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wayne, adam, sam or anyone else who can run pialign [message #36983]

Wed, 19 June 2002 09:59

replay
Messages: 284
Registered: May 2009

Grand Master

i want to put my pair of jbl 4655's to good use. as we all know these lack response below 80hz. i have a pair of omega pro-18 which i'd like to build cabinets for. i would place each jbl on top of each omega box. what is the smallest volume box i can build and still maintain good deep bass response. the speakers will be x-overed actively so i can play around a bit. also what is the recommended x-over point between the omega and the jbl woofer in the 4655? thanks in advance!

cheers,

george

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PiAlign says... [message #36993 is a reply to message #36983]

Wed, 19 June 2002 15:54

Wayne Parham
Messages: 18784
Registered: January 2001

Illuminati (33rd Degree)

Using your numbers, Fts=28, Vas=12.49 and Qts=0.24, PiAlign values are Frd=28, Vad=12.49 and Qd=4.17. PiAlign suggests making a 3 cubic foot box tuned to 44Hz. For a bass-reflex cabinet, actual dimensions are 26" x 18" x 12" and with a rectangular port having inside dimensions of 3 1/2" x 6 3/8" x 5 5/8" long.

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Re: PiAlign says... [message #37000 is a reply to message #36993]

Wed, 19 June 2002 18:24

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Messages: 284
Registered: May 2009

Grand Master

thanks wayne! a couple more questions. can i shape the box to resemble a cube as long as i stay close to 3 cu ft? also what is the -3db point for that box and at what frequency should i x-over to the jbl 4655's for best performance?

cheers,

george

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Re: PiAlign says... [message #37003 is a reply to message #37000]

Wed, 19 June 2002 21:00

Wayne Parham
Messages: 18784
Registered: January 2001

Illuminati (33rd Degree)

You can build the box cube shaped as long as you crossover low. Above 300Hz, a box this size made as a cube will have standing wave resonance problems. But if you crossover a couple octaves below that with a steep slope, it won't be a problem. I'd also suggest you crossover at or below the frequency where the distance between your sub and main speakers equalled 1/4 wavelength. So, for example, if you plan to crossover at 100Hz, be sure the sub and the mains are within 3 feet of each other.

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