IMF owners thread!

[SimplySound]

May 1963 - IMF Styrene Pressure Speaker...

Good stuff Jeff!!!!

It says in this brochure that "The IMF Styrene Pressure speakers use British Drivers..."

I'm going to go on a limb here and say these were probably KEF B1814's... not exactly sure when the B139 came out but it was probably around 1963 and I doubt KEF was shipping those to other builders at that point... This is from the History of KEF Drivers.

When KEF was founded in 1961, by Raymond Cooke and a small group of likeminded
colleagues, the prime objectives were to design loudspeakers using the latest
materials technology and with the best engineering methods. The 1960s was a hotbed
of innovation in drive unit technology with significant contributions from a number of
commercial companies as well as the BBC’s Research and Design departments.
The first drive units designed and developed by KEF formed the K1 series of
products. They comprised the B1814 bass unit, with a flat diaphragm of polystyrene
with aluminium foil laminated to the front and rear surfaces, the M64 elliptical
midrange with the same polystyrene/aluminium foil laminate structure, and the T15
tweeter with a dome made from aluminized melinex.

 

[mech986]

Hey Canuck,

Thanks for the pdf's from tyella, the read on the Professional Monitor confirms what I suspected about that model - it's going to be a very good speaker and if working well, mccarty is going to be very pleased.

As for my RSPM Mk. VII's, its a solid performer and sounds very good. Interestingly, if one is expecting to hear a lot of low bass enhancement, it doesn't do that. Rather, it plays what bass is in the recording and doesn't exaggerate it. My Big JBL's tend to push a bass hump due to their ported designs, and on most common music, it certainly sounds nice. But the Mk. VII's may be more accurate - quality vs. quantity so to speak.

I haven't pushed the Mk. VII's beyond 50 watts of SS Yamaha professional power though, so I don't think I've tested their ultimate capabilities yet.

At some point, I'll have to see if I can drag the TLS50's down to compare, and then pull the TLS80 Mk. II's I picked up in May or June to have some type of shootout. After that, I may need to get new windows and repair cracks in the walls!

 

[mech986]

BTW, this is all without having had a chance to do any crossover restoration work. Have been dealing with some serious medical problems with my daughter over the past month (still in Hospital as I type) so have not been home to play with audio.

Still, great to see and hear about the AK IMF experiences. Cheers!

 

[mccarty350]

Jeff...thank you...man...that really fans the flames

Hey fellas,

Another AKer (tyella) graciously offered to pull out these IMF reviews from a Stereo Review magazine. Big thanks to him! I thought I would share them with you here.

See below.

It's IMF Day!


March 1983 - IMF Professional Monitor


December 1971 - IMF Studio


July 1965 - IMF Mark III Cartridge


May 1963 - IMF Styrene Pressure Speaker

Of note, the 1960 reviews are from when IMF was run by Irving M. Fried, and aren't products from John Wright, but are interesting nonetheless. The other two reviews, the Studio is the smaller version of the original t-line that made John Wright and IMF (of the UK) famous. mccarty350, your Pro Monitor review is posted there.

Enjoy!


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[mccarty350]

Indeed, I'm ready! If you get the time to do the comparison I'll definitely be curious to hear the results. Seems like some folks liked the TLS 80 over the RSPM's due to the simplified crossover, more dynamic, etc. etc. I'm guessing it will be a matter of preference but definitely curious to hear your preference Bart.

Hey Canuck,

Thanks for the pdf's from tyella, the read on the Professional Monitor confirms what I suspected about that model - it's going to be a very good speaker and if working well, mccarty is going to be very pleased.

As for my RSPM Mk. VII's, its a solid performer and sounds very good. Interestingly, if one is expecting to hear a lot of low bass enhancement, it doesn't do that. Rather, it plays what bass is in the recording and doesn't exaggerate it. My Big JBL's tend to push a bass hump due to their ported designs, and on most common music, it certainly sounds nice. But the Mk. VII's may be more accurate - quality vs. quantity so to speak.

I haven't pushed the Mk. VII's beyond 50 watts of SS Yamaha professional power though, so I don't think I've tested their ultimate capabilities yet.

At some point, I'll have to see if I can drag the TLS50's down to compare, and then pull the TLS80 Mk. II's I picked up in May or June to have some type of shootout. After that, I may need to get new windows and repair cracks in the walls!

