X-MTM and X-CS build

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Re: X-MTM and X-CS build
« Reply #20 on: 24 Feb 2021, 04:57 pm »
Here is a thread showing something like I was talking about, but with butt joints:

I might have considered glueing in the other end piece first just to keep thing rigid.  The other thing to consider is to glue the braces into the one side.  Once all of those are done, see how the other side fits.  If some of the dados need to be opened up to make it fit, go ahead and open them.  If they have a big gap, use the Titebond Quick and Thick for the gluing.

Here is what i did with the plastic wrap:


Re: X-MTM and X-CS build
« Reply #21 on: 1 Mar 2021, 10:32 pm »
Got a lot done this weekend after doing the forensics on the mildly disappointing MTM glue up last weekend.  I picked up a few more clamps last week and decided the first glue up would only be the back, top, bottom, and one side.  I was a little more sparing with the glue this time around as well as I think the sheer volume of glue last time was an issue.
I used two of the braces and the other side to help align things and elevated the unglued side with a couple scrap pieces of MDF to keep it from getting glued in at the corner.  I was able to keep the dados for the braces clear of glue by scraping it out with the end of the glue brush which took some tending but worked out well.  After that glue up set, it was a simple matter of inserting the braces and other side for the final glue up.  This went wayyy better than the first cabinet.  I ended up with far better joints and everything lining up like I planned.

All three speakers are glued up as much as I can do at this point.

I then broke out my new trim router to trim down the sides.  I'm really glad I got this as I'm sure I wouldn't have been able to do nearly as good a job with my full size router.  Watching Peter use a big one to trim veneer makes me appreciate how skilled he is with a router.  The trim router is much more manageable for tasks like this, and even then I make a couple mistakes moving it to and from the workpiece where I accidentally tilted it toward rather than away from the corner.
That said, it's pretty remarkable how much that cleans everything up and made it look so much better.
Next came some quality time with some Bondo all purpose filler.  I am very familiar with this type of product after using Evercoat for many, many years in boat repairs. The smell is almost comforting at this point...almost.  I used this to fix some of my glue up errors from last weekend and correct the small mistakes with the trim router.  I used Bondo because it will be under veneer (so who cares what it looks like), I know it will stand up to the heat of the heat lock glue, and I knew exactly what the results would be.  A couple batches later and everything was smooth.
You can see the difference in the joint between the first glue up from last weekend and the one I did this weekend.  Night and day difference.

Ready for the next step.

The last task for this weekend is to get the front ready for glue up by getting holes drilled for dowels.
My poor mans drill press and drill block came in handy here.

I was a little nervous about this part, but it turned out to go much quicker and smoother than I anticipated.  After locating and drilling the holes in the cabinet (44 in total for each MTM!)  I used some dowel centers and lightly clamped the front to the cabinet making sure I had alignment on all four sides.  A 5lb sledge and scrap of MDF helped ensure the pins were adequately impressed on the surface of the MDF.  This process took a few steps for each speaker as I only have 20 centers and replaced the centers with dowels as I went to keep everything aligned.

Ok, now my photos are starting to turn upside down.  What the heck.

The final dry fit of the fronts with all the dowels inserted was perfect and the final glue up of the fronts (somewhere in the future) should go really smoothly.

Next steps:
I got some decisions to make.  I'm waiting on a quote from a local CNC shop to route baffles out of 1/2" acrylic.  My crazy plan is to paint the backside of the acrylic in black with a simple geometric design painted in copper carved in the backside.  This should give the illusion of the drivers hovering in front of the copper design.  The acrylic will be only big enough to sit under the drivers and will be the exact same size for all three speakers. I'm doing a test piece with some painted acrylic on MDF with E6000 glue.  The MTM's will be walnut below the acrylic.  I'm going for kind of a modernized 60's/70's sci-fi shtick with these.  They may not be to everyone's taste, but my wife thinks the sketchup looked cool and it will match some of the other fixtures and treatments in the room.  Then again, this could be completely over the top.  This will be a pricy way to go (both material and routing), and if the I can't get the CNC done for reasonable amount or if the glue method isn't up to par, I'll just go with full walnut veneer (which will still look good).
At this point I'm at a holding pattern with the cabinets while awaiting parts from Danny, particularly the no-rez which I have a feeling will take a little while to cut and install.

