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Moondog55 3rd November 2007 11:31 AM

Dual B-139's
I may soon be aquiring a second pair of KEF B-139 bass drivers, does any-one have plans or a link to a design using pairs of B-139's in parallel??
I do not have much floor space so would prefer to go tall rather than wide, midrange will be Vifa I have a quad of P-11 and I will Bi-amp these, assuming I ever get time to build that is.
Sealed or transmission line is what I am thinking
Regards Ted

Moondog55 4th November 2007 04:14 AM

OK; here is the question; do I try and design a dual T-line box with seperate lines or do I combine both drivers in one box using Vas X 2?? As I do not like low impedance loads I would consider running another set of compatible drivers in series in seperate sealed box/boxes.
What about a pair of 8 inch 8R woofers in series before the KEF's, or a pair of 6.5 inch 4R-mid-woofers or a single largish 4R sub wired after them?? I have several pictures in my head but I am having trouble getting them down on paper.
For those Aussies out there I do have some of Jaycar's little carbon fibre 165mm mid woofer but as these have a fairly smooth top-end it seems a waste to cross them over so low ( 250-400 Hz)
Is the thought of sittng a pair of B-139's on top of a 12 or 15inch sub box a little over the top?
Visaton have some cheapish 8inch woofers that may do the job in series
Wired in series -parallel this would/should be an easy amplifier load and reasonable power handling

planet10 4th November 2007 04:35 AM

Scott & i did up a TL for the B139. It could easily be adapted for a push-push TL.

Minimum footprint would mean unfolded (ie a wegde shape). You'd have to have 9' ceilings to leave it unfolded thou.


Moondog55 4th November 2007 05:08 AM

Dave the web-site has been down for days, it was the first place I went looking, I have seen the pix of Andy's Manhattan tower and GeeVee has sent me the plans for the Bailey clone but I was thinking of something bigger.
But heck I still haven't finished the "Tardis" front and back subbie yet, I get sidetracked into new projects all the time.
I was thinking about a simple folded line but we only have 8 foot ceilings here.
Performance of the B-139 in a simple sealed box is still reasonable but when I was a younger man in England I went to the audio show at Heathrow and still remember hearing IMF studio monitors for the first time, we have access to much better mid-range drivers and tweeters now, but it is my memories ot the bass of that particular speaker I rememer most vividly.
From what i have read and heard it is the long term power handling of the KEF/ELAC driver that is the biggest drawback, which is why I was considering multiple drivers.
I would even consider giving these the front and back treatment but using the additional woofers in seperate sealed boxes as a base, I have 8 1/2 foot ceilings, and the room is small but 'L' shaped and all walls have drapes and heavy wall hangings floor is polished and the ceiling is untreated plaster board.
These speakers are going to have to do double duty as music and HT mains L&R
All comments and advice appreciated

planet10 4th November 2007 06:24 AM


Originally posted by Moondog55
Dave the web-site has been down for days,
OK i fixed that. Earlier in the week it was maintenance where i host my pictures, today it was my server.

The B139 box isn't up anywhere yet. Here is the single Triangulated line -- a TTL won't work for your ap.


pinkmouse 4th November 2007 08:04 AM

I wish I had a second pair. I seem to remember seeing a tiny H frame OB design that used a pair somewhere here or on the web, German design IIRC, they had so little wood involved it might be fun just to knock up a pair and see how they sound.

If you search for my thread on the B139, Scott posted an interesting MLTL that was a bit smaller than Dave's true TL and might be an alternative. I still haven't decided which to build. ;)

planet10 4th November 2007 06:11 PM


Originally posted by pinkmouse
I wish I had a second pair. I seem to remember seeing a tiny H frame OB design that used a pair somewhere here or on the web, German design IIRC, they had so little wood involved it might be fun just to knock up a pair and see how they sound.
Isn't that how Gradient started out, with dipole woofer support for Quads?


pinkmouse 4th November 2007 07:13 PM

Dave, I think you might be right.

Oh, and the PDF for that dipole sub is availble from here:

planet10 5th November 2007 01:11 AM

2 Attachment(s)
The mid & tweeter cabinet could be designed to sit on the angled face....


Moondog55 5th November 2007 06:51 AM

I like the look of those, how much clearance above the open throat do you need ??
Also is there a program that can simulate the effect of a first order high pass at 25Hz (ie woofer resonance ) in TL's
I am beginning to think that a Q equals 1 sealed box using that system may give me what I need in this room

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