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vintageaxeman

Celef RT-1 speakers

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Super Wammer
16 hours ago, Mike H said:

BTW does the Emblem on the grills look right? From the pic I can't quite see it and the only pic and can find doesn't show the grill.

Hi Mike.

Glad that was useful.

The emblem position is the same as on my speakers originally, and they look to be 100% original emblems. Thin aluminium with printed logo, stuck on with a couple of spots of rubbery glue....they're the one bit of the whole speaker which I thought let it down....so I removed my Celef labels very early on.

As regards recapping, I replaced all the big caps, and also bypassed them with small precision polystyrene caps.....I didn't mess with the coils or the resistors. I did re-cable everything, though.

The crossover circuit boards are generic 3 way KEFkit style ones, (also similar to Cambridge Audio R50 crossovers I think).....I've got a feeling that my crossover boards actually say 'Falcon Acoustics' on them.....(FA have been a big supplier of speaker parts for decades in the UK)...but it's been a long time since mine were opened up.

And Hydie is correct, I'm pretty sure, about piano (gloss) black not being a usual option. It COULD have been a special.... but back then I don't think I had ever seen a gloss black pair of any speakers!    In those days, wood finish was the norm, or otherwise matt or satin black paint sprayed over woodgrain was very popular.  As long as they're not badly scratched, gloss black should look really nice....But be careful transporting them...any knocks or scratches will show badly on gloss black!

And as I've been corrected before, I should pass on the love....it's Stewart Tyler, not Stuart... :-)

Stewart is one helluva designer, to have come up with all the Celefs and Proacs over the years....I did talk to him on the phone once (since 2000), asking for advice about working on my crossovers. To be honest, although he remembered producing the RT-1s, as they were 'back-catalogue' by then, I was left to my own devices in the end....But there's enough expertise on here to advise you if you do have any queries.....

The rear port I forgot to mention. It's a few inches in diameter, and contains a bundle of drinking straws. If these are missing ('little fingers' could have pushed them into the cabinet) they can be easily replaced. This helps with controlling turbulence in the port. The single pair of speaker terminals will look very cheap compared to some of the 'gaudier' and bigger ones nowadays. Just make sure they are secure before you start tightening them up on the speaker cables....Of course you can DIY an improved pair of terminals for it. You might also be interested to know that on my first pair of RT-1s, I removed the crossovers for a while and had the speakers working actively, by using a home made active crossover (an Elektor magazine design) with 3 pairs of Leak valve (tube) amps, and later on with 3 Naim NAP160 power amps....  That took the sound up another HUGE notch!!!

Looking forward to seeing a picture of them clean, in position, and hearing what you reckon to them!

Cheers, David

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Well they were of course RT-1's and had been painted black I suppose to blend in with decor at some time. They had been her father's who died only 2 months ago. She's already sold his Revox RtR which I somehow missed and she says there's a lot of stuff to go through but she'll more or less give me first dibs after she researches the various items. I'm going to let them reach room temperature before I test them ( it was minus 24 celsius here last night which was one reason I didn't even bother testing them as they were in the garage) but she said they were fully working 2 years age before her dad retired them to buy some different speakers for her hearing impaired mother. The cabinets are in pretty good shape - just the odd scratch in the black paint so they should be easy to clean up and repaint. There are no cracks in the baffle boards so all's good there and no rubbing when the bass and mid drivers are pushed in and out so they should be fine. Just remains to be seen if the tweets are working so will let everyone know when I test them later today which unfortunately will be well past midnight for those of you in the UK. Oh BTW the serial numbers are sequential 77 and 78 so I take it a later pair plus the drinking straws are in place. I wonder if replacing the port with a newer flared one would be the way to go? Anyways thanks for all the input and can't wait to give them a try with my Yamaha B2 power amp ( or my OCM 500 , Sony TA-N80ES or Yamaha M80) 

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Well it seems everything is good - all drivers working well. Just need to know where the access is to the crossover. 

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Moderator
1 hour ago, Mike H said:

Well it seems everything is good - all drivers working well. Just need to know where the access is to the crossover. 

Would make an interesting active conversion project...

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Super Wammer
7 hours ago, Mike H said:

Well it seems everything is good - all drivers working well. Just need to know where the access is to the crossover. 

:-) Remove bass driver. Crossover is behind it.

5 hours ago, Tony_J said:

Would make an interesting active conversion project...

Active conversion worked very well for me.

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On 1/5/2018 at 15:09, vintageaxeman said:

Hi Mike....

Serge has given you all the right advice, as I would expect!!!

Yes, I can tell already from the split grilles and the proportions of the cabs, and the faint shadow of the drivers, that those ARE genuine CELEF RT-1s.

Back in the early 1980s I paid £600 (around $1,000USD) for a pair of ex-demonstration RT-1s. They were reduced to half price, having been DOUBLE that originally. The retail price was officially £1200 (around $2,000USD).  That was at a time when, as a young professional, I was earning around £400 take-home pay each month. So this was a VERY expensive pair of speakers.

