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Old 7th December 2006, 11:48 PM   #1
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Lightbulb Multiple KEF B139s

I have 8 KEF B139s and plan on using 4 per cabinet to
make a stereo pair of subs. I heard they work great in
TL, but for 4 units per cab, I think it would be too large
to build suitable enclosure for ordinary size living room.
Any other ideas on sealed box or passive radiator based
design?
They are SP1044 by the way.
Anybody else ever use multiple SP1044s in any type
enclosure?
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Old 8th December 2006, 12:06 AM   #2
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I once found a web site describing two B139s in an OB H frame Sub. It looked interesting and was quite a small enclosure, (if you can call it that). Four of them should be pretty cheap to make and might give you some good results. Unfortunately the link was on my Mac, which is currently dead, but google should help.
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Old 8th December 2006, 01:45 AM   #3
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Default well you could...

build them into four "W frame" dipole cabinets that would be very compact and go as low as you will ever get them to go. Would make for excellent loading of the room with four cabinets distributed. There is a link in the Ripole thread somewhere if you are interested. Just found the link here...http://www.tech-diy.com/Dipol-Subwoofer.pdf Regards Moray James.
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Old 8th December 2006, 09:07 AM   #4
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That's the one!
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Old 8th December 2006, 09:53 AM   #5
Dag is offline Dag  Sweden
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You can use them in Isobaric configuration to reduce box size.

Isobarik: Also known as compound loading. By using two low frequency drivers (generally mounted face-to-face and wired electrically out-of-phase or mounted front-to-back in a shallow tube and wired electrically in phase) you can halve the volume of the cabinet without reducing the low frequency extension of the subwoofer.

http://www.audiogearreviews.com/tech...n/isobaric.asp

The Bricks (aka Linn Isobarik DMS) used two B139 (isobaric). Maybe not the best speaker but the bass is very good (and it makes me happy: ).


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Old 8th December 2006, 10:36 AM   #6
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Have a look at what Linkwitz did way back with his breakthrough satellite & subwoofer system. Speaker Builder 1980 I think, it's on his website.
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Old 8th December 2006, 01:32 PM   #7
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Default Dag....

Quote "You can use them in Isobaric configuration to reduce box size."

With "W Frame Dipole (Ripole)" there is almost no box at all and the design will reduce the driver Fs by about 7-10 Hz. Add to this the fact that you will also have directivity control (cardioid pattern) what more could you ask for? If you only want two cabinets then double up the 139's so they provide an almost square composite driver which should actually work better than running just two per cabinet as the height and depth ratio will be closer to being equal. Regards Moray James.
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Old 8th December 2006, 02:35 PM   #8
Dag is offline Dag  Sweden
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moray james and everyone else:

You are right, no box is the smallest box! I do like the "W Frame Dipole"! It is a very clever design (I want to try one under my bed!!!)
But I have not heard one (yet!) so I do not know how they sound. I have heard the isobarics and I liked the sound. But I can't tell which one I like more. Has anyone tried both????

One advantage of a closed box (or isobaric) could be that the air in the box is linearizing the excursion of the woofer!? (Air pressure vs. volume is very linear) I think I red that somewhere.... But if you have 8!!! B139 that might not be an issue.

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Old 8th December 2006, 02:40 PM   #9
Mikett is offline Mikett  Canada
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Here's another idea. Use the four per side but use them in isobaric as well as opposed excursion. This will reduce the 2nd order distortion due to opposing cancellation effects. This will probably benefit the B139 greatly as the drivers from that era did not have the newer distortion reduction technologies that better drivers of today have.
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Old 8th December 2006, 08:06 PM   #10
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Quote:
Originally posted by Mikett
Use the four per side but use them in isobaric as well as opposed excursion.
Push-push push-pull

This is the most effective way to do it from a distortion & reaction cancellation... not so high cosmetically. Front woofer removed in the sketch.

Make the box as big as you need -- in this configuration a box modeled for a single driver supports all 4.

For instance a 96in line, 6:1 taper ratio. So=2.25Sd, Sl=0.375Sd. Zdriver at 32.25in. Stuff 0.5lbs ft from the top of the line 80in along.

Sd = 55in^2

(2.25+0.375) x 55 = 145 in^2 (total cross-section area for a folded once box excluding partions. -- that is a box ~ 14" x 14" x ~50" tall (those exact wxd would need juggling to fit the drivers.

dave
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