Clueless--maybe one of the few times I've disagreed (but to a small degree). Here's the problem. You are right that it is a time delay thing--but it occurs because of too much energy reinforced in the room. We look at these with waterfall plots and evaluate it in a psycho acoustical approach. That approach takes into account the time delay (it's actually an integral function and works similarly to the human ear). This also coincides with the fact that we can not perceive phase shifts at low frequencies. I know that there are many papers written that say we can, but our tests as well as many others show that the human ear really can not determine these things at low frequency. So all you need to do is reduce the total energy at that frequency (but it must be nearly exactly tailored for the Q factor and amplitude). Room treatment does nothing for the null points, they still exist. You should not sit in a null point, nor you should you sit in a peak. This is why 1/3 or 1/5 spacing is generally used--you don't have that problem in general. 1/2 and 1/4 are the worst places to be (but we always sit in the middle of the room from left to right don't we). This is true no matter what room treatment is used (we are talking about low frequencies only) or equalization. What happens is there is too much energy that is re-enforced by the parallel walls. You need to decrease that to bring things back into balance. Yes, the nodes and peaks still exist, but are far less problematic as they are in balance with the other frequencies (which also have peaks and nulls in the room). What's really interesting is to look at the energy distribution as a result of all modes (tangential and oblique as well as axial). A lot of surprises happen. CARA lets you do this to some degree and it's pretty fun to take a long look at what happens.
As to boosting frequencies where there are nulls--bad idea. The nulls still exist. If they are caused by impedence mis match between amplifier and speaker--it's a worse idea and will likely drive the amplifier into overload. Fortunately, particularly at low frequencies, the human ear is very forgiving to small (meaning narrow band) drop outs (or troughs) in the frequency spectrum.
As to boosting frequencies where there are nulls--bad idea. The nulls still exist. If they are caused by impedence mis match between amplifier and speaker--it's a worse idea and will likely drive the amplifier into overload. Fortunately, particularly at low frequencies, the human ear is very forgiving to small (meaning narrow band) drop outs (or troughs) in the frequency spectrum.