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Multi-Way Conventional loudspeakers with crossovers

Cambridge Audio R50 and Rogers Monitor repair
Cambridge Audio R50 and Rogers Monitor repair
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Old 29th October 2014, 11:57 AM   #31
48kg is offline 48kg  United Kingdom
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Hello Lawrence,
Just read your post and as you can see i don`t get here that often.

It was a shame that your speakers were painted on the sides but i do understand that as even when we were making these the bought in panels the teak veneer was so thin that we often used to just sand through in places and the polisher had to colour them in!...it was very difficult. All was sanded by hand and not by large drum sanders.

The mention of a prototype i have never heard of but i do know that the pair i have are about the 2nd pair ever made.......they were given to John to assemble as he was a known good cabinet maker but the parts and shapes of the board inside the speakers are ALL different and when assembling he made a mistake and put a piece in the wrong way around.....one is correct and the other incorrect...but they were always kept in pairs where ever they went so i have them now after all these years.....and whats more i can prove that they are the earliest ones by the pictures of the insides and also the label with it`s date. John`s bench was next to mine so i heard and also witnessed the conversation between the foreman and himself.....i talked to him after and saw first hand what he had done so as not to make the mistake myself. Of course as you can imagine loads of pieces of board all dripping with glue during assembly one just carries on and assembles hence the difference.

You can see the piece of wood right inside the tapered rear tunnel where it is the wrong way around compared to the other.

You can also see the lambs wool right at the top of the tunnel where it goes through the various tunneling to the front of the speaker...of course this was all laid in upon assembly....there was no wool in the large rear tapered tunnel but just from the mid range and around the base speaker compartment.

When i opened mine up the wool had clumped and dropped due to the vibrations and so was all teased out again on assembly....i did keep the same wool and the amount is important as we had to weigh it before inserting so the correct amount was in each one.

I did replace my foam though with the blue....there has to be a cut out around each screw hole otherwise when screwing the front panel on the screws will grab the foam and spin it around and tear it but you won`t know until you remove it again!

I am thinking of replacing my black laminate to the top but of course these things are always on the back boiler so to speak.

I love my R50`s dearly and have never heard anything like them but i am at the moment selling some R40`s on the bay as i don`t have the time to restore them and i need the space now

Keith
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Old 18th December 2014, 08:17 PM   #32
RC in TO is offline RC in TO  Canada
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This all fascinating! I'm so glad to have been directed here by a fellow member of the KEF forum where I usually lurk about.

I have just purchased a bit of a "clunker" set of Cambridge TL-200s, that I understand are actually R-50's with a higher power crossover.
These are to be a restoration project for me, and I am really looking forward to it! I simply adore the TL design when executed correctly. In fact for the last several years we here have had IMF 80's as the main speaker in our living room. These do double duty for 2 channel stereo music listening, and Home Theater (No Sub Required!)
The TLS80's are BIG, and overpower the room with their girth. The TL-200's are much more room friendly shape. I hope to get at least similar sound quality from them when properly finished.

Before opening these TL-200's up I had a 20 minute listen at home (the previous owner had recapped the filters using Polypropylene cap's from Parts Express). 20 minutes was about all I could take. I found them so ridiculously forward in the mid's, shrill in the HF, and thoroughly unbalanced across the spectrum. Bass was seemingly pretty good, but my head was splitting after that 20 minutes from the rest of things.
So I ordered up some proper R-50 high powered crossover kits from Falcon as a start.

But the biggest surprise (and huge disappointment) was when I opened them up. I found zero long haired wool in the lower section behind the woofer. There is a plug of some white polyester fiber in the lower part of the first section of the line (going up the back).
Behind the B-110 there's another wad of polyester, and behind that a small blob of the original wool. There's nothing at all in the upper section of the B-110 line.
Behind the tweeters there's nothing at all in way of wool or polyester fill, but in the lowest part of the line jammed up from below IS a wad of polyester.
I'm going to assume that someone along the way decided they could "improve" their sound by replacing much of the wool. with other material. But my goal is get these back to at least close to original as possible.

Now I have a real problem! I need to find out exactly what's missing. (Wool) I need to source it and I need to find out exactly how much to get and where to put it.
If anyone can assist with information to these questions I would be eternally grateful.