Things I learned/opportunities for improvement/screw ups:
- Mostly this weekend was about having a more enjoyable time in the shop between a better glue up approach, fixing some past mistakes, and seeing how having some of the right tools for the job led to better results  :duh:.  As obvious as this is, it's nice to have some confirmation.
- Lost one pack of 50 dowels after buying them a week ago, so I guess another trip to the store is in order.
« Last Edit: 2 Mar 2021, 02:56 pm by JWCoffman »


Re: X-MTM and X-CS build
« Reply #22 on: 2 Mar 2021, 12:35 pm »
Congrats on the glue-up...   :thumb:

These a coming along nicely.  Although, I am a little confused about your plans for the front baffles and how they will look.  However, I will leave that as an excuse to continue following this build, and see what develops.  I am sure you will document it well.  :popcorn:

As for the “rotating” pictures.  This seems to be a nuance of the web site.  It randomly rotates images that one uploads.  It is easily corrected, though.  First, use your gallery to upload your pictures.  I found it best not to use the button at the bottom of the “Reply” window that says “Upload and insert an image”.  Open your gallery, at the bottom should be a blue button that says “upload images”, plural.  Once you have uploaded the images to your gallery, scroll down to the newly uploaded images and look to see if any are rotated from what you want.  If there is, click the thumbnail of that image.  That should open the image in a window that you can use to edit the image.  At the bottom of this window is a set of buttons to rotate the image left or right.  Once you have corrected the rotation, click the link above the image that says “up to (gallery name)”.  This link will be centered between “previous image” and “next image”.  This will take you back to your gallery.  If you have more than one image that needs to be corrected, click either the “Previous” or “Next” button.  Then use the “Up to ***” button to return to your gallery.  Also, on your “Manage your gallery” page, you can open/create albums and name them to help organize your images. Hope this helps...


Re: X-MTM and X-CS build
« Reply #23 on: 2 Mar 2021, 03:04 pm »
Thanks for the tip re: the photos.  I went through and corrected them and reuploaded the one from my previous post, but it's still upside down.  I'll need to play with it more.

Below is a screen grab from my Sketchup file.  The black and orange parts are acrylic with the black painted on the backside and the orange part (that shape is called a stadium, BTW) will be routed 1/4" into the backside and painted copper.  This will give the illusion of the drivers hovering above a piece of copper on a black background.  Hopefully that makes sense.  The wood parts will be walnut veneer with a simple Danish oil (or maybe just tung oil) and shellac.  Perhaps some polyurethane as a final step to protect it if I feel it's necessary.

The bases are...I dunno.  I'm less enthused about having those be acrylic, so they'll most likely just be walnut.


Re: X-MTM and X-CS build
« Reply #24 on: 3 Mar 2021, 02:03 pm »
I’m getting the idea.  Still, it will be interesting to see how it turns out.

I got my idea for the base from what others had done.  Of course there is the “unique and it’s my idea” base, but I was a bit uninspired when I got to that point.  :P  The things I did know that I needed in the base were that it needed to be wide enough to keep the speakers from being tipped over and they needed to have adjustable levelers as the floors in my house are not level... :o   :wink:


Re: X-MTM and X-CS build
« Reply #25 on: 3 Mar 2021, 03:58 pm »
I've been doing a little proof of concept work alongside the build to see how the acrylic plan might end up.  I got a small 4x4 piece of 1/2" acrylic, routed a 1/4" wide x 1/2" deep channel which I painted with some copper spray I grabbed at the local box store, then sprayed the back in an acrylic flat black.  There was no surface prep done to the acrylic other than trying to keep it clean.  I tested the adherence of the black with various implements and found it to be very well bonded.  Hopefully this gives a little bit of a sense of what I'm thinking.

I then glued it to a piece of scrap MDF with E6000 and let it cure for 48 hours (full cure is apparently 72 hrs, but I got impatient).  Initial tests are promising.

Much testing!  So science!

That's a 53lb kettlebell hanging from the acrylic with about a 4sq. inch glued surface area.  I let it hang there for about 10 minutes and had no issues.  I was tempted to try a 70lb kettlebell, but something probably would have shattered at that point and I have some more testing I want to do on the acrylic with a roundover.  I don't think the glue will be a weak spot.

