ML-1C Recap Experience

[Refugee]

I finally got around to recapping the ML-1C speakers. Here is how the experience went for me. I rebuilt the crossover of one speaker and put my family through some blind tests by sending a mono signal through one speaker and then another. They all said the rebuilt speaker sounded better. As for my impression – the speakers were slightly veiled before the recap. They sounded better to me after the work. It was not a drastic change. I really enjoyed the sound of the speakers to begin with and worried that I would loose the character of the speakers, but this was not the case. Just a little more detail and clarity. Well worth it!

I used the service manual to get a parts list together.

I ordered the caps, resistors, and caulk from Parts express (no affiliation). Cap and resistor choices are personal – this is just a guide and a timesaver.

All the resistors were of this type (only one value included in link) except one value that was not available for which I subbed in a more generic wire wound I had in stock.
Dayton Audio DPR10-6.0 6 Ohm 10 Watt Precision 1% Audio Grade Resistor

The speakers must be airtight when they are reassembled and this calk worked well.
Parts Express 12" Speaker Sealing Caulk Box of 72 Pcs.

For the parallel cap I ordered this bi-polar cap
150uF 100V Electrolytic Non-Polarized Crossover Capacitor

The rest of the caps needed were of this type. (only one value included in link)
Dayton Audio PMPC-1.0 1.0uF 250V Precision Audio Capacitor

The speakers were laid on their back using two short boards underneath to avoid putting pressure on the banana jacks. Remove the 12” woofer and unplug the wires from it.

Remove the fiberglass (use gloves) and set it aside in a way that makes it easy to put it back in the same orientation when you finish. Remove the wires and screws holding the crossover and then bring it to your soldering area.

There are some differences between older and newer iterations of these classic speakers. If you do not have the newest version of the crossover. It is recommended that you update to the final version. Very early versions had only four coils – recommended that you find a coil to update. Some of the resistors also changed value. The schematic and layout included here are the final version that should be followed. R6 on my speakers was the 64Ohm 5W from note #4. That was the only older revision in my crossovers. I replaced with the 56Ohm 10W from the final revision.

Solder in the new parts. Glue down the caps and resistors. I put toothpics under the resistors and glued them to the main plate and the resistors to the toothpics so there would be some room for airflow around the resistors. Use the caulk to seal the 12” speaker and the crossover – it must be air tight.


I have included pictures as I wished I could find some before I opened my speakers. I like to know what to expect before I start. Hopefully this post helps the next guy. Pretty cool that the date was stamped onto the crossover! OCT 18 1971.

Oh yeah –​

I used E6000 Craft Industrial Strength Clear All Purpose Adhesive to glue down the components. This was suggested on several crossover posts here on AK and it really worked well. It stays 'rubbery' which I think adds some vibration protection.
I also took time to use contact cleaner on all the wire connectors and posts, and took pains to clean off all the flux.

The speakers should be good for another 50+ years.

 

[eiraved]

Thanks for sharing your experience! I once owned a pair of ML-1C speakers and loved them, never performed a recap though but I did replace the woofer surrounds.

 

[motorstereo]

Nice write up and kudos for the nice neat job on the crossovers. I also recapped mine and like you I did one and then compared it to the other original. My bud stopped over and we both agreed it was a huge improvement. Another bonus I found I was able to back off the settings on my mq101. Pre recap the 101 was essential. After the recap not so much and I would often bypass the 101. I found a slight bass boost with the c28 was all that was needed as the mids and highs were so much better. Problem was I had 2 pair of ml1c's at the time and comparing a freshly recapped pair to the originals was even a bigger difference. By the 4th ml I was getting pretty good at reworking those crossovers.
I wonder if you have any busted grille clips? Most of mine were snapped off so I used magnetic cabinet latches to fix those issues during the recap. All 4 of mine are gone now but they were fun speakers while they were here.

 

[Refugee]

I wonder if you have any busted grille clips? Most of mine were snapped off so I used magnetic cabinet latches to fix those issues during the recap. All 4 of mine are gone now but they were fun speakers while they were here.

One of the grille clips was busted when I got them. I reinforced it with some plastic and glue and it is holding up ok so far. I was lucky that they were in such decent shape. The speakers looked really bad when I got them. They seemed to have a garage life and double as drink holders. All sides were terrible. I refinished the outside of the speaker boxes - the grills were in good shape and the speakers did not need a re-cone. Here are some before and after. Did the bottoms first - sides next - tops last.

