[jonbee]

Over the last dozen years or so of my 47 years in this hobby I've owned over 30 "premium" stand mounted speakers retailing for > $1500/pr., plus assorted floor standers and cheaper standmounts.
 Among them PSB Platinum M2, Volent Paragon VL-2, VMPS 626R, Totem Model 1 Signature, Thiel PCS, Talon Khite, Spendor LS3/5a, Silverline SR11, Sequerra Met 7.7 mk V, Selah Tempesta, Selah SSR, Selah RAAL/revelator monitor, Revel M20, Paradigm Active 20, Paradigm ref 40, Onix Ref 1 MK 2 ninja, Nohr 9.0 Mini w/ dennis murphy xover, Morel Renaissance, Monitor audio GR10, merlin tsm-m and MME, Joseph audio RM7si mkii, GMA Rio, Event Opal studio monitor, Escalante Juniper, Buggtussel Cingulate, Aerial Acoustics 5, ACI Sapphire III, AAD silver 1,  AAD 2001, and Paragon Jubilee.
In terms of overall quality in my rooms and by my taste, Selah Tempesta, Volent VL-2, Selah "mini-Verita" Scanspeak/RAAL monitors, Event Opal, Selah SSR, Merlin TSM-MME, Buggtusel Cingulate, AAD silver, AAD 2001 and Revel M20 were in my top 10, in roughly that order of preference.
The Revel M20, which I owned about 13 yeas ago, was one of only 5 of these (Tempesta, Volent, Opal, Cingulate and M20) that had enough deep, powerful bass to sound balanced in my lossy living room system without a sub. They are very neutral and offer a fast, dynamic, transparent, wide range soundstage. They are very well built and measure about as well as any speaker out there.
http://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements
http://www.soundstagemagazine.com/measurements/revel_performa_m20/
Stereophile ranked them class A, IIRC. I liked them quite a lot, but I did feel the tweeter didn't integrate fully with the woofer, despite virtually perfect measurements. I could always hear the tweeter as a separate driver, and it had a bit of metal dome sound.
About a dozen years ago I bought a pair of Thiel 3.6s, which besides being much larger were better integrated and had better soundstaging. They also had a metal dome, but it was better behaved and integrated. I sold the M20s, but have fond memories of them.
I had read an AC posting about modding a pair of F30s, Revel's floorstanding counterpart to the M20, which I have also owned (and didn't like as well overall, feeling that there was a lower midrange  integration issue). Perhaps if I had modded my pair I would have liked them better.
http://www.audiocircle.com/index.php?topic=46327.msg415105#msg415105
Crossover parts and cabinet damping upgrades such as are described there are something I've done a lot, so I thought I might see if the M20 could be similarly improved. Now days the used prices of M20s has dropped to a level below that of other competitive speakers, and I consider them a bargain, so they would seem to be a promising candidate for a project.
I bought a near mint pair recently to kick it off:

