impedance difference

[internosh]

Hi All

I got my gear out of storage recently and checked the impedance of my speakers and was surprised with the results.

I am using
DR504 '72 set a 16 ohms
2 Marshall columns each containing 2x12 G12M 20w 15ohm

My knowledge of electrical circuits is minimal so I'd appreciate any feedback!

So one cab measures 25 ohms and the other 26 ohms which got me wondering because the amp was set 16 ohms.
I discovered that the speakers were wired in series and with my understanding that dc resistance measures lower
the figures are therefore about right.

Looking on the web I think I will be losing volume and gaining mid tones but I'd be interested in what others think?

[OldSchoolDave]

I discovered that the speakers were wired in series and with my understanding that dc resistance measures lower
the figures are therefore about right.

Looking on the web I think I will be losing volume and gaining mid tones but I'd be interested in what others think?

I don't know where you're looking on the web, but your amp is set correctly for your current speaker configuration.

Re-wiring the columns to parallel and setting the amp to 4 ohms, in my experience/opinion, would not make a difference in volume or tone...

Dave

[internosh]

Thank you Dave for your advice and confirming that everything is ok...it does sound ok!.

I'd just been expecting to get a reading of something closer to 16 ohms to match the amp's impedance.

cheers
.i.

[OldSchoolDave]

I'd just been expecting to get a reading of something closer to 16 ohms to match the amp's impedance.

DC Resistance will never read the same as Impedance. Also, there's no practical difference between speakers labeled 15 ohms vs. 16 ohms.

Your cabs are wired in series (2 @ 16 ohm = 32 ohms) and are connected to the amp in parallel (2 @ 32 ohms = 16 ohms). All is well.

Enjoy!
Dave

[internosh]

Thanks for that Dave, I understand the math now!
all the best
cheers
.i.