1964 Vox AC30 Celestion Silver Bells measure 11 ohms

[evil79]

Hey guys. So I have an old Vox AC30/6 Treble on the bench, and I just measured the speaker impedance and it’s 11 ohms. That’s 2 8 ohm speakers in series like you’d expect in a Vox. So should I connect the speakers to the 16 ohm or 8 ohm tap of the OT? It’s closer to 8 ohms, but it’s supposed to want 16. Does it really matter when it’s in between like this? OT is an original Parmeko and speakers are original too.

[evil79]

So I read that 16 ohm speakers usually measure between 10-12 ohms. I’ve never had that low of a reading. But according to the internet, it’s normal and I should go with 16 ohms. Thoughts?

[Jon Snell]

Use 8R tap with two 16R speakers wired in parallel and 16R tap for two 8R in series.

[Enzo]

You didn't measure impedance, you measured resistance. Two 8 ohm speakers in series is 16 ohms, regardless of the DC resistance. DC resistance usually measures lower than nominal impedance.

[pdf64]

Hey guys. So I have an old Vox AC30/6 Treble on the bench, and I just measured the speaker impedance and it’s 11 ohms...

How did you measure impedance? It requires a special meter, and for a speaker, will vary significantly according to the test frequency used.
Maybe you meant resistance rather than impedance, the former being lower than the latter. 11 ohms resistance seems a bit low but they’re rare models so who knows. Do both speakers measure the same?
Whatever, without any other evidence to the contrary it’s probably best to assume that they’re wired up correctly.

[Helmholtz]

I measured a number of mid sixties AC30 speakers. DCR varied from 6.3R to 6.7R. So you should get around 13R for both speakers in series.
Is your meter accurate, calibrated and battery fresh?

Speaker impedance is always higher than DCR.