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Hi all

I was working with a well known Dutch pianist and he has a pair of IMF speakers in his rehearsal studio. The type is ALS40, these speakers sound very good, well balanced and a very accurate mid plus really nice low end.

Anybody who's familiar with them speakers?

Peace, Han


anonymous Wed, 02/18/2004 - 12:22

IMF stands for "Irving M. Fried", after the guy who designed and the speakers. His nickname was “Bud”. IMF Electronics went out of business in the late 80's. TDL was the successor company of IMF and run by most of the same people. TDL also eventually went under. There is a new company called "IMF Audio" that bought the name, but the speakers are nothing of the sort. Bud Fried was one of the greatest speaker designers who ever lived; he died a few years ago.

The speakers you saw were manufactured between 1977 and 1983. All of IMF designs were based on the "transmission line" theory. Very different from bass reflex or any other designs you might see today. The basic principal is to use smaller drivers for accuracy and space with engineered cabinets to gain frequency response with higher levels. Many of the designs also incorporate phase shifting switches on the crossovers. The transmission line theory has never been fully developed because it’s so complex. IMF and TDL probably had the best designs.

IMF’s are hard to find vintage speakers. Do you know if you saw the "ALS40" or "ALS40II Studio"? They look the same but are radically different. ALS40’s are a compact smaller breed of IMF's, but great for near field monitoring. The ALS40’s are more abundant on the used market then some other better models. They used an 8" bextrene bass unit, 8" bextrene sub-bass unit, 4" rolled surround impregnated cone mid-range with domed tweeter. The dome tweeter was probably made by Coles. Cabinets were generally very high quality. I think part of the reason they went out of business is because the speakers where made without cost in mind.

I use a pair of IMF “Studio Monitors”, they are one of a kind. If anyone is still using them today, like me, I would venture a guess that they have had new crossovers custom made. The originals were good at the time but new ones can make those speakers sound unbelievably good. A funny thing is that Bud didn’t think the quality of wiring was an important factor in acoustics, he actually said that. Bottom line is that their great.

Anyway, I could write a huge book about this so I’ll just stop here. If you want to know more visit this link or just ask, I’ll be happy to talk more! And thanks for the great post! I don't run into many people who have ever even herd of IMF, let alone actually using them in a studio. There are a couple of factual errors I noticed on this site but you’ll find a lot of useful info including dates and timelines, frequency charts, parts that were used, crossovers, history, interviews... If this stuff interests you click on links at the bottom, they will guide you to other great websites of transmission line interest.

There is also a discussion group on yahoo called “imf-electronics”

anonymous Wed, 02/18/2004 - 13:36

Mike, thanks for your great and very detailed post.
It were the ALS40II I've listened to and they sound wonderful.

I have traced a pair of ALS40's in Amsterdam, don't know whether it's ALS40 or 40II and the guy says they are painted black.

I want them for mastering, I can't imagine these speakers are so rare, because IMHO there are very little speakers that sound so balanced as the IMF.

Actually there's a pair of TLS50's or TLS80's on Ebay right now.

Peace, Han

anonymous Wed, 02/18/2004 - 16:07

Yeah I see a few TLS50's and 80's on ebay from time to time. They seem to be most common. When I mentioned the speakers are rare, I was just referring to other models that were designed specifically for studio or reference use and are still in decent shape.

Notice that the TLS 50's that are on eBay are not the "TLS 50II Studio" that has major differences. Not all IMF's should be used to reference on just because they sound good, some of his designs were ment to be colored. Even IMF's in poor shape fetch good money on the used market.

Anyway you seem interested so do all the research and keep your eyes peeled for some. Look for TDL too. Europe probebly has more floating around.

anonymous Mon, 03/01/2004 - 09:37

Like you said, they're one of a kind.
I've listened to all kinds of music and these speakers seem very neutral sounding to me.

A very nice low end, the mids are not spectacular, but very neutral and the high and is quite nice and silky. The stereo image is wonderful.

If you compare the sound to the NS10 for example, you can hear the NS10's +7db peak at 1.5 khz very clearly.