After routing out the channel on my cheap router table, I realized that I probably don't have the tools and/or skill to cut three perfect stadia and nine perfect driver holes in what is somewhat expensive material.  I thinkg the prudent path would be to have them CNC'ed which should lead to smoother and more accurate results.  I'll still need to do the final trim, roundovers, and polish in situ on the cabinets to make it seamless, but that seems more doable, I just need to take my time.


Re: X-MTM and X-CS build
« Reply #26 on: 3 Mar 2021, 05:25 pm »
And practice...

Oh, you already said that.. :wink:

Interesting concept.   :thumb:

Not sure if this helps, but there are some clear glues out there.  I was able to glue 2 pieces of plexiglass together, face to face using a clear rubbery adhesive.  I wanted to make a large, clear 1/4” thick router plate out of two 1/8” thick pieces.  It came out well, with only a few bubbles that I didn’t bother to work out.  Like I said, not sure if it helps with anything you are doing, but just a thought of something that can be done....

Peter J

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Re: X-MTM and X-CS build
« Reply #27 on: 3 Mar 2021, 05:46 pm »
Good on ya for blazing new trails with the acrylic. That's the stuff that trips my trigger to a large extent. The one sure thing is that you'll learn something. A noble goal, IMHO.

And if you didn't know, there are (at least) two flavors of acrylic sheet. Cast and extruded. I can tell you that the cast acrylic machines much cleaner on CNC. The extruded tends to melt and gob up...not pretty.


Re: X-MTM and X-CS build
« Reply #28 on: 3 Mar 2021, 06:13 pm »
Good on ya for blazing new trails with the acrylic. That's the stuff that trips my trigger to a large extent. The one sure thing is that you'll learn something. A noble goal, IMHO.

And if you didn't know, there are (at least) two flavors of acrylic sheet. Cast and extruded. I can tell you that the cast acrylic machines much cleaner on CNC. The extruded tends to melt and gob up...not pretty.
Thanks for the somewhat reserved thumbs up.  I think there is general consensus that this may not end up working out like I hope, but there will be a lot of learning along the way.  I'm OK with that.

I've learned a lot about acrylic in the past month.  Cast is what I'm going with, which is much more expensive than extruded.  I'm not even sure you can get extruded in 1/2" as I've only seen it as thick as 1/4".  I've also seen that most CNC shops will not work on extruded for the reasons you mention.  Even the cast has it's idiosyncrasies where you still have to be aware of depth, router speed, and feed rate to ensure you don't melt it.  The roundovers are going to be a challenge as I need to make sure I'm only taking a little bit of material at a time and I keep the router moving steady.  On my test piece you can see where the router started to chatter due to trying to take off too much material and the feed rate being too slow as a result.  Once I made shallower cuts and sped up the feed rate it came out much better.  I still need more practice before the big show.


Re: X-MTM and X-CS build
« Reply #29 on: 9 Mar 2021, 05:15 pm »
*UPDATE* Danny responded and let me know there are only 2 needed per speaker, so somehow I ended up with two extra that I'll probably just send back to him.
Got my parts yesterday!  :thumb:
Immediately started laying out my crossovers and ran into a question regarding the Miflex caps, specifically how many I should have and where they go.
I got 4 included in the baggie with the X-CS caps and resistors and another 4 in a baggie separate from the X-MTM caps and resistors for a total of 8 for three speakers.
So, my question is how many should I have and where exactly do they go?
I found a proper crossover posted by Lebo in the "Crossover Assembly 101" sticky: https://www.audiocircle.com/index.php?topic=83325.260
It shows 2 Miflex caps inline with the Sonicaps in the tweeter circuit.  This makes sense to me, but then what do I do with the 6 I have for the MTMs?  My assumption is they would go on the same Sonicaps since the network is almost identical, but that leaves 2 left over, and I doubt Danny is running a Miflex charity program.
I did email Danny with this question, but I'm hoping someone here can pipe in and set me straight.