 

[twiiii]

If I have recapped and installed resistors in ML-1C once I have done it over 100 times. Normally I had to replace the orange dome and tweeter too because people had fried the speakers with 2105's or 2100's. Boy was I glad when the MC 502 came along with Power Guard. The tube amps didn't cause me any head aches at all driving ML series speakers. A 2105 could even destroy ML-2 drivers. Poor ML 10's didn't have a chance. But back in the 90's and early 80's having to refoam the woofers and the later mids became just as much of a problem. With all that you would think I didn't like ML-1's. But when powered correctly and use as a book shelf speaker I thought they were best. A B&O 5700 had much fewer problems only needing a new tweeter diaphragm 90% of the time and sounded great. But when it came to bass below 50 HZ nothing could match an ML-1C until the XR-5 came along.

Caps will definitely will help today. Now if you want to increase the dynamic ability of a ML1 above 40 HZ Roger Russel designed an update replacing the orange dome and tweeter with Morel drivers. Audio Classics has all the info. Just ask for Ryan or Steve.

I had a friend that stacked two pairs of ML-1's on top of each other with the top unit inverted vertically on his fire place harth . He powered them with a MC 7200 and used a MQ 107 EQ. No issues there either. Others would stack them 2 or 3 units high horizontally using amps with Power Guard. ML_1's were sought out by folks knowing their full potential after they had been discontinued for quite a few years.

 

[Refugee]

Normally I had to replace the orange dome and tweeter too because people had fried the speakers with 2105's or 2100's.

Luckily the mids were fine when I got these. Replacing R6, the original 64 Ohm resistor with the 56 Ohm across the mid dome as per the latest crossover specs will help a small bit in protecting the mid dome. I am always on the lookout for a pair of working original domes to reserve as a replacement.

I could definitely kill them with the 2105 if I overdrove the amp or ran it right under distortion levels for too long but luckily the 2105 has meters that allow me to monitor the output and avoid this abuse. I was also sure to educate my kids on the top safe levels, and so far they have not damaged anything.

Now if you want to increase the dynamic ability of a ML1 above 40 HZ Roger Russel designed an update replacing the orange dome and tweeter with Morel drivers. Audio Classics has all the info. Just ask for Ryan or Steve.

I have also considered getting (and probably should) the morels while they are available in case the worst happens. Thanks for bringing this up. I will at least price out the upgrade parts with Audio Classics.

But when it came to bass below 50 HZ nothing could match an ML-1C until the XR-5 came along.

I've never had a pair of XR-5 but I do enjoy the deep bass of the ML-1C especially since I got the MQ-101. Another pair of 1C's would be great or maybe 2-C.
I upgrade slowly....it's my no debt for audio policy.

 

[eiraved]

Still haven't listened to my XR-7's, been too lazy to replace the trashed surrounds. I'll get around to it one day...

 

[Refugee]

Still haven't listened to my XR-7's, been too lazy to replace the trashed surrounds. I'll get around to it one day...View attachment 3425100

I have kept an eye out for some XR-7's for a few years now. They have long been on my wanted list. I'll bet they really satisfy once you get around to the refurb.

 

[tuffstuff1]

I bought a recap kit for my ML-1C and the kit fell one cap short of what my crossover consists of. There is a 25UF cap that goes across C3 and C2 referencing the schematic above. All of the schematics I have seen online are built like the schematic consisting of four capacitors. Would someone know what the 5th capacitor is for and is it even needed?

 

[Refugee]

@tuffstuff1
If you have the original drivers in the speaker then I would replace that cap with a jumper to match the schematic. If the drivers have been changed then there may be a reason for the added cap. Do you have five coils?
(EDIT)
Probably, the cap is an implementation of the highlighted note on the schematics note page. Is the original C2 cap also a 25UF cap? This could be the reason. (2 - 25UF caps in series equals a 12.5UF cap.)
If you got a 12UF cap for C2 in your kit then you would not need the 25UF cap in series. (Replace with a jumper)
See the schematics notes below from the Service Information Manual:

 

[tuffstuff1]

Perfect! See my question about LI coil wire relocation? I think I need to move one of the leads to C2. Does it matter which lead from the coil gets moved if need be?

 

[Refugee]

@tuffstuff1
The jumper between C3 and C2 is sufficient as it will attach the coil to both points electrically. If you move the coil wire to C2 with the jumper in place you have only attached the coil to the other side of the jumper - the electrical connection is the same. If you want to more closely match the drawing from McIntosh to avoid any confusion in the future then maybe there is some merit in that. It's up to you but it will not change the function of the crossover whatsoever.

Look at it like this: One side of the coil is attached to C1 and the other side of the coil is attached to C2, C3, and C4.