I think these are the most neutral sounding speakers I've heard so far, they sound far from 'hyped', but far from 'dull' as well.

The guy I've bought them from, has sold them because his wife found them to big. Oh, I love women! :D

Peace, Han

anonymous Mon, 03/01/2004 - 11:01

I'm glad your happy with your purchase. I felt like the mids where very flat on mine. I also thought the highs sounded like tin. I tweaked the xovers and that fixed it. I might suggest you want to think about replacing your capacitors.

Do you know anything about PMC Monitors? I'm checking them out and was wondering of you ever listened to them, there a European company. Anyway, enjoy your speaks and take it easy Han.

anonymous Mon, 03/01/2004 - 11:58

Mike, I have listened to PMC monitors at AES a while ago. This were small monitors and it sounded quite impressive there.

Later I was in a studio that has PMC's, NS10's and Auratones and it was almost shocking how different the PMC's sounded from the NS10's and the good old Auratones.

The best sounding monitors at AES IMHO were the Earthworks'.

But, the discussion about studio monitors on the many forums is a never ending story. I have had so many monitors in my studio (my gearpimp comes every now and then with a number of them) and 'THE' monitor doesn't exist.

I can make good mixes on the horrible sounding NS10's because I've got to know them. I think once you know your monitors, you can mix on them.

I will get to know the IMF's the coming weeks and I will make some mixes and listen to them on many stereo's, hi fi speakers. I'm really curious how they translate, they sure sound very nice, but so very different from many other monitors as well.

Take care! :p:

anonymous Mon, 03/01/2004 - 12:36

The reason I asked about the PMC's was because they are designed on the same theory as the IMF's, which is transmission line. I'm going to try and pick up a pair of small PMC's for near-fields.

My goal is to have a couple sets of really nice speakers and use them exclusivly for many years so I can get used to them and not worry about buying new monitors and getting to know them all over again. I don't really care much about the latest and greatest or brand names, but i still take it all into consideration.

anonymous Tue, 03/02/2004 - 08:04

Mike, I believe I've heard the AML 1 and this small monitor sounds very 'big' for such a small one, but also very different from Genelecs etc.

And they're quite expensive as far as I know.

Have you had the opportunity to hear the ADAM monitors? Made in Germany and very popular among the (American)musicplayer forumites, but nobody is talking about them in the Netherlands, very odd.
They're very nice sounding monitors although the highs are spectacular IMO.

Peace, Han

anonymous Tue, 03/02/2004 - 18:20

I'm looking at a pair of TB1's. A few steps down from the AML1's. The AML's probebly sound better but I'm more of a fan of passive speakers. I just don't like the idea of amps built into the speakers, for too many reasons to list here. So I could never bring myself to buy powered monitors, but that day may come.

A nice thing about a correctly designed transmission line speaker like the PMC's, IMF's, and TDL's is that the frequency response doesn't have the inherant dips and spikes as conventional design does. Even at low listening levels you don't have to boost low-end and tweak the eq like you normally would. The frequecny response and volume hold together nicely. Good for mixing at moderate levels to avoid ear fatigue...
Do you know what i mean? If not you'll soon find out after listening to your TLS50's for a while.

Iv'e only heard one other person mention ADAM monitors, he said they were awsome, but I forgot about them and never had the chance to check them out. Now that you've reminded me I think i'll try and find some to listen to.
I used Genelec's for about a year and did not like the smaller reference type of nearfiels they manufacture, but I do like the studio monitors they make for impressing clients and that sort of stuff.

[ March 03, 2004, 01:39 PM: Message edited by: Mike Kruger ]

anonymous Thu, 03/04/2004 - 10:31

Mike, check the ADAM S3A monitors.

I have been working most of the day in the studio and used the IMF's as my monitors.
It's incredible, not a trace of fatique. I switched every now and then to NS10's and I can't believe I've spent so many hours of listening to these little bastards.

To anybody who uses NS10's, tweak them as soon as possible, get rid of that +7db at 1.5 khz.

The ALS40II's are the best purchase in a long time and only 150 euro :D

Cheers, Han

anonymous Thu, 03/11/2004 - 15:48

Hey Mike, I've just collected my third pair of IMF speakers.

