IMF owners thread!

[Andy-roo]

Super-tweaters were functional as far as I recall... the 50's have been sitting for a while after I found a set of 80's. Plan is to get all of them re-capped, and my brother will take-over the 50's as they were originally our father's.

After the re-cap they will be checked to make sure all the drivers are functioning... wish us luck!

 

[rogermatthew]

Hi Guys.

Well, after all the advice I got here a while back, today I finally got around to recapping my IMF TLS50 Mark IIs (caps from the very helpful Jerry Bloomfield at Falcon Acoustics)

First speaker, no problem, sounds great. Ran into a problem with the other one though, roll-off of high frequencies. Luckily I had a CD of test tones, and was able to pin it down to somewhere around the 3kH level upwards, so probably the problem is in the super-tweeter area (frequencies below that sounding good). Just to be sure, after checking everything, I replaced the old caps but same problem, so obviously I've done something to mess things up. I did check the drive unit connections and, no, I didn't put my foot through any of them! Oh, and the speaker was fine before.

So I'm at a loss - do any of you more experienced guys have any ideas? I'd be very grateful

Thanks

Roger

 

[mech986]

Well, the problem would be with the tweeter and supertweeter. Swap the tweeters from one side to the other. If the problem follows the tweeter, the tweeter is bad. If it stays the same, the crossover is the problem. Do the same with the supertweeter, but it might be hard to tell any differences unless your hearing is good.

If it is the crossover, check all solder joints, and touch them up if needed. Also, check the wiring and if needed, replace the wiring from the crossover to the tweeter.

 

[mech986]

Anybody know which KEF B139 is used in the TLS80 Mk. II? I just dragged my pair out of the garage and into the upstairs loft, only to find one has the TS1212 4 ohm unit from I think a KEF tower speaker (Chorale III?). I haven't had a chance yet to pull the other woofer to see if they are the same or different.

I always thought the TLS80 Mk. II, like the RSPM IV, used the KEF B139 SP1044 8 ohm unit.

 

[mech986]

Hi, I'm hoping that with your extensive knowledge on IMF you can assist me in making a decision based on a photograph.
I have the opportunity to pick up some imf's , I have no idea which model or there condition other than a poor photograph which I'll add , now here's the thing , she wants £5 for the speakers which she describes as having tatty grills BUT !! It's a 600 mile drive !!
Can you identify the model from the photograph? I'd be crazy right ? View attachment 810521

Wonder if Andyrib went for the speakers or not?

 

[rogermatthew]

Well, the problem would be with the tweeter and supertweeter. Swap the tweeters from one side to the other. If the problem follows the tweeter, the tweeter is bad. If it stays the same, the crossover is the problem. Do the same with the supertweeter, but it might be hard to tell any differences unless your hearing is good.

If it is the crossover, check all solder joints, and touch them up if needed. Also, check the wiring and if needed, replace the wiring from the crossover to the tweeter.

Thanks mech986 - good advice. I'll start with going over all the connections on the crossover, I doubt it's the caps as I've already resoldered the new ones and replaced the old ones with no luck, but I'll look at the other joints. I doubt it's the tweeters as they were fine before, but it would eliminate them as the problem

Roger

 

[mech986]

Double check any resistors or coils in the circuit, a bad solder joint or a minute break in the signal path can be part of the problem.

 

[rogermatthew]

Double check any resistors or coils in the circuit, a bad solder joint or a minute break in the signal path can be part of the problem.

Hi mech, I've checked every joint, and while I was at it put back the new caps. All seem solid to me, but the sound is still muffled. Next step will be to as you suggest, swap over the tweeter (it's happening with frequencies of 3 and 4 kH upwards, so I can discount the supertweeter for now) but that will have to wait for another day!

It would be a strange coincidence if the tweeter went just at the moment I recapped, but then stranger things happen!

I'll let you know progress - thanks again

Roger

 

[Yvan_donald]

Hi Mech the mk II woofer should be the 8 ohm SP1044,but Canuck or other owners of the mk Ii will know.

 

[rogermatthew]

Hi mech, I've checked every joint, and while I was at it put back the new caps. All seem solid to me, but the sound is still muffled. Next step will be to as you suggest, swap over the tweeter (it's happening with frequencies of 3 and 4 kH upwards, so I can discount the supertweeter for now) but that will have to wait for another day!

It would be a strange coincidence if the tweeter went just at the moment I recapped, but then stranger things happen!

I'll let you know progress - thanks again

Roger

Hi Mech - I did what you suggested, swapped over the tweeters, same problem, so it's not the tweeters. While I was at it, I resoldered every connection on the crossover board, no luck.

So, I'm guessing some other component on the crossover has suffered, which would kind of make sense, since that is what I started fiddling about with. Any suggestions how to proceed?

I have to say, everything everyone here has said about recaps is true; with the speaker that is working properly, the sound difference is amazing!

