New DIY MTM Towers designed by Dennis Murphy and Paul Kittinger

[Swerd]

It's not THAT far of a drive, c'mon man.

I wish I could drive to hear them. I'm only 1300 miles away.

Thanks for all the great photos. They're looking great. Don't worry about the ¼" roundover. Like all DIY builders, you focus on the mistakes that only you can see. No one else will notice, or care .

Was gluing the front baffles before rounding over the edges your only mistake? It might be useful for others who are considering building these to know what order you did things as you assembled them. Now that you've built them, what might you do different?

Where did you mount the crossover board? Did you run into any trouble as you installed it, and all the various wires?

Did you install the polyfill yet, and how much difference does it make in the sound? It would be easy to do a simple comparison after you've done one speaker.

How did you lay out and cut the hole for the tweeter?

 

[skyline_123]

Thanks for all the great photos. They're looking great. Don't worry about the ¼" roundover. Like all DIY builders, you focus on the mistakes that only you can see. No one else will notice, or care .

Was gluing the front baffles before rounding over the edges your only mistake? It might be useful for others who are considering building these to know what order you did things as you assembled them. Now that you've built them, what might you do different?

Where did you mount the crossover board? Did you run into any trouble as you installed it, and all the various wires?

Did you install the polyfill yet, and how much difference does it make in the sound? It would be easy to do a simple comparison after you've done one speaker.

How did you lay out and cut the hole for the tweeter?

Thanks Richard, that's encouraging. I showed Erin my wimpy 1/4" roundovers and she couldn't tell there was anything wrong with them. She liked it in fact.

I have not filled them with polyfill. I will do one with polyfill and the other without and report on the differences once I get these painted.



I know I am forgetting some things but here is the process I used (or should have used) to construct these speakers.

My goal in the beginning was to make as few changes to the table saw as possible to ensure all dimensions are as identical as possible. The extra care in the beginning makes a big difference in the end.

1. Rip pieces of MDF 12” in width; these will serve as your sides, top, bottom and braces.

2. Now that the width of all these pieces is identical, cut the top, bottom and braces 7.5” wide so that they will all be identicle. At this point, the braces can be hollowed out according to the drawing.

3. Cut the sides a little long for now (44.75” to 45”); these will be trimmed later using a flush trim bit.

4. Cut the front, back and baffle pieces a little larger than needed (9.25” x 44.75”), leaving a small amount of overhang that will be trimmed later as well.

5. Glue the sides, top and bottom pieces first. Make sure the distance from the top and bottom piece is accurate according to the drawing (and square). Trim the overhang on the sides.

6. Glue the back piece on, trim the overhang and cut the hole for the port.

7. Dry fit the front piece using screws and trim the overhang.

8. Dry fit the front baffle onto the front piece using screws and trim the overhang.

9. Remove the front baffle and cut out the speaker mounting holes and round over the outside edges. If desired, used a beveled edge bit on the underside of the holes (make sure to leave room for any hardware used to mount the drivers).

10. Once the holes are cut in the front baffle, transfer them to the front piece. These holes can be larger than the ones in the front baffle.

11. Once the hole locations are known on the front piece and baffle, you can now glue the braces in accordingly.

12. Glue the front piece.

13. Glue on the front baffle.


Here are just some of the issues I’ve had with the construction. I will try to add to this as my memory comes back to me.

One thing to look out for is the interference between the crossover and the port. One of the inductors is quite large and since the port sits so close to the bottom and goes so far into the enclosure (especially if using flared ends), it tends to interfere with the crossover. I actually have to mount the crossover on the side of the enclosure at the bottom. If I were to do it again, I might just make an external crossover box or try hard to make it as compact as possible.

The holes for the tweeter are a bit strange and to be honest, cutting them was simply a trial and error process. I actually made some cuts with the router, test fitted the tweeter, and made more cuts until I got it to mount properly. Not professional at all but it works.

So you think your itch is scratched, huh?
That's what Audioholics is all about ... being content with the gear you have.

