Monolith iiixb

[Steevray]

Just got a nice set of Monolith iii with active crossover. They are in pristine condition. My only complaint is the subwoofer. It sounds pretty dated . Any members out there with the suggestion to replace the all stamped with steel woofer with a nice new cast one? I heard that Peerless has a drop in replacement.
I would really like to hear from any person who is a monolith iii owner. How do you think they compare with newer technology at Martin Logan.
Best
Steve

 

[JonFo]

Hi Steve, welcome to the MLO !

The topic of woofer replacement on older generation models is an increasingly common topic, so much so I'm thinking of consolidating the last dozen years worth of threads into a single article to condense and index the subject.
But for now, you can start by reading my thread updating the III with the Peerless woofers: Monolith refresh - Panels, woofers and rail stain updates

As a fellow Monolith owner, I'll be happy to help. But I have posted a ton of info over the years as I've modded my units. Just do a site search and read my system thread, I usually index the threads with significant content in that system thread. First post has a lot of links.

 

[JonFo]

...
I would really like to hear from any person who is a monolith iii owner. How do you think they compare with newer technology at Martin Logan.
Best
Steve

I believe that with an active XO and a woofer refresh, the Monolith is quite competitive. I find that segregating the very low end to subs is necessary for best performance. So crossing over around 60Hz is important to improving the upper bass (150 - 300Hz) performance. As the woofer is overmatched by the big panel at high volumes.
Not sure in what condition your panels are, but I found a nice step up when I replaced mine 12 years ago. The new ones have not changed one bit since, but then I have an ideal setup and take good care of them.

So for the money, a used Monolith, refreshed, and running on an active XO and with appropriate amplification, is quite the bargain, and it's why as much as I love the new ESL line, I'm not tempted to change.

Now, that big panel does mean even more placement challenges and absolutely demands room acoustic treatments to deliver all the goodness it is capable of.

 

[Steevray]

Hi Johnathan
Thanks for the reply.
Just a quick thought.
Are you familiar with Danny at GR Research.
He has open baffle single, dual and triple servo open baffle sub kits.
Thought there could be a way to incorporate in with the Monoliths.
I'm A Newbie and think I might have been trickeed .
A guy let's call him Dave, lives in woodland Hills and claims to know everything and everybody at Martin Logan. Got them home a few days ago and something is wrong with the electronics in one. Both panels work fine ) took out the one that sounded fine and installed it in the problematic speaker. Presto! Both panels work fine.
Marcus at ML suggests George Myers in Southern California to look at them.
I look forward to discussing the ins and out of these beautiful speakers.
Best
Steve

 

[JonFo]

... Are you familiar with Danny at GR Research.

Yes, I've long admired his line-array designs. But I've never interacted with Danny.

He has open baffle single, dual and triple servo open baffle sub kits.
Thought there could be a way to incorporate in with the Monoliths.

Remember that the woofer in the Monolith is not a 'sub', it has to deliver well into the 250Hz range thanks to a 12dB/Oct. slope in the stock XO.
I recommend running the XO at 24dB/Oct, pinned at 300Hz, and further crossover the low-end at 60Hz (also using 24db/Oct LR filters) to a true subwoofer.
So yes, replace the woofers with the same Peerless models I run, and you can then play around with any type of sub you want to see how that goes.
But I'll admit I'm not a fan of open-back anything, especially in the low-end. To me, two or four sealed subs, carefully located to minimize room modes and then time-delayed and matched (using a miniDSP or similar) is the ideal.

... Got them home a few days ago and something is wrong with the electronics in one. Both panels work fine ) took out the one that sounded fine and installed it in the problematic speaker. Presto! Both panels work fine.
Marcus at ML suggests George Myers in Southern California to look at them. ...

Which 'electronics' are you talking about? The board that sits inside the woofer cabinet, or something external?

 

[Steevray]

Lots of great ideas. Thank you very much. Your final woofer was the peerless. Model number? Yes, I really respect Danny and his knowledge. I have never heard an open baffle woofer. People seem to be really loving them for some reason. Very hard to place.
The parts that I will be sending in to George Meyer are the internal parts in the woofer compartment.
Steve

 

[JonFo]

As linked to in my thread
https://www.martinloganowners.com/t...h-panels-woofers-and-rail-stain-updates.2025/
The Peerless 830699 is it, both PE and Madisound have it

https://www.parts-express.com/peerless-by-tymphany-830669-12-paper-cone-sls-subwoofer--264-1118
Madisound
https://www.madisoundspeakerstore.c...rless-sls-830669-12-woofer-coated-paper-cone/

The parts that I will be sending in to George Meyer are the internal parts in the woofer compartment.

Great, keep us posted on how that goes. For many older-gen users whose units are now >25 years old, having a person who can update those boards would be handy. Please PM me his contact info.
I'm considering having mine recapped and installing an Amplimo step-up transformer as a 'tweak', since I have such granular control of all other parameters.