Thanks to all

Roger

 

[mech986]

Hi Mech - I did what you suggested, swapped over the tweeters, same problem, so it's not the tweeters. While I was at it, I resoldered every connection on the crossover board, no luck.

So, I'm guessing some other component on the crossover has suffered, which would kind of make sense, since that is what I started fiddling about with. Any suggestions how to proceed?

I have to say, everything everyone here has said about recaps is true; with the speaker that is working properly, the sound difference is amazing!

Thanks to all

Roger

Using the below two schematics, I would check the following:

I would specifically lift up one side of these components and check DC resistance value - R4 33 ohms, inductor L4 blue dot, and L5 grey dot for continuity and DCR. If you're anal, same for the other resistors.

Be sure the perspective switches on the back panel are cleaned with DeOxit or similar and the board solder joints are good. Then be sure they are both set correctly and the same when you test each speaker.

Did you change the two electrolytic caps there as well, the 6 and 12uf caps respectively?

From earlier in the thread, post #149

 

[rogermatthew]

Sorry Mech, I'm out of my depth with circuit diagrams - I know when to draw the line! I will check the connections on the perspective switches though, it's possible that when I pulled at the crossover I dislodged something there. I didn't change the caps on the switches, nobody ever suggested it. Incidentally, the difference in sound between the speakers is much more than these switches can account for.

Thanks for all your help though, I'll have to get someone to look at it now. Might have to wait until after Christmas, but I'll let you know the outcome, maybe post pics of my whole system.

But thank you very much for all your advice

Roger

 

[mech986]

Which switch settings are you using, straight up, or turned left (-) or right (+)? Interesting that many of us have forgotten about the switch and its circuit parts

 

[mech986]

In the above diagram, the 12uf electrolytic cap and one of the 3.3 ohm resistors is in the system in the 0 position for the midrange. In the (-) position, the 6uf and 12uf caps are both in, and both the 3.3 ohm resistors are in series (added) for the midrange, also the 33 ohm resistor is in the circuit for the tweeter. In the (+) position, both caps are out and both resistors are out for the midrange, and the 33 ohm is out for the tweeter.

Try running both speakers with the switch turned to + and see if both return to roughly equal loudness.

 

[mech986]

I would suggest that it would be important to replace both electrolytic caps on the switch as one or both will be in for either the regular 0 or - switch settings respectively. This may also apply to the other TLS or RSPM systems that run with a perspective switch and associated filtering components.

 

[rogermatthew]

I would suggest that it would be important to replace both electrolytic caps on the switch as one or both will be in for either the regular 0 or - switch settings respectively. This may also apply to the other TLS or RSPM systems that run with a perspective switch and associated filtering components.

Great advice again, many thanks!

In fact I normally listen with both speakers set to the centre position (after early experimentation) but when I got my problem, I did switch the duff speaker to the '+' setting. There was such a loss of high frequency that I wasn't expecting it to work miracles but I guess I felt there was nothing to lose. It didn't sort it out of course.

I will check the connections at the switch plate, there was so little play on the wires that it's possible I dislodged something there, even though I was careful. It was OK before, so I'd be surprised if anything just failed by coincidence at the exact moment I recapped the crossover. Could it be one of the other components on the crossover that I messed up while recapping?

Yes, interesting that there are caps on the switch plate, I'm surprised there has been such little attention paid to it.

I'll have a play later in the week when I get time

Thanks

Roger

 

[mech986]

Will be interested to hear what you find. BTW, where are you located?

 

[rogermatthew]

Will be interested to hear what you find. BTW, where are you located?

The UK!

If you're ever passing ...!

 

[rogermatthew]

Will be interested to hear what you find. BTW, where are you located?

Hi mech. Guess what - I fixed it!

I had another hard go at it today, went over all the connections of the 'faulty' crossover and noticed a small nick on the edge of the board. It may well have happened when I first removed it (the retaining ties were bound quite tight). This had caused a small break in the continuity. A bit of resoldering with copper strip and all is now well!

Was it all worth it? You bet! I cannot believe what a difference the new caps have made, everything everyone has ever said is true!

So my thanks to all at the forum and especially you mech. It's always reassuring to have someone pass on their experience, gives confidence when working in an area where, frankly, I don't have a lot of experience.

Just one more thing please: the speaker has two foam rectangles towards the bottom of the cabinet (I presume at the end of the transmission line duct), they are both brittle and beginning to crumble, through age I guess. Any suggestions as to whether to replace them or leave well alone?

Anyway, I'm off to have a good listen now - something I've been looking forward to!

Thanks again

Roger

 

[mech986]

Lovely, its always something so little that defies first examination! Glad you have a working pair of speakers now. Snap a pic of the foam rectangles and we'll see if there's something that could be used. Falcon or Wilmslow might have foam that could be used, although I'm not sure it would be quite the same shape.