IMF owners thread!

[montrecott]

I purchased a pair of restored Super Compact 2 from RDSChicago on Barter Town a couple of month ago and have been enjoying them ever since. They really sing with a Luxman R1120a. Very good bass for speakers their size, along with that classic British midrange. Here's one of them.

 

[IMF_Pioneer]

The Super Compact in both variants (Mk I & Mk II) was probably IMF's biggest selling speaker worldwide and as such is still very much enjoyed by many and thus they still fetch top money when good examples become available.

 

[montrecott]

The Super Compact in both variants (Mk I & Mk II) was probably IMF's biggest selling speaker worldwide and as such is still very much enjoyed by many and fetches top money when good examples become available.

I was fortunate to get a good deal on mine.

 

[BGS57]

Hi
I have just found a pair of IMF ALS 40 ll, and the surround of one of the sub basses have gone loose from the cone edge and is irrepairable, so I need to get some new surrounds. Now my question is.. what should I get? Foam or rubber? The original surround is a shiny rubberish thing, inverted.
I`m also in doubt if the size that I should try to find is 8" , 20,5. The Speaker is an Audax HB20 B25 /0376, but I can`t seem to find anyone who sells surrounds for these
I have done surrounds before but never an inverted one... and it`s difficult to see if the original one is glued on the outside or inside of the cone.
I have searched the internet far and near for an answer to my questions, but have not been able to find anything. Maybe the original surrounds will last forever and I just have been unfortunate to find a pair with a hole poked though them.
Any solutions what I should get will be highly appreciated as I`m really looking foreward to listen to these speakers. Thanks.
Kind regards
Bjarne

 

[mech986]

Bjarne, Welcome! Can you post a pic of the woofer and the area where the surround has either come off or been damaged? Also, can you provide a picture of the model markings as there were a number of variants of the Audax HD20B25 where there may be additional numbers which detailnthe voice coil windings. The 0376 is a production date code. They do show up on eBay Europe, Uk, and US Canada from time to time.

Rubber surrounds are hard to source since they don’t fail often. A foam surround may be your only option. Check goodhifi.com for some options.

For repair, You may need to measure the following:

1. Outside diameter of the cone edge.
2. Inner and outer diameter of the surround roll
3. Width of the surround glued to the cone.
4. Outer diameter of the surround glued to the frame edge.

 

[BGS57]

Thanks for your reply and welcome,mech986. Here`s a couple of pics of the driver. It`s very difficult to see what is actually stamped on the magnet. The surround has broken close to the cone and it`s ripped as well. I really have to be carefull when I try to remove the old surround because it`s very well glued to the cone and don´t come off easily(Iso-propyl-alcohol??) At the moment where it`s still attached to the cone I can`t really figure out whether it is glued to the outside or inside of the cone as in above or under.

 

[IMF_Pioneer]

As far as I'm aware there are no replacement surrounds available for this speaker. These generally just do not fail unless treated badly in some way.

As previously suggested you will have to keep an eye out on the bay for a replacement.

If all else fails some very delicate gluing will be the answer but remembering that a flexible but strong adhesive will have to be utilised, such as Sikaflex which is very much used in the Automotive industry. It is very strong but still rather flexible which is what you'll require.

 

[JimPA]

Thanks for your reply and welcome,mech986. Here`s a couple of pics of the driver. It`s very difficult to see what is actually stamped on the magnet. The surround has broken close to the cone and it`s ripped as well. I really have to be carefull when I try to remove the old surround because it`s very well glued to the cone and don´t come off easily(Iso-propyl-alcohol??) At the moment where it`s still attached to the cone I can`t really figure out whether it is glued to the outside or inside of the cone as in above or under.

View attachment 1419578

View attachment 1419577

I would contact Bill at Millersound / he will know what to do.

My best guess is that you will have to use a butyl rubber surround.

 

[mech986]

Bjarne, yes, very tough to make out the markings. Do you have the matching driver in the other channel to pull and also take pictures of the markings? If you do, try taking the photo from an angle below or above the markings, not directly overhead. \_/ That might help to bring out the markings a little. Also, I think I see an 8 which may indicate 8 ohm nominal. If you have a multimeter, take a DC resistance reading of both woofers which can help us determine if 4 or 8 ohm types and maybe even the length of the voice coil (usually longer is a little more resistance). Also, if you have an inductance meter, you can determine the inductance of the voice coil.