 

[Steevray]

As linked to in my thread
https://www.martinloganowners.com/t...h-panels-woofers-and-rail-stain-updates.2025/
The Peerless 830699 is it, both PE and Madisound have it

https://www.parts-express.com/peerless-by-tymphany-830669-12-paper-cone-sls-subwoofer--264-1118
Madisound
https://www.madisoundspeakerstore.c...rless-sls-830669-12-woofer-coated-paper-cone/

Great, keep us posted on how that goes. For many older-gen users whose units are now >25 years old, having a person who can update those boards would be handy. Please PM me his contact info.
I'm considering having mine recapped and installing an Amplimo step-up transformer as a 'tweak', since I have such granular control of all other parameters.

Thank you so much for your invaluable information. Unfortunately since we have chatted my close friend has passed. Of course that is taking up all my time. However the one thing that gives me solace is to be able to keep my hands busy. On your recommendation I am going ahead and purchase the peerless roofers. I do have the active crossover. I alhave very little knowledge but have the equipment for measuring. I purchased If you things like the microphone and such from parts express. After getting on my feet I will really look forward to chatting with you again. Thank you so much

Best

Steve

 

[JonFo]

Steve, sorry for your loss. We'll be around, just post to this thread when you get back to it.

 

[Steevray]

Steve, sorry for your loss. We'll be around, just post to this thread when you get back to it.

 

[Steevray]

Thank you so much. I know it's a big ask but I would love to hear from any of the members who might have the working electronics for the monolith 3.
I am so desperate and would love to hear these speakers.
Being the newbie I am I fell for a scam. Some guy named David in woodland hills rip me off. Times are hard but I wish people were just a little more honest. Anyway I guess he needed the money more than I did.

 

[JonFo]

Steve, thanks for the pics. Interestingly enough, it looks different than my Monolith III. Seems yours are from a later run where they use numeral 3 instead of the roman numeral III.
And it has the new(er) logo and the Signature scrawl at the top. Based on the respective serial numbers:
Your Monolith 3 was built in February of 1998, and is the first of the second set made that month.
Note for posterity: unit numbering had been zero-based, as my units have 000 and 001. But it looks like you have 003 and 004, so they must have changed to be 1-based at some point.

Here's is a picture of the back of mine:

Mine was built in January 1993.

 

[JonFo]

Steve, also, do not underestimate the possibility of a wiring problem in the problem speaker base. The leads from the internal board (pictured above) to the terminal block at the top of the unit might have a misconnection. Something could have come lose in transport.

snarky comment: I find it hilarious that many spend big bucks on garden hose sized speaker cables, and then you see that the final 8 inches or so of wire are like 18GA at best. So even my moderately priced BlueJeans Wire Belden 12GA wire pictured above is overkill.

 

[JonFo]

Also, I recall there are occasionally issues with the music sense circuit and if it fails to trigger, then the unit does not energize the ESL HV circuit. You might try and bypass that to test.

Otherwise, I'm guessing you will need a tech to test the board and replace whatever is busted or out of spec.
Over the years, it's been anything from a resistor going out of spec to HV board transformers blown by power surges.

 

[modavid]

I have receive lots of good information from participants of this tread. I though I would share some of my experiences. I used the Peerless 830699 on my III's for a while now. I recently made a change which is delivering awesome results. I purchased the Goldwood GW-12PC-4 12" Heavy Duty Woofer 4 Ohm ( the original Eminence woofer was a 4 ohm). The woofer fits perfectly in the cutout. You will not be able to use the existing Hex bolts and T-nuts due to differences in hole diameter. I applied some foam weatherstrip to the woofer to seal the mounting from air leaks. Ran AB comparisons with the goldwood and peerless woofers. The Goldwood is superior to the Peerless in every sense. Base is much more detailed and has more punch. Mid bass is more accurate and defined. They also sound exceptional along side my Depth i subwoofer. The Goldwood driver seemed a little quieter in the upper bass. I copied the external passive crossover to XSim software and applied some tweaks. There are 2 coils each rated at 5 Mh on the low pass filter. I removed and shorted the connection point of one coil to lower the inductance to 5 Mh. This will move the crossover point of the woofer slightly higher frequency. Again tested. This made a big impact on the overall sound and i had no problem getting one of those coils out of the way of the signal path. These speakers now sound complete by themselves. Soundstage is now blowing me away. I was able to reduce the frequency of the sub so it only reproduces the lowest frequency demand. Overall I'm very pleased with this setup. The peerless woofers were a improvement initially but they tend to sound pretty muddy compared to the goldwoods. I have listened to Wilson Audio and Wilson Benesch speakers at my Audio dealer and honestly while I would love to own them, they just do not sound $60k better better than my upgraded and freshened Logans to my ears. They still present "the sound is coming from a cone dynamic". Once again I keep returning to my Logans. There is really nothing better than ESL speakers in my opinion. If you can get a hold of some worn out Monolith III's, they would be worth restoring.

here are all the improvements so far.

1. Stat panels replaced last year ($2600). Once again big improvement.
2. Replaced the electrolytic caps in the crossovers with music rated devices.
3. Replacement of Woofer with Goldwood model. Upgraded connection wire to woofer w/ Duelund signal wire
4. shorted one inductor coil to lower the total value.

Running MyTek Manhattan II DAC, Krell FPB MC-350 Monoblocks, Bi-Wired connection to speakers w/ MusicLink Super speaker interconnects. Shunyata Alpha XLR interconnects.

 

[Brad225]

Congratulation. Glad to hear you have brought them back to life and they sound that good.

 

[Robert D]

I have receive lots of good information from participants of this tread. I though I would share some of my experiences. I used the Peerless 830699 on my III's for a while now. I recently made a change which is delivering awesome results. I purchased the Goldwood GW-12PC-4 12" Heavy Duty Woofer 4 Ohm ( the original Eminence woofer was a 4 ohm). The woofer fits perfectly in the cutout. You will not be able to use the existing Hex bolts and T-nuts due to differences in hole diameter. I applied some foam weatherstrip to the woofer to seal the mounting from air leaks. Ran AB comparisons with the goldwood and peerless woofers. The Goldwood is superior to the Peerless in every sense. Base is much more detailed and has more punch. Mid bass is more accurate and defined. They also sound exceptional along side my Depth i subwoofer. The Goldwood driver seemed a little quieter in the upper bass. I copied the external passive crossover to XSim software and applied some tweaks. There are 2 coils each rated at 5 Mh on the low pass filter. I removed and shorted the connection point of one coil to lower the inductance to 5 Mh. This will move the crossover point of the woofer slightly higher frequency. Again tested. This made a big impact on the overall sound and i had no problem getting one of those coils out of the way of the signal path. These speakers now sound complete by themselves. Soundstage is now blowing me away. I was able to reduce the frequency of the sub so it only reproduces the lowest frequency demand. Overall I'm very pleased with this setup. The peerless woofers were a improvement initially but they tend to sound pretty muddy compared to the goldwoods. I have listened to Wilson Audio and Wilson Benesch speakers at my Audio dealer and honestly while I would love to own them, they just do not sound $60k better better than my upgraded and freshened Logans to my ears. They still present "the sound is coming from a cone dynamic". Once again I keep returning to my Logans. There is really nothing better than ESL speakers in my opinion. If you can get a hold of some worn out Monolith III's, they would be worth restoring.

here are all the improvements so far.

1. Stat panels replaced last year ($2600). Once again big improvement.
2. Replaced the electrolytic caps in the crossovers with music rated devices.
3. Replacement of Woofer with Goldwood model. Upgraded connection wire to woofer w/ Duelund signal wire
4. shorted one inductor coil to lower the total value.

Running MyTek Manhattan II DAC, Krell FPB MC-350 Monoblocks, Bi-Wired connection to speakers w/ MusicLink Super speaker interconnects. Shunyata Alpha XLR interconnects.

So how much overall, including the cost of buying the monoliths, do you have invested in the speakers?

I'm having new panels for my Prodigy speakers produced now. I'm anxious to hear them. The rest of them is stock. They were produced in 2000. When were your speakers produced? Im wondering if any other components of mine need to be replaced. Problem is, how do you know what they should/could sound like? Don't want to spend a lot of money and have them sound no better or worse.

I also don't have the tech knowledge you do to work on them. Id most likely have to pay someone to do all the work. The idea though of taking my Prodigies with new panels and making them sound substantially better interests me.

 

[modavid]

I purchased the Monolith's used from my local Hi End dealer back in 2002 for $3500 for the pair. According to the ML archives they were introduced in 1990 and retailed for $7500 with the passive crossovers. not sure how old mine were when I purchased them. The panels were $2600 the woofers(2) $168. So essentially I have new awesome speakers for $6268. The panels woofers and crossover mods really brought these speakers back to life and were well worth the restoration investment. I will probably keep them for another 20 years or as long as my acute hearing lasts. Kudos to Martin Logan for supplying parts for these classic vintage products. I'm fortunate that one of the Martin Logan service techs lives only a block away from me. He has been very helpful.

 

[Robert D]

I purchased the Monolith's used from my local Hi End dealer back in 2002 for $3500 for the pair. According to the ML archives they were introduced in 1990 and retailed for $7500 with the passive crossovers. not sure how old mine were when I purchased them. The panels were $2600 the woofers(2) $168. So essentially I have new awesome speakers for $6268. The panels woofers and crossover mods really brought these speakers back to life and were well worth the restoration investment. I will probably keep them for another 20 years or as long as my acute hearing lasts. Kudos to Martin Logan for supplying parts for these classic vintage products. I'm fortunate that one of the Martin Logan service techs lives only a block away from me. He has been very helpful.

So you ended up buying the woofers and crossovers from Martin Logan? The monoliths are an older model than the Prodigy so id probably be in luck.

 

[modavid]

So you ended up buying the woofers and crossovers from Martin Logan? The monoliths are an older model than the Prodigy so id probably be in luck.

The panels came from Martin Logan The Woofers were sourced from Parts Express ( Goldwood GW-12PC-4 12" Heavy Duty Woofer 4 Ohm ) The original woofers Eminence made for them are not manufactured anymore. They were not that good to begin with and were the designs weak link. The crossovers are external to the speakers and came with them. There were a couple of options depending on your setup at the time. More than likely your woofers can be re-coned if they are damaged. Just contact ML tech support. They will help you out.