"Plhart: I have a dedicated sound room that is 12x17x7'2". The room has 3" and 4" acoustic wedge foam completely covering the front wall. The ceiling and side walls are covered out 5', or in other words LEDE.”
1. Wedges which measure 3” and 4” high at their peak do not have anywhere near the effectiveness or solid masses of 3” or 4” thick foam. The closer measure of their true effectiveness is by measuring the thickness of the wedges at the bottom of the wedge.
2. You do not mention how far out into the room your speakers are placed or your listening position but assuming that you’re using “classic optimized stereo” positioning I’m guessing your speakers’ front plane is about at the 5’ mark where you’re ending your room treatment. Thus, for all the damping behind the speakers you may still not be attenuating the first reflections from the sidewalls floor or ceiling.
3. The LEDE room was originally intended as a stereo listening optimization technique but implicit in the LEDE’s optimization was controlling at least to some degree the numerous (axial) first reflections which it appears your set-up might not be doing on the sidewalls because you do not have main reflection points covered (ususally halfway) between your speakers and your listening position. Your’s would appear to be slightly less than 1/3rd coverage so I would suggest, again not knowing the exact speaker and listening positions that a simple rearrangement of your already purchased foampanels to cover all first axial reflections and the echo slap from the rear-center of the room could increase vocal intelligibility.
“The ceiling is a triple layer: 1. soundboard, then resilient channel holding controlled density sheetrock which is covered with acoustic tile. The floor is concrete slab with a heavy pad under carpeting.”
1. I don’t know what “controlled density" sheetrock is. I would only say that standard sheetrock which is basically of a poured plaster-like composition could also be called “controlled density”. The 1” soundboard on the ceiling will give you attenuation down to 1000Hz. So along with the “heavy pad” (wool or felt I presume) undercarpet these two absorption elements are contributing far mor percentage-wise to mid and high frequency absorption than the foam you have behind your speakers.
2. The bad rap with resilient channel (or “Z” channel as it is sometimes known is that most installations use even increments of spacing of the channel so the end result can be a very specific one or two frequencies usually below 100Hz which have a huge suck-out, thus making the room mode frequency range below 150Hz harder to equalize.
There are large bass traps in each corner and one extra in the middle of a side wall.
1. You do not give details on your traps so I cannot comment as to their probable effectiveness.
“The reason I am telling you this is so you have an idea of where I'm coming from. After tuning my very tunable VMPS speakers and getting the best position I could I find an equalizer still helps alot. It helps well above 250hz”
Although you’ve done a good job at attenuating the ceiling and floor reflections above 1000Hz or so there may still be very strong sidewall reflections which should now be more noticeable. That you can still notice the equalizer “helping a lot” can mean any of several things from the speakers not being flat reproducers in an anechoic environment in the first place to the more likely scenario that psychoacoustically it "sounds better" to you. And that really is all that matters.
”Trying to do with treatment what can be done with a sound processor is much more work than it needs to be and possibly more expensive. Therefore in my experience I'm forced to disagree with that thinking. I fully encourage people to try an equalizer. This should be done with the help of a test cd and a SPL meter, then of course to taste. The gain in sound quality is very worthwhile.”
Again, when you use a sound processor(with mic at the listening position) and you have not attended to the first sidewall reflections (and the echo slap from the rear wall) you are reading a great % of reflected energy and the direct energy from the speakers being summed together at the same time. So the EQ is working off of all information, delayed and direct, to try to “equalize”. You may be going further away from the linear on-axis and polar response ideal. Though again. Whatever floats your boat.
“ Like REG in Absolute Sound said: "Everybody in the consumer world has got it in his head that equalization adds phase shift, but of course it's really just the other way around. If you equalize the resonances out of a room the correct timing is restored." I will add that if you just take it either part or most of the way there that the improvement is quite worthwhile, to say the least.”
The bass frequencies below 150Hz, combined with the room effectively constitute a minimum phase system. If you can measure the room modes with 1/12 or better yet 1/20 octave precision and apply an inverse signal of exact height, width and frequency with a minimum phase device such as a parametic equalizer then the signal remains minimum phase. With full range speakers having woofers operating above and below that 150Hz range this doesn’t work because the interrelationship of the reverberation within the room changes as the frequencies increase.
