What to do with KEF B139s and T15s? A TL?

diyAudio Member
Joined 2007
I lusted after a set of traditional TLs with the B-139 when I was younger but no longer.
But whatever you do don't use them over 300 Hz and going down to 250 or even 200 would work better.
Are you going to Bi-Amp still? Why not use the triangle box from Dave as-is and place a set of reasonable, small 2-Way boxes on stands right next door?
Even a mediocre set of cheap speakers can sound a lot better when relieved of bass duties. My favourite combination for ease of cross-over construction is no longer available but a smallish driver in a small sealed box with a good flat response and a tweeter that can get by using a simple first order XO shouldn't cost the earth.
Do you have the DXO and the amplifiers already? If so what are they?
 
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I have speakers with the B139s, and they work well.
They are in braced sealed boxes the same size as the Linn Isobariks, about 70L I think, with some good wool stuffing.
I would do the usual analysis of their characterists into a 70L sealed box of course, but they work well for me in my 'half barik', and using an isobarik crossover.
The B139 is good for TLs, and I did have them in huge TLs many years ago, but didn't seem to be any better bass with that, in fact I prefer the sealed box.

Also the B139s have a 1kHz 'ring' IIRC, so use a good crossover. They are however deeply cool, one of the most interesting drivers from the 1970s :)
 
The most thunderous bass I have ever experienced was using a pair of 139s in a sealed box about 2'x2'x1' using a Linkwotz Transform equaliser to extnd the response below the closed box resonance.

No speaker or sub, diy or commercial has ever come close.

The satellites used a B110 & T15, also driven via active crossovers.
 
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But whatever you do don't use them over 300 Hz and going down to 250 or even 200 would work better.
Sure - I think that's a given - 200 sounds much safer.
Are you going to Bi-Amp still? Why not use the triangle box from Dave as-is and place a set of reasonable, small 2-Way boxes on stands right next door
I think bi-amping is the way to go - certainly the components for a passive would cost a fortune at 200Hz. I had thought about the satellite option - but instead will probably mount a Mark Audio driver (in a separate wedge shaped box) on the sloping face. Again, visually, it would appeal to my better half.
Do you have the DXO and the amplifiers already? If so what are they?
I ordered two BRU5 Class D amps from Alibaba recently. These are a steal (although PSUs are not included in the price) as they have a DSP chip. They use the same software as the Arylic plate amp and I assume therefore the same chip. There's a lot of effects not really useful (autotune etc) but the parametric 10 band EQ has settings for shelving filter, XO, notch etc.

I've been experimenting with these on my original Leak Sandwiches - more or less recreating the redesigned XO that a guy in Melbourne Audio CLub did 20 odd years ago. The improvement over the original (with Stephen? Spicers) XO mods (which are ingenious) actually make the Sandwich listenable.

I really bought the BRU5s for experimenting with - but could perhaps use them permanently in the B139 speakers (whatever they'll be called). Or build the active XO that Rod Elliot has designed with a Class D for the B139s and something else for the FR driver. Or use the Arylic plate amp

For tweeters I 'll play with the KEF T15s as you suggest with a simple XO on them - even if I've more or less destined them for my Sandwich rebuild as the Leak sandwich mid/tweeter is a tad like the B139 - good if its used within its limitations.

I'm treating this really as a learning experience - a lot more educational fun than simply buying a B139 TL kit from Falcon.
 
The most thunderous bass
My introduction to the B139 was with Pink Floyd's The Wall, must have been early 1980s, with my uncle's system (perhaps even the TLs, can't recall), they can really create impact.
Only a full 12" Eminence has been able to get close to the drama of the B139 in that track :D.

Of course we had Vinyl back then, but to my surprise some of the Vinyl has better dynamics that them CD versions of songs - odd given the supposed 25dB(ish) advantage of the CD, but perhaps due to the poor low level performance of CDs.

But the combination of Vinyl and B139s I still remember to this day :)
 
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The B139 is good for TLs, and I did have them in huge TLs many years ago, but didn't seem to be any better bass with that, in fact I prefer the sealed box.

Also the B139s have a 1kHz 'ring' IIRC, so use a good crossover. They are however deeply cool, one of the most interesting drivers from the 1970s
They'll be XO'd at 200 or so. Interesting that you preferred them in a IB box. I've measured the TH parameters of both 139s now (having worked out how to use REW with a laptop) and the measurements more or less agree with each other - which is all to the better. I'll plug those results into WinISD and see what happens. For now though I'm committed to the TL design - simple because I've always wanted to do that. My dad was a KEF fan (and these 139s were his) and I grew up with his friends building all manner of speakers with the 139s. From my perspective it';s a bit of a sentimental journey.
 
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My introduction to the B139 was with Pink Floyd's The Wall, must have been early 1980s, with my uncle's system (perhaps even the TLs, can't recall), they can really create impact.
My dad had several friends in the late 60s and 70s who would turn up with amps they'd tweaked or built, speakers, LPs etc - a fav was definitely the 139. They all seemed to wear tweed jackets with leather elbow patches, smoke pipes and have pockets bulging with misc resistors, valves, mullard transistors and the like. The coal fire would be burning in the grate and they'd demonstrate their latest tweaks/builds and discuss them in a fug of St Brunos. Sadly they're all long dead now but I remember their kindness in giving me components so I could muck around with a soldering iron. In part this little project of mine is about reliving those days.

I think these events (long before internet forums) are now called bake-offs?
 
