Cabinet Wiring Oddity

[Never2Late]

Feeling stupid while I type this:  So, I'm wiring-up a restored Hiwatt cabinet with some brand-new Fanes and EV Classics.....I 'thought' I was wiring-up all 16-Ohm cones, used the common seres-parallel method found everywhere online.  Finished-up, until I did a last-minute multimeter check of the Cab total-load before sealing it up.....7.4 Ohms.

"Hmmm, can't be right....supposed to get around 16 ohms here"  Oops, EV Classics are rated 8 Ohms each, and I 'thought' I bought 16-Ohm Fanes....now I'm not sure.  I measured a Fane by-itself, and got something less than 12 Ohms....total load of the Cab is 7.4-7.6 Ohms, so if I just dial my amp to 8-Ohm load, am I good-to-go, or will a Ohm mismatch in the cab result in one pair of speakers being driven harder than the others?

[Bloozguy]

I think you are confusing DC resistance with impedance. A 16 ohm speaker will typically read between 7 and 12 ohms DC resistance. You should be fine using the 16 ohm speaker output.

[Never2Late]

Crap - then the Fanes are DEFINITELY 16 Ohm cones, and the EVs are 8 Ohms (says-so on the rear label, fine-print) - I have mixed cones in the same cabinet.

[benjammin308]

Just set the amp for 12 ohms and you're good to go.  Seriously, you could get away with using the 8 ohm amp output as it is generally OK to have a load with a larger impedance than the amp is expecting but not a smaller one.  Personally I would go with all 8s or all 16s, and Bloozguy is right - trust the label, not the meter.

Edited to add:  I love my Hiwatt cabinet, you will be very happy!

[Dave Scepter]

3 hours ago, Never2Late said:

am I good-to-go, or will a Ohm mismatch in the cab result in one pair of speakers being driven harder than the others?

Yes on both accounts... if your  "total" reading is less than an 8 ohm load you should set your amp speaker switch at 8 ohms... there's obviously going to be a mismatch however, and it depends on each speakers efficiency accounting the db differential... try it, you might like it... I always use my meter to check the impedance of a speaker because old/worn speakers will have a lower impedance reading then what listed... I have 60's, 70's & 80's 16 ohm speakers reading 10 ohms and they're not reconed... especially in the ol JBL/Altec Lansing days where lots of stuff were either reconed or incorrectly labeled/ badged from the factory

[tomteriffic]

When you strap a multimeter across a speaker's leads, what you're measuring is series resistance, not impedance. A rule of thumb is that the resistance measured is roughly 2/3 of the actual impedance, so an 8 ohm speaker will typically read around 5.4 ohms. Following from that, a 16 ohm speaker should read around 10-11 ohms.

Short answer, set the impedance switch at 8 ohms. Your actual total impedance will be around 11-12 ohms and tube amps much prefer a mismatch to the high side than to the low side.