Jump to content

RTR001

Old Martin Logan Aerius Crossover rebuild

Recommended Posts

I recently picked up a nice old pair of Martin Logan Aerius speakers (built May 93) which I’m looking to do a complete rebuild of when I find the courage to do so. I’m looking for some advice as to the best way of tackling the crossovers since the majority of the existing caps are 25 year old electrolytics.

 

Martin Logan sent me the crossover schematic which I’ve included below. Reading this I’m looking at 2 of each of the following caps:

For the top end: 10uF, 15uF & 22uF

For the woofer: 80uF, 100uF, 470uF

 

The inductors are air core so I’m not going to worry about those or the resistors.

 

I don’t have a small fortune to invest in super high end caps so am considering some bypass options as well as some premium ELKO caps for the bottom end - I may need to combine a few to get the 470uF.

 

I’ve looked into this a little and there is a lot of talk about using the Vishay MKP1837 0.01uF (readily available at Speakerbug) as a tiny bypass cap. At this stage, for the ESL panel capacitors, I’m *thinking* about using a combination of Jantzen Standard Z-caps and Premium Z-caps where my budget will allow and add a bypass to each using the Vishay.

 

I haven’t had any experience with bypassing though so I’m unsure if this is the best approach or even a good one. The speakers which I’ve recapped have always just been like for like values.

 

I would appreciate any suggestions & advice

ML Crossover.JPG

Share this post


Link to post
Share on other sites

I’ve used the Vishay MKP1837 0.01uf as a bypass on a 47uf and 25uf MKP on/off....beat me if I can tell the difference.   Not sure if you are going to notice the difference in a XO network for speakers.  I’ve used them for psu bypass too on electrolytic 100uf....

However utilising these instead of ceramic smooth the SQ up in a input fet stage.    The ceramic that was replaced were for RF suppression.

Share this post


Link to post
Share on other sites

Not capacitor related, but the main problem with all ML speakers of that vintage is that the conductive coating on the Mylar membranes degrades over time. I have heard that the conductive particles float off the membrane as they get attracted to the charged stator panels, eventually leading to a dull lifeless sound in the speaker. Some call it a fatal flaw, but my suspicious nature tells me it was a bit of planned obsolescence by ML as they did a roaring trade with replacement panels @ $1-2K a pop!

 

Also, ML panels are difficult to take apart being glued tightly in place (with risks of bending and crumpling the metal stators) making refurbishment difficult. If you do manage to remove the stators successfully, then it is just a matter of recoating the Mylar membrane with a specific conductive liquid solution. A repair kit for all electrostatic speakers can be purchased cheaply from Rob MacKinlay at ER Audio.com in Western Australia.

 

Once repaired in this manner the MLs should go for another 10yrs+. Btw, I don’t think the newer ML speakers are prone to this problem.

 

Steve.

Share this post


Link to post
Share on other sites
Posted (edited)

Maggie’s have a different kettle of problems ...aluminium strips attached to a moving plastic sheet of mylar/kapton, the glue denaturing over time and causing the sheet to resonate, flap and rattle. 

Edited by Steve M

Share this post


Link to post
Share on other sites

Thanks guys, I'm tackling the panels separately and have already spoken to Rob and a few others :)

 

I've also read that aside from the Vishay's using corresponding values ~1% of the main capacitor is an effective bypass. I.e. Running a cheaper 10uF Janzten Z-cap in parallel with a 0.1uf Superior/Silver Z-cap. Not sure how effective that is? 

 

Given that the panels are so revealing (when working 100%) I'm keen to get the most out of the crossover within my budget of a couple of hundred dollars.

Share this post


Link to post
Share on other sites


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By rocker4ever
      Teac X-3 Needs a belt. Got all the screws off the front panel and the parts that come off. Even took the back off.
      The front panel is loose on top/bottom  and both sides. Can get about 1/2 inch if pull lightly BUT seems like something in the middle by the heads is stopping it.
      A close look shows that it should lift right up from there. No need to take off the heads assembly. Tried looking for some screws from the back with no luck.
      Got a schematic and looked ... either I'm blind or somethings wrong. Can anyone tell me the exact procedure to get this panel off so I can put new belts on and see if anything else if needed. I would really appreciate it. Thanks guys.
    • By Raab
      Hi everyone,
       
      I'm looking for some advice for a good budget stereo amp and floorstanding speakers combination?
      I'm definitely want used equipment but that means I wont necessarily be able to try them in combination before I buy.  
       
      Budget is ~2500
      Room: 3.5m x 7m, wooden floors.
      Music: Classic rock, Metal, Reggae, Electronic.
      Source: Spotify (probably using Chromecast audio, unless someone recommends an amp with Spotify Connect?)
       
      Any advice or experience people have would be greatly appreciated!
      Cheers
    • By fire
      I am totally  newbie into this turntable and LP, just got myself a very first turntable Denon DP 30L mk2, with D20E/II cartridge in good condition, but needs some good clean. 
       
      any suggestions to upgrade this cartridge ? which one is the best option for a newbie like me? 
       
      Any one has this Denon DP30L Mk2 turntable? 
      And also where is place to but some second handed LP in Melbourne?
       
      Many thanks
       
      Jason
    • By Johnno2017
      Bought a Sotm SMS 200 unit from a SNA member last week to replace my Sonos Connect. I can see why the Sonos is so successful as it is so easy to use, just plug, simple 1-2-3 setups and play. 
       
      I cant say the same for SMS 200, I got nowhere further than seeing power up and ethernet light up. Tried to connect my PC to SMS 200, but all I got was error messages. 
       
      Sotm instructions, Google and Youtube were my reference for help. Now, here I like to ask for help, possibly some pictures of your connection. 
       
      Equipment : 
      - Laptop (PC)
      - Sotm SMS 200
      - Lan Cables CAT 5 
      - Modem router
      - TP-LINK Power Adapter
       
      Connection attempt 1
      - connected pc to sotm with lan cable
      - tried the ip thing 168.192.1.0 and //euhasu and eunhasu.local
       
      Connection attempt 2
      - connected sotm to modem router with lan cable
      - pc connected to the same modem router with lan cable 
      - tried the ip thing 168.192.1.0 or 1 and //euhasu and eunhasu.local
       
      ##Goal is to use squeezelite to play tidal.##
       
      Thank you for reading !!
       
    • By dsj88
      I'm trying to play an MKV movie file off of an external hard drive.
      I've plugged it in the the front USB port, plugged the power cord in, the hard drive lights up and spins up fine but nothing happens on the Oppo.
      It's a USB 3.0, NTFS file system that works fine on my computer. I don't see any option on the Oppo's menu to play something off of external media. For all I know it could be detecting the hard drive fine but I just don't know how to access it.
      Any help would be appreciated.
×