Stereophile | January 2017 Issue

[NorthStar]

Lexicon

Regarding the Lexicon SL-1 speakers.

I'd say it's even more than interesting; it's a totally new departure from what we are used too. ...It's...complex; simplicity doesn't enter the door here.
This is the world of DSP and multiple drivers...lots of them.

And, it has no "fatal attraction" like few ultra hi end speakers have. I would even venture to say that they are "ugly".
Please forgive me for using such a vulgar world to describe "unattractive". It's my way to emphasize my true artistic critical impression. :b

Will it fly? Perhaps with angels above lifting them up to the heavens... ;-)
_______

Interesting Bob. Makes my MBL 116's look pretty simple in execution.

 

[f1eng]

Nice theory but show me one material that truly behaves that way. There is always some bending/flexing occurring that will transmit the character of the material while in-band and it will not be a true piston. A true long ribbon will probably have the least inherent character of it's own because it has a resonance of only a few hz and is uniformly driven over it's whole surface (for a pure metal one at least). As for materials that are very rigid like ceramic, they breakup so badly out of band that the modes are easily heard and are never fully suppressed by notch filters and the like. Doped carbon fiber sort of works but is still not rigid enough to be totally silent; however, it can behave well out of band.

A simple experiment to conduct is to take a piece of paper and just bend it back and forth...it makes distinctive sound. Now do the same with a similar thickness piece of plastic or aluminum. The acceleration from the voice coil is 10s of times greater and despite the cone profile helping things there will be flex in the cone. Laser interferrometry will confirm this.

Your experiment of "bending a piece of paper back and forth" is absurd. The whole point of using a material in its pistonic frequency range is because it is up to that frequency it is NOT BENDING BACK AND FORTH!!!!!

I have used laser interferometry for vibration research. Laser interferometer confirms that up to the first natural frequency the cone (or dome) moves as a piston, so the material has no sound of its own. So I don't need to show you one material that works this way, they all do. Above that frequency you get loads of pretty modal shapes with different magnitudes of vibration. Materials which have low internal damping have sharp, high, narrow peaks, ones with an applied damping layer have wider lower peaks so plenty of changes to the sound possible. This is not new science. It has been well understood for all of my 45 years as an practicing engineer.

Certainly producing a loudspeaker where one is not listening to the sound plus that added by cone breakup is very difficult, maybe there aren't any. Most speakers on the market do not achieve it, at any price. The skill is in making the effect small and euphonic.
Ribbons could in principle be better, but it is pretty well impossible to get a completely even magnetic field over the whole ribbon in panel length ones, so they probably do flex both because of uneven drive and their thinness.

 

[morricab]

Your experiment of "bending a piece of paper back and forth" is absurd. The whole point of using a material in its pistonic frequency range is because it is up to that frequency it is NOT BENDING BACK AND FORTH!!!!!

I have used laser interferometry for vibration research. Laser interferometer confirms that up to the first natural frequency the cone (or dome) moves as a piston, so the material has no sound of its own. So I don't need to show you one material that works this way, they all do. Above that frequency you get loads of pretty modal shapes with different magnitudes of vibration. Materials which have low internal damping have sharp, high, narrow peaks, ones with an applied damping layer have wider lower peaks so plenty of changes to the sound possible. This is not new science. It has been well understood for all of my 45 years as an practicing engineer.

Certainly producing a loudspeaker where one is not listening to the sound plus that added by cone breakup is very difficult, maybe there aren't any. Most speakers on the market do not achieve it, at any price. The skill is in making the effect small and euphonic.
Ribbons could in principle be better, but it is pretty well impossible to get a completely even magnetic field over the whole ribbon in panel length ones, so they probably do flex both because of uneven drive and their thinness.

http://diy-audio.narod.ru/litr/Measurement_and_Visualization_Cone_vibration_2006.pdf

There are modes that occur below the first breakup. They may or may not have audible consequences.

