Please Help me Identify and Build 1980’s KEF Speaker Kit

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The secret to routering freehand is to use a very low power router. Fortunately that means a cheap one. Also use a sharp (repeat sharp) narrow bit and a series of very shallow cuts, (increasing the depth gradually) to reduce the forces which will tend to throw the router away from the proper line. Also move the router in the direction that tends to throw it inward rather than outward.

Cut the outer edge of the recess first as a narrow slot (say 1/4 inch wide) before cutting the hole with a jigsaw. This gives you support when you need it. Then cut away the surplus using the router.
 
tsnell said:

Enclosures will be separate TLs for left and right, along the lines of
planet10 (post 21). But undecided on the B110 and T27 arrangement.
Sreten can you please elaborate on “Mounting all drivers on a wider
baffle and a higher crossover frequency increases the nominal
sensitivity”, aren’t there major drawbacks for wide baffles
for high/mid freq drivers (baffle step etc)?

Hi,

If you look at the concerto crossover the T27 is run unattenuated.
If you look at the CS1A crossover you will see its run at ~ - 3dB.

The 3-way is ~ 3dB more sensitive than the 2way .....

Which should mean you cannot passively c/o the B139 low
to the CS1A as a subwoofer as it will be ~ 3dB too loud.

Unless of course you go isobaric (a la Linn) for the sub ....

A Plate amplifier for the subwoofer is the most flexible.

Passive subwoofer crossovers are a minefield.

Unless your friend is a bass freak I would steer away from a
massive bass enclosure, its unlikely to appreciated long term.

Making a good performing small box is a lot easier than a big
one, IMO the CS1A will surprisingly adequate on its own.

I would build a simple sealed isobaric subwoofer. I would
then try a stereo series 1st order crossover for each B139
and sattelite (sounds strange for isobaric but should work).
AFAICT this might work quite well for a passive arrangement.

If it does not work well then the subwoofer needs to go active.
There are all sorts of possibilities if you are capable of buiding
the preamplifier and power amplifiers, active also means any
subwoofer approach can be taken.

AMV8
You can add a subwoofer to it using the B139.
There is a design on the internet for that arrangement.

Could you post a link ?

:)/sreten.
 
Thanks for the input everybody and apologies for my slow responses on here (between uni, work and family lately I have not had enough time to get onto the forums – the project is still definitely going ahead, things will just be slow until trimester break). I don’t want to waste anybody’s time, so I probably need to do some more research myself before I ask too many more questions. I will fire this thread up again when it gets close to build time. Thanks again everyone.
 
diyAudio Member
Joined 2007
OOPS, My bad; OP was in Newcastle, these are in Canberra, although that is only a couple of hours in a fast car.

$200 per driver is too much, for that much you could buy something new, lower Fs, greater X-max and higher thermal rating, I like b-139s, but not when they cost more than $150 a pair which is what I thought was a fair price when I sold mine.
 
frugal-phile™
Joined 2001
Paid Member
Moondog55 said:
han $150 a pair which is what I thought was a fair price when I sold mine

If we use USD and they are in the box as these are, i'd say that is about right... but if you are a guy who loves his IMF TLS80s or Refs, and in need of a spare it might not seem so steep.

The local dealer won't sell used Tangent TM3s because he can get way more selling the drivers to guys who blow up their Linn Saras (the TM3 is a better speaker IMHO)

dave
 
My suggestion is to go for original KEF recomended enclosure:

KEFKITs and DIY Designs

You should take a look @ this enclosure:

Anatomy of the Kef Concerto

An externally hosted image should be here but it was not working when we last tested it.


This is cabinet specs:


Anatomy of the Kef Concerto

Vented speaker box with three drive units.

Specification: (source KEF C Series Leaflet 10/73/C- 3)

Dimensions: 711 X 432 X 305 mm

Internal Volume: 62 litres

Weight: 25.4 kg

Nominal Impedance: 8 ohms

Specific Frequency Response: + or - 3db 35-30,000 Hz measured at 1m on the axis of the HF unit in anechoic conditions

Dividing Frequencies: 400 Hz and 3,500 Hz

Sensitivity: 9.5 watts into 8 ohms produces 96 db at 1 metre in anechoic conditions.

Rated maximum power: 50 watts

Room size: Up to 280 cubic metres
 
Hi, Very interesting!!!! I have the same set of speakers for years now. I bought them second hand. The enclosures are self-build but not well designed. So I consider to build new boxes. I wonder how the horn design worked out for you.

I'm interested in a copy of the hifi news and record review article as you showed in the pictures. Do you have a design of the Original Concerto as well.
(if some other reader has a copy of these articles for my you make my day as well)

thank you,

Willem
 
My neighbour used to have the KEF Concerto's.

I cleaned them up for him one day. Just tidied up the wiring to fresh metal really. Sounded pretty good afterwards. We listened to "Graceland" by Paul Simon. That smooth, if unexciting, old bextrene sound.

FWIW, Wilmslow Audio and Falcon Acoustics offer upgraded crossovers more along later KEF ideas.
 

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Kef B200 transmission line subwoofer

I didn't read the whole thread, but if someone is trying to replicate the Kef B200 stereo transmission line subwoofer...I own an original. Someone can take measurements. It came as a sub satelite system sold by Fried speakers. I don't remember it been sold by Kef directly.
As far as the grand daddy sub of the era, the coffin sub with the kef B139, I heard one and almost purchased it, but didn't because of its size. I wish I had it now.
 
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