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I currently have 2 subs that I EQed as 1 with REW with good results. I have a rather large room (22'x33'x10') which is open to other rooms such as kitchen, living and dining rooms) and my plan is to add 4 or 5 more subs around the family room for a total of 6 or 7 subs. Are there any guidelines/procedures out there that discuss multiple sub placement and how to EQ and integrate a multiple sub set-up?

Reasons for adding more subs: 1) clipping during explosions, etc. and 2) desire for more even frequency response throughout the room.
 

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A more detailed answer: In most any room you’re going to have widely divergent measured response at different locations, and possibly at different seating positions as well. You might plant one of your subs in your listening position and take some measurements at the proposed locations for the additional subs. REW can average the readings to get you an idea how response would look at the seating position.

What the graph probably won’t show you will be the cumulative effect subs in less-than-optimal locations might have on extension. For instance, if you found (like I did) that you got the best extension with the sub in a corner, you can’t expect that extension will be nearly as good when it’s placed near a hall doorway, next to an open stairwell, under an end table several feet from any wall, etc. If the sub got down to 20 Hz in the corner, you’ll probably find it dead below 30-40 Hz at most of those other locations. What will be the cumulative effect if you have one sub getting to 20 Hz, and then add 3, 4, or 5 others that “top out” at only 30-40 Hz? The combined output off the latter will swamp the former, and your deepest extension will be completely blown out. You’ll have a 30-40 Hz system. But hey, at least it’ll be loud. :D

Regarding the quest for even response throughout the room, I’ve lived in a few places like you describe (currently are, in fact), and what I’ve found is that bass response is fairly consistent at most seats that are away from boundaries. However, if you have any seating against a wall, there will always be boundary reinforcement factor. I highly doubt adding more subs around the room will eliminate that.

In fact, I’ve found that in open rooms like ours, it’s much easier to achieve uniform response than it is in a dedicated room with symmetrical shoe-box dimensions. In those rooms, you have a “bass hole” in the dead center of the room, and measured low frequency SPL increases as you move towards any boundary. When you see people battling with drastically different response or output at seats right next to each other, I typically find they are in dedicated shoe box rooms. I’ll take my open family room any day!

So, I think your best bet would be put the money you would spend for 4-5 more subs towards one or two better-performing subs, unless for some reason you just can’t get uniform response any other way. In the meantime, you can help alleviate the clipping problem at least somewhat by employing milder equalization on the subs you do have. In other words, reduce the range between the deepest cut and greatest boost.

Regards,
Wayne
 

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To build on what Wayne has said, some people have done two really good subs to handle the 15-50Hz range that are located up front and then place mid-bass modules (HSU MBM-12) nearfield for the 50-xo Hz. Another variation of this option is to run the mid-bass module up front with the mains and place the main subs nearfield. Many people have done both with very good results.

If your room is as large and difficult as you say, another option you should look into is an infinite baffle set-up.
 
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