IMF tls 80

[RichmondMark]

I'm looking for advice. I have a chance to pick up a pair of IMF tls 80 speakers. They look like they were modified to replace the tweeter/super tweeter with a single tweeter. The mid and woofer are in great condition. I've seen discussions about modifying them from 4 to 3 drivers so I guess that might be ok. The picture I was sent looked like they did a clean job but I suppose there is a lot involved with the crossover, etc. I just don't know if I will be capable of evaluating that on the site when I go to look at them. These were highly regarded speakers as far as I can see. So I guess my question is...if you weren't sure about the tweeter situation would you still pick them up for $200.00. Seems like a good deal to me regardless. What do you think?

 

[sealy]

For sure. The B139's are worth that much on their own. Throw in the B110 mids and you've got a good deal. It shouldn't be too much trouble to locate the original tweeter/super-tweeter, if that's the route you choose to take. The current tweeter appears to be a ring radiator.

 

[M Jarve]

The only issue I can really imagine that might creep up is that the TLS-80 (and many IMF speakers) used a series crossover (one of the reasons they can't be bi-amped). Changing from a 4-way series crossover to a 3-way one (or a 3-way parallel version) would require changing the entire crossover, if done properly. If they simply took out the original and super tweeter and stuck something in there, I would highly recommend going back to the original configuration. If, on the other hand they did it properly, it might be okay to leave them as is.

$200 is a no-brainer price for those- in original condition, they might fetch 4-5x that. Figure another $200-300 to make them original again (if you're so inclined) and you're still ahead in the game.

One thing to remember when listening to them (and remembering why they're a 4-way system) is that when they were designed, tweeters with smooth, very extended frequency response were uncommon. This was compounded by the fact that the design required tweeters of low sensitivity to match the output of the bass and mid TL systems. A 4-way system was the best way to accomplish this at the time. Tweeters have gotten better over time, but I would still be worried that a more modern and sensitive tweeter would impart a stronger sound than the original design.

 

[RichmondMark]

OK. Thanks. great advice. Sounds like I can't go wrong. I needed a push in the right direction. Given confirmation on the no brainer price I'm gonna pick them up in the morning. I'll circle back around and tell you my thoughts after I get them.

 

[Spalls]

OK. Thanks. great advice. Sounds like I can't go wrong. I needed a push in the right direction. Given confirmation on the no brainer price I'm gonna pick them up in the morning. I'll circle back around and tell you my thoughts after I get them.

Good choice. I suspect that you will be happy with these once you work out the bugs. :yes:

 

[kmanusa]

I've had 2 pair of the IMF RSPM Mark IV, the very similar but slightly larger brother to the TLS-80. I seem to recall that either the tweeter or super tweeter were very rare and hard to find used-- FYI.

 

[Arkay]

You'll be glad you got them, even if it takes a while to sort out the tweeters. They were among the very best speakers made in their day, and are still sonically desirable; the transmission line bass on those is amazing! :yes:

Get them, figure out what you have (what was done and not done to the crossovers, etc...) and use the internet (the experts here on AK and other resources like CL and eBay, etc...) to get the information and parts you need to make them "right" (if they aren't). These speakers are definitely worth putting a little effort into.

 

[MunkeyQ]

Looks like a rather nice ring radiator tweeter it's been replaced with though...hate to say it, but if the crossover has been modified appropriately, it may even sound better than original! The Celestion 1300 is playing up to its practical upper frequency limit in there. If they're just been wired in place of the supertweeter without the appropriate mods, then by all means revert to the originals.

Originally, they would have had Celestion tweeters and supertweeters - model 1300 tweeters and 2000 supertweeters. The 1300 isn't hard to find on ebay as it was used in loads of Celestion's own speakers, but the 2000 might prove tricky. Correct me if I'm wrong, but the Coles 2001 might be an appropriate replacement.

And yeah, $200 is an excellent price! Enjoy them, and get some serious amplification behind them to get the best out of them...efficient they are not. Some users have swapped out the lossy laminated iron core inductors with air core equivalents with good results. The caps will be well past their use by date (Elcaps!) and it's well worth replacing them.

Edit: crossover schematic is here if it's of any use.