I'm glad to see that you have an excellent set of speakers for your efforts.
You have fallen in with a fine group of fellows but don't think for a second that you're all done.
This is the beginning.

My itch is definitely scratched. I think I am happily content with my gear, it's now a matter of getting a room with proper treatments that will do these speakers justice.

A fine group of fellows, indeed! I wrote in one of my first posts that I was going to build a home theater system based on the recommendations of people on this board. I have not been let down a bit!

 

[Swerd]

Thanks for taking the time to make that list. It can help in avoiding mistakes. I bet you wish someone had made such a list for you .

Your point about ripping all your work pieces to the same 12" width is a very good one. It made all the later assembly steps work better.

Your router work is excellent. And your photos made it very clear how you did the final trimming to get the outer dimensions right. In my hands, I also find it is much easier to do it that way than to try to get everything just so with the table saw.

I think I saw in your photos that you glued on the tops, bottoms, and braces at the same time. Do you really think delaying the braces until later makes a difference?

I also wondered just where you could fit the crossover board. I couldn't offer any suggestions because I couldn't guess how big it would be. Can you remember what size board you mounted the crossover parts on?

I don't think there is any problem with where you did mount the board. It might have been easier to install it before you glued on the front baffle. But you managed anyway .

 

[jinjuku]

One thing to look out for is the interference between the crossover and the port.

Remember you don't have to keep your x-over components all on the same board. You could for example create one board for the tweeter circuit and another for the woofers. You could even divide that assembly up into a couple of sub components.

 

[skyline_123]

Thanks for taking the time to make that list. It can help in avoiding mistakes. I bet you wish someone had made such a list for you .

A list would have been nice but often the best lessons are learned the hard way.

Your point about ripping all your work pieces to the same 12" width is a very good one. It made all the later assembly steps work better.

Your router work is excellent. And your photos made it very clear how you did the final trimming to get the outer dimensions right. In my hands, I also find it is much easier to do it that way than to try to get everything just so with the table saw.

I think I saw in your photos that you glued on the tops, bottoms, and braces at the same time. Do you really think delaying the braces until later makes a difference?

Thanks, having router bits with decent bearings makes things easy. There's really no skill involved.

I constructed the two enclosures in a different order and of the two, I definitely prefer the second method (the one I listed above) where I waited to install the braces. The reason I waited until the end to install them is because I wanted to place the top two braces directly behind the drivers and rather than needing to be exact in my measurements, I simply waited until I cut out the holes in the front baffle. The bottom two braces can be installed whenever.

I also wondered just where you could fit the crossover board. I couldn't offer any suggestions because I couldn't guess how big it would be. Can you remember what size board you mounted the crossover parts on?

I don't think there is any problem with where you did mount the board. It might have been easier to install it before you glued on the front baffle. But you managed anyway .

I would like to say that I built and installed the crossover after the enclosures were built for a specific reason, but I'm not sure I have one. On the other hand, by installing the crossover afterwords, you are guaranteed that in the event of a problem, you will be able to uninstall them and remove them out of whatever hole you installed them in. That's it!



Here's a shot of my crossover. You'll notice that I have about 12 inches worth of wire that installs directly into the crossover. I did this in case I need to remove the crossover, I would not need to take out the drivers to disconnect them.

Remember you don't have to keep your x-over components all on the same board. You could for example create one board for the tweeter circuit and another for the woofers. You could even divide that assembly up into a couple of sub components.

This is good advice. What method do you use to secure the crossovers to the inside of the enclosures? I was thinking of adding some small rubber feet to the board and fasten it using small screws.

 

[skyline_123]

A little progress was made today. I am trying my hand at using an HVLP Gun for the first time. It's getting a little cold here and the bondo is not curing like it should. I'm letting them sit in the house for a while. Then it's off to shoot some more primer.

In the meantime, on to another project. Can you guess that design? First person who gets it wins a swift pat on the back.

 

[Alex2507]

Where did the HVLP sprayer come from and what model is that? That toy will enable you to take the finish to the next level and beyond. A couple of my friends up here have them and I've been wanting to get further instruction on using them but getting somebody to give you that kind of time requires a worthy piece to work on ... like your speakers.

