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IMF pro monitors 3 refurb

Radfordman said:
Are these anything like yours?

http://images.google.co.uk/imgres?i...q=imf+professional+monitors+3&hl=en&sa=N&um=1

KEF B139, KEF B110, Celestion HF1300, Celestion HF2000.

In case you were not aware there are several types of HF1300, basically big magnet, small magnet, high and low impedance.

The B&W's, Spendor and I believe the IMF's use the large magnet 15 Ohm ones.

Small magnet ones are used in things like Celestion Ditton 10, 15, County. In my experience, they seem to be less robust (still pretty good though)
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Isn't the uncovered supertweeter on the left a Coles?

I've got a set of NOS HF1300s and Coles from a B&W dealer's old spares, good for DM2A and DM4, and they're all 8-ohm units.

Also, retail HF1300s had a plastic cover over the rear of the magnet making it appear much larger, where the OEM ones had no covers. There were also front-mount and rear-mount versions of the 1300. I think the origins of the HF1300 were as tweeters for the old GEC Hugh Britten aluminum cone speakers of the 1950s.
 
Yank said:
Isn't the uncovered supertweeter on the left a Coles?

I've got a set of NOS HF1300s and Coles from a B&W dealer's old spares, good for DM2A and DM4, and they're all 8-ohm units.

Also, retail HF1300s had a plastic cover over the rear of the magnet making it appear much larger, where the OEM ones had no covers. There were also front-mount and rear-mount versions of the 1300. I think the origins of the HF1300 were as tweeters for the old GEC Hugh Britten aluminum cone speakers of the 1950s.
Click to expand...

I believe that the uncovered supertweeter on the left is an HF2000 (without grill, they sometimes come off). The The Coles 4001 does not have any visible leadouts on the faceplate. The colour of the faceplate and the lack of black grill makes it look a bit like a Coles 4001.

Yes, I have some of the retail 1300's as well, plastic cover over magnet and label on front. Yes, different mountings as well for 1300.

The HF1300 from DM2, DM2a, DM4 are 16 Ohm units (at least all the ones I have are). They are sometimes marked. The Coles 4001's (4001G) from the same speakers are so called 16 Ohm. In fact they measure 23 Ohm DC resistance. The Celestion HF2000 would be a much lower impedance unit. Theoretically, the Coles 4001G and the Celestion HF2000 cannot be interchanged without a crossover mod.
 
You should find confirmation of what I mentioned on the Yahoo Spendor Group. I also put some photos of various HF1300's there.
 
I just looked through my junk box and sure enough, the pair of HF1300s are indeed 16-ohm units. I have no idea why I've been suffering under the misapprehension that they were 8-ohms. That misapprehension has probably kept me from buying some BC1 fixer-uppers that occasionally popped up on eBait.

The 4001s are unmarked, so I would assume them to be the usual 23 ohms. The reason for that odd choice of DC resistance, I believe, is due to the origins of that dome as a microphone diaphragm.
 
Yank said:
I just looked through my junk box and sure enough, the pair of HF1300s are indeed 16-ohm units. I have no idea why I've been suffering under the misapprehension that they were 8-ohms. That misapprehension has probably kept me from buying some BC1 fixer-uppers that occasionally popped up on eBait.

The 4001s are unmarked, so I would assume them to be the usual 23 ohms. The reason for that odd choice of DC resistance, I believe, is due to the origins of that dome as a microphone diaphragm.
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Yes, a lot assume that because the BC1, BC2, BC3, DM1, DM2, DM4, Rogers Export Monitor etc. etc. are nominal 8 Ohm speakers, that the Celestion HF1300 inside is 8 Ohm. Not so they are all the 16 Ohm versions.

Yes the origin of the Coles 4001G is microphone capsule (originally STC) I still have some STC 4001Gs, identical to the Coles.

The 4001 is still available in a lower impedance version (7 Ohm) and I believe that there was a third even lower impedance one years ago.

Some years ago I bought a pair of B&W DM4s cheap because one HF1300 had been replaced by an 8 Ohm version (small magnet). The seller told me. I thought this a great sin, however it seems to work reasonably well, difficult to hear any difference between the two speakers. Not ideal, but not as bad as one might think.
 
Radfordman said:
I am no expert on IMF's, certainly the ones I remember seeing years ago had the KEF, B139, B110, 1300, 2000. But I may be mixing up, the big elliptical Elac may have been used when the company took the TDL name.
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I have a pair of what was 'late IMF': IMF's TLS80 MK 2.-4 way. They have the elliptical bass unit with rubber surround - not the original traditional KEF K139 as used, in the MK 1..
 
Adding further on: I believe that the ultra tweeter in the IMF TLS80 Mk 2 : from 13KZ to 24 KZ was possibly a French Audax unit.
 
ter said:
I have a pair of what was 'late IMF': IMF's TLS80 MK 2.-4 way. They have the elliptical bass unit with rubber surround - not the original traditional KEF K139 as used, in the MK 1..
Click to expand...

Probably these ellipticals ?


DSC04257.jpg


DSC04256.jpg
 
Is it the model with the cast frame and heavy magnet? Are those ones with the pressed frame in pics just cheapos?
 
lexi said:
Is it the model with the cast frame and heavy magnet? Are those ones with the pressed frame in pics just cheapos?
Click to expand...

The pressed frame EMI's can be very good 10x6" in B&W DM1, 13x8" in DM3.

Cast frame 14x9" EMI's were not used in IMF as far as I know. That part number is 14A770C.

They were used by Monitor Audio in MA2? with B&W 8" mid and Isophon (I think) hard dome tweeter.
 
Thank God for that! I thought that you were saying the pressed steel ones were crap..........I` ve two for a project:D
 
lexi said:
Thank God for that! I thought that you were saying the pressed steel ones were crap..........I` ve two for a project:D
Click to expand...

The surrounds look good on yours, can shrink with time etc. The EMI ellipticals are pretty good. Trouble there are so many versions on the same chassis. Magnet size is obvious, so is voice coil size, but there are different cones that look similar. Paper, double laminated paper, triple laminated paper and fibreglass laminated with paper.

The fibreglass ones were only only supposed to be for B&W, but some got out somehow. The guy who did the fibreglass EMI went to work for B&W, forget the name.
 
As the consensus seems to be to replace tweeters with original fitments, Question, With the studio monitors (all makes) if they were used as intended in a studio the tweeters were changed on a regular basis (at least in the ones I know of). If it was considered prudent to change the tweeters, albeit after huge usage in comparison with home usage. Why is it that the accepted way now is to continue to use very old tweeters in these speakers?

Are we actually hearing the speakers as they were intended. Or are we losing out through degradation from use and or time. I have always just replaced like for like in the past but is it really the correct way to go?
 
This is not really an answer to your question, but in about 1969 Jim Rogers sold me two EMI 13x8" bass units (large magnet fibreglass laminate cone), two Celestion HF1300 (16 Ohm) and two STC4001G (Coles.). I built these in some very heavy cabinets (1" thick wood close to 3 cu ft). There are no electrolytic capacitors in the crossover and they have had a lot of use since then.

They still sound perfect today, although they have never been driven from "monster amps" I do have a 100W per channel Quad 405-2, but this is used with care and and rarely as I prefer other amps such as the Radford STA25 III, though this is not weedy, close to 40W per channel.

I have many other speakers (for many years) that use the HF1300 (16 Ohm) and Coles 4001G combination, eg. B&W DM1, DM2, DM2a (DM3 although HF1400), DM4, Spendor BC1, BC2 and some home built KEF B200/ HF1300/ Coles. I have never managed to damage a HF1300.

I have (stupidly) managed to burn out two Coles 4001G accidentally, when
testing a pair of DM4's on a signal generator that was set at a high frequency, the amp volume was too high and the tweeters popped almost instantaneously.

The only other casualty was a single KEF B200 bass unit. This was in about 1976 when I bought a brand new Quad 405 and was testing it out. The B200 is not very efficient so this was quite easy to do without achieving that high a sound level! Stupid again.

Still just these casualties in over 40 years messing with loads of loudspeakers is not bad.

I would guess that in years past that most tweeters in studios were not blown or damaged by music, more likely the fast spooling of tape with audio on.

You raise a good point, how was maintenance of monitors carried out in say the BBC? Were they checked for calibration? If so how often? etc. etc.

I have friend who is a BBC Engineer and will ask him that question. He is much younger than me and I introduced him to the LS3/5a. He now uses those and JR149's at home. He prefers them to the Genelec Monitors that he uses at work.

The Celestion HF1300 and Coles 4001G are old designs, but in my experience, if treated with respect, last and last. The same cannot be said for some newer offerings with ferrofluid that can congeal and affect the performance drastically.
 
