Quote:
Originally Posted by
HDvids4all 
What you're doing is called "corner loading." By placing your sub in or near the corner of the room, you'll reinforce certain room modes, which can give the appearance of increased gain (volume). In my opinion, corner loading 2 subs for an HT that's primarily used for movies might not be the greatest idea.
Another option is to separate the 2 subs in different parts of the room. This will help even out LFE throughout the room so you don't have as many nulls, or dead zones in certain places. If you have multiple rows of seating, or even a wide row of seating in your HT, 2 subs will give a much better listening experience for everyone.
Adding another Legend will not lower the audible frequency of your Legends, it will just strengthen the output you currently have. Since you'll have twice the power with 2 subs, you can turn the gain down and still have the same output, but with more headroom and more "evenness" for lack of a better word at the moment. Or, you can turn them both up and shake the rafters, your choice.

I have 2 Empires in my HT for this very reason. If I turn one of them off and move from seat to seat, I can hear drastic nulls in a few places where there is literally zero bass.
If you are planning on applying EQ to the subs/room interaction, then corner loading is the correct choice, especially if the prime focus is HT LFE tracks.
The idea being that you start with the maximum SPL which the subs can produce in that room, regardless of FR than use EQ to cut and shape the response to your standards.
Adding another Legend will not lower the audible frequency of your Legends
While it is true that adding more of the same sub to the mix does not change the sub's FR, the additional subs adding more SPL/headroom with the same FR of the original solo sub, there is a subtle inaccuracy in your phrase.
The Fletcher-Munson curves (the so-called loudness curves) which track the threshold of audibility, show that if you get low frequencies LOUD enough, they do indeed become audible.
Those who have not heard a well-designed IB (infinite baffle) sub or an array of subs (well-EQ-ed such that second harmonic distortion does not create a phantom impression of the fundamental due to ear/brain processing), may not have experienced this phenomenon for themselves but nonetheless, raise subsonic frequencies high enough and they can be heard as well as felt.
Naturally, the lower down into the "infrasonic" range you go, the louder it must be to be heard, to the point where the overall SPL would become hazardous if the entire frequency range was raised to the level required to make sub-20Hz frequencies audible. Those with the proper equipment, room characteristics and know-how usually add a "house curve" to their EQ, having the SPL capacity to handle this boost down low.
So, adding another Legend, with its consequent increase in overall SPL, COULD make audible some frequencies in the range which previously were only felt.
If in a given room, 20Hz is audible with one sub, depending on the room size, sub gain, EQ, adding a second *might* push the threshold of audibility down a couple of Hz, due to the increased total SPL.
