I am wondering if this thread is still active? I have been playing with mdkt for a few days, I know now that the crossovers are wired improperly. I am trying to figure out the secret code between postive and negative on the connections at the crossover. I have sent several pics to Jerry at Falcon and waiting a reply. For sure the 139 are wired out of phase but I am not sure which terminal on which crossover is - or +. I have searched and googled many sites. On my crossovers from the top down I have on the connection side from the top down, LG, LF, IP, MD, MR, LC-M, (can't read the next pad, then TR, TW, STW, STR, NG. Several connections are wrong between the left and the right speakers, but I am just not sure which speaker and crossover is correct. Any help is appreciated, I really want to hear these shine....now that I found out the issues. THX!!!
IMF owners thread!
- Thread starter canuckaudiog
- Start date
Are both speakers equal in sound quality?
Other than swapping the speaker cables from positive to negatives to test polarity, I would err on the side of caution and wait for the recap kit to come in — always best to keep the number variables in the test as low as possible!
Failed/out of spec caps is the most likely cause of weirdness, being wired wrong from the factory is unlikely.
Do the speakers look like someone else had been modifying them?
Other than swapping the speaker cables from positive to negatives to test polarity, I would err on the side of caution and wait for the recap kit to come in — always best to keep the number variables in the test as low as possible!
Failed/out of spec caps is the most likely cause of weirdness, being wired wrong from the factory is unlikely.
Do the speakers look like someone else had been modifying them?
Yvan_donald
Well-Known Member
Hi, please rodercot can you show us the other side of your crossover and I will compare with my prof mk III, should be not far from mine for the circuitery pattern. Look at page 32 , you will have some pictures of my crossover, Yvan.
Thanks, I am attaching the pic of the track side of the crossover. This is the right speaker. ON the left speakers crossover, they had the purple and white reversed for the woofer, and they had the ST soldered on to the tweeters pad. I fixed both of those and the speaker sound a whole lot better. I just wish we could find a proper schematic for these pre-imf models. On page 104 you were chatting with a user named Kat, and he had posted some pics of his crossover, but the did not look to have the same components as mine do.
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Both speakers measure 8.5 ohms at the input terminals. Yes these speakers have been mucked around with over the years, not sure the actual components were ever touched on the crossovers. On the left speaker the woofer was wired backwards, and a couple other wires on the wrong pads when compared to the right speaker. I know they are better now as I actually have bottom end the left speaker is no longer dominant. Now I am just waiting to hear back from Jerry. Is there any reason we cannot just use the Falcon pre-made crossovers that are setup for this driver arrangement? I would also like to find out if there was a spec for the amount of damping that would have been used as I know mine are pretty hollow behind the drivers, and it is just pink insulation.
Yes, I agree. I was asking more because there looks to be a large void in the cabinet behind the drivers pretty much to the input terminals, which has me questioning if the damping is correct. It is the pink insulation.
those might be Mullard capacitors... but you might need to remove one to see if there's more information printed on the side(s) you can't see easily
found this forum post that refers to "Apparently "8017B" (which is marked on some of the 680nF250V yellow "chicklet" types found in some old Marshalls) indicates a post office spec."
http://forum.marstran.com/viewtopic.php?f=18&t=467
but I'm not seeing photos that are identical
closest similar I've found is
https://richelectronics.co.uk/product/mullard-polyester-axial-capacitor-1uf-250vdc-mbd017g
found this forum post that refers to "Apparently "8017B" (which is marked on some of the 680nF250V yellow "chicklet" types found in some old Marshalls) indicates a post office spec."
http://forum.marstran.com/viewtopic.php?f=18&t=467
but I'm not seeing photos that are identical
closest similar I've found is
https://richelectronics.co.uk/product/mullard-polyester-axial-capacitor-1uf-250vdc-mbd017g
Question pertaining to IMF CM3 insulation, specifically in the upper midrange and tweeter section. The set of CM3'S that I have came with Polyfill in the upper chamber, wondering if this is as original or added later. The woofer section of course is nicely lined with foam rubber and was rubber cemented in place, I know this because the original foam was removed on one side of each cabinet to put in an off the shelf Dayton xover, then the foam rubber was just tucked back in place over the xover's. The residue from the glue clearly apparent on the foam and the inside of the cabinet.
