New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[jinjuku]

Btw

Nice looking build. This hobby is going to cost me too much time...

At least as I go through builds I can most likely get rid of stuff at cost RIGHT GUYS?

 

[sawzalot]

Even expensive hole saws clog easily when cutting MDF. The problem isn't cheap cutters in this case, it's the fact that the gullets are so shallow and the dust has nowhere to go. If this was solid wood, I'd suggest using Forstner bits for the small holes and a hole cutting jig on a router for the large ones.

I made a jig for my smaller router and I've been using it for all of the holes on the speakers I'm building now, including the 2-3/16" holes for the ports. I didn't do anything particularly creative for the braces- I left 1-1/4" on the outside of the extra pieces that I cut (same size as the tops and bottoms) and since I rabbeted them 1/4" into the sides/front/back, they're plenty strong. I also rabbeted the front and back so they fit into the sides/top/bottom and they fit so well I'm checking them out with no clamps and only the top screw in the top woofer is screwed into a brace.

Sounds like a really tight box, , can you post a pic of the front install with the rabbeted areas, I would like to see the side view of the edges up and down and across the top. Is there some disadvantage to using screws besides the whole filling and sanding routine ?

Skyline I noticed your sides were a bit longer than the top and bottom did you glue and fasten then go back with the flush trimmer and remove the over hang (extra material ) ? Thanks sawz..

 

[highfigh]

You are most likely using too much pressure. You want to avoid glue squeeze out.

Depends on how much you are going to get into this hobby. The Jasper jig is $33 and there is a Craftsman jig for under $30. Money well spent. That and a TON of clamps.

I only glue and clamp. Even my subs are interlocked braces with only wood glue.

I just bought more clamps at Harbor Freight and IMO, they're the best bargain out there. The 12" are $4.49, the 18" are $4.99 and the 24" aren't much more. I gave up on the plastic ones because they don't handle stress well. The ends broke, the pins at the lever pivot broke- it's just not worth using them when they break in the middle of a glue-up and it's one of the last clamps I had at the time. I exchanged them for the metal ones (black rail with blue/gray) and I should be pretty well set for a while.

Then, while I was in line yesterday, some rat-bastige gave me a 20% off coupon that's good on everything, including sale items. I had been thinking about the 12" disc sander but I'm not thinking about it anymore. Now, I have to find a place for it. I don't think he had any idea how much of an inconvenience it will be to have this.

 

[highfigh]

Sounds like a really tight box, , can you post a pic of the front install with the rabbeted areas, I would like to see the side view of the edges up and down and across the top. Is there some disadvantage to using screws besides the whole filling and sanding routine ?

Skyline I noticed your sides were a bit longer than the top and bottom did you glue and fasten then go back with the flush trimmer and remove the over hang (extra material ) ? Thanks sawz..

Sounds like someone needs a cold shower.

The photos are in my other computer but I'll post them later. The edge that's visible is 1/2" and 1/4" is in the box. I'm not sure how they'll be finished- the wife of the customer has a designer who doesn't want to see them, she doesn't really care about this kind of stuff (she said he and I are dorks for caring about sound quality this much) and I may just paint them black. The ones I let him use were covered with black trunk liner because they were never intended to be anything other than test boxes and he liked the fact that they kind of visually disappeared when they were in the room. If I do paint them, I may add a cleat in the front corners before I glue them up and route 1/2" out of the corners, so I can inlay a piece of fine-grain hardwood before I round them over. That way, I don't have to deal with MDF edges soaking up the paint. I may bevel the corners, too.

 

[sawzalot]

Sounds like someone needs a cold shower.

The photos are in my other computer but I'll post them later. The edge that's visible is 1/2" and 1/4" is in the box. I'm not sure how they'll be finished- the wife of the customer has a designer who doesn't want to see them, she doesn't really care about this kind of stuff (she said he and I are dorks for caring about sound quality this much) and I may just paint them black. The ones I let him use were covered with black trunk liner because they were never intended to be anything other than test boxes and he liked the fact that they kind of visually disappeared when they were in the room. If I do paint them, I may add a cleat in the front corners before I glue them up and route 1/2" out of the corners, so I can inlay a piece of fine-grain hardwood before I round them over. That way, I don't have to deal with MDF edges soaking up the paint. I may bevel the corners, too.

That was another question of mine, If one was to put the large roundover on the edges is the cleat something that is a must at the inside corners, I mean after all one would be removing quite a bit of the stock material correct, and I can see how just glue at that area is a must.
Back to your rabbeted edges I got a bit confused for some reason I was thinking that the front would over hang the sides by a 1/4 inch but I guess I have been working with kitchen cabinets a little more than speakers, that front edge finishes flush with the sides leaving 1/2 inch exposed right?

On the plans for the build here, the mounting of the tweeter says to mount 3/4 of an inch off of the horizontal center, should that be the vertical center ??

 

[skyline_123]

Given the choice, I would use screws when assembling with butt joints. If it's dado and/or rabbet joints, I don't. Butt joints aren't as strong because they don't have as much glued surface and any way to resist shear if the parts are trying to pull apart. If you don't want to sand as much, don't leave as much compound on the joint- do it like drywall mud and keep it thin, but build it up as needed. Also, use a file when possible- it's faster and leaves the surface flatter because you're only removing the compound. Then, sand it smooth.

Great points here. Thanks. The problem I face when filling holes (I use bondo for the larger voids) is that when trying to scrape off the excess with my putty knife, the surface tension so to speak will draw the bondo back out of the hole, which is why it is built up so high. I either apply it two separate times or build it up higher than normal. I guess I could always try a different filler. I like your idea of hitting it with a file before sanding.

Nice looking build. This hobby is going to cost me too much time...

At least as I go through builds I can most likely get rid of stuff at cost RIGHT GUYS?

Thanks. I really wish this were true. I would be more willing to build more designs if it were.

Skyline I noticed your sides were a bit longer than the top and bottom did you glue and fasten then go back with the flush trimmer and remove the over hang (extra material ) ? Thanks sawz..

You are correct. It gives you a little more tolerance while cutting, which saves time, and at the end after you used a flush trim bit, it's near perfect.

On the plans for the build here, the mounting of the tweeter says to mount 3/4 of an inch off of the horizontal center, should that be the vertical center ??

Hmmm...I can see it either way. Of course, I just look at the pictures.

 

[drab]

Has Dennis or Paul published this design somewhere? I can't find it anywhere but here.

 

[highfigh]

That was another question of mine, If one was to put the large roundover on the edges is the cleat something that is a must at the inside corners, I mean after all one would be removing quite a bit of the stock material correct, and I can see how just glue at that area is a must.
Back to your rabbeted edges I got a bit confused for some reason I was thinking that the front would over hang the sides by a 1/4 inch but I guess I have been working with kitchen cabinets a little more than speakers, that front edge finishes flush with the sides leaving 1/2 inch exposed right?

On the plans for the build here, the mounting of the tweeter says to mount 3/4 of an inch off of the horizontal center, should that be the vertical center ??

Right- the edges at the sides are flush with the front being inset 1/4".

I have seen speakers that were all centered, off-center, butting up to each other and separated. The Cookbook says the tweeter and mid (in a 3-way) or woofer (in a 2-way) should be no more than 1/2 of the crossover frequency's wavelength. The last ones I built for myself were just less than that and the edge of the tweeter's outer edge was in-line with the edge of the woofer's frame. They sounded good but after replacing the woofers & tweeters twice and re-configuring the crossovers a couples of times, it was time to start over.

The cleat just adds more meat at the corners of the front and i don't think I'll round the back edges over much, so it's not an issue. The front will get at least 1" radius, although I may use a thumbnail bit instead (wider and shallower than a round-over bit).

 

[highfigh]

Great points here. Thanks. The problem I face when filling holes (I use bondo for the larger voids) is that when trying to scrape off the excess with my putty knife, the surface tension so to speak will draw the bondo back out of the hole, which is why it is built up so high. I either apply it two separate times or build it up higher than normal. I guess I could always try a different filler. I like your idea of hitting it with a file before sanding.

If you use drywall screws for this, get the dull oxide coated ones. The Bondo will stick better. Another trick to getting it to stick better is spray a little car paint primer on them and let it dry. The Bondo will definitely stick to that and if they want to let go while it's wet, they can pop out once it dries. You can also let it lift out and go back in the opposite direction to get it more flush. I like Bondo for filling wood but there's another filler that moves more like wood and it's lighter- I may try it next time I need more.

 

[highfigh]

Sounds like a really tight box, , can you post a pic of the front install with the rabbeted areas, I would like to see the side view of the edges up and down and across the top. Is there some disadvantage to using screws besides the whole filling and sanding routine ?

Skyline I noticed your sides were a bit longer than the top and bottom did you glue and fasten then go back with the flush trimmer and remove the over hang (extra material ) ? Thanks sawz..

Here's some photos-

 

[skyline_123]

Here's some photos-

Now THAT is a good looking enclosure. Quite inspiring.