 I decided to keep it simple- I lined the cabinet with No-Rez damping sheets, removed a third of the stock fiberglass stuffing, and replaced the generic looking film tweeter caps with Sonicaps, bypassing the larger of the two with Sonicap Gen 2. The woofer circuit uses large electrolytic shunt caps; for now I decided to leave them alone. Wiring is large guage and looks like ok quality, so I decided to leave that alone as well.
I've run them for ~20 hours, probably not enough to fully burn in the caps, but the overall sound is probably stable.
First off, these mods have not changed the overall nature of the sound, but have increased the overall focus from top to bottom in a pretty notable way. The lower midrange is much clearer and more focused and the bass is tighter and better focused as well without losing the great extension that is so special.
The top end is also similarly improved- it is smoother, grain-free and more finely detailed, and it now integrates better with the woofer than it did before. The metal dome signature is pretty much gone too, and I don't hear it separately from the woofer nearly as much as I had before the mods.
So an already good speaker is very nicely improved, essentially transformed, but there is still an asterisk here. While the top end is notably cleaner and clearer, it still has a signature, in that the tonality still sounds tipped up a bit. The clearest example is listening to Joshua Bell in the Red Violin. Compared to my Daedalus speakers (Eton soft dome) or my Selah stand mounts (RAAL ribbon), the violin, while squeaky clean and clear, seems to favor the upper harmonics over the lower body tone by just a bit, making the violin sound a little thinner and smaller. The effect is to make the overall sound a little cooler. Not huge, and not a show stopper for me, but it does define some of the sonic nature of the speaker.
So- here's my verdict. For the price of the speakers ($500-800 depending on condition) plus about $150 for parts, you get a very fine, nearly full range standmount that is very fast and clean, with excellent transparency and a large soundstage. It is built properly, with quality drivers, a state of the art conventional crossover design and a solidly built cabinet. Often ignored elements like mounting hardware, connectors and switches are executed very well, making them quite easy to work on. They are very flexible in use, having enough bass to supplant small floorstanders in medium sized rooms, yet able to be used against the wall or in a cabinet at the flip of a switch.
For me, they have cracked my top 5 list, moving ahead of the Event Opals, which have a trace of metal dome emphasis and a tad less clarity in the lower mids, and they are knocking on the door of the Volent VL-2 in overall quality, trading some of the VL-2s fine detail and soundstage depth for superior balance. While still not up to my Daedalus DA-RMA v2s (which favor the mids and "power" range), principally in richness of tonality and soundstage dimensionality, I could live with them permanently in my main system now.
The only caveat is that one should prefer or at least tolerate a squeaky clean presentation and a slightly cool, dry overall sound that showcases the upper range, and use appropriately matched front end and cabling. I've done that and I think they are great speakers for my bedroom system (the position matching selector on the rear works very well for small rooms and close wall placement).
I consider the simple mods I performed successfully got the lowest hanging fruit. I suspect replacing the  woofer 'lytics, wiring, using better replacement caps and resistors should extract even more from these chestnuts, for much more effort and 2x+ the parts cost.
So- if you have a pair of M20s, in my opinion this is a pretty easy, inexpensive and worthwhile upgrade. If you're looking for a very good smallish speaker for under a grand and are a little bit handy, this might be a very good option for you.
Over the years many speakers have been put up as "giant killers", sub $1000 speakers that play with the high priced options.
Spending the weekend listening to these in all 3 of my systems leads me to believe this is truly one of them.  I didn't consider the M20 to be Class A in their original form, but I think they are with these simple mods.
I don't know of any under $1k stand mount speaker that will outperform it overall, new or used, and Revel builds their speakers to last a long time, so a majority of their useful lifetime is still ahead in most cases.
The M20 is one speaker entering its "golden years" that truly deserves a new lease on life.

[jonbee]

Notes on the job:
It is best to remove the woofer by removing the back panel (a good strong tug on the speaker terminals will do it once the screws are removed) and using a long tool to push the woofer out from behind. Just be sure you are pushing on the magnet structure.
The existing caps have small diameter leads, and the circuit board is drilled for them. Many better caps have larger leads, as do the Sonicaps.  I had to drill out the holes in the board to 1/16th to fit the new leads.
Separate circuit boards for woofer and tweeter- tweeter board on right side wall held in by 3 screws.
Parts:
One sheet of 24x27 No-rez from GR Reseach. I've found No-Rez is easier to work with if cut 1/4" smaller than the  cabinet panel measurements.
2 ea. 15 mf Sonicap Gen 1,
2 ea. .15 mf sonicap Gen 2 as bypasses for above to replace 15.2 mf stock cap
2 ea. 7 mf Sonicap Gen 1 to replace 7.3 mf original. I had planned to bypass it with a Gen 2 to increase the size, but after I heard it without I liked it and left it alone.
For those interested in the woofer caps- there are 3 electrolytics- 18.6, 21.9 and 100mf. Film caps this big are physically quite large, so squeezing them into the boards is much more effort than the tweeter caps, and will also require drilling out the lead holes and probably extra holes for zip ties to secure the biggest caps. I'll probably replace them next weekend with Axon True Caps, mediocre but cheap for large sizes.
About 4 hours work overall. A pretty easy speaker to work on. No issues except those noted.

[Ric Schultz]

Jon,
Felt the whole front of the speaker (black part or at least around the tweeter) and cut off the phase guide on the tweeter.  Way less bright, focused and clear.

[rollo]

Jon,
Felt the whole front of the speaker (black part or at least around the tweeter) and cut off the phase guide on the tweeter.  Way less bright, focused and clear.

    Excellent suggestion. Do it.


charles

[jonbee]

Jon,
Felt the whole front of the speaker (black part or at least around the tweeter) and cut off the phase guide on the tweeter.  Way less bright, focused and clear.

I'll give the felt a try. The phase guide is another matter. Those domes are very delicate, and it seems there are dangers and small fingers around every corner!