 

[canuckaudiog]

My Technical Data Sheet arrived for my IMF RSPM Mk IVs the other day!

This means I now have the full complement of literature that came with them upon purchase, making them complete with boxes, paperwork, etc. Although it's just one document, this makes me very happy. :yes:

I'll be getting those scans up for you guys shortly. I've been trying to find some time to rig the scanner up, but it's coming.

Also, I am currently working on a Sansui 500a receiver. I'm just in the midst of selling some extra stuff to pay for the parts to restore it - I plan to run it full bore with the IMFs as I am very curious to see how a piece of tube gear will run with the IMFs. I have done it before with 6.5 WPC and it sounded excellent - we'll see what a 20 WPC Push Pull, Sansui-made receiver will do!

 

[c-atle-79bay]

I enjoy running my studios with a sherwood S8000, was concerned at first with the sherwood's heavy bass but did not have any issues.

 

[mccarty350]

I'm curious as to what will happen, I always hear that the woofers on these things need high damping factor amps to keep them from becoming floppers, using a tube amp should put that to the test.

 

[canuckaudiog]

I'm curious as to what will happen, I always hear that the woofers on these things need high damping factor amps to keep them from becoming floppers, using a tube amp should put that to the test.

Of interest, I spoke with a british gentleman whom purchased my Kef 107s from me and he used to sell british hi-fi over in London back in the 70s (he's very fond of Kef as a result). They sold Kef, Celestion, IMF, Spendor, Rogers, etc. He said that the IMFs were voiced with Radford tube amplifiers. This is entirely possible - and it intrigues me. The whole damping factor argument I think isn't very well thought out nor educated.. it's simply a guess as to why some amplifiers don't work well with the IMFs and the B139 in particular (and, t-lines I suppose as well).

I think it strongly depends on the circuit topology of the amplifier and as always, experimentation is key. Like I mentioned I had a 6.5WPC SET amplifier running the IMFs and it sounded very satisfying. No detraction in the bass department - the midrange was very sweet. I have no doubt that this Sansui will be able to run the IMFs just fine. Certainly they like brunt-force solid state power, as you can only achieve their maximum SPL this way (what with their low sensitivity and the heavy nature of the drivers, crossover and large cabinets), but hitting around 80-85dB in most environments doesn't require you to be using the maximum amount of power the speakers can take. So, anyways, we'll see how this plays out. I'm around 1-2 months off from getting this project completed - it's just a matter of getting the funds together. But I am very motivated to do so since this receiver (the 500a) is one I have really wanted to hear!

 

[c-atle-79bay]

Interesting with the 6.5 watts, I'm on the TPA VS Tripath tread about the TPA3116 chips and really wanting to build one of those amps to run with a bottlehead foreplay and never thought about running the IMF's with that kind of power.

 

[jimmymcfarre]

Ran my RSPM4 with a lowish powered valve amp with very good results. I don't remember the specs - it was built by a friend & I just borrowed it for a couple months - but there certainly wasn't any lack of volume or bass control.

 

[mccarty350]

Okay, good to hear that that was fictional speculation. I'm guessing my only problem would be having enough tube watts to actually drive something this inefficient to a volume worthy of anything.

 

[canuckaudiog]

Okay, good to hear that that was fictional speculation. I'm guessing my only problem would be having enough tube watts to actually drive something this inefficient to a volume worthy of anything.

Yeah, it depends on how far away you sit from them. In my current set-up I am about 10 feet away and 20 watts will be enough for me.

Keep in mind that for example my RSPMs produce at 1 watt at 1 metre away 80dB (up to 82dB depending on the control settings) of sound - another watt and that's 83dB, another 2 watts and now we are up to 86dB at 1 metre. 8 watts is 89dB.. which is getting pretty loud. Of course I don't sit that close to the speakers, so to achieve my desired volume level I likely have to double the power again, to 16 watts, to achieve 92dB at 1 metre - and here I should hear my comfortable 80-83dB sitting 10 feet away.

Power ratings are a funny thing. The IMFs seems horribly insensitive but only in comparison to other speakers. In realistic terms it doesn't take that much power to get them going.

 

[Cadastra]

selling IMF RSPM Mk iv improved

Folks, I am retiring and downsizing so finally after 35 years am selling my beloved RSPM's any ideas on value and best place to put them (ebay?) I am in Sydney Australia so shipping may be an issue..

