Matt's DIY audio page

Pilar of power subwoofer

It has been awhile since I built any speakers, but I couldn't resist replacing my old subwoofers with my DIY Pillar of Power subwoofer. My wood working skills keep me away from doing too many speakers, but a Sonosub (built from Sonotube) simplifies the building. Sonotube is a thick card board like material that is used to make concrete pillars in bridges and other structures. A cylinder is the next best shape for a speaker. Spheres are best, but very hard to build. In short, you take the sonotube cylinder and add a top and bottom. Mount a speaker, throw in some aesthetics and you are done. The subwoofer is a sealed design using a 15" Tempest subwoofer from Adire Audio. With over 16mm of linear one way x-max, the Tempest can push some air and create some good vibrations. You can find more details and pictures for this project. This subwoofer is one of my projects that still sees active duty. It makes room shaking bass for movies, but is still articulate for music.

Matt's big class A

My senior project from '99, a single ended class A amplifier (right), has been completely posted. The article was published in AudioXpress magazine (September 2003). The schematic, board layout, parts placement, parts list, and detailed article are now up. The amplifier was designed using PSPICE and Veribest (an electronic simulation and layout program now owned by Mentor Graphics). Specs. 20 Watts per channel, three stage architecture (differential input, gain stage, output stage). The International Rectifier IRFP140N MOSFET was used for the output transistor and current source. Pictures and details are available. This was a fun project. It never saw too much time in my stereo rack becasue my "stereo" serves both music and home theater duties. The sound level the amp produced (with reasonably efficient speakers) always surprised younger people who consider 100W/ channel the norm. However, 20W is a little anemic when used for home theaters at "reference levels". It is a very nice sounding amplifier.

24dB/octave Linkwitz-Riley crossover

My latest electronic project is a 24db/octave Linkwitz-Riley hi/low pass electronic crossover at 85 HZ. It is used as the sub woofer I found the Loudspeaker Design Cookbook by Vance Dickason to be very helpful in choosing the type of crossover for the application. The book has graphs of phase and droll off characteristics of many different x-over configurations.The picture shows the finished crossover. Check out the (Add details and pictures section) as well as a close-up picture of the circuit boards.

This was probably my most popular project on my web page. With home theater receivers that have crossovers built-in, this crossover isn't as relevant. This is an active crossover so you need amplifiers after it to drive the speakers (or need pre-amp in on your receiver)

Corcom based power filter

Another project that I have done is an A.C. power filter. A D.I.Y club in San Diego that no longer meets, featured this as a club project.It uses several Corcom type filters, Metal Oxide Varistors, and a large high voltage capacitor to filter RFI/EMI and voltage spikes floating down from the power line.The six large metal boxes in the picture are the Corcom filters which have coils, capacitors and resistors sealed inside them. The three small red discs towards the front are the M.O.V.'s. The A.C. outlets are along the backside and the power switch and circuit breaker are on the front panel. The black square in the front right hand corner is the high voltage capacitor.You can see the (Add details and wiring diagram) of the of the A.C.filter.