 

[RichmondMark]

Thanks...A lot of good information here. I ended up picking them up this morning. They came from a smokers home and judging by the film I'm assuming that was the case for years. So they really need a good cleaning. Looks like the grunge will come off...maybe a diamond in the rough.

The seller actually acquired them from a relative who passed away so they could not enlighten me on the modification. I'll know better where I stand on that once I play around with them a little.

The advice, schematic, etc. are appreciated.

 

[RichmondMark]

OK, so I had a chance to give the speakers a listen. I'm really excited. So let me warn you in advance about the long post. I'm no expert so I need some guru assistance. My initial take is that I am really going to like these -- I can see what the buzz is about. However, they are definitely going to need some work. That's where I may need some help.

First issue: As discussed they have been modified to one tweeter. The tweeter is a Peerless (Vifa?) XT25TG30-04 ring radiator which seems to he highly regarded from the reading I've done. But I don't know what they did with the crossover yet. I want to check that out but (1) I'm not sure how to access it. Do I need to take off the front panel of the speaker which I guess would mean disassembling the drivers etc? Any help here would be appreciated. And (2) I don't think I'm qualified to determine if they did a good job reworking the crossover (from a design standpoint) once I find it. I may need help with that once I can pull it out.

Second issue: Now, it is possible that the speakers will be great sounding with the current drivers at least for a while (without going original). The first issue above will help determine that. But I'm having trouble auditioning them. The right speaker sounds fantastic. But, while all the drivers on the left speaker seem to be functioning (I'm not sure how to describe it) it is not as full a sound. When I'm off access in a different part of the room they sound wonderful...I think...these are fantastic speakers. But when I sit in front of them the soundstage is skewed to the right. I think it is the mid range. I can fade back and forth and and the left speaker just is fainter in what I'm thinking is the midrange frequencies. Vocals for instance are stronger from the right speaker -- they are not missing from the left one...just fainter. When I cup my hands around my ear and hold them up to the midrange/tweeter on the left they both seem to be working. I'm not sure how to attack this. Could aging crossover capacitors cause this? Or can a driver get older and just perform at a lesser level without failing completely. I did try them out with different amplification and sources and the outcome is the same.

Third issue: There is a circuit (with switch) mounted on the back of the speaker terminal (inside the cabinet). It's a three position "perspective control". Does this also need to be recapped or can I just leave it alone in the middle position with no potential issues? Do you think this actually performed a worth while function or is it just an unneeded bell/whistle?

OK...that's a lot. It's just that I'm excited about getting these up to speed because I can definitely see the potential. Anything you can help with would be greatly appreciated.

 

[cabinover]

I know that new caps in a pair of Cornwalls I had brought the highs back from almost non-existance compared to when I bought them.

That presence switch could also need some cleaning, maybe its corroded and not letting all of the signal through? It is in series with the midrange speaker according to the schematic posted above.

 

[krimney]

Imf

I'm guessing the super tweeters quit and were removed. I'm also guessing that there has been nothing done to the crossover to accomodate the new tweeter.

What I'd do first is to get a pair of matching tweeters in the cabinets. it is hard to compare two speakers when they have different drivers. I'd then go through the simple things, like making sure the wiring is all intact and correct.(maybe something was switched when the drivers were out. make sure the mids work. If they are original B110, then they are fairly common, but if one is weak, pull them both and put in a pair of known working mids, that will let you know if you have a crossover problem or a mid problem. clean those controls on the back.

If you can't find original tweeters, you might consider a Kef T27 tweeter. these were paired with your B110 and B139 in the Kef concerto.

Is the original tweeter in the other cabinet a rectangular peerless? they are common enough.

 

[RichmondMark]

So I will try cleaning the switch first. That's a good point.

The tweeters are matching...both the peerless/Vifa ring radiator. So I could do a side-by-side even comparison but for the other issue with the left speaker. Not sure about the crossover yet...you may be correct. I guess if the crossover was not modified it would make reverting to the original easier. Then again I was told that a proper modification might result in something that's very tolerable (and if lucky even better?). In the end, value wise, going original would probably be my best bet.

I was hoping for a little advice from someone with experience with this model on accessing the crossover. There's a lot going on in that cabinet with the foam, walls etc. and I'm looking to avoid a mess.

Thanks for all this info so far...