Thanks all!
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Old 14th January 2017, 10:39 PM   #33
gavod is offline gavod
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Fascinating stuff. I made a pair of R50 look-alikes in the 1970s. The design was published in Practical Hi-Fi. I remember loads of high-density chipboard and hundreds of screws. The chipboard was a laminate sandwich with car underseal on the inside and veneer on the outside, but I never got round to putting on the veneer as I wanted so much to use them! I doubt that made much difference. They were simply fantastic, driven by a Beolab 5000 (which I have only today taken out of service). As far as the lambs' wool is concerned, I was sceptical that this could be the best acoustic absorbent but, as I was doing A-level physics at the time, I did a project comparing materials that might do the job and, amazingly, it was long-haired lambs' wool that worked best. Being in Edinburgh, I sourced mine by acquiring a fleece from a sheep-shearing business in the Scottish borders and cutting/carding myself to get the required mass. It made the speakers stink for a year or two (it was completely untreated, straight off the fleece) but worked wonderfully. The speakers lasted for years. We finally had to dispose of them when we moved into our current house in the mid 1990s, as there was insufficient room. I still hanker after them: the bass response was fantastic, particularly if you're an organ enthusiast! The instructions did say how much (weight) of lambs' wool to use, and from what I can remember the density was such that when evenly distributed it supported itself without much danger of it moving about. The idea is to distribute it through the transmission line so that as much sound as possible is absorbed. The length of the line is then such that any sound that does make it to the port is back in phase with the sound from the woofer (i.e. half a wavelength). I think there was also some stuffed behind the mid-range unit, just to damp any chamber echo (that box is sealed), but I'm not so sure of that. If I ever come across the instructions again I'll post a scan; but I suspect they went when I disposed of the speakers.
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Old 15th January 2017, 10:26 PM   #34
MIKEY G is offline MIKEY G
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Hi all,im new to this site and to this game,I am restoring a pair of R50s.In my own opinion i have done a cracking job on re-venering ,sanding and re-staining the cabinets.The problem i have is the two tweeters on one dont work,as it is both, the bottom keff t 27 is out would this break the circuit to the top tweeter,which i cant identify.As it is both could it be something else before i pay out for replacments.Is there anyway to check before making an exspensive mistake.Any info would be greatly apreciated as i need these beautiful things to do what they should.Thanks.

Last edited by MIKEY G; 15th January 2017 at 10:48 PM.
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Old 7th February 2017, 03:32 PM   #35
MIKEY G is offline MIKEY G
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Hi,I am in the middle of restoring my R50s.I have re-venered the cabinets and are looking very nice,for my first attempt. Now for the technical bit.I have the Kef and the Cole not working on one side. Could it be they have blown,or more likely something else.I am on a limited budget and don't want to spend out on the wrong things.How could I test? I am a complete novice to this but eager to learn.If I do have to replace,should I source original or replacements, i .e falcon acoustics? Can I change just the side which has blown,or will I have to do all 4 to keep them even?I also need to re_foam the midrange,or again better to replace? Where would I get original spares from.Sorry,lits of questions but I don't want to make the wrong move.Thanks in advance.
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Old 7th February 2017, 08:27 PM   #36
drewan is offline drewan  United Kingdom
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Hi Mikey, I am a Noob here but would think if neither tweeter is working it would more likely be a crossover/connection problem. I've no idea whether a continuity test alone on the tweeters would tell you. It would certainly be worth forking out a few for a cheap multimeter anyway. They are so useful once you have one.

Last edited by drewan; 7th February 2017 at 08:28 PM. Reason: spilling :(
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Old 9th February 2017, 10:56 AM   #37
MIKEY G is offline MIKEY G
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Thank you,i do really need to get to grips with a meter.I think it will be the right way to go,just need to learn ow to use one.thanks again
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Old 9th February 2017, 03:19 PM   #38
Andrewbee is offline Andrewbee  Jamaica
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Mikey G,

Contact Falcon and order the capacitors to replace everyone on your crossovers. They are old and most likely out of spec.
Do not use Solens or other PP caps, use the original style that Falcon sells.

I bought a beat up pair of Tl 200's / (R 50's) a little over a year ago locally.
Replaced all the drivers except the B 200's which are okay (thankfully) Also replaced the crossovers with the ones with the updated slope on the B 110 ( I can't remember the model), all from Falcon. Teased out the wool and rewired the pair. Made a new baffle for one of the speakers to replace a damaged one.

These things are 30+ years old. They are in a room ~ 16' X 40'. Wonderful sound. Well worth the effort and $ imo.

You could try moving the working drivers to the non working drivers box and see what happens. If they still do not work then its a crossover issue, if they work then defective drivers.
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