SevenSixTwo - InDIYana 2018 Coax Design

[KEtheredge87]

Too late to help you now since you've already made the cuts, but I was thinking, could you have fabricated the part by cutting the two thicknesses of MDF separately and then laminating them together afterwards? Its the double thickness that forces the cut to be so long. Or if the second thickness is just to take up volume, it could just be an appropriate sized block sitting inside of the cabinet, you would just need to make it the right volume to occupy in the enclosure.

Hey Skatz,

Those are great thoughts! I had considered some kind of bevel cut - then laminate kind of arrangement. It would probably work out well with the right clamping arrangement. My engineering neuroses drove me to glue then cut so that I was sure the surfaces didn't have some kind of step in there where I glued after cutting. The block for volume is a great simple idea too. Doing things as I have made this fat wall a decent brace too. I'll look for the silver linings in my own craziness

[skatz]

Too late to help you now since you've already made the cuts, but I was thinking, could you have fabricated the part by cutting the two thicknesses of MDF separately and then laminating them together afterwards? Its the double thickness that forces the cut to be so long. Or if the second thickness is just to take up volume, it could just be an appropriate sized block sitting inside of the cabinet, you would just need to make it the right volume to occupy in the enclosure.

[jhollander]

Ah, well, land the panel at the top of the cabinet -30 degree, gives time for a beer. Square off the mid box and vary the insulation, 2 beers, but not nearly as interesting.

[KEtheredge87]

I love it! I'm going to have to build a sled like that!

Question: why is the back of the mid enclosure double wall?

Hey Craig, The only reason the mid enclosure is double wall is because I was targeting specific volumes from bassbox for the coax and woofer chambers, and I didn't want to change my external dimensions to account for it. That extra layer of MDF just fills up some internal volume. I probably could have gone single wall and saved myself a load of trouble, since the math works out to a ~3.8% increase in woofer chamber volume with only one layer of 3/4" MDF.

Alternatively...I'm just a glutton for punishment.

On the sled bits... yeah, it turned out much better than I would have guessed for a 10 minute DIY effort. I used this Wood Working Web video from Colin Knecht as my guide.

https://youtu.be/r4FNdr1VO0M

[PWR RYD]

I love it! I'm going to have to build a sled like that!

Question: why is the back of the mid enclosure double wall?

[KEtheredge87]

...Be careful of kick back!! That small amount of blade through means kick back could be an issue.

Oh, you bet! I looked long and hard at this setup before actually making a cut. In this case, the fence itself actually works like a sled. The MDF vertical fence extension is secured against the DeWalt table saw fence on both sides, and the whole assembly slides forward and backward on the fence itself. Two clamps in the picture are securing a back-stop to the fence that helps push the workpiece forward, and two other clamps are securing the workpiece itself to the sled / fence. Even with this kind of setup, I still stood off to the side as much as possible in case the whole assembly decided to go airborne.

Kickbacks are nasty... I want none of it! Here's a few more pictures of the setup... only a slight repeat of photos.

[Wolf]

I did the vertical method on my table saw when I cut the equilateral triangle sides for the Trichotomy project. Needless to say- it was a 'fun' process as well there too. I wasn't using as thick a board as you have though.
Be careful of kick back!! That small amount of blade through means kick back could be an issue.

Later,
Wolf

[KEtheredge87]

Alright guys, tonight was a great night in the garage First thing I did was make a tall fence extension for cutting panels like John and Kevin suggested. This was super simple and I was done in about 10 minutes. Clearly I was overthinking this yesterday! After dialing in the angle on the table saw blade, I made the first cut and was quite happy to see the blade cut all the way through the material! No need for the belt sander this time (sorry Kevin). As Wolf suggested, a band saw would have worked for this as well, and I did check that out... my 10" WEN bandsaw didn't have enough height clearance to get the 8" wide piece underneath the guide bearings, so this table saw jig was the only way to save me from my own designs!

