FE127E voice coil inductance for Zobel calculation

[arjscott]

Hi all,

I've finally decided to start experimenting with passive filter components with my FE127Es. This is out of curiosity, rather than the need to "fix up" the frequency response.

A Zobel seems like a good starting point, as it'll make other filters easier to calculate, and aparrently will also reduce the gently rising response of the driver.

I was just about to use MJK's Zobel / BSC calculation spreadsheet to come up with some component values, but I realised Fostex do not specify the voice coil inductance for this driver, it just says "N/A".

Can anyone offer advice? I assume even if Fostex consider the Le extremely low, a Zobel is still worthwhile for my experiements, and required to flatten the impedance.

A post on the full range driver forum states:

I checked my four Fostex FE127E Drivers: 0.257, 0.256, 0.260 and 0.263 mH

Test conditions 1kHz and 150uA. I don't know what the standard test condition should be

Does anyone think these values will be sufficent? As the poster says, who knows what standard test conditions are.

Best regards,

Andrew.

[gmilitano]

Hi,

I measured those values. They are higher than what I was expecting, so I qualified the measurments as you noted. When I put the LC meter on an air core inductor of known value, I get a reading that is very good.

However, I can't help but think that the measured L is a little high. Surely someone else has an LC meter and a FE127E they can check.

Cheers,
Gio.

[arjscott]

Hi Gio,

Thanks for the reply. I should have mentioned who made those measurements :-)

I think I should figure out how to use Speaker Workshop, or perhaps Arta, and do some impedance measurements with various Zobel components in place. I'll start with component values based on your measurements.

An un-educated backwards approach? Yes. But hopefully it will tell me what I want to know.

Best regards,

Andrew.

[gmilitano]

I tried speaker workshop, but getting it going is not trivial. ARTA is much easier to use, but ARTA will not determine L. I don't suspect speaker workshop will measure L.