Project Summary

This was an awesome project I got interested in because of this YouTube video by Tech Ingredients.

Basically all that's happening here taking advantage of some cheap exciters to turn cheap XPS foam panels into speakers.

Since the exciters only output mid-high range frequencies, I had to build a subwoofer box to cover the lower end.

Panel Build

The panels are Extruded Polystyrene foam that I carved into shape with a box cutter and some high grit sand paper. As Tech Ingredients explains in more detail, you want to round off the corners to get a smoother sound. The photo on the right was taken before I began sanding. I was actually able to get a really nice surface finish on the final panels.

Next I used some cotter pins and epoxy on the top surface so I could easily hang the panels.

From there I painted the front and sides of the panels to match the yellow couch we have in our living room.

Finally I attached the exciter on each panel according to the three-fifths two-fifths rule specified by the manufacturer. I had lent my soldering iron to my friend when I made these, so I used alligator clamps to attach the speaker wire to the exciters. To connect ot the amp I just used conventional self crimping banana plugs.

For the record, the exciters I used were the "Dayton Audio DAEX32EP-4 Thruster 32mm Exciter 40W 4 Ohm" which ran at about $20 each. I selected these based on their impedance, to match my amplifier.

Subwoofer Build

Unfortunately, I didn't take many pictures of the build for this because I was in a huge rush to get it done before my housemates got home on New Years Eve. I used this subwoofer volume calculator to get my external dimensions, and used the manufacturer specified volume.

I cut 3/4" thick MDF using a circular saw and some guides, for the baffle hole I used a really terrible harbor freight jigsaw I picked up for cheap. I hindsight I would've ordered one of those comically large hole saw bits for about the same price. It only took a couple hours to glue everything together because I own a ton of clamps in this size range.

I finished the box off with a quick spray paint job on the inside and outside just to kinda seal the MDF since it's not the least carcinogenic material in the world. I didn't go so far as to apply a coat of polyacrylic, because, again, I was in a huge rush to get these done. I will get around to it eventually.

Finally I mounted some rubber feet to isolate the box from the ground, the banana plug terminals, and then the subwoofer.

I went with the "Dayton Audio DC160S-4 6-1/2" Classic Shielded Woofer 4 Ohm" which ran me about $40, and again I chose to match my amplifier. It should be maxing out at about 100W and based on how much my house shook when my housemates had me test it out with some base trap/frat party music, I'd say it can definitely get up there.

Results

Overall this project turned out amazing and was a lot of fun. When I was a kid my parents had a surround sound system and I don't think it ever sounded as good as this. We have the amplifier hooked up to our projector and watching movies at home has never been so good.

I really can't stress enough how good the sound quality turned out. It surprises everyone I play it for, especially when they find out the panels are just made out of $2 XPS. In the future I plan to delve more into the audio engineering behind this, and see if I can quantitively characterize the performance in different ways.

If you have the tools and want a cheap new sound system, I can't recommend this enough as a good starting point.

On the right, I recorded the system playing Allegretto which has been my favorite piece of classical music since high school. Please attribute any issues with the sound quality to the fact that I recorded this with a 3-4 year old phone in probably a suboptimal position. I promise the sound is great in person.