Re of a Driver- How to measure

[dumrum]

I have a couple of new woofers with me and would like to measure the exact Re value for the driver. Earlier when I used a less expensive Multimeter, I got a value of 7.6Ohms for the 8 Ohms marked woofers.
Now I got a new, more expensive Multimeter , but when I try to measure Re across the Woofer terminals, the value just keeps on fluctuating from 5 Ohm to 8.5 Ohms.
I cannot figure out what the exact value is.
Kindly help with where I might be wrong, or any other means to measure the Re value for the Driver.

Regards,
Linoj.

[phase_accurate]

the value just keeps on fluctuating from 5 Ohm to 8.5 Ohms.

Assumed that you always measure the same driver and that it is basically OK:
Contact resistance can be somewhat critical when measuring low valued resistors (what you actually do here). Make sure that you have a good contact between measuring tips and the drivers spades/clamps. Though not very elegant, I sometimes scratch on the connector of a device I want to measure (in order to remove oxidation), until the readout is consistent.

Regards

Charles

[Dazzzla]

the value just keeps on fluctuating from 5 Ohm to 8.5 Ohms.

If it's not a dirty terminal then it might be the driver is acting as a microphone, make sure that there is no cone movement while you are measuring Re.

Regards
DE

[hunter audio]

hi

Share the same iference as Dazalla but wouldnot have managed wording the entire technicality behind it - in this microphone manner

i hope the driver is up - right and not touching the gaskets , ie the cone is free in its travel

the actual way is to measure the coil only and not when its in the mag field thats why the re is specified by the manufacturers
measured - prior assembly

take care

suranjan

suranjan

[Ron E]

The magnetic field has no effect on the actual resistance, but it does complicate measuring because cone motion generates EMF and messes up the reading. You could try putting a small sand bag or a pillow or something on the cone to damp motion and see if that helps stabilize the measurement. The proper way to measure Re is with a locked coil - which you can't do without removing the dustcap.

The problem with most multimeters is that they are not truly accurate to 0.1 ohms. They are accurate to ~1.5-2% of the reading +5 digits in the last position. at 10 ohms, this is +/- 0.6-0.7 ohms.

You can make a 4-wire low ohms rig for $20 or so. These measure voltage drop across the coil when a known current is sent through it.