This is all very new to me. :scratch:


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Re: X-MTM and X-CS build
« Reply #30 on: 9 Mar 2021, 05:36 pm »
Glad ya got it all sorted!  :thumb:


Re: X-MTM and X-CS build
« Reply #31 on: 22 Mar 2021, 02:45 am »
It's been a relatively slow couple weeks on this build between a job getting busy, assisting aging parents, springtime projects, the house next door burning down, etc.  You know, the usual.
But I did make some steady slow progress over that time.
After getting the parts a couple weeks back I made the crossover networks my after work project during the week.

Many people on this forum have already mentioned this, but Danny's video on crossovers was immensely helpful in both how to approach it and some basic soldering techniques.  I have soldered things before, but never felt proficient at it.  I was able to test the crossovers last weekend and everything seemed to be working fine.  The woofers were playing woofer-ish frequencies and the tweeters were playing tweeter-ish frequencies.  It all sounded pretty good considering they were just sitting on my workbench.
Got to mounting the crossover and installing no-rez in the X-CS last weekend, but that's about it as much of the weekend was spent hoping our house didn't catch on fire.

This weekend was spent entirely on getting the crossovers installed in the MTM's, connecting the wiring, and installing no-rez.
I found that actually attaching the crossovers to the back of the cabinet was harder than anticipated.  Enter another tool purchase.

Installing no-rez was quite the process, and I'll be the first to admit that I probably overdid it and took a somewhat inefficient route.  I pretty much covered every inch of cabinet that I could in at least the base layer (not sure what it's called, but it's the actual resonance mitigating material).  And kept as much of the foam as possible.  I cut the foam at the corners where necessary to allow pieces to join together without compressing any foam.  I also prioritized using full pieces at almost every spot rather than several small pieces to cover a surface.  Unnecessary, I know, but it just felt more correct to do it that way.  What that meant is that I went through 7 pieces of no-rez, but have about 1.5 sheets in off-cuts that I can use for future projects.
Again, it's inefficient.
The other reasonably challenging aspect was getting the input and speaker wires measured, cut, stripped, and soldered, all while being deeply fearful that I was going to break off one of the thin resistor wires on the crossover board.  I ended up using a fair amount of hot glue under the soldered joint as a strain relief which greatly eased my mind.  I also used some hot glue to tack the wire runs to the braces to secure them and keep them from vibrating against a hard surface.  Has anyone done a deep dive into the sonic impact of hot glue around wire insulation?  It's probably fine.
I made the mistake of installing the X-CS crossover prior to connecting the input and speaker wires.  Twisting that solid core wire tightly enough in that tight space was challenging.  I did connect everything on the MTM's before installing the crossovers to the back of the cabinet, so I am learning from my mistakes.

Interiors done, ready for final assembly and finishing;

Next steps:
At this point I have everything I need to finish including the drivers, walnut veneer, acrylic, and finishing products (danish oil and shellac).  I even got my speaker spikes this past week from Dayton.
I'm still pursuing the acrylic idea even though the CNC quote came back higher than the price I'm willing to pay, so I'm scheming how to mill the pieces myself.  Luckily, I found a source for 1/2" cast acrylic for much cheaper than my original quote, so I feel much more confident trying this out given the lower cost.  The order of operations getting the pieces milled for both the speaker holes and the exterior dimensions of the cabinets is turning out to be a complex process.  I'll need to take my time with it and not get ahead of myself.

Things I learned/opportunities for improvement/screw ups:
- I wrote this in jonsk's thread, but I soldered the crossover of my X-CS before mounting it onto the board.  I ended up with a couple parts slightly off the board as a result.  NBD as I just carved out the foam to make room, but a little embarrassing.
- The insulation on the wire Danny provides is tough stuff.  I need to invest in a better stripper/crimper tool if I'm going to do more of these builds.  I kept saying to myself "Don't nick the copper" all while trying to get a knife through that stuff.  Taking insulating out of the middle of the wire is harder than Danny makes it sound.  Thankfully, in the end I only had one end I had to recut due to damaging the copper with the stripper tool and all the wire stripping I did in the middle of wires looked pretty good.
- I think I'm going to have enough slack in the wire for one of the woofers, but it's going to be tight.  I mis-measured a positive lead and didn't notice it until it had been fully soldered and heat shrinked (heat shrunk?).  I don't see why I needed to be so stingy on that one.


