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How to get more open sound from Monolith III

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georgehifi

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This mod will give a more open and dynamic sound to the Monolith III, the electrolytic 100uf cap C2A should be changed for a good quality polyproplene of the same value, at least 150volt or more voltage rating, you might find it hard to get 100uf so you can parralel say 2x40 and 1x20 to get the value. Suggested makes Wonder Cap, Solen,Clarity, Relcap, Aurie
It's well worth the effort to do, and remember that poly caps this big need time to run in.

Thanks again to Jim Power for the circuit diagram of the Monolith III

Cheers George
 

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BigGuy

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Monolith III Passive Xover Mods (Resurrected)

This mod will give a more open and dynamic sound to the Monolith III, the electrolytic 100uf cap C2A should be changed for a good quality polyproplene of the same value, at least 150volt or more voltage rating, you might find it hard to get 100uf so you can parallel say 2x40 and 1x20 to get the value. Suggested makes Wonder Cap, Solen,Clarity, Relcap, Aurie
It's well worth the effort to do, and remember that poly caps this big need time to run in.

Thanks again to Jim Power for the circuit diagram of the Monolith III

Cheers George
Does not look like this thread went very far. I am interested (after all this time) in this topic since I have a pair of Monolith I's which were upgraded many years ago to III status with the new woofer and passive crossover. Not a techie but have read about deterioration of electrolytic capacitors over time. Since the speakers were "voiced" with certain components, am I better off replacing the "C2" Elcap (100 mfd, 100 VNP) with direct replacement still available from Martin Logan or switching to a polypropylene cap as suggested? To George's point, there are not a lot of 100 mfd polypropylene caps out there but have found Solen and AEon (Axon?) caps available from Michael Percy with higher voltage, e.g., 250, 400, 630, ratings. I understand that higher voltage rating may yield sonic improvements :music: over the 100 mfd original.

Also, are there other crossover mods which members feel offer improvement(s) over the original passive crossover design?

Thanks.
 
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ted betley

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Try a polypropelene bypass of 2-5 uf. I just installed a 5 uf one in my logan x-overs and it indeed changes the sound to be more open
 

BigGuy

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Appreciate the feedback, Ted. I assume you bypassed the 100uf ElCap. Would it be advantageous to also bypass the 470uf ElCap or even the 39uf Solen?
 

BigGuy

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After some additional consultation, made the following mods to the crossover:

C1, Elcap 470uf: Bypassed with 1 x 5uf+/-10% Electrocube;

C2, Elcap 100 uf: Replaced with 2 x 50uf+/-10% ASC
+ 1 x 2uf=/- SEC 98-28
+ 1 x 0.1uf Vishay ERO MKP 1837
Combo matched to within 0.1uf

C3, PB 3900 MKP-FC 39uf: Bypassed with 1 x 0.33uf+/-1% SEC

C4, Elpac 10uf: Bypassed with 1 x 0.1uf Vishay ERO MKP 1837

Even after limited hours of burn-in with "IsoTek Full System Enhancer & Rejuvenation Disc" and system play, notice a significant improvement in low level detail and presence. Well worth the effort though a bit of a challenge to get "10 lbs of caps in a 5 lbs bag"!

CIMG0369_25%.jpg
 

pidigi

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II to III

Does not look like this thread went very far. I am interested (after all this time) in this topic since I have a pair of Monolith I's which were upgraded many years ago to III status with the new woofer and passive crossover. <snip>
Hi BigGuy!

I own a pair of Monolith II and since I have to replace the woofers (I have tryed to refoam them but the result is not completely satisfactory; in any case now the foam is gone again) I'm very interested about your upgrade. Is the woofer of the Monolith III different from the one of the II's? The upgrade from the series crossover to the parallel one is worth the effort?

Thanks in advance,

Paolo
 

BigGuy

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Hi BigGuy!

I own a pair of Monolith II and since I have to replace the woofers (I have tryed to refoam them but the result is not completely satisfactory; in any case now the foam is gone again) I'm very interested about your upgrade. Is the woofer of the Monolith III different from the one of the II's? The upgrade from the series crossover to the parallel one is worth the effort?

Thanks in advance,

Paolo
I know little if anything about the Monolith II edition. NOTE: In fact, M-L is looking for manuals, specifications, etc. for this model so, if you have any literature, I would contact them if you have a mind to. I am sure it would be appreciated. I would not mind having information on the II myself if you care to share. From what I remember, the replacement woofer WAS different but unfortunately I do not have specifics and there is nothing visible without removing the woofer itself to see the back. Perhaps another member would be able to supply this information. As I remember, there was a considerable improvement in the overall sonics with both the woofer change and the replacement of the internal crossover with the external passive crossover. If you go the route of the external passive crossover, capacitor modifications similar to those mentioned in my 05/23 post are quite dramatic in a positive way!
 

pidigi

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monolith II

unfortunately I don't have any literature about them. All I know is infact what I can see.
About the woofers, there are some figures printed on the magnet
-X3600
-1036
-8623

(hey, is this meaning they are from 1986?)

I was thinking about a peerless 830669, but with the availabe volume of the box it is quite difficult to obtain a good loading... so I'm considering other options to upgrade.

Ciao!

Paolo
 

TubeHeaven

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I'm surprised people say any of them aren't "open" sounding. I own the II's and they are so transparent they are ruthless on less and good recordings. I;d highly recommend you experiment with some other upstream gear such as the amp and pre before changing out parts.
 
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