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 |
http://www.cco.caltech.edu/~boyk/spectra/spectra.htm |
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. |
. 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. . |
Oohashi's findings have never been confirmed by another
laboratory and the papers are open to criticism of their
procedures and findings. |
