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IMF owners thread!

Hi, Biggles I will never argue on the fact better tweeter's are made today, like better drivers too. Me I want the sound like if I was sitting normally in a concert hall let say in Vienna with all the warm tone and impact the orchestra can give me, no more no less. With the IMF like they are, nothing is harsh, instruments are sounding like they should, large wall of music, when oscar peterson play piano and I hear huming the music an his mout or other piano player who seems to do the same, distinct all the 4 voices in the Bethoven 9 th symphony and listening 100 of women and men singing and believed they are with me,that's what I have. Harp sound like Harp, triangle with nice high subtil tone, the big Drum impact and tympany sound precise and feel the skin of the instrument, 4-5 trompette when they blow in it have the impact , nice tone in piano note or clavecin, hear and feel the big dong in pictures of exibition classical, xylophone with is distinct sound, organ music in the back with the orchestra. I do not touch any drivers in my speakers because that's the way John Wright design it and that's the way I like. But in your case the TLS 80 was crimple, so du for improvment, and if are sure of yourself go for it, askink myself,are you in Electronic field?
 
Yvan,

Nope, no electronics in my background. I spent 26 years as The Computer Guy, that's where I made my mark. For the last 6 years I've been meandering, looking for work here and there. I'm so very tired of computers, no interest whatsoever.

I'm hoping the fresh capacitors that are on their way will improve my frequency response. My midrange frequencies are dull and lifeless. Lows and highs are just fine, as they should be.

My Bozak B302A's delivered the experience that you describe. But it took a lot of work on my part to get them there, they were not stock.

Biggles
 
Exactly. Once the caps arrive, I can dig out the crossover again. I need to follow the traces, work out which inductors and caps go to which drivers and then make sure all the components are within spec and working as they should. I do have the schematic and the back of the crossover board included. But once I have the crossover in my hands, it'll all make a lot more sense. I also will check all the connections to the drivers and crossover. Everything needs to be inspected very closely. I'm also considering re-wring everything, but that's for later. One thing at a time, then test.

Biggles
 
Hi, Biggles if you look at page 55 you can see my x-over, probably one Day I gonna install it outboard, because the caps are one of top of each others+ I never change the 100 uf ,but will do it soon this coming year.
 
Oh man, I would change that cap pronto. Those old El Caps were lousy when they were new. I've had those caps in many previous speakers, horrible little buggers. I changed mine the other day and the midrange finally opened up, it was really veiled. And mine had been previously replaced with generic electrolytics.

Unless you're going to be swapping drivers, changing crossover points and generally running experiments on your speakers, I wouldn't bother with externally mounting your crossovers. I'll probably be doing that on my next Bozak build. But that's because I build multiple crossovers and have to change them out from time to time. I've been building crossovers for friends and having them mounted externally means I can test my work without having to open up the speaker cabinets.

Biggles
 
Hi,yes it is a good point to have it outside to make the mods,when you need to. Mine Ii did not reglue the X-OVER is very easy to access
 
Hi, you see for the 60 uf I have use 2×30 plus a janzten .22uf that I have, I install the .22 on the x-over it has silver lead, in Connecticut the 2 x 30 in parallèle. First I did the contrary by installing one 30 uf, in connections the 2 others one ,did like the sound, but after the change silver lead have better conductivité so better transient.
 
Well I replaced the Tweeter in my New to me CM 2's but now go. So I had to open them up to see what the issue is.........

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So how to I go about taking out the cross over. Looks like glue but there are also two plastic ties as well.

It is tight quarters in there so I can not get a blade to cut it out of the "carpet pad" it is glued to.
The cross over is set at the bottom of the speaker where the black acoustic foam is. can it be accessed from that side maybe?

Edit: the ties hold them in !!!

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Nashou
 
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Hi Athanasios, well the alcap cap blow, this is un usually, maybe have been drive to high volume. That's is the way IMF was installing the X over with Tie-rap, no more glue,easy to work.
 
drbiggles said:
Hey Yvan,

Ferrite core inductors are okay to use at 150Hz and lower, and affordable. However, they have issues with saturation at higher frequencies which result in muddiness in your midrange frequencies. I'm sure it wasn't the engineer that wanted to use them, it was the people in charge of the money that forced the engineers to use them. I've heard crossovers that originally came with ferrite core inductors, they were poor, confused and muddy. I completely rebuilt the entire crossover using modern components and the results were absolutely stunning. The owners had wanted to sell their speakers, but after the crossover upgrade, they decided to keep the speakers and found them some of the top performers that they'd had in years.

