sub placement question??

[tkot]

i have had my system set up in three different rooms and in its most recent room it has lost more bass output than i think it should have.

because of the giant pita of moveing things around i was wondering if someone would give me a starting point, on sub placement in my room.

the room

13x19x8

the north wall is 13 feet, concrete block, 5 ft under grade.

this is also where the screen is. mounted 6 in off the wall.

the east wall is also concrete block (19 ft).

the south wall is framed with drywall and the opening into the room is located

in the corner against the west wall (the opening is 38 inches wide) into a short hallway

the west wall is framed,with drywall and has a brick fireplace that takes up the center third of the wall.

the seating area is 12 ft back from the north wall

the subs now sit front and center on the north wall under the screen. the backs of the cabinets are 1 ft from the wall.

where should they go?? im useing cornwalls for the fronts and they are forced ,because of screen size, into the corners.

the subs can be stacked verticaly or horizontaly if that would be better??

they are twin 15 cabs that are front ported (h36 w20 d18)

any thoughts as to a starting point for placement??

thanks in advance

jay

[Colin]

read this:

http://www.audioc.com/library1/subprimer.htm

then this:

http://www.harman.com/wp/index.jsp?articleId=1003

(hint: you are on the right track)

[tkot]

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On 3/15/2005 11:20:54 PM Colin wrote:

read this......

(hint: you are on the right track)

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sorry it took so long to respond but i read and then reread the second artical.

if i got anything out of it , it was that i really have 4 subs

(i run the cornwalls full range)

so the best placement would be the mid points of the 4 walls

in a home theater setting this has some issues

so the next best thing would be with the subs in the rear corners

this also has the issue of putting one of the subs in the doorway into the room.

so the next best would be to put the subs mid point on the longer walls( kills ever useing the fireplace for anything other than a sub stand)

aaarrrggg!!!!

colin, thanks for the links!!!

i now realize that this isnt going to be easy

now someone hand me a large caliber handgun

j/k

jay

[DrWho]

One trick that seems to work well is to put your sub at the main listening location and then crawl around the room until you find a spot where the bass sounds the best. Now put your sub in that location and you should have plenty of bass at the main listening position.

I would start off with using one sub and getting it dialed in first and then adding the second sub (doing the same method WITHOUT the first one playing). Then fire up both subs and tweak as necessary.

[Colin]

what about both sides of the fireplace or one on the front and one on the back wall?

[formica]

I'm familiar with the Harmon papers... which tried to achieve the "flattest response in THEIR test room". Although it'll provide some general ideas on what the different placements achieve (exciting room modes, tailoring response, etc...), it unfortunately doesn't provide a fool proof placement guide.

The catch is that not all rooms behave the same way... and this will depend on room shape, wall construction, openings, finishes, etc...

So, what should you do?

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On 3/16/2005 3:10:43 AM DrWho wrote:

One trick that seems to work well is to put your sub at the main listening location and then crawl around the room until you find a spot where the bass sounds the best. Now put your sub in that location and you should have plenty of bass at the main listening position.

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I think that would be a good starting point. Because of the bass wavelengths, the sub and listeners positions are interchangeable. If you want to get fancy... you can do the same thing with test tones and a mic (or SPL meter). ETF (a real time analyser software) has a sample room on their site which steps you through a similar optimization.

Good luck...

Rob

PS: don't forget to verify the phase adjustment of your sub at it's crossover point.

[tkot]

if i use the plan of putting the subs in the listening position,

does it matter what way they are pointed, to the front/rear/side of the room. or should i lay them down pointing up at the ceiling??

come to think of it, has anyone ever tried pointing the subs at the ceiling?? i wonder what effect that would have on bass output??

jay

[DrWho]

bass is pretty much omnidirectional and the wavelengths are so much larger than the driver itself that it really doesn't matter which way they're pointing. Nevertheless, I think I would end up pointing them in the direction of where I'd be putting the subwoofer.

[Colin]

only low bass is omnidirectional, mid bass, which is most of what we hear, is directional, placing a sub near the middle of the soundstage locates the bass the best, placing it in the middle behind the speakers, deepens the soundstage...