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About DrSK

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  1. The measurements I was referring to aren't about room modes and transfer functions. This doesn't relate to much other than at low frequency. These messuments are about the other factors I mentioned which relate to the time delays and content of early order reflections before the reflected field has built enough to become the reverberent field. I don't think this would help as most locations in the room are redundant and have no use. For the stuff we are talking about it is the state of the direct signal presented to the listener in the stereo sweet spot that is of importance.
  2. I wouldn't over sample the CD. I'd sample the DAC output at the same time as the amp and use that as the reference for the difference measurement. That way the DAC is taken out of it and the samples will coincide for the difference calc.
  3. Room measurement isn't my strong point yet. Acoustics is a big field with many sub-disciplines. Talking to those that design performance spaces such as concert halls etc, they are using firstly impulse response so they can seperately measure the time delays and frequency content of direct signal and all individual reflections of the impulse as each one arrives. From this they can tune for timbre, spaciousness, presence, image width etc. In stereo and home scale, I don't know anyone who works in this space as there isn't a market to pay the $10s of thousands required t
  4. Just noting there is a difference between sample rates that are audible and Nyquist limitd to sample rates that generate reliable data for signal analysis. No one uses Nyquist limits to analyse signals unless it has a multiplier in front of it. Eg I've dealt with 30Hz signals that need 48kHz sampling to analyse them.
  5. Yeah, that's me. Hate not knowing if there is something I've missed when capturing data so grab everything given storage is cheap. And that way I don't waste time analysing data with flaws in it. Probably, I just prefer to make sure data is robust to rule everything else out. It's the playback of the measured sample that concerns me most on this. Given that amplifer 1 struggled in the first place. That was why I headed to difference signals and then making sure sources of error from sampling were accounted for.
  6. Yes. This is the sort of thing I've had in mind. I've been frustrated by the witch craft, marketing and subjective reviews of stuff for years. You would want to oversample the signal by at least 10 times Nyquist from experience. Nyquist limits are rather rubbish for signal analysis as you there is nothing much left to analyse, particularly at higher frequency. Nyquist limits require interpolation of a waveform with only 2 points at the limit, so you have nothing left to analyse of your test subject. It is just an interpolation when you try and view it (eg v
  7. Like I said, it's apparent on some material and not others. And it will also depend on the transparency downstream.
  8. The discussion is also directly relevant to DACs. Eg check out the following chip which has configurable filtering which changes the forward presentation with the most forward being the cleanest signal. AK4495EQ The forwardness changes are audible most on close mic stuff as recorded transient effects from the room etc seem to dominate for recordings further away.
  9. I disagree with you. There is no other explanation about how one amp is flat and another has depth. Our auditory system is highly refined and evolved to process reality. If it is fed something resembling reality, the stage will pop into the intended width and depth. Here is a good starting point. And from this you can work up to stereo. https://www.booktopia.com.au/psychoacoustics-facts-and-models-with-cdrom-hugo-fastl/book/9783540231592.html?source=pla&gclid=CjwKCAiAzNj9BRBDEiwAPsL0dx79hJDMdLBXHr3XC_-No11lJmkaUpbc9KVh6rRla3T1ZyllVpV0mBoCBtsQAvD_BwE
  10. Of course not published, as hifi research work is complex and time consuming and doesn't pay the bills. Hifi seems like money can only be made by selling product. But the differences are not subtle. I guess the point is it is very well established how humans perceive sound in 3d and judge distance to objects by the physics of the propagation paths between a source and the ear drum. Many people on this forum don't understand how this works. I gave some information about human perception as some explanation of why two amps can sound so different, t
  11. If you're referring to me this is coming from what I've read about studio mixing of sound from different distances. This ties in with 20 years on and off working in psychoacoustics and published at peer reviewed international conferences. Which all relates exactly to 20 years of acoustic measurement over distances and the physics of modelling acoustic propagation. Design of performance spaces. Processing audio signals to identify source location in a room by measurement of reflections vs initial signal. A patent in directional mo
  12. I'm a firm believer the current measurements aren't up to it. Yeah, I was waiting for someone to mention the valve amp side of things. The grunt side of 1 makes sense as you often hear this has downside. Given our brains will grab at anything to try and build a proper picture. There is a chance any artifacts from the valve may still follow the desirable rules, and create fake info that is beneficial on balance. Eg if the attack is fine, the amp doesn't get grainy and destroy info, and any harmonics create fake info on the right frequency range that builds on what we n
  13. I'm not sure yet! Assuming the headphones etc are up to it the content shouldn't change. The issue is that the speakers are physically in front of us which places the sources in that direction. So some of our physical directivity related aspects remain, eg our outer ears etc. Headphones don't do this and place the sound in the middle of our head and they bypass the effects of our outer ear etc. I'd expect the effect to be reduced with headphones. Unless additional processing is employed. To put the whole sound stage out in front to begin with
  14. For the amp to be projecting the voice forward, it can only be doing this by giving our auditory system the information needed for us to perceive this as so. The science behind spatial perception is well established and used in recording and mixing. Both in left and right, up and down and distance. This is achieved by altering spectral content and attack and decay characteristics. Spectral content and the phase response relates to attack. And decay relates to any transients from recorded or introduced reflections or oscillations. Now attack dro
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