Additionally, there is a measurement of the height and circumference of the magnet, which makes up the H or J models (H is larger magnet and stronger motor). As I mentioned before, a lot of variants of this woofer were in production. Take a good look at the back edge of the cone. I suspect you will not find an overlap of the surround there, and the surround is glued onto the front - the likely issue is there is also a coating which is painted onto the front of the bextrene cone for dampening and it may have been painted onto the surround also, making it very difficult to see the edge of the surround.

Nice source for some archived Audax catalog listings. http://www.audax.com/archives.php I also have a couple of old Audax (FR), Polydax (US) and Sonaudax (UK) catalogs somewhere around here too.

http://www.audax.com/archives/hd20b25h.jpg

http://www.audax.com/archives/HD20B25H - Catalogue 1982.pdf

 

[BGS57]

I can see a figure 8 in then right end of the stamping..so it must be an 8 Ohm. I have enclosed some pic of the edge and I`m almost sure that the surround is attached to the top of the cone...inside... and that it is coated with something.. Any ideas what to use to soften it and get it loose...Iso-Propyl alcohol is what I have at hand if that can do the job without damaging the cone.
It`s not an option to repair the damage as far as I can see as the stretch to attach it to the cone again would be too much for any glue to hold. So I will look out for some butyl rubber surrounds... but first I have to get the old one of...





Sorry if the most important pics are a bit blurry..but that`s what the camera can produce to day.

 

[mech986]

Personally, I’d suggest NOT trying to remove the old surround from the cone - reason being the cone is made of bextrene, an expanded polystyrene plastic that may react to any solvents, even isopropyl alcohol, and the plastic dampening coating is similar to PVA glues like white glue which can absorb small amounts of water or high humidity.

What I would suggest is to gently remove the decorative white circular trim ring around the outer surround and frame edge. Then using a small but sharp knife blade (here in US we would use an Exacto blade type instrument) and carefully cut the surround out along the edge of the cone - this can be done from in front or possibly from behind depending on access and visualization. Final trimming would be from in front for best cosmetic appearance. Then You can easily remove the rest of the surround from the frame edge and any glue that is left.

Then, if you’re lucky, you might be able to see any glue gaps that could help you split the remains of the cone surround from the cone, taking care to trim and hopefully keep undisturbed the front cone coating. This is where it gets tricky and may result in uneven removal of the remaining surround, maybe even leaving chunks that won’t release from the cone.

The alternative is to simply leave the ring of old surround firmly glued in with its cone coating intact. Measure the thickness of the surround and then make a ring of similar thickness from paper card stock or thin plastic sheet to fit and glue on the frame edge where the new surround would glue onto - a spacer to lift the outside of the surround the same thickness as where the inside of the surround would glue onto -voila, no offset up or down with the new surround, theoretically.

Now here’s the issue. With any replacement surround, rubber or foam, you definitely want it to be very flexible, as flexible as the original was. You also need the dimensions of the outer diameter edge, the outer and inner roll diameters, and the diameter of the inner edge glued to the cone to be very very very close to original. You probably could get away with a roll width a little narrower if needed. But you’ll also need the inner overlap section, which will be glued to the cone, to be angled so that it lies flat on the cone when glued down. You’ll also have to determine that the roll is either convex (roll upwards like most speakers are) or concave (roll downwards like originally done). The available surround replacements may dictate which angle and roll position works for the surround you need.

