This may be a somewhat uninformed (dangerous) comment, but to make sure I understand the above:
Trinnov seems to be doing something to improve reflection issues?
And in this example Audyssey, almost nothing?
So I am fighting with Bass Trap issues as well, my bass trap testing isn't "fixing" what I think is a reflection problem.
I was reading somewhere (cant remember where) that perhaps 4 subs (2 front/2 year) adjusted/tuned (not sure what this means) the right way would "block" the oncoming bass waves and do a MUCH BETTER job than bass traps. Although many can't do this, if you can any idea what this is all about ?
Some people maintain that Audyssey does nothing in the time domain other than as a byproduct of what it does in the frequency domain. My own measurements also seem to confirm this.
You and me both. I have reflections which show up in the ETC for which there seems to be no possible cause. I have come to the conclusion that they might emanate from the speaker cabinet itself, and possibly from the mic stand. They are not all that serious and don't appear to cause me any audible issues so I have (for now at least) stopped chasing them. I also have a reflection off the PJ. There is nothing that can be done about that - the PJ cannot be moved for obvious reasons and nor can it be swathed in absorption materials for equally obvious reasons. I have become more philosophical as a result :)
The general "best practice" we have been working with is to reduce all reflections to -20dB within the first 20ms. Managing reflections is not a simple topic, and there are quite a few opinions expressed by valuable contributors to this thread, so perhaps we will hear some other inputs.
As far as finding the reflections, the "blocking method" seems to be the most reliable. For this, you will need a reasonably large non-reflective "blocking tool". For example, I use a leftover 2'x4' bass trap, but a large piece of pink fluffy may work equally well. I start by placing the tool immediately to the right, left, top, or bottom of the speaker. This narrows the general direction of the reflection (e.g. east, west, up or down). Then I follow that general direction, placing the tool at various spots and taking measurements. This approach will normally isolate a reflection that has a single path. Of course, the ETC graph and the string method will also give you a general distance that the reflection is travelling, which is also useful in the hunt.
Reflections off multiple surfaces are more difficult to isolate. For example, I had a significant reflection off the ceiling, then onto the back wall, and finally down to the MLP. Treatments on both the ceiling and back wall were required.
Early reflections are especially tricky to isolate. They can be caused by the speaker cabinet, SBIR, the mic stand, the MLP chair, etc. Again, persistent use of the blocking technique should isolate the cause.
And also remember to try filtered IR response measurements, as per Jim's recommendations. IIUC, reflections at higher frequencies that are not present at lower frequencies are likely caused by smaller surfaces. A very narrow reflective surface can be causing a reflection. For example, the hard frame around a bass trap could be the source of a high-frequency reflection.
And then, of course, there are the ceiling fan reflections, mitigated only by installing a Big Ass Fan.
Mmmmm....ok, so I have MASSIVE custom traps in my two front corners...put in place via a home theater (well respected) consultant. I honestly don't know if they are helping or hurting.
What if I added a 4th sub....anyone know if my readings (or my dreams) have any validity ? Meaning the opposing subs tuned to defeat the reflections, etc.