[Wayne A. Pflughaupt]

Here are those AVS graphs:

Before
before_wf.jpg

After
after_wf enahnced.JPG

I'm not sure that ringing is actually worse with the "after" graph.

Note the highlighted frequencies appear to be at ~120 Hz, ~60 Hz, and ~30 Hz. Most likely these are artifacts generated from some source other than the sound system: An air conditioner kicked in, someone turned on a washing machine or microwave oven, etc. (Note that 120 and 30 Hz are harmonic frequencies of 60-cycle noise.) You can tell it's not ringing because it's a steady-state, constant signal. Ringing from a resonating audio frequency isn't going to drone on and on forever, it's going to continually drop in level and eventually disappear - like everything else in the graph does.

Another problem with the graphs is that they show only a 30 dB window. Signal levels should be kept high for waterfall readings. Note in Ethan's graphs at the RealTraps link that its bass peak is 60 dB above the graph floor. When it comes to waterfalls, Ethan knows what he's doing, so follow his example!

Apparently even professional people who should know better have trouble analyzing waterfalls. Consider a couple from the DSPeaker site Bailman linked above:

p_d7fa838944.jpg

p_e0550e60df.jpg

You would think these folks should know what they're doing, but look at the lower graph: By the time they're done equalizing, the signal is a mere 20 dB above the graph floor.

And look at the graph's lower limit - 50 dB? What, is that for people who run box fans in their HT room? Raise your hand if the noise floor in your room is that high.

(I could comment further, but rather than sidetrack the thead you can see more that I recently presented on the subject of waterfalls here.)

I'm confident that Audyssey is a dandy product, and probably the little box from DSPeaker as well. It's a shame they label them as "time domain" products that improve sound by reducing ringing. They may do a little of that, but primarily they're improving sound by smoothing or flattening response - i.e., reducing peaks and valleys with counteracting filtering. That may or may not carry an improvement in the rate of signal decay (which must be shown if you want to claim an improvement in ringing, not merely a reduction in gain that makes a waterfall "look" better to the untrained eye). In fact, it can even make a waterfall look worse at some frequencies where boosts are enacted (again, to people who don't know how to properly read them). But IMO the improvement in sound ultimately comes from minimizing peaks and valleys, regardless of what happens to ringing. For instance, try applying equalization to your headphones, if they need it. If it makes them sound better, it was purely response smoothing - there was no ringing factor involved.

One thing that does trouble me with Audyssey is the way it appears to equalize every nook and cranny out of response (the orange line represents the equalization that will be employed):

The range between 1-3 kHz, for instance: While all those little up and down jags look bad, the truth is you really can't hear that. The ear does not hear the same way a mic "does." For instance, if you add a coffee table to your room you may see a change in a response reading, but everything sounds the same to you. So I'd be concerned that all that equalizing could degrade sound quality, but I'll leave that judgement to the folks who have actually used Audyssey.

Regards,
Wayne