural ear/brain distortion pattern...push/pull and high feedback destroy the monotonic (exponential decay) pattern found in nature.

...and the way sound moves naturally though air.

I extend this naturalness to the use of high-rate DSD into a native DSD DAC into a SET.

 

[KeithR]

You are right, we are going to disagree again. Because it is clear that distortion of low order is inaudible up to much higher levels than 0.1%. 2nd order harmonic, in particular has been shown to be inaudible up to around 2% with pure tones. That means with real music the threshold will be higher. The dependence of harmonic order on that harmonics audibility is strongly non-linear and gets dramatically more audible as the harmonic order increases. This has been known at some level since the 1920s and 30s and begun to be defined in the 1950s. Recently, CHeever came up with a model that is dependent on harmonic order and SPL. It shows that even a little bit of high order harmonic distortion that is out of the expected PATTERN of the ear/brain's own harmonic pattern becomes very obvious, whereas an amp that can mimic the ear/brain distortion pattern...at all SPL...will for all intents and purposes be inaudible. According to Cheever, only the SET can approximate the natural ear/brain distortion pattern...push/pull and high feedback destroy the monotonic (exponential decay) pattern found in nature. Geddes came up with another metric, derived more from functions that make distortions, but had a similar conclusion that low distortion can sound much worse than high distortion depending on the content of that distortion.

It seems that humans are far more forgiving of linear distortions (like Frequency response) and these do not have serious impact on the realism of the sound as long as they are grossly out of whack. A damping factor of 5 or greater will be sufficient for an amp to have less than +- 1db FR, which is better than nearly any non-corrected speaker system. Only grossly underdamped speakers will be a problem for the bass.

What do you mean exactly by lots of people love this sort of equipment? You mean those who love natural sound or those who love listening to distortion? Or?

That's ironic as I feel like I'm swimming in distortion with my past few SET auditions. Many people prefer 3rd order over 2nd order distortion, so that is probably why. I have not been happy with SET bass practically ever. No, I have not heard a KR in my system

By perusing Cheever, appears he did a Masters thesis in 2001 for his MSEE but isn't even in the industry - amplifiers have changed quite a bit since then and he never did any followup, nor was this reviewed or presented. He opens with the infamous Bryston vs Cary Stereophile examples from the early 90s (and yes, that Cary 300SEI is a crap amp as is the Bryston). He used a Hafler and his own custom built 1.5 watt SET, not exactly the creme de la creme. It also wasn't a scientific study (5 listeners, single blinded) that utilized 16 ohm Radio Shack speakers from the 60s (lol).

http://www.dancheever.com/

So "citing" Cheever isn't a big deal to me, although he makes some interesting points that you clearly agree with. If you have any more recent studies done on distortion, I'd enjoy reading them sometime.

 

[f1eng]

What do you mean exactly by lots of people love this sort of equipment? You mean those who love natural sound or those who love listening to distortion? Or?

Lots of people love the sort of equipment like SET amplifiers and record players which have audible levels of euphonic distortion, often lots. Since most modern recordings are mixed from multiple microphones placed much nearer to the instruments than any listener (other than the player themselves) ever listens I think the concert hall experience can perhaps be more realistically imagined if these sorts of harmonic additions are made.
SET amps are very simple circuits, which would be a good thing IMO if they were also linear, but they are not, usually nowhere near.
I personally believe that these harmonic additions are audible and that is why some people like this sort of equipment (and speakers which have the same type of additions).

"Natural sound" may have to be simulated in recordings where microphone choice and position makes the raw recording somewhat unreal, as is often the case.

In my own amateur recording efforts I have found that microphone choice and position makes the most difference to sound quality, with the recorder less important. If that is not well done, and IME in many recordings it is not, a linear low distortion replay system will not sound as nice as one with loads of built in euphonic harmonic additions.

0.5% 2nd harmonic distortion definitely changes the timbre of a musical instrument.

Frequently I see good reviews of equipment which has major non-linearities in Stereophile. There is the age old question of "does it sound nice because of the distortion or despite it". I am firmly in the camp of those who believe the former.

 

[bonzo75]

Seems to be quite a match between PH.D in Analytical Chemistry vs F1 Engineer and Nuclear physicist.

That said, the best sound is with a car salesman.

 

[YashN]

I personally believe that these harmonic additions are audible and that is why some people like this sort of equipment

A common misconception...

Neutrality is the goal of great SET designs.

It so happens that the 2nd order harmonic distortion that is prevalent is of the musical type, much like C4 is an octave higher than C3 and exactly twice the frequency.

Making more of that distortion isn't the goal of building a great SET.