IMF owners thread!
- Thread starter canuckaudiog
- Start date
Good advice. As long as speakers don't stress an amp, the combination that sounds best to yours ears is the right one.
Hello,
I'm trying to identify the value of a capacitor on the crossover board for a pair of IMF speakers, unfortunately the same cap has been replaced on both crossovers and I would like (if possible) to figure out the correct value.
I've attached images with the crossovers and to what I can see the cap values are 6uF, 7uF, 60uF, 100uF and for the one replaced on both boards, 47 uF (or 0.47 uF ??) but ideally I would want a confirmation on the correct value (I don't have a capacitance meter to test). Looking at the space available, I doubt it would have been anything close to 50uF (comparing with the other 60uF). I know ideally I should trace the components (that's the next step) or at least measure the existing caps but measuring would not give me the initial values.
These are unusual because they don't have tone corrections, so all schematics I found do not match.
The reason for the recap is that one of the tweeters (the one where the 7uF is obviously grown fat) sounds very faint and decided to replace all caps while we're there.
Any clues, ideas are much appreciated.
I'm trying to identify the value of a capacitor on the crossover board for a pair of IMF speakers, unfortunately the same cap has been replaced on both crossovers and I would like (if possible) to figure out the correct value.
I've attached images with the crossovers and to what I can see the cap values are 6uF, 7uF, 60uF, 100uF and for the one replaced on both boards, 47 uF (or 0.47 uF ??) but ideally I would want a confirmation on the correct value (I don't have a capacitance meter to test). Looking at the space available, I doubt it would have been anything close to 50uF (comparing with the other 60uF). I know ideally I should trace the components (that's the next step) or at least measure the existing caps but measuring would not give me the initial values.
These are unusual because they don't have tone corrections, so all schematics I found do not match.
The reason for the recap is that one of the tweeters (the one where the 7uF is obviously grown fat) sounds very faint and decided to replace all caps while we're there.
Any clues, ideas are much appreciated.
Yvan_donald
Well-Known Member
Hi and welcome to this forum, yes it's a .47 uf, my prof. MK III have the same and I think your's is the original cap, 250v is normal for this cap,best regards Yvan.
Yvan_donald
Well-Known Member
Hi, please can you post a photo of the back ,and sorry for this question but it seems your baffle have receive an open surgery around the woofer,what happen?
Someone tried _something_, I'm thinking to mount a different speaker instead of the B139 but (luckily) failed and reverted back. The damage is mostly cosmetic but there are some extra holes.
I've added a back picture, these are not strictly IMF (from looking at the label on the back) but very early (1972 from reading this: https://www.hifiwigwam.com/forum/to...rs-labeled-mdkt/?tab=comments#comment-2187151)
They still sound incredible, I don't think I've heard a drum beat sound so life-like in any other speaker.
Next step is to replace the caps.
I've added a back picture, these are not strictly IMF (from looking at the label on the back) but very early (1972 from reading this: https://www.hifiwigwam.com/forum/to...rs-labeled-mdkt/?tab=comments#comment-2187151)
They still sound incredible, I don't think I've heard a drum beat sound so life-like in any other speaker.
Next step is to replace the caps.
Yvan_donald
Well-Known Member
Hi, yes the B 139 with the styrofoam cone is for me have the most flat frequency response you can obtain from a woofer, absolutetly no coloration from it. That's why I love my Mk III so much,when you knock on the cone it sound dead, compare to other cone material.
Yvan_donald
Well-Known Member
Hi, you should apply wood putty filler on the surface around the woofer,sand with 100 grit sandpaper and spray with a flat black high temperature paint.But first masking tape all the components, put a foam gasket behind the woofer,install the woofer to is place,masking tape edge of suround and spray the baffle, is gonna look very clean. I did that on my MK III and they look great.
Yvan_donald
Well-Known Member
Hi and welcome to audiokarma,I own similar pro mk III and to answer your question is no, just flat,do you know if they are improved model,what was the value of each capacitor.Do your kits comprise a 100 uf,60uf,12uf,6uf and maybe 5 X2.2uf,and 1X .47uf?
Yvan_donald
Well-Known Member
Hi slofut, you know it is a very small difference between the normal and the improved model, in the past , page 32 here I have shown the difference between them ,the board himself almost identical but different.I will have to take a new picture of the 2 boards side by side. And at page 44, I have insulate the midranges tube (inside), this mod make a big difference, because at higher volume the bass enter the tube or vice versa mids go true the tube. Now with better insulated the mids is more clear.
