Finishing, Final Assembly, Final Thoughts

I had a bit of trouble getting the stain as dark as I wanted, and trouble with the finish.

Finally the finish is done.  Have installed the handles and wiring.

I should have just stuck with Danish Oil… Its a dusty location and anything else will pick up too much dust as it dries.  I have redone the finish on the front using just Danish Oil and a bit of Minwax. The interior has been filled about 90+ percent with fiberglass.  It will help dampen some of the frequencies, but not really much at the low end (but it can’t hurt…)

January 24, 2011.  My helpers were away so I moved it myself (over 300 lbs).  I used a chain hoist to lower the sub onto a moving dolly, and then easily brought it into the house using a plywood ramp at the front steps, it was not hard!  The handles came in handy.  When my helpers arrived we lifted it off the moving dolly and set it in place.

Here’s the 500 watt amp, which installed easily, and then the driver.  I used a bit of fingertip rope caulk around the inset before installing the driver.  The rope caulk never dries completely and will ensure a good seal.  I had changed the wiring to 14 gauge low voltage wire I found at Home Depot.  That wire is good for all speaker uses, and should be as good or better than any of the expensive commercial speaker wire.

Subwoofer in place!  Eventually it will fit below the TV in my new entertainment center – but that’s another project!  It is sitting on some 1/4 inch felt feet.

How does it sound?

I played all kinds of music, starting with a dozen of my favorite organ works, and then some contemporary music.  The sound is very rich and detailed and yet not harsh even when it’s shaking your bones.  I find I don’t need it loud to hear it clearly!  I’m very pleased.  It’s very satisfying and eye opening, all those octaves I have been missing are now there… although it really shows up the shortcomings of my other speakers!  Well… that’s the next project.

The panel amp performs very well.  It never even gets warm, that’s a nice feature of a class-D amp.  BTW, Parts Express has a new version of this amp out now, although it’s a bit pricey.

Final Thoughts

When my tri-amp surround system is complete I will be driving the subwoofer from the output of a Linkwitz Transform Circuit and an 8-channel equalizer, this will extend the lower range of the sub and allow me to tweak it to a perfectly flat response.  This is one of the reasons I chose the 500 watt driver and amp, it takes extra power to drive the lower frequencies below resonance.

I really enjoyed this project, and I would do it again… it would just be a lot faster now, since I learned so much!

What I would do differently:

  • I would not angle the right wall (which I did to make it easier to access the amp).  It makes the coving difficult to fit.
  • I would also not make a foamed glue layer between the plywood and MDF (as mentioned earlier).  It would be quicker and cheaper to just make the walls thicker – lesson learned.
  • I would  just use Danish Oil and Minwax to finish my next speakers.  That’s nearly foolproof.
  • I would also be more careful to toss any intermediate plan printouts, as I did get a dimension wrong – placing the driver a bit farther right than I had intended.  It still worked out fine tho!
  • I would not use the speaker cabinet handles I got from Parts Express here.  They are not really strong enough for this weight (although they did not break with the very limited use I put then through).
  • I would build a CNC machine first, and use that to help  build it :).

Things I’m glad I did:

  • Planning the project completely before starting, using Alibre Design.  I can’t stress enough how much this program helped me, including printing out the dimensioned drawings.  It’s well worth learning, and only about $100 for full 3d parametric modeling!
  • Read the Loudspeaker Design Cookbook – a must – for all the theory behind speaker performance.

What’s my next project?

I’m working on a variable lab power supply now so I can test the boards I am building for my tri-amp surround system. I have built the PCB and am modding an old UPS chassis to hold it.  I will post pix when it’s ready.  For background on the lab power supply see: Variable Dual Lab Power Supply at Rod Elliot’s excellent website.

I will build one channel for my surround system before I build the speakers.  The electronics for this channel will consist of power supplies, a 4 way active crossover, three 8-channel equalizers, and three amps.  I will post the beginning of this project in a week or two.



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