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

Discussion in 'McIntosh Audio' started by Johnny_Law, Aug 14, 2016.

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  1. Johnny_Law

    Johnny_Law AK Member Subscriber

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    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, they may make it inside to meet the C24/MC502 and see if any magic happens. I'm pretty excited to have a full McIntosh system (minus the turntable, will use the AR-XA until I find a Mac TT).

    [​IMG]

    [​IMG]

    [​IMG]
     

     

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  2. damacman

    damacman Blown and Injected Subscriber

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    Nope - those are unique!
     
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  3. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Interesting ... I'll probably pull them all and see if I can figure out what they are and how they compare to the original equipment.
     
  4. Johnny_Law

    Johnny_Law AK Member Subscriber

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    The story is that these came from / were likely modified by a shop called Trend Electronics in San Francisco, and were acquired from the shop owner Gordon Wagner or his brother Stuart. I am seeing if I can get in touch with either. Maybe someone here knew them or the shop when it was in business?
     
  5. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Well I'm at a fork in the road here. These have ended up sitting in my garage while other projects came and went. Now I need to decide whether they are worth finding original tweeter and midranges. Or, if there are any suggested replacement tweeters and midranges that are reasonably priced? It looks like I can remove the front wood panel and replace it with a fresh one pretty easily (judging from visible screws - unsure if screwed / glued from the back).

    What would the group do here? What's the best move?

    Get new front wood panels, and
    -Find original components (tweeters, midranges, mesh covers), or
    -Find replacement components (tweeters, midranges) and original mesh covers

    Don't get new front wood panels, and
    -Part them out because it's not worth it
     
  6. motorstereo

    motorstereo AK Subscriber Subscriber

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    If it was me I'd either find a spot like a garage or outbuilding where cosmetics aren't important or sell them as is. I see way too many headaches getting them back to original and presentable. Even if you did get them back up to snuff cosmetically, recapped and all you still should use the MQ101 with them and that adds still more $$.
     
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  7. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Thanks ... well, I should note that I realized the tweeters pictured above are in fact KEF T27s. I happened to be in need of a KEF T27 for some Ref. 104s ... so I stole it from the ML-2C. :p

    I guess I could refurb or replace the bad T27 I have, maybe, but I'd need to spend some $ on the T27 or a replacement either way.

    I did in the meantime acquire an MQ102 - so I do have that already, if it changes the calculus.

    If I was to try to find replacement drivers, any de facto standards or suggestions? I didn't catch mention of aftermarket replacements from Mr. Russell http://www.roger-russell.com/drivers.htm, http://www.roger-russell.com/ml2cservice.htm, http://www.roger-russell.com/speakers.htm#ml2c
     
  8. damacman

    damacman Blown and Injected Subscriber

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    If they sound good, why not just retain the parts and keep the grilles on? WGAF?
     
  9. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Mainly because I cannibalized one for one of the T27s so I'd need a new tweeter anyway, but also because I'd like to hear them as they were originally made - or get as close to that as I can - if feasible.

    I should see if I can figure out what those strange dome midrange drivers are.
     
  10. damacman

    damacman Blown and Injected Subscriber

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    You can email roger via his web site. He'll help you with driver info. You may also call Audio Classics
    to see if they happen to have any parts or leads.
     
  11. c_dk

    c_dk Addicted Member

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    I have two pair of ML 1s that have been holding down the floor boards in my shop space for years.........

    Back in the 80's Mac parts was having much difficulty supplying replacement domes. They were unable to get replacement magnet structures so we were without replacement midranges for more than 6 months.

    A lot of customers as well as salespeople found the voicing of the Mac speakers to be dull sounding so it would not surprise me that a local dealer might try to resolve both issues by modifying a set of his speakers before offering this option to customers.

    How much do you think it would cost to replicate the cabinet at todays prices? Do you find the cabinets attractive? Do you know anyone who does?

    I have one ML and two XR domes left.....you need four, I would not want to face the bill for 4 ML domes..... If you could find them.

    I have had a little success in finding drop in driver replacements. We also did do a RR designed and sourced ML driver update with marginal success. The owner was happy, we found it to leave a lot of possibilities behind.

    If the cabinets are found to be worthy of refinishing and are then able to find a new home, it should be possible to update the midrange structure of the speakers to enhance the already well done bass.

    RR did this with his Morel driver update but again he voiced the replacement sytem for concert hall row twenty so we had to quickly follow his revised crossover design and remove all his dropping resistors to keep the owner happy. The revised voicing curves still showed row 16 but the owner found this to be acceptable.

    You have a challenge in front of you.....
     

     

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  12. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Hmm. Ok so maybe I would be better suited with the drivers already in there, and just cleaning up the front baffle...

    If I were to find modern replacement drivers, the frequency ranges are pretty clear from the literature. The mid mid-range has to handle 1.5kHz to 3kHz, the high mid-range has to handle 3kHz to 7kHz, and the tweeter has to handle 7kHz and above. I'm just not sure what the impedance curves look like for the originals. Anyone know if that information exists anywhere?
     
