This seems the equivalent to a definition stating that anything not signal is noise and whereupon distortion perception is defined as being the point of audibility. Fair enough.
Motional feedback should be a more widespread solution if people would really like linear systems.... .I had a sigma drive system and it made some fairly low quality speakers sound like a million buck speaker system, but that tight control was so linear that i could hear the stupid music behind it and let's face it like men: we actually don't like a lot of the music we listen unless we do it on the "right setup "
Where they Philips drivers? Motional feedback is interesting, having built numerous subs, including a stereo pair using 12" drivers and another pair using 6- 8" drivers per side. The vibrato the 12's produced from an organ pedal (from the classic E. Power Biggs album) at the low end was phenomenal. Unfortunately it wasn't possible in my own listening room, rather in someone elses large loft. Although there is a drastic audible difference between feedback and non-feedback speakers the room resonances created from such extension often destroyed the advantages, hence parametric notch filters were used to diminish those resonances.
Back to the point of the thread, the feedback mechanism is one of comparing the input signal to that of the voltage fed back from the accelerometer attached to the cone. Linearity occurs when the voltage signal source is proportional to the acceleration of the speaker, concluding that from the speakers perspective the input signals are acceleration waveforms. Hence the clipping of an amplifier is different from that of a speaker hitting some displacement stopping mechanism. In other words an amplifier being clipping generates the equivalent of some fixed force on a voice coil, that for a speaker to respond requires that the speaker continue to accelerate simply from Force = Mass x Acceleration. Ultimately non-linear distortions can be generated as dominantly irreconcilable in different domains.
As you mention power, it lends me to think about the high power often used (ok, I know the... What?! Quadratic for doubling power) in here... Oh, yes, it's related to the listening space dimensions, but also to something you said earlier (... Directed to OP...)
Which is also the effect of masking, as a feeling of sound over sound.
So power in a room might be over - requested only for sub/multi subs, the limit to be determined in the auditiory space, and the result cuts many zeroes from the 1000-2000 W we may find to read about... Indeed the SE crowd... No crossover.. (well, indeed the need for high power hasn't any place In a well done 3 way for home reproduction, let's call it an ideal speaker, where the room and how the speakers... Funny, the corrector gave me 'systems' - are placed...)
So little power, little troubles (every piece of the 'system' must perform as 'ideal' but real world speculation suggests that the trouble must be minimized to fractions and fractions which is achieved by utilizing state of the art technology and techniques) and relativity in various magnitudes, and than correct interpretation of how the others give name to the different attributes are found and related (after being processed by the brain, in poor words...) in sound, so masking...
Class A amplifier has no crossover distortion. It is mean the harmonic profile of the distortion is always close to monotonic. Human perception in not only about THD and harmonic profile of the distortion. There are many distortion that not seen with only measure the THD, like thermal distortion. Dr. Arto Kolinummi called it dynamic distortion. You should compare same amplifier with different biased. If you trained you can know the sound different blindly. It is not which more accurate, but which more you preferred.
If you can make classA amp with 0.001% distortion at all audio frequency and all level below clipping, why do you make class A amp with 0.1% distortion? Maybe you make low cost amp or you can not design such amplifier.
I made two amplifier with same topology, one in classAB and one in classA. Both have different strength and weakness. Person who listening those percept that the classAB has better in high frequency and the classA has better in low and mid frequency. I still investigate why they precepted like that.
Because i am not as smart as you. Only you know upfront how the recording will sound before you even buy it.
I do not design, i am diy builder. I build and i listen.
Maybe you forgot to send memo to Mr. Nelson Pass, who keeps designing those wonderful sounding classA amplifiers with distortion 0.1% and more.
Ha! I was just discussing that phenomenon in another thread. That a subwoofer can re-absorb energy from the room, but only if it's designed and powered in such a way that it's allowed to do that job.
I stumbled upon it while experimentally decreasing the damping factor for the woofers in my system, and found that the notch filters for room resonances had to be adjusted for less dB and Q correction.
The amplifier clipping is almost the same thing as crossover region just that it happens when the signal slew rate is at its minimum, while the speaker tension is highest so the speaker membrane will not hit its maximum peak nor the accelerometer will feel any big difference in acceleration so its information should be easy to correct in time with the information from a clipping detector...never studied that philips circuit though...I only had one sigma drive amplifier which derived its feedback electrically.
A hifidelity amp is an amp that has no audible difference between input and output.
An effect box has audible difference between input and output.
You posted some graphs to make a point.
But what do these graphs actualy mean?
By that I mean, what does the horizontal part of the graph mean, what does the vertical part mean, and what does the actual curve mean.
Of cause, what really matters is, where are the peer reviewed scientific listening tests, that show humans can hear 2% of non linear distortion added to normal music?
I haven't seen any, but I'm not an expert.
With another amplifier, right? And it can have 2% distortion, so easy.
In fact Edison settled the matter long ago, you can't hear the difference.
https://blogs.loc.gov/now-see-hear/2015/05/is-it-live-or-is-it-edison/
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Exactly the same as how those graphs you posted were being created, but now with a subjective measurements (using your ears).
Iow you compare the input signal to the output signal and try to find out if there's an audible difference.
This is how it goes: input signal through DUT. Output of DUT level matched to input signal and and compare with an ABX test.
It's not rocket science.
It's the percentage part that is confusing to some.
It doesn't mean that the actual level of the artefacts is increasing, as you claimed.
So you already have a tiny signal level, that by itself is difficult to hear (masking is a real thing) and people claim that they can hear the artefacts produced.
I don't thing anyone can hear ants walk, in normal circumstances.
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It being understood that the sound depends on the entire listening chain, I add a few notes based on my experience in measuring and listening to different preamps, solid state and tube, generally in class A.
I am not saying anything new by stating that what can have an effect on the perceived sound is not the absolute value of THD, but the relationship between the different harmonics that contribute to its determination. In order to better understand "how it sounds" a preamp in a "black box" approach, it is important to measure the trend of the different harmonics both as a function of frequency and the level of the input signal.
From the correlation of the measurements of dozens of preamps and listening tests of different people on different systems, those that were on average more pleasant to listen to have the following characteristics:
- Type of harmonic distortion (HD): mainly second and third harmonic; very small (< -100dB) and in limited numbers those of higher order.
- Frequency trend: constant, with very limited increases (few dB) in high frequency on low order harmonics.
- Trend for signal level: similar to the curve in step 2 shifted downwards by 6dB for each halving of the input level.
For example, this is the HD curve as a function of frequency on the first orders of a tube preamp (with 6SN7), judged to be well sounding. Input is at 1Vrms input; output at 5Vrms (14dB Gain). The THD curve, not plotted, practically coincides with that of the second harmonic. The peaks on the highest order harmonics in the high frequency end in the ultrasonic band and are not relevant.
While the THD curves (with the contribution of the first 4 harmonics) as a function of the level, from 1.4Vrms to 0.125Vrms in steps of 3dB of the input signal, are the following:
For comparison, this is the curve of a solid state (transistor) preamp, with volume control on output (see here for more details) which behaves a little less well for the aspects indicated. Always 1Vrms in input and 14dB Gain.
For the THD curves as a function of the level, from 2Vrms to 0.25Vrms with steps of 6dB of the input signal, we have:
Other similar experiences?
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