Regarding the inside of the speaker I think getting as much of it sealed with anything (latex/acrylic/urethane) out of a spray can would restrict the wood from absorbing moisture from the air. I think giving it the same finish as the outside is the path to madness but spraying whatever you can hit through the port and driver cut outs makes sense to me and it's cheap and easy. Doug? ... just grow up, okay?

 

[annunaki]

In the meantime, on to another project. Can you guess that design? First person who gets it wins a swift pat on the back.

TriTrix from PE. Pretty common kit but well designed and inexpensive.

 

[skyline_123]

d

Where did the HVLP sprayer come from and what model is that? That toy will enable you to take the finish to the next level and beyond. A couple of my friends up here have them and I've been wanting to get further instruction on using them but getting somebody to give you that kind of time requires a worthy piece to work on ... like your speakers.

Regarding the inside of the speaker I think getting as much of it sealed with anything (latex/acrylic/urethane) out of a spray can would restrict the wood from absorbing moisture from the air. I think giving it the same finish as the outside is the path to madness but spraying whatever you can hit through the port and driver cut outs makes sense to me and it's cheap and easy. Doug? ... just grow up, okay?

The HPLV Gun, Starting Line E-07, is a friend of mine's gun he uses for his cars. He's been kind enough to lend this to me but unfortunately, his time is very valuable and was only able to give me a quick run down on how to use/clean it.

I have done body work and painted a car back when I was in high school but it's been a while. As I recall, the majority is prep work and the painting only takes a few minutes.

I will take a brush and primer the inside the best I can. It will be hard to fit those pythons in the small holes though.

TriTrix from PE. Pretty common kit but well designed and inexpensive.

Dang, you're quick. Good job! They are pretty common but not too many post anything about them. In the end, I'll be able to compare some very nice budget speakers systems. I will have access to 2030p's, TriTix TL's, some Polk bookshelves (can't remember the model, Oscar?) and my ER18's. I also have a couple subs to compare. Dual Dayton 120's, sealed Infinity Kappa Perfect 10DVQ and the 12" Kappa Perfect Simple Build. I think I know what the clear winner will be BUT, it will be nice to see what exactly a few extra hundred bucks gets you in the speaker world. All I'm really missing in my comparison are the Primus 360/362's.

 

[STRONGBADF1]

The HPLV Gun, Starting Line E-07, is a friend of mine's gun he uses for his cars. He's been kind enough to lend this to me but unfortunately, his time is very valuable and was only able to give me a quick run down on how to use/clean it.

I have done body work and painted a car back when I was in high school but it's been a while. As I recall, the majority is prep work and the painting only takes a few minutes.

I will take a brush and primer the inside the best I can. It will be hard to fit those pythons in the small holes though.





Dang, you're quick. Good job! They are pretty common but not too many post anything about them. In the end, I'll be able to compare some very nice budget speakers systems. I will have access to 2030p's, TriTix TL's, some Polk bookshelves (can't remember the model, Oscar?) and my ER18's. I also have a couple subs to compare. Dual Dayton 120's, sealed Infinity Kappa Perfect 10DVQ and the 12" Kappa Perfect Simple Build. I think I know what the clear winner will be BUT, it will be nice to see what exactly a few extra hundred bucks gets you in the speaker world. All I'm really missing in my comparison are the Primus 360/362's.

You have the sickness!

Good stuff. Will be following your adventure.

 

[Alex2507]

Polk bookshelves (can't remember the model, Oscar?)

RTi6 IIRC.

The original owner (Phil/Speakerman39) of those Polks and my Primus 360's preferred the Polks over the 360's. Your mom said she preferred the 2030P's over the 360's ... whatever.

You should be able to find a forum with tips about using a gravity feed HVLP sprayer. About all I know about spraying is that you don't want the spray hitting the speaker at an angle. So point the sprayer directly at the work and don't angle it up, down, left or right. I think I would lay the speaker on it's side to paint the top and bottom and stand it up to paint the sides. Figure something out to separate the wet bottom from the work table when you stand it back up like standing it up on a few screws or something. Use a milk crate elevate the speaker. You need that to keep from having to point the sprayer down to spray the bottom. Make sure you have the right size nozzle for the finish you're applying.