 

[tuffstuff1]

@tuffstuff1
The jumper between C3 and C2 is sufficient as it will attach the coil to both points electrically. If you move the coil wire to C2 with the jumper in place you have only attached the coil to the other side of the jumper - the electrical connection is the same. If you want to more closely match the drawing from McIntosh to avoid any confusion in the future then maybe there is some merit in that. It's up to you but it will not change the function of the crossover whatsoever.

Look at it like this: One side of the coil is attached to C1 and the other side of the coil is attached to C2, C3, and C4.

Duh! I see that. Had a brain freeze. I think I'm in good shape now. I ordered the resistors from your example. I really appreciate your thread and the effort you put forth laying this all out for us. I'll post a couple pics of my crossover when it is done. My new caps are much larger than yours. There were two to make up the 150UF. There's a 50UF and a 100UF. It's going to be tricky to make them fit. I already have a MQ-101 equalizer. That is why I snagged these speakers on the cheap and heard great things about them recapped with the EQ. Do you use an EQ? Thanks again!

 

[Refugee]

I do use the EQ. These speakers are in my main system. You can see what I'm using in my signature.
What brand are the caps?
Please post a pic when you are done....very curious to see. I am always glad to see this great gear refurbished and used.
See Roger Russell's site for some good reading about these speakers.

http://www.roger-russell.com/ml1cpg.htm

 

[tuffstuff1]

I will. I bought the caps off of the auction site before I saw your post. The caps are MPT. Big yellow caps. I bought the system containing a C-26 and a MC-2100. The speakers were Bozak and the MQ-101 was on the Bozaks. I wanted all MAC system though, thus the ML-!C. Thanks for the info.

 

[tuffstuff1]

I rebuilt one crossover and installed it. It works but the upper mid domes on both speakers are toast. I feel stupid for believing the seller these were good. It was sooooo long ago when I bought these speakers. It's probably been 10 years ago already. Anyway, I wonder if I should scrap the project and stop putting good into bad or replace the mids with the Morel as you have mentioned. Do you know which Morel driver to use and where to buy it? Now I probably have to modify the crossover to go with the Morel as well. Do you have any information on which resistors or caps would need to be modified on the crossover? I did put a lot of work into the cabinets. What to do?

 

[tuffstuff1]

I rebuilt one crossover and installed it. It works but the upper mid domes on both speakers are toast. I feel stupid for believing the seller these were good. It was sooooo long ago when I bought these speakers. It's probably been 10 years ago already. Anyway, I wonder if I should scrap the project and stop putting good into bad or replace the mids with the Morel as you have mentioned. Do you know which Morel driver to use and where to buy it? Now I probably have to modify the crossover to go with the Morel as well. Do you have any information on which resistors or caps would need to be modified on the crossover? I did put a lot of work into the cabinets. What to do?

Any takers on this? If not I'm going to shove all the new parts in the cabs and stow them away for another 10 years lol.

 

[Johnny_Law]

When I restored my ml-2c a few years ago, I decided to bide my time and wait for good used original domes to pop up. It took a couple years but eventually they did.

ML-2C PROJECT COMPLETED: Custom mid-tweeter arrangement

Picked up a pair of ML-2C's with some custom drivers. Anyone ever see anything like this before? They actually sound pretty good! Crossover looks all original, woofers all freshly re-foamed, all drivers work. Early-ish serial no.s (L2C682 and L2C686). I think after a re-cap and a re-finish...

audiokarma.org

 

[eiraved]

I have kept an eye out for some XR-7's for a few years now. They have long been on my wanted list. I'll bet they really satisfy once you get around to the refurb.

I'll have to pick up a MQ101 or MQ102 equalizer. I had three MQ102's at one time, unfortunately sold them all.

 

[eiraved]

I rebuilt one crossover and installed it. It works but the upper mid domes on both speakers are toast. I feel stupid for believing the seller these were good. It was sooooo long ago when I bought these speakers. It's probably been 10 years ago already. Anyway, I wonder if I should scrap the project and stop putting good into bad or replace the mids with the Morel as you have mentioned. Do you know which Morel driver to use and where to buy it? Now I probably have to modify the crossover to go with the Morel as well. Do you have any information on which resistors or caps would need to be modified on the crossover? I did put a lot of work into the cabinets. What to do?

Caps will definitely will help today. Now if you want to increase the dynamic ability of a ML1 above 40 HZ Roger Russel designed an update replacing the orange dome and tweeter with Morel drivers. Audio Classics has all the info. Just ask for Ryan or Steve.

Have you contacted Ryan or Steve at Audio Classics yet?