[thirdeye]

Hi,

Quick question for those who test a lot of drivers... So I realize the 8 ohm spec. is nominal impedance we don't need to get into that.

But I was just measuring two drivers, both identical make / model etc...  for DC resistance.

One keeps reading about 7.4 ohm

The other keeps giving me 6.1 - 6.2 ohm?

Whats going on here other than for some reason these voice coils are an ohm plus apart?

What effect will this have on sound quality or balance between the 2 channels?

What could possibly be causing this?

Neither driver is hooked up to a crossover so should be clean readings.

Big problem is these are VERY expensive German drivers from Avantgarde acoustics!

As of now most testing in the speaker seems to give no indication anything is seriously off, and they are 107 db drivers so this could be difficult to notice from one to the other of course all I have to go on is more or less the ear test.

Thanks

[Russell Dawkins]

Two expensive and nominally identical drivers should not differ that much in DCR. On a typical amp, the driver with the lower resistance should play louder than the other.
To test this out, you could play them face to face with a mono signal with one in reverse polarity and a rheostat or 1 ohm resistor in series with the driver with lower resistance.

You should get a high degree of cancellation if the drivers are identical in sensitivity, and you might find you need to add about an ohm of resistance to achieve that.
If that is the case, I think this is grounds for money back, or at least replacement of the out-of-spec driver.

Experimentally short across the resistor or potentiometer to hear the degree of mis-match.

[RDavidson]

Wouldn't a good SPL meter and some simple white noise tests (done on each speaker individually) tell you if they're off?

I guess you'd also want to do some frequency sweeps since impedance varies with frequency.......in which case my simple test becomes maybe less simple.

[Duke]

I don't really have anything to add.  That's more difference in DCR than I'm used to seeing, and more than I'm comfortable with.  Maybe if they're using very thin voice coil wire to get the moving mass very low there is less margin for error, and different spools of wire could have slightly different thicknesses, resulting in a different DC resistance.