Regarding the various wood finishes I tried to get as much info from the people I knew for a long time but nothing put me on the fast track like this book called Understanding Wood Finishing by Bob Flexner.

When I first started refinishing furniture I wanted every piece to be the brightest piece in the room. As my tastes evolved I came to understand that there was an understated elegance to low luster finishes. I am still happy with my high gloss brighter than the sun sheens but ...

I'm looking forward to seeing your choice of finish. Oh yeah, set up a light source that allows you to see reflected light on your work so you can see what you're doing with the gun ... maybe slap a 1'^3 MDF box together to practice on.

 

[Swerd]

Sean - Thanks for the crossover board photos. 10 x 5 is plenty big. Smaller would also work, but no problems with what you made.

I used to buy those stick-on rubber feet and attach the board with a few screws. Now I make the feet with some large dabs of silicone caulk on the underside of the board.

All your work so far looks like it is carefully planned and thought out, so I hesitate to ask if you have the right tools to reach in through the woofer hole and drive in the screws to hold down the crossover board. I'm gonna guess that you have this figured out too.

I'll be looking and learning as you work with HPLV spray to finish your cabinets. I've never done that. I also have Bob Flexner's book on finishing that Alex mentioned. Everything I know on the subject comes from that book.

It is awsome that you have the Tritrix! I am eager to hear your comparison of it and the ER18s. The SEAS and Fountek drivers should easily outperform the budget Dayton drivers in the TriTrix, that is no contest. But I am most interested in a comparison of the bass performance. There is a debate among transmission line DIYers about the relative merits of Martin King's mass-loaded TL (as in the ER18 design) vs. the more traditional type that comes with the TriTrix kit. I'm looking forward to that.

 

[highfigh]

HVLP doesn't provide the same blast of air and finish of a conventional spray rig, which is a big bonus if the gun is set correctly. Drips can happen but with an HVLP or even a conversion gun, it's less of a problem. If spraying up, down or on an upward/downward angle isn't going to happen, standing a piece of MDF or whatever vertically will act as a good test piece.

I bought a cheap conversion gun at Harbor Freight, just to try it and see if it would work for occasional jobs that I didn't want to hand-rub or brush-on and I shot my upper kitchen cabinets with it. No drips at all. Overspray still happens but I didn't set up a booth, either. That will change next time I need to spray anything since I don't have a separate space to use as a shop (I use my garage). I have sprayed MinWax polyurethane varnish, latex paint and shellac with mine and it always works well. The problem I have is moisture, even when using an in-line filter with dessicant and a small one immediately ahead of the gun. I'm doing a job that's part of a 3rd floor rehab and the painter has a Triton true HVLP setup with a turbine air pump and there's almost no over-spray at all- the finish looks great and it isn't terribly expensive. I may be getting one of those. The cabinets at another job were sprayed with an Accu-Spray gun, using pre-cat lacquer, something I want to start using.

 

[skyline_123]

I used to buy those stick-on rubber feet and attach the board with a few screws. Now I make the feet with some large dabs of silicone caulk on the underside of the board.

All your work so far looks like it is carefully planned and thought out, so I hesitate to ask if you have the right tools to reach in through the woofer hole and drive in the screws to hold down the crossover board. I'm gonna guess that you have this figured out too.

Good advice on the silicone feet. I guess I'll just drill a hole on each corner of the crossover board, build up the silicone on those holes and after it sets up, screw them into the side wall with a right angle drill or a short screw driver.

It is awsome that you have the Tritrix! I am eager to hear your comparison of it and the ER18s. The SEAS and Fountek drivers should easily outperform the budget Dayton drivers in the TriTrix, that is no contest. But I am most interested in a comparison of the bass performance. There is a debate among transmission line DIYers about the relative merits of Martin King's mass-loaded TL (as in the ER18 design) vs. the more traditional type that comes with the TriTrix kit. I'm looking forward to that.

The TriTrix build is a gift to my mother. I built her a nice computer with 2TB's worth of storage and will rip all her music to the hard drive. It drives me insane when I go over to her house and see CD's scattered EVERYWHERE. I will be using the Sherwood RX-4105 to power the TriTrix.

HVLP doesn't provide the same blast of air and finish of a conventional spray rig, which is a big bonus if the gun is set correctly. Drips can happen but with an HVLP or even a conversion gun, it's less of a problem. If spraying up, down or on an upward/downward angle isn't going to happen, standing a piece of MDF or whatever vertically will act as a good test piece.

I bought a cheap conversion gun at Harbor Freight, just to try it and see if it would work for occasional jobs that I didn't want to hand-rub or brush-on and I shot my upper kitchen cabinets with it. No drips at all. Overspray still happens but I didn't set up a booth, either. That will change next time I need to spray anything since I don't have a separate space to use as a shop (I use my garage). I have sprayed MinWax polyurethane varnish, latex paint and shellac with mine and it always works well. The problem I have is moisture, even when using an in-line filter with dessicant and a small one immediately ahead of the gun. I'm doing a job that's part of a 3rd floor rehab and the painter has a Triton true HVLP setup with a turbine air pump and there's almost no over-spray at all- the finish looks great and it isn't terribly expensive. I may be getting one of those. The cabinets at another job were sprayed with an Accu-Spray gun, using pre-cat lacquer, something I want to start using.

Do you thin the polyurethane with anything?

 

[skyline_123]

I made a little progress tonight with the HVLP gun. A friend of mine that let me borrow the paint gun went with me to Napa Auto Parts to get some good primer and paint for the enclosures. I started to purchase a quart of primer and a quart of paint but after the clerk so pleasantly informed me that my total was going to be $120 bucks, I decided to work with what I already had in the garage.

Surprisingly enough, and to all you wood finishers out there please don't flame me, I had relatively good success with using a latex primer thinned down with water (about 60% primer and 40% water) and a 1.3mm tip at roughly 25 psi. I put 2 coats on tonight and I feel like it turned out well. I think I will sand them before putting a third coat on though.

The lighting and camera are terrible but you get the idea. It's a lot rougher than I hoped for but I think I can manage. I hope once I build up the primer I will be able to sand it smooth before paint.

 

[highfigh]

Good advice on the silicone feet. I guess I'll just drill a hole on each corner of the crossover board, build up the silicone on those holes and after it sets up, screw them into the side wall with a right angle drill or a short screw driver.

Do you thin the polyurethane with anything?

If the crossovers are heavy, think about using Goop if they'll never move from their final position. It sets harder than silicone and if you know what Shoe-Goo is, it's the same thing. A little goes a long way with that stuff.

I thin it 50% (less if it's hot out) with Naptha, after talking to some painters about what to thin it with. According to them, it skins over faster and that's one of the things that keeps dust from causing nibs, lumps and fish eyes. My kitchen cabinets needed nothing after I sprayed them. It's not as smooth as some of the ones I have seen on job sites but they do it all the time and have a spray booth with filtered air, unlike my place.

If you use any thinner like Naptha, lacquer thinner or acetone, get a good respirator mask with charcoal filters. The label will show which materials the filters are for-look for VOC (Volatile Organic Compounds) in the specs.

 

[Alex2507]

I thin it 50% (less if it's hot out) with Naptha, after talking to some painters about what to thin it with. According to them, it skins over faster

For some reason I seem to remember reading to thin it with 10% mineral spirits in order to keep it from skinning over which allows the urethane under the surface time to complete it's oxygen reactive cure. Thin coats are key and sanding with nothing finer than 220 grit in between coats is required because subsequent layers need a tooth to bond mechanically.

For dust control sweeping and vacuuming the floor, letting the dust settle (over night?) and covering the floor with plastic is recommended. It also protects the floor from overspray. Raising the work as has been done here is good for that too.

