Ready to DIY; starting with a THT low profile sub

I've been wanting to build some speakers or a sub for quite a while, and I am finally in a position to go for it. I already have an MFW-15 driver and a Behringer A500 amp laying around, and now I have a reason to build a large sub with no aesthetic constraints. So I'm going to build a "THT Low Profile" to take to Burning Man this year to give our camp some bass and extra seating (a THTLP seems like it would make a good bench).

I bought a house last summer and finally have the garage organized and ready for a project. I just ordered the THTLP plans, a Makita 5007MG circular saw with a Diablo 40T blade, and a track system and work table kit from eurekazone. I picked most of that stuff based on reading recommendations in this forum -- thanks for the info and inspiration! I know this is overkill for building one sub, but this is just the first of many projects I expect to do so I decided to invest in some tools that will make building more enjoyable.

In 2009, I built this 2001-style monolith / speaker (to play "background music"), but I'm planning to do a better job with the audio on my sub/bench project this year:
https://picasaweb.google.com/playamax/Monolith#

I will update this thread as my build progresses. My goals for this project are fun and function and I don't care what it looks like -- it will be totally covered in dust at Burning Man anyway.

-Max

To ease transport, the monolith was really just PE grill cloth stretched over a frame that I assembled on-site. There were at least two other monoliths that year -- an interactive art piece that let you make music and had a chalk board surface, and another that was a 9 foot subwoofer. Both of those were solid.

Status update: I got the plans in my email today.

-Max

Extension to 20 hz is not a requirement. My selection of the THTLP design was mainly due to the fact that I already have an MFW-15 driver, which I understand works well in the THT(LP) design. And I like the size and shape of the THTLP because I can transport it in a passenger/cargo van and it can serve double-duty as a bench or table around camp. It can also stand up in the garage the rest of the year without taking much room.

That said, 20 hz might make the "sub seats" more enjoyable (or therapeutic, as Rob points out ). And I will probably use this as a "garage sub" the rest of the year, where it might be fun to have a sub that plays that deep for movies.

I don't have a specific SPL requirements -- we aren't a music camp, so this sub just needs to fill in some bass for moderate music in the hang-out area of camp. Higher sensitivity seems like it would use less power, which would be a useful advantage since this will be running on battery power in the evenings.

So, I guess that all boils down to:
* I don't have specific extension or output requirements.
* I like the 18"x72"x(18+ -- I might do 24)" dimensions of the THTLP because it will make a good bench, will be easy to transport in a cargo van, and can stand up in my garage without taking up too much room the rest of the year.
* I already have an MFW-15 driver laying around.
* ALTERNATELY: I also have a 10" driver from the AV123 UFW-10 / ULW-10 that I would be equally happy to use. Does anyone know the specs?
* I'm open to getting a different driver, too, but using one of the drivers that I already have would be a bonus.

Would the MFW-15 driver work okay in a T39 or T48? Or maybe the UFW-10 driver? Are there any other designs I should consider?

Thanks,
-Max

Good points, Andreas. It is decided -- I'm building the THTLP.

I can always build more stuff later if I want to. For instance, it would be nice to have a <14" deep sub that would fit inside the monolith...

Also, Brad -- I just saw the links in your signature and checked out your THTLP build thread -- nice!
http://www.avsforum.com/avs-vb/showthread.php?t=1275894

-Max

I'm not quite working on my THTLP yet, but I made some sawdust today -- I finished my workbench. I attached a pic below.

This post is fairly pointless, I guess, but maybe it will be useful to another new DIYer that is thinking about what tools to get or how to get started.

The workbench isn't specifically for working on speakers, but rather just a good workbench for my garage. The top is 72*37" and it is 36" tall. It turned out nice and heavy, which is just what I was going for. I followed these plans:
http://www.lowes.com/cd_Build+a+Workbench_692759023_

For the top surface, I used 1/2" Arauco ply from Lowes -- the same stuff I will be using for my THTLP build. I had them rough cut it, since the eurekazone track system I ordered won't be here until Monday, and I can't fit 4x8' sheet in my car anyway. Even after my track cutting system arrives, I might have the store do some basic cuts on the ply that I get for my THTLP since it's free, easy, and it allows me to take the stuff home easier. To install the plywood on the workbench, I used a countersink #8 drill bit. The THTLP plans recommend using one of those if you plan to use screws. It seemed like it would be perfect for installing my workbench top, so I picked one up for less than $5. It worked fine, though I wasn't very consistent on how deep I made the countersinks.

I used one of the scraps from the plywood as a guide, and used my new circular saw to trim the ply once installed on the workbench. There was about 3/4" extra hanging over on one side and I wasn't sure how much the router trim bit would safely cut. Maybe the router trim bit could have handled that, but it didn't hurt to get a little practice with my new circular saw.

I then used my new router (Bosch 1617EVSPK) to trim the surface plywood to exactly match the top of the workbench. I used a Freud 1/2"x1.5" trim bit that I ordered from Amazon. This was the first time that I ever used a router. I don't know why, but I always thought of routers as being scary tools for some reason. But it was really easy. I made sure to install the bit correctly and to go the right direction. Easy as pie. No burns or other weirdness. It just worked. I did, of course, have safety glasses on -- well worth the $10 I spent on new ones that look like sunglasses to replace the many old scratched up / uncomfortable ones I have around the garage. I also had on some $4 Harbor Freight ear muffs for hearing protection, which also worked great.

