diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Multi-Way (http://www.diyaudio.com/forums/multi-way/)
-   -   Doug's Abbey build (with veneer) (http://www.diyaudio.com/forums/multi-way/147035-dougs-abbey-build-veneer.html)

DougSmith 6th July 2009 02:30 AM

Doug's Abbey build (with veneer)
 
After much research and deliberation, I decided to build a pair of Earl Geddes’ Abbey speakers for my sound system. I chose the Abbeys because of the positive owner feedback (also from owners of other, similar, Geddes speakers), flexibility in terms of room placement (being CD waveguides), dynamics, reasonable cost, and ability to double as live music and recording monitors. This first post is a bit long because I waited until the project was well along before starting this thread (otherwise there would have been some long gaps since I tend to work in small increments on weekends and evenings). I noticed a number of people asking about veneering the Abbeys on this forum and others, so I thought I would describe how I did it.

Building these speakers was a bit of an adventure – I hadn’t tacked a serious woodworking project for quite some time – but I figured it would be worth the effort so I went ahead and ordered the kits. I decided from the outset that I would veneer the enclosures instead of painting them (the latter being the usual approach), but the design (with large radius roundovers on all but the back corners) presented some challenges. I originally planned to veneer each panel separately and then join them at the corners with rounded hardwood pieces (after trimming off the ends of the MDF panels provided in the kit). An alternative approach, that Earl suggested would be to wrap the veneer around all four sides, joining the ends at the bottom. The latter approach sounded better, but I wasn’t sure it would be possible to bend the veneer across the grain. After reading up a bit on wood bending I decided to give it a try. I planned to combine this with a 1/8” groove where the front baffle meets the side panels so I could stretch a grill cloth over the front baffle and use a spline or filler strip to hold it in place.

For the veneer I chose hickory because it had a nice appearance and grain pattern. Another reason was because it was available in wide pieces, 9 feet long, and it is among the more flexible wood species (according to Fine Woodworking’s book on wood bending). Other highly flexible woods listed there include oak, walnut, beech, elm and (less so) birch. Interestingly, temperate hardwoods as a group are much more bendable than tropical hardwoods such as mahogany or teak. Perhaps this has something to do with the compounds temperate trees produce to protect them from freezing. One nice thing about using these woods… no worries about supporting the destruction of rain forests.

To create the groove to retain the grill cloth, I cut a ~1/8” square rabbet in the front edge of the side, top and bottom panels on the table saw. I continued the rabbet around the rounded corners by making several passes while gradually lifting up the opposite end of the panel to ~30 degrees. I then test-fit and glued up the enclosures (with Tightbond II), using the pocket screws provided in the kit and subsequently plugged the pocket holes with 3/8” dowel pieces (as suggested by Mike Galusha on AudioCircle). I added some mitered glue strips to the inside edge of the baffle joints to provide some extra strength (since I reduced the glue area a bit by cutting the rabbet). This may have been superfluous, but it seemed like a good idea. I then added 3/4” square oak landing strips for the rear panel and cross braces, and secured them with glue and screws. I added an extra cross brace for the sides, which might also have been superfluous but I thought it would help reduce enclosure resonances a bit. I smoothed out the joints at the corners, screw holes, etc., with wood filler and put a few coats of Zinser BIN sealer on the baffle (masking off the sides). The result can be seen here:

http://www.dougsmith.lisalandy.com/myalbum/inside.jpg

I added some 1/2” MDF constrained layer damping (CLD) pieces to the inside of the side, top and bottom panels to further reduce enclosure resonances, as per Earl’s suggestion. I used polyurethane caulk to create the constrained layer and to adhere the panels (“PL door, window and siding sealer” – this material bonds well to MDF and remains permanently flexible (like silicone), although it was quite stiff and hard to apply with a hand caulking gun). Earl suggested a two-part polyurethane, but I used the PL material since it was inexpensive and readily available locally. After adding the CLD panels, I waited a few days before sealing the inside of the cabinets. Here is a picture of the interior of the cabinets after adding the CLD panels and sealing:

http://www.dougsmith.lisalandy.com/m... after CLD.jpg

I also applied some black acrylic enamel (spray can from an auto supply store) to the front baffle.