Re: X-MTM and X-CS build
« Reply #32 on: 22 Mar 2021, 01:59 pm »
First - Your builds are coming along nicely!  :thumb:

Second -  :wtf:  THE HOUSE NEXT DOOR BURNED DOWN AND YOU WERE WORRIED ABOUT YOURS?  Hope everyone, pets included, are ok, and you and yours are all ok...

For the next time - I think it was a Peter R video where he talks about no Rez, sizing it and putting it in.  Basically what I remember about it was that “close was good enough”.  A half to 3/4 inch to corners and braces was good enough for the first pieces to go in.  And then cut the pieces that will butt up against those first piece about 1-1/8 from the hard surfaces so the foam just clears or touches the first piece.  It will save a lot of no Rez as well as effort.

I ran into the same issue with stripping the wire Danny gave me.  I had a set of strippers I have used for years on house wiring.  They work great on the house wire - Not so good on Danny’s wire.  Look up “wire strippers” on YouTube before you buy one.  I did that and found some really good review of various kinds and how well they worked (sorry, don’t remember which I watched).  This was really worth while in helping me in my purchase.  I got a plier/scissor type that works well.  I’ll say it still takes some effort, though.  As for stripping the wire in a mid-section, I used an X-ACTO knife with a straight blade and wore a pair of cut proof gloves.  This worked better than a regular knife.

A thought for routing the acrylic - Make a template to use with your router and router guides.  Cut the template from ~1/2 plywood.  Cut holes in the plywood (maybe 1” dia) around the template at various locations and then cover the holes with some sheet aluminum, glued in place.  Then hot melt glue the template to the acrylic at the spots where the aluminum is.  This way you can heat up the aluminum through the holes in the wood to soften the glue to remove the template.  Not sure how to remove any residual  glue, though.  But at least this way you don’t have to deal with clamps.  Another thought would be to use this stuff to temporarily attach the template to the acrylic:

It holds really well, but I am not sure if it will hold well enough for doing the routing.  Might be worth a try.


Re: X-MTM and X-CS build
« Reply #33 on: 22 Mar 2021, 03:15 pm »
Sooo, yeah.  The house next door.  If the fire department got here much later we probably would have at least a partially burned house.  We live in a fairly dense neighborhood and the roof of our house and the one next door are about 12-15' apart.  The neighbor on the other side had some cracked windows from the thermal expansion due to heat, but otherwise their house was fine too.
Everyone, including pets, were fine, so we dodged a major bullet.  We also didn't get nearly as much smoke impingement into the house or attic space as we thought we might.  The local fire department did an amazing job keeping the surrounding houses protected.

Regarding acrylic.  My plan is to make a couple templates for guide bushings out of 1/2" BB like you suggest.  One template for the design and the other for the driver holes.  I'm going to use double sided tape (the kind you find at woodworking stores) to hold the template to the material.  I used the same method making the internal braces and it works really well.  The tape isn't cheap but I found a little bit goes a long way.  The good thing about the acrylic is it comes with a protective film on both faces so I don't have to worry about adhesive on the actual acrylic itself.  The big issue with acrylic and carbide bits is that you can only take a little bit at a time lest you melt the plastic or break a bit, so patience and accuracy will be key.


Re: X-MTM and X-CS build
« Reply #34 on: 22 Mar 2021, 03:55 pm »
So glad to hear people and pets are all ok and that you and you other neighbor came out of it OK too.  I would have a similar issue in my neighborhood although our houses are a little further apart.

It will be interesting to read about how you make out with the acrylic.


Re: X-MTM and X-CS build
« Reply #35 on: 29 Mar 2021, 04:17 am »
Sooooo many "learning opportunities" this weekend.

First, let's start off with what I have at the end of it.

Not too bad, though it does adhere to the "good from afar but far from good" rule.
A keen eye might notice that the copper colored portion is pretty close to the woofer holes.  In fact they are directly under the screw holes.  I simply took the dimensions for the stadium shape off the Sketchup drawing for the X-CS, which had the radii for the arcs 1/4" too small making the overall shape 1/2" too small.  The X-MTM drawing did have the correct dimensions, but of course I didn't use those.  This was a pretty critical error as it means there is not much material underneath the screw holes and the arcs would be completely hidden under the driver frames. :duh: I also made some painting mistakes where the copper paint didn't play well with the flat black.  The painting mistakes I could have overlooked as you would have to know they were there to really see them, but the addition of the dimensional error put this squarely into "I will regret this for the rest of my days if I don't make it better".  The fact that the mistake still turned out looking exactly the way I hoped only urged me to push ahead, so I'm going to completely redo all three of them.
I did have fun with templates, however.

