ECM8000 Tests (lots of pics)

[germanicus]

BoomieMCT wrote:

Yeah, position errors aside, the delta between my mike and Anthony's stayed the same every time we did different runs. Also the difference between horizontal and vertical was very repeatable.

To add another data point: I've been experimenting with various real time analyzers running on my laptop. While measuring pink noise with my ECM8000 I can clearly see that the 10kHz+ part of the spectrum shifts up by at least 5dB when I point the mic at the speakers, and goes back down when I orient it vertically. The rest of the spectrum doesn't change when I re-orient the mic, and nothing changes much if I move it around without changing the orientation.

[Dennis H]

Hey guys,

I don't get over here often enough. This thread and the ECM schematic got linked over at AVS and I was a bit concerned with the schematic. Siegfried Linkwitz has done a lot of experimenting with the Panasonic capsules and has some DIY designs on his web page.

http://www.linkwitzlab.com/sys_test.htm#Mic

In part, he says:

When the cartridge is connected as described by Panasonic it produces fairly high distortion at moderate SPL's and is marginally suitable for serious recording and measurement purposes. The microphone itself is extremely linear, but the built in FET amplifier stage is not configured optimally.

Fortunately, is it possible to modify the external connection to the FET. This involves some delicate work of cutting a trace on the tiny pcb in back of the cartridge and soldering thin, flexible wires to the standard two hookup points, and making a different connection to the capsule housing.

I noticed that the ECM has the capsule wired the conventional way. Obviously they aren't going to do surgery on every capsule. I wondered if their circuit might overcome SL's objections so I emailed him a copy of the schematic and asked. I received a prompt reply (the guy is a real gentleman) and here's what he says.

Hi Dennis,

This mic will definitely suffer from distortion.

Too bad,

SL

FWIW.......

[vrsound]

The ECM8000 is not alone in this phenomenon. In recording orchestras for film sessions we use the omnidirectional Neumann M150 (or if you can find one the original M50). One of it's characteristics is that the high frequency response is very non omnidirectional past 2kHz. Besides it's amazing sound quality this is one of the reasons it's used so much for the Decca tree recording technique. It is not a cheap microphone costing around $6,000 - $7,000. In the Decca configuration there are always 3 of them (That's around $20k for 3 mics). The M150 was never meant to be a measurement microphone as the frequency response chart shows, but it is also not truly omnidirectional.

If the ECM8000 exhibits this type of polar pattern as well then wouldn't it be correct to say the the horizontal orientation would be the only position that would be correct to measure HF response?

I guess the correct question to ask is what is the orientation for the flattest frequency response?
My guess would be on-axis to the intended target. Not really what you want for a measurement microphone but at this cost, beggars can't be choosers!!

Vince