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IMF Professional Monitor IV

DSJR said:
Without being too biased or disrespectful either way (!!!) I'd say the Ruark speakers of my acquaintance can sound just a little "tight a*sed" in the bass (a bit like someone I knew who always walked as if he had a carrot stuck up where the sun doesn't shine).

Traditional early seventies IMF's let it all hang out big time. The B139 bass unit of the bigger ones could flap about uncontrollably and get everything not tied down in the listening room flapping about too. In my first life (at KJ Watford), we sold bucket loads of Crown/Amcron power amps, which back then were the only models with enough control (damping factor) over these wayward bass units (and this was with bell wire through a relay switched comparator as well!). The little D60 was a stonking power amp, brick walled at 35Watts, but it had the control and, more recently, sounds musical too with a modern source and pre-amp. We sold a lot of D150's too with the IMF's - more power - and we had the fear inducing (back then) DC300A as well!

The mark 2 models had a MUCH tighter bass and the RSPM IV was the first to come out. That's why I still have very fond feelings for it. The TLS50 models were ideal for typical UK rooms but looked tiny by comarison so we unfairly overlooked them, as with a push uf a button, we could show how much bigger and more imposing the sound was on the bigger ones

Favourite tracks/albums? Dark Side Of The Moon, Tago Mago (by Can), Anything by Mandingo (highly percussive jazzy stuff recorded in Abbey Road - we had a copy master tape) and Frankenstein, by the Edgar Winter group - I once had a round of applause after demonstrating this track through IMF ALS40's!

IMF's are of course over thirty years old now. The drivers may have aged and will almost certainly be irreplaceable with new ones. I wonder whether the internal sponge line damping will have disintegrated too? I'd love to hear a pair with modern gear, but to ever own some - I'd need a divorce and a big detached house.......

PMC are where it's at now, but the only ones that even begin to get where the big IMF/TDL models are the MB2 and BB5's to be honest. All the lower caste PMC's are but childrens toys by comparison.
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With the pair of the IMF 80's Mk2 I have, I check the internal sponge over the years and have not found any sign of deterioration, but then I also live in the non tropics and an air- conditioned house, and that may have some bearing.
Secondly I found that Japanese Lux amplifiers were a ' godsend' for transmission line speakers. The IMF's are special for that added unexpected 'exclaimation of really low air purr' in some quiet sections of classical pieces. With most other speakers, that reproduction is unattainable and non existent.
Thirdly I smiled at your mention of the 'power' fear with DC 300A's. Around that period I visited a shop that had also received in some very powerful beast amps called I think (Ampzilla's?) .Staff apologised that (in its use - with of their comparator) they had blown either one or both speakers in some of the speaker combinations on show.:D:D:D I am talking of the likes of AR 12'' ascoutic suspensions, large Altec Lansing and JBL's.The staff were mainly young 'hot shots', reputedly known for always 'impressing' by insisting on turning up volume controls to insane levels. In their eyes, the degree of loudness "determined" quality! Not long after, the place went out of business. It was no great loss.
 
DSJR said:
..............I'd love to hear a pair with modern gear, but to ever own some - I'd need a divorce and a big detached house.......

.
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I have always maintained that a good speaker is sexier than any woman! Come on men, do the trade before it is too late. :);)
 
I still own my pair of IMF-TLS 50, bought used some 20 years ago.. I remember well the day I heard IMF the first time. Mark IV and TLS-80, and then the 50. They had them plugged on a weird "Mission" amp. The preamp used batteries, and both pre-and amp had the Mission name litteraly "forged" in the front of their cases. Wonderful sounds.. wonderful music.

Finding a matching amp to control them is not easy. I used to have a Radford Zd-100. I equally used with success a Marantz 8B, but it was the only tube amp that brought these to life with control.

Over the years, I moved to Tannoys. First, bought an old battered pair.. and then the IMF went out in my workshop. Couldn't live without the immediacy of Tannoys. And can't get myself to sell the IMF I no longer use.

