Monday, April 2, 2018

Walnut Bookshelf Speakers

Finished Product Up Front

Intro

So the guts of this speaker build is basically what I've been using for my mains for the last 6 or 7 years. The tweeter is a Bohlender Graebener Neo3-PDR Planar Tweeter and the woofer is an Aurum Cantus AC-130MKII. I'm still amazed by the AC's ability to be detailed and dig down lower than any 5-1/4" driver has any right to.

Those were in a Mass Loaded Quarter Wavelength Tube (ML-QWLT) and had an F3 of 33Hz which is pretty stellar for a little 5-1/4" driver. I have been meaning to redo the cabinets for about 5 yeras, but never got around to it since even though they were ugly....


they sounded great. Now that I have a few actual woodworking projects under my belt I thought it was a good time to revisit the idea of making them "pretty". 

I had never used veneer before and thought it'd be a good idea to work on something smaller than a tower for my first attempt. I had the speakers but not the crossover parts on hand to make a second pair so I thought I'd build a pair of bookshelf sized speakers for the rear channels and then move on to making the towers.

So now that that's out of the way....

Drawings/Modeling/etc.

Modeling the box itself for a vented alignment, ended up around 11.4L (.4ft³) tuned to 46Hz I'll have to do a sweep to see what it is actually tuned to... I didn't get all fancy and figure out things like bracing volume and such. My ear says they started dropping off around 50Hz so it should be fairly close. This was modeled in "Unibox" which is just a free and powerful excel spreadsheet fairly commonly used on the speaker building forums.

Now that I had the appropriate box volume and port sizing I could figure out overall dimensions. The original design for the XO called for a 10" wide baffle, but I did a little bit of modeling and the frequency response wasn't too too effected by going slightly narrower. Window bracing is ~1" wide all around and rounded over. The bracing will make a bit more sense later

Electronics

I designed these a few years back and can't seem to find the response curves or my original crossover files but here are the schematics and general layout of the board. The tweeter is reverse polarity.



It's a fairly simple 3rd order on the tweeter with some padding to bring it's sensitivity down to match the woofer. 3rd order on the woofer too with a baffle step compensation circuit.

The finished boards

And underside of the board, my soldering "skills" aren't great, but hey, it works.

Build

This was a pretty straight forward build, didn't really get any assembly pictures of the main box since it took about 15 minutes to cut everything and assembly was less than an hour or so. I did end up using 16GA brad nails for assembly which was more because I wanted to use my new toy than actually having a reason to do so. I drove them beneath the surface and back filled with wood putty to get it flush. All the material is 3/4" MDF.

This is the brace that sets inside the cabinet in the front, I just eyeballed where the windows should be and used a fostner bit to get radius'd corners. 

Cut the rest of the window with a jig saw

For the front baffles I used a combination of walnut, tiger maple, and "rosewood". The rosewood isn't true rosewood, but some species from the Solomon Islands near New Guinea that I got for free. It seems to be in the sapele family? Idunno but it's pretty and I had a piece that was too thin to really use as anything but an accent so here it is.

Laying out the speaker geometry to flush mount the woofer. I tried to mark the start/stop points as well as I could.

First step was to cut the radius'd corners, used a circle jig for this part and carefully stopping at the start of the straights.

Which was kind of a pain since this is the window I was looking through...

After the corners were done I did the flats with an edge guide.

For all these I would go to one side of the cut, plunge to full depth and go back to my start point do a full plunge there and do 3-4 shallow passes along the rest of the cut. Having the full depth already done on the ends of the cut meant that I didn't have to hit my "stop" point perfectly every time, just on the first plunges.

and then the inner section where the speaker would rest on again with the circle jig

along with the through hole. In total I think this actually took longer than the entire cutting/gluing/etc. of the main cabinet

Using the edge guide again I roughed out the hole for the tweeter, since all that was hidden I wasn't too exact and did a lot of it by hand if that wasn't readily apparent.
  
I wanted a fairly shallow chamfer on the sides so broke out the hand plane

 Forgot a few pictures here, but I taped down the baffle to the box with painter's tape and used a drill press to locate the 6 screws that hold the baffle on the front. That way if any of the holes were off it'd be "wrong" on both the baffle and the rest of the box and still work.

This was a test fit of everything you can see some inconsistent gaps around the woofer, might have to try and dial that in for the towers.

on the interior brace I put in some threaded inserts (get these from McMaster-Carr, they are nearly 10x more expensive if you go to Lowes/HD) using my through holes as guides.

You can see here I used a ring around the port since I had to cut the hole after assembly and didn't thing the PVC would adhere very well without it. Normally I'd cut a recess for the PVC to slide into. The brace in the center is also sized (kinda) so that the inside baffle in inset from the main case slightly for weather stripping.

Everything is glued/brad nailed together.

Finishing

After everything was drilled I was ready for veneer, this was my setup and I did one side of each at a time. I picked up some walnut veneer and heat sensitive glue from veneersupplies.com. After cutting a section about ~1/4" larger than the panel I just taped them down to something flat so they don't curl up while they dry which was something I learned on a test piece


Applied a very thin layer of glue on both the box and the veneer using a rubber roller I also got from veneer supplies. I also marked each piece with an orientation arrow so both speakers would match

In about a half hour or so it was dry and ready to be ironed on. I had some cracking issues with my test piece so I wet down the veneer a bit with a spray bottle and that seemed to mitigate the issue for the most part.

Using a utility knife I cut off the excess fairly closely and then used a plane to flush it up which worked surprisingly well. Another method I also used was to lay a plane blade (without the body) flush with the side and use that to remove it. That seemed to be a bit more sensitive to splitting the wood if you weren't extremely careful with grain direction. Might be less of an issue with a less brittle veneer though. This is my first time working with real veneer so I am mostly just talking out my ass...

