I think Audyssey is only good for correcting really bad resonances, ie. severe speaker flaws. If your speakers are good, Audyssey doesn't have much to do. There is no sense in fooling around with reflected sounds as well. Audyssey is a band-aid for bad speakers. I think it is useful below the transition frequency, but only for a single listening position, and only for cutting peaks, but when it tries to boost nulls, that can do more harm that good. I don't use Audyssey or anything like it.
TLS Guy, you ought to look at Dirac Live. It is room correction that is more interested in correcting for time-related problems and so it really goes to work on the impulse response, as opposed to Audyssey which only concerns itself with the frequency domain. It reduces reflections and places more emphasis on direct sound. In cleaning up the impulse response, that consequently causes improvements in the frequency response. From what little I know of Trinnov is that it acts similarly as well. Here are some white papers on Dirac:
here and
here
Thank you for that post and those links.
I readily admit I had not looked closely at Dirac. As you know I think we have a long way to go before any of these programs should even be on offer. The downsides are just too great.
I did find the article interesting.
The real guts of the issue is on pages 4 and 5. So I'm going to paste them here.
{This has some important implications for sound equalization. When we read our magnitude response estimates, we use a very simple estimate of the perceived spectrum, completely suppressing the concept of time. For example, take a minimum-phase impulse response and reverse it. The former starts at time zero and decays with some time constant until it dies out; the latter has instead a substantial pre-ringing but no post-ringing. Now all research that has been carried out on human perception of transients say that pre-echoes and post-echoes sound completely different to us. Yet, the magnitude responses are identical. Of course, this is also manifested if we say something and then play it back in reverse. Both samples have the same Fourier magnitude responses. This illustrates that phase responses, or impulse responses, do affect the perception of sound, even for a monaural source. There is obviously some threshold of how phase sensitive we are, but the literature on this matter (which is extensive, starting from the 1930’s) has concluded that this threshold, or integration time-constant, is adaptive and varies with what we listen to. What we can say for sure is that we do hear absolute phase but that the higher the frequencies the less sensitive we are (obviously, as the wavelengths become very short and the physics of wave propagation dictates that very little relevant information can be transmitted acoustically at high frequencies due to the chaotic behavior of high-frequency acoustic transfer functions). This implies that a good equalizer needs to consider also phase, not just magnitude. An example will show this point more clearly. Consider a loudspeaker standing in a room. Mr A measures impulse responses in a certain listening volume and finds to his dismay that the magnitude response has a substantial broad dip at some rather low frequency, say 300 Hz, in all positions. He calibrates a peak filter and fills up the hole in the magnitude response, which is then confirmed by measurements. Enter Mr B. Mr B is a musician and he listens to the equalized system. “It sounds horrible! What have you done to the system!? It sounds all swollen and strange!” Mr A becomes nervous, as Mr B is an important customer, and calls his trusted friend Mr C. Mr C answers: “Ah, yes of course. The dip was really due to reflections. You should never boost any dip, because they are typically due to reflections.” So Mr A removes his equalizer filter and lets Mr B listen again. Mr B, however, is still not happy. “It is better, but it’s not good. There is something hollow about the sound.” At this time Mrs D enters the conversation. She’s been listening, sitting quietly in a corner of the room, and says: “Mr A was wrong because he forgot about the time domain. Looking only at the magnitude of the Fourier transform and interpreting it as strongly related to our concept of frequencies, he thought that he could boost that region and obtain better sound. The problem is that he uses minimum-phase filters and consequently adds energy at that frequency early in time. But if we only look at the direct wave there is no hole to be filled in the frequency response. The hole never exists if we look at a short window at any time.” Mr B frowns: “So Mr C was right to say that we cannot do anything about it. But if that’s the case, why do I still hear a strange sounding oboe on my recording?” Mrs D looks sternly at him: ”Mr C was wrong too. The problem is due to the time domain properties; the reflection causes the problem and it can only be corrected for by a time-domain approach. If we design a filter that reduces the reflection, you will end up with the interesting result that the hole will be gone and the oboe will sound more natural.” “But,” Mrs D adds, “don’t take this example as evidence that you can always correct dips this way! In this case it was possible, because all positions experienced the same problem.”}
Of interest is his view that time/phase matter. Also that individuals vary in their ability to be bothered by these aberrations. I agree that this detection is something that can be leaned over time. I know I am very sensitive to this issue. This is probably why I am highly adverse to most speakers with large driver to driver time shifts.
As you know I try and maximize acoustic response in crossover design and minimize the use of filters keeping electrical orders to the minimum to get a flat FR.
I put huge store in a speakers impulse response. As you know I demonstrated really superior impulse response in my speakers. That is why I included the impulse responses in my plots in this series. You may have noted that Audyssey disturbed the impulse response more than FR, which it also failed to improve. What is even more interesting is that the damage to the impulse response of the reflections is greater than the upset to the direct response.
As the author points out equalizing with one mic position might improve a sweet spot but downgrade the rest. That is basically why I did not do it. In this theater every seat is a good seat with slight increase in warmth in the rear because it is near the back wall.
I can't begin to tell how absolutely awful this system sounds with Audyssey engaged. I'm sure it is in large part due to deranged time/phase relationships. It exhibits all the bad effects the author points out.
Audyssey does its damage ahead of the processor, which is why it totally destroys the effects of multi channel listening, especially Dolby Plx2, which I like a lot. When engaged front row sounds like the orchestra seats and the back row the balcony.
I do think that the author has minimized some of his problems, especially ringing, and I would say even minimal pre ringing would negate a good result.
I don't think any of these programs are suitable for widespread application at present, if they ever will be.
I think this discussion I have generated is one we have needed for a long time. I think most members probably assume that Audyssey is improving their systems, should be part of the set up and used. In fact far more likely than not it is degrading their systems. Just the fact that it tries to correct nulls is reason enough that it should never have seen the light of day, and I eluded to that in my analysis.
A survey of who uses Audyssey would be a good start. Everybody who is using Audyssey should give their systems a prolonged listen without it.
