To SAM or not to SAM and DRC

[GuillaumeB]

Thanx Confused for testing and having the kind words.

Ok.
The most difficult thing in this test is the transparency of your system chain...I know, I know, everybody in this forum would claim his system for being very transparent   .
But may be there is a here and then of someones system resolution being a little bit better than the average   ...you know what I mean   .
For those having a 'highly' transparent system the effect the test discovers will be of a large amount, I promise. Saying that we did this test with 'highly' tuned rooms and systems here.

Does anybody take a thought discourse on the Bit-Perfection? Am I right that Bit-Perfection is out the window if the music signal is touched by e.g. SAM, etc.?

gui

I will bite the bullet on this one. 

I don't think that bit perfect is what really matters. The ideal would be a system that reproduces at the listening location as the output of the speakers the exact sound Field that the microphone was attempting to capture. 

Before continuing I would like to express a number of postulates that underpin my reasoning:

1) 24bits PCM is inducing a quantization noise that is well below the audibility threshold
2) The dominant effect of an ADC DAC chain is the low pass filter that is required to fulfill the Nyquist condition, and is way beyond the audibility and even most speakers capability if you take a 96kHz sampling rate, so not even speaking of 192. 

We can debate those statements, in which case the following will have to wait... 

So the notion of 'bit perfect' is only valid if the rest of the chain is perfect. If it is not, then it does not really matters whether you correct the defects in the digital domain, the analog domain or the accoustic domain. 

The only problem is that it is always a matter of compromise and cost. The acoustic correction of a room mode can be much more costly and requiring much more real estate than a digital correction.

The digital correction will have other compromises. The biggest is that to compensate cancellation you need a lot of power that can quickly reach the limits of the speakers, meaning that most of the time room correction will only allow you to play at a lower level than the same system would have been able to play with an accoustic treatment. 

An other consideration is that a phase shift is a phase shift and an attenuation is an attenuation and it does not matter if it is done in the digital, the analog or the acoustic domain. Similarly, if I can insert somewhere in the chain the exact inverse function the end result will be much more accurate, and it does not matter in which domain the correction is done. 
It happens that digital signal processing is the most cost effective way to achieve it. So yes the digital chain is no longer bit perfect but the overall chain becomes much closer to the identity function. 

One last consideration is that our brain has evolved to discover changes and patterns. That was a matter of survival, therefore the hardest situation for us is to listen to two identical things and find them identical. 

My post is probably way too long already but let's have the ball rolling. 

Jean-Marie

Great post Jean-Marie 

Guillaume