Archive for June, 2009

Installing a Behringer DSP8024 Equalizer and Upgrading Firmware

Monday, June 8th, 2009

I’m interested in faithful audio reproduction on my home stereo, not just sheer loudness; and even if I don’t end up choosing to stay there, I’ve always wanted to start with a flat frequency response — that is, every pitch that’s played back coming out of the speakers (more to the point, reaching the listener) at the same volume.

My Sony TA-E9000ES preamp / processor has a white noise generator for calibrating the volume of the surround speakers — it sends “static” to each speaker one at a time going around the room. Because I can hear a distinct difference in the “color” of the static when it goes from my main front speakers to my center channel, I already assumed that my different speakers are not providing the same reproduction of the signal going into them — which means that at least some of them (and probably all of them) are not delivering a flat playback.

Behringer 8024 digital equalizer

While poking around on Behringer’s web site, I came across their discontinued DSP8024 digital equalizer. It offers thirty-one 1/3-octave bands of graphic equalization from 20Hz to 20kHz — but more importantly, it offers real-time analysis of your audio system. Connect a reference microphone and turn on auto-equalization and it plays pink noise through your speakers and adjusts the EQ to give you flat response.

And because it’s discontinued, I figured a used one would be a cheap way to get into real-time analysis and flat frequency response. Within a week or so I had picked one up on eBay with the ECM8000 reference microphone.

After flattening my room response, the sound coming through my DSP8024 is simultaneously absolutely awful and absolutely glorious.


Recommend a Temperature Logger?

Saturday, June 6th, 2009

Any recommendations for a battery-operated two-channel standalone temperature logger that collects data for a while in the field, then uploads via USB or serial to a computer? If proprietary software is required for the upload, then it’s provided? The whole works for under $150?

Insulating Paint for Bus Roofs

I’ve seen a couple of descriptions of mixing ceramic and glass microspheres into paint for repainting bus roofs, with the claim that it’s supposed to have thermal insulating value. One person actually took temperature measurements before and after — but acknowledged that he was going from a schoolbus-yellow roof to white, and the increased albedo obviously helped slow heat absorption into the bus as well.

I have a hard time imagining how — in the paint thickness and mixture proportions described — the microspheres could have much of an insulating effect. It seems as though there must be a whole lot more brittle than peanut, and the heat would go right through the brittle. But I’m willing to be convinced.

The Proposal

Converted schoolbus, front

Let’s do the empirical test of insulating microspheres on a bus roof. Half of my bus roof is already an extremely light grey that looks white. I want to paint it white. I’ll even pre-paint the purple roof edges white for the sake of the test. The magic spheres are relatively inexpensive and I’m willing to try them in the “real” roof paint job.

Help me find a two-channel temperature sensor — or two one-channel sensors — for under $150 and I’ll put one inside and one outside the bus for a month, taking readings every five minutes so we can graph outside and inside temperature. Then I’ll paint the roof with magic spheres mixed in and graph the inside and outside bus temperature for another month and we can compare the two.

Is this a proper test? Care to change the methodology and/or add constraints?

Of Course I Could Build One …

But I have enough things to build right now, I’d rather buy this. ‘Kay?

I Bought a Bus

Tuesday, June 2nd, 2009

For years, I’ve been enthralled with the idea of buying an old schoolbus, ripping out the seats, and converting it approximately into an RV. While in college, I thought it should have a B/W darkroom and that I should cross the country taking and printing photos; but today film is out of fashion and I’d rather it have an electronics laboratory (that’s “la-BOHR-a-tree”).

Converted schoolbus, left front

My dream appears to be taking shape in reality. Last week I won an auction for a half-converted former schoolbus previously owned by a university athletics fan and used as a tailgate bus. It already has the seats removed, potable and waste water tanks plumbed, and many other interesting “features.”

I’ve started a new schoolbus conversion blog to describe the project. I’ll cross-post to the electronics blog only when work pertains to electronics; so if you’re interested in the schoolbus conversion in general, you should subscribe to that blog separately.

Posts will be relatively infrequent as I expect the projects to be larger and take longer.