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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Subwoofer FUD Forum Archive => Topic started by: Wally Hyde on September 28, 2010, 12:16:14 am

Title: How would you characterize this design?
Post by: Wally Hyde on September 28, 2010, 12:16:14 am
I'm wondering what you call this design, or what it is based on.  It's a reflex enclosure with a flared duct, and the woofer is mounted on the top of the duct, firing through a slot. For a 15" woofer, the slot is 6" x 10", which gives it a 2.5:1 compression ratio.

What can anyone else tell me about the design or the theory behind it?

Thanks!

http://walt.drizzlehosting.com/img/psw/Omni.bmp

Title: Re: How would you characterize this design?
Post by: Art Welter on September 28, 2010, 11:42:40 am
Wally Hyde wrote on Mon, 27 September 2010 22:16

I'm wondering what you call this design, or what it is based on.  It's a reflex enclosure with a flared duct, and the woofer is mounted on the top of the duct, firing through a slot. For a 15" woofer, the slot is 6" x 10", which gives it a 2.5:1 compression ratio.

What can anyone else tell me about the design or the theory behind it?

Thanks!

http://walt.drizzlehosting.com/img/psw/Omni.bmp



The slot creates an acoustical bandpass, reducing the upper end output of the speaker. Placing the speaker output in the port also does more bandpass.

Depending on the crossover frequency of the mid speaker, the bandpass may be enough so no other crossover is needed.

Even when using a crossover, this arrangement would reduce speaker harmonic distortion.

An expanding port has been called a venturi port in some designs.
In a large port, the non- parallel walls can reduce some resonant effects. An exit the size of the port you have drawn would do some horn loading also, though that would be in more of the low mid range, a horn of that size would do little below 200 HZ.

Title: Re: How would you characterize this design?
Post by: Wally Hyde on October 01, 2010, 12:14:04 am
Thanks for the explanation.

FWIW, the woofer has a 2nd order LP filter at 500Hz, crossing over to the mids (not shown).