 

[BGS57]

Thank you for your detailed advices. I´ll keep the Iso-propyl alcohol far away from the cones then....I have a few old razor knifes laying around which could be usefull for the job of removing the old surround from the edge of the cone, they could be perfect for that job. I`ll come back with photos of a hopefully well done job when they are finished and ready to be put in the speakers again. Thanks to everyone for your suggestions, I really appreciate that. What a great site this is

 

[Jogi]

Hi everyboy!
After reading the whole thread and listening to a pair of TLS80 at a friend, I couldn't contain myself and drove 600km to pick up a pair of cosmetically gorgeous Tls50 Mk2. I knew that the midrange drivers would need reforming or replacement, so I ordered the Monacor from somewhere here in Germany.
The former owner had replaced the wiring and all caps. Unfortunately the workmanship is rather shoddy, and the wire some garden hose size. I detected some errors and one broken connection, and replaced some caps again for MKL Siemens NOS Film caps, as they have the same size as electrolytic and sound better to my ears.
Ok, they both play nice tunes now connected to a powerful TI TPA3255 amp, which is capable of putting out some 300W with a good amount of damping the woofers, which are rather wobbly.
Midrange is really good, silky and smooth and open, especially after replacing the 3.3 ohm resistors which go to the midrange drivers. I chose some 10 watt metal band MPC resistors from Fukushima futaba, which are a good and affordable upgrade to the stock wirewounds.
They opened up the midrange quite a bit.

Ok, here comes the bad news: listening today I realized that something is off, and checked the Coles supertweeter, and of course one of them is dead. And no way I could repair it regarding the closed microphone capsule and the super thin wire.
So, my question is, if someone here has a Coles (or STC) tweeter capsule or whole tweeter and is willing to part with it? The ones at Falconacoustics are a mere 120€ a pair, and I want to try first here, before I pull the trigger on these.
Or... maybe there is a replacement, like for the mids? If yes, let me know.

Ah, and while I am at it...The bass is too much in my smallish room, but only when it hits certain frequencies. Has anyone made some experiences with damping the line with some more or less foam? Really want to keep them, as they are quite something otherwise.
Thanks, and all the best, Juergen

 

[P. Hageman]

This evening I bought me a pair IMF super compact speakers. They are in near perfect condition and have all the original internals. I bought them from someone who was in his seventies and always dealt in audio and speakers, according to him these speakers can be regarded as the best that was made in the 70's. I don't know if that is true, but he certainly knew his stuff. When I asked if the speakers needed new capacitors he waved his hands.No, no, no, he said, leave them original, they sound perfect and the capacitors they used by IMF were as he called the "wax capacitors" with 10% tolerance and they do not deteriate? I am realy happy with these speakers and will hook them up tomorrow

 

[IMF_Pioneer]

Hi PH,

Not quite sure I'd go as far as saying what your seller did, but yes they are amongst the better end of the scale of speakers from the 1970's. The TLS-80 Mk II's & RSPM Mk IV's are certainly far superior but then they are of a different classification I guess.

I to have always had a bit of a feeling that this capacitor replacement craze is a tad over rated on these particular "Elcaps" as when I recapped my Mk IV's I really didn't feel that there was any major wow factor afterwards. I strongly feel that it all depends on how the speakers have been treated over the years and in what climate they've been located in. As I'm in Australia, we are in probably the driest continent and also being in South Australia the driest state as well apart from the Arizona desert and thus why my caps have survived all this time.

BTW I have 4 sets of Super Compacts in my inventory of speakers, 3 sets of Mk II's and one set of the original IMF International Mk 1variant. None have been recapped, only new surrounds on the troublesome midranges and as such they still sound fabulous after all these years. The Mk 1's are being used on a daily basis in my family room system, so no issues there at all.

 

[dubai2000]