Here is a question though, in a multitone real environment, the driver will be receiving tones, although muted by the crossover, that excite the breakup modes basically all the time. Many designers put the crossover about one octave above the resonance frequency of the driver...once a driver is now bending from breakup, it is not behaving pistonically, so will it be bending from other frequencies and accelerations that are in band? Once something is bending it is no longer rigid.


http://www.bowers-wilkins.com/Discover/Discover/Technologies/Kevlar.html

Watch the video. THey show a plastic cone bending like a "sea wave" according to the researcher. The Kevlar does it too but that it cancels out. I don't see how a thin metal cone would fare much better. Maybe ceramic or diamond...until the big breakup...

"Looking at the behaviour at a single frequency with a sine wave readily shows standing waves or resonances in the diaphragm at that frequency. It also gives an indication of the way the sound disperses as it leaves the cone. For example, at higher frequencies, a semi-flexible diaphragm can exhibit motion where little radiation comes from the outer area and most comes from the central region. "

"If we look at laser scans of the two different cones at different points in time after an impulse signal has been applied the conical shape of the diaphragm is lost in the process. At the time just after a signal has been applied, just the centre of the cone has started to move in both cases. "

Not very pistonic, I would say. In fact, B&W acknowledges their kevlar mid is not pistonic but they seem to be claiming no one else's is either and theirs disperses the resonances better, faster and with better HF dispersion.

I do see examples where at low frequencies they claim the whole cone moves in phase but at what amplitude? That is usually not given and I would think amplitude definitely matters because of the relative non-linearity of the surround material.

THere is other interesting research by Kippel that shows that when stiff cones are excited by pure waves below breakup they move together but this is not the real world of a loudspeaker driver.

 

[f1eng]

http://diy-audio.narod.ru/litr/Measurement_and_Visualization_Cone_vibration_2006.pdf

There are modes that occur below the first breakup. They may or may not have audible consequences.

Here is a question though, in a multitone real environment, the driver will be receiving tones, although muted by the crossover, that excite the breakup modes basically all the time. Many designers put the crossover about one octave above the resonance frequency of the driver...once a driver is now bending from breakup, it is not behaving pistonically, so will it be bending from other frequencies and accelerations that are in band? Once something is bending it is no longer rigid.


http://www.bowers-wilkins.com/Discover/Discover/Technologies/Kevlar.html

Watch the video. THey show a plastic cone bending like a "sea wave" according to the researcher. The Kevlar does it too but that it cancels out. I don't see how a thin metal cone would fare much better. Maybe ceramic or diamond...until the big breakup...

"Looking at the behaviour at a single frequency with a sine wave readily shows standing waves or resonances in the diaphragm at that frequency. It also gives an indication of the way the sound disperses as it leaves the cone. For example, at higher frequencies, a semi-flexible diaphragm can exhibit motion where little radiation comes from the outer area and most comes from the central region. "

"If we look at laser scans of the two different cones at different points in time after an impulse signal has been applied the conical shape of the diaphragm is lost in the process. At the time just after a signal has been applied, just the centre of the cone has started to move in both cases. "

Not very pistonic, I would say. In fact, B&W acknowledges their kevlar mid is not pistonic but they seem to be claiming no one else's is either and theirs disperses the resonances better, faster and with better HF dispersion.

I do see examples where at low frequencies they claim the whole cone moves in phase but at what amplitude? That is usually not given and I would think amplitude definitely matters because of the relative non-linearity of the surround material.

THere is other interesting research by Kippel that shows that when stiff cones are excited by pure waves below breakup they move together but this is not the real world of a loudspeaker driver.

I am familiar with all this.
I am afraid you are not understanding the physics but here is scarcely a forum for going back to University, so I will leave you with your misunderstanding and bow out.

 

[morricab]

I am familiar with all this.
I am afraid you are not understanding the physics but here is scarcely a forum for going back to University, so I will leave you with your misunderstanding and bow out.

