variable impedance voice coil

[valhallax]

when i hook an ohm meter up to most speakers it will read a fairly solid number..ie. 7.1 or 11.6 etc. but when i hook up my ohm meter to my 515, the numbers are all over the place. ive read here that the early ones used a variable impedance voice coil, however i have no idea what this means? or what my amplifier will see this as.

[valhallax]

though this might need to be in a different thread.. i was wondering , only having one set of 515b's for a pair of 210 cabs, i needed another set of 15 inch drivers for the other cab. all i had on hand was a pair of 418b mi speakers..so i threw them in. one speaker reads 7.3 on the ohm meter and the other reads 4.1 ohms..with a combined total of 2.7 ohms. obviously a bad driver, but it'll have to do. kind of a 'run what you brung' deal. running this pair and the other pair into my 9444a amp, will it be ok? in other words, will the two channels of my altec anniversary amp, act independently of one another?

[hmole]

Wandering Ohms indicates a bad connection somewhere, see if you can isolate it, Could be a bad tinsel wire, or a toasted VC, or even an inability to get contact with the probe.
I think if you are running drivers of disparate Ohm you will find one will hog the power, you want them fairly well matched.
You might have more luck amplifying those drivers separately.
Harry

[bfish]

Digital meters often 'go wild' while ohming out woofer VCs when there is signifigant background noise. HE woofers make fair microphones, and the voltage produced by the VC adds and subracts from the meter's internal battery voltage.

[Old Guy]

To remedy the situation bfish mentions, face the driver down on a formica countertop...the gasket will seal a bit, and the trapped air will damp the cone.

[valhallax]

you guys were right..i was testing in front of the air conditioner and after i turned it off. who knew, a little background noise who do that to a woofer? live an' learn