[Redefy Audio]

Jon,
Felt the whole front of the speaker (black part or at least around the tweeter) and cut off the phase guide on the tweeter.  Way less bright, focused and clear.

what caused the brightness? the stereophile measurements didnt suggest that at all. except the ringing at 20khz, which it won't be remedied by removing the guide.

http://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements-part-2

[jonbee]

what caused the brightness? the stereophile measurements didnt suggest that at all. except the ringing at 20khz, which it won't be remedied by removing the guide.

http://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements-part-2

Measurements don't tell the whole story, obviously. Most of the brightness went away with these upgrades, with just a trace remaining. Atkinson noted that he also felt there was a discontinuity between woofer and tweeter, although it doesn't show in the measurements. I think the psychoacoustic effect of the mismatch in tonality is manifest as brightness in this case. Tightening the focus on the lows and midrange by absorbing more of the rear wave using the No-rez, and smoothing the tweeter with the improved cap allows them to blend better, which the ear/brain "likes" better. That's how I hear it, anyway.
In any case, I'm very pleased with the outcome.

[Redefy Audio]

Measurements don't tell the whole story, obviously. Most of the brightness went away with these upgrades, with just a trace remaining. Atkinson noted that he also felt there was a discontinuity between woofer and tweeter, although it doesn't show in the measurements. I think the psychoacoustic effect of the mismatch in tonality is manifest as brightness in this case. Tightening the focus on the lows and midrange by absorbing more of the rear wave using the No-rez, and smoothing the tweeter with the improved cap allows them to blend better, which the ear/brain "likes" better. That's how I hear it, anyway.
In any case, I'm very pleased with the outcome.

I can relate to what you mean for that the measurements don't tell all. the Revel M20 is one of the most impressive stand mount speakers i heard, although it was many years ago, that impression stays with me.

I didn't find them bright at all (adjusted the selector to taste of course).

One thing that the stereophile's didn't have is the phase response related to the freq response, which may or may not explain the discontinuity that you heard.

But anyway, it is always beneficial to treat the cabinets (although it is pretty good to begin with) 

[jonbee]

I thought I would update this. I replaced the 3 Ely woofer electrolytics with Axon True caps (same as Solen fast caps), bought on discount from parts connexion. Cost was ~$70 shipped. I also removed another of the original 3 sheets of fiberglass stuffing bats, now using only one.
I found only the 47 mf I doubled up with a 6 mf to replace the 100mf required drilling out the crossover board holes.
However, these large film caps were a bit of a challenge to mount because of space limitations. It might be better to use 33mfx3 or smaller for the 100mf, 16 + 6 for the 21.9 mf.
Otherwise it went pretty fast. If done along with the tweeter xover it adds another hour or so to the job.
Sonically, I think the woofer range is now better focused, with better soundstage depth and ambience presentation. Not as big a difference as with the tweeter caps and cabinet damping mods, but worth it to me.
After I did this, I added felt tweeter rings, 3.5 in diameter, 1.5 inch inner diameter. It did reduce the top end a bit, and improved the top end focus some, too. No downside I can hear. A worthwhile and very cheap tweak.
The sound is quite remarkable. Strikingly clear, dynamic and open from top to bottom, with superb, tightly focused bass and a wonderful soundstage. Not a trace of extra warmth or romanticism, though, and a top end range that is still favored in the mix a bit. I've been comparing them to my Hifiman HE-500 phones and they are very close. A true moniter, IMO.
Compared to my beloved Daedalus DA-RMA v2 (new price ~$10k), the DA-RMas have a fuller, harmonically richer sound and somewhat clearer rendering of ambience and spatial information. The top end has similar detail but is less prominent; if anything a bit on the reserved side. Cabernet vs. vodka, maybe? I prefer the Daedalus, but could happily live with the Revel.
One might consider something like Jupiter oil caps for the tweeters to soften their sound if desired, perhaps. As always, they won't be everyman's cup of tea, but for my taste I'm mighty pleased for my $1100 outlay (including stands and grills). Not "perfect" (I've never owned a perfect speaker), but the best overall sound for the $ I've ever had, for sure.

[wushuliu]

Sonicaps are a great bargain but they do have a thinner presentation IMO. For a little warmer upper midrange/treble good affordable options are ClarityCap ESA or Audyn Cap Plus.

[jonbee]

Sonicaps are a great bargain but they do have a thinner presentation IMO. For a little warmer upper midrange/treble good affordable options are ClarityCap ESA or Audyn Cap Plus.

I agree there are probably better choices. I wanted to start out with a good but cheaper option and see what I would get. Now that I'm satisfied that it is a worthwhile project I may roll a few caps in the tweeter slots. A slightly warmer, more organic signature on top would be a perfect tweak for the sound.
Anyone else have suggestions for other tweeter caps with a warmer signature that are not ridiculously $$$$?

[neep]

Jon,
Felt the whole front of the speaker (black part or at least around the tweeter) and cut off the phase guide on the tweeter.  Way less bright, focused and clear.

I thought this was an interesting comment. Just picked up the Revel M20's and they certainly are fatiguing after a long listen - even with the tweeter attenuation all the way down.

