Multiple Subwoofer Placement

[elninoloco7]

I've had my set up for about a year now. Im only in there like once a month if not ever. I have 2 JBL 400 Watt RMS subwoofers. My theater room is 17'x20'.

At first i Had my set up like this one. It look very nice hidding the subs behind the curtain. The 2 blue boxes are the subs. READ LEGEND

But i can barely hear or feel the bass to all the seats. The curtains arnt thick at all. So i know that wasnt the factor. Then i switched it to this one here

Now at first this was the most effective way, and the bass was incredible. However i just noticed in seats 1 and 2 i feel little bass vs the seats on the riser and seat 3. (Normally i sit in seat 5) Seat 4 gets pounded with all the bass. Originaly i wanted to place the sube next to each front speaker but it wouldnt work on the left side because of no wall being behind the sub only the curtain.

Is there a better placement for my subs so i can get equal amounts of bass throught the room? or is this the best set up?

[samson]

I would try to put them on each side of the center channel, facing all of your seating. Just another off topic comment, try switching your bookshelves with your surrounds. I think you'll notice a difference there also. Not an expert, so take it for what it's worth and good luck!

[Certified THX Technician]

Just a couple observations here ...I just started a new thread on subwoofer placement ...

1. Place your subs in the middle of each side wall across from each other....directly in the middle of the length of the side walls, one on each side. You could do front and back as well, but your would have to put the rear sub into the wall since you have seats there. THX recommended spec for 2 subs is opposite each other on opposing walls in the center of the wall. Face the drivers inwards towards the center of the room.

2. Your surround speaker placements are backwards. You should have your RS-42's at the sides, with the null between the two rows of seats and the 2 RB-51's on the back wall for the rear's, 30 degrees each off center. This is also THX recommended spec. Surrounds should be bi/dipole speakers and rear's should be direct radiating (front firing).

I can explain this in much more detail with the how's and why's if you like by email. But trust me, you should reverse your surround speaker placements.

Your setup is very similar to mine ...what is the height of your surrounds (side and rear) ? I will also let you know what height they should each be at.

[elninoloco7]

Well, the thing is if i place them next to the center, theres no wall behind it. I thought having no wall near the sub made a huge difference. I'll try it though.

Yea as far as the bookshelf and surround thats how i had it at first, but for some reason i heard my bookshelf in the back more than my surround in 7.1. And my back row i could barely hear the suround, maybe because its about 6 inches awat from the wall. When i switched the surround to the back and the bookshelf on the side, i could hear a difference of improvement and i can hear all the speakers well balanced within my front rows. I will admit my back row i only hear the rear surround and not the bookshelf.

[elninoloco7]

Just a couple observations here ...I just started a new thread on subwoofer placement ...

1. Place your subs in the middle of each side wall across from each other....directly in the middle of the length of the side walls, one on each side. You could do front and back as well, but your would have to put the rear sub into the wall since you have seats there. THX recommended spec for 2 subs is opposite each other on opposing walls in the center of the wall. Face the drivers inwards towards the center of the room.

2. Your surround speaker placements are backwards. You should have your RS-42's at the sides, with the null between the two rows of seats and the 2 RB-51's on the back wall for the rear's, 30 degrees each off center. This is also THX recommended spec. Surrounds should be bi/dipole speakers and rear's should be direct radiating (front firing).

I can explain this in much more detail with the how's and why's if you like by email. But trust me, you should reverse your surround speaker placements.

Your setup is very similar to mine ...what is the height of your surrounds (side and rear) ? I will also let you know what height they should each be at.

You know i havent really thought about the height of the surround side speakers. I gotta measure that. I can send some pics of the speakers and tell me whats wrong. Right now it sounds good but i know it can sound better. I tried putting them in the center facing towards the seat. I actually went to THX website but i really didnt feel or hear an improvment in the subs.

I am assuming you mean this set-up

[elninoloco7]

This is a link of my theater

Old pics http://good-times.webshots.com/album/560490129EZKdzy

New pics http://good-times.webshots.com/album/563062030WwgBNi

[Certified THX Technician]

Yes, but the subs should be exactly in the center ...the look a little more towards the rear (I know it's only a rough diagram).

Is the red line your curtain and does the actual room extend to the back behind it? if that left wall is actually longer and the signal passes through the curtain to the back that will affect the placement and sound as well.

[elninoloco7]

Yes, but the subs should be exactly in the center ...the look a little more towards the rear (I know it's only a rough diagram).

Is the red line your curtain and does the actual room extend to the back behind it? if that left wall is actually longer and the signal passes through the curtain to the back that will affect the placement and sound as well.

Yes the red line is a curtain. its a room but within the same theater room. The room start in the left and finishes like 6 inches from the right of the center speaker

[elninoloco7]

Again the drawings are not to scale its just a layout of my system. I posted two links up above to view the pics. The new pics is what the set up is now

[elninoloco7]

Yes, but the subs should be exactly in the center ...the look a little more towards the rear (I know it's only a rough diagram).

Is the red line your curtain and does the actual room extend to the back behind it? if that left wall is actually longer and the signal passes through the curtain to the back that will affect the placement and sound as well.

So this pic was taking about a reay ago when iwas getting started haha. Gives you an idea

[Certified THX Technician]

Yes the red line is a curtain. its a room but within the same theater room. The room start in the left and finishes like 6 inches from the right of the center speaker

The left sub then should go in the middle of that entire wall, including the back room ...the standing waves first dip will be in the middle of that wall, and that is also where your first row is roughly ....then put the other sub across from it on the right wall, slightly ahead of center. You can then try moving the sub on the right wall to exact center and across from the other one to see which provides smoother response on that side. Non square or rectangular rooms are hard to control the bass properly.

You don't need a wall behind you subs...they should be out at least a 6-12" from the wall....this helps reduce the Boundary Gain (buildup of frequencies on the wall...artificially boosting the signal) .

I'll get back to you more on this tomorrow and with proper height for your surrounds etc ....also key is to make sure your SPL is the same from all speakers in the centre of the two rows of seats.

[elninoloco7]

Yes the red line is a curtain. its a room but within the same theater room. The room start in the left and finishes like 6 inches from the right of the center speaker

The left sub then should go in the middle of that entire wall, including the back room ...the standing waves first dip will be in the middle of that wall, and that is also where your first row is roughly ....then put the other sub across from it on the right wall, slightly ahead of center. You can then try moving the sub on the right wall to exact center and across from the other one to see which provides smoother response on that side. Non square or rectangular rooms are hard to control the bass properly.

You don't need a wall behind you subs...they should be out at least a 6-12" from the wall....this helps reduce the Boundary Gain (buildup of frequencies on the wall...artificially boosting the signal) .

I'll get back to you more on this tomorrow and with proper height for your surrounds etc ....also key is to make sure your SPL is the same from all speakers in the centre of the two rows of seats.

Whoa im confused. So i Put one sub in the center back room and where does the other one go? I don’t get what you mean by across the right wall. I appreciate the help by the way.

[InVeNtOr]

not trying to be a sour puss...but shouldn't this be in the subwoofer section?

lets make this simple....first off follow the advice of all the posts, they make sence.....

change the rb-51's and rs-42. make sure all the surrounds are around 5' off the floor (measured from the bottom of the speaker). the center you want either place at the same height as your face or if it's mounted lower, have it angled up toward you face. the front mains you want a little bit off the wall. you can check all these dimension at www.dolbydigital.com or www.thx.com. just go there and all these dimentions are on the web site.

recalibrate your system with a spl meter after you do that.

the sub placement is trial and error. ask the ear for some advice on how to set it up. basically you have to do the "bass crawl" to get a good location. i too wanted 2 subs but after reading on how to set up 2 subs, i got a headache and just bought a better single sub. for me, if this was my room, for O.C.D. reasons i would try and have the subs on either side of the screen (left and right) or 90 degrees from me.

i have a question....how far are you (seated) from the screen? is there any way you can move up a little? did you do the THX suggested tv viewing distance? (tv size - diagional- divided by .84)? if you can move up you can try and placing the subs behind you.

for cables try www.monoprice.com. i just bought a 50' sub cable from them for less than $10.

good luck.

[elninoloco7]

not trying to be a sour puss...but shouldn't this be in the subwoofer section?

lets make this simple....first off follow the advice of all the posts, they make sence.....

change the rb-51's and rs-42. make sure all the surrounds are around 5' off the floor (measured from the bottom of the speaker). the center you want either place at the same height as your face or if it's mounted lower, have it angled up toward you face. the front mains you want a little bit off the wall. you can check all these dimension at www.dolbydigital.com or www.thx.com. just go there and all these dimentions are on the web site.

recalibrate your system with a spl meter after you do that.

the sub placement is trial and error. ask the ear for some advice on how to set it up. basically you have to do the "bass crawl" to get a good location. i too wanted 2 subs but after reading on how to set up 2 subs, i got a headache and just bought a better single sub. for me, if this was my room, for O.C.D. reasons i would try and have the subs on either side of the screen (left and right) or 90 degrees from me.

i have a question....how far are you (seated) from the screen? is there any way you can move up a little? did you do the THX suggested tv viewing distance? (tv size - diagional- divided by .84)? if you can move up you can try and placing the subs behind you.

for cables try www.monoprice.com. i just bought a 50' sub cable from them for less than $10.

good luck.

