Kit built retransmission line....help.

[sumday]

I recently acquired a pair of speakers based on a kit design I think from Rogers.
The driver layout mimics Cambribge R50s, i.e. B139, B110, T27 and Coles 4001.
Although the cabs are in good shape and very solidly built...they are thick chipboard with a black Formica covering ala back of IMF TLS etc...sadly all tweeters are missing.
Being on a tight budget I cannot afford the crazy prices being asked for T27s and 4001s on ebay.

I was pondering a slight redesign, reverting to 3 way with some cloth Audax tweeters I have laying about.
A quick looksee on Amazon tells me reasonable Monocar xovers could replace the suspect 4 ways I have in the cabs.....these were hand made and are pretty beaten up.

The cabs are currently wadded with lambs wool supported on stringing, much of this is also in bad shape and I will have to ditch it.....would I replace with foam or modern wadding.?....I have access to both but the tranny tunnel is quite complex so glueing up will be a one time deal I guess.

These cabs are true survivors, I understand they have spent almost 40 years in the back of a garage with only a carpet cover for protection

They now look almost as new with new grille cloth and the Formica responded well to T cut and Turtle Wax....it's just the innards that need help!!

[walpurgis]

If it was me, I wouldn't buy the Monacor crossovers. They are unlikely to suit those drivers unless specifically designed to work with them. I'd look on ebay for a pair of second hand KEF Concerto crossovers which will match the drivers perfectly, put new caps in them and use those.

The Coles supertweeters can be introduced with a series capacitor separately if you really want them, they are not actually necessary, as the T27 extends to a claimed 30kHz and yes, it's probably worth holding out for some T27's.

You could try the Audax tweeters, but it may not be ideal. They are likely to sound bright.

[fatmarley]

Agree with Geoff, keep the original crossovers unless you know how to measure and design your own. If you don't, it's a steep learning curve and not cheap to buy all the measuring gear. An off the shelf crossover is unlikely to come close to a properly designed one.

I'd either put them back to exactly how they should be or sell the individual drivers on ebay.

[Macca]

Don't buy off the shelf crossovers. Keep the ones you have and replace the caps and anything else that looks dodgy.

As Geoff says you don't need the supertweeter. You can use the same xover it doesn't make any difference that the supertweeter is not connected in terms of the overall operation of the speaker.

I'd put the Audax units in and see how it sounds, I'll bet they will be fine. The tweeter doesn't do a massive amount anyway, the mid range is doing all the stuff in the audio band we are most sensitive to. IME of these old KEF based transmission lines (I have some IMF TLS50) they are on the darker side of neutral overall so a higher tweeter output than originally intended might sound subjectively better. Especially with no supertweeters.

You've got the tweeters already so nothing to be lost by trying them except a little time.


You need to replace the stuffing in the line with the same stuff, and put it in at the same varying density as the stuff you take out. It's a pain in the arse. I'd leave it unless it is really rotten


If the internal wiring is bellwire replace with some decent copper cable, doesn't have to be pricey but it's worth it. Can we see some pics?

[sumday]

Beavering away today I've sorted the xovers and dropped in some tweeters for a test play.
Bloody hell they go low, but the top end is well, soft. They currently seem shut in with no real treble detail...it's there but no sparkle.

Whoever built them knew his stuff but 40+ years in a cold/hot garage have taken there toll on the internals.
I've never really listened to a B110 midded enclosure before but now I get it....the vocal delivery just hangs in space with detail I've never heard in recordings I've known all my life.

Sadly my back is done in for now...the heaviest speakers I've owned and a proper two man lift.

I'd post pics but my efforts in the past have always failed.

[walpurgis]

Did you put new caps in the crossover? That may well bring them to life.

Just use Alcaps from Cricklewood Electronics on ebay.

[Lawrence001]

Would be good to know that there is no low pass element for the T27 in the crossover. Ie the Coles supplements it at the top, not supplants it. If it does it should be relatively simple to remove the low pass element with a bit of sage advice from here.

+1 on the new caps.

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