Mixing subwoofers?

[Bogie]

I've already got a pair of Dayton Quatro 15s in my basement in ported enclosures. I'm thinking of adding another pair in sealed boxes. Will I be likely to run into problems?

[xstephanx]

well it IS the same driver, but the frequency response will be entireles different on both of them, which might result in cancellation?. Unless you were to say, use 4 of them in large low tuned enclosures for 25hz or 30hz and below then use two for the sealed boxes that would pick up from there. Then you have to think of how hard it is to properly integrate 6 sealed subs into one room(assuming they arent stacked). now think about all the diffculties there will be in the set up. Why not try an IB set up? with that many 15s....

EDIT****

Or! why not keep the two ported ones, and then make a pair of dipoles? then the dipoles can do all the 30hz+ and the vented can do 30-?

[simon5]

You will not run into cancellation, but the FR curve could suffer because the sealed subwoofers will improve only upper end.

[BassAwdyO]

Simon's got it right, the wave cancelation shouldnt occur unless one of your subs is wired up reverse polarity. There might be a slight cancelation at Fb of the ported enclosures however due to the typical spike in group delay there . Does anyone else know about this?

[paulspencer]

I have my two subs in test boxes, one is vented, the other sealed. The difference is hard to pick. For all the negative talk you hear of vented boxes, they are VERY similar!

What is it you are trying to achieve with adding sealed boxes?

well it IS the same driver, but the frequency response will be entireles different on both of them, which might result in cancellation?

Cancellation will only occur when the polarity is reversed. Adding another two subs of equal power will add 6db of output. This effect will not extend as low if the new subs are sealed.

The word "basement" to me spells acoustic disaster! Normally the construction is so robust that there is a massive amount of stored energy right down to the bass. If this is a listening space where a basic level of accuracy is desired, I'd first consider acoustic treatment.

If your basement is anything like most - brick walls and concrete floor - then any possible "problems" with the subs themselves will be trivial in comparison to the room itself.

[xstephanx]

Ahhhhhhh. once again i am wrong, oh well im learning i guess

I would SERIOUSLY go for an IB with 10 litres of displacement. Or maybe one really big ported box?

[simon5]

You are right that you might get some cancellation and other problems at tuning point because of the group delay, but since the sealed subwoofer will be already rolled off a bit, probably very hard to notice.

[ChesterFuzzin']

i got 2 different pairs of subs in my room...

originally i had one set vented and one set sealed..

just ended up plugging up the holes.. both sealed sounds real tight found..but the bass sounded deeper with the combo..

[Bill Fitzpatrick]

Yes, and with both vented the bass would be even louder. The question is, considering room gain maybe the bass would be excessive? I use 2 sealed 12s per channel and with room gain the bass seems just right.

[paulspencer]

The differences between sealed and vented are probably irrelevant in a garage - room resonances are likely very very bad. Take a look at the FRDC Room reflection calculator and you will see what I mean.