Once I got the first cut complete, I went ahead and cut the angle on all three back wall pieces I made, just so I don't have to set the jig and blade up every time. From there, I cut an angle on the coax chamber bottom wall piece and custom fit that one into place. After fitting those pieces to satisfaction, I drilled two holes in the rear wall section for wires to pass through, then it was time for glue! Trying to clamp these parts was a bit tricky with the angles, so I used a few brad nails on the angles to help stabilize while the clamps held things down to the wall.

The next big item is the slot port, so I set one up for glue separate from the box. I'll slice a hair off of one end after it's done drying to make sure that I have one perfectly flush surface to glue against the front baffle.

Like I said, tonight was great! Thanks for everyone's input and suggestions to get me over the hurdle!

[KEtheredge87]

Is a link available? I just checked the Speaker Building Bible sticky and didn't a see a link there.

Why yes there is This YouTube video is how I learned to recognize Tom Z before I ever met him in person. He's got a few YouTube videos out there.

https://youtu.be/Wqwvbla7D-g

[dkalsi]

Hey Kevin! Thanks for the compliment. I have watched tomzarbo 's videos on veneer wrapping several times in my speaker building career, and that's exactly the method I intend to use.

Is a link available? I just checked the Speaker Building Bible sticky and didn't a see a link there.

[tomzarbo]

Keith, it's been awhile since I've made those videos and i'm not exactly sure what I used to gain some 'shrinkage' length for the veneer.

The last time I just did this a few weeks ago, I ended up using a length of copper cable... romex type, ground line, un-sheathed. I made a loop at the end of it and hung it up on a nail in my basement workshop for next time.

It allowed for just the right amount of extra veneer for shrinkage. I glued up to a few inches from the seam, and then fit the seam together carefully, then ironed the slight 'hump' in the veneer down flat. This time it came out pretty much perfect.

Good luck brother!

TomZ

[Wolf]

Heck- if you have a bandsaw;
Use the fence and a jig to hold the board at the right angle, and just cut it with the bandsaw.

Later,
Wolf

[Kevin K.]

If you can make most of the cut clean with the Table saw and a jig, finish the cut with the band saw and break out the belt sander I know you have.

[KEtheredge87]

Sometimes the obvious will elude you Keith, John's suggestion should be the fix. I'm digging your project and it looks like they'll be pretty snazzy when all finished up! If you're still planning on wrapping the core of the cabinet in veneer, check with Tom for a video he made on a small subwoofer. Lots of cool little tricks in the video that could be very helpful. Oh, and make sure you use at least a 3/4" radius, 1/2" can be done but increases the pucker factor tremendously.

Hey Kevin! Thanks for the compliment. I have watched tomzarbo 's videos on veneer wrapping several times in my speaker building career, and that's exactly the method I intend to use. I'm planning to hide the seam on the bottom of the cabinets to keep that complete band of veneer look going. Also yes... 3/4" round overs will be used here. I bought some veneer softener for extra insurance with the curly maple going around those corners. May be extra hassle, but then I won't have to worry about any cracking or ridiculous behavior from the curly bits in those corners. I've already given myself plenty of aesthetically driven construction challenges as it is!

[KEtheredge87]

Standing on end and table saw set to 30 doesn't make the cut? Make a 90 degree jig and clamp the piece to it.

Thanks John, I found some jig ideas on youtube for bevel cut jigs that I think should work. I still may be a bit too shallow on my cut though. I'm going after the long side of the 30/60/90 triangle I sketched out, which is 3 inches long on my 1.5" thick wall piece. My DeWalt table saw has 3.125" thick depth of cut at 90 deg, and 2.25" depth of cut at 45 deg. I doubt I would get close to 3" of cut when at 30 deg.

Of course, the only reason I'm using a 1.5" thick wall back here was to really dial in the internal volumes to match what BassBox was giving me. I suppose I could scrap the 1.5" thick wall idea and just add a bit more volume to the woofer section. Not likely I'll ever notice the difference that increasing the volume by 3.8% would make. If you're wondering... that's 0.63 ft^3 original + 0.024 ft^3 by using 3/4" thick MDF instead of the 1.5" glue-ups I made.

Can you tell I'm an engineer???