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Best position for groundstacked pair of subs

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Loren Jones:
Hi all,

I am aware that there are lots of discussions on this and I have read through many of them.  I've also read the recent "avoiding Power Alley" article on PSW.

I just wanted to ask for people's thoughts on my particular application.  I am going to be trying out a pair of groundstacked subs in our church as an alternative to our current flown subs (see pic).  In the pic each of the three hangs has a dual 15" sub in it.  I am planning to try turning those off and running a pair of groundstacked 21" subs instead.  Output for the levels we run at won't be a problem.  The question is best coverage.  For reference, I think the distance from the left side speaker cluster to the right is about 80 feet.

Position choices for the pair of subs would 1)  One on either side of the center stage stairs, that puts the subs about 12-14 feet apart.  2) Both together on either side of the stairs, which would put them about 6 or 7 feet off of the center of the room.  3) One sub under each of the left and right speaker hangs, which would put them about 75 or 80 feet apart.

I am guessing that #2 would be better than #1, but I don't know about option #3.  Of course I will try out a couple options and see what sounds best, but words from the wise are always helpful and appreciated.

Thanks,
Loren Jones

Bob Leonard:
Loren,
I would want to avoid possible long delays that may tend to make the subs sound as if they were not a part of the same system. I realize that your DSP can cure that problem, however, humans feel the music or material also and that may lead to a strange listening experience. Looking at the photo, nice installation by the way, I would experiment as you suggested but start by placing the subs one each where the top of the stair railing meets the stage. Not at that level, but centered between the L/R and center speaker clusters.

Ivan Beaver:

--- Quote from: Loren Jones on February 12, 2011, 10:25:47 am ---Hi all,

I am aware that there are lots of discussions on this and I have read through many of them.  I've also read the recent "avoiding Power Alley" article on PSW.

I just wanted to ask for people's thoughts on my particular application.  I am going to be trying out a pair of groundstacked subs in our church as an alternative to our current flown subs (see pic).  In the pic each of the three hangs has a dual 15" sub in it.  I am planning to try turning those off and running a pair of groundstacked 21" subs instead.  Output for the levels we run at won't be a problem.  The question is best coverage. 
--- End quote ---

If you are talking aobut "coverage" meaning as equal as possible across the listening area-the groundstacking is going to make it a lot worse.

The people near the subs are going to be a lot louder than the other seats (say at the back of the room).

There is no way to avoid that-inverse square law.

Part of your current problem is the 3 positions of the subs.  I would consider putting them all together in the middle-flown as close to the celing as possible.

Loren Jones:

--- Quote from: Bob Leonard on February 12, 2011, 11:27:59 am ---Loren,
I would want to avoid possible long delays that may tend to make the subs sound as if they were not a part of the same system. I realize that your DSP can cure that problem, however, humans feel the music or material also and that may lead to a strange listening experience. Looking at the photo, nice installation by the way, I would experiment as you suggested but start by placing the subs one each where the top of the stair railing meets the stage. Not at that level, but centered between the L/R and center speaker clusters.

--- End quote ---

Thanks Bob,

I will give that a try as well.  That I guess would make sense as far as doing the most possible to give the most equal distance between all parts of the audience and one of the subs.  Is that the perspective you were looking at it from?

Loren

Loren Jones:

--- Quote from: Ivan Beaver on February 12, 2011, 11:48:33 am ---If you are talking aobut "coverage" meaning as equal as possible across the listening area-the groundstacking is going to make it a lot worse.

The people near the subs are going to be a lot louder than the other seats (say at the back of the room).

There is no way to avoid that-inverse square law.

Part of your current problem is the 3 positions of the subs.  I would consider putting them all together in the middle-flown as close to the celing as possible.

--- End quote ---

That is what I am afraid of Ivan.  Many members of our congregation comment that they are missing a sort of visceral impact or bass power from the current system which they felt was present with our previous all groundstacked system we had prior to building this facility.  So it is the old "ground coupling" idea that I am wondering about partly.  Also it is a suspended ceiling (probably 4 ft above the tiles) so we the current subs aren't that close to a hard boundary above them.  Finally the current double 15" cabs really roll off pretty strongly below 45 or 50 hz whereas the subs to try on the ground have solid extension to 30 or 35 hz with I think even a little more gentle rolloff below that.

I am really just planning to try this for a week or two just as a curiosity more than anything.  If we were going to do anything permanent I am sure that your suggestion for the subs all to be flown together just above the center cluster would be best.  I'd think a pair of TH118's above that center cluster would be more than enough for us :)

Thanks for your input,
Loren Jones

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