Restoration McIntosh ML-4c

I am in the process of updating the drivers on the ML-4C. I have redone the crossover schematic to match the crossovers documented in the ML4C service manual(also attached). The new drivers are the MDT40 and MDM55 made by Morel as recommended by Roger Russel in his restoration info attached to this thread, The manufacturer published 0 degree FRD/ZMA for those drivers are also attached. I also attached the SPL graph from VituixCAD for the upper/lower midrange and tweeter reponses and the VituixCAD file for this speaker system(change the extension on the ml4c_all_speakers_schematic file to ml4c_all_speakers_schematic.vxp, in order for it to load into VituixCAD). The Woofer and Midrange schematic is included but is detached from the main crossover because I do not have the FRD/ZMA for those old drivers. I am posting this info hoping someone has the frequency responses of those drivers to verify the 1.5K crossover and overall axial response. If not available and I've searched everywhere, likely I will have to measure those drivers... but being the ML-4Cs weigh more than a fridge, I'm not looking forward to that.

I had previously updated the crossover components in 2021(pandemic project) with the same original schematic values and brought life back into those speakers.

ML4C before.jpg

ML4C After.jpg

I'm wanting to update the drivers so I can get some more life from these wonderful speakers.

Any comments on the crossover are welcome. Sadly, Roger Russel is no longer available to us.


  • mcintosh_ml4c_info.pdf
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  • Morel MDM55.frd
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  • Morel MDM55.zma
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  • Morel MDT40.frd
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  • Morel MDT40.zma
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  • ml4c_all_speakers SPL.png
    ml4c_all_speakers SPL.png
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  • ml4c_all_speakers XO-schema-1.png
    ml4c_all_speakers XO-schema-1.png
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  • ml4c_all_speakers_schematic.txt
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