This is not really an answer to your question, but in about 1969 Jim Rogers sold me two EMI 13x8" bass units (large magnet fibreglass laminate cone), two Celestion HF1300 (16 Ohm) and two STC4001G (Coles.). I built these in some very heavy cabinets (1" thick wood close to 3 cu ft). There are no electrolytic capacitors in the crossover and they have had a lot of use since then.

They still sound perfect today, although they have never been driven from "monster amps" I do have a 100W per channel Quad 405-2, but this is used with care and and rarely as I prefer other amps such as the Radford STA25 III, though this is not weedy, close to 40W per channel.

I have many other speakers (for many years) that use the HF1300 (16 Ohm) and Coles 4001G combination, eg. B&W DM1, DM2, DM2a (DM3 although HF1400), DM4, Spendor BC1, BC2 and some home built KEF B200/ HF1300/ Coles. I have never managed to damage a HF1300.

I have (stupidly) managed to burn out two Coles 4001G accidentally, when
testing a pair of DM4's on a signal generator that was set at a high frequency, the amp volume was too high and the tweeters popped almost instantaneously.

The only other casualty was a single KEF B200 bass unit. This was in about 1976 when I bought a brand new Quad 405 and was testing it out. The B200 is not very efficient so this was quite easy to do without achieving that high a sound level! Stupid again.

Still just these casualties in over 40 years messing with loads of loudspeakers is not bad.

I would guess that in years past that most tweeters in studios were not blown or damaged by music, more likely the fast spooling of tape with audio on.

You raise a good point, how was maintenance of monitors carried out in say the BBC? Were they checked for calibration? If so how often? etc. etc.

I have friend who is a BBC Engineer and will ask him that question. He is much younger than me and I introduced him to the LS3/5a. He now uses those and JR149's at home. He prefers them to the Genelec Monitors that he uses at work.

The Celestion HF1300 and Coles 4001G are old designs, but in my experience, if treated with respect, last and last. The same cannot be said for some newer offerings with ferrofluid that can congeal and affect the performance drastically.
 
Sorry about the delay in replying, I would also be interested in knowing if these days they actually checked the calibration of the monitors on a regular basis, and if so whether there was measurable degradation of the tweeters. So would be interested in your friends reply.

I suppose the only real way to find out just how time etc has altered the actual sound (if any) would be to compare a modern test of a pair of speakers and an original test using the same methods, test equipment and environment. Of course virtually impossible to organise more is the pity.

Certainly in the past I have not had the diversity of quality speakers that you have had experience of. Various Rogers including a pair of very battered LS3/5a that were given to me as studio cast offs., and from the time I first heard them the big IMFs.

More through luck than judgment the only drivers I have destroyed have been in economy speakers that were 'hard rocked' at much too much volume.

Over the years 'classic' speakers are more pleasing (at least to me) with their overall 'presence' than most if not all the modern commercial speakers that I have heard. Mind you I have not heard any of the super expensive ones. What a pair costing over £30k sound like, is hard to imagine.

I have now managed to pick up two pairs of HF1300s, one set from a pair of old speakers I fortuitously bought from a garage sale, which has also yielded a good pair of B139s though the B110s were shot. And another pair from a dealer. So have fitted them to the IMFs with a replica mk4 xover I built, works very well and as much as one can say after 30 years sounds just like I remember my others sounded.

Having now got them back to approx how they were intended to sound, I am getting the urge to experiment and see if good modern tweeters prove a good enhancement and make Classic speakers even better without losing their character and balance. Therefore I have decided to buy the CAT308s and a pair of Fostex FR drivers and see if they can successfully be used in the IMFs as replacement tweeters and if they would actually be an upgrade. If not I can always go back to standard and the Morels and Fostex will be used in other projects.

Hypothetically, in a few years time when original drivers may be virtually impossible to get, how adverse would you be to using new replacement drivers in say your favourite speaker or would you prefer to sacrifice another pair to get the required drivers?
 
I will send an e mail to my friend that is a BBC Engineer, he is on holiday at the moment, probably about another week.

Trouble substituting modern units for old designs, crossover will probably not be ideal, efficiency/ sensitivity of units may well be different, etc. etc. If the new unit is more efficient/ sensitive, that will initially sound more impressive.

Some substitutions can work, however I think most don't.

Here, a substitution for Spendor BC1 bass unit is suggested (by Willmsow). I bought them, not satisfactory in my view. See the comments towards the end. I am "Guest".

I probably would rob another system to repair a particular speaker. eg. I have Chartwell LS3/5a, if a T27 tweeter should fail I would have no hesitation taking a T27 out of a pair of KEF Choralle or Cadenza that I also own.
 
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