2 subs and standing waves?

[yepimonfire]

during my research on ways to reduce acoustical problems particularly at low frequencies i've stumbled upon a few thing that suggested using two identical subs spaced equidistantly from the side walls, claiming it would even out bass response issues caused by room problems. any of this true? to what extent? as a side question what benefit besides more SPL does two subs have? also doesen't two drivers increase extension by about 5-10hz? nearly all speakers i've seen that had one woofer and two woofer models in the same size cabinet using the same woofers etc. the one with more woofers had anywhere from 5-10hz more extension. would the same be true for dual subwoofers?

 

[zhimbo]

as a side question what benefit besides more SPL does two subs have?

SPL gain is not all that great. The main point is to even out bass response through the listening area. To increase SPL the most, you should co-localize/stack the subs, so that they completely reinforce each other (but this does nothing to even out response through the room). This will give you up to a 6dB increase.

also doesen't two drivers increase extension by about 5-10hz?

Two identical subwoofers will have exactly the same frequency response curve as one. You don't change the sub's frequency response merely because another sub is in the room as well. It's possible that with a flatter room response you might get a little more effective extension in your listening location, but don't count on it.

nearly all speakers i've seen that had one woofer and two woofer models in the same size cabinet using the same woofers etc. the one with more woofers had anywhere from 5-10hz more extension. would the same be true for dual subwoofers?

Speakers with two woofer drivers are different designs than speakers with one. Two subs of the same design...have the same design.

 

[gene]

This article should address many of the questions in this thread:

http://www.audioholics.com/tweaks/get-good-bass/multiple-subwoofer-setup-calibration-1

You don't need to co-locate subs to realize the added gain.

I also recommend reading chapter 13 of Sound Reproduction by Dr. Floyd Toole which goes over all of this exhaustively.

 

[GO-NAD!]

This article should address many of the questions in this thread:

http://www.audioholics.com/tweaks/get-good-bass/multiple-subwoofer-setup-calibration-1

You don't need to co-locate subs to realize the added gain.

I also recommend reading chapter 13 of Sound Reproduction by Dr. Floyd Toole which goes over all of this exhaustively.

I'll vouch for both pieces of advice. I referred to the article and read the book when trying to decide where to place my in-ceiling subs. I'm quite happy with the results!

 

[yepimonfire]

thanks gene this is exactly the answer(s) i needed. on another note, i would obviously be using this mainly for music, so would i be able to notice a directional difference with four subs? (i think not because all my music is matrixed to 5.1) i know they say bass is not directional, and well i will say this is true from experience when keeping the sub near the front speakers, if i put the sub to the left or right of me facing a completely different direction then the main speakers, i can detect it easily.

 

[j_garcia]

2 drivers in the same enclosure playing the same thing will not extend any deeper than one, but you will get a +2dB increase in sensitivity.

Even with one sub you will have standing waves. Two subs will allow you to change the behavior of some of those waves within the room.

Low bass waves are longer than the room and thus it is harder to detect the location of the source, but that does not mean you can't tell where the sub is, especially depending on the room, where you sit, and how you have it setup. The lower the crossover, the less likely you will be able to localize.

 

[yepimonfire]

hmm, maybe it is because of an overall increase in cabinet volume in order to accommodate a second woofer that increases extension. also i have another sub question, is cranking the subs gain to the max and controlling the output level via the receiver a bad idea?

 

[yepimonfire]

oh and an acoustical question, would moving my bass traps to floor level instead of ceiling level reduce bass problems, considering the sub is on the floor?

 

[j_garcia]

hmm, maybe it is because of an overall increase in cabinet volume in order to accommodate a second woofer that increases extension. also i have another sub question, is cranking the subs gain to the max and controlling the output level via the receiver a bad idea?

That is most likely the reason. My speakers come in a bookshelf and tower version and the tower obviously has more volume and it does have lower extension.

oh and an acoustical question, would moving my bass traps to floor level instead of ceiling level reduce bass problems, considering the sub is on the floor?

I would tend to think so. At ear level should net you a more audible difference than up above.

 

[highfigh]

Using more subwoofers is more about the distribution of the standing waves than output in a home system. If it was for live sound, it would likely be for the added SPL as well as minimizing the spots where the bass disappears vs where it's too strong and how those coincide with where the board is located.