I am afraid you are quite wrong and I understand exactly what is going on here. Your idea is a cheap swipe at my level of understanding (with no basis on fact) and leaving all with the presumption of superiority on the subject by "bowing out". You are an engineer I guess and I am a Ph.D in Analytical Chemistry. So, I understand spectroscopy and measurements based on interferometry quite well (been done for analytical measurements like IR spectroscopy for a long time). I am also well versed in lasers, having designed and built mass spectrometers that used them for detection purposes.

Your comments are a cop out to not have a serious discussion on this rather intriguing issue. I quite understand what it means to have "pistonic" behavior...in theory...I am saying in practice it doesn't happen and the fact that it does not leads to a lot of the "character" we hear from our speakers.

 

[bonzo75]

Regarding engineer, he was an f1 engineer and Schumacher's engineer when he won his first race. Apart from that I don't understand what you guys are talking about

 

[andromedaaudio]

haha bonzo

Really a F 1 engineer , respect

Regarding cones stiffness and resonance , i ve tried about everything and the stiffest dont sound the best , probably they are also subject to resonance /being so stiff , accuton ceramics and diamond i mean .
You have aluminium as well as carbon /plastic and what ever , regarding midrange nothing beats papercomposite imo , probably due to its abilty to desolve membrane resonance a natural way.

 

[Mike Lavigne]

haha bonzo

Really a F 1 engineer , respect

Regarding cones stiffness and resonance , i ve tried about everything and the stiffest dont sound the best , probably they are also subject to resonance /being so stiff , accuton ceramics and diamond i mean .
You have aluminium as well as carbon /plastic and what ever , regarding midrange nothing beats papercomposite imo , probably due to its abilty to desolve membrane resonance a natural way.

i think it's a mistake to assume that all approaches to use particular cone materials have the same results. i respect that you have particular experiences which are your dominant data points. I'm not discounting those.

like Bonzo says, you gotta listen with open ears and consider the whole system/room picture and hear what the total package does for the musical message.

 

[andromedaaudio]

Off course mike , i do like the kharma exquisite classic as well , never heard your E A , its only my opinion so far to my ears in my own designs

 

[morricab]

i think it's a mistake to assume that all approaches to use particular cone materials have the same results. i respect that you have particular experiences which are your dominant data points. I'm not discounting those.

like Bonzo says, you gotta listen with open ears and consider the whole system/room picture and hear what the total package does for the musical message.

If they figured out how to completely suppress the ceramic "coldness" character I have heard in every design using those drivers, then they would be the first. Kharma clearly gave up on them and went to carbon fiber and composites.

Maybe you have some insight there? Is it the ribbon tweeter? Crossover?

 

[Mike Lavigne]

If they figured out how to completely suppress the ceramic "coldness" character I have heard in every design using those drivers, then they would be the first. Kharma clearly gave up on them and went to carbon fiber and composites.

Maybe you have some insight there? Is it the ribbon tweeter? Crossover?

well.....i don't claim any techie insights to try and assign cause-result to components of speakers. and reading your perspectives I'm not sure our sonic compasses are close enough in alignment to make my comments relevant to your characterizations.

i prefer the darTZeel view on music, you prefer the SET view. we don't have to agree but i think that is more of our differences than our views on speakers.

 

[MadFloyd]

well.....i don't claim any techie insights to try and assign cause-result to components of speakers. and reading your perspectives I'm not sure our sonic compasses are close enough in alignment to make my comments relevant to your characterizations.

i prefer the darTZeel view on music, you prefer the SET view. we don't have to agree but i think that is more of our differences than our views on speakers.

Out of curiosity, what is the difference in character between darTZeel and SET (in your view), Mike? I have a little experience with both, but really not enough to be able to know.

 

[bonzo75]

Out of curiosity, what is the difference in character between darTZeel and SET (in your view), Mike? I have a little experience with both, but really not enough to be able to know.

Most SETs work only on high sensitivity speakers like horns. With something like NATs you could chance lower but definitely not on YGs or Apogees. I don't know if dartzeel could do those either.

