The test is CD based. That might be why.
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If this had any basis in reality, at all, speaker testing would be based on power vs. frequency. It isn’t. It is input voltage vs. frequency. Hmm. So you’re saying that a solid state amp can make as much power into a 30 ohm load as it can an 8 ohm load? And that with an ESL, the impedance curve is also a graph of its efficiency? I think we both know that neither is the case. SoundStage Magazine online has a review for the Atma-Sphere MA-1 Mk II.2 mono-blocks: The conclusion here is false; starting with ’with an excellent...’. The reason is that the MA-1 is a zero feedback device and is not a ’typical’ tube amp! If it had enough feedback (about 20db), it would behave as a voltage source and the test as shown would have measured flat. Also, this does not debunk the idea that a solid state amp will have troubles driving higher impedances. IOW, this is typical behavior of a **zero feedback** tube amp and not that of one employing feedback. So one has to ask why we would make an amplifier that has no feedback with resulting (apparent) FR errors, and the answer is that feedback adds higher ordered harmonic content that is easily detected by the human ear. We get low distortion without feedback (assuming that the test equipment does not ground one of the speaker terminals which can result in a bogus test) so then we are simply looking to find a speaker with which the amp will have flat response. Dr. Herbert Melcher, a neuro-scientist, has shown that the brain has a variety of tipping points. One of them appears to be that the ear/brain system will favor distortions interpreted as tonality over actual FR errors. So our approach is that if we can minimize the tonalities generated by the amp due to distortions, it can often appear to be more neutral than amps that measure much flatter on a given speaker on the bench.
We don’t try to give this impression! Erik (@erik_squires what is the brand of speaker you make?) is correct otherwise; most speakers are Voltage Paradigm devices. But not **all**; some are based on the prior Power Paradigm, as are zero feedback tube amplifiers (see link at the end of this post). If you’ve ever seen an older speaker with midrange and tweeter level controls, the reason they are there is not to adjust the speaker to the room but instead to match to the voltage response of the amplifier. These controls are not seen on Voltage Paradigm loudspeakers. Long ago we discovered that our amps sounded much better without feedback (smoother, more detailed, wider and deeper soundstage). It took a while to find out why! In the meantime though, we have always been very careful to ascertain which speakers would be a good match. This is important (at least to us), because this is the dividing line between what makes for a good hifi as opposed to what sounds like real music. That we are still around 40 years later suggests that there are good number of speakers that work with our amps. This is not to say that a Voltage Paradigm speaker can’t sound like real music; it is saying that if that speaker won’t have flat response without an amplifier employing a lot of feedback, then that speaker will never sound like real music on account of the amp. The **reason** is that loop negative feedback ignores a fundamental law of human hearing which is how we detect sound pressure. Rather than detecting the volume of a fundamental tone, our brains sort out sound pressure by detecting the strength of higher ordered harmonics associated with that sound (which are increased if feedback is employed, although in ’trace’ amounts, but our ears are literally tuned to detect those traces). If the harmonics are louder than they should be, then the fundamental(s) will be interpreted to be louder too. That would not be such a bad thing but the extra harmonics are also interpreted as brightness and hardness by the ear /brain system and that is why they impart the sound of a hifi instead of real music. BTW, this is easy to prove using simple test equipment. So we abandoned feedback and as a result the Voltage Paradigm as it has that fundamental flaw (although otherwise works great) and went back to the Power Paradigm (which was what was around prior). We’re not the only ones; SETs, horns, ESLs and a number of other speakers (which are admittedly limited to high end audio) are also built around Power Paradigm principles; we’re not the first or only ones that have sorted out that loop feedback isn’t perfect (see the writings of Norman Crowhurst; these problems have been known for over 50 years). The Soundstage test assumes that all amps are based on the Voltage Paradigm and the simple fact is they are not. If your amp’s impedance is high enough, it will become an ideal "current source" where the output current has nothing to do with the load, and therefore the voltage at the speaker will vary wildly with the speker’s impedance. Atma-sphere has a unique perspective on this issue, and seems to constantly be suggesting a current source is ideal. He stands very much alone in this area.This statement is mostly false. Why: We don’t hold this viewpoint, and Also a current source amp will have an output that in fact varies according to the load, but in an inverse way. Nelson Pass has built some amps based on this principle, but he never made any such amp for production, and I’m not aware of anyone who has. Current Source amps IOW never developed any sort of following. Put another way, if the impedance of the amp is low, it is likely to act as a voltage source. If the output impedance is medium (a few ohms, like SETs and our amps) then the amp will act as a Power source (constant power into all impedances rather than constant voltage). If the output impedance of the amp is very high, multiples of the speaker impedance, then it will be a current source. That being said, the question of sound quality and amp/speaker matching is purely subjective, and you should listen for yourself. I’m pretty sure my favorite tube amps of all time, the CJ Premiere 8s were quite high in output impedance, but I’m not going to try to sell new physics to convince anyone to buy them.Listening of course is what this is all about :) The cj has a fairly low output impedance owing to the loop feedback employed and behaves as a voltage source. It has a classic tube sound as you might encounter with any excellent hifi. For more on the Voltage and Power Paradigms see http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php |
@atmasphere I am saying your entire argument is bunk, because the ideal audio amplifier is a voltage source, not a current source. In essence you are also arguing for amplifiers of TINY damping factor being ideal. Not supported by anyone but you. In fact, the amplifier I quoted, has a damping factor of around 0.8. That's about 400x worse than even a mediocre solid state amps. Complementing the amplifier design, speakers are measured by the output vs. frequency based on constant input voltage. For your theory to be at all accurate, speakers would have to have flat power efficiency (input vs. output) and ....they don't! The power efficiency of almost all multi-way speakers varies tremendously based on frequency. The LAST thing on earth you want is a constant current amplifier, unless you want your output to look like your impedance curve. If you are right, then man, 10 Ohms is too low. You should make amps with 30 or 50 ohms at the output, you would get even more ideal current sources! << hahahahah >> You know, it is a real shame that you take this tack, because I actually think you have a lot of fans, and built good products, but I've gotten really tired of you constantly hammering the superiority of high output impedance amps as a feature based on false and misleading (that's your own phrase) statements you repeat over and over again. Best, E |
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