2x KEF B139 for home theatre challenge - diyAudio
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Old 8th May 2013, 03:16 PM   #1
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Default 2x KEF B139 for home theatre challenge

I've 2x KEF B139 and need to enclose them for use in a home theatre system.

They are to accompany a pair of floor standers and need to play as low as possible. I'd love 10-80Hz, though a little off either end to the benefit of efficiency.

I've attached a T-TQWT design done by Bjorno, models very well but no longer fits with my living arrangements and despite my best efforts I cannot improve on it-I've managed to eek out a few more Hz lower in the register by MASSIVELY increasing it's size but at the detriment to both bandwidth and SPL, which I thought would go against Hoffman's Iron Law?!

Space is not really an issue (it was the limiting factor in previous designs) I have at least 4m (12ft) width to play with and depth/height can be anything you'd consider reasonable to sit a TV on top of (I will be building some storage on top/in front of/around the enclosure). The subwoofers will be powered off a 12ch Sonance Sonamp 1230 (12x 30wrms, 6x 60wrms @8ohm) which will also power the floor standers. A single fold design would benefit me in building the design, and would fit better with the depth of the room!

Anyway, I leave it open to you-can you better Bjorno's design?
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Last edited by TheBaronGroog; 8th May 2013 at 03:19 PM. Reason: Forgot attachment!
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Old 8th May 2013, 03:27 PM   #2
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You need two more ? Think I have 2 sitting on the shelf ?
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Old 8th May 2013, 03:44 PM   #3
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Hi, thanks for the offer but any more audio equipment and I'll not have a home to put it in, plus they come up pretty often over here for less than the postage from the USA!
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Old 8th May 2013, 10:26 PM   #4
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Default There's always the Linkwitz Transform

I used a sub in a rather small enclosure, per Sigfried Linkwitz 1978 article for several years. Went down very well, though it was limited by max excursion. b139 don't sound good when they hit stops.

Requires separate amp, includes schematic for crossover with transform. You may find it's not enough for home theater. I had to give it up when we moved to a bigger living room, just not enough travel. 4 12" drivers was big enough....

Linkwitz Lab - Loudspeaker Design
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Old 9th May 2013, 07:03 AM   #5
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Thanks, for the link.

Had a look at the size of the room last night and have decided to limit length to 2440mm, width and height around 600mm (8ft x 2ft in old money) for convenience in buying materials.
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Old 11th May 2013, 09:45 AM   #6
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Morning bump!
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Old 11th May 2013, 11:43 AM   #7
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by TheBaronGroog View Post
The subwoofers will be powered off a 12ch Sonance Sonamp 1230 (12x 30wrms, 6x 60wrms @8ohm) which will also power the floor standers.

If I read this right, you're planning to drive subwoofers with an amplifier that's 60w @ 8 ohm when you strap two of the channels together?

You might want to consider a dedicated subwoofer amplifier that has a little more guts, like a Behringer EP series or something, for HT I think you'll run a 60 wpc amp out of juice pretty quick.

Edit: I didn't realize the b139 was a fairly small driver.

Last edited by DrDyna; 11th May 2013 at 11:50 AM.
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Old 11th May 2013, 12:39 PM   #8
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Power shouldn't be a problem, excursion will limit input power-if I ever get past the "design" stage!

Current design is just over 90dB with 1 watt input power - not sure whether for the two drivers you need to enter the voltage/wattage differently?

Last edited by TheBaronGroog; 11th May 2013 at 12:48 PM.
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Old 11th May 2013, 12:56 PM   #9
bjorno is offline bjorno  Sweden
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Hi All,

FYI: Another suggestion, i.e. a ML-TQWT using 25% more Volume than the prior: T-TQWT.

b
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Old 11th May 2013, 01:09 PM   #10
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Wow, that is a significant improvement! Now, how do I translate that to full box dimensions?

The gross dimensions I get, though would need to know the:

Length of the internal wall, distance it is away from the front/rear face and the vent dimensions?

Am I missing these from the diagrams or is there an easy way to work it out?

Is there any way of sacrificing upper extension in exchange for more SPL/lower extension?
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