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Brian Knight 8th May 2006 12:08 PM

Crossover for older KEF drivers
This is probably a question for old-timers with long memories!

I have a pair of KEF B110B woofer/mid-range drivers, T33A tweeters and 'Concerto' crossovers. These are all left over from an upgrade to a transmission line speaker system in which I decided to retain the KEF B139 woofers but upgraded the midrange and tweeter units and installed newly designed crossovers.

It occurs to me that that it should be possible to use the KEF B110B and T33A drivers in a system similar to the old BBC/Rogers LS3/5a monitor speakers. However I cannot find a crossover design for this combination of drivers or even cabinet plans. Can anyone point me to cabinet plans and a proven 2-way crossover design for the B110B/T33A combination in a small sealed enclosure. If not, would it be feasible simply to use the Concerto crossover with the components required for the woofer low-pass and mid-range high-pass filter sections removed?

richie00boy 8th May 2006 12:36 PM

The crossover might not be right for a different width of cabinet, and the midrange might be attenuated as well. There was a design called the Super 7 or something - a sealed 7 litre cabinet. The Speaker Company here in the UK resurrected the design but they went bust a few years ago.

Try Falcon Acoustics in England.

sreten 8th May 2006 01:24 PM


Falcon possibly sell such a beast, as their 3-way networks
for XXXX/B110B/T33A, are on two boards, B/M and M/T.
I say possibly because baffle step compensation may be an issue.
However I'm sure Falcon would give good advice.

Which I think answers your questions, that is the concerto bits
can be used, but in doing so there would be nowhere near the
amount of BSC (baffle step compensation) as in the LS3/5A.

Probably be just as good as a pair of Linn Kans though.

Wilmslow Audio used to sell a B110B/T33A croosover and plans.

I'd say it depends on the speakers intended use.

For rear speakers on a wall, simply copy the LS3/5A dimensions
and use the concerto crossover components - should be fine.

For front use on open stands you would need a LS3/5A type crossover,
for the cabinet again copy the LS3/5A dimensions but ~ 20% deeper.

For detailed cutting lists just copy any small loudspeaker plans e.g. :

For a sealed box the B110 would be fine in a box anywhere between 4L and 10L.

I'd recommend 6 or 7 Litres for main use, 4 to 5 litres for rears.


jackinnj 8th May 2006 02:40 PM

Consider the DALINE + B110 -- used a B110 and T-27 -- you should be able to find plans on the web -- this was a very nice use of the B110. Obviously you will have to mod the xo somewhat for the T-33.

This is one of the first speakers I built from scratch -- May 1975 HiFi News and Record Review if memory serves correctly.

I am sure that the boys in Canada could make good use of their Mathcad program to improve the design. It was a very nice setup.

sreten 8th May 2006 04:30 PM


Originally posted by jackinnj
Consider the DALINE -- used a B110 and T-27 --

if my hazy memory of the daline crossover is correct, the mid/treble
section from the concerto will be more or less equivalent. That is
the c/o has no baffle step compensation and the Daline (which has
an ~ 12" wide x ~ 6" deep footprint) should be used against a wall.


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