So this looks like I'm going backwards... which I was.. because spray paint is the devil. The first attempt ended up looking terrible and had some crackling so I used a filler primer and got things a lot more flat and smooth

and still managed to mess it up. I noticed some dust and even though it had been drying for a few hours the cloth I used to dust them off still managed to scrape the paint... 

Moving on... applied my usual few coats of Arm-R-Seal to the veneer (3 coats gloss 1 satin). I also lightly sanded the scratches and fingerprints (that came 6 hours after spraying...) in the paint and just applied some Arm-R-Seal to that as well and it's "good enough" for the back of the speaker that won't ever be seen.


Here is everything wired up and the walls lined with ~1.5" of mineral wool. I put some weather stripping around the face so it seals up when the baffle bolted on.

All that was left was to bolt the faces on and fire them up. 


Tuesday, March 20, 2018

Walnut and Quilted Maple Coffee Table

Finished Product


Drawings

This was the original all walnut/maple design with closed ends

After building my bed with tube steel I decided to go with a more "industrial" look and switched to using 2x2x1/8"angle iron at the corners and 4x5.4# channel for the legs. Overall dimensions are ~4' long and 1'-11" wide height stayed the same at 1'-6" which was based on the height of my sofa

Build Log

Laying out the boards for glue up, at this point I decided to go with an offset stripe of the quilted maple

Planing everything flat after glue up this is the bottom of the piece which has 3 walnut boards apposed to 4 on the top (hopefully this doesn't bother me for ever)

Just a dry mock-up after some of the main boards were cut to see if I liked the size and proportions

Noticed that after glue up there was some cupping in the panels, probably should have jointed the boards before glue up, I'll do that from now on especially on these wider glue ups, it wasn't ever really an issue on smaller ones.

Enter Big Bertha, I had just got her (which tells you how long this whole shebang took) and decided to use this to fix the cupping issue. 

Worked pretty damned well I'd say

Used the table saw to some some loose tongue and groove for the drawer casing, will have to be a bit more precise in the future on these

Adding the dowel holes for the side panels to attach to the base and top


Hand scraped everything, and after my hands getting tired of holding the blade in a cup made a little holder jig which made things so much nicer

This is why I don't sand anything remotely figured, left is sanded, right is after hand planing, you can see how the luster just dies when it's sanded rather than cut with an iron

Splashed some mineral spirits to get an idea of finish because I'm impatient

All the drawer casings were finished before glue up to ease the finishing process. It would have been a pain in the ass to get to these after everything was assembled.

Setting up the masking for the spots that will eventually be glued

After a few coats of Arm-R-Seal, 3 coats of gloss followed by 1-2 coats of satin I believe

Showing off that figure

And how the figure changes depending on the lighting

So... some creative clamping going on, masked off the areas where there might be some glue squeeze out to so clean up was a ton easier. 

So this is the point where I started needing to make some Christmas presents and the project was on hold for... 3 months

Fucking shit up with my dovetail jig. Note to self: never use a dovetail jig on ply that has a super thin veneer on the outside... it won't go well. Ended up re-cutting everything and just doing glued/screwed butt joints

I had originally planned on doing two "legs" out of C Channel going along the short length of the table, but then decided to do 4 going in the opposite direction. I don't really have metal working tools, but had heard about these blades and it did wonders 

So this was my "trick", after drilling the clearance holes in the channel on the drill press I used the same sized brad point bit to mark the center points on the wood using the leg as a template

Kind of hard to see in pictures but you're left with 5 pinholes that mark where you need to drill on the base.

This was my 5 minute jig for making straight-ish holes to the proper depth. I just cut up a 2x4 and drilled a hole with a drill press and then set the depth stop on the bit to the proper depth. Left the center open so I could see what the hell I was doing.

The inserts I was using had a tendency to split out if you did a fairly tight clearance hole so I chamfered them a bit

Then installed the 10-24 tapping inserts with an Allen key bit on the drill

I guess I didn't take any pictures of the angle iron fab, but they were already cut to length I just drilled clearance holes and chamfered them so the hardware would sit flush. On the table I just drilled a hole slightly undersized of the 10-24 bolts rather than using inserts as the holes in the angle weren't too too accurate partially because of me learning what not to do with a drill press and partially due to the press having some slop in the spindle. A few days after I had everything done I found out that the collar holding the spindle in place had worked itself down after 70 years of use, so it was just a matter of tightening that up... but I digress. 

After sanding everything smooth-ish I applied some gun blue to darken the raw steel back up, I wanted to keep a bit of the rough surface so mostly just got rid of the extremely rough parts and any rust/markings.

So back to woodworking! Cut the drawer fronts to the proper size (I had a big panel that matched the top/base that I had planned on using for the whole endcap) and then added chamfers by hand since I wanted something a bit shallower than a 45 degree bevel

On the back side I routed channels for the drawers to be set in and a lip on the bottom side to open the drawer with since I didn't want a drawer pull at this point, though I may change my mind in the future. The slots for the drawer were done before the chamfer so it didn't want to rock under the router.

Finished drawer before mounting

Installed. These were Centerline soft close drawer slides, I had read how much of a pain they were to get dialed in, the first one basically worked on the first try and I thought "well what the heck were these people complaining about" little did I know the second one would be a royal pain in the ass.

Threw some edge banding on, which it color matched a bit better but I doubt anyone will notice but me and I'll only be getting into these drawers every few months at most.


Finishing/Glamour Shots

Sorry... I may or may not be obsessed with all the figuring in these pieces... bear with me






And finally! The completed table!



In its final resting place