There is no glue residue on the wood in the upper chamber so I have to assume that there was never any foam lining there. It seems odd that they would use Polyfill there instead of foam lining as they did for the woofer section. Anyone out there know if there was originally Polyfill of other damping material in the upper midrange and tweeter section of the CM3 cabinets?
There is no glue residue on the wood in the upper chamber so I have to assume that there was never any foam lining there. It seems odd that they would use Polyfill there instead of foam lining as they did for the woofer section. Anyone out there know if there was originally Polyfill of other damping material in the upper midrange and tweeter section of the CM3 cabinets?
no personal experience, but does this photo match yours?
looks like the board is on top of multi-colored recycled foam rubber/carpet underlayment
then the white poly fill or foam rubber?
https://www.stereonet.com/forums/topic/99842-imf-cm-3-new-old-speakers-from-garage-sale/
looks like the board is on top of multi-colored recycled foam rubber/carpet underlayment
then the white poly fill or foam rubber?
https://www.stereonet.com/forums/topic/99842-imf-cm-3-new-old-speakers-from-garage-sale/
no personal experience, but does this photo match yours?
looks like the board is on top of multi-colored recycled foam rubber/carpet underlayment
then the white poly fill or foam rubber?
https://www.stereonet.com/forums/topic/99842-imf-cm-3-new-old-speakers-from-garage-sale/
Here's a photo of mine without the xover, also a photo without the foam rubber lining. Assuming those brackets are for mounting the xover's?
What a difference 48 hours makes, I now have in my speaker collection a pair of TLS80's and a set of RSPM Mark IV with stands. The 80's sound mind blowing and no comparasion at all to the pre-imf speakers I have been working on. The 80's cabinets are smaller than the Pre-IMF cabinets. I am going to measure both sets the 80's and the pre-imf. and if internally they measure up, I am thinking I could restore the pre-imf and turn them them into 80's. I setup the rspm's first but they just did not sound right in my room, I do not think I am getting much response if any from the filter tilt or slope pots, got some static initially when I turned them. So I will remove the crossovers and inspect, clean the pots and I guess I will be ordering a few sets of caps from Falcon... To be continued.... will post pics later have to run to a meeting this morning.
Congrats!
The TLS80’s in good working condition are an especially excellent find, both for their own sake and as a yardstick for comparing the ones that need repairs.
so obviously you need to get all three sets operating correctly so you can use them for an overkill home theater system!
The TLS80’s in good working condition are an especially excellent find, both for their own sake and as a yardstick for comparing the ones that need repairs.
so obviously you need to get all three sets operating correctly so you can use them for an overkill home theater system!
I agree about the metal clips potentially rattling, think I won't be mounting to those. At least not directly.
Have you had the midrange section of the cabinet open? Someone on one of the many threads I've been on trying to get information on these speakers said that there should be foam lining in the top part of the cabinet too, however there is no glue residue to indicate that there ever was any to begin with. When I opened mine there was however some Polyfill in each midrange part of the cabinets, curious if that's supposed to be there?
Thanks but the CM3'S are a completely different arrangement. This is the midrange and tweeter section of the cabinet
Slofut, you posted a some crossover pics back on page 104, can you please let me know which wire went to which pad and what was positive and which was negative, I am trying to figure out the crossover wiring for the drivers for my pre-imf mdkt models and those crossovers you posted look very similar to mine other than I have a couple jumper wires soldered on my boards. I posted pics of both sides of my crossovers a few posts ago. Thanks, Dave