Anyone have measured ts specs for mcm 15 & 18 pro woofers?

[bknop]

I am looking into making some open baffle speakers using the 15" or 18" MCM pro woofers in either the steel or cast frame variants. Does anyone have any measured ts parameters, as it is comomly known that the manufacturer parameters are often incorrect?
The steel models considered:
18" 55-2984
15" 55-2983
15" 55-3213 4ohm
Cast frame models considered:
18" 55-2964
18" 55-2984
15" 55-2963
15" 55-2983
15" 55-3243 4ohm

Thanks,
Brad

 

[John Busch]

Have purchased several MCM 15, 18 & 21 inch woofers. Not one of them met published specifications. FS, physical dimensions, voice coil size & so on were as advertised. All looked nice, especially for the selling price.
However, the QE and QM values were way off, usually double or in some cases triple the advertised values. As if the magnets were way under charged. Since I play in the world of open baffle, I can work around that. If I had intended to use them in closed box alignments every one of them would have been useless. I contacted MCM on several occasions and they didn't seem to care. Now that Newark owns them, god knows what you are going to get! Caveat Emptor!

 

[bknop]

John, thanks, I figurred the values were a lot higher. Do you have any favorites for ob use? I was suprised when the Mcm site dissappeared, Mcm and Newark have been sister companies owned by Farnell for many years. Also, do you remenber any of the qts values?

Thanks,
Brad

 

[Michael Chua]

I have the 8", 10" and 12" MCM cast frame. Qes and Qts almost double. Very disappointing.

MCM 55-2960
MCM 55-2981
MCM 55-2982

 

[bknop]

Michael,
Thanks for the info. I wish MCM would remeasure them. That 10 inch one you tested, I used to repair some Kustom kpc10 cabs. It worked out well due to decent midrange quality. The cabs were tuned lower to reduce the midbass bump caused by the woofer's high qts though.

 

[Michael Chua]

Hi Brad

Midrange for the 55-2960 is not a problem. It's actually smoother than my Dayton PA200.

All my MCM drivers have high Qts. As John mentioned, the best avenue is to use OB.

 

[bknop]

I agree, I have been testing the mcm 55-2952 12", it definitely sounds good for open baffle, but the cone resonance is around 56.5hz vs 38hz on the spec sheet. Do these woofers need a lot of play to break in?

 

[Michael Chua]

My 12" MCM 55-2982 bass was hard when new. I ran a 30Hz tone continuously for a few days to break it in. After that, it sounded much better.

The Fs will measure lower and the Vas higher after break in.