 

[canuckaudiog]

Folks, I am retiring and downsizing so finally after 35 years am selling my beloved RSPM's any ideas on value and best place to put them (ebay?) I am in Sydney Australia so shipping may be an issue..

Best to put up a thread in Dollars and a Sense but I'll send you a PM...


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[mccarty350]

I definitely am not a professional here that's for sure nor is my understanding of the real world impact of damping factor, etc. anything great so I'm just latching mentally on what my brain thinks 'should' be a factor. I'm eager to hear the result though...I may beat you to it, I should have mine in a few weeks and I have a baldwin 4 x 6L6GC based amp in my office that I can try on the Professional Monitors.

Of interest, I spoke with a british gentleman whom purchased my Kef 107s from me and he used to sell british hi-fi over in London back in the 70s (he's very fond of Kef as a result). They sold Kef, Celestion, IMF, Spendor, Rogers, etc. He said that the IMFs were voiced with Radford tube amplifiers. This is entirely possible - and it intrigues me. The whole damping factor argument I think isn't very well thought out nor educated.. it's simply a guess as to why some amplifiers don't work well with the IMFs and the B139 in particular (and, t-lines I suppose as well).

I think it strongly depends on the circuit topology of the amplifier and as always, experimentation is key. Like I mentioned I had a 6.5WPC SET amplifier running the IMFs and it sounded very satisfying. No detraction in the bass department - the midrange was very sweet. I have no doubt that this Sansui will be able to run the IMFs just fine. Certainly they like brunt-force solid state power, as you can only achieve their maximum SPL this way (what with their low sensitivity and the heavy nature of the drivers, crossover and large cabinets), but hitting around 80-85dB in most environments doesn't require you to be using the maximum amount of power the speakers can take. So, anyways, we'll see how this plays out. I'm around 1-2 months off from getting this project completed - it's just a matter of getting the funds together. But I am very motivated to do so since this receiver (the 500a) is one I have really wanted to hear!

 

[mccarty350]

I posted in dollars and sense to find out what were reasonable prices for what I was going to sell and ended up getting my thread deleted. I started reading policy (I guess I should have before) and found that you cant' use Dollars and Sense to determine best price for something you are going to sell or that has any bearing or benefit to you on selling or at least that's my new understanding.

Best to put up a thread in Dollars and a Sense but I'll send you a PM...


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[Radfordman]

Your midrange unit is an EMI unit with extra coating on the cone. Some early IMF's used these units. My friend who worked for EMI used to supply IMF.

Hey,

thank you everyone for giving me a warm welcome to Audiokarma, I really appreciate it!

@captouch: I have tested the supertweeters independently on a beat frequency oscillator (luckily my dad owns one) and one of them gives out a cracking noise in the really high areas which the other one doesn't produce, that's why I figured that one of the supertweeters isn't working properly.

@curlycat: Thanks for the warm welcome, I'll do my best to restore those old beauties!

@mech986: Thanks for the info on the Coles tweeters - it makes sense that my ones are an older type. The thing that bugs me is that my tweeters are metering roughly at 55 Ohms impendance so replacing them with new 16 Ohms ones would lead to a change of the capacitors on the crossover, right? Maybe I need to take some time and actually find a pair of "old" Coles supertweeters.

My plan is to renew the capacitors on the crossovers anyway.

As promised, here are some more photos, I hope that they shed some more light on what type/kind of IMF TLS I actually own.

Here are the cabinets:

The woofer, a KEF SP 1014:

The midrange, I guess it is an "IMF own brand"? But I am not sure, it has rubber surrounds which seem to slowly come off from the chassis - I guess they can be glued back in place though.

The tweeter, a Peerless, which looks very similar to the tweeters made by Heco in the 70s and which were used in many German made loudspeaker cabinets.

Finally, the crossover - I have been in contact with Falcon Acoustics and they told me that the capacitor layout is actually that of IMF studios.

Thanks a lot guys!


Marcus

 

[mccarty350]

Professional monitors in the back of our suv on the way back to indy...all drivers confirmed working...let the rehab begin

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[canuckaudiog]

Professional monitors in the back of our suv on the way back to indy...all drivers confirmed working...let the rehab begin

Sent from my SPH-L710 using Tapatalk

WOOHOO! I'm excited for you! It'll be interesting to hear your thoughts on these. Keep us posted and post some pictures