Again i normally had my RS 42's on the side and the RB 51 on the back orinigially it didnt work, but i found my error, they are about 6 feet high, which i think is okay but my rears are 8 feet high. I can move the seats about another foot out. My side surround its about 6 feet, however it is too far up so i need to move it slightly back. My front Row is about 12 Feet from the screen and the back is about 16. I have 106" screen. My sub cables are long enough to move them all over the room as well as the speaker cables.

[elninoloco7]

I played around with the subs and got the best sound. FINALLY. I placed them infront of each front speaker angled towards the center. (Same way the fronts are angled) Sounds fantastic in all the seats, and well balanced. Rear row still gets pounded with bass than the front but im thinking its because im near the back wall and the riser i built shakes like crazy, which i like.

Just switched up the RS 42 to the sides at 5 feet in between both rows and the RB 51 in the back at 6 feet. I hear so much more sound from the sides in both rows, however, like the first time, i cant hear the back bookshelf speakers. The level on the receiver has been adjusted and i messed around with the volume lever for the rears and not much going on. I have it set on 7.1 NON MATRIX. I also poped in a 7.1 movie (Rambo) And ihear the sides more that the rear. The front row i can hear the back surrounds sometimes, but on the rear row nothing. Maybe because its about a foot from the back wall and the speakers extend out pretty far. I am unable to move the seats, as the first row will be to close to the screen.

[InVeNtOr]

the reason you hear the rears more is most likely you haven't calibrated you system. get a spl meter and a tri pod. then go through and level out the speakers. i wouldn't use the microphone from the AVR, it's best to use the spl meter to fine tune it.

[InVeNtOr]

106" screen (divided) by .84 = 126.19" or 10' 6". if you want to follow the thx guide line you can move your seats up a little. this may help with the rear speakers for the people in the back row. just so it is said, that dimension is from your eyes to the front of your screen). also how did you set up the receiver for the speakers - as far as distance set up? you can tell the receiver that the center channel is at 8' (when it actually is placed at 11') and the rear speakers are at 7' (when they actually are at 4') etc. that way the receiver sets delays in your speakers arrangenment. it can give the illusion of a bigger room and may help out in the sound area.

besides the thx info, everything else can be found in your manual. there should be a section explaining the receiver set up.

[DrWho]

The THX spec calls for dipole side surrounds because it is striving to create a non-localized sound. The reason we use monopole rear surrounds is to fill in the hole in the rear soundstage that would otherwise exist as a result of just the side surrounds.

The way non-localization is achieved is by spreading the sound out over a wide enough area such that the sound arriving at the listening position is a combination of both the direct sound of the speaker and the reflections bouncing around the room.

If you took a monopole and a dipole speaker out into the middle of a field, they would both have the same localization. The reason I bring this up is to stress the point that the non-localization is a direct result of the sound bouncing off the walls in your room.

In order to get even coverage in all the listening positions, each listening position needs to reside inside the direct sound of every single speaker. Think of each speaker like a flashlight...if you want to light something up, then you shine the light at the object - not at the wall on the other side of the room. When you have the RB speakers in the rear, the light is shining out at 90x60 degrees - which means any seat off to the side of the speaker or directly under the speaker isn't getting any light on it...and thus you get uneven coverage.

So all that to say, you absolutely could and arguably should be using the RS speakers for your surrounds. First of all, you absolutely require a wide dispersion speaker in order for the direct sound to hit every single listening position. But secondly, the geometry of your room is such that you won't be getting any reflections from the wider dispersion at any of the listening positions. In other words, the RS style speakers are actually satisfying the intent of the THX spec, which is providing a localized sound for the rear channels!

So if you wanted to take the THX recommendations to the Nth degree, then you should be running four of the RS speakers for your surrounds. But with the gear you already have on hand, using the RS style for the rears makes a lot more sense....and coincides with your own listening comparisons too.

[InVeNtOr]

well Dr....you may have just smacked my pepe.....lol.

sounds like it makes sence. i guess i never thought about it like that....i only have a living room set up and 1 seat to worry about....lol

[elninoloco7]

Well i jsut finished calibrating my system and moved my 2nd row slightly forward. Tested my THX Ultimate Demo DVD, Rambo (Blu Ray 7.1 DTS HD Master) and U-571 (HD DVD DTS Depth Charge Scene). Surround sound now sounds awesome. I can clearly hear the 7.1 effects in some scenes. The subs are just fantastic well balanced. On just 5.1 movies is it best to leave it at NON Matrix mode or Matrix?