I kept them for years, and eventually replaced them with a second pair. Not many people know of these speakers, so they tend to go for a very low price. I am not exactly sure how many pairs were made but I think it was less than 20 pairs, probably as low as 12-15.

YOU WILL NOT BE DISAPPOINTED in these wonderful speakers.

Construction and component wise, the bass units are ATC studio bass units. They are wonderful. The midrange units are actually KEF B200 units, the ones with the heaviest magnet. This might seem odd for a midrange, but they are in open backed cabinets so they work in virtually 'free air'. And as a consequence, voices in particular sound very, very realistic. The Decca horn tweeter is a ribbon tweeter which goes VERY high. But the most important thing about the ribbon tweeter is the realism that it gives to the sound. Transients are VERY fast. And anything metallic, such as a metal guitar or bass string, or a brass brush touching a cymbal, sound absolutely accurate. In fact sounds like these just shimmer and snap the whole sound into focus.

Things to look out for:

  • 1. Check the cones of the bass and midrange speakers and the surrounds. They should be undamaged. Both the surrounds, to the bass AND the mid, are rubber,not foam. Rubber is far less likely to have rotted into holes, but if there is any damage, you may be able to negotiate a discount.
  • 2. The ribbon of the Decca horn ribbon tweeter  (visible from the front of the cabinet, but at the back of the horn's throat) will almost certainly look ragged if it has been used a lot. It should look like a bit of tinfoil that has been neatly corrugated (folded) about 20 times. If it looks like it has scorch marks or raggedness to it, then it may still work but will need replacing.
  • 3. If you try the speakers out, do not try them loud until you are confident that they are ok. The reason is that the capacitors in the internal crossover may well have deteriorated (age) and if you put too much power into them, they could blow, damaging your Decca horn in the process.
  • 4. Three out of four of the cabinets I have had, have had a crack where the front baffle is inserted into the main cabinet frame. These are not removable (everything is glued in position) and is not an insurmountable problem (I can advise you about repairing it). The problem will show as a short crack running vertically, adjacent to the bass driver on the front veneer.
  • Are the proper base stands available. These came with the RT-1s, and I have one pair. If they are not available, I can advise you about how to make your own of the correct height.

I still have my second pair in use, and they are not hugely embarrassed by my active ATC SCM150ASLT speakers.

I also have some spares if you need anything. I have three spare pairs of Decca DK30 ribbon horn tweeters in stock.  I have 2 pairs of the correct KEF midrange units. And I have one pair of the original crossovers, fitted with a couple of component upgrades. I also manufacture the ribbon assemblies to order, and have enough parts to manufacture 8 pairs in stock right now. They take a couple of hours each, and when made, they are very vulnerable to damage so I don't make then up until I get an order in.

Go ahead and buy them. They're a steal at that price, even if you have to do some work on them. They will perform comparably to some very respectable modern day speakers.

As regards the finish, I have never seen black RT-1s, and I have the original brochure which doesn't seem to mention black. Both of my pairs AND the three other pairs I have seen were all mid coloured woods, which I am pretty confident were teak or walnut veneer.  My last pair are teak.  The finish doesn't matter as much, if you're getting such a bargain. There are a multitude of ways to refinish them, including reveneering, or much cheaper, using modern high quality photo printed self-adhesive vinyl such as burr elm pattern. It sounds cheesy but works incredibly effectively and nowadays the stuff is very realistic. I can advise you where to buy the best stuff from.  Or you could repaint them if necessary. (removing / masking the drivers first.) Likewise it is very easy to replace the grille cloth if it is dusty/old/damaged.

I hope that all helps.

Any more questions, please let me know.

Cheers, David

Thanks for all the info Dave. I've been comparing them to a rare pair of 3A M5 Serie Master I have and they compare favourably though the A's have more detail in the mids. The Celefs are more pronounced in the bass than I'd like but that may be because I have them on the floor. She didn't have the base stands and doesn't know what they would look like . Would you have a pic of the stands? Also maybe you could advise me as to the construction ( dimensions etc) should she   be unable to find them. Cheers, Mike.

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Super Wammer
On 25/01/2018 at 03:46, Mike H said:

Thanks for all the info Dave. I've been comparing them to a rare pair of 3A M5 Serie Master I have and they compare favourably though the A's have more detail in the mids. The Celefs are more pronounced in the bass than I'd like but that may be because I have them on the floor. She didn't have the base stands and doesn't know what they would look like . Would you have a pic of the stands? Also maybe you could advise me as to the construction ( dimensions etc) should she   be unable to find them. Cheers, Mike.

