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IMF owners thread!

Thank you Yvan. From what you say about adding the carbon pad inside the old tubes, I have a new idea:

- mid-speaker tube should remain the same size inside (diameter) and re-use the old foam packing material (assume that the original design is good)
- replace the 40yr old cardboard tubes with something more rigid like plastic or fiberglass or composite
- ensure the "new" tubes are strong & stiff so they do not introduce new resonance

Has anyone else tried this? I can only find reference to treating the original tubes to increase their stiffness, such as here: http://www.canuckaudiomart.com/forum/viewtopic.php?t=31450

My guess is: either play with the original cardboard tubes or replace them. Wish I could find more info about this as I don't want to ruin the original tubes.
 
Hi, I have read the canuck forum and only if the tube start to separate from the baffle, the use of glue putty,epoxy,silicone to fix it. The carboard is fine, the active carbon with all the mini cavities is the best to insulated the mids frequency to get in the bass line or the bass frequency to mix with the mids frequency + active carbon have the quality to add or made the tube bigger,so without diminishing is dimension. Active carbon is the best product for insulated or sound barrier by is thickness and now use by many sound engineers , only "lead" is better for thickness , but more expensive. The tube is very thin and for me Just put the googoo they talk about is not enough to really stop the frequency to come in or out, that's my opinion. Plastic or fiberglass when you knock on them make sound, really don't thing it's a good idea and almost impossible to remove the existing tube without destroying the speaker. Best regards,Yvan
 
Thank's Andy to agree, I have made couple of mods on my speaker and really believed I did improve the overall sound, without changing the original intend of IMF philosophy and achieve reference standard rendition of my music program , jazz,classical and other styles by listening mostly live shows. Search for perfection it is trial and error, but audio is great , and IMF was a head over many others, achieving their goal specially in the bass frequency , over 40 years ago, Yvan.
 
Hey Everyone,

I'm new here to this thread and the British Audio forum in general. I'm familiar with vintage Wharfedales, but this is my first pair of IMF's. I need some help!

I traded these IMF TLS 80's on Tuesday for my freshly restored/modified vintage DIY Bozak B302A's. The IMF's are not original. I was told the super tweeter had been disconnected and the original Celestion tweeters have been replaced with Hiquphon OWI tweeters. I plan on keeping the Hiquphons unless I can find affordable, and I mean affordable factory replacements.

It looks like the crossovers have been recapped with modern electrolytics. I have ordered Alcaps from Falcon Acoustics in the UK, they'll be here in another week or so. I see quite a few nasty iron core inductors, a huge one is screwed into the bracing down inside the cavity. I plan on replacing them all with air core inductors, that should really clean things up. I'll also probably end up replacing the resistors as well. But I'll test them first just to see.

I'm reading my way through this thread, it's a long one. Does anyone have a direct link to my crossover schematic? An image of my crossover is included below. I've found all kinds of schematics on the web, trying to nail down the correct on.

I haven't gone very deep into the innards yet, just enough to look at the crossover. The cardboard tube for the enclosure over the back of the midrange seems quite sturdy to me. I'll check later to make sure it's sealed/attached properly.

I have another question. I notice the front baffle has screws holding it into the cabinet. Does the front baffle come out free and breezy? Or am I opening up pandora's box? I would like to be able to remove the drivers and the baffle so it can be sanded and finished.

There are no sonic issues with these speakers, they sound absolutely wonderful. I would like to get a little more clarity out of the midrange though, but that's me being picky. They are amazing and they match what people are saying about them on the net. Here are a few images.


IMFTLS80-011.jpg


IMFTLS80-012.jpg


IMFTLS80-013.jpg


IMFTLS80-001.jpg


IMFTLS80-010.jpg


IMFTLS80-006.jpg


Biggles
 
Hi, welcome to the IMF thread, please don't try to pull out the baffle, because it's well glue and you will damage the inside cabinet, the mids tube is glue to the baffle, place in a groove, very Well fix, not like the Tls 50 serie or als 40 where it's more problematic. Someone have removed one of the original Iron core inductors on the x-over and install a different one On the foam. First you should change some wires,this new inductor have flimsy wire. The 5 X Red capacitors are they 2.2 uf value, the green one .47 uf, one 100 uf, 60 uf and 6.8uf, this x-over is a bit similar to my Prof Mk III except me I have a 12 uf and a 6 uf on mine. The tls 80 is very similar to my prof. Except the cabinet is smaller, so supposely give you more present bass frequency in the signal, TL labirinth is smaller, do the nessecity to isolate the mids tube.Is this à Mk I or Mk II model?
 
Yvan,

Thank you for taking the time to stop by. I looked through your crossover images on page 32, thank you! I now have the crossover schematic for the TLS 80.

Great news on the baffle, I'm glad I didn't dig into that. I'll leave it alone.

I don't believe I have the Mk II, it's the original I.