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Of course we had Vinyl back then, but to my surprise some of the Vinyl has better dynamics that them CD versions of songs - odd given the supposed 25dB(ish) advantage of the CD, but perhaps due to the poor low level performance of CDs.
Now that's interesting. I've always had an interest in recording techniques stemming from the fact that two of my dads tweed jacketed friends were recording engineers - one for Decca who got me a work placement. I gather that modern mastering increasingly uses heavy compression - partly because the companies consider that people listen to most music in their cars, and partly because compression has an immediate audio impact of sounding more impactful - although its something that gets tiring very quickly. These companies today are in a desperate state (especially in the classical world) and wish to find ever new ways of reselling their back catalogues (so making us buy the same product several times over) - so box collections are prevalent (using any cobbled together 'theme' they can think of) and by using compression that make it sound 'new'. By way of a test I took a couple of albums where I have both the original LP pressing and a CD reissue and measured the dynamic range of each. In both cases the dynamic range was lower on the CD than the LP. For that reason I am NOT going to get rid of my LP collection which is now three generations long!
 
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That's interesting as that's something I wanted to build at some stage. Can you point me to a source for that?
Rod Elliot makes a pcb for the Linkwitz transform:

https://sound-au.com/project48a.htm

This is the system I built I thik it was featured in Wirless World in the 1970-80s.
https://www.linkwitzlab.com/sb80-3wy.htm

On page 13, he shows you how to calculate the variables.

The B139s crossover at 70Hz and mine were built into a large coffee table, down firing.

Actually he used T27 tweeters which I also used, not T15s.

My satellites were suspended from the ceiling at head height on chains although I would use shock cord these days.

Thanks to better quality opamps and passives, it's still a viable design, and for me, avoids digital signal processing, although I probably would use a Clsss D amp + switch mode psu for the B139s. I used five Mapin 50watt amps (not the Mosfet version) and a 500va toroid that dimmed the light when I switch it on.
 
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frugal-phile™
Joined 2001
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My introduction to the B139

IMF TLS80, KEF Concerto, and many DIY builds. I sold literally 100s of them. Haven’t seen any back. Just 16 of the B200.

Of course we had Vinyl back then

Slowly sorting my records and just ran across the case i carried around 20 or so albums for testing/trialing systems hen on the road. And memories of many Linn Sondeks.

dave
 
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a fav was definitely the 139

:

In both cases the dynamic range was lower on the CD than the LP!
For me KEF seemed to be at the centre of HiFi advancements, and the 139 was a thing of new wonder :). I had a couple in reasonable shape in my half-bariks, then one day at the local tip, a few years ago so a bit more casual and democratic then, I peeked under the grilles of a couple of shonky looking homebuilts - and for £5 had them, with their immaculate pair of untouched B139s on them :D
I sold the old pair on, to a guy in Kentucky, USA :).
The B139 and B110 seemed the height of tech, and even today I often hear far worse in shops.

Today I was in a charity shop and there was a pair of old Wharfedale Dovedale 3 speakers sitting there (PM me if anyone near Cambridge wants to know the location, but they wanted £125 which is quite steep IMO), which reminded me of what my dad had at the time.

LPs have a good low level signal, yes there's hiss and pop, but being analog, there's almost infinite resolution. 'The Wall' was particularly dynamic, and the quiet bits on the LP were of good quality.

The issue with the CD, in my view, was really the format IMO: A linear 16 bit number, to describe a logarithmic level. Not smart. A 16 bit float would have been better, 24, perfect; the problem being that at low levels there's very few bits involved in the signal, i.e. the resolution is very low, 3,4 or 5 bit audio: not as good as a slightly hissy LP when turned up loud :)

So to make a CD sound good, in general they end up with less dynamic range than the old vinyl. That's my view anyway, which I think is shared by all those new buyers of Vinyl out there !

I still have the original Wall LP I bought in 1979, but not quite organised enough yet to sort out a suitable player in the living room! The 1970s and 1980s were IMO the height of fun in HiFi.
 
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frugal-phile™
Joined 2001
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This is the system I built I thik it was featured in Wirless World in the 1970-80s.

Yes WW. I still have the original copy i got in my official KEF blue binder that promoted diy builds. Inspired people to hang their speakers, never heard or saw such a build. It did help sell a few dB Systems XO.

dave
 
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Reading my mind now?
Possibly! I just think that shape a) fits and b) 'counterpoint's your wedge - if that's not being too arty-farty. It also gives my wife scope for a colour scheme.

I was thinking of a sealed box at .707 (I'm confident of dealing with that).

In case I obtain the second pair of 139s would one MA driver be 'balanced' enough against the two in push-push? I note your plan said there was a gain of 3dB for the two. There are SPL figures for MA drivers but nothing I can see for B139s.
 
then one day at the local tip, a few years ago so a bit more casual and democratic then, I peeked under the grilles of a couple of shonky looking homebuilts - and for £5 had them, with their immaculate pair of untouched B139s on them
Lucky sod ;-) Why do people throw things away? I had a perfectly good Mullard 5/10 amp that my dad threw away after I left home - on the grounds of 'you didn't want that old mono thing!'
The 1970s and 1980s were IMO the height of fun in HiFi.

...and I think the 60s. There was a lot of ex-military surplus stuff around - oscilloscopes, radios, components etc that the tweed jacketers were constantly playing around with because it was dead cheap.
 
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frugal-phile™
Joined 2001
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You are biamping. But if you have 2 (bipole) you might need to reorient them as they ideally will be pulled out from the corner, and work best if firing sideways.

With a single i imagine that the B139 is front-firing… we had some issues with the single side firing driver in Tysen V1 and i tend to avoid that now.

To triangles in different finishes with a smaller one mounted on the angled side (wish i coukd draw a picture).

With 4 you could always build 4 cabinets, they can be stacked as a bipole or spread out in the room to fight room modes acoustically.

dave