Page 1 of 4 123 ... LastLast
Results 1 to 15 of 50

Thread: Monolith refresh - Panels, woofers and rail stain updates

  1. #1
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Monolith refresh - Panels, woofers and rail stain updates

    Iíve had Monolith IIIís for eight years now, having bought them used in Ď98. They were made in January of Ď93.

    They sat unused for more than a year as I finished up the custom home theater room designed around them and the rest of Martin Logan gear I have.

    Once in full deployment in the new HT, they were marvelous, although running on their factory passive crossover for the first months. After playing with placement, tuning the room acoustics and all other non-invasive approaches, it was clear that a better sound should be possible with these great speakers. So I went with an active external crossover and bi-amped. Big improvement.

    However, in measuring the new x-over setup, it was clear something was not right in the bass, especially the mid-bass. Keep in mind Iíve always used subs (back in those days it was two Velodyne ULD-18ís) so the Monolith woofers were not being taxed by ultra-low frequencies. The x-over then was at 60hz.

    Looking at the stock 12Ē driver, it was clear the distortions and Ďflabbinessí I was hearing were a product of one tired speaker. So I updated the driver with an ACI SV12 unit. Read the specific story and see pics of that one at my site.
    The sound, especially the 100hz region was vastly improved. Been very happy with them as long as the x-over is below 160hz.

    Having experienced dramatic improvements from the active x-over, I then went all-out with a Speaker processor, the DriveRack 260. This allowed true panel to woofer (and to sub) integration on a level that seemed a pipe-dream before. This unit is awesome, and results are likewise.

    Now, here we are in the spring of 2006 and the panels have significant high-end frequency drop offs, the ETF measurements also show some panel resonances that I donít think had been there before. Also, the original panels are now 13 years old. Time for a refresh of the panels.

    The Monoliths I bought (since I got them used) came with Oak rails. They look nice, but donít really go that well with my HT setup, where everything is either black, grey or uses purple for a highlight color. When using front projection, light control and reflections are critical. The light Oak rails pick up the light of the PJ and are somewhat noticeable when playing a movie. Since the replacement of the panels requires some disassembly of the Monolith, Iíll be removing the rails and refinishing them.

    The plan is to use an Aniline dye to stain them a dark purple and then put a satin finish poly coat over that.
    First, lotís of sanding to get down to the bare wood.

    In addition to the panels and rails, Iíll also be doing something with the woofer, but thatís detailed in another post.

    Some of you have PMíd me or posted asking for details on Ďhow-toí perform some or all of the above, so this thread is for you guys. Pics, measurements, descriptions and crying on your shoulders if I screw-up, all to come in the next few days.

    Lotís of work in the next day or two
    Last edited by JonFo; 04-30-2006 at 01:00 PM.
     
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  2. #2
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Woofer Update selection

    Since the woofer project a few years ago, Iíve been doing two things, one is testing higher crossover points to move out of the dipole rear-wave cancellation issue area, and the other is researching drivers that can play cleanly at up to 500hz. Turns out there are a couple of suitable drivers, one is a Peerless brand unit, the other is an AudioTechnology Flexunits model.

    The Flexunits seems like a good choice if you do not use a sub, as it has better LF response and a better motor. However, itís more expensive and does not quite go as high as the Peerless, but definitely goes high enough for the factory x-over points or even higher.

    I settled on the Peerless 830669 12Ē driver. This unit will play clean past 1KHz, and bass was reasonable considering Iíll be crossing over at 24db/oct at 80Hz. It is not suitable for a full-range Monolith, as itís low-end extension is limited. But for my purposes, seems like a good choice. Proof will be in the measurements.

    As seen the pic below, the woofers and panels are here.
    The other stuff is for my little center channel project
    Attached Images Attached Images  
    Last edited by JonFo; 04-30-2006 at 01:01 PM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  3. #3
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default As-is measurements of ACI SV-12

    Before we go moving and ripping anything up, I captured some Ďas-isí measurements of the current ACI woofer.

    This graph shows both the detailed Bode response (blue line) and the smoothed third octave response (green line) as measured at 1m distance

    As you can see, the smoothed response is reasonable, being +/-3db from 35 to 435Hz. It falls off pretty rapidly after that. In the Bode response, the distortion elements at >250Hz start accumulating. The cone is pretty massive and does not do mid-bass that well.
    The big peak at 64hz is a room mode. I donít have anechoic chamber, so we live with spikes here and there

    I expect the peerless to go higher and smoother.

    More to comeÖ
    Attached Images Attached Images  
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  4. #4
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Back on track

    Well, after a few weeks of hard work, first on the SL3-XC center channel project , and then some catch-up at work, I finally had time to get back to the Monoliths.

    The plan to deal with the trim rail is a bust. Hereís why:

    The monolith is constructed of essentially three parts:
    1. The Bass cabinet, which houses the 12" driver and the ESL Electronics (but no Crossover, Monolith x-over have always been external, with a choice of passive or active)
    2. The ESL frame. This is what holds the panel and the trim elements.
    3. The Rails that tie the two together.