My intention was not to be negative or talk badly about the designers and engineers of the IMF's. What they did with what they had was absolutely amazing and they've lasted all these years. But I'm just one guy restoring one pair of speakers, I can afford the time and money to use higher quality components. If I had to make thousands of these speakers from scratch, I probably would have used ferrite core inductors as well.

I have the KEF B130 Woofer, B110 midrange, Celestion HF2000 super tweeter and was supposed to have the Celestion HF-1300 tweeters.

Biggles
Click to expand...

Hey Biggles,

Welcome to the land of the IMFs!

Although yours aren't original, those tweeters are pretty nice. I can see why they did what they did, that is, disconnecting the two tweeters and using one. Really, that's what should have been done in the 70s but no tweeter was capable of reproducing that full range in one tweeter. So long as the modification was done properly I think it will work well. If possible, I would try to get frequency response measurements so you can see if there is anything funny going on there at the hand-off point between the mid and tweeter.

Regarding the inductors, I asked Jerry Bloomfield about this a while back because I had the same line of thought - why use these cheap inductors and not use air core? His response was that, yes, they are not ideal, but they do form part of the sound of the speaker and contribute to its voicing. You could of course go with air core but I feel like it's one thing you could probably skip. They sound gorgeous with those inductors and the air cores might certainly improve the sound, but would be rather expensive and as they are already modified, I'm not sure further modifying them would really be worth it. That's just my two cents on the matter.

Congrats on the find, for some reason I feel like I've seen those IMFs before with that modification. I'm almost positive I have.. but, can't recall where. Either way, that's good they sound great.
 
Hey man!

It's good to see you, where you been? Tweeters have come such a long way in the last 30+ years and I don't regret not having the originals. Well, okay I do have one regret. I regret that potential buyers don't feel the same way. I traded them for my vintage DIY Bozak B302A's so I could sell them. I was hoping that I'd keep and enjoy them. So far, I just can't warm up to the buggers. I've swapped them out for a pair of Bozak B-301 Tempos I picked up about 3 or 4 weeks ago. They're the low end, bookshelf sized Bozaks. However, they are delivering the character that I so desperately was looking for. They don't dig very deep, down to 40Hz. But damned if they don't make all the hairs stand up, get a little choked up listening. THAT's what I'm looking for.

I understand what the engineers say about why ferrite-core inductors were used, I get it. But I'm not buying it. If your solution to voice a speaker causes you to add sub standard components into the network, you're doing it wrong. There are other ways to handle spitty/shrieky/peaky responses to tweeter performance. For years I simply added a vintage oil cap. But all that does is add second order harmonics, a certain flavor of distortion. It adds ESR, causing the amplifier to work harder to push the goodies into the tweeters. You can either design a Zobel network, or if you've done the testing, you can build a trap for the specific frequency that the tweeter peaks. And I'm sure there are other ways to tame a tweeter with some real finesse.

When I recapped them with Alcaps, I was able to figure out that the L1 inductor was removed in the conversion. This way the replacement tweeter was able to be hooked into the original network and the lack of that inductor allowed it to go all the way up. With the new caps, the replacement tweeter is exceptionally smooth, lush and precise. They're a real pleasure to listen to. I'm also quite pleased that the L1 inductor was a ferrite-core rig and it's now gone. They are a far better speaker than they once were. But they're sitting in a corner now, face to the wall.

I know the guy that had them upgraded, and he doesn't post anything on the internet. So, I can say with authority that these specific speakers never got published. But that doesn't mean he didn't get the idea from someone else on the net, that could very well be.

It's good to have you back here and hope all is well up there. It's really wet down here, no disasters, yet.

Biggles
 
drbiggles said:
Hey man!

It's good to see you, where you been? Tweeters have come such a long way in the last 30+ years and I don't regret not having the originals. Well, okay I do have one regret. I regret that potential buyers don't feel the same way. I traded them for my vintage DIY Bozak B302A's so I could sell them. I was hoping that I'd keep and enjoy them. So far, I just can't warm up to the buggers. I've swapped them out for a pair of Bozak B-301 Tempos I picked up about 3 or 4 weeks ago. They're the low end, bookshelf sized Bozaks. However, they are delivering the character that I so desperately was looking for. They don't dig very deep, down to 40Hz. But damned if they don't make all the hairs stand up, get a little choked up listening. THAT's what I'm looking for.