I am not sure how Magico M works, but if you go to Rhapsody, you will get to compare his Vitus to the mega expensive Kondo Kagura on Magicos. http://zero-distortion.org/magico-vitus-kondo-rhapsody/

Then you will know the SET sound. Then listen to the SET sound on horns.

 

[Mike Lavigne]

Out of curiosity, what is the difference in character between darTZeel and SET (in your view), Mike? I have a little experience with both, but really not enough to be able to know.

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. there are many different SET's and different SET friendly speakers. whereas the darTZeel (458) gets out of the way of the music and does not add it's own character, has lower noise and is more extended and linear top and bottom, yet is liquid, nuanced and grain-less. the darts are capable of driving more full range speakers and when pushed it simply gets better. it is more complete.....but not quite as inherently sexy. but when optimized it has a greater upside. maybe the SET gets more nuance without so much effort. all the stars have to align to get that musical connection with the full range pathway.

what gets missed is that when you have a system with coherence and deep bass extension that the mid range gets a significant boost from true mid and deep bass linearity. vocals, horns, cellos, pianos etc. are sexy and tonally complete from the complete full range picture. an SET does it differently. but both do it.

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

 

[bonzo75]

From Mike's comment, "but not quite as inherently sexy. but when optimized it has a greater upside. maybe the SET gets more nuance without so much effort. all the stars have to align to get that musical connection with the full range pathway." this would have been difficult for me to appreciate, and easy to ignore, had I not heard the system. Very ordinary words BUT very true.

 

[andromedaaudio]

I ve owned a zanden 300 B set for a couple of years and drove a a couple of speakers of various efficiencies, which i also drove with SS and large power tube amps

I agree with this " when pushed you find limits " , although they created a more upfront soundbubble and sound natural , they also missed some sheer control ./drive.
I also drive them with 10 watts class A transistor , and the drive / control returns , although not as much as high power SS .

Ps mine are not as high in eff as mikes EA speakers

 

[f1eng]

I am afraid you are quite wrong and I understand exactly what is going on here. Your idea is a cheap swipe at my level of understanding (with no basis on fact) and leaving all with the presumption of superiority on the subject by "bowing out". You are an engineer I guess and I am a Ph.D in Analytical Chemistry. So, I understand spectroscopy and measurements based on interferometry quite well (been done for analytical measurements like IR spectroscopy for a long time). I am also well versed in lasers, having designed and built mass spectrometers that used them for detection purposes.

Your comments are a cop out to not have a serious discussion on this rather intriguing issue. I quite understand what it means to have "pistonic" behavior...in theory...I am saying in practice it doesn't happen and the fact that it does not leads to a lot of the "character" we hear from our speakers.

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 ...

 

[morricab]

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. there are many different SET's and different SET friendly speakers. whereas the darTZeel (458) gets out of the way of the music and does not add it's own character, has lower noise and is more extended and linear top and bottom, yet is liquid, nuanced and grain-less. the darts are capable of driving more full range speakers and when pushed it simply gets better. it is more complete.....but not quite as inherently sexy. but when optimized it has a greater upside. maybe the SET gets more nuance without so much effort. all the stars have to align to get that musical connection with the full range pathway.

what gets missed is that when you have a system with coherence and deep bass extension that the mid range gets a significant boost from true mid and deep bass linearity. vocals, horns, cellos, pianos etc. are sexy and tonally complete from the complete full range picture. an SET does it differently. but both do it.

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

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.

 

[SCAudiophile]

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.

Not to derail the thread (send me a PM if that is better); when you are talking about SET amps in your setup, are you referring to the Wall Audio M50s or your other SETs? What do you think of the M50s? Also, what subwoofer(s) are you using today?

 

[morricab]

Not to derail the thread (send me a PM if that is better); when you are talking about SET amps in your setup, are you referring to the Wall Audio M50s or your other SETs? What do you think of the M50s? Also, what subwoofer(s) are you using today?

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.