Speaker Workshop Extremis6.8 Test Results

[GrahamT]

I set up a SW testing rig in my computer room. I use the Claudio JIG and believe it or not, the Radio Shack SPL meter with calibration file. I'm sure it's not perfect but it's a good enough for me to gain some testing experience.

These are some results from testing the Extremis on a 10x17" baffle. The white graphs are Jon's the grey ones are mine.

Near field





Far field





Impedance





How do they look?

[ThomasW]

Given the inherent limitations of a $50 RS meter compared to Jon's $5000 mic, the plots look pretty good ... :wink:

[Hank]

I'd say amazingly close, given the cost delta. Question for the Pooh-bah's: how much closer would the inexpensive Behringer mic be? That mic seems to be the value proposition in mic's.

[JonMarsh]

Well, I certainly agree the Behringer is a value leader- why do you think I have one, too? I'd certainly recommend Graham look into getting one of those ASAP. But I understand what student budgets are like... and money spent on test equipment is money you can't spend on drivers or crossover parts.

That plus one of the Maudio mic preamps (I use a DMP3) is a good entry level solution- one I recommend unless one is going with Praxis, then you need to use their mic setup for the AudPod.

[cjd]

I found the Behringer and the RS to be rather different, though I didn't have correction info on the RS.

C

[ThomasW]

Hank,

Somewhere there's a thread where Jon compared his B&K to the ECM-8000. The ECM-8000 is a surprisingly good mic. It's weak spot is the extreme top end.

Note that it's the standard mic included when one purchases a DEQX system (price of admission starts approx $2500)

[GrahamT]

This setup is just a ball park rig so I can experiment. The snap shots above are intentionally similar. I figured if my results resembled the known results, then I was doing something right. :W

I do plan to upgrade the mic at some point. It all depends on where I am working, where I decide to go to school, and how much scholarship money I get. As things stand right now, I might buy a DIY mic and preamp kit that some people at DIYaudio.com are working on.

[JonMarsh]

The ECM8000 has a roll off in the extreme treble, above 16 kHz. DEQX provides a very accurate mic cal file with each one. For the purposes of speaker development, it's an interesting question as to whether a couple of dB overall level inaccuracy somewhere in the extreme deep bass or top end is going to affect the results most of us amateurs can produce- particuarly considering the influence of room placement, etc.

The Girardin small diameter electret capsul mic sold by Liberty instruments with Praxis is one of the best low cost solutions if you want accuracy to beyond 20 kHz in the top end, but the small capsule size lowers it's S/N and low bias voltage limits dynamic range a bit. It's a measurement mic, whereas the ECM8000 was originally designed as an inexpensive omni recording microphone, though it has a relatively small diaphram, too. I built a pair of custom mics using AKG 451 capsules back in the 70's; wish I had those still, though I do have a couple of bodies and capsules; may have to build them up again someday. Though I'm sure by now you can buy better at reasonable prices.

[Dennis H]

I heard Kim Girardin will calibrate the Behringer mic for about $40 so that still works out cheaper than buying one of his calibrated mics.