    The rails are a part of the support structure and require some major bolts and screws to be removed. And I didnít feel like a total disassembly project. So the rails will remain Oak, and their light color nature will be dealt with differently. Iíll post about that when I get around to solving that issue.

    In the meantime, I had the new panels and the Peerlesss drivers to install.

    So, doing one each weekend, Iíve updated the panels and woofers.

    The speakers were repositioned and measurements taken.
    Last edited by JonFo; 05-21-2006 at 08:23 PM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  5. #5
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Woofer Update

    As noted above, the ACI woofer as big improvement over the tired-out factory Eminence unit.
    However, the ACI SV12 is really more of low bass /sub driver, which means it canít go cleanly up into the mid-bass. Not too big a problem if you stick to the 125hz factory crossover point.
    But as many threads have discussed, dipole speakers, no matter how big the panels, have issues with rear wave cancellation at low frequencies. Physics gets in the way it seems.
    Therefore I like to cross-over around 312Hz to the Monolith panels.

    To better match the higher crossover point (and use of 18db/octave slopes), I needed a speaker that would be clean up in the 800Hz range.
    The Peerless also does not go down very far, its FS3 is 40hz. So it needs to be crossed over to the sub above 65Hz. In my application, Iím using 80hz.

    As can be seen in this graph of frequency response, the old ACI and the Peerless are roughly equivalent in the 100 to 450 range. The ACI clearly is more of low-end driver, easily posting 3 or more DB better numbers down low.
    But the Peerless goes substantially higher (and as weíll see in the impulse graphs, cleaner) and is essentially flat at 800Hz. The graph does not show it because of the floor bounce (notice how both curves track it). I really need an anechoic chamber

    Measured from different distances (with different room modes affecting), itís clear the Peerless is better at the mid-bass.
    Attached Images Attached Images  
    Last edited by JonFo; 05-21-2006 at 08:26 PM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  6. #6
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Impulse response

    The real difference is in the distortion products of these two drivers. The larger mass of the ACI will get in the way of clean mid-bass transients. This Impulse response shows us that the ACI can start and stop its initial impulse fairly well, but then the cone oscillates substantially more than the Peerless unit. The Peerless has a lighter mass cone, and less compliant surround, which is why it does better up in the mid-bass.

    The Blue trace is the ACI, the Green trace is the Peerless.
    Attached Images Attached Images  
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  7. #7
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Pulling the old speaker

    Here is a shot of the ACI pulled out. You can see the ESL electronics in the cavity.

    Note the bolts screwed into the driver. Thatís a little trick to pry out drivers without marring the surrounding box. They allow for leverage to be applied (crowbar or claw hammer) in an upwards fashion to loosen the driver from its seal.
    Otherwise, you ainít getting those out of there by hand, I can tell you that
    Attached Images Attached Images  
    Last edited by JonFo; 05-21-2006 at 10:29 AM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  8. #8
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Putting in the new

    Here is a shot of the new Peerless going in.

    Since I didnít think that fully reflective set of electronics and back panel was quite right acoustically for a driver playing up into the mid-bass, I put a Deflex panel to hang over the electronics and absorb / deflect the mid-bass and hopefully reduce resonances.

    Also, the Peerless basket holes do not align perfectly, so a bit of reaming of the metal was required.

    Otherwise, itís a drop-in replacement.
    Attached Images Attached Images  
    Last edited by JonFo; 05-21-2006 at 08:28 PM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  9. #9
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Panel Updates - removal

    Updating the panels is a bit daunting. First, the Monolith is a big puppy, weighing in at over 120 pounds per unit, you donít just grab these, you need two people to safely move them about.

    Also, since they are not square sided, they do not lie on their sides, they will rock onto their backs if not held.

    So step one is to enlist a Ďvolunteerí to help here. My six foot tall gorgeous French wife, who can easily lift 100 pound bags was kind enough to Ďvolunteerí to help

    The instructions for the panels are easy to follow, and I really have no additions or corrections to them other than the color commentary here.

    First, we pull off all the trim and that allows the access to the frames where the panels are seated. Below is a shot of the speaker on its side, with the panel already removed.
    You can see the frame slots the panels fit into.

    The process of pushing the panel centers out from the middle (from behind) is pretty straight-forward. The panel flexes pretty easily (with the right amount of pressure) and one of the edges will pop out of its frame, making the rest of the removal a simple process of pulling the panel up and out of the other frame element.
    Attached Images Attached Images  
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  10. #10
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Panel Updates Ė Install

    The installation process is a bit more involved, as sliding in the panel has to be done just so. The first detail is the ESL drive pigtail cable. It goes into a slot at the bottom of the left rail(as seen from behind) and is a tight fit. Then the rest of that side of the panel is fitted to its frame rail from the front. We then have to bend the new panel to slot it into the other frame slot.
    Again, this is a bit difficult to get over the fact that you have literally bend the new ESL panel a good bit to get it in. But in it goes, no worse for wear. Just make sure you treat the foam edging on the panels very carefully and donít rip it or get the tape off of it.

