Monolith3 Replacement Woofers

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mikebecerr1258

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Hello All... does anyone know what the performance/physical specs of the "original" Monolith3 woofers were? I was thinking of using ScanSpeak brand speakers to replace the Goldwood Sound woofers that the previous owner used to replace the originals. I contacted the ML service/repair department, but they don't have any records to use as reference regarding the original bass drivers. Can anyone help? (there is definitely something missing in the upper bass performance... don't think it's a crossover problem, but could it be?)
 
Measure the woofer enclosure and calculate volume in cuft, find crossover freq and slope for Monolith3, calculate port volume and tuning freq for the box, then find the best woofer to match these parameters. Help with this on DIY audio.com etc... whatever woofer is in there now is prob not chosen using the existing enclosure parameters and were prob chosen based on size and cost. A thousand dollar Scan Speak woofer may sound like crap (upper bass dilemma) if not applied to the right enclosure. There is science behind this. GordonW on audiokarma is a good go to if you can contact him. Many others too.
 
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https://www.martinlogan.com/en/product/monolithiii
It appears to be a 12 inch 4-ohm woofer in a sealed cabinet. While I assume yours are passive xo, there was an active xo option. (reading from the 1989 brochure)

Two 12 inch 4-ohm aluminum woofers I recommend:
this $290 Peerless:
https://www.madisoundspeakerstore.c...835017-xxls-12-aluminum-cone-subwoofer-4-ohm/
and this $340 Scan Speak:
https://www.madisoundspeakerstore.c...s/scanspeak-discovery-30w/4558t-12-subwoofer/

Does your cabinet have a counterbore for the woofer to fit within? Hopefully these will physically fit, so check first.
 
Can anyone help? (there is definitely something missing in the upper bass performance... don't think it's a crossover problem, but could it be?)
Hi, been there, done that 😉

First, to answer the question about the crossover: YES, it is a problem! The passives on these are power-sucking PoS. Once you hear these with a correctly configured DSP active crossover, you will be glad to see them out of the loop.

As you will see from all my posts and metrics in the following linked threads, the upper-bass blend is critical to making these speakers perform at their best.
The first misconception to get over is the crossover frequency, it needs to be much higher than stock, minimum 330Hz IMHO. I give reasons why in the threads.
So you need a woofer that has low moving mass and clean frequency response up to 500Hz or higher. So 'subwoofer' drivers are not ideal.
Given the placement constraints for any ESL, the use of a sub is highly recommended, so cross over the woofer at 60 to 80Hz to that sub. A DriveRack Venue360 will handle the two-way for the L/R and still have two more outputs for subs (so you can EQ and time-align)

This thread documents my 2006 upgrade:
https://www.martinloganowners.com/t...h-panels-woofers-and-rail-stain-updates.2025/
And this one from 2020 is where we help another member, and even includes mentions of an update using Goldwood drivers, so maybe that Monolith pair is the one you purchased?
https://www.martinloganowners.com/threads/monolith-iiixb.18343/
 
Hi, been there, done that 😉

First, to answer the question about the crossover: YES, it is a problem! The passives on these are power-sucking PoS. Once you hear these with a correctly configured DSP active crossover, you will be glad to see them out of the loop.

As you will see from all my posts and metrics in the following linked threads, the upper-bass blend is critical to making these speakers perform at their best.
The first misconception to get over is the crossover frequency, it needs to be much higher than stock, minimum 330Hz IMHO. I give reasons why in the threads.
So you need a woofer that has low moving mass and clean frequency response up to 500Hz or higher. So 'subwoofer' drivers are not ideal.
Given the placement constraints for any ESL, the use of a sub is highly recommended, so cross over the woofer at 60 to 80Hz to that sub. A DriveRack Venue360 will handle the two-way for the L/R and still have two more outputs for subs (so you can EQ and time-align)

This thread documents my 2006 upgrade:
https://www.martinloganowners.com/t...h-panels-woofers-and-rail-stain-updates.2025/
And this one from 2020 is where we help another member, and even includes mentions of an update using Goldwood drivers, so maybe that Monolith pair is the one you purchased?
https://www.martinloganowners.com/threads/monolith-iiixb.18343/
Thanks for the extensive information!!! I don’t know much regarding audio technology… so which active crossovers are you recommending? Also, the thread you mentioned regarding the replacement Goldwood subwoofers couldn’t be mine, as I unfortunately have the passive crossovers!!!
 
so which active crossovers are you recommending?
If you go with the DBX DriveRack line, I can send you my configuration files for a Monolith III, saving you the days of work I put into figuring out the basic settings. The new Venu360 is a slick piece of kit: dbx DriveRack VENU360

Around $1K new, and can be found for $800 in 'Open Box' deals, or for $700 ~ $800 used.

