Hi Mitch4T:
I recently upgraded to some of the new Reference 3A Episodes, which have a "supertweeter" that covers from 20khz to the upper 40khz area. After some experimenting with blocking off the supertweeter, I have noticed that it does certainly add some positive effects to my music, but not on all of the recordings I listen to. What they add does not seem to be anything that is part of the texture of the music itself, but to the ambience of the soundstage being created in my room. Some may call this "air" to the soundstage. It is a subtle improvement at best, but it does make a difference. It seems that some of this upper frequency information is deleted or missing in about half of my CD collection. |
Bifwynne, no speaker has anything like what I would call a linear curve. If the bumps aren't too bad often that's pretty good :) |
The less phase shift, the better the imaging. Tonality will also improve since phase shift causes improper summing of harmonics. I'm not sure about speakers but amplifier has at least 45 degree phase shift at -3dB frequency limit. My -3dB@60kHz amplifier has 20 degree phase shift at 20kHz. Newest amplifiers from Jeff Rowland have 350kHz bandwidth. |
The SACD improvement over CD on most recordings i feel relates to improved digital processing and frequency response, that I easily hear on my Magnepan ribbon tweeters which go to 40 kHz. On phono, MC improvement over MM, more clearly relates to FR. IMO the difference comes down to more accurate complex harmonic structure in the audible higher frequencies under 20 kHz. Most all audiophiles prefer SACD over CD, and MC over MM. |
12-27-12: Mitch4t: Kr4, do you think there's any value or advantage for a speaker to be able go above 20khz? I think that it is necessary that speaker response extend at least to 20kHz and have a smooth, well-behaved rolloff above. 12-27-12: Don_c55: Kr4
Do you hear any difference between a CD and SACD? I do but I doubt that it has to do with FR. For example, at an audio show, I was able to pick out the addition of an ultra-tweeter that was effective only above 20kHz even though I have audiograms which show that my hearing at 20kHz is more than 20dB from reference. |
Kr4
Do you hear any difference between a CD and SACD? |
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Kr4, do you think there's any value or advantage for a speaker to be able go above 20khz?
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Oohashi's findings have never been confirmed by another
laboratory and the papers are open to criticism of their
procedures and findings. |
. X. Significance of the results
Given the existence of musical-instrument energy above 20 kilohertz, it is natural to ask whether the energy matters to human perception or music recording. The common view is that energy above 20 kHz does not matter, but AES preprint 3207 by Oohashi et al. claims that reproduced sound above 26 kHz "induces activation of alpha-EEG (electroencephalogram) rhythms that persist in the absence of high frequency stimulation, and can affect perception of sound quality." [4]
Oohashi and his colleagues recorded gamelan to a bandwidth of 60 kHz, and played back the recording to listeners through a speaker system with an extra tweeter for the range above 26 kHz. This tweeter was driven by its own amplifier, and the 26 kHz electronic crossover before the amplifier used steep filters. The experimenters found that the listeners' EEGs and their subjective ratings of the sound quality were affected by whether this "ultra-tweeter" was on or off, even though the listeners explicitly denied that the reproduced sound was affected by the ultra-tweeter, and also denied, when presented with the ultrasonics alone, that any sound at all was being played. Don, thanks for the great reference. . |
Don_c55 - thanks for the reference. I continue to tell people that the human brain and nervous system are far more sensitive than is generally believed. Oohashi's result seem to confirm that. It was particular interesting that subjects said they heard nothing, yet there was brain activity associated with sound great than 20 KHz. Something is clearly going on above 20 KHz even if we can not "hear" it in the traditional sense. One question is whether modern electronics and speakers are taping into that high frequency information or whether somthing like Atmasphere's explanation is what is happening.
The more we know, the more we don't know. |
http://www.cco.caltech.edu/~boyk/spectra/spectra.htm |
Ralph, let me see if I understand what you're saying. A speaker which has a flat FR out to 45K Hz will have less (?) phase shift in the audio range than speakers with a lower frequency bandwidth. This is a good thing.
If I've got that right, I will return to an old saw -- I've seen the impedance and phase angle plots for my speakers. The graphs look like a roller coaster. Even still, the speaker sound fine and imaging is very good. Can you clarify what I think I understand? Thanks |
The issue is phase shift. That is why bandwidth is nice.
The less phase shift, the better the imaging.
Phase shift is caused by group delays that in turn are caused by a rolloff in the equipment. They can have artifacts to 10x higher than the low frequency rolloff, and 10X lower than the high frequency rolloff.
This is less of a problem in speakers than electronics, but its still an issue. |
My dog sometimes complains about it !!!! |
No. It is a big but inaudible difference. |
