70s Peavey 6x10 speaker retrofit.

[jazzbass_5]

I would recommend series connections for each pair of 2 drivers, then paralleling th 3 pairs. Call it a 4 ohm cabinet and be done with it.

Exactly what I did.

 

[jazzbass_5]

I've gotta say I'm really impressed with the sound. It turned out better than I expected.

 

[Old Garage-Bander]

All 6 of the old speakers were the old square magnet Peaveys, the cab was never really intended for bass, it was more of a guitar cab/keyboard cab, at least according to the old Peavey adds. When I got the cabinet it had 4 left in it (2 on top and 2 on bottom with a couple of crap replacments) they were all the same impedance, one had a ripped and repaired cone the other 3 were in decent shape and I boxed them up for storage. They measure out to 23 ohms a piece! Here's some pictures.
View attachment 3014463 View attachment 3014464 View attachment 3014465

So probably 32 Ohm nominal impedance?
With the meter you are measuring the voice coil wire DC resistance.

If I remember correctly DC resistance is always a bit lower than nominal Z.
An 8 Ohm Driver usually measures out to be somewhere between 5 or 6 Ohms.
If it is fair to scale that up, a 32 Ohm impedance would measure right around what you show on your meter.

 

[jazzbass_5]

So probably 32 Ohm nominal impedance?
With the meter you are measuring the voice coil wire DC resistance.

If I remember correctly DC resistance is always a bit lower than nominal Z.
An 8 Ohm Driver usually measures out to be somewhere between 5 or 6 Ohms.
If it is fair to scale that up, a 32 Ohm impedance would measure right around what you show on your meter.

With that, the plate on the back said the cabinet was rated at 4 ohms. Not sure how exactly they got to that unless they were rounding down from 5.33. Thoughts?

 

[agedhorse]

Nominal impedance involves some averaging and rounding

 

[scuzzy]

I love when a plan comes together

 

[Old Garage-Bander]

With that, the plate on the back said the cabinet was rated at 4 ohms. Not sure how exactly they got to that unless they were rounding down from 5.33. Thoughts?
View attachment 3014496

"Nominal" means, in name only.
The speaker/cab will present a 4 Ohm load to the amp at one frequency. This can be determined using an audio oscillator and some other test equipment that most people don't own. A multimeter alone will not give you impedance.
So the actual instantaneous impedance that a speaker/cab presents is all over the place given that the output frequencues of your bass is a complex mix of fundamentals and harmonics. The speaker manufacturers determine a nominal impedance so that you will know what you can and cannot connect to your amp.
If it helps, think of it like gas milage. What the sticker on the auto says vs what you get may be different, but it should be in the ballpark, or nominal. So just like with gas milage, YZMV. Your Impedance May Vary. (Z is the symbol for impedance) But unlike gas milage, you will do well to not exceed the minimum rating on the amp when using the nominal ratings on the speaker as your guide.

 

[jazzbass_5]

"Nominal" means, in name only.
The speaker/cab will present a 4 Ohm load to the amp at one frequency. This can be determined using an audio oscillator and some other test equipment that most people don't own. A multimeter alone will not give you impedance.
So the actual instantaneous impedance that a speaker/cab presents is all over the place given that the output frequencues of your bass is a complex mix of fundamentals and harmonics. The speaker manufacturers determine a nominal impedance so that you will know what you can and cannot connect to your amp.
If it helps, think of it like gas milage. What the sticker on the auto says vs what you get may be different, but it should be in the ballpark, or nominal. So just like with gas milage, YZMV. Your Impedance May Vary. (Z is the symbol for impedance) But unlike gas milage, you will do well to not exceed the minimum rating on the amp when using the nominal ratings on the speaker as your guide.

So, 4 ohms....

 

[Old Garage-Bander]

So, 4 ohms....

Says 4 Ohms on the cab. Unless someone messed with it, that is the manufacturers nominal impedance rating.

-edit- Of course you are changing speakers so the back plate rating is moot. The nominal impedance of the cab will be the combination of all of the nominal impedance ratings of the speakers and how you wire them up.

-edit edit- With six 8 Ohm drivers, you could have any number of combinations of wiring such that your total cab impedance will something between 0.75 Ohms (everything in parallel) and 48 Ohms (all in series) or something in between depending on how you wire it.