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Nov 19, 2009

As I’ve mentioned here many, many times, I’ve been selling pre-calibrated Behringer ECM8000 microphones because of popular request, as well as a way to supplement my income. A few months ago, Parts-Express started selling the EMM-6 microphone which is essentially a clone of the ECM8000 (and the Nady CM-100).

Back in September, PE had a $10-off sale on the EMM-6. I bought up a bunch, did my calibration thing and sold them at a $10 discount. Somewhat unexpectedly, this turned out to be wildly popular with customers all over the world. Prices have since returned to normal but I was able to get a volume pricing on the EMM-6 and offered the sale again a couple of weeks ago. Once again, the sale went very well.

When I started selling mics, I never intended it to be a volume business. I typically sell a few every couple of days, maybe a dozen in a busy week. In the last six weeks I’ve sold just under 400 microphones.

Needless to say, I was overwhelmed (and it didn’t help that I had to travel for four days in the middle of the first sale to attend a wedding). Up until recently, the process I used to process each mic was labor intensive and involved several computer programs (ARTA, Octave, Gnuplot, LaTeX), two platforms (Windows and Mac OS X) and several pieces of hardware (Presonus Firebox, Sencore SP395 RTA, GenRad 1986 calibrator, a customized test loudspeaker, a customized low-frequency pressure chamber and a sound-isolation chamber). The polar measurements were performed using a lazy susan with quickly got cumbersome when trying to deal with processing dozens of mics per day.

Obviously something had to give and my delivery times for the first mic sale were pretty abysmal. I learned my lesson - I needed to automate, automate, AUTOMATE! I spent a weekend cooking up ways to script the the measurement and data processing activities. For the on- and off-axis frequency response measurements, I wound up using AutoHotkey to script ARTA to make the swept-sine measurement/file saving activity a one-button activity. I use a Mac for the data processing so I was able to employ AppleScript combined with tcsh scripting to smooth the measurement data in Octave, make plots and generate the LaTeX files. The script also generates the .csv files .FRD files for the data CDs.

Automating the polar measurements proved to be the biggest challenge. I’ve looked into purchasing a turntable system but at $3,000+ for a turntable, plus several thousand dollars more for software, I really couldn’t justify the cost. I had hoped that turntables used for 3D photography might offer a credible alternative, but those are still in pricey.

I finally wound up buying a Meade DS-2000 telescope mount (without the telescope obviously):

polar measurement jig

The DS-2000 is a computer-controlled 2-axis motorized mount with arc-second accuracy. Combined with some serial programing and AutoHotkey scripts I was able to put together an automated polar test suite for under $300. A 360-degree polar measurement (unlike some measurement labs, I don’t just measure 180-degrees and mirror the response, I measure over the full circle) takes about 10 minutes, but the advantage of automation is that I can actually be doing something else while the test is running.

The results have been dramatic. During the first EMM-6 sale, I was processing roughly 6 Premium Plus-type microphones in a day. After automating everything, I was able to process 12 to 15 microphones to day. My last sale involved 70 microphones and I was able to start shipping them out the day after receiving my order from PE and all of them went out in less than a week.

Just are definitely moving along much faster now. The mics come in…

boxes o' microphones

… they get processed…

boxes o' microphones

… and they go out.

boxes o' microphones

I’m now at the point where my bottleneck in shipping microphones is burning the data CD’s and packing boxes. There’s not much I can do to make that process faster, but if things manage to stay busy, I may just wind up hiring someone to take care of that part. We’ll see.

In the meanwhile, if you’re interested in buying discounted microphones, I am collecting names of people who are interested in group buys. When I get 10-12 names, I’ll take orders, place a volume order with Parts-Express, ship the mics and then start the process again. Unfortunately PE is sold out of EMM-6 and won’t have more until mid January but I am looking into getting a group purchase of ECM8000’s instead. If you’re interested in the discount, please sign up.

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