Just to follow on from my post about the crossovers, thought I'd tell you
what I've been up to.

Bought a total of three LS 5/8 with BBC modified Quad 405s a few months
back. This design is post my time at the BBC, so I'd never used a pair for
work monitoring - but had been impressed on the occasions I'd heard them.
However living with a pair for day to day use is often not the same.

Also, on chatting to some retired BBC TV sound supervisors at a reunion,
it became clear the 'pop' boys loved them, but drama ones didn't.

Which is what I'd been finding. Sound great at high levels on most types
of music, but not good at low levels - and more so on speech at 'natural'
levels. And since they are to be used for everything including TV and
radio, not so good for my use. If I had to put a finger on it I'd say
something not right in the midrange. The design uses a 12" bass unit to
2kHz, and a single dome tweeter above that. The bass is superb, though.

AB tests between a single LS 3/5a and a single LS5/8 showed the mid range
voicing to be very different at normal domestic listening levels. So they
both couldn't be correct. ;-)

Now the B110 was always highly regarded so I decided to fit then to the
5/8 covering the critical midrange of 300 - 3kHz. Falcon Acoustics make
new FB110 units which they claim are as near identical as possible. Adding
an extra amp to the 405 and of course a new crossover.

Which is what I've done.

I made a new baffle and moved the tweeter to one side with the B110 on the
other side in its own 0.004 cu.mtr enclosure - this is what KEF
recommended for mid range use. When I do the other one it will be mirror
image.

Fitted a Maplin 150w MOSFET alongside the treble amp in the 405, a
separator PS for the crossover between the mains transformer and smoothing
caps, and the crossover where the BBC one was - alongside the other 405
power amp. (My thinking was the original 405 PS should be ok as I'm not
actually expecting more total 'watts' out of the system.

I'm listening to the prototype at this minute here in the worskshop and am
very pleased with it. (I used the third speaker as a prototype, so still
have the main pair in the living room.) Doing an AB between it and a 3/5a
shows them to be very similar in the midrange.

I have lots of pics I can put on Photobucket if anyone's interested.

--
*He who laughs last, thinks slowest.

Dave Plowman London SW
To e-mail, change noise into sound.