I understand what the engineers say about why ferrite-core inductors were used, I get it. But I'm not buying it. If your solution to voice a speaker causes you to add sub standard components into the network, you're doing it wrong. There are other ways to handle spitty/shrieky/peaky responses to tweeter performance. For years I simply added a vintage oil cap. But all that does is add second order harmonics, a certain flavor of distortion. It adds ESR, causing the amplifier to work harder to push the goodies into the tweeters. You can either design a Zobel network, or if you've done the testing, you can build a trap for the specific frequency that the tweeter peaks. And I'm sure there are other ways to tame a tweeter with some real finesse.

When I recapped them with Alcaps, I was able to figure out that the L1 inductor was removed in the conversion. This way the replacement tweeter was able to be hooked into the original network and the lack of that inductor allowed it to go all the way up. With the new caps, the replacement tweeter is exceptionally smooth, lush and precise. They're a real pleasure to listen to. I'm also quite pleased that the L1 inductor was a ferrite-core rig and it's now gone. They are a far better speaker than they once were. But they're sitting in a corner now, face to the wall.

I know the guy that had them upgraded, and he doesn't post anything on the internet. So, I can say with authority that these specific speakers never got published. But that doesn't mean he didn't get the idea from someone else on the net, that could very well be.

It's good to have you back here and hope all is well up there. It's really wet down here, no disasters, yet.

Biggles
Click to expand...

I've sort of been around, but haven't checked AK in weeks. Maybe months? The audio hobby took a bit of a hit because of Christmas time and also interests in other things. Heck I can't even remember the last time I looked at the classifieds once a day, haha. I still listen to music on pretty much a daily basis though! Just nothing to do with any restoration work or hunting new gear. I'm pretty happy with what I have so I haven't been compelled to really look for anything, except I did pick up a pair of Celestion SL6's yesterday (mostly because I want a nice bookshelf speaker in the house). That's rekindled my interest in this hobby a bit since now I need to get them recapped and they sound pretty darned good. That and I need to get a move on with my Wharfedales, the Airedales other tweeter is now buzzing, but I'm pretty sure I can fix it.

So you went with Alcaps, good man! They're good electrolytics, and have the right ESR properties to replicate the original sound. Which, in the case of IMFs, isn't hugely important because the crossovers aren't very complicated, but you at least want good quality electrolytics. Either way, with parts that are almost exactly like the originals, there's not much reason to go with something else save for cost or availability. I'm not too surprised the refurb went off without a hitch, since now you are, more or less, hearing them as they were originally designed. It sounds like you're on the right path. It sure would be interesting to compare an original set to those, since I think the changes were solid improvements. The only question would be the balance of the speaker and if the crossover point shifted considerably because of the new tweeter, and whether or not that was compensated for in the crossover.

Either way, cool beans - I think you can now understand why people like this brand of speaker so much. They're a special vintage speaker, one of the best from the 70s. Not cheap, either, as the TLS 80 was around $1500 new in the mid 70s. But once you hear that bass, you likely will not hear better quality bass from another speaker. The freedom from the boxiness sound that a lot of speakers exhibit, especially from that time period, is really something else. You can of course find high quality bass elsewhere but the transmission line bass is unique.
 
I understand the dormancy, kinda been there myself over the last year. I haven't posted any of my Bozak projects. But I still poke around here on AK and goof off. I've met too many people locally and online to let the hobby slip. They keep contacting me with shiny objects, speakers I just have to have or whatever.

I'm in agreement with the online reviews with these the TLS 80's a full 100%. Good lord, what they can do with a good source is nothing short of amazing. It's just not what I'm looking for these days, I want more character. While the crossover isn't really all that complicated, it's no first order crossover. The drivers don't overlap each other and I think that's what killing their character for me.

The tweeter replacement was a drop in, no crossover changes were necessary. There were 2 audio/electrical engineers who did this, it was not something someone just did on a whim. They were even physical drop ins as well, no cutting was done to the baffle. Care, thought and talent were used to get this project completed. And at 240+ dollars or more, it wasn't a cheap job either. Thankfully, they don't take up a lot of real estate. They can sit in the dining room until they sell, or I can just move them out into the garage and deal with them later.

Biggles
 
If one were to replace the iron core inductors with air core the entire crossover would have to be redesigned.
The added Re with the air core inductors would cause this to be this case.
 
Hey Jim,

Which might be fun to do, see what would come of it. And then make them available to IMF TLS 80 owners. But at this point, it's moot. Hopefully soon my pair will be going to live in a new home.

Biggles
 
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