Calling any Cambridge Audio R50 owners

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Giraffe

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Calling any Cambridge Audio R50 owners
« on: 21 Apr 2021, 03:32 pm »
I own a pair of Cambridge Audio R50 transmission line loudspeakers.  While they are good loudspeakers, I think that they would benefit from one of Danny's level 3 overhauls whereby he has the loudspeakers in his possession for test and measurement and re-enigneering.  Being in the UK though means that sending the loudspeakers to him is not feasible.

My idea is this: if there are any R50 owners who would like to have their loudspeakers overhauled by Danny then I will pay (subject to an estimate) for that in order to be able to buy the upgrade package for my own loudspeakers.

Not sure if the R50 was every exported across the pond, but if you have a pair and would like a free upgrade the let me know and maybe we can work something out.

Giraffe

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Re: Calling any Cambridge Audio R50 owners
« Reply #1 on: 23 May 2021, 06:31 pm »
Guess not then.

Were the R50s not exported to the US?

I know that the best results can only come from measurement and test.

subsonic1050

Re: Calling any Cambridge Audio R50 owners
« Reply #2 on: 23 May 2021, 08:43 pm »
Hi Giraffe - I was curious so I did a search. In order to find any Cambridge R50 speakers for sale I used Hifishark - there were none. I checked expired posts and there have only ever been THREE. Ever. The last one was in 2016. I'm not a speaker model expert but it does not seem to be a common speaker model - at least not in the United States from what I can see. Also, the speakers are a 40 or 50 year old design, is that the case? I wonder how your surrounds and things are holding up in addition to the crossover parts.

planet10

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Re: Calling any Cambridge Audio R50 owners
« Reply #3 on: 24 May 2021, 05:00 pm »
The R50 was also a diy project in Audio Amateur/SpeaerBuilder. Also the same as first of the Pro9TL.

A good XO rework could make remarkable improvements.

http://p10hifi.net/TLS/downloads/Pro9TL-1.pdf
http://p10hifi.net/TLS/downloads/Pro9TL-Mk2.pdf

Lowering the B110/B139 to 200 Hz to help deal with teh 1kHz resonance in the B139.

And one could take them up a notch by replaceing the B110 and up with a good full-range and bi-amp 200-300 Hz. Way more seemless with really good bottom.

The B139/B110 are not known for having failed surrounds. But those 50 year old caps will be long dead.

dave

planet10

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Giraffe

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Re: Calling any Cambridge Audio R50 owners
« Reply #5 on: 25 May 2021, 07:50 pm »
Thank you everyone for your replies.

These particular R50s are from 1976, so 45 years old!  Not quite as old as me ;)

So they were exported to the US but probably in very small numbers and I expect that most have been scrapped by now.  They do come up for sale here in the UK every now and then.

A previous owner replaced the crossovers with Falcon Acoustics Super Power units:


So these R50s are not suffering from dead caps and the like, but the Falcon Acoustics crossovers are not that great to my eye: a PCB, ferrite-core inductors, cheap resistors and electrolytic caps.  I could reverse-engineer a schematic and build new point-to-point crossovers using audiophile-grade components but that doesn't work if the circuit design could be improved.  These Falcon Acoustics crossovers do have a different schematic to the originals and change the crossover-point of some of the drivers (I do not remember the details).

I do not want to spend $$$ on new crossover components only to reproduce a circuit design that is non-optimal.  I wish I knew how Falcon Acoustics arrived at their circuit design.  Maybe I'll just give them a call and ask!

The surrounds of the all the drivers seem to be in good condition, remarkably.

The reason for all of this is that I think that they have much more potential to be released from the design.  The bass has a solidity I have only every heard from transmission line designs and correctly-recorded vocals just sound wonderful.  As I write, Ella Fitzgerald is actually in my sitting room.  Spacious and simple music does sound clear, realistic and with great dynamics (for example, Art Pepper and other jazz recordings from the 50s and 60s) but things fall apart when the music becomes complex or over-produced.  David Bowie's Black Tie White Noise sounds like a mess when the layers pile on, yet I have heard this album sound fine.