These units are bulletproof, designed for the rough life on the road, they just loaf along in a home setting. My DriveRack 4800 has been on 24/7/365 since May 2008, with no issues.

They are managed via software from Harman called Audio Architect, which makes it straightforward to load configurations and tweak them. There is a Tablet app as well so you can do things like enabling the Sub-harmonic synthesizer function for those old 70's rock recordings whose low-end was chopped off in mastering.

They use balanced (XLR) connectors, so you will need adapter cables. The gain management on the DriveRacks is sufficient to mate with consumer gear when needed. I also have a Jensen Transformers RCA to XLR adapter box if you are interested, I used that back when my front-end had unbalanced outs.
 
Measure the woofer enclosure and calculate volume in cuft, find crossover freq and slope for Monolith3, calculate port volume and tuning freq for the box, then find the best woofer to match these parameters. Help with this on DIY audio.com etc... whatever woofer is in there now is prob not chosen using the existing enclosure parameters and were prob chosen based on size and cost. A thousand dollar Scan Speak woofer may sound like crap (upper bass dilemma) if not applied to the right enclosure. There is science behind this. GordonW on audiokarma is a good go to if you can contact him. Many others too.
Th
https://www.martinlogan.com/en/product/monolithiii
It appears to be a 12 inch 4-ohm woofer in a sealed cabinet. While I assume yours are passive xo, there was an active xo option. (reading from the 1989 brochure)

Two 12 inch 4-ohm aluminum woofers I recommend:
this $290 Peerless:
https://www.madisoundspeakerstore.c...835017-xxls-12-aluminum-cone-subwoofer-4-ohm/
and this $340 Scan Speak:
https://www.madisoundspeakerstore.c...s/scanspeak-discovery-30w/4558t-12-subwoofer/

Does your cabinet have a counterbore for the woofer to fit within? Hopefully these will physically fit, so check first.
Thank you for your assistance!
 
If you go with the DBX DriveRack line, I can send you my configuration files for a Monolith III, saving you the days of work I put into figuring out the basic settings. The new Venu360 is a slick piece of kit: dbx DriveRack VENU360

Around $1K new, and can be found for $800 in 'Open Box' deals, or for $700 ~ $800 used.

These units are bulletproof, designed for the rough life on the road, they just loaf along in a home setting. My DriveRack 4800 has been on 24/7/365 since May 2008, with no issues.

They are managed via software from Harman called Audio Architect, which makes it straightforward to load configurations and tweak them. There is a Tablet app as well so you can do things like enabling the Sub-harmonic synthesizer function for those old 70's rock recordings whose low-end was chopped off in mastering.

They use balanced (XLR) connectors, so you will need adapter cables. The gain management on the DriveRacks is sufficient to mate with consumer gear when needed. I also have a Jensen Transformers RCA to XLR adapter box if you are interested, I used that back when my front-end had unbalanced outs.
So if I buy this DBX DriveRack... how would it be hooked up into a home stereo 2.1 audio system? I have a CD Transport/DAC, Preamp, Amp, Turntable, Single Subwoofer, and Martin Logan Monolith3 speakers with existing passive crossovers?
 
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Also, is it possible that another DBX unit would better suit my needs, seeing that it is only a 2.1 home stereo set-up?
 
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how would it be hooked up into a home stereo 2.1 audio system?
In a 2.1, you would be leveraging 5 of the 6 outputs, so a 'spare' for a tactile transducer, or a second sub (recommended to balance room modes).