  13. c_dk

    c_dk Addicted Member

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    Have your checked the crossover for changes that might have been done when the new drivers were installed? Roger did a lot of massaging of the inherent inaccuracies in the original mid dome 036-016 compared to the later 036-035 mid dome. I would expect that those might have been changed back in the 80s repair.

    The original ML2s would measure +3 at 100 hz, 0 at 1000, and be down -6dB at 10,000 in a typical American living room of that day....certainly reinforced their dull sounding image.
     
  14. Johnny_Law

    Johnny_Law AK Member Subscriber

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    The crossover may have been modified. I am not sure what the two resistors in series are, and I don't know where that red wire goes. I'll have to dig into it more closely.

    [​IMG]

    Curiously, these have 018 8" midranges in them, but they have cloth surrounds. According to Roger Russell, the 018s were supposed to be identical to the 002s but with foam surrounds. Weird.

    [​IMG]

    So how am I going to save these? My plan is to remove and replace the front baffle. I would like to use better drivers for the upper mid (in place of the 016s) and tweeter (in place of the 012), and arrange them in an MTM configuration. Currently I have the Celestion HF1300s to replace the 016s, and Philips dome tweeters to replace the 012s. Open to suggestions.

    Here're all the drivers waiting for action (and the 001s waiting for fresh foam; previous "fresh" foam was a sad, sad hack job, according to previous owner by A Brown Soun in the north bay):

    [​IMG]

    However, I am having trouble removing the baffle. I have removed the screws indicated by the red arrows, to no avail. Has anyone removed the front baffle from ML-2Cs before?

    [​IMG]
     
    Last edited: Jul 15, 2018
  15. damacman

    damacman Blown and Injected Subscriber

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    My bet is that they're glued solidly to the cabinets.
     
  16. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Confirmed, glued in place, and more. The upper portion of the baffle extends up behind the trim piece between the side panels and the top of the cabinet. This is the trim piece to which the upper grille receivers are mounted. So, it doesn't seem like the baffle can come out unless the top panel is removed, unlike the rear panel, which does not have the trim panel to block it and comes right out:

    [​IMG]

    This seems like it could be extremely difficult, and I've never done this before. The trim piece seems to have a tongue and groove joint into the top of the side panels. You can see how the trim is blocking the front baffle by comparing it to the rear access panel pictured above.

    I'll start reading up on the process of disassembling a glued groove joint in a speaker cabinet, which hopefully has been covered.
     
    Last edited: Jul 15, 2018

     

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  17. c_dk

    c_dk Addicted Member

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    Why not just route a rabbit, or groove to accept a sub baffle to replace the section cut out to accept the earlier replacement drivers.

    You could attach additional strips behind the now lap joint to reinforce it and if you hold off gluing the sub baffle in place you could easily try different drivers and driver layout.

    I am sure a common modern 4 inch cone mid driver and super tweeter will out perform the 40 year old drivers......you might consider placing the mid driver as high in the cabinet as possible with the super tweeter lower.....

    For the ML1s my son now has,I unwound enough of the 8 inch driver's crossover inductor to raise it's response up to 2.5k so it could cross to a basic 1 1/8 dome. If using a 4 inch mid I doubt that would be needed.

    Still another pair on Ml1s to do......I think the Bessel array as used in many pro speaker arrays and in past Mac designs might be interesting.
     
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  18. Johnny_Law

    Johnny_Law AK Member Subscriber

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    Thanks - I had thought of that but lack the skills / tools to do so. What process / tools could I use? I never back down from an excuse to buy more tools for the workshop. I haven't yet made the jump into woodworking tools but this sounds like a good chance to do it!

    Your idea sounds even better now that I've realized the front baffle is stepped on the bottom too, so it doesn't seem like I can remove it without taking the top totally off, and sliding it up and out.

    So now that the front baffle removal is kind of out the window (that was short-lived wasn't it), I'll start looking up how to make a clean square cut into the front baffle, so that I can cleanly insert a sub-baffle with the new upper mid & tweeter drivers.
     
  19. c_dk

    c_dk Addicted Member

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    A good plunge router with a sled that spans the width of the speaker cabinet would be the place to start.

    There was a article in Fine Woodworking magazine years ago showing a celebrity actor using a router and sled to flatten huge slab desk tops.

    I am sure some other member will know the actors name and/or the magazine # , but while not exactly the route you need to go it would give you the basic starting point.

    You would need to limit the horizontal travel of the router to keep it under control but once you cut a groove half the depth of the baffle the inner part could be cut through with a jigsaw.

    Then a replacement sub baffle could be cut with a table saw and dado blade......so you could at least justify 4 new woodworking tools.....I am sure we could collectively justify a few more for you.....
     
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  20. Johnny_Law

    Johnny_Law AK Member Subscriber

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