I have the ALS40II, the Compact II and the Compact monitor 2's now.

Next week I going to get the Super Compact's, so I will have four pair of IMF speakers.

They all sound great, it's my intention to buy all IMF's in the Netherlands. :D

anonymous Sun, 03/14/2004 - 11:59

Mike, the odd thing is that I'd never heard of IMF before I was at that pianist's studio.

Now I have three pair of them and I can say that the Compact Monitor 2 is by far the best sounding small monitor I've heard in a very long time.

You can put them aganst the Earthworks and ADAM monitors, but the funniest part is that I only payed 80 euros for them, which is as much as $103.20

I hear details in mixes and well known CD's that I'd never heard before. And that incredible stereo image!

And when I switch to the NS10's.....sigh.

It seems to me that IMF monitors are extremely unknown among engineers, nobody else is reacting so far, same thing on other forums. When you realize they were there 25 years ago that's very odd.

Cheers, Han

anonymous Sun, 03/14/2004 - 14:19

I know what you mean Han. No one I talk to has ever seen or heard of them. I’m glad I was introduced to IMF at young age. I bought mine when I was around 14 or 15 years old. They have helped tremendously to train my ear properly. Now, as an engineer and music lover they are a prize possession to me. Your right, the detail and stereo image is amazing, I always reference mixes to mine because I hear things I would not otherwise hear.

I’ve listened to a lot of speakers for home and studio. IMF goes to show how much you’re really getting ripped off these days when you buy new speakers, at any price. It’s sad that you can’t get half the quality and sound you did 25 years ago, even if you had all the money in the world.

I think what set IMF apart was that the engineer, Mr. Fried, owned the company and was truly more interested in designing a quality speaker then making a profit. He devoted a lot of time and energy to his transmission line theory. There seems to be no compromise in design or parts to save money. Unfortunately I assume that’s why the company went belly up. Every part was just as important as the next.

What I really like about IMF’s is that their not excessive. What I mean is that there’s nothing fancy about them, they were built to a point where more expensive components become unnecessary. And what truly is mind-boggling is the price you can find them for. People sell them for peanuts if you can still find a pair in decent shape.

I know who has all the original drawings, schematics, plans, and ideas for IMF’s. It sure would be nice if I could buy these from him and reproduce some of them.

anonymous Mon, 03/15/2004 - 10:24

Mike, what's the type of the IMF's you own?

"I know who has all the original drawings, schematics, plans, and ideas for IMF’s. It sure would be nice if I could buy these from him and reproduce some of them."

That would be great! Can you get the original drivers?

I found the square tweeter to be better sounding than the circular one (like in the Compact 2).

Peace, Han

anonymous Mon, 03/15/2004 - 11:36

I own the "Studio Monitor" model. Check it out on

Last time I contacted the guy who has the origional schematics, drawings... was about a year and a half ago. His name is Shayne Tenace (616) 697-5037. Unfortunatly he did not have a single part. His motive behind purchasing the logo and IMF name was so he could start his own speaker company called "IMF Audio". The schematics and drawing simply came with the name. I didn't really like the fact that he was trying to use the IMF name to sell new speakers that are completely different from the origional IMF's. He was sort of reluctant to share any information with me about the origional IMF's.
Maybe I should call him again and talk for a while to see if I can purchase the stuff from him, since he's not ever going to use it.

anonymous Mon, 03/22/2004 - 07:37

I own a pair of "compact monitor II" models.

I own a pair of "compact monitor II" models.

Using them for mastering (and enjoying music). Almost flat frequency response all the way up, just what I need for mastering audio. Mids are REALLY good on these, the crossover is near perfect. Lows are as tight as it comes, hard to add a subwoofer with these as you immediately notice your phase gets fuct over. Best stereo image I ever heard so far and overal the sound is just incredibly detailed. The only bad thing with these speakers is you notice how bad some of your favourite cd's sound.