So the output of the pre-amp would use RCA to XLR cables to feed inputs 1 and 3 of the DriveRack360, the outputs feed the amps for the Monoliths. The sub output can feed the (I assume) powered sub via its LFE input (ideally an XLR input). So no need for 'sub amp' shown in this diagram that depicts two unpowered subs:

DBX360_ThreeWay.jpg


You can use your existing amp for the ESL panels, but will need to add an amp for the Monolith woofers, a cheap Pro amp will do just nicely, no need for bling there. A Crown XLS1002 is more than enough, Yamaha ProAudio amps are nice as well, IIRC, those use variable speed fans, so are silent in a home setting (no need for forced air).
Or if aesthetics are an issue, then an Emotiva BasX A2 amp (<$500) will do, as would any class A/B or class D ~200wpch stereo amp.

Also, is it possible that another DBX unit would better suit my needs, seeing that it is only a 2.1 home stereo set-up?
Since you need a minimum of 5 outputs, only the 360 supports that.
 
In a 2.1, you would be leveraging 5 of the 6 outputs, so a 'spare' for a tactile transducer, or a second sub (recommended to balance room modes).

So the output of the pre-amp would use RCA to XLR cables to feed inputs 1 and 3 of the DriveRack360, the outputs feed the amps for the Monoliths. The sub output can feed the (I assume) powered sub via its LFE input (ideally an XLR input). So no need for 'sub amp' shown in this diagram that depicts two unpowered subs:

View attachment 23010

You can use your existing amp for the ESL panels, but will need to add an amp for the Monolith woofers, a cheap Pro amp will do just nicely, no need for bling there. A Crown XLS1002 is more than enough, Yamaha ProAudio amps are nice as well, IIRC, those use variable speed fans, so are silent in a home setting (no need for forced air).
Or if aesthetics are an issue, then an Emotiva BasX A2 amp (<$500) will do, as would any class A/B or class D ~200wpch stereo amp.


Since you need a minimum of 5 outputs, only the 360 supports that.
Johnathan...I will probably pester you daily for the foreseeable future, due to the fact that I am rather uneducated regarding various equipment functions and how to incorporate them into my 2.1 home stereo system. Although the technology of the DBX is way beyond my comprehension, I trust that you'll guide me in the best direction in order to get the best results out of my system. You also pointed out that I will need to add/purchase a 2nd amplifier to handle the low/bass frequencies for the woofers. Let me describe my entire system to you so it can best help you to respond. I presently have a Black Ice Audio F35 Integrated Tube Amp, which is now powering the Monolith3's with their passive IIIP Crossovers. Momentarily, I will also own an Emerald Physics EP-600.2SE Class D Amp (rated @ 750 wpc @ 4 ohms) AND a Schiit Freya+ Preamp. My intention is to replace the Black Ice with the Emerald Physics Amp. However, since you clarified my need for a 2nd Amp if I should purchase the DBX and eliminate the passive crossovers... Do you think I could use the Black Ice (even though it is an Integrated Amp rated at 70 wpc @ 4 ohms) to power the low/bass frequencies of the Monolith's? If not, which of the relatively inexpensive amps that you mentioned/recommended earlier is your favorite and why? Rounding out my system is a Sony Turntable, Black Ice CD Transport/DAC, and a Polk Audio Powered Sub-Woofer (which has a variable response control from 60-120 Hz). As you already know, the current Monolith Crossovers are set for 125 Hz, although the previous owner modified the passive crossovers with a red jumper cable in order to allow the replacement GoldWood Sound woofers to reproduce higher mid-bass? frequencies. I am excited to read your response to all of this!!! Thanks!
 
Jonathan... I'll warn you ahead of time, but I am very uneducated regarding equipment function and how to incorporate the various units into my system. So I will probably pester you daily for a while!!! Thus far, I am understanding that you think very highly of this DBX unit. I appreciate that, but its' technology is way beyond my comprehension! I am very grateful for your guidance, so there's a good chance I'll take your advice and purchase one. Your responses also point out I will need a second amplifier to run the low or bass frequencies. Let me clarify my actual system for you, as you seem to be very knowledgeable regarding brands & models. I presently have a Black Ice Audio F35 Integrated Tube Amp, which is now powering the MonolithIII's with their passive IIIP Crossovers. Momentarily, I will have an Emerald Physics EP-600.2SE Class D Amp rated at 750 wpch @ 4 ohms AND a Schiit Freya + Preamp (with Tube option). My intention is to replace the Black Ice with the Emerald Physics amp. However, since you clarified my need for a 2nd amp if I utilize the DBX and eliminate the passive crossovers, do you think I could use the Black Ice (even though it is an Integrated amp) to power the low/bass frequencies of the Monolith? If not, which of the relatively inexpensive amps you suggested earlier, do you most like? Also, don't forget I have a Sony Turntable & a Black Ice CD Transport/DAC. My single powered subwoofer is a Polk Audio, which has a response knob from 60 - 120 Hz. And as you already know, the Monolith crossovers are set at 125 Hz. Finally let me state that the previous Monolith owner eliminated one of the connections with a red jumper cable in order to allow the GoldWood Sound replacement woofers to reproduce higher mid-bass? frequencies. I am highly anticipating your response to all of this information!
 
I presently have a Black Ice Audio F35 Integrated Tube Amp, which is now powering the Monolith3's with their passive IIIP Crossovers
Well, that right there is why the sound is not the best, as a tube amp and those woofers are not a good pairing, much less through a passive XO. And 70w is not enough for those panels, and worse due to losses in the XO.

But since you intend to switch to a more powerful amp, you should see better results with the EP driving the passive. But it's still a passive XO, not even the mighty Sanders ESL amp will make that sing.

Thanks for sharing further details about the gear, as that is key to understanding how various options will fit.

Both of your current front ends are integrated models, with pre-amp and amp in a single box, and neither seems to have a pre-out / amp-in loop, which is required to insert an active crossover. So the effort to go active is over unless you are willing to consider fully separate pre-amp / amp options.

Thus far, I am understanding that you think very highly of this DBX unit. I appreciate that, but its' technology is way beyond my comprehension!
Yes, the tech in this thing is pretty cool, but it's been around for two decades. It does depend heavily on the setup software to load and set configurations, so one needs to be comfortable using apps on the PC. And due to its nature as an auditorium-scale management system, it has concepts such as 'Venue' and finally gets down to devices and then presets for the devices. So a bit of unnecessary complexity to manage a single box, but it doesn't really get in the way too much. Then again, I've been in the computer software development space for 45+ years, so what I see as straightforward, may not be to others.
So if comfortable enough driving an app like that to load the pre-made configurations I can send you, the hard stuff will be done for you. The only configuration tweaks we might make are adjustments to input/output gains to match your gear, and the delay settings on the subwoofer output, again, to fit your physical setup.

But, I'll stop there and double-check that the whole active XO path is one you are willing to pursue, as it requires several things to achieve a successful outcome:
  1. Front-end is a pure pre-amp with line-level, volume-controlled outs (balanced preferably)
  2. Two amps, one for panels and one for woofers, matched to their respective roles (balanced ins)
  3. An electronic crossover, DSP-based preferably but could be a fixed analog active XO
  4. Crossover design that suits the Monolith (I can supply that for the DBX)
  5. Measurement system to validate settings and setup, REW software, and a UMIK1 microphone
Right now you have none of those (well, #4), so maybe a rethink of the overall project, as this is both complex and costly. But if willing to go all-in, the results can be impressive.

However, as I usually counsel here, your number one bang-for-the-buck improvement is going to be acoustical treatments of the room housing the ESL setup. And those large Monolith ESL panels need a LOT of room treatments to tame them. A full ton+ (literally) of room treatments in my dedicated room.

So maybe look at deploying the EP amp (since you have it) and look at improving the acoustics. A few hundred bucks there goes a long way.
 
All this reminds me of why a core value of the Monoray line is that all these complexities are completely abstracted and one could have a very nice 2.1 system with extremely high performance and is easy to deploy by normal humans.
That systems controller/amp even supports realistic tube amp emulation thanks to the closed-loop DDFA nature.

Further leveraging this closed-loop, DSP-enabled design, users may select from a list of ‘classic’ amplification models to achieve sonic signatures based on user preferences. Models from highly regarded tube designs achieve uncanny emulation thanks to the dynamic nature of the feedback and the DSP, thus the typical tube third-order harmonic distortion under load only appears when load would merit it.

Only a highly accurate, tightly coupled amplification and speaker system can offer this type of option, making DDPD unique in the world of audio

Too bad it only exists on paper at the moment.
 
Well, that right there is why the sound is not the best, as a tube amp and those woofers are not a good pairing, much less through a passive XO. And 70w is not enough for those panels, and worse due to losses in the XO.

But since you intend to switch to a more powerful amp, you should see better results with the EP driving the passive. But it's still a passive XO, not even the mighty Sanders ESL amp will make that sing.

Thanks for sharing further details about the gear, as that is key to understanding how various options will fit.

Both of your current front ends are integrated models, with pre-amp and amp in a single box, and neither seems to have a pre-out / amp-in loop, which is required to insert an active crossover. So the effort to go active is over unless you are willing to consider fully separate pre-amp / amp options.


Yes, the tech in this thing is pretty cool, but it's been around for two decades. It does depend heavily on the setup software to load and set configurations, so one needs to be comfortable using apps on the PC. And due to its nature as an auditorium-scale management system, it has concepts such as 'Venue' and finally gets down to devices and then presets for the devices. So a bit of unnecessary complexity to manage a single box, but it doesn't really get in the way too much. Then again, I've been in the computer software development space for 45+ years, so what I see as straightforward, may not be to others.
So if comfortable enough driving an app like that to load the pre-made configurations I can send you, the hard stuff will be done for you. The only configuration tweaks we might make are adjustments to input/output gains to match your gear, and the delay settings on the subwoofer output, again, to fit your physical setup.

But, I'll stop there and double-check that the whole active XO path is one you are willing to pursue, as it requires several things to achieve a successful outcome:
  1. Front-end is a pure pre-amp with line-level, volume-controlled outs (balanced preferably)
  2. Two amps, one for panels and one for woofers, matched to their respective roles (balanced ins)
  3. An electronic crossover, DSP-based preferably but could be a fixed analog active XO
  4. Crossover design that suits the Monolith (I can supply that for the DBX)
  5. Measurement system to validate settings and setup, REW software, and a UMIK1 microphone
Right now you have none of those (well, #4), so maybe a rethink of the overall project, as this is both complex and costly. But if willing to go all-in, the results can be impressive.

However, as I usually counsel here, your number one bang-for-the-buck improvement is going to be acoustical treatments of the room housing the ESL setup. And those large Monolith ESL panels need a LOT of room treatments to tame them. A full ton+ (literally) of room treatments in my dedicated room.

So maybe look at deploying the EP amp (since you have it) and look at improving the acoustics. A few hundred bucks there goes a long way.
I only have One current front end… the Black Ice F35 which is a true “ integrated “ amp. Shortly, I will also own the Emerald Physics amplifier (non-integrated) and the Schiit Freya+ (plus) which is a pre-amp only. So if I am not mistaken, wouldn’t I be able to use the Schiit as a single pre-amp for both amplifiers (the EP and another true amp, such as Emotiva BasX2)??? Therefore I would only be replacing the Black Ice with the Emotiva… and the passive xo with the DBX? If this is correct, then my investment should be around $1,500 for both units. Please confirm this to be true, or false…
 
Shortly, I will also own the Emerald Physics amplifier (non-integrated) and the Schiit Freya+ (plus) which is a pre-amp only.
Ah, OK, my bad, I glanced at the EP600 and somehow thought it was an integrated. Lack of coffee ...

and the Schiit Freya+ (plus) which is a pre-amp only. So if I am not mistaken, wouldn’t I be able to use the Schiit as a single pre-amp for both amplifiers (the EP and another true amp, such as Emotiva BasX2)???
Correct, and the good thing is the Schiit has balanced XLR outs, and both the EP600 and whatever else you get for the woofer amp can use balanced ins, making gain management simpler.

Therefore I would only be replacing the Black Ice with the Emotiva… and the passive xo with the DBX?
Correct, the passive is replaced by the DBX as the system XO.
The woofer amp should be one with XLR balanced inputs, so the BasX is out, maybe a Marantz MM8025 on the used market for $500 https://www.ebay.com/itm/185492653241?epid=4024807981&hash=item2b303944b9:g:vH0AAOSw6~Bix27Z
That one has balanced inputs and looks like a typical home audio amp.
 