After looking at the TLS 80 crossover's components, I'm not impressed. I'd like to build my own crossover with air-core inductors, those ferrite-core inductors should be smashed with a hammer. It's going to take some time to get everything laid out well, but it doesn't look too difficult. Yay, a new project!

Biggles
 
Hi, Biggles don't be so negative on the inductors they make a excellent job in the IMF, sure probably you can improve with air core one, IIRC John Wright (IMF guru) have compare air core inductors vs the Iron core inductors and see no significative reason to use air core all the way? Why your's, original inductor have been change? To compensate for the new tweeter?. But you know the original celestion HF 1300 make an excellent job pair with the HF 2000 ,myself on my Prof. Mk III they really make excellent job to reproduce classical instruments in their natural tonal sound, I thing "Wilbur Aker" have a Tls 80 Mk I and probably can take some pictures of is X-OVER. Your mids if ever you checker should be kef Sp 1003 like my Mk III without the damping coating on the cone like I have on mine.
 
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
 
Hi, but do these ferrite inductors are they use for the lower frequency? And yes you have b110 sp 1003, and b 139 Sp 1044 in your speaker. But you know at the time they built these IMF , they always say , built with no compromise and not at a price, I'M not in Electronic field, but John Wright was one of the director (owner) with two other gentleman and always said Cost no object when making their speakers. For me the weakest link parts are the capacitors but it's just my opinion,and yes put I quality products help, I have spend over $1400.00 on capacitors and other mods, isolate mids tube,speakers binding posts and do not regret it, my MK III improved a lot,do changing the inductors will improved clarity without changing the voicing of the speaker?Best regards,, Yvan.
 
Hi Yvan,

Capacitors in crossovers are used to keep lower frequencies from getting to the drivers, you generally see them on the midrange and tweeter circuits. The inductors stop the driver from seeing higher frequencies, these are generally located on the woofer and sometimes on the midrange and tweeters. For example, you'd put an inductor on a midrange driver so it wouldn't go above 2500Hz, and a capacitor would filter frequencies below 400Hz. This way your midrange would only see frequencies from 400Hz to 2500Hz.

Ferrite core inductors are noisy and cause some sound artifacts when used in midrange and tweeter circuits. But they're so darned inexpensive when compared to their air core counterparts. John Wright passed away in 1999, so we can't ask him about why they used them. They do not have any magic in them, they're not special. They're inexpensive and can save you tons of money when your crossovers go into production. Don't quote me on this, but I believe ferrite core inductors aren't very picky about how they're placed on the crossover board. So, you can tuck more than a few tightly together on a crossover board and save space. Whereas the air core inductors need to be upright and 90 degrees from each other, while being at least 20cm from each other. They require relatively a lot of space so they don't magnetically couple with each other and cause problems with your crossover points moving all over the darned place. Replacing the inductors on these crossovers should greatly improve the imaging and voicing of the midrange drivers. They should really open up and deliver a far cleaner presentation.

My IMF's have already been messed with, they are not original. So, for me to go in and replace the inductors along with all the epoxy coated mylar capacitors isn't really an issue. I'm not messing with factory original IMF TLS 80's. Even if I was, I could put them back to original without much hassle.

I'm sure you've already read this TLS80 mod page, but down on #6 the author talks about installing just 1 tweeter instead of the factory tweeter/super tweeter combo. Tweeters have come along way in the last 20 to 30 years.

http://www.t-linespeakers.org/classics/TLS80/TLS80_mods.html
http://www.t-linespeakers.org/classics/TLS80/TLS80_mods.html
Biggles
 
Hi, yes Biggles I just finish listening the 8 and 9 Dvorak symphonies, wow I love classical musics, specially the Vienna orchestra at Musikverein hall ( for me the best recording come from this place), you know these musicians play on old instruments of the past time.with the Berlin orchestra they are probably for me the two best one, specially during the time of Karayan and Bernstein , you surely right on the ferrite inductor, if you put air core will you have to move them from where they are at the moment ,because of contrain space no, or it will be okey? Myself the way my prof sound with the celestion combo,it is hard for me to change to one tweeter, something magical with this HF 1300, and the tonal frequency of the HF 2000 is just perfection, you know the active carbon thing do I don't no what, but perfection+ I have open the back of the HF 1300 remove the foam and replace with the active carbon, before iI have some echo or distinct high tone coming out from the tweeter, now with my change no more of this. All IMF made are base on the learning experience of the prof. Mk III, John Wright pass so much time to perfection this model, so for me it is the ultimate model and I will keep the 4 same components, because 10 hz to .... very rare to achieve, I can feel all the nuance in the low frequency with amazing définition, no mâter what People say, the Kef b-139 with the styrofoam cone give a incomparable natural sound and with my preamp Audio research SP 6b with amp Bryston 3B St, everything is Well controle at any level, seriously l'M not kidding.Yvan.
 