The information on that imf-electronics website about this model is wrong. Here's the real data:

Dimensions: 480 x 255 x 275 mm wide
Driver units: 200mm Bass/Mid - laminated cone, 25mm tweeter - soft dome.
Crossover Frequency: 3 kHz
Frequency Response: 60 Hz to beyond audibility
Efficiency: 1 m Pink Noise - 86 dB per watt
Matching Impedance: 8 ohms nominal
Recommended Amplifier power: 10 to 100 watts per channel RMS
Cabinet Finish: Walnut Veneer

In my opinion, the CM2 can easily be compared to the likes of ADAM, Earthworks or Genelec monitors that will set one back at least 4000 dollars. I got the CM2's for 80 euro :p

anonymous Thu, 03/25/2004 - 14:52

No Mike, I've had a phone call with a guy who has bought a pair of them.
He says the SACM's were also available as a DIY building project, which he has bought and he is not happy with the kind of wood they were built from, so he's going to rebuild them to the original company specs.

I would like to have a pair of them very much though, but my wife thinks they're too big :) :) :)

I have worked again a whole day long with the CM2's and they really sound very detailed. The ALS40II's however, sound very good too, but different, bigger with less mids. I have a problem with making my choice.

I found out the ALS40 sound best when standing free. I had put them in a 'doghouse' in the wall, but that doesn't work, too much 'boom'.

I don't get many responses to advers I've put on the web, it seems the IMF's are rare in the Netherlands as well.

Peace, Han

anonymous Wed, 03/31/2004 - 01:55


Hi all,

My name is Stephane, I'm the "webmaster" of the IMF website.

I'm not a professional. I just liked the IMF speakers when I was a kid, I had the opportunity to buy a pair of RSPM 25 years later. Since nothing could be found on the internet regarding IMF, I decided to fill this gap with a website + a Yahoo! Group.

2 things :
- if they are innacuracies or errors on my website I'll be happy to correct them. Just drop me a mail.

- I have a pair of Reference Standard for sale in Paris. They were used by a sound engineer who moved to Canada. Someone please buy them, because I have no room to store them ! Pictures are on the Yahoo! group.

Thank you,


anonymous Sun, 05/02/2004 - 04:09


Mike, Stephane... Behold!

Sign and me (Sign needed an extra pair of hands) picked these babies up yesterday. We had to carry them down two stories from somebody who had em stashed away at his attic somewhere in the Netherlands (our home country).

I bet Sign is well pleased right now :p

BTW Chrissy I'll try and see if I can find summat fer ya. Stay tuned.

anonymous Sun, 05/02/2004 - 08:54

>I bet Sign is well pleased right now<

I am!

I've been listening half of the night to these little fellas and boy, what an extraordinary pair of speakers this is.

I've been playing a lot of great music and heard a lot of details that are unhearable on NS10's :D

Frank Sinatra sounds great, although there are several 'plops'.

Kate Bush' 'Hounds of Love' doesn't sound very good on these speakers, although it sounds quite decent on JBL's.

A couple of number one hit songs sound plain bad on these puppies.

Tonight I'm gonna listen to Diana Krall and Norah.

Cantrell Fri, 11/30/2018 - 09:08

I have just acquired a lovely (sounding) pair of CM3s, externally in good condition.
I was told that the grille foam fell apart years ago - it would be nice (but not essential) to replace it - any suggestions?
I notice that Falcon Acoustics offer replacement capacitors and wondered whether anyone knows of suitable replacement drivers - particularly the mid-range which seems faintly "suspect".

I am a great fan of transmission line (type)speakers (e.g. B&W DM2 & Cambridge Audio R50)

HansM Sat, 09/07/2019 - 00:38

I've moved through a few IMF's over time. TLS50, Then TLS80, bought the Super Compact II because of size.
Found them to be amazing in mid and high, but a bit light in the low end.
Got a pair of ALS40II instead, great speaker.
By accident (I was not looking for them) ran into a beautiful pair of ALS40-IIa, and bought them. Amazing difference, and I am happy.
Sounds very analitical and "true".

But... now found a nice set of CM3's. Not sure how they compare to my ALS.
Since they are not close to where I live, I am in doubt if I should take the trouble and drive over to listen.
Has anyone compared the CM3 with the ALS40-IIa?