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Old 8th February 2012, 06:44 PM   #1
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Default Sealed or Vented????

I just got my hands on a pair of SB Acoustic 12'' woofers. The FS is 19Hz and the QES is .42. My choices are to build 4.0 cubic ft of volume ported cabinets or 2.6 cubic ft of volume sealed cabinets. The woofers will be working with midranges and tweeters. What direction should I take. Thanks.
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Old 8th February 2012, 06:52 PM   #2
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If you want a louder, flatter response to F3, ported, if you want the best transient response and have EQ to flatten the LF response, sealed.

There are also an infinite range of alignments between the two you suggest.
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Old 8th February 2012, 07:44 PM   #3
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In Martin Colloms book "High Performance Loudspeakers" he makes the general comment that subjectively the sealed (2nd order) appears to have more bass than a 4th order reflex despite the theoretical advantages of the latter......all things being equal (Which they seldom are!). He tentatively puts this down to less phase change in the former. But sensitivity to phase seems to vary a lot........

Are you in a position to try both before making a final pair?
More work but could be an interesting exercise.

Cheers, Jonathan
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Old 10th February 2012, 10:55 PM   #4
Lojzek is offline Lojzek  Croatia
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Hi Ccdave !
Quote:
Originally Posted by Ccdave View Post
I just got my hands on a pair of SB Acoustic 12'' woofers. The FS is 19Hz and the QES is .42. My choices are to build 4.0 cubic ft of volume ported cabinets or 2.6 cubic ft of volume sealed cabinets. The woofers will be working with midranges and tweeters. What direction should I take. Thanks.
For example:

SB 34 NRX75-6
Fs=19 Hz
Re=4,2 ohms
Qts=0,4
Vas=260 liter

Passive box, flat response, low F3 =ported box, Vb= 250 liters, F3=20 Hz
Passive box, flat response, high F3 = sealed box, Vb=55 liters, F3= 50 Hz

Calculated values of Vb and F3 might not be totaly accurate, more like a guideline.
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Old 10th February 2012, 11:07 PM   #5
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by Jonathan Bright View Post
In Martin Colloms book "High Performance Loudspeakers" he makes the general comment that subjectively the sealed (2nd order) appears to have more bass than a 4th order reflex despite the theoretical advantages of the latter......all things being equal (Which they seldom are!). He tentatively puts this down to less phase change in the former. But sensitivity to phase seems to vary a lot........

Are you in a position to try both before making a final pair?
More work but could be an interesting exercise.

Cheers, Jonathan
I guess ole Martin has never heard a good vented enclosure ...
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Old 10th February 2012, 11:16 PM   #6
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It is very rare ...
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Old 10th February 2012, 11:30 PM   #7
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Btw Wayne Queensland, where I live, is in Australia the home of Neville Theile and where Richard Small did his work so we're really BIG on vented encloses down here.....at least in theory..ha, ha.
It is interesting that Theile's work became known through the JAES in the early '70's but had been published locally some ten years before and just wasn't recognised for the break through that it was.
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Old 10th February 2012, 11:31 PM   #8
pski is offline pski  United States
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Can't speak technically but I made a woofer box for a JL Audio 6w3 and a JL Audio bass amp.

The box is hardly larger than the woofer but everyone is amazed.
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Old 11th February 2012, 01:17 PM   #9
Scott L is offline Scott L  United States
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Default Forced to make a choice here......

FWIW I do sit firmly in either camp, I have heard both bad and good outcomes with either application.

Assuming the OP meant "A Qts of .42 (?) " and an Fs of 19; furthermore giving the hint that this will be part of a 3way system, I'd opt for the PROPER vented alignment. I'm thinking that a 3way system will be set up away from room corners/ boundries whereas sometimes a devoted SEALED woofer/subwoofer is placed in or near a room corner and gets the associated room lift along with the shallow slope makes for a better overall compromise. just my 2 cents and not worth much these days
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Old 11th February 2012, 03:04 PM   #10
Jay is offline Jay  Indonesia
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The Qts is more suitable for vented. I don't believe in small enclosure for woofer like this. It seems that the woofer has been designed for vented in mind?? Just be aware that you may require bigger room.

I like (the transient of) a closed cabinet, and I hate it when certain woofer is more preferable for vented design.
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