Hi, you know Biggles I'M 60 years old, I am from the time when the Crown DC300A was use by almost all rock concerts ingeneers or technicians at the time.myself I was using two DC 300À in mono 600 watts each,don't have to tell you the IMF was well control but not so musical like with the Bryston 3B,I own three models of this Amp, and the ST is far more superior than the First two, this one have no flaws, it never clip and have a tremendous clarity and all frequency if he is combine with a good preamp.And 20 years waranty it is exceptionnel.The purpose of making the IMF TLS 80 was to reach for a different crowd of People more for rock music, so smaller cabinet so more punch for the bass, that what I heard,my friend of audio was telling me for this model (selling IMF). That is why these mods came out, more vibration in the baffle, and the mid tube isolation, the prof. Mk III have formica laminate as finish, not so nice ,but no resonance, bigger cabinet.For the mid tube you have to try the active carbon 1/2 inch, you will heard a big difference,,it is an excellent sound barrier without affecting the dimension.
 
Hi Yvan,

I'm only 52, so a little behind you in age. You are correct, a small cabinet will give more "punch", but limits the ability to dig deeper. I like large cabinets, 5 cubic feet is as small as I like to use. Since my IMF's were already messed with, I don't feel that I have to keep them original. I could buy the original tweeters and install them, but I don't really want to. The high quality replacements that were used sound absolutely wonderful. They have a pleasing tone to them, very open and clear, precise.

I've spent the last 2 days listening them off and on. I've been very busy with other audio projects, haven't had the time to spend all day at them. I'm finding that the midrange sounds subdued, not quite as detailed as I was hoping for. Let me make this clear, my midrange drivers are working fine. However, when I compare the midrange response to my Bozaks and my Stephens Trusonics, the detail and open airiness of the midrange isn't there. I've ordered the new capacitors and I'm going to replace those. I will test their response. Then I will figure out which inductors are for the midrange, and replace those if necessary.

Tell me more about using active carbon in the midrange tube. Is this the filter that we buy for our fish aquarium water filters?

Biggles
 
Hi Biggles if you look at page 44 , when I install the active carbon, it come in pad 10"X20"X 1/2". My tube have 4 pcs. Of fiberglass 2"X 18"-20" X 2" thick, dispose like a + or a × in the tube, but was not filling the complete perimeter, take it out and put the active carbon inside on the complete perimeter, cut a piece circle of 5 1/4" install at the end of the tube, so the complete tube is cover with the active carbon, cut the fiberglass in half in reinstall 5 pcs. 2"X 1" X 20". Now the tube is very well insulated from the T-line, and the mids from the t-line. The sound is à lot more distinct, heard little details who was not so obvious before. Great stuff this active carbon.
 
Yvan,

Thank you so much for taking the time to offer up that suggestion and the explanation. I read a little bit about using active carbon stuffing in speaker cabinets last night and will do more reading. Thank you!

Biggles
 
Hi, I have been thinking about what some Aker's in the fact of upgrading for new tweeter's, or one better tweeter replacing the original combo. All the 4 originals drivers Works at their optimum frequency with their inductors,limiting the range, we all know? the HF 1300 work to maximum + - 13000 hz and act as a midrange-tweeter, hf 2000 do the rest. By removing the HF 1300 from the quatuor you lose the frequency this tweeter usually do for the mids. Do two drivers have more impacts when the HF 1300 have 1 1/4" diaphragme surface, HF 2000 3/4" surface, compare to one new tweeter with 1" surface who gonna déliver from 3500hz to 20000hz and more. It's is not a small task to achieve a reference standard sound. In previous design Celestion use HF 1300 with 8" driver (Ditton 15),Spendor, B&W and act as a mid-tweeter limiting the high frequency to maybe 15000-16000hz and did a good job. New tweeter do higher frequency today but can they do lower frequency too? Best regards,Yvan.
 
Hey Yvan,

The choices available for modern tweeters is huge. And the prices range from 30 dollars to thousands of dollars to go up and over 30,000Hz. The precision, detail, performance versus 30 to 40 year old tweeters is even larger. I called Madisound.com today to talk about some tweeter solutions I would like to have for a Bozak project I'm just finishing up. There are tweeters made with Beryllium that are supposed to be absolutely amazing. But paying over a thousand dollars for a pair of tweeters isn't going to happen, for me.

The Hiquphon OWI tweeters (nearly $300 dollars delivered) in the IMF's can be crossed over at 2500Hz and are supposed to be able to go up to 28,000Hz. They're made in Denmark by Oskar Wroending, a exceptional product. No modification to the IMF network was done, they were a drop in replacements.

I'm using a new pair of SEAS Excel T25CF-001 in my 50 year old Bozak Symphony speakers to replace the original arrays of 8 B200Y tweeters in each cabinet. The SEAS tweeter can be used down to 2000Hz and goes up to 25,000Hz. But I've crossed it over at 2500 to come down to match the B800A midrange in the Bozaks.

I love vintage speakers, most of mine are 50 years old or more. The weak spots are the tweeters and the crossover design. The results I get from updating both the crossovers and tweeters is astounding and worth all the time, effort and money I've put into them. I will never go back to original crossovers and tweeters, we can do far better.

Biggles
 
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