    Once it pops in, remember to hook up the pigtail to a socket in the top of the woofer section (see pic below) and youíre done and can start reassembling the trim.
    Attached Images Attached Images  
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  11. #11
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default All done

    Once the trim is back on, we repositioned the speaker and are good to go!

    Hereís a shot of the Monolith with the new panel and woofer. The ESL is much more reflective than the old panel was, with a nice Ďchromeí metallic sheen. A combination of both the new vapor depositing process ML has, which leaves a consistent and thicker coating (for increased efficiency) of metal on the surface, and the fact that the old panels had accumulated dust and other particles that had bonded to the Mylar.
    Attached Images Attached Images  
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  12. #12
    Junior Member
    Join Date
    Mar 2005
    Posts
    27

    Default

    Here is a shot of the ACI pulled out. You can see the ESL electronics in the cavity.

    Note the bolts screwed into the driver. Thatís a little trick to pry out drivers without marring the surrounding box. They allow for leverage to be applied (crowbar or claw hammer) in un upwards fashion to loosen the driver from itís seal.
    Otherwise, you ainít getting those out of there by hand, I can tell you that.

    Hi I don't fully understand the implications of this post Since I have had difficulty getting my loctited screws out of the panels I'm sure this post has some relevance for me.
    What do you mean by bolts screwed into the driver? Did you pry loose the driver with a crowbar without trying to loosen the screws thereby ripping out the female metal sleeve receiver within the wood? Or does it mean something else?

  13. #13
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default Listening impressions

    A quick tweak of the DriveRack settings and some initial listening test show that the new panel and woofer are indeed sounding better than the old set.
    However, much measuring and tweaking to go.

    Initially, the panel is very bright, not only is the efficiency a couple of DB better than the old, but as weíll see in the measurements a bit later, the midrange has a serious rise in it.

    But once the levels between panel, woofer and sub were tweaked, it was much better, still a noticeable Ďpresenceí in the midrange. Not unpleasant, but a bit too Ďforwardí for my tastes. Weíll tame that with a combo of room treatments and EQ.

    As Iíll update later on the SL3XC build thread, the tuning of the center along with time and phase alignment across all three front speakers results in an astounding soundstage.

    The biggest difference is in the mid-bass of course. Not only do the new Monolith panels play louder and lower than the older ones, the higher crossover points and the new woofer conspire to really fill in the mid-bass. And since that it where drum hits, bass guitar and so many other instruments have either fundamentals or critical harmonics, it really brings the sound to a new level.
    The big mid-bass line array in the SL3 based center now really keeps up (actually, itís better than) the Monoliths. This is something that now gives the front soundstage its width and depth that Iíve never heard before. And thatís in a room designed for these MLís

    Listening to Ďdanceí music, like Madonnaís latest (well produced and recorded dance stuff) ĎConfessions from the dance floorí is actually an impressive experience on the MartinLogan set.
    I always used to pick Jazz, vocals and other acoustic music to show off the MLís because it highlights their strengths while hiding the fact that they are lacking in Ďpunchí. Well, no more. They truly rock now.

    Of course, they do subtle vocals and solo piano like no other. Frankly, with better authority than ever with the improved mid-bass foundation.

    All in all, worth the effort and expense.

    If you have Monoliths with >12 year old panels (or panels that have sat in the light or harsh environments). Call ML pronto and order your new panels. You will not regret it.
    Last edited by JonFo; 05-22-2006 at 03:34 AM.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  14. #14
    Super User JonFo's Avatar
    Join Date
    Jan 2005
    Location
    Big Canoe, GA
    Posts
    3,532

    Default

    Quote Originally Posted by ted betley
    ...

    Hi I don't fully understand the implications of this post Since I have had difficulty getting my loctited screws out of the panels I'm sure this post has some relevance for me.
    What do you mean by bolts screwed into the driver? Did you pry loose the driver with a crowbar without trying to loosen the screws thereby ripping out the female metal sleeve receiver within the wood? Or does it mean something else?
    Ted, the drivers are held in by hex drive screws. Those come out pretty easiliy.

    Prying the driver out of the hole may or may not be an issue. My ACI's were bonded into the leather by some sealant strips they had on the backs.

    Since sticking a screwdriver or anything like that around the edge of the driver would A) risk damaging the leather or B) risk damaging the driver, I decided to try a different approach.

    By screwing in some bolts that thread into the woofers holes (which normally are designed to let smaller screws through) I now have some big metal items that are two inches long, have a 'head' that I can pull on and are secured to the driver.

    By placing a hammer on a piece of metal, which itself is on top of a cloth, I can now use the hammer nail removal claw to pull 'up' on the bolt head with a good bit of leverage. I'm just trying to break loose the bonding between the driver an the enclosure.

    I recalled the factory drivers required a bit of effort to get out as well. This trick would have speeded up the process.

    I hope this clears it up.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

  15. #15
    Senior Member
    Join Date
    May 2006
    Location
    Boise, ID
    Posts
    441

    Default

    Hehe...good trick. We were once trying to replace the woofer in a B&W ASW850 sub and it was really sucked in there good. We ended up holding upside down an inch or so off the floor, and playing 5HZ through it with a generator. It broke free.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •