Amped Up Hemi

I recently upgraded my salad bowl hemispherical speaker with a new amp board, and I’m loving the sound. I get more volume with less distortion.


This 6-channel board (Sure Electronics TDA7498) is significantly more powerful and easier to install than my previous configuration of 3 stereo amps. I had to use a router to make room for the cooling fan, but otherwise the installation was straightforward.

Here’s everything hooked up before I stuffed the innards back in place and fastened the bottom plate.

The DIY orchestra of the future – hemi speakers

In this TED Talk Ge Wang of Stanford geeks out about computer music (hooray!). He talks briefly about the hemispherical speakers used by the Stanford Laptop Orchestra. Their design (using an IKEA salad bowl) informed my hemi speaker experiments here.

I recently bought a 6-channel amplifier to upgrade the 3 2-channel amps I originally installed in the speaker. I’ll post about the new amp as soon as I drop it in.

No more clunky JBL EONs

My JBL EON G2 10s have served me well as a small PA or as monitor speakers, until they suddenly developed a nasty rattle. At first I thought I’d blown a woofer, but a quick inspection behind the grill showed everything was in order. Then I noticed that something inside each speaker was loose–it would make a disturbing clunk sound whenever I moved it. So I pulled the back off (so many screws…) and discovered the toroidal transformer was loose. I applied a dab of Loc-tite, tightened the bolt, and reassembled the speakers. Now they’re rattle free!

Mouthpiece Mashup Mark 2

20140503-172118.jpgHere’s the second-generation prototype of a soprano sax / trumpet mouthpiece hybrid. This was printed on a Makerbot Replicator 2X. I modeled the soprano sax mouthpiece base and appended the geometry of a Bach 1-1/2C trumpet mouthpiece found on Thingiverse. The trumpet cup is a bit roomier than the previous prototype; I think I’ll try a trombone-sized cup next. Here’s the STL file so you can download, modify and print your own.

Whenever I try this mouthpiece on my horn my son yells at me to “Stop that horrible noise!” So it must be working…

Today’s Fun: Diddley Bows

Inspired by Mike Orr’s Handmade Music Factory book I grabbed some scrap wood and empty soup cans and hacked together three diddley bows. They sound a bit like a berimbau crossed with a one-string Resophonic guitar. I’ll post some sounds once I find my way around the instruments. I’ll likely add guitar pickups or contact mics, too.

Cigar Box Guitar


Had a great time building a cigar box guitar under the direction of John Nickel at Nickel Cigar Box Guitar.

Here’s a detail of the piezo pickup that we installed in the cigar box. The small block of wood on the left is later glued to cover the piezo element.

Singing Strawberries at Wired Kingdom

The Wired Kingdom exhibit opened today at the Arts Center of the Capital Region. My piece for musical strawberries, Das Lied von der Erdbeer, is part of the show. The strawberries sing the opening motive from Mahler’s Das Lied von der Erde.

Studio Gets the Treatment – Part 2

This is the second of a two part post about my recent studio remodel and acoustic treatment. Read the first part here.

Once all the acoustic treatment was installed and the furniture was moved back in, I took another series of audio measurements. All my measurements are quasi-scientific, using materials I had on hand: a Max patch to generate test tones, a home-built omni mic, a spreadsheet. I only tested the frequency response for lower frequencies (20 Hz to approximately 350 Hz). I made no attempt to measure the reverberant response of the room (RT60). Given these limitations, the data nonetheless show a clear improvement in frequency response in the room.

Test Results

My goal was to flatten the frequency response of the room, knowing that a perfectly flat response isn’t practical given the dimensions of the room (or of my wallet). The chart above shows a range of approximately 50 dB in the untreated room, with the lowest reading of 51 dB at 122 Hz and the highest reading of 100 dB at 151 Hz. After the treatment was installed the range is approximately halved to 26 dB, from 67 dB at 62 Hz to to 93 dB at 148 Hz.

One unanticipated difference between the tests is the difference in low frequency readings. In the untreated room, my sound level meter registered nothing below 35 Hz. Once the room was treated, the meter picked up readings beginning at 31 Hz. This bass extension may be due to my ad hoc test equipment, but I seem to hear it.

Listening tests in the treated room were revelatory. Overall bass response is noticeably more even. Much more striking for me is how much the stereo imaging has improved in the treated room. The soundstage seems more defined and both wider and deeper. I’m shocked by how much improved even older stereo mixes sound in the treated room.

Listening to the Beatles “A Day in the Life” in the untreated room I felt like I heard the hard-panned mix just fine, despite some muddiness and boominess in the toms. In the treated room, the toms are clearer and more even, as expected, but even the hard-panned stereo image is more defined. Many tracks in the untreated room suffered from the “hole in the middle” syndrome, whereas in the treated room the sounds are more evenly distributed. I noted that Miles Davis’ “So What” seemed to have good imaging between the bass and trumpet in the untreated room. Listening to it with the acoustic treatment installed I can hear more than just the separation between the instruments–I can hear the sound of the room the instruments were recorded in.

Not Going Back

Remodeling my studio disrupted my work and schedule, but the results are well worth it. Even though it seems pedestrian to spend time and money on acoustic panels rather than boutique microphone preamps or the fashionable plugin du jour, I’ll continue to choose the former over the latter. I’ll never work in an untreated room again.