I should say that there were some real successes:
- Carbide spiral up cut bits are much better with acrylic than straight cut bits.  You can't take a bunch of material in one go, but the quality of cut is far superior in the end.
- My routine for lining up the two templates I was using worked very well and the circles and arcs lined up as well as I had hoped.  Double sided tape is the way to go.
- The copper against the flat black looks amazing, unfortunately the photos don't quite do it justice.

Here's the same piece with a dish that my wife picked up off ebay this past week.  We're thinking along the same lines with decor.

I'm a little bummed about the mistakes, but I'm pretty excited about the results and can't wait to try again.

Things I learned/Opportunities for improvement/Screw ups:
- Pretty much all listed above.  I simply made the wrong assumption that the correct measurement had translated from the X-MTM to the X-CS, which it had not.
- Acrylic has a real static issue when milling that gums up the works when using guide bushings.  Since my router plate is also acrylic, shavings were collecting on the guide bushing and getting in between it and the template.  This was a real issue with the stadium-shaped template where the tolerances are much tighter than the driver holes.  I'll need to investigate static mitigation for next weekend to see what can be done.
- Even though the flat black paint had dried for several days, the copper paint catalyzed the black all over again in a couple spots and made for some poor results.  I've got another plan for painting the next ones which should eliminate that issue.


Re: X-MTM and X-CS build
« Reply #36 on: 29 Mar 2021, 01:04 pm »
Pretty amazing!   :thumb:

These will be a real show piece.

Are you using a vacuum attachment on the router when you are working on the acrylic?


Re: X-MTM and X-CS build
« Reply #37 on: 29 Mar 2021, 02:02 pm »

Are you using a vacuum attachment on the router when you are working on the acrylic?

There are actually a few issues to deal with, of which the static is the most vexing.  The base plate I'm using is the only one I have that takes the guide bushings I'm using, but with the guide bushing in (which has an ID just a little bigger than the 1/4" bit) there is no way to suction material upwards past the bit.  The other issue is that the shavings come off pretty chunky.  This is actually a good thing with acrylic as it shows the material is staying cool and the bit is cutting cleanly, but the pieces are far bigger than the dust you would normally get with a straight cut bit in wood.
All this points to the fact that CNC is still a better solution for acrylic as it alleviates all the issues related to templates, but the cost is simply too high for these.  I could pick up a Shapeoko CNC for close to the cost I was quoted for these three pieces.


Re: X-MTM and X-CS build
« Reply #38 on: 29 Mar 2021, 04:01 pm »
This winter I had static issues just cutting the MDF.  I would get shocks from the router.  Probably had something to do with the plastic vacuum hose I was using.

I know what you mean about using the template guide and it blocking the vacuum from doing much.  I do a lot of my work with an up-spiral 1/8” bit.  Originally I thought the up-spiral cutter would draw stuff up enough to make the vacuum effective.  However, that wasn’t so. 

I know you said that you have just that one base plate, but I was wondering if you thought that putting slots in it around the opening for the template guide, leaving enough material to support the guide, would at all be helpful at making the vacuum affective.  It would mean getting a second base plate, to cut up.  I did some “routing” of plexiglass on my drill press and that worked well.  The cutting speed is really slow compared to a router and it “cut” at that speed.  Not saying for your acrylic piece, but maybe as a way to slot a base plate.   Again, just thinking out loud.


Re: X-MTM and X-CS build
« Reply #39 on: 29 Mar 2021, 08:04 pm »
I'm looking at a few base plate options including just routing out some holes in my existing one for vacuuming.
I talked to someone at TAP plastics today about the static issue and they basically just said "deal with it".  They agreed it sucks too and they just spend a lot of time cleaning their cutting and milling equipment.
 I think my best option is the vacuum route and figuring out how to clear the chunks before they get caught in the works.
Perhaps a combination of compressed air into the template channel and vacuum above the base plate will help solve it.  It'll require another set of hands but I think my wife will oblige.  I'll do some testing with all this scrap material I now have.