Ah, OK, my bad, I glanced at the EP600 and somehow thought it was an integrated. Lack of coffee ...


Correct, and the good thing is the Schiit has balanced XLR outs, and both the EP600 and whatever else you get for the woofer amp can use balanced ins, making gain management simpler.


Correct, the passive is replaced by the DBX as the system XO.
The woofer amp should be one with XLR balanced inputs, so the BasX is out, maybe a Marantz MM8025 on the used market for $500 Marantz MM7025 2 Channel Power Amplifier 699927121556 | eBay
That one has balanced inputs and looks like a typical home audio amp.
Thank You... This brings me to another question: My system is a 2.1 Stereo with Powered Subwoofer. If I just simply want to eliminate the existing factory passive crossovers and use something different, but very simple & basic... could I use something like the DBX 234xs Stereo 2/3 Way, Mono 4 Way Crossover rather than the DriveRack Venu 360? I am realistically looking for something that isn't complicated or overly challenging in it's operation... something simple without relying on my computer or phone apps and feeling overwhelmed. Something that would appeal to a 63 year-old non-tech savvy individual? If this is possible... then once again I am looking to you for suggestions for a specific brand/model of such a XO (if something else works better than the DBX 234xs). Finally, I really don't want to have to add a 2nd Amplifier to power the low/bass/woofer portion of my Monolith's or bi-amp. Do you think I could still get some good, effective results from running each speaker with just the Emerald Physics Amplifier (for the ESL Panel & Woofer together) which is rated at 750 wpc into 4 ohms?
 
If I just simply want to eliminate the existing factory passive crossovers and use something different, but very simple & basic..

Sure, which is why I also mentioned you "... could get a fixed analog active XO ", as that Marchand can be specified as a 2.1 model with the following three-way configuration:

High Pass - 24dB octave L-R @ 330Hz with optional 1ms delay added for the panels
Band Pass - 24dB octave L-R @ 60 to 330Hz for the woofers
Low Pass - 24dB octave L-R @60Hz with bass summing (so the L/R signal is mixed for the .1 )

https://www.marchandelec.com/xm44-electronic-crossover.html
Finally, I really don't want to have to add a 2nd Amplifier to power the low/bass/woofer portion of my Monolith's or bi-amp.
Uhm, that's not how this works, sorry. An active crossover setup requires one amp per band being split, so a two-way requires two amp channels per speaker, a three-way requires three amp channels per speaker, etc.

If you only want to use one 2ch amplifier, then you are stuck using the factory passive.

Given the (understandable) reluctance to go for something complex, I stand by my suggestion to look at placement and room acoustics work first. It will bring a huge bang for the buck, especially with the big panels which can easily overpower a room.
 
Sure, which is why I also mentioned you "... could get a fixed analog active XO ", as that Marchand can be specified as a 2.1 model with the following three-way configuration:

High Pass - 24dB octave L-R @ 330Hz with optional 1ms delay added for the panels
Band Pass - 24dB octave L-R @ 60 to 330Hz for the woofers
Low Pass - 24dB octave L-R @60Hz with bass summing (so the L/R signal is mixed for the .1 )

https://www.marchandelec.com/xm44-electronic-crossover.html

Uhm, that's not how this works, sorry. An active crossover setup requires one amp per band being split, so a two-way requires two amp channels per speaker, a three-way requires three amp channels per speaker, etc.

If you only want to use one 2ch amplifier, then you are stuck using the factory passive.

Given the (understandable) reluctance to go for something complex, I stand by my suggestion to look at placement and room acoustics work first. It will bring a huge bang for the buck, especially with the big panels which can easily overpower a room.
I will definitely work on room placement and acoustics. But also asking if there’s anything that can be done to improve/modify the factory passive crossovers and your recommendations for new replacement woofers that will be as good or better than the original Eminence or GoldWood Sound woofers (which will be used with the original xo’s)??? Thanks!
 
I will definitely work on room placement and acoustics. But also asking if there’s anything that can be done to improve/modify the factory passive crossovers and your recommendations for new replacement woofers that will be as good or better than the original Eminence or GoldWood Sound woofers (which will be used with the original xo’s)??? Thanks!
 
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