Insulation/Sub Placement Questions

[comradburk]

I admit, I know little about audio (but I did read the stickies a bit) and don't have an epic home theater quality sound system (but it is just for my computer). I just had some quick questions though...I just moved into my college dorm a few weeks ago, and I've been trying to get my sub set up in a decent location with my computer speakers. I have a Logitech Z-5500 speaker system and I'm just trying to get a fuller sound throughout the whole room...I had no problem finding a good spot for it in my room at my house, but the problem is, the dorm room is rather small and the walls are more or less cinderblocks...no matter where I place it, there seems to be no way to prevent the lower bass from just dieing in the middle of the room and becoming really boomy in the corners of the room.

Anyways, what I'm wondering is, because of how hard and reflective the walls are, without buying acoustical foam, would it pretty much be impossible to have a somewhat full sound throughout the room?

Thanks...

 

[bpape]

Any and every room will have nulls and peaks in response as well as boomy bass in the corners. That's just the physics of it. This is why you don't sit against a wall, in the middle of the room, or in a corner.

Even with foam, that's not going to help anything in terms of the bass. For that, you need something thicker and more dense like 3lb fiberglass, mineral wool, etc.

Bryan

 

[tbewick]

I admit, I know little about audio (but I did read the stickies a bit) and don't have an epic home theater quality sound system (but it is just for my computer). I just had some quick questions though...I just moved into my college dorm a few weeks ago, and I've been trying to get my sub set up in a decent location with my computer speakers. I have a Logitech Z-5500 speaker system and I'm just trying to get a fuller sound throughout the whole room...I had no problem finding a good spot for it in my room at my house, but the problem is, the dorm room is rather small and the walls are more or less cinderblocks...no matter where I place it, there seems to be no way to prevent the lower bass from just dieing in the middle of the room and becoming really boomy in the corners of the room.

Anyways, what I'm wondering is, because of how hard and reflective the walls are, without buying acoustical foam, would it pretty much be impossible to have a somewhat full sound throughout the room?

Thanks...

Hi

I'd recommend putting the sub in the corner of the room, because it should achieve maximum output there. Following this, adjust the sub's volume until the boominess is gone. Perhaps you've heard this before, but you could try putting the subwoofer at the place you sit. You then put some music on, and then crawl around the room until you find a location where the bass has maximum impact and volume. This spot is where you position the subwoofer.

You could try setting the adjusting the tone controls to improve fullness of the sound, e.g., increasing the bass and lowering the treble. Another option would be to experiment with speaker/listener placement. Sitting nearer the walls may improve the amount of low-end bass, although I've heard that it's best to avoid sitting too near to acoustically reflective surfaces. If the subwoofer has a port, you could block this up. This will reduce high-bass, and possibly improve the low-end bass response proportionally.

These two papers have more information on speaker set-up:

http://www.harmanaudio.com/all_about_audio/loudspeakers_rooms.pdf
Loudspeakers and Rooms - Working Together, Floyd E. Toole.

http://www.aes.org/technical/documents/AESTD1001.pdf
Multichannel surround sound systems and operations, Audio Engineering Society Technical Council.

 

[bpape]

While placing the sub in the corner will in fact give the most output, it will also generally result in the least smooth frequency response since you're maximally exciting all of the room modes by sitting at the end of all 3 room dimensions.

The Harmon papers are an excellent resource. Note that their recommendations are to place 2 subs in the MIDDLE of opposite ends of the same dimension. The ONLY time the recommend corner placement is if you have 4 subs - 1 in each corner.

If you want to work with 1 sub and try to minimize room issues, try setting the sub up at a prime factor of the room dimensions. So, say 2/7 or 3/7 of the room width and up off the floor a foot. That leaves you only against one room dimension end.

Bryan