Other speakers I keep around equally are Sonab, Braun LV-1020 (triamped) Oh, yes, I equally had Quads, and loved them too.

One last word about IMF. I still wonder how they managed to have such an open and coherent sound out of "4" way xovers and drivers.

This was my first post here.

Sylvain (Quebec, Canada)
 
Welcome Sylvain!

Lux with IMF's? Not the early ones I can tell you - squelch, boom, Boom BOOOM! :)
 
Welcome to the forum, Sylvain.

My brother used to have a diy RSPM IV copy, driven from a Kenwood KA1000. Fond memories.
 
DSJR said:
Welcome Sylvain!

Lux with IMF's? Not the early ones I can tell you - squelch, boom, Boom BOOOM! :)
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Hi DSJR,

Thanks for welcoming me folks. I don't remember mentioning "Lux" with IMF, did I get something wrong?

On the other hand, the Marantz 8B has been the tightiest tube amp I've owned and the match with the smaller TLS-50 was made in heaven. The weird Mission amp was one of their first amps I believe, and it was a pricey thing.. just like their matching battery powered preamp. A lot of wow factor. Then they went on building cheaper products, but I'd say these earlier amps were very much Naim-like in character. The IMF are no small load for an amp, neither easy to place in a room. Mines were happy when 4 feet away from any wall. Otherwise, boom boom boom..

Sylvain
 
I'm sorry Sylvain, this old brain of mine gets a little confused at times...:D

The ZD100 was a really good amp (solid state) as I remember, but through the comparator its lack of bass control showed itself on the big IMF's, although mid and top were lovely. We had a "bargain" combo with a ZD22 pre and Crown D60 power amp which would work with anything (sounded amazing with Spendor BC1's and its relatives..

I wish we direct wired some of these vintage systems back then, even if it was with 79 strand cables and cheap patch cords..

I've heard Sonabs sound really engaging - not my taste of presentation but the OA7's (I think thats the title) sounded great in a clients home, even with a B&O centre driving them...
 
They were BIG!!!

I don't think they sounded that much different to the RSPM apart from the extra scale - did they?
 
I remember reading the reviews, about amplifier driving problems (I think the review ended up with different amps for the bass and mid), two B139 in their own lines, and lines for the mids too. I was sure they had the most bass extension out of all the IMF/TDL's?

I at one point, thought I would have liked to own them, and have had the oportunity Second hand mail order (£1500), but just couldn't house them. My preference is for something like the PMC BB5 though. (another I cannot house)

generale-2.jpg
 
Thanks for the link. It's been expanded in the last year or so - it's a while since I last looked and I'd forgotten about it.

God I'm getting nostalgic.... Speakers that'll probably never be made for a domestic market again :(
 
Hi everyone, just picked up on the IMF thread and joined up. I've had IMF speakers for a long time, TLS50's ( much under-rated), RSPM 1V's ( much the best of the RSPM range IMHO), and I run with a pair of SACM's ( IMF's flagship speakers) as well as a pair of much cheaper TLS80.2's. The SACM has the same x-over as the RSPM bar a couple of component values, they need some serious power to get going. The best of the lot? I agree with you, Paul, IMHO it's the TLS80.2 , it has great definition, soundstage, that serious TL bass that you don't get anywhere else, and it's easy to drive. Jerry
 
Just a quickie, I have contacted Stephane of the IMF site that 'cliffpatte' kindly posted, I am currently scanning all the circuits and literature I own relating to IMF Electronics, Stephane has a wish to publish this information on his site, so if any members need any IMF x-over circuits of the following:

RSPM MkIV, TLS80 MkII, TLS50 MkII, ALS40 MkII, Super Compact and Compact II, each model has features of the Polar response, frequency graph, Schematic with values and the full tech spec, yes I have a lot of scanning to do, so if you need info on these models go to Stephanes site.
Paul
 
On a parallel note, we used to sell Amcron (Crown) amps with the early - mid seventies IMF's, the dry, lean balance of these amps (especially the D150 power amp) suited the big IMF's really well.