If cutting off the phase guide is a quick fix, I'd do it in a heartbeat but I'd love more confirmation that this is a good idea first. Any thoughts guys?

[jonbee]

I thought this was an interesting comment. Just picked up the Revel M20's and they certainly are fatiguing after a long listen - even with the tweeter attenuation all the way down.

If cutting off the phase guide is a quick fix, I'd do it in a heartbeat but I'd love more confirmation that this is a good idea first. Any thoughts guys?

I felt the same way about the stock M20s.
I haven't removed the phase guide out of fear of damage to the exposed tweeters, but the cap upgrade and the felt rings did really clean up the top end a lot. I'd say that at least 80% of the top end "zing" is gone, leaving it to be a well balanced speaker now. I used Sonicaps for the tweeters, but there are "softer" sounding caps as mentioned above that would take it further. Just replacing the tweeter caps and adding some extra cabinet damping is quite easy, and really brings these up in listenability.

[timind]

This thread could use some pics!!!
I have a pair of M20s that are in service about 50-50 with my Meadowlark Kestrels. The Kestrels aren't anywhere near as accurate as the Revels but still sound wonderfully warm and full.
I run the M20s with the tweeter level control down i notch. What really tamed the highs for me was finding the right position. And that was reducing the toe-in almost completely. The problem I had was more of a harshness on female vocals if sitting dead center. Moving my head 3-4 inches either side of center cleared this up. Removing most of the toe-in I had fixed this problem for me.
I read this thread a couple months ago and am going to read it again as I may try the cap swap. As I said thiugh, if you (Jonbee) took any pics during the process, I'd love to see them.

[jonbee]

This thread could use some pics!!!

Sorry, I don't have any, but the work is pretty simple. The only difficult part is popping the woofer out, as the gasket holds it tight. I removed the back plate from the speaker first, then pushed the woofer out from behind by tapping on the magnet with the handle of a hammer.
Once the woofer is out, you'll see the tweeter crossover on the right sidewall, woofer left. You don't need to touch the woofer crossover if you don't plan to upgrade those caps. I didn't find it to be a big improvement. There are 2 or 3 phillips head screws that hold the xover boards in place. Remove them with a short screwdriver and the boards come out easily. The leads are long enough that you can do all the work without de-soldering them. The tweeter caps are 2 film types, yellow in color. I've listed the values above, or you can check yours. The bang for the buck in this project comes from replacing the 2 tweeter caps and installing cabinet damping material. This or similar is good and cheap:
https://www.parts-express.com/sonic-barrier-1-acoustic-sound-damping-foam-with-psa-18-x-24--260-525
Remove 2/3 of the  fiberglass stuffing around the woofer area if you add the damping.
This only involves a little soldering, unless the new cap leads are too thick to go through the PC board holes. Then you'll need to drill them out a little. I used a 1/16" drill bit.
Lately I've been enjoying a pair of speakers with an aluminum tweeter and ClarityCap ESA caps. Not too expensive, and they sound very nice.
If you pull the woofer out, it all will look pretty obvious. These are easy speakers to work on.
For under $100 you can really improve these, particularly the top end quality and midrange definition.

[kenreau]

Cool project upgrade.  Thanks for sharing this and the updates.  I'll keep this in mind for a future project.

Kenreau

[timind]

Thanks for the link Jonbee. I think I'll order some of the foam.
I had the back off one of my M20s a while ago when one of the binding posts needed tightening. It did take a pretty good tug.
Might try the foam first and crossover after assessing the change.
I just made a minor change to the Kestrel crossover by changing the resistor inline with the tweeter. The Kestrels lack a bit of top end energy so I removed the 6 ohm resistor and inserting a 3 ohm resistor. This was too much of a change but it was the only resistor on hand. I ordered 5 ohm resistors and installed them. I believe this one ohm change was all they needed. Have only put a few hours listening on them, but sounds promising.

[Bryson69]

Hi Jonbee, I’m a new member and I have 2 pairs of m20 need to upgrade but I’m not that much of a DIY kinda guy. So do you do this on the side? I willingly to pay for all the parts, labor and shipping. thank you in advance

[jonbee]

Hi Jonbee, I’m a new member and I have 2 pairs of m20 need to upgrade but I’m not that much of a DIY kinda guy. So do you do this on the side? I willingly to pay for all the parts, labor and shipping. thank you in advance

In days past I might have done it, but no more. That said, it is not that difficult, and i'd be happy to walk you through it.
PM me if you wish.

[Bryson69]

Thank you for your responded Jon. I’m new here and it’s doesnt allow me to PM .