Next I decided to roundover the edge of the workbench surface. I used a Freud (34-120) 1/4" roundover bit. I turned the speed on the router down a couple of notches in keeping with the RPM recommendation on the package. Unlike with the flush trim bit I used in the last step, the depth needs to be set precisely this time. So I made the adjustment on the fixed router base that I was using. I just eye-balled it and then did a test cut on a piece of scrap wood. I thought that I would need to make an adjustment, but the test cut looked great, so I made no adjustment. Then I routed around the whole workbench top. Again it worked perfectly with no burns and no problems -- just smooth operation and the results were excellent. I attached a pic below. I still have a lot of respect for the tool, but I'm definitely not scared of my router anymore.

It seems that a good shop vac should be on the list of "must have" tools for DIY speaker builders -- I'm glad I already had one.

I also found some 4x4' sheets of Oak 3/4" plywood at Lowes today, so I got one of those and had them cut it in half. I'll be using one half as the top for my Eurekazone Smart Table. It felt much stiffer than the other plywoods -- should be good for the table. I also picked up some Douglas Fir 1x4s for the smart table. I wasn't sure what wood to get for the 1x4s, but these boards were pretty straight and they had slightly rounded edges which should be good for my intended usage.

-Max

So I wanted to order some hurricane nuts from Parts Express, but that wasn't enough to get free shipping. As any rational person might do, I decided to add the parts for a pair of EconoWave SR Compacts to my order. I now have two DIY speaker projects lined up.

-Max

I received my shipment of parts for my Econowave SR Compacts from Parts Express. But I'm going to make the THTLP sub first.

However, my only work progress to report is that I made another work table. This time it is a Eurekazone Smart Table from their kit. Check out the pics below...

I mounted the eurekazone base on my circular saw and trimmed the edge / did some test cuts tonight. I also picked up the Arauco ACX plywood for my THTLP build. I've got a busy week, but I am excited to really get started building my sub.

I cut the first couple of panels and did all the layout stuff, and tonight I glued the first panels together. I'm having fun, and my anticipation is building for making some noise with my project sub.

It has been a while since I posted in this thread, but I have been working and taking some pictures.

Here's panel #2 being glued into place...

And panel #3...

Panel #4...

Panel #5

I used the Jasper jig and a 1/4" spiral upcut bit to make the cut. First I used a straight edge and the corners of the board to find the center. Then I screwed on a backer board, both in the center and outside the hole. I used a countersink so that the surface would remain smooth for the router to pass over. This was my first time using the jig and it worked perfectly. I did it in two cuts. The bit moved very smoothly and quickly through the wood, and the hole turned out perfect.

I laid the driver face-down on the board and carefully centered the driver before using a nail to mark the positions for the driver screws. The Eurekazone Smart Table was useful here, because it made it easy to reach up from the bottom and feel if the driver was centered. You could do the same thing with a few 2x4s on a flat table, too.

Then I drilled small (~3/32") starter holes so the drill wouldn't walk around too much before I drilled the 1/4" holes that I needed for the hurricane nuts. You can use t-nuts, also, but I picked up the hurricane nuts from Parts Express after reading some positive reviews. I really like them for this application because they don't dig into the back of the board like t-nuts do. You don't need to cut the driver hole as a bevel -- the hurricane nuts fit with no overhang into the driver cut-out. I've heard that you don't really need to use epoxy with hurricane nuts, but I used some anyway just to be extra safe. I tapped the hurricane nuts into the holes and then flipped the board over and installed the driver to fully seat them before the epoxy dried. That should ensure that I don't need to chase any epoxy out of the threads during final assembly, too.

I bought 1.25"-long 10-32 socket cap screws, but I guess 1" length would have been enough, as they stick out about 1/4". :-) I don't think that will be a problem. I wanted black, but the local store only had silver. And no one is going to see them anyway once the sub is complete.

As you may have noticed, I seem to smear the glue around a lot. I just put on a pair of nitrile or latex gloves before I glue anything, and then smear it into the corners once the panel is in place.

I bought the larger size of PL Premium tubes and a big caulk gun to match. So far I'm still on my first tube after a few weeks of work. I just stand the tube up and wrap the tip with foil when I am done. In fact, I've been using the same piece of foil every time, so it is now like a formed cap made out of PL Premium with a little foil on the outside. This seems to be working quite well. I can easily remove the "cap" and I don't even need to use the poker to get the glue flowing again. So if you are wondering if you can buy the big tube and just use a little at a time, the answer is "yes" -- at least over a few weeks, and possible longer. My first tube doesn't show any signs of drying up yet.

I need to cut some braces and make ~1/2" of clearance for the driver. So I cut the braces and screwed them both to a backer board from the underside. I carefully positioned the backer board so that the edge would be 1/2" from the edge of the brace. This way I can use my flush-cut router bit to cut the driver clearance.

I still think this is a good approach, but I messed up a bit as you can see in the pics. One of the screws was barely poking though and it was digging into the base of the router. I should have known something was wrong when the router wasn't moving smoothly, but I didn't figure it out until after I stopped with the router. Rookie mistake! But now I know.

The braces turned out kind of sloppy but good enough. I think the router base is still functional, too. I'm sure I can get a new base if it proves to be a problem.

Gluing the panel 2/6 braces...

Thanks smokarz.

Yup, just me, internet radio, screws, brads, jigs, and a lot of clamps. This isn't going in my living room, so I can screw up a bit and learn as I go on this without feeling like it needs to be perfect. I think as long as it is air-tight it will be okay. Fortunately (and I think as an intended effect of the THTLP plans), things seem to be coming together where they need to, even though my plywood is warpy and woodworking skills are not finely honed.

-Max

Panel #7 and some braces installed tonight...

Having a piece of angle iron around has been useful as a relatively compact straight edge.

I used brads to hold the bottom of panel #7 in place.