I don't necessarily need the modes to not be excited, audyssey will take care of that, i just want a more even bass response. I might try moving it out from the wall, though my wife will probably insist i move it back lol.
The one place it might be able to sit out from the wall would be at the front wall at the midpoint, about 3 1/2 feet into the room. Where would an ideal spot be?
Also the center measures faily flat in the bass. No point crossing it higher. I know many here are rigidly stuck on an 80hz xover point but I've never had good blending with an xover greater than 60hz. In my experience the lower the xover the better the sub integrates, considering my front l/r are easily capable of a full 105dB @40hz, and the center and surrounds are capable of 105dB @50hz, there's no reason to cross them over higher if i can acheive a flat response via EQ across each channel.
Also, a center speaker reproduces far more than just dialog. Over 60 percent of the effects anchored to the screen are mixed into the center, and i almost always listen to music upmixed with DSU or other upmixing algorithms, with no center spread. I personally find a real center beats a phantom center no matter the content, and most non audio people ive demoed it to agree a hard center for music sounds more natural.
As for matching excursion, lets assume a single speaker is capable of 105dB at 30hz without distortion, each channel adds an additional 3dB, which gives a combined headroom of 117dB, plenty to handle both the LFE and the regular bass.
With LFE+main, the bass at and below the xover is attentuated in the speakers 3dB, and in the sub 3dB, in order to properly match, this affords greater headroom in the speakers as well.
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Are you treating the walls to absorb the first reflections?
Your first comment doesn't work. You're familiar with sympathetic vibrations, right? It takes little energy to get them going and it's hard to stop them- this is the same thing- the air really wants to vibrate at these frequencies in that room because of the dimensions. It's no different from a vibrating string- the mass, length and tension determine the pitch of the fundamental and the distance between parallel surfaces determines the resonant frequency.
Audyssey does NOT take care of modes in a way that allows for the best sound. It can only subtract from the output at those peaks and anything else it does, which might include changing the distance setting, will cause other issues.
The ideal spots for speakers tend to be away from the center of walls or the floor- that provides symmetrical stimulation and you don't want that.
The center is already crossed at what, 60Hz? The crossover slope isn't infinite, so you still get output at 50Hz and the other nearby mode, at 46.8Hz- that's close enough to cause this to become difficult to manage.
You can have a large number of small drivers producing 30Hz, but they'll never provide the same feeling you get from larger drivers at the same frequency unless the smaller ones have been grouped together. You need to think of a moving cone as the head of a piston.
I would stop thinking in terms of headroom and more about the dynamics of the air moving in the room. High SPL in a small room causes even more problems and if you're expecting Audyssey to dampen harmonic vibrations, you'll never cure this. The room needs to be somewhat inert- having specific frequencies that can be easily excited means they'll ring like a drum head if you don't dampen them. Equalization can't fix everything.
Blow across the mouth of a bottle- it really wants to produce one frequency and the only way the frequency can be changed is by changing the internal volume of the bottle as long as the velocity of the air doesn't change.
If you have/download a tone generator and do a frequency sweep between about 20Hz and 200Hz, without using your subs- look at an RTA screen while this is going through the problem frequencies and watch the amplitude increase, even if the output doesn't- THAT won't be solved with simple equalization. The relationship between the sound source and the reflective/absorptive surfaces is where the solution lies, as well as the room's dimensions. That's the reason it's necessary to determine the percentage of treated surfaces when treating a room.
