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Old 3rd January 2008, 05:49 AM   #1
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Default TDL reference standard speakers

I have been looking for a project to utilize my B-139's, and yes I am still shopping for a second pair.bawling:
Would it be practical and / or possible to replicate the TDL "top of the line" model using a more modern mid-range and tweeter?
I was thinking of the Vifa P-13 before they become totally extinct.
Did the 45 degree angle on the front firing woofers equal the benefits of front and back bass drivers?:
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Old 3rd January 2008, 05:53 AM   #2
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This is the only link I have been able to find on these speakers , and I can't speak or read Italian

http://digilander.libero.it/piani/tdl_electronics.htm

But these are the speakers I remember from my time in the UK, well before wife and kids I have to say
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Old 3rd January 2008, 07:50 AM   #3
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Ah, I loved those speakers! Through the rosy glow of recollection they were excellent, and extremely dynamic, but being a student at the time I could never afford them.

IIRC, the tapered front was to reduce the apparent baffle size for the mids and tweets, rather than trying to spread the bass around.
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Old 3rd January 2008, 04:17 PM   #4
Bobken is offline Bobken  United Kingdom
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Hi,

What a coincidence!

I just referred to a still-working pair of these "Reference Series" in another thread started by a countryman of yours. Seeing this pic actually reminded me that they were not IMFs as I had wrongly suggested, but TDLs, although both were designed by John Wright and shared a lot of construction/driver similarities.
Luckily, my carelessness in this other thread was not materially significant. (A "senior moment", we call it here!)

Also, the bass drivers in those are not strictly KEF B139s as far as I know, but (IIRC) they looked like some 'specials' which I believe JW had made by Elac (!), but strangely they had exactly the same shaped cast alloy baskets, and one could physically interchange them, as I tried this out temporarily. This alternative manufacturer rather puzzled me, but if my belief is correct here, maybe they were made under license from KEF, but they did not have the usual 'KEF' lettering cast into the frames, I do clearly recall. Otherwise, I might have thought that JW had standard KEFs modified by Elac for some reason best known to him.

The most (and only!) obvious difference being that unlike the 'conventional' KEFs (at least the 2 slightly different cast-alloy framed B139 versions I am aware of) which had a rigid but very light expanded polystyrene flat-faced diaphragm, these JW versions had a more conventional paper cone with a circular dust cap. Another 'oddity' I also recall was that the 2 drivers in one cabinet had different impedances (probably 8 and 4 Ohm, but could have been 8 & 16 Ohm), and the associated X'over parts values were slightly different. I guess that this was an attempt to 'separate' any fundamental similarities/characteristics to give a better and more-even 'spread' to the bass response, and it could be that the 2 transmission lines were slightly different, to help with this too.

I re-built these massive speakers for the owner a few years ago, and they sounded very impressive when on song. Incidentally, I guess that they must have been one of the earlier implementations of the MTM arrays, which later became very fashionable, or at least I hadn't seen this driver arrangement before seing these on dem in London many years ago.

Although it was a job I was paid for, I considered it to be a privilege to be able to do some work on these old mammoths, and I never thought that this would happen when I ogled at them with some amazement so many years earlier.

If you can replicate them successfully, I am sure that you would not be unhappy with the results, anyway, and they will fill a very large room with with a lot of enjoyable sounds.

My guess is the same as Pinkmouse's suggestion, and that the angles were intended to keep the width of baffle down as much as possible, and help reduce the diffraction effects with a less sharp transition to the side panels. The bass these monsters produce will not be very directional at those low levels, but this shape of enclosure gave rise to a mainly non-parallel sided transmission line, which is bound to have been good for the sound.

Regards,
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Old 3rd January 2008, 11:11 PM   #5
eanee is offline eanee  Australia
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A.O.S. Audio Systems are worth checking out.They carry some replacement units for the TDL range although now preferring Scanspeak in their own transmission line designs.
http://www.aos-lautsprecher.de/
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Old 4th January 2008, 07:40 AM   #6
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Bobken
I suffer from early onset "old-timers" disease myself.
I was aware of the difference in the bass drivers visually, but in the catalougue description the are described as a 'rigid polystyrene fibreglass composite' I would have to hazard a guess that they were modified at request possibly to control the cone break-up at 1K5 that people talk about?
Perhaps I should just concentrate on a sigle driver box using the B-139's, but that is an impressive unit and one day would be worth doing I am sure.
eanee
Thanx, just popped them an E-mail
Just found out that there are only 8 Vifa p-13's left at Speakerbits and probably no more that 3 dozen left in the country, i am trying to convince my partner that I "HAVE " to have them. Just in case I need them next year you understand
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Old 4th January 2008, 12:30 PM   #7
Bobken is offline Bobken  United Kingdom
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Hi Moondog,

I am a little confused as to which diaphragms you are reffering to when you mention Polystyrene, but this is certainly what the 'normal' KEF B139s are made of. As you are probably aware, they are just like the expanded polystyrene used in packaging, with a thin foil membrane glued to the front surface. Accordingly, the cones are still very light or low mass, but also extremely rigid, with the intention of them acting like the 'ideal' piston in use.

