IMF owners thread!

[AndreasH]

Hello IMF owners,
I own a pair of IMF Professional Monitor. Found some information about them but nothing about recommended positioning in the room.
I am currently working on a dedicated stereo listening room in the basement of our home. Building acoustical treatment is in progress.
So I wanted to ask if somebody knows recommended distance to back and side walls.
Are the speakers sensitive when setting them up?
I need a good starting point for positioning.

Hope somebody can help me.

regards
Andreas

pics:
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[Yvan_donald]

Hi, welcome Andreas, IMF are easy speakers to place, back wall and side wall do no really affect the sound, you don't have to toe in to much, you don't have to be in the sweetspot to enjoy them, Best regards,Yvan.

 

[AndreasH]

Hi Yvan,
I thought so already because the sound when sitting at the computer desk was very good. Now I have the confirmation.
I will now attach the original stands and start with listening

Thank you very much for the useful information.

Best regards
Andreas

 

[AndreasH]

now I just want to introduce my IMF speakers here.
The Professional Monitor: got them in a really good shape, only the foam front cover was no longer usable

The Compact II:
they were in a bad shape, I had to put in a lot of work




regards
Andreas

 

[IMF_Pioneer]

Hello Andreas,

Good to have a fellow Austrian (Ostereicher) on board here on the IMF dedicated thread. I used to have a set of PM's just like yours but just couldn't hang on to 3 sets of the larger IMF variants. I ended up keeping my TLS-80 Mk II's and RSPM Mk IV's. As Yvan has already suggested you'll find the PM's very forgiving in their room placement, but in saying that every room will colour the sound a little. With that you'll just have to experiment a little to what you personally like. Rest assured you won't spend much time doing that, rather more time enjoying the music.

If I may ask how long have you owned these lovely examples ?

BTW. You have don'e a lovely job with those Compact II's. Removing coloured paint is always a difficult task without leaving any traces behind and not going through the veneer. I'm currently restoring a set of SL6 Celestions with the same sort of issues.

 

[AndreasH]

Hello IMF_Pioneer,
yes I am from Austria. We don`t have Kangaroos (except in the zoo) ..

I got the Professional Monitor from my father in law, he used them to listen radio in his office.
At some point I persuaded him to swap them for my Sony speakers. I think I own the PM`s about 17 years now next to my Audio Physic Spark.
They are a bit big for the living room but they will have a fine place in my new listening room.

Wish you much luck in restoring your Celestions.

regards
Andreas

 

[IMF_Pioneer]

Hi Andreas,

Wow that's an expensive set of radio listening speakers he had. Did he buy them new or simply pick them up for a bargain price second hand and then decide to use them for what he did ?

I'm just absolutely blown away by someone using these for just radio sound in an office.

Cheers.

 

[AndreasH]

As far as I know he got them from a relative who emigrated overseas. They were stored in a room in his office until he used them again.
I just needed to free them and give them true purpose ... I am very happy to own them now

 

[h.elf]

Sorry for late reply, had to dig through my papers for the values, -
Not 100% sure if they are correct, I think they look kind of low..?

Inductors:
L1 brown dot = 2,75mH - 0,16 Ohm
L2 no dot = 0,8mH - 0,16 Ohm
L3 yellow dot = 0,5mH - 0,13 Ohm
L4 blue dot = 0,42mH - 0,11 Ohm
L5 white dot = 0,24mH - 0,09 Ohm

Hi,new in this forum,and need your help,I have exactly same speakers same crossover.but I forgot the connection on the selector.the +(blue and small wire brown from medium selector)right?
Or smal wire brown with black wire(-)?
Thank you for replay and best regards.

 

[Pilsern]

Hi,new in this forum,and need your help,I have exactly same speakers same crossover.but I forgot the connection on the selector.the +(blue and small wire brown from medium selector)right?
Or smal wire brown with black wire(-)?
Thank you for replay and best regards.

My notes from back then -



blue goes to + on the terminal

 

[h.elf]

My notes from back then -

View attachment 1341171

blue goes to + on the terminal

Thank you,
Ok,but if I put the short wire brown with Black one( -),I have no medium.
Look at the foto left side
I must take a foto before opening
Regards

 

[Pilsern]

Thank you,
Ok,but if I put the short wire brown with Black one( -),I have no medium.
Look at the foto left side
I must take a foto before opening
Regards

Yes you are right - according to my notes only Red and Black to (-) terminal.
I don't have my TLS50s any longer so unable to check.

br

 

[h.elf]

Yes you are right - according to my notes only Red and Black to (-) terminal.
I don't have my TLS50s any longer so unable to check.

br

Thanks a lot.

 

[dogwan]

IMHO I feel that this set has had all it's original internals gutted and replaced by some test pilot at some point in time.

As there is no information and also hardly any examples of this model speaker around, I very much feel you are going to have to be your own ears pioneer, much like the previous owner of this set was it seems.

I believe you are right. I've started replacing the approx. 1" fiberglass stapled to the sides and top behind the drivers.


I also was able to locate some fiberglass intended wrapping pipes. It's unfaced and is 1/2" x 3" x 25'. Was able (just) to slide strips down and maneuver between the dowels and the back. I stapled at the top so the strips are hanging down into the beginning of the TL. That was a royal pain in the arse getting my arm down into the cavity and positioning the bats.