I Googled the Crown IC150 pre amp as I'm trying to find a good cheap pre right now and it was panned as being hopelessly bright, with a "fingernails down a blackboard" quality to it.

I also remember a "bolt up" Naim 250 making TLS80's and especially the Pro Monitor 3 "improved" sound boomy and stodgy..

So this begs the question - what modern day amps would have the control in the bass for vintage IMF's, together with a sweetness and lightness of touch for the mid and top end? I think AVI amps would be cool, but what else?
 
I used to use HK ( Harman Kardon ) amps to run my pair of TLS80 MKII's, they were about the only power amp that had sufficient current for these speakers, the HK range of amps have always had a good beefed up power supply, something I have praised HK amps for in the past, they had the right thinking behind their design IMHO, sadly the top end was sometimes a little too fizzy on some of the lesser amps.
 
DSJR said:
We had all the IMF models to demonstrate and I also loved the TLS80 mk2. I dunno, I think I might have liked the adjustment possibility of the RSPM IV. I'm not sure if all these caps were always in circuit or could be switched out though, it's so long ago and in a life I thought I'd left behind....

I remember one very happy afternoon when JM Jarre's Equinox had just come out, playing side 2 and really getting in to it (I'm a sucker for electronic bass sequencers/arpeggiators). That controlled "push" in the chest on the bass notes and no boom on these, not even with a "bolt up" 250, which didn't quite have the damping factor on paper these TL's were supposed to need (it sounded awful in combo with the previous generation though, all wallowy Booooooom!!!!!!!).

If I try to play Dark Side of The Moon on CD on the ATC 20aSLpro's I have to almost catch the cone as it shoots out on the *heartbeats* :(
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I had a friend that talked about the low bass on his big Altec Lansing 'Voice of the Theatres ' with the usual top flared horns'. Ok, out came 'Jean -Michael Jarre's Concerts in China' -Side 1 for comparative testing with my IMF80 mk 2's. We heard the Altec Lansings swoop down and finish their bass 'show'. Then the IMF's were used on the same sequence.............the IMF's got to the same 'finish point' then slid further down into the bass region, showing just how much bass, the Altec Lansing's had 'chopped off'.
Rather startling.... as well as having one mortified crest fallen Altec Lansing owner.
 
I may have mentioned the day I bought "Equinox" just after it came out - it was good having HMV Bond St a five minute walk away...

I played side 2 on the TLS80 II and remember the sound like it was yesterday. I THINK it might have been on Naim as well, so much better was the damping on the series 2 models. So good, so deep and this sequenced "push" on your chest - lovely!

The change to Elac/TDL drivers made the sound rather dry and "nasal" as I recall and we didn't like them as much (I may feel differently now with modern equipment).
 
DSJR said:
On a parallel note, we used to sell Amcron (Crown) amps with the early - mid seventies IMF's, the dry, lean balance of these amps (especially the D150 power amp) suited the big IMF's really well.

I Googled the Crown IC150 pre amp as I'm trying to find a good cheap pre right now and it was panned as being hopelessly bright, with a "fingernails down a blackboard" quality to it.

I also remember a "bolt up" Naim 250 making TLS80's and especially the Pro Monitor 3 "improved" sound boomy and stodgy..

So this begs the question - what modern day amps would have the control in the bass for vintage IMF's, together with a sweetness and lightness of touch for the mid and top end? I think AVI amps would be cool, but what else?
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New Luxman amps.
 
Hi trusty IMF knowledgeables, have a lumpy problem that I could do with some help with. I have a pair of IMF Monitors supposedly "Professional" but I can't find any current reference to them in Google. They are 42" H x 24"W x 17" D, on casters not stands. Speaker layout is as Prof.Mon. oppostite handed pair, terminals and two switches upper corner in recess. These are surplus to requirement but can't sell without know-what.
 
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