The drivers in the TDL, though, are quite different in this respect, looking exactly like thin paper cones, with the usual circular central dust cap, but I understand that the voice-coils were the same as KEFs. However, if it is these cones which you say are rigid polystyrene/glassfibre according to what you have read, I cannot think that this claim would be false, so I must have been mistaken in my earlier comments. The surface finish and texture of the cones was just like the usual duller/slightly rough compressed paper, unlike most synthetic plastic cones I am familiar with, which are generally more shiny and smoother-finished.

Although their cast baskets are physically identical to the later KEF units (except for no 'KEF' on them), as I said, I always knew that these were Elac-sourced, although I don't now recall why. Most likely it had a badge to indicate this on the back of the drivers, and, of course, none of the drivers in those monsters were actually KEF-sourced.

Since my last post, out of curiosity/nostalgia I clicked on the pic shown on your earlier reference, and realised that although this was an Italian site, the narrative is actually in English. This explained quite a lot to me as it makes clear that TDK is/was a subsidiary company to Elac, and that all of the drivers used were made by them. Maybe I knew this at one time, but some of these obscure details grow a bit dim with passing years.

Anyway, good luck with your endeavours, and if ever you do get around to replicating these TDL monsters, I am sure there will be a lot of interest on this Forum as to how you get on with this. As recently observed in another thread, I do believe that you would be able to surpass the mid and HF performance of any 'clones' with the better drivers now on the market, but improving on the TDL LF performance with using anything other than either B139s or the similar Elacs (if they are obtainable) would certainly take some doing.

Regards,
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Old 4th January 2008, 07:11 PM   #8
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Hi Bob
As you say the picture of the drivers in the web-link does appear to be paper as you describe, but reading the catalogue description it is stated "polystyrene/fibreglass" I has actually not realised that these were in English when I made the post.
WAF will be a big factor here, not the usual space matter but money.
I am suppossed to be saving for a wedding 'mine'
regards Ted
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Old 4th January 2008, 09:42 PM   #9
Bobken is offline Bobken  United Kingdom
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Hi Ted,

Congratulations on the forthcoming event, and as an old married man I can only say that I hope that you will have as happy a life together as my wife and I have had.

There are some things more important in the scheme of things than our hobbies, and who knows, maybe some time in the future you may get around to constructing the ultimate TDL clone.

Good luck to you both.

Kind regards,

Bob.
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Old 21st December 2011, 09:53 PM   #10
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Originally Posted by Bobken View Post
Hi Moondog,

I am a little confused as to which diaphragms you are reffering to when you mention Polystyrene, but this is certainly what the 'normal' KEF B139s are made of. As you are probably aware, they are just like the expanded polystyrene used in packaging, with a thin foil membrane glued to the front surface. Accordingly, the cones are still very light or low mass, but also extremely rigid, with the intention of them acting like the 'ideal' piston in use.

The drivers in the TDL, though, are quite different in this respect, looking exactly like thin paper cones, with the usual circular central dust cap, but I understand that the voice-coils were the same as KEFs. However, if it is these cones which you say are rigid polystyrene/glassfibre according to what you have read, I cannot think that this claim would be false, so I must have been mistaken in my earlier comments. The surface finish and texture of the cones was just like the usual duller/slightly rough compressed paper, unlike most synthetic plastic cones I am familiar with, which are generally more shiny and smoother-finished.

Although their cast baskets are physically identical to the later KEF units (except for no 'KEF' on them), as I said, I always knew that these were Elac-sourced, although I don't now recall why. Most likely it had a badge to indicate this on the back of the drivers, and, of course, none of the drivers in those monsters were actually KEF-sourced.

Since my last post, out of curiosity/nostalgia I clicked on the pic shown on your earlier reference, and realised that although this was an Italian site, the narrative is actually in English. This explained quite a lot to me as it makes clear that TDK is/was a subsidiary company to Elac, and that all of the drivers used were made by them. Maybe I knew this at one time, but some of these obscure details grow a bit dim with passing years.

Anyway, good luck with your endeavours, and if ever you do get around to replicating these TDL monsters, I am sure there will be a lot of interest on this Forum as to how you get on with this. As recently observed in another thread, I do believe that you would be able to surpass the mid and HF performance of any 'clones' with the better drivers now on the market, but improving on the TDL LF performance with using anything other than either B139s or the similar Elacs (if they are obtainable) would certainly take some doing.

Regards,
IMF started using TDL drivers whe KEF stopped producing the b139 bass unit as well as the mid range driver.
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