Sean, the latex won't sand out. Think of sanding latex gloves. I think that oil base Kilz will sand out but alcohol base Bin Primer is for sure sandable. With a shellac finish you don't have to sand in between coats. You may need to skim out the rough primer if it is like orange peel but if you have a dry spray condition sanding may be enough to get you an acceptable result. Holding the gun too far away causes under atomization (dry spray) and holding it too close causes under atomization (orange peel). My friend Eddie says he has gotten excellent results spraying latex on cabinets. He says holding the gun 6" away works best for him with a turbine.

I've never heard of using automotive paint on wood. Who knew that stuff was so steep? Anyway, the spay job looks fine in the pic's and the practice you obtain with the prime coats will be of benefit in the finish coats. I didn't read the entire thread because a lot of it is outside of understanding (way to go ) but I don't get where the urethane fits in with latex paint ... a protective clear coat?

 

[Alex2507]

Holding the gun too far away causes under atomization ...

Whoops, that should read over atomization ...

 

[highfigh]

For some reason I seem to remember reading to thin it with 10% mineral spirits in order to keep it from skinning over which allows the urethane under the surface time to complete it's oxygen reactive cure. Thin coats are key and sanding with nothing finer than 220 grit in between coats is required because subsequent layers need a tooth to bond mechanically.

Sean, the latex won't sand out. Think of sanding latex gloves. I think that oil base Kilz will sand out but alcohol base Bin Primer is for sure sandable. With a shellac finish you don't have to sand in between coats. You may need to skim out the rough primer if it is like orange peel but if you have a dry spray condition sanding may be enough to get you an acceptable result. Holding the gun too far away causes under atomization (dry spray) and holding it too close causes under atomization (orange peel). My friend Eddie says he has gotten excellent results spraying latex on cabinets. He says holding the gun 6" away works best for him with a turbine.

I've never heard of using automotive paint on wood. Who knew that stuff was so steep? Anyway, the spay job looks fine in the pic's and the practice you obtain with the prime coats will be of benefit in the finish coats. I didn't read the entire thread because a lot of it is outside of understanding (way to go ) but I don't get where the urethane fits in with latex paint ... a protective clear coat?

I have read all kinds of recommendations for thinning and have tried some of them- the Naptha worked best and it was smoothest because is does skin over. The solvents will evaporate regardless but if the surface skins over, dust won't be as much of a problem.

Sanding latex primer works but it has to be really dry and it has to be done slowly- Kilz works really well and that's what I used on my trim with great results.

As far as car paint on wood- if you see a Fender electric guitar from the early '50s until about the middle '60s, all of the colors (except sunburst) were car paint.

 

[skyline_123]

Well, it's been a while since I've posted any updates. I've been experimenting with finishes and I believe I've been somewhat successful. The two biggest accomplishments I've made in the past couple weeks are

1) Shooting primer and paint using the HVLP gun.

2) Obtaining a high gloss polyurethane finish.




The black paint I used is an acrylic, latex based, high gloss enamel. I was VERY pleased with how they came out but I was really wanting a high gloss clear coat finish. It took me a while to the water to paint ratio just right (I'll post the exact ratio next week when I get home from Utah). I started my experimenting with a 50/50 water to paint ratio on a test piece. 50/50 was way too much water and ran almost immediately. The problem I ran into, and you'll see it in the first picture below, is that the closer and closer I was to the optimal ratio, the longer and longer it took for the paint to run. So in the first picture, the ratio was just a tad too watery and even 15 minutes after I shot my test, the paint was fine so I decided to shoot one enclosure. Well, shortly after I shot one enclosure, I look back at my test piece and sure enough, the paint was running. Luckily, I did get it right. Here are some shots.

Here, I simply wiped off the paint and sanded with 220 after it dried sufficiently (it really looks worse than it is).

Here, the paint has finally dried and I am really satisfied with how it turned out. You can see the reflection of the bed in the paint. Enamels are known for being pretty durable but because this is a latex based paint and not something more ideal like oil based enamel, it is still not very scratch resistant.