What I am seeking is better separation in the mix, with the ability to follow individual instruments and also better soundstaging.

planet10

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Re: Calling any Cambridge Audio R50 owners
« Reply #6 on: 25 May 2021, 08:22 pm »
a PCB, ferrite-core inductors, cheap resistors and electrolytic caps.  I could reverse-engineer a schematic

Those caps are not very good. If you start with the Pro9TL or the Web XO i suspect the topology will be much the same.

dave

Giraffe

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Re: Calling any Cambridge Audio R50 owners
« Reply #7 on: 25 May 2021, 08:35 pm »
I haven't compared the schematics but I think that the Pro9TL and Webb crossovers will be the same.

Just found information for the mods that Falcon Acoustics made to the original crossover design:
Quote
"...improves the performance of this network for the original B139/B110/T27 units by (A) increasing the roll off of the B110A (SP1003) at high frequencies from 12 to 18db per octave and (B) incorporating a simplified version of the acoustic Butterworth section for the T27."

So no change to the  B110/B139 crossover point.

planet10

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Re: Calling any Cambridge Audio R50 owners
« Reply #8 on: 25 May 2021, 10:52 pm »
Quote
no change to the  B110/B139 crossover point.

That is where the biggest ugliest parts are.

dave

Hobbsmeerkat

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Re: Calling any Cambridge Audio R50 owners
« Reply #9 on: 25 May 2021, 11:17 pm »
It all looks rough... A lotta cheap electrolytic caps, floss-gague iron core inductors, including the two at the top mounted parallel... Likely leading to some crosstalk issues between them...  :duh:

There's definitely a lot of room for improvement in there, esp in terms of clarity and detail.

planet10

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Re: Calling any Cambridge Audio R50 owners
« Reply #10 on: 25 May 2021, 11:20 pm »
They are the same topology. Some different values.



Third order on the B110 LP would, at its simpliest, be sliding the greyed out cap into the circuit just below where it sits, and then jugle the values of the C & L before it.

And this is what the 104AB circuit does: http://p10hifi.net/planet10/TLS/downloads/Kef104abXO.pdf

dave

Tyson

Re: Calling any Cambridge Audio R50 owners
« Reply #11 on: 26 May 2021, 12:52 am »
Or you could sell them and use the $$ to build a new speaker.  Drivers have come a long way in 45 years.

planet10

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Re: Calling any Cambridge Audio R50 owners
« Reply #12 on: 26 May 2021, 02:05 am »
The TL part is good. The B110/T27/ST4000 have more value than the box as a whole likely.

Sell those, put a decent 3-4” FR and bi-amp. It will be significantlyy improved/

dave

Giraffe

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Re: Calling any Cambridge Audio R50 owners
« Reply #13 on: 26 May 2021, 02:23 pm »
Or I could sell all of my hifi and buy the ATC SCM150ASL loudspeakers that are on Ebay at the moment, plus an ATC CDA2 mk2 CD/pre-amp/DAC unit.  Expensive perhaps but it'd be the only system I'd ever need and I could get on with listening to music.  Are the SCM150ASLs too large for a 13ft x 40ft room? (13ft x 26ft room plus 13ft x 13ft open conservatory with the loudspeakers in the room facing away from the conservatory).  I won't be living in this house forever and wherever I move to next will have a listening room of better proportions.

I am kinda serious, even though I love the R50s and would like to get the best from them and I do enjoy a project (although right now I have too many on the go).

jazyes

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Re: Calling any Cambridge Audio R50 owners
« Reply #14 on: 26 May 2021, 02:35 pm »
I agree with Dave and Tyson. The B110's and T27's will be gobbled up by LS 3/5A enthusiasts. IIRC, they are also used in the original Rogers JR149's and MK1's (a two way with
a aluminum cylinder enclosure). Both speakers still have a devoted following, especially "across the pond" in the UK. Falcon Acoustics has recommissioned production of both drivers to original spec and sell as replacements and in kit form, but very expensive.

John

nickd

Re: Calling any Cambridge Audio R50 owners
« Reply #15 on: 30 May 2021, 03:36 am »
Your R50 project reminded me of a pair of IMF TLS80’s I played with for a few months about 15 years ago. The bass from the B139 in a proper transmission line is really something to behold. Think you may have discovered  some of the weaknesses. Tweeters, caps, baffle designs and measurement technology have progressed substantially in the last few decades.

Hard to get those older multi driver, wide baffle boxes to image perfectly. Think if you restore them, you just have to love them for what they are. They can be a lot of fun, but won’t disappear and float instruments independently in a well defined soundstage. The laws of physics just won’t let that happen.

Really cool project though.  :thumb: