1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

IMF owners thread!

Discussion in 'British Audio' started by canuckaudiog, Mar 18, 2013.

  1. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    Not sure if this question was directed at me or not. But, I did look for some TLS50 MkI crossover and see some similarities and also some differences. I have my crossover sketched out and just need to refine and double check it. Will post it when I have time to complete.
     

     

    Please register to disable this ad.

  2. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    Here's my drawings of the crossovers for my "The Studio's". I am told they are very early ones. On the T-15 tweeter the wires come out of the metal housing and if there were markings they're gone. I assumed the Black wire is the negative side. The wires from the crossover were spliced to the driver, so not sure if there was a change at some point. Also, I am not positive that the mid is an EMI driver. It has some kind of doping on the cone and an inverted surround that appears to be some kind of thin rubber or PVC?

    I'm still on the fence whether to restore these to original or make a bunch of improvements. Any input is appreciated either way.

    I have another thread I started in the speaker forum to document my re-build. But, I will keep coming back here for expert advice as it progresses.
    IMF Crossover schem.jpg IMF Crossover map.jpg
     
  3. petervv

    petervv Active Member

    Messages:
    107
    Location:
    Netherlands
    hi All,

    I walked into a pair of near mint Compact II's and couldn't resist for 45 euro (52 US $)
    Units are like new, wood has some minuscule marks but overall stunningly beautiful for speakers 40 years old!

    image5.jpeg image4.jpeg

    They look cute next to my RSPM's :)

    image2.jpeg image1.jpeg

    kind regards, Peter
     
  4. petervv

    petervv Active Member

    Messages:
    107
    Location:
    Netherlands
    hi Dogwan,
    I would restore them to original using the Falcon capacitor kit. Using better capacitors will change the voicing of the speaker, other improvements like moving the crossovers outside the box will ruin their value. As the inductors have iron cores they are much less sensitive to having other inductors close, I wouldn't bother.
    Whatever you change to the design, the units still are 40 years old, if you really want better sound quality, buy modern speakers, things really have improved since the 70's.
    Of course, this is just my opinion, your milage may vary.

    kind regards, Peter
     
  5. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    Yeah, that's the way I'm leaning. I think it would be the path of least resistance as far as causing headaches. I already have the capacitor kit from Falcon in hand. Yours is the 1st opinion that the inductors are fine where they are. I get that they may be better oriented a different way, but worry that I would ruin the voicing if they were tested and adjusted the way they are.
     
  6. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    185
    Location:
    Australia
    Hi Dogwan,

    I very much support what Peter has written. I to am a firm believer in non modification, rather only modify in the sense of maintenance of replacing failing components of the same values and specifications.

    I very much feel that the IMF brand has fallen into the category of "collectable" and as such the value in them is held by their originality. As soon as they are modified in a way that is "non retrobility" they basically become worthless. This is why many harder to find IMF drivers and parts command substantial prices when offered on sites like eBay etc.

    Peter,

    What a contrast in those two photos, you've basically got entry level sitting next to top level at the time of your RSPM's production.
    BTW, every time I see your speakers and Pioneer Spec gear it just makes me go ahhhhhh ! The effort you've put into your gear is a real credit to you.
     
    Last edited: Oct 26, 2018

     

    Please register to disable this ad.

  7. petervv

    petervv Active Member

    Messages:
    107
    Location:
    Netherlands
    thnx, I'm having great fun :)

    Like many of us I'm actually collecting the system I lusted over when I was 16/17 years old, I still have the actual Pioneer '77/'78 brochure from back then.
    I heard the RSPM's in a shop around that time as was immensely impressed but of course couldn't afford them so I buildt some DIY transmission line speakers with a Kef B200 and an Audax HD12x9 and even wound the coils for the crossover myself to save some money. Of course the sound didn't come close to the RSPM's :-(
    After acquiring the SPEC rack I thought I should have HPM150's because they match the rack system, I really tried to like them, recapped them, found orignal woofers, again tried to like them but did not succeed.
    After reading all information on the web about IMF it was clear I should buy the RSPM Mk4's as most people find this the 'best' version.
    I also learned both tweeters are fragile and a lot of them were killed over the years, so I had to find a pair with original and working tweeters.
    After about a year of searching I found a pair in good original condition in Germany, a deal was made, the HPM's were sold to finance the IMF's and the rest is history :)
    To my ears, the RSPM's sound so much better, they make me smile everytime I listen to them.

    have a nice weekend, Peter

    PS The Compact II's are in my SX-1250/PL-570 bedroom system and are very nice to listen to on easy sunday mornings :)
     
  8. lawrence001

    lawrence001 New Member

    Messages:
    6
    Location:
    London, UK
    Supposed to be collecting my first IMFs, TLS80s (first version) on Friday, very excited. Will have a good read through this thread when I have more time. Unfortunately one and possibly both B110s are scratchy on certain frequencies.
     
  9. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    185
    Location:
    Australia
    Congratulations Lawrence ! it's always a nice feeling getting into your first set of IMF's

    As far as the B110's are concerned, that's nothing that can't be easily solved as replacements are readily available and even if you have to go all the way, new upgraded ones are now able to be purchased directly from Falcon Acoustics in your neck of the woods.
     
  10. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    Hey, I need some help.

    The "Studio's" I bought had their stuffing replaced with dacron. I now have the cabinets completely gutted and about halfway to having the woodwork restored and ready for re-finishing. Crossovers have been re-capped. Probably should start developing a strategy for getting the stuffing back to as close to original as I can.

    Here's what I know:
    • There's evidence of fiberglass stapled to the sides behind the drivers. Not sure about the back behind the drivers.
    • There used to be dowels (side to side) behind the drivers holding something up against the back (covering the terminal plate?)
    • There are small dowels (front to back) if I reach down the throat into the transmission line. These dowels stop short of the back, meaning there's a gap that something could be slipped passed them.
    • In the exit throat there's also evidence of fiberglass, maybe stapled, maybe not.
    • In pictures I've seen it appears that at the exit there was some kind of jute like long fiber held in place by black cord stapled in a zig-zag pattern.
    Here's what I don't know:
    • Is it only fiberglass that was used on "The Studio"? Or, was it a combination of fiberglass and sheep's wool.
    • Was there anything stuffed in the mid section of the transmission line (the part I can't reach).
    • How thick was the fiberglass that was stapled behind the drivers?
    • What is the weird jute like fiber at the transmission line opening?
    Here's what I think based on what little information I could find and some other sources:
    • I should staple fiberglass to the sides behind the drivers.
    • The dowels behind the drivers should hold some tightly pack short hair sheeps wool.
    • The dowels down in the beginning of the transmission line are there to hold in place long haired sheeps wool.
    • I should place more loosely packed long hair sheeps wool behind the drivers
    • In the exit section of the line I should place a flat sheet of uncompressed fiberglass
    A couple other thoughts:
    • If there is supposed to be stuffing in the middle section I am going to have to cut an access panel in the front baffle so I can reach it. I have the skills and tools. But, it won't be stock anymore with a mending plate covering the access hole after stuffing it.
    • The front baffle of both the driver board and the line are well glued in place. There's no way they are coming out without severe damage.
    • I read an article that the ideal amount of Sheep's wool stuffing for a transmission line is roughly 0.5 - 0.7 lb's per cu.ft. I calculated internal volume of my speakers to approx. 2.95 cu. ft. internal dimensions. I have just about enough raw washed Sheep's wool to meet that formula.
    Any guidance is appreciated. I would rather not have to second guess whether I got it right. I am attaching a couple pics I found in my research. I wish the one from the IMF website had some labelling.

