Measuring drivers with a multimeter? Question about Fl FH

[NickZ]

I'm waiting for my microphone bits so I thought I would try using the multimeter. This is the website I'm following along with.

Measuring Loudspeaker Parameters

I think I'm doing fine until I hit

"Complete the measurements for Fl and Fh, for which the voltage across the source resistor is equal to Vr"

Okay if I understand this I change the frequency until the voltage read on the meter is equal to Vr. Fine. But what are Fl and Fh? I thought at first I would just measure the frequency like I did for Fs. But that's only one number not two.

Now less of a problem but still a wonder for me.

"First, measure the resonant frequency. Adjust the frequency until the voltage across the resistor reaches a null (minimum level)"

Just how low should I go. I can get it down to the point my meter is the issue. But I'm doubting 13500 is the frequency for the midrange I'm testing. So how low a minimum level do I need?

[owdi]

13,500 sounds very wrong, you have passed the impedance peak. Voltage is getting lower because after a point the impedance of the voice coil rises with frequency. If you're measuring a midrange the voltage drop and impedance peak should be somewhere between 40 - 1000hz.

Dan

[richie00boy]

Fl is the frequency below resonance where the voltage is equal to Vr, conversely Fh is the frequency above resonance where the voltage is equal to Vr. The span will not be more than about a couple of octaves from Fl to Fh, e.g Fl = 23Hz, Fr = 47Hz, Fh = 84Hz

[NickZ]

Thanks to you both. Makes a lot of sense.