Plans for TL Cambridge R50s/HiFi Answers version

[Royston Vasey]

I have an old pair of KEF Concertos that I refurbished about eight years ago putting in new tweeters and good quality crossover from Wilmslow Audio. While they sound OK I have always fancied using the drivers (KEF T27, B110 and B139) in the Cambridge R50 TL speaker. HiFi Anwers did the plans for a version of these speakers in the 1970s.

I will shortly have the workshop facilities for making these complicated speakers and am looking for a set of plans that I can use to build them from.

Has anybody any idea where these would be obtainable? I note there is a book on speaker design that mentions projects from the 1970s but do not know if it covers this sort of design.

RV

[qwad]

Hi , yes I can help, gimme your email address & I can scan and send it to you+ a couple of others inc the bert webb version as the hi-fi answers one was designed by chris rogers, which are essentially the same and are in an old badger components catalogue I still have lying around and use a similar x/over so you can use all your components without having to buy any others except the coles 4001g super tweeter which I am sure is still available from coles electroaucustics [ who I'm not sure if they have a website] though falcon should be able to help'or wilmslow?or you could use the celestion hf 2000 in it's place I believe.... and it was a much better unit than the coles/ itt 4001..... cheers; TC

[sreten]

Going back a bit here, the Bailey design also used the same drivers.

The Hi-Fi Answers design is called the Pro9-TL I believe.

The seminal design using these drivers is Linkwitz's active 3-way,
which was the basis for the passive KEF 105's.

And I'm sure there are IMF designs not too far away.

JMO but bass obviously will be better, mid/treble ? why better ?

And you need to make sure that if you buy crossovers
they are for the correct versions of each drive unit.

KEF were (in)famous for using versions of drivers in their speakers
that were not made available to home constructors, and it is also
sensibly rumoured the units made available were production
rejects, AKA the Constructors series.


Years ago, and I mean it, I converted a KefKit3 (the same
as the Concerto) to a smaller satellite stood on top of the
original bass enclosure, other than not retuning the bass
reflex, I still think this is the sensible option, midrange,
imaging and detail improved immensely.

From what I remember a prominence in the B110 around 1k
is actually improved by the much smaller baffle, a premise
that at the time KEF would not confirm but did not deny.

If your interested I can describe further details.

sreten.

[qwad]

AAAHEM! I beg to differ the pro 9tl was a popular hi-fi project also by mr c. rogers, but using the peerless ko 10rmf something or other sealed back midrange unit albeit in much modified form the beauty of this design was the flexibility it afforded in the use of tweters by very simple component changes one could use the isophon kk10 or a seas 1 in soft dome that was current at the time a model I cant recall off the top of my head right now... agreed kef pulled a few fast ones in the past [and having lived with b110's in the past in the r. fris 3 way daline and the complexity of the bbc ls 3/5a x/over bears witness that this driver has it's faults just like any other] and so has everyone else witness the current controversy over the accuracy or otherwise of peerless t/s specs etc , etc, and so on..... cheers T.C.

[sreten]

Originally posted by qwad
AAAHEM! I beg to differ the pro 9tl was a popular hi-fi project also by mr c. rogers, but using the peerless ko 10rmf something or other sealed back midrange unit albeit in much modified form the beauty of this design was the flexibility it afforded in the use of tweters by very simple component changes one could use the isophon kk10 or a seas 1 in soft dome that was current at the time a model I cant recall off the top of my head right now... agreed kef pulled a few fast ones in the past [and having lived with b110's in the past in the r. fris 3 way daline and the complexity of the bbc ls 3/5a x/over bears witness that this driver has it's faults just like any other] and so has everyone else witness the current controversy over the accuracy or otherwise of peerless t/s specs etc , etc, and so on..... cheers T.C.

agree- the Pro9-TL was a kneejerk that was wrong, still
trying to remember the TL design using two HF1300's.

The problem with the LS3/5A B110 was the required specs
ended up being to one side of the bell curve, i.e. lots of rejects.

But I still think a large and complex TL enclosure will not improve
the Concerto's mid / treble performance one iota, and that such
effort is misguided.

sreten.

[planet10]

Originally posted by sreten
still trying to remember the TL design using two HF1300's.

That would be the atkinson... i never did finish this 3D

Originally posted by qwad
I beg to differ the pro 9tl was a popular hi-fi project also by mr c. rogers, but using the peerless ko 10rmf something or other sealed back midrange unit

The HiFi Answers article i have says B139/B110/T27/Coles 4001. BTW there were 2 versios of the Chris Rogers design. Remo is still selling a Version 7 of this design.

My feeling would be that given we have much better TL modeling tools would be to grab Matin King's software and generate a new line for the B139 -- i'd also TL load the B110... ideally an active XO at about 200-300 Hz between the B139 & B110 (point choosen so as to deal with baffle step).

Of the classic lines, Bailey's Triangulated TL was always my fave.

dave

dave

[sreten]

Originally posted by planet10

Of the classic lines, Bailey's Triangulated TL was always my fave.

dave

His expedient of mounting the B110 in the line never did catch on......

sreten.

[qwad]

AAH, but the idea did catch on with monitor audio in the 70's a 3 way model I cant recall designed by one Martin Colloms one of the founders of Monitor audio placed a bowers & wilkins sourced mid unit without any sub enclosure to isolate it from the main br chamber of the bass driver at the time claiming that there was not much pressure influence on the mid from the bass unit which had a wonderfull and open character.... cheersT.C.
PS; thanks planet 10 for posting that diag saves me having to dig mine

[planet10]

Originally posted by sreten
His expedient of mounting the B110 in the line never did catch on......

That was never a good idea ... i always built these things with the B110/T27 in LS3/5A inspired sats... i even dug out a set of boxes i'd cut for these kind of sats and repurposed them when i got back into hifi after my hiatus...



Note: i don't know if i was an influence, but Bud Fried started making his sats a similar shape, after i'd had clients build Fried Hs with the "pyramidal" sats.

dave

[planet10]

Originally posted by qwad
thanks planet 10 for posting that diag saves me having to dig mine

I have the entire article pdfed so it is easy to find.

dave