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21" sub build - need input

1404 Views 8 Replies 4 Participants Last post by  Garric33
Looking at some drivers for a 21" sub build -


Leaning towards the B&C 21SW115-4, since I can get it in Canada. Does anyone have prior experience with these drivers, or have input on a box for these drivers ? I was thinking of a ported box, with a tune in the mid 30s. Box size somewhere near 8 cubic feet.

I am looking to add this a pair of subwoofers -

(1st sub) 2 x CSS SDX15, tuned to 11 Hz, ~ 25 ft^3

(2nd sub) 1 JBL 2241 18", tuned to mid 30s, ~8 ft^3

I would like some more punch for both music and HT. I have a large basement that seems hard to create SPL in. Also, I am trying to limit the number of extra subwoofer boxes that I have along the back wall
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ricci is the guy you need to find. he built a test sealed box AND he built some big ported cabs for that driver.

poke around data-bass.com for the measurements on the sealed and use to search tool and you should be able to find his ported build.

if you want absolutely stupid level bass, danley uses a pair of those drivers in the th-221 aka "cinemonster" which is a horn loaded beast used in commercial imax cinemas. somebody could probably help you diy something similar if you have some decent wood working skills.

the only thing about that driver is that it starts to run out of gas around 20 mm xmax and once you get to a certain low note for home theater, it becomes largely all about displacement.

edit: and if going to be used for home theater something around 25hz tune is about as high as you want to go if you choose ported.
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Something is not right if the dual 2241's aren't giving you enough output above 30hz. With a highpass filter below tuning to keep excursion in check, they are capable of over 130db.

Adding a 21SW115 and porting it to ~30hz would just give you headroom where you don't need it.

I think you need to take measurements to see if you are getting some cancellation issues or if there is a setup issue.
I wasn't very clear - I only have 1 JBL 2241. Edited initial post. I expect I wouldn't be wanting more if I had a 2nd 2241 in a matching cab.
i kind of hate to bring this up as it has been discussed a lot, but what mains are you running? after a lot of research (actually analyzing the spectral content of the music), i was surprised to find out that a lot of the "bass" in music is actually up in the lower midrange or above.
mains - (each)

2 x Dayton Audio RS225-4

2 x Dayton Audio RS100-4

1 x Morel CAT 408

Actively crossed at 750 Hz/5500 Hz, 24 db/octave LR I think (going on memory here).
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have you done any analysis like mr. c. suggested in order to see if you have a big suckout at some frequency in your room?
The subs you suggest seem to be 10Db moore efficient than you mains. You'll be limited by the dynamics of your mains (I know you go active...)
maxserg - I agree. I guess I like to run hot bass. Looking at some Unity U215s in the future. I have a soft spot for the mains though, just based on the amount of time I put into them. Easily 200 hours.
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