Hi Mike. Mine are sitting on their Celef stands in the garage. I will try to take a pic of them tomorrow. My first pair sat on home-made wooden stands for many years, as I preferrec a black painted woodgrain finish to metal tubing. Both work fine. Anything which lifts the speakers off the floor will reduce bass. My wooden stands were about 140mm high (around 5½")  The genuine Celef metal ones are a bit higher. I'll measure them for you. Any metal fabrication workshop can make them up for you. Cheers, David

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55 minutes ago, vintageaxeman said:

Hi Mike. Mine are sitting on their Celef stands in the garage. I will try to take a pic of them tomorrow. My first pair sat on home-made wooden stands for many years, as I preferrec a black painted woodgrain finish to metal tubing. Both work fine. Anything which lifts the speakers off the floor will reduce bass. My wooden stands were about 140mm high (around 5½")  The genuine Celef metal ones are a bit higher. I'll measure them for you. Any metal fabrication workshop can make them up for you. Cheers, David

That's great - I didn't know they were metal . That would make it easier for her to find them - I assumed they were wood and told her that but I didn't know their size. Personally  I'd prefer a dense heavy MDF base that would take a black  stain to match them.

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Super Wammer

When I had the RT-1s, I decided to use home made wooden bases as well. I didn't like the look of the metal stands. I used some solid 19mm Ash, (2 side pieces about 150mm tall, and the full depth of the speakers (front to back) and an MDF horizontal panel to join them, with an ash front lip. Lightly varnished, just to seal the wood, then spray painted with satin black acrylic. Joints were re-inforced with dowel rods (hidden) and glued with Cascamite.  So this made a sort of H-shape, which I can advise you further about if you're interested. At the time I had some Meridian amps which were not very tall, and I had each mono amp mounted under each speaker on the horizontal panel.   Spikes on the bottom, double sided tape on top just to locate without damage, and a couple of small metal plates at the back, screwed into the back of the stands and the back of the speakers, just to make sure they couldn't get knocked off.

The original metal stands are a Z shape with a 3 crossbars. Made out of 1" (25mm) square steel tubing.I still have them (below).

They are 290mm tall, and the width and depth of the speaker of course.

Not sure why they were designed like this, as the speakers do rock on them, which I don't consider to be a good thing at all. Maybe there is some reason why they might benefit the sound but I have never worked that out. Any way, I never compared my wooden stands with the metal ones sonically.

Cheers, David

Screen Shot 2018-01-27 at 16.18.39.png

Edited by vintageaxeman

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Thanks Dave. I'll wait to see if she can locate them after she visits her mom's place in the future. 

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Hi there.

Just picked up pair 007 008 !

Very happy for the moment.

Is the atc glued on or what ?

And does anyone have a picture of the crossover please ? 

Thanks.

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Super Wammer

Welcome, Sunnroyal! Congratulations!!!

Let's have a picture then!

I should be able to get you a pic of one of my 4 RT-1 crossovers in the next few days...unfortunately it's right at the back of my storage unit!

The crossover is in the bass compartment, accessible by removing the ATC bass driver. It's not stuck on (unless a previous owner has done that....some people use tube sealant. I don't!)

How do the cones and surrounds on the ATC bass driver and the KEF B200 look? OK?

And IN the horns, the crinkly foil at the back, behind the stainless steel grille, what does that look like?

I can advise you on mods to the crossover if you like....

Cheers, David

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Hi.

Thanks.

Pictures soon.

Don't want to modify crossover, just refresh it.

Speakers all ok. But ATC stuck in place, on one speaker at least.

I'll tell you what.

Cheers.

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Super Wammer

Maybe this suggestion can help....

Around the circumference of the speaker are the 8 mounting bolts....Offhand, I  don't know what thread they are, but assuming they are metric, they are probably M5 or more likely M6. Of course these go into T-Nuts in the back of the baffle, through 'clearance' holes (unthreaded) around the outside of the speaker surround.

But for the purpose of removing the bass drivers, try this.... The plastic trim pieces around the perimeter of the speaker...which are held on by some smaller bolts, are actually screwed into the metal frame of the speaker... These plastic trims should be left in place, BUT, there is nothing stopping you temporarily screwing in a longer bolt (important...use high tensile socket head bolts) of the same thread, so that you can hopefully use a mole wrench or pliers etc to get some purchase on the bolt and either PULL or LEVER the driver out using a block of wood as a fulcrum...If you're not quite sure what I mean, ask and I will happily draw you a diagram....  Just be careful you don't use so much force that you damage the threads or break the bolt off in situ.

Nobody in their right mind would have GLUED the speakers in, but using sealant I can understand....so the chances are that it WILL come out eventually. But you never know!

As regards the crossover, I replaced some of the big polyproplene caps with the same values but with better quality caps, but I also used some small polystyrene capacitors to bypass the larger ones. This is a well known type of mod, which can allow tiny details to be revealed more easily.

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Hi.

Thanks I will try for the moment thy just took place, and are singing ... Well !

Just found some stands good size in height.

I have many apps to try on them.

Actually with albarry monoblocs 100w, later Sunfire 300. And many more ...

Pictures soon.

To be continued ...

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