What are these? Rogers RM-40-TL Mk3???

SimplySound

Kent Engineering & Fondry
Subscriber
WOW!!! Ok, I think these are DIY, but I just don't know. They are listed around the internet as "Rogers RM-40-TL Mk3"...

They use some really interesting vintage drivers!!!
KEF B139 SP1044,
KEF B110 SP1057,
Audax HD13D34H,
Seas H437

Are they really built by Rogers in England? Were they a Kit offered by them? Should this be added to the "Holy Grails"? Enquiring minds want to know...:scratch2:

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Uhmmmm.... think I found the answer on a Dutch site....

Yes: this misunderstanding was to be expected!

This is the REMO-DIY-transmission systems, "Rogers RM40TL Monitor" or "PRO 9 TL" were based on a design by Chris Rogers (not Jim Rogers of BBC Fame)', in an article published in "HiFi Answers".

To quote from Chris Rogers on the revised Pro9 TL

"In the three years or so since my original TL design appeared in print (HiFi Answers) there has been considerable advancement in drive unit design and, of course, we have 3 years of further knowledge & understanding of the TL principal. This then is the culmination of the last three years presented as a new design. "

In the early version the T27 was not considered to be extended enuff so a super tweeter was added. The newer version used a more extended tweeter and dropped the super-tweeter (as well as using a self-enclosed midrange)
"
 
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Found more...

I had always been impressed by the sound from loudspeakers using the "Transmission Line" principle, namely the Cambridge Audio R50 design. Having first listened to the R50 loudspeakers at a talk given by Reg' Williamson, to the Norwich Tape Recording Society, back in the early 1970's. A DIY design published in Hi-Fi Answers, by Chris Rogers, enabled me to construct such a pair of loudspeakers at a reasonable cost. The bass (B139), mid' range (B110) and tweeter (T27) drive units, were manufactured by KEF, whilst the super tweeter (4001G) came from ST&C. The latter, ST&C, are probably better known for their ribbon and dynamic microphones, rather than loudspeaker drive units. The task of constructing these loudspeakers, was awesome, with a high degree of accuracy required in cutting the wood for the transmission line and mid-range enclosure. It would also be a very tedious task, what with using over 100 wood screws in each cabinet and under sealing all internal surfaces (some being very difficult to access). Not forgetting, the "Stringing up" of the various sections of the transmission line, ready to hold the critically weighed lambs wool, for acoustic damping. I found out some years latter, that a very good friend, and work colleague, namely Peter Harradine, had also constructed the same loudspeakers So it was interesting to compare notes on construction problems that we had found, and of course, how they actually sound. My DIY transmission line speakers are still in regular use today, some 30 years since their construction. In all those years, other than rewiring the drive units to the cross-over PCB, I have only ever replaced one of the KEF B139's, that failed by going "open-circuit".

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Found more...

I had always been impressed by the sound from loudspeakers using the "Transmission Line" principle, namely the Cambridge Audio R50 design. Having first listened to the R50 loudspeakers at a talk given by Reg' Williamson, to the Norwich Tape Recording Society, back in the early 1970's. A DIY design published in Hi-Fi Answers, by Chris Rogers, enabled me to construct such a pair of loudspeakers at a reasonable cost. The bass (B139), mid' range (B110) and tweeter (T27) drive units, were manufactured by KEF, whilst the super tweeter (4001G) came from ST&C. The latter, ST&C, are probably better known for their ribbon and dynamic microphones, rather than loudspeaker drive units. The task of constructing these loudspeakers, was awesome, with a high degree of accuracy required in cutting the wood for the transmission line and mid-range enclosure. It would also be a very tedious task, what with using over 100 wood screws in each cabinet and under sealing all internal surfaces (some being very difficult to access). Not forgetting, the "Stringing up" of the various sections of the transmission line, ready to hold the critically weighed lambs wool, for acoustic damping. I found out some years latter, that a very good friend, and work colleague, namely Peter Harradine, had also constructed the same loudspeakers So it was interesting to compare notes on construction problems that we had found, and of course, how they actually sound. My DIY transmission line speakers are still in regular use today, some 30 years since their construction. In all those years, other than rewiring the drive units to the cross-over PCB, I have only ever replaced one of the KEF B139's, that failed by going "open-circuit".

diy%20transmission%20line%20loudspeakers.jpg
 
I first heard the Pro9TLs in Southampton in the early 70s. I considered they were the best speaker I had ever heard (not many at that stage). So I built a pair of the DIY kits featured in Hi-Fi Answers. Kept these until the mid 2000s, eventually selling them because I wanted to build some new ones with an updated crossover, better wood work and a decent paint job. Original cost was 100 pounds. New project NZ$2500 (1200 pounds). Would I change? A pair of Sanders Sound Systems 10b or 11s would do the trick. But until the pennies are saved this is where I am going to stay, I don't think there is anything else that can compare for the money.
 
There is a past thread about those speakers on AK.
Since many of the inserted photos are not available on the new AK forum the thread will be difficult to find.

IIRC they were a DIY kit. offered in magazine adds.
The tweeter placement above the Kef B110 is too far in distance for a flat response with the crossover used.
 
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