http://www.dougsmith.lisalandy.com/m...ted baffle.jpg

I started the veneering work with the narrow strips for the rear edges of the enclosure and the edges and surface of the rear panel. This gave me a chance to get used to the “heat lock” glue and iron-on technique on the less important part of the cabinets. Generally, the method worked quite well (applying glue to both surfaces and letting it dry before bonding them together with a hot iron). The main thing one needs to be careful to avoid is overheating the panels, which causes small stress cracks to appear. I trimmed the edges and removed the veneer over the pre-cut binding post holes by marking the center from the back side and carefully trimming with a razor knife. The rear panels and corners are shown here:

http://www.dougsmith.lisalandy.com/m...rear panel.jpg

http://www.dougsmith.lisalandy.com/m...rap-around.jpg

Next I prepped and applied glue to two large veneer panels and both cabinets for the wrap around veneering.

http://www.dougsmith.lisalandy.com/m...ting dried.jpg

I taped a piece of parchment paper to one end of the veneer on the glue side after drying to prevent it from sticking to the enclosure prior to cutting the final seam. I was very concerned initially that it would be difficult to bend the veneer around the corners until I tested a couple of scrap pieces (with glue on one side) – I found that these could be easily bent to a 1/2” radius or so without cracking. I proceeded to iron on the panel (parchment end first) starting at the lower part of one side and bending around the bottom corner first. Initially I used way too much steam with the iron, which caused the panel to buckle, but I was able to fix that with a hair dryer (good to have one handy). I ended up dispensing with the steam altogether, however, since it was not necessary to achieve a smooth bend around the corners. I proceeded to bond each side and consecutive corner, working my way around the enclosure, and used a straight edge and razor knife to cut the overlapped ends and create a tight seam at the center of the bottom panel. Here is a picture of what the process looked like before going around the final corner and making the seam…

http://www.dougsmith.lisalandy.com/m...sk at join.jpg

I trimmed off the excess material at the sides with a razor knife, being careful to cut in the direction that would best avoid splitting the veneer at the edges. Trimming the edge flush along the inside edge of the groove was a bit of a challenge... first I cut off the excess at the center of the groove, then I trimmed it flush on a second pass. It was impossible to avoid nicking the black paint on the edges of the groove, but that was easily repaired later (in retrospect, it probably would have been better to paint the baffle after veneering). The final results are shown here:

http://www.dougsmith.lisalandy.com/m...ming edges.jpg

http://www.dougsmith.lisalandy.com/m...dge detail.jpg

I am currently ~2/3 of the way through the finishing process, which has been a bit of a learning experience in itself. The finish is coming along pretty nicely according to what I had in mind, but I would do some things differently if I did this again. For example, I would avoid using a brush-on shellac based sealer on top of aniline dyes – it creates great color, but leaches out the dye a bit, making it hard to avoid lap marks… the alcohol in the shellac also interacts poorly with Rockler “Wonderfill” wood filler – it soaks through the wood causing the filler to shrink slightly). Here are some shots after the second top coat (I will switch from gloss to satin for the final coat or two – to avoid that “plastic look”).

http://www.dougsmith.lisalandy.com/m...other side.jpg

http://www.dougsmith.lisalandy.com/myalbum/one side.jpg

Still a work in progress… more updates to follow.

-Doug

PeteMcK 6th July 2009 10:24 PM

Nice work Doug, wish I had the patience & skill to build something that good.
As a matter of interest, why seal the insides?

DougSmith 7th July 2009 01:35 PM

Thanks, Pete...

Sealing the inside helps stabilize the MDF against expansion and contraction due to changes in humidity.