 

[ColinR]

There is a circuit (with switch) mounted on the back of the speaker terminal (inside the cabinet). It's a three position "perspective control". Does this also need to be recapped or can I just leave it alone in the middle position with no potential issues? Do you think this actually performed a worth while function or is it just an unneeded bell/whistle?

The main part of the crossover is behind the bass unit but a subsidiary PCB consisting of three resistors and two electrolytic capacitors is located behind the contour (wafer) switch between the speaker terminals.





This post or any other information supplied to this website or any other by myself is not available as sales and marketing material for sleezeBay or Audiodogging pimps and the like.

 

[RichmondMark]

Well so it appears that perhaps there was no modifications to the xovers for the tweeters. Looks like they hooked the new tweeters up to the leads for the old tweeter and then just wrapped up the super tweeter leads. Please let me know from the pics if you agree with that assessment (if you can).

However, somebody did alter the left xover (see pics). The crossovers are attached to the foam behind the woofer. The right one is still suck in its original position. The left one was pulled up and a portion of the foam ripped (still attached to the bottom of the xover). Looks like someone soldered in 2 33mf cap where the untouched xover has a a single 60mf cap.

The thing is...I don't see a 60mf cap on the xover schematic provided by MunkeyQ. So I'm not sure which speaker this is associated with.

So I'm guessing these should both be recapped. And I'm guessing they could go back to the original configuration easily if I can get the speakers.

Do you think the difference in the cap values (and one versus two) here could be the biggest contributing factor to the left speaker having weaker sound (maybe mid range...not sure) as I discussed in my other post?

 

[RichmondMark]

Alright guys...pardon the newbie with all the questions. Don't want to wear out my welcome. But here goes...

So if the two 33 mf caps were put in place as "C1" from the schematic provided by MunkeyQ, I guess they are functioning as part of a "high pass" between the woofer and the mid/highs. Is that right?

So if the values were different, C1 on xover 1 @ 66 mf would pass a differing frequency range than the C1 on xover 2 @ 60 mf? Does that make sense?

And if so, then the mid ranges might be supplied differing frequencies and this could be the difference I can notice?

Does that make any sense? There are different cross over points?

 

[RichmondMark]

I think I put you guys to sleep. I don't blame you.

Anyway...problem is solved. Switched out the caps in question and the speakers now sound identical.

Now I'll just have to sit tight until I can find the original tweeter/super tweeter...but you know...they sound pretty darn good as is. Must have been something when original.

thanks

 

[M Jarve]

Alright guys...pardon the newbie with all the questions. Don't want to wear out my welcome. But here goes...

So if the two 33 mf caps were put in place as "C1" from the schematic provided by MunkeyQ, I guess they are functioning as part of a "high pass" between the woofer and the mid/highs. Is that right?

Yes indeed.

So if the values were different, C1 on xover 1 @ 66 mf would pass a differing frequency range than the C1 on xover 2 @ 60 mf? Does that make sense?

And if so, then the mid ranges might be supplied differing frequencies and this could be the difference I can notice?

Does that make any sense? There are different cross over points?

'
Exactly. The speaker with the two series-wired caps would shift the crossover frequency down and mess up some other things. Though, it should be noted that 66µF is likely well within the tolerance of the original caps (sometimes spec'd as -10+20%!), and thus would not be huge. Noticeable, especially since the older, original cap has likely lowered in value over time, raising the x-over frequency.

And definitely track down a set of original tweeters and super tweeters if possible. One thing that might help with that is knowing that the both were used in a number of speakers, usually of British origin. A donor unit might be a B&W, for instance. Be thankful that the 80's weren't equipped with the really rare Coles unit that the 50's used.

 

[RichmondMark]

Interesting. Thanks for the info/confirmation Mike. It's something how big a difference a single component can make. I had my fingers crossed given the closeness in the rating (60 vs. 66). I suspect you are correct that the existing cap had lost some value over time and exaggerated the difference. It was pretty substantial.

I'm happy they are serviceable for now (actually pretty good) and that the rest of the crossover is intact so I can revert back easily...when I get replacements. This will be a good project.

 

[M Jarve]

Actually, now that I thought about it, the two 33µF caps in series like that would equate to a 16.5µF cap! Way, way off! In order for that arrangement to work, each cap would have to be 120µF.