Dual subs in one box question.

[silver hatch]

I usually see in professional setups, when two subs share one box, there is a wall separating the air space inside the box. But I've tried experimenting, sharing the same air space (no wall), and it sounds great. I was wondering if this causes the amp to work harder (which might blow the amp) by having the two subs create pressure against one another.

[thechromecoyote]

:pop2: interested in the answer as well from our audio gurus

[tdman77]

There will only be a problem if you are using a multi chanel amp. If both speakers are not in phase then they will be working against one another. If you have the same subs and are using a mono amp or dual chanel bridged then it should be ok. Still it is best to have a seperate chamber for each sub. Even with good subs no two are exactly the same, one will always be a little bit off from the other one.

[RON]

There will only be a problem if you are using a multi chanel amp. If both speakers are not in phase then they will be working against one another. If you have the same subs and are using a mono amp or dual chanel bridged then it should be ok. Still it is best to have a seperate chamber for each sub. Even with good subs no two are exactly the same, one will always be a little bit off from the other one.


Completely agree. If you running mono it really won't make a difference unless you are looking for all out SQ. I ran three 10" in a seal box way back when and it was fine I am sure that some would say it was sloppy but it hit (in high school I just wanted loud!)

[Chad]

I actually PREFER to see 2 share the same airspace, there are going to be mechanical differences and some electrical differences on a per driver basis, it's just a tolerance thing. By placing 2 drivers in a shared airspace you literally "average out" these differences and the box "sees" one driver with one set of parameters. If you divide the enclosure, especially for vented designs you basically have 2 enclosures with 2 very slightly different drivers in them, this can cause a small amount of loss and phase shift in relative to the two "systems" you have created.

The problem arises when you nuke ONE driver in a shared airspace, this causes the other driver to assume it is in an enclosure twice the size and then some as the other driver acts as a glorified passive radiator, this unloading can cause mechanical failure of the working driver in short order if you don't catch it soon enough, usually the working driver will bark enough that you will catch it if you are not a complete imbecile :D

As you can imagine the above scenario will not happen in a divided enclosure. Regardless, I still vote for a shared chamber.

Chad

[bchaney]

Very interesting topic and an interesting response from Chad.

I would think that it'd be hard to calculate exactly how much volume is needed for two subs in one enclosure. Could it really be as easy as doubling volume? ex. one sub needs 1.0cf, two need 2.0cf. It would seem that each sub "sees" the full 2.0cf.

As far as blowing the amp, it should go on protect or blow a fuse before anything gets fried internally.

[Chad]

Well, calculating the internal volume is actually easier for a shared airspace! Just double it, for seperate air spaces you then have to subtract the material volume for the divider and incorporate this lack of volume into your build plans (each space has to be 1/2 the divider volume larger)