I just picked up a pair of mystery IMF, I thought they were modified but then I found an identical pair in France:
http://www.hifi-antique.com/view_product.php?product=10757
They're not veneered, rather finished in a smooth grey laminate with casters on the bottom. They look similar to a TLS 80 but the cabinets are bigger (the size of an RSPM).
They're still in the car because it has been snowing (ugh) but once I get them in the house I'll open them up and see what's in them for a crossover. Might shed some light on what model they're closest to.
http://www.hifi-antique.com/view_product.php?product=10757
They're not veneered, rather finished in a smooth grey laminate with casters on the bottom. They look similar to a TLS 80 but the cabinets are bigger (the size of an RSPM).
They're still in the car because it has been snowing (ugh) but once I get them in the house I'll open them up and see what's in them for a crossover. Might shed some light on what model they're closest to.
Yvan_donald
Well-Known Member
Hi,this is a pair of Prof. Mk III improved with reference standard plate on it, these are with fiberglass insulation inside but IMF last production of Mk III was with foam insulation calling the same reference standard.Do IMF sell the plate or give the reference standard plate to any Improved model, if you ask them at the time? These are laminate grey color instead of wood laminate,like they have produce before if you ask them for a specific color.I have seen some pictures of IMF with the same color. I would like you to take some pictures of the crossover when you open them (from the woofer you have access). Do these IMF have the crossover done? Because after 45-50 years (1974-75) long time some electrolytics capacitors are out of spec. It's the first time I see a reference standard plate so close in a picture, the fabric is different from original, maybe have been change or not?
Yvan_donald
Well-Known Member
Hi, Slofut here 2 pictures of removed crossover improved, you see at the bottom left the improved model is different from the non-improved, page 32,you see a little wire doing a bridge right beside.
Yvan_donald
Well-Known Member
Hi, I just knowing I didn't put a complete picture of the non-improved model, i have to take a better one, but anyway if your crossover is not like thes new pictures I have take it means you have the non-improved one, but easy to modify, the holes seems to be at all the same place.
Yvan_donald
Well-Known Member
Hi Slofut, I have put the picture of the specific difference in page 32, further down in later post. Sorry long time ago.
This is the crossover in mine:
Here are a couple pictures of the actual speakers (like I said, pretty much identical to the ones in the link). At some point someone modified them for bi-amping by adding a couple pairs of speaker terminals, fortunately they didn't butcher the internal wiring so it will be easy enough to undo. I'll need to deal with the extra hole in the back once I remove the extra terminal cup, I'll probably plug it up and put a new piece of formica on the back (some day...).
Does anyone sell replacement super-tweeter covers? Both of mine are missing.
Here are a couple pictures of the actual speakers (like I said, pretty much identical to the ones in the link). At some point someone modified them for bi-amping by adding a couple pairs of speaker terminals, fortunately they didn't butcher the internal wiring so it will be easy enough to undo. I'll need to deal with the extra hole in the back once I remove the extra terminal cup, I'll probably plug it up and put a new piece of formica on the back (some day...).
Does anyone sell replacement super-tweeter covers? Both of mine are missing.
petervv
Active Member
Returned to my RSPM's after using the Magnepan 1.6's + sub for a while, for the occasion I treated them with some furniture oil, they still look perfect after all these years, they really are special speakers. I fell in love with them hearing them at a local dealer somewhere around 1978-1980, but of course, being 16-18 years old I didn't have the money to buy them, as documented in this thread, they came on my path a few years ago so I sold my HPM-150's and will live happily ever after 
Yvan_donald
Well-Known Member
Hi Ross, look for the improved crossover ,your's is not the improved one, it's exactly what my Mk III crossover before I received the improved one, look at the pictures in page 32 in this forum and page 104 to modify. Buy the Falcon kit for the improved model and you will have a big improvment. For the cover it's very hard to find , Falcon sell cover for the Ls3/5a not exactly the same as celestion but similar.I would like to try but I have to be sure the diameter of the dome is close to the celestion HF2000 and Ask Gerry for the exact dimension of is cover.
Yvan_donald
Well-Known Member
Peter VV, hi they really look super clean, nice pair. One of my friend just buy a pair and they sound wonderful, drive them with Naim products and they sing very well with is components, but he need more watts ,hard to drive so he just get an amp with more power.