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In Reply to: JBL 2245 in 828 cab posted by jnorv on March 24, 2007 at 09:08:34:
Greets!FWIW, I'd use a smaller vent for a HIFI/HT app, ~7" dia. (38.485"2) x ~8" long.
Follow Ups:
it might be time to pull the 2245's and put them in tapped horns. It is always a crap shoot in picking vent sizes. There is the theory of making the vent size the same as the driver size. At some point in making them smaller you run into vent velocity problems.
Greets!Not really, you want the vent mach to be <5% to ensure both low vent compression/'noise', which the 7" vent is, so any lower vent mach (larger vent) normally causes peaking at Fb and the extra length adds its own out of BW 'coloration', which may/may not be euphonic, but for sure is technically distortion, so to be avoided if practical in a HIFI/HT app IMO.
As always though, YMMV.
Simple enough to change vents.
Greets!Yep, let me know what you think if you do it.
This is very interesting indeed! Are you happy with the results or are you still tweaking? I'm in a bit of a quandry with how to configure my "stuff" (see original post). I like the look of the horn inside the cabinet rather than on the top. What am I sacrificing by doing this? What about flipping the cabinet over so that the horn is on the bottom?
I might consider your idea with the 2245 but am wondering what that does to the original woofer, in terms of reducing the effective horn size?
Thanks, Andrew
Greets!I assume you're asking jnorv these Qs, so will only address the ones he didn't:
The horn-in-port increases internal reflections, increases port turbulence and just generally mucks with the cab's reflex portion of its performance. It really screws with off axis response and puts the woofer too low for optimum performance in the XO BW.
Flopped upside down, all the critical mids/HF BW is exiting/reflecting off floor/whatever at foot level, so will sound unnatural at best, though I've been in folk's homes that preferred them this way for what I assume was because they were driving them with horrible sounding early design SS amps and probably didn't attenuate the horn either. I didn't stick around long enough to check once they fired them up and weren't willing to experiment further, though I did manage to buy one disillusioned owner's pair dirt cheap.
BTW, adding a sub in the bottom doesn't affect the horn's size.
you seal off the upper part of the box behind the original woofer so that it performs as a simple horn with a sealed back chamber. The bottom of the box, which is about 8 ft^3, then is used as a bass reflex system for the new woofer.
The only 15" drivers I have are JBL 2225J and EV SRO 15. Would either of these be suitable candidates for adding a sub to the 828 cabinets? If so, how would I tune the ports? Thanks, Andrew
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