-Doug

augerpro 7th July 2009 02:16 PM

What did you seal the inside with?

So this CLD is just some panels attached with caulk? How strong is the bond? Did you clamp it so the layer is very thin? I wonder if you could build the actual enclosure fromt this or would there be too much of a soft inner layer to be used as a structural component?

DougSmith 7th July 2009 04:18 PM

The inside was sealed with Zinser BIN primer. That particular polyurethane caulking material bonds very well to MDF. I tried it first on some test pieces; after 1 day I tried to pry them apart... the MDF separated before the joint would. When I applied the material, I spread it evenly over one surface with a putty knife, then simply pressed the two pieces together firmly with some slight circular motion. I used ~1" blocks to create the right spacing from either the bottom of the cabinet or the center braces (with the cabinet placed upright) and let it cure. The layer ended up fairly thin; ~1/32" or slightly less. The tone of the panel resonance was noticably reduced afterwards - although still present to some extent.

-Doug

DougSmith 22nd July 2009 03:30 PM

These are finished now… My hand rubbed finish came out nicely (final sanding with 1500 grit paper and rubbing with polishing compound). One hiccup with the final stages of assembly was that I had to enlarge the holes for the woofers (Earl said this is quite unusual, but it did happen in my case… the holes were ~3/32” too small). I made a template, clamped it on and used a router with a flush cutting bit to enlarge the holes. A side benefit was that this made the integrated woofer gasket perfectly uniform in thickness (which was not the case initially). I added a 1/8” neoprene rubber gasket to compensate for the gasket material which I removed. In the end this worked out fine. I repainted the baffle and groove satin black after masking off the sides.

I wired the crossovers and mounted the drivers as per the assembly manual (here is how my crossovers looked).
http://www.dougsmith.lisalandy.com/m.../crossover.jpg

I also trimmed off the rounded front bulge of the foam plugs since they would have protruded beyond the baffle. After trimming, the plugs were ~1/4” shy of the baffle.
http://www.dougsmith.lisalandy.com/m...fore cloth.jpg

I used 24 star-head finishing screws to hold the backs on (after careful drilling of pilot holes and countersinks) using some thick rubber electrical tape (“Temflex”) as a gasket to make them airtight.
http://www.dougsmith.lisalandy.com/myalbum/back.jpg

I rolled some window screen spline in the groove (a tight fit) and used a putty knife with a smooth edge to force the grill cloth into the crack between the spline and the veneer edge. The material I used (from meniscus audio) was very strong and held up quite well to this procedure. Going around both speakers in ~1/4 inch steps while pulling the cloth taught was a bit tedious, but worked quite nicely to the cloth securely in place. I trimmed off the excess material with a single edge razor blade, using a mask to avoid nicking the material on the baffle, and went around one more time with the putty knife to push in the cut edge. Here is how they came out:
http://www.dougsmith.lisalandy.com/myalbum/cloth on.jpg

Finally, I was ready to hook them up to my system and listen. The sound??? Terrific! Great detail, dynamics and imaging - and very musical (powered by a Yamaha RX-Z7 receiver). Definitely worth all the trouble!

-Doug

SamL 7th December 2009 12:08 AM

Link to photos no longer work. Have photos been moved/deleted?

DougSmith 7th December 2009 01:56 AM

Maybe my web server was down for a while. They seem to be OK now. (Thanks for looking).

-Doug

SamL 7th December 2009 04:14 AM

Hi Doug,

Still no good. Have the same problem from my office and home PCs. It is not browser related as I've tried both IE and Firefox. I wonder if others from down-under have the same problem.

Pallas 7th December 2009 05:24 AM

The drool leaking out of my mouth indicates that the pictures work fine for me. :)

(OSX/Safari)

Seriously, that's a very, very good-looking approach. May as well hide the drivers if they're in public. Did you check w/ Dr. Geddes before filing down the foam, though? Also, did you do two or three (LCR)?


All times are GMT. The time now is 02:36 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2