My plan is to add loosely distribute some sheep's wool down among the dowels to tune the damping.

Can anyone tell me what to expect from the sound if either under stuffed or over stuffed? Is it like an Avacado ripening? Almost, almost, too ripe?

 

[Yvan_donald]

Hi,the crossover should be install glued on 1/2" foam on the flat at the bottom of woofer,for you to have an easy access,like all IMF,you should cover completely the top back section over the switchs and speaker posts.Yvan.

 

[dogwan]

Hi,the crossover should be install glued on 1/2" foam on the flat at the bottom of woofer,for you to have an easy access,like all IMF,you should cover completely the top back section over the switchs and speaker posts.Yvan.

Yeah, I know. In that shot the speaker was laying on its back.I tacked the crossover into place there temporarily because I was rolling the cabinet back and forth to get my arm in. When permanently place the crossover underneath the woofer I'm using 1/2" standoffs instead of foam. Didn't like the corrosion the glue caused on the traces of the PCB.

BTW, I finally stumbled on a pic of "The Studio" with the woofer pulled and a shot of the stuffing behind.....

 

[Yvan_donald]

Hi,nice job by the way,I don't thing you're IMF should have the fiberglass in the lower part of each side panel inside the line because my prof. don't .Did you find some staples lower to the entrance of t-line behind the woofer?Yvan

 

[dogwan]

Hi,nice job by the way,I don't thing you're IMF should have the fiberglass in the lower part of each side panel inside the line because my prof. don't .Did you find some staples lower to the entrance of t-line behind the woofer?Yvan

No staples low on the entrance to the line. But, if you look back to my earlier photos looking down at the dowels in the 1st section of the line you can see there's a glue ring on each dowel at about the mid-point. This is on each dowel. I can feel them with my hands. Because I did manage to see sets of dowels in the middle section of the line and there's definitely a sheet of fiberglass in that section, I think that indicates there was something in the 1st section.


I know it's hard to see and the resolution is not great, but this cross-section was taken directly from the IMF speakers web page for "The Studio". If you look closely you can see the bat in the middle represented. Also a similar looking bat (or two?) in the 1st section.

In the upper corner behind the drivers the cross-hatching seems to represent some other kind of loose stuffing. I'm thinking this may be why there are two cross dowels about 2 inches below the top panel. There is also a 3rd dowel about 2 inches above the bottom ledge under the woofer (I'll try to take pictures next time I have day light in my garage). Maybe this is Lamb's wool? Also look at the 1st bend. Is this more Lamb's wool?

It also looks like the last section of the line is stuffed denser than the other sections. I did find staples with tufts of pink fiberglass at the exit to the line. I also infer that this means there was stuffing in the last section of the line as well. Could that be a full thickness bat of fiberglass?

 

[sac]

Hello


New to these forums, but not new to IMFs.

I have a pair of IMF CM2 and a pair of CM2A. and also had a set of TSL80Mk2 for quite a while.


The CM2s I have had seen new, and the CM2As bought 2nd hand 15 years ago. (I’m guessing they are both about the same age, manufactured 1980-81, (both with the foam grills that have now fallen apart...but made some nice new cloth framed ones that use the orignal velcro holders)


As far as I can tell the speakers are identical apart from the CM2 being ported?


Ok, here is my problem. Even though when I bought the cm2A I was satisfied with the sound and a full frequency sweep revealed that both tweeters and woofers were working correctly, I have now identified a problem with them.



They are currently being used as surround speakers in my home theatre. I am running a Denon receiver which runs the Audyssey microphone calibration set up. In looking at the equalisation curve for the cm2A it was showing that they are flat up to 2 kHz , but needed 6dB(that the maximum Audyssey can give) of boost in the 4, 8 and 16k bands, whereas the CM2s were relatively flat across the spectrum. Swapping speakers about the room and indeed using the cm2A by themselves as mainspeakers showed that they were consistently down by 6 dB above 2 kHz, possibly more given that is the max boost audyssey adds.

Were the tweeters not working? Well testing with high frequency tones revealed there were(and physically blocking the tweeter directly did have an effect on the output-so it wasn’t just high frequency getting reproduced by the woofer), just quite a bit down compared to the CM2s. Interestingly Audyssey was showing that within the pairs each speaker was within 1 dB of being identical to the other.


Interestingly I hadn’t use either pair as my main speakers for over 20 years and was surprised to see how good they still sounded when driven hard when I was comparing their responses..


Questions:

1. Was that the way they were made(the CM2A), or have they deteriorated.(unlikely they would have been 6 dB in the top end at the time?)

2. My understanding of the audax tw1500F tweeters is they work or they don’t work, their output shouldn’t decrease with time?

3. Are we looking at problems in the cross overs of the CM2As……..I suppose I could answer this for myself if I opened both speakers up and played tones through the respective woofers and tweeters bypassing the crossovers.

4. Are the crossovers different for the two types of speaker, or perhaps made at a time when one supplied component was not up to it?


At the moment, given Audyssey has spectrally taken care of the problem in my home theatre setup, it perhaps doesn’t matter, but would still like to get on the problem if we decide to do something else with the cm2A


Suggestions on where to go from here. (apologise if this is covered somewhere in the 84 pages so far)


Thanks


Sac

 

[IMF_Pioneer]

Merry Christmas to all the IMF Owners around the world !

Cheers.