ML Monolith III and damaged woofer

Hello DIY folks there!

I have couple of questions regarding my pair of MartinLogan Monolith III.

Unfortunately original woofer elements have got physical damage (children and pencil), so I need to replace those. I did research and found at least Peerless 830669 and HiVi W12 has been used as a replacement, but that was 2006.

1) I wonder what might be best replacement at todays market? Perhaps Peerless XXLS?


2) When woofer level is less than original, should I change resistors (I assume R1 (2k 50W) and R4 (50k 50W) while speaker box is open, or does is make difference if I put extra serial+parallel resistor at ESL input (after passive crossover box)? What is resistance of ESL for calculating new resistors?

Haven’t open box yet, so I took above values form this diagram:
http://www.martinloganowners.com/forum/attachment.php?attachmentid=16533&d=1378884467


3) Is there a way to tweak “music sense” sensitivity (or bypass it all together)?
While woofers were ok, often happened that my listening level was so low that music sense shutdown power on ESL.

Cheers,
-jla

Too bad about the damage, but the original factory woofers were probably due for replacement anyway given the age of the speaker. Plus, I do not have a high opinion of the original driver, it was nothing to write home about. And the factory passive crossover was not great either. I see from your introduction posting you also Have the Exos active crossover, which is excellent, as any active will be miles ahead of that passive.

To answer your questions:

#1 - No, do use 'subwoofer' drivers for this application, you are not interested in bottom octave performance, that should fall to an external sub that can be correctly placed and adjusted to the room. The XXLS is a sub driver with limited mid-range and a heavy cone.
The most critical band to pay attention to is the 60Hz to 700Hz range, as that's where the crossover to the panel lies, and having a driver that has clean performance up to 1Khz is important, as the factory crossover slopes are only second order (IIRC). So you want a driver with a nice low Mms and good specs in the mid-bass. This means that realistically, it will start to roll off below 60Hz, which is fine as long as you remove the low-frequencies and redirect those to a sub.
Also, by removing the need to deliver low-bass from this driver, you allow it play cleaner in the mid-bass, and that makes a world of difference once you start playing louder.

So I looked around and guess what, I would still recommend the Peerless 830699 https://www.madisoundspeakerstore.c...rless-sls-830669-12-woofer-coated-paper-cone/ . There might be some alternatives you can source in Europe, but the specs would need to be similar (light cone, good mid-bass performance).

#2 – I would not change anything past the step-up transformer. Since the passive is external anyway, I’d pad the positive line for woofer or ESL as needed to balance gain. As for values, I’d replace the woofer, then measure. So if the new woofer is 3dB louder than before, then calculate how much resistance is required to drop the output by 3dB (DIYaudio.com has tons of threads on doing this).
But this is why I love active crossovers, it should be a simple matter of adjusting gains on the xover or the amps and you’d be done.

The ultimate is to get a speaker processor and adjust delay as well as pick better crossover points and slopes. But that requires a good speaker measurement rig and knowledge how to use it.

#3 – Sorry, not sure how one would tweak that. Maybe one of the EE’s will chime in.

You should abandon those passive crossover boxes and use an active crossover as JonFo recommended before making any other alterations because it will be a tremendous improvement.

1. I would have both woofers reconditioned as the specification are hard to equal.
   
   Here are the parameters for the Monolith-III woofer part number 121515:
   
   Power Handling (RMS) 150 Watts
   Power Handling (max) 250 Watts
   Impedance 4 ohms
   Frequency Response 20 to 500 Hz
   Sensitivity 89.1 dB 1W/1m
   Voice Coil Diameter 2"
   
   THIELE-SMALL PARAMETERS
   Resonant Frequency (Fs) 19.25 Hz
   DC Resistance (Re) 3.51 ohms
   Voice Coil Inductance (Le) 1.00 mH
   Mechanical Q (Qms) 3.34
   Electromagnetic Q (Qes) 0.49
   Total Q (Qts) 0.42
   Compliance Equivalent Volume (Vas) 12.701 ft.³
   Mechanical Compliance of Suspension (Cms) 0.9036 mm/N
   BL Product (BL) 8.12 Tm
   Diaphragm Mass Inc. Airload (Mms) 75.6g
   Maximum Linear Excursion (Xmax) 10.0 mm
   Surface Area of Cone (Sd) 532.36 cm²
   
   
2. Those resistors after the transformer should not be changed as the R1 2K-ohm is for secondary leakage inductance and the R4 50K-ohm is for secondary magnetic inductance. They can be moved to the primary side but the values would need to be lowered by the transformers step up ratio squared. The R1 2K-ohm resistor would need to be lowered to a 0.8-ohm Rdamp in series on the primary side and the R4 50K-ohm resistor would need to be lowered to a 20-ohm Rshunt parallel with the primary terminals.
   
   
   
3. If your music sense circuit is turning off at low volume levels maybe your amplifier needs to be upgraded? The triac can be jumped which activates the ground circuit on the high voltage multiplier but this is not recommended because you'll need to use a switched power source for the bias boards.

Thanks guys for responses! I have integrated amplifier ASR Emitter II Exclusive, which has not pre_out-main_in connectors. It has sub-out which I could possibly have active crossover (for example Exos which I have) for either low or high pass and then second pair of amplifier. Not sure if this answer anyway, as I suspect that active crossover would cause delay and if the other line is using passive crossover without delay.. But I'm not what I'm seeking for more electronics at the moment. So with my current amp, active crossover is really not answer.

I may seek repair for Eminence woofer elements. Though I may try Peerless option.. Thanks for original woofer specs, that will help for comparing alternative parts.
It came clear to me that I don't touch internal parts in ESL line

Do you have schema around Music Sense circuit?

Cheers,
-jla

Hi, haven't been here for a while.
As to the Monolith 3 woofer, I tracked down the Eminence spec sheet for it, as it was made especially for ML.
here it is.
I didn't like them much (one note bass), I much much prefer the ACI SV12's I replaced them with (attached below PDF), plus a few mods to make them work right in that box, and now active, and I use the third order sealed as well, super low, tight, punchy and fast and blends perfectly with the speed of the esl panels.

Cheers George