I would like to add my experiences with IMF speakers. I actually discoverd them by chance because a friend of mine who actually wanted to get himself a pair of ALS-40II decided not to do so and so I stepped in (he has got himself to different pairs of IMFs by now ). I checked at the seller's place to see if all drivers were playing and there was something in their "sound" that made me take them home. Connected them to my own gear I was immediately struck by: their naturalness,clarity and the quality (cleanliness) of the existing bass. I was told that caps had already been replaced and I believe that is the case because:
Having been mightily impressed by those "smallish" models I decided to upgrade - and as there was a pair of TLS-80 (MKI) offered not too far away, I decided to get those as well. And even without having done anything to the crossovers I found them to be the most complete speaker I have ever owned.
Right from they sounded very similar to the ALS, but you could also tell that they were a tiny bit tired/less fresh. Hence I ordered a set of replacement caps from Falcon (for the electrolytic caps). After installing them I noticed a similar "freshness" to those ALS but, as human beings are curious, I also began toying with the idea of replacing all the other parts on the crossover (film caps and resisitors - switch section included).
Obviously doing that is a controversial issue but as I had done the same in other vintage speakers, I was optimistic that I would like the outcome. I decided to use ClarityCap CSA for the 2.2 uF, Siemens MKL for the 6uF caps (which originally was not a 6.8uF cap as shown in a pictue soemwhere in this thread), and the new 60uF and 100uF from Falcon I bypassed with a combination of Russian PIOs and very tiny Teflon caps). I case I wouldn't like the change I could always put the original film caps back in again. But fortunately I am a happy camper.
Has the overall voicing of the speaker changed? Well, to my ears not really - it still is an extremely open and natural sounding speaker - just perhaps a bit fresher and even more revealing.
When listening to large orchestral pieces such as Holst's "Planets" you really notice a lot more than with other speakers that orchestras consist of individual players and as a group their sound does have weight, not just loudness - just like in real performance. I think not that many speakers can convey this in a way the IMFs undoubtedly do - and in the light of that, even TSL-80s are actually kind of - "small" .

 

[BGS57]

Hi again
So I finally got my surrounds...I took a chance if they would fit and they sort of do. That`ll be... they fit better in the normal position that in the inverted ditto, as I think the gab between the surround and the cone edge will be to big and difficult to glue on. So before I glue them on in the non-inverted position I have to ask if there will be any disadvantages by doing so sound wise. Off course they won`t look as the originals at first sight but apart from that? Otherwise then I will just try to wrap the surrounds around the cone edge even if it`s a bit more difficult to glue it and hold it in place. Suggestions please?

 

[dubai2000]

This thread has become kind of quiet - I suppose interest in certain brands come and go (unless they are very 'big') - anyway: I have spent some more time my my IMFs and the longer I listen to them, the more sensitive they strike me to be. Different to what has been stated in some previous post I find them quite touchy in terms of placement and parts used for re-capping. For example their ability to present music in way that moves away from the speakers is quite dependent on how far they are apart (and in my room and to my ears a few centimeters do make quite a big difference). The same applies to the tonal balance and hence again their ability to "disappear". For example I used the same Russian PIO as bypass for the 12uF cap that sits next to the switch at the back of the speaker as I had used across the 60uF cap - and after a few days I noticed that I was listening less attentively and with less pleasure than before - there was a subtle change in tonality and the ability to reveal the recording venue had dimished. Removing this cap and replacing it with a different kind of cap (of the same value!) made a (positive) difference. Obviously this applies to my ears, room, gear etc. - but what surprises me is how very fragile the right balance of those speakers seem to be.

 

[Yvan_donald]

Hi, it is evident that you need a certain distance between both speaker's and from yourself , depending on the type of capacitor you use,it does make a difference. IMF are less affected from back wall and side wall, compare to others speakers.Transmission line give you very clean bottom,myself invest quite a sum to bring the best of them.At the age these speakers are for sure you to do a good x-over job.Some people like more midrange,but depends of your gear you have to drive them, big amp is really a must for them.Myself have in the past problem with the clipping of amp,now what I have drive them with breast.Falcon acoustics is the best to put you on the right track. Best regards,Yvan.

 

[AndreasH]

Hi all,
my IMF are still original except for the front cover, here was a foam that crumbled by touching it. Because I don't want to do any experiments here and don't know the components very well,
I won't change anything in near future. I believe that a revision of the crossovers can bring new/old freshness into sound.
I have had the same experiences with positioning. My Professional Monitor are uncritical when it comes to wall distance, but the listening position makes a lot of difference.

Since my good old Marantz PM-64 mkII (100W / 8Ohm) died, the loudspeakers were connected to my Marantz PM-66 SE KI which has half of the power.
Now I got an Yamaha A-1020 (125W / 8Ohm) and there is a big difference especially when listening to soft music. And of course more pressure in the bass range.
So they really need a lot of power to show their quality, I think more power would be even better ;-)