 

[highfigh]

Now THAT is a good looking enclosure. Quite inspiring.

I have to give a lot of the credit to my saw and blades. I set the fents (yes, it's supposed to be plural) to a dimension and although I occasionally check a piece after I make a cut, it IS that size. It cuts square, straight and never goes out of adjustment. I also use only one tape measure, to keep tolerances from stacking up and causing inaccuracy. All I do is set the fents (a good band, BTW) and push the wood through.

 

[skyline_123]

Christmas came early.

 

[Swerd]

Hey Sean

Nice progress with the cabinets - great photos. I'm superstitious about cutting holes for the drivers, I never trust the dimensions given on the websites. I wait until I get the drivers in hand. I hope Madisound had the correct dimensions. Also, go buy yourself some cheap dust masks now that you've finished most or all of the MDF cutting!

Highfigh - thanks for all your experienced tips. Can never have enough tips. I avoid using screws, and have used bondo or spackle as fill. Instead of using a file before sanding, I use a small palmsized Stanley Sureform after the filler dries, and then follow with sanding.

Someone (drab) asked earlier if this design has been published elsewhere. No it hasn't. I believe Dennis will eventually post it on his DIY website, but I'm not sure. I wrote it up and made the diagrams hoping to prod Dennis along.

This morning, I'm at Lake Placid, looking out my room over Mirror Lake. The hotel has wireless internet. My wife is still beautifying herself before we go and find some breakfast. So I'm looking at all of Sean's photos .

 

[drab]

Thank you for the info Swerd.

I wrote it up and made the diagrams hoping to prod Dennis along.

Good luck with that!

 

[skyline_123]

Hey Sean

Nice progress with the cabinets - great photos. I'm superstitious about cutting holes for the drivers, I never trust the dimensions given on the websites. I wait until I get the drivers in hand. I hope Madisound had the correct dimensions. Also, go buy yourself some cheap dust masks now that you've finished most or all of the MDF cutting!

Highfigh - thanks for all your experienced tips. Can never have enough tips. I avoid using screws, and have used bondo or spackle as fill. Instead of using a file before sanding, I use a small palmsized Stanley Sureform after the filler dries, and then follow with sanding.

Someone (drab) asked earlier if this design has been published elsewhere. No it hasn't. I believe Dennis will eventually post it on his DIY website, but I'm not sure. I wrote it up and made the diagrams hoping to prod Dennis along.

This morning, I'm at Lake Placid, looking out my room over Mirror Lake. The hotel has wireless internet. My wife is still beautifying herself before we go and find some breakfast. So I'm looking at all of Sean's photos .

Thanks Richard. I'm having a lot of fun building these and learning a lot in the meantime.

The hole dimensions are pretty close. I'm not 100% sure because I didn't actually use them. I too wait until I get the drivers are in my hands and take measurements directly from them.

God willing, I'll get the 1.25 mH inductors in the mail today (BO'd from PE) and will be listening to them ALL night long.

 

[darien87]

Lookin' good so far!

 

[Swerd]

Here are some pictures of the front baffle.

Sean

On that outer front baffle piece, what radius did you use on your jig when you cut rounded lower edge? I like the look of that curve. When I made the diagram, the radius of the curve was shorter, and it looked wrong to me.

Also, is that 0.5" or 0.75" thick plywood?

 

[Swerd]

On the plans for the build here, the mounting of the tweeter says to mount 3/4 of an inch off of the horizontal center, should that be the vertical center ??

Yes, that should say vertical not horizontal. Thanks for catching that.

Sean, because that is your post, you if you ask the AH moderator, maybe they can fix that for you, or let you edit it.


Correction made - ML

 

[skyline_123]

Sean

On that outer front baffle piece, what radius did you use on your jig when you cut rounded lower edge? I like the look of that curve. When I made the diagram, the radius of the curve was shorter, and it looked wrong to me.

Also, is that 0.5" or 0.75" thick plywood?

I used a pensil and string and had to play with the center point and the length until I got the curve I wanted. I then measured the string. I want to say the radius is about 7 or 8 inches but I cannot be for sure. I'll have to remeasure. I had to look up pictures of the ST's to get my inspiration. The diagram you drew puts the diameter at 9 inches, the width of the speaker. It looks okay but it would be hard to actually do. Seeing as I don't have a nice circle cuttin jig, I would not have been able to make it look good where the arc joins the edge.

Yes, that should say vertical not horizontal. Thanks for catching that.

Sean, because that is your post, you if you ask the AH moderator, maybe they can fix that for you, or let you edit it.

I'll get on that.