    studioicon.jpg

    response_Bailey-1965-Non-resonant-Loudspeaker-Enclosure-Design.jpg
     
  11. Yvan_donald

    Yvan_donald Well-Known Member

    Messages:
    706
    Location:
    Montreal,Quebec,Canada
    Hi, my Prof. Mk III have fiberglass inside,1 inch. Thick stapple on the wall and top near the woofer, back install diagonal with empty space at the top angle, being the woofer two long dowel from the side wall to couple of inch from the tube,these dowels are fill with four pcs.of fiberglass 1 inch not too compress square with two cut diagonal in front bottom and top back side. Try to get a camera (snake) to look inside the line, probably some stuffing is still there because too far to reach. I think the back previously have 1 inch. Fiberglass along the back wall, living the Dowell pin alone like your picture of first drawing, probably they have sheep wool at the bottom curve like my prof. Not too much,just let the air go.At the end your studio have fiberglass? or sheep wool.? not compress. My Prof. Or the later Tls have cardboard tube not plastic, for sure much better for the resonance in tube.best regards,Yvan.
     

     

    Please register to disable this ad.

  12. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    It just dawned on me that I could cut an access hole on the bottom to see what's in the middle section. That would be easy to screw a cover in place and have it completely hidden.

    I have used a mirror and from both the entrance and exit I cannot see any more stuffing poking out from the bends. But, that doesn't mean there isn't anything stuck in there.
     
  13. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    185
    Location:
    Australia
    Personally I wouldn't touch the inner chamber as nothing will have been changed from original manufacturing because no one can get to it in the first instance.
     
  14. Yvan_donald

    Yvan_donald Well-Known Member

    Messages:
    706
    Location:
    Montreal,Quebec,Canada
    Hi, I did an experience couple of year's ago, I glue a styrofoam (adjusted to the shape of the cone ,1 to 11/2 inch thick.,flat even with the rubber surround) on a extra woofer I have (SP 1014), I install it on my tls 50 mkI. the sound was okey but the baffle was ratleling, because the baffle have no support in the center like the tls 50 mkII or the Prof. serie or tls 80. But I did like the bass coming out, the woofer was more stiff with no distortion of the cone,like a flat piston.Maybe I should drill holes in the center on the lower section below the woofer and glue few dowels to make the baffle more rigid and retry the experience.
     
  15. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    I can't tell if someone might have removed the front baffle. I see nail heads around the perimeter and it's glued in place with a construction adhesive like glue. If someone did remove it they would have had easy access to the middle section.
     
  16. IMF_Pioneer

    IMF_Pioneer Active Member

    Messages:
    185
    Location:
    Australia
    I must admit in cases like this photos are a huge help and the more the better I always say.

    Cheers.
     

     

    Please register to disable this ad.

  17. Yvan_donald

    Yvan_donald Well-Known Member

    Messages:
    706
    Location:
    Montreal,Quebec,Canada
    Hi,even if you remove the front baffle,you can't have access to the middle section.They only way is from the bottom if you open a big square like the size of the wood base.I know because I bought a prof. MK III, and during shipping they broke one wheel and I have to completely remove the bottom base made of presswood laminate with black formica.only this way hyou could achieve what you try to accomplish.
     
  18. dogwan

    dogwan Dogwan

    Messages:
    1,195
    Location:
    Portland, OR
    @Yvan_donald, I used to be a professional cabinetmaker so if needed I have the skills and tools to perform surgery on either the front baffle or through the bottom to get to the middle section. I'm thinking the bottom is the best route to get a straight visual and easiest to repair. I can cut a rectangular hole inside the base and screw a cover plate back over the hole.


    @IMF_Pioneer

    Here's some pics.....
    These two are down the entrance to the TL. You can see there's nothing at the bottom. The material stuck to the dowels is dacron pillow stuffing. The dowels don't go all the way to the back and I could probably slide a sheet of fiberglass down the back if I tried really hard.
    20181110_120824.jpg 20181110_120801.jpg

    These two are looking up through the exit of the TL. Again, you can't see anything poking out.
    20181110_120834.jpg 20181110_120842.jpg

    Here you can see some of the staples that held the fiberglass behind the woofer and you can also see the holes for the 1/4" dowels (2).
    20181110_120915.jpg

    This one is through the woofer cutout looking at the back. You can see the entrance to the TL. You can also see the 3rd hole for a cross dowel.
    20181110_120922.jpg
     

Share This Page