Coffee Phil wrote: ↑
08 Aug 2019 19:26
Hi H. callahan,
Think about this for a moment: You state that it is not possible to cut a record with acoustic methods which is constant amplitude, then you admit that you are not sufficiently conversant in mathematics and physics which are the disciplines required to make such a statement.
You also suggest that some sort of "tuning" may have been used to reduce the modulation for bass and increase it for treble as an attempt to achieve some sort of RIAA curve. It is not likely the engineers at the time were thinking RIAA as it was adopted decades later. When electrical recording came out the need for EQ became apparent. The velocity responding cutters had to produce records which sounded correct on old players which were playing the acoustic records. The EQ made the records constant amplitude over much their range in an effort to be compatible with records cut with acoustic cutters. That suggests that acoustic records are more or less constant amplitude over much of their useful range. RIAA is constant amplitude from 50 to 500 Hz, then constant velocity from 500 Hz to 2120 Hz, returning to constant amplitude from 2120 Hz to the upper end of audibility. Those inflection points of coarse are the Bodie approximations. The actual slope transitions are more curved.
I may not be able to speak the mathematical/physical language, but this musn´t mean i´m wrong.
Are my explanations wrong? Is nature of sound constant amplitude?
I have been looking up my physics books for about an hour and was not able to find a formula which does express what i mean - so just for you i´ll make up a formula:
I don´t know if that is correct, maybe it also is A=V/2F or A=V/F^2, but i know that its accurate when i say nature of soundwaves is not constant amplitude.
I´m not saying that engineers of that time were thinking exactly
RIAA, but similar. As i said:
"It may be possible that they tried to tune the acoustic recording equipment into some sort of RIAA-EQ
, as reduced volume on bass was easier to cut and emphasised treble was desperately needed for higher frequencies not getting lost due to constant velocity, plating and pressing."
When electrical records came out there was no need for EQ for recording. They still could have cut the records with constant velocity with an electrical cutting head, but then the sound quality and FR would have equaled them acoustic recordings more or less.
introduce EQ on electrical recording to overcome
problems of constant velocity, so electrical recordings did have extended FR in comparison to acoustic records. If they needed EQ to adjust electrical recordings to the properties of acoustics, electrical recordings should not have greater FR than acoustics, but they do. A lot. Acoustics only have 3kHz at best
while electricals go up to 5kHz easily, and way beyond.
One more example, which regretfully isn´t in the mathematical/physical language:
Let´s say there is an acoustic guitar and the lowest note it can play was 100Hz. You plug the string to make it vibrate at 100Hz and a certain amplitude and you need some ammount of mechanical energy to do so.
Now you press the string down in the middle to create a 200Hz frequency when being plugged. When oscillating at 200Hz the string does have to move double as much per second, at double the speed at least - so if you want it to oscillacte at same amplitude as at 100Hz you´ll have to bring up double the mechanical energy at least, maybe even four times as much.
To make it oscillate with same amplitude at 400Hz you´ll need four times the mechanical energy at least, at 800Hz its 8 times at least, at 1600Hz its 16 times, at 3200Hz its 32 times and at 6400Hz it was 64 times at least
This would mean that playing a high note on an acoustic guitar would take the player 64 times the force at least
to play this high note at same volume, if nature of soundwaves was constant amplitude - which it is not.
Playing a high note having the same volume on a guitar does not take 64 times the force, but about the same.
Therefore i conclude that nature of soundwaves is not constant amplitude but velocity.
I know this is not mathematical/physical language, but please tell me whether i´m wrong or right with that statement.