What impedance to set on amp? Specific issue

[Woody333]

I have an old (1968-ish) 4 x 12, Pinstripe grill. Speakers must have been replaced around 1973 with G12 H 30W 75 Hz 16 Ohms. I decided to check the state of the speakers now and found that they're all 12.2 Ohms instead of, I guess, what the original G12 Ms would have been (around 13.5?).
The whole cab as measured at the input jack is 11.8 Ohms. SO, my question is, what impedance should I set the amp (70s 50W Master Volume) which of course only has 4, 8 or 16 Ohms settings? Sorry if it's already been covered, new member as of yesterday. Cheers guys.

 

[junk notes]

15Ω Pulsonics?

Use the 16Ω.

 

[BlueX]

Welcome to the forum!
(question already answered)

 

[Woody333]

Thanks guys for the welcome and the answer. Should you always go for an amp impedance setting at least higher than that of the total quad cabinet? Is that for safety, not being particularly au fait with the physics of these electronics? When I used to use the equipment when I was a lad (!!!) I just assumed that the cabinet was sold as 16 ohms, therefore it must be 16 ohms so that's what I set, perhaps luckily?
Junk notes, how do I tell if the G12 H s are Pulsonics, haven't seen that word on them?
Thanks again.

 

[fitz]

Should you always go for an amp impedance setting at least higher than that of the total quad cabinet? Is that for safety, not being particularly au fait with the physics of these electronics? When I used to use the equipment when I was a lad (!!!) I just assumed that the cabinet was sold as 16 ohms, therefore it must be 16 ohms so that's what I set, perhaps luckily?

Resistance measured on a multi-meter will always be a lower value than the stated ohms rating on a speaker. Speaker ohms, and the amp output transformer taps, are more of a calculated value based on the amount of power flowing through the circuit while the amp is operating. Checking a speaker with a meter is just a good way to make sure you're not seeing something like 6.5, when you are expecting 13 to 14 for a 16 ohm rated speaker.

 

[Gutch220]

yea, 16 ohms set on the amp

 

[Woody333]

Thanks guys, appreciated 👍

 

[neikeel]

Resistance measured on a multi-meter will always be a lower value than the stated ohms rating on a speaker. Speaker ohms, and the amp output transformer taps, are more of a calculated value based on the amount of power flowing through the circuit while the amp is operating. Checking a speaker with a meter is just a good way to make sure you're not seeing something like 6.5, when you are expecting 13 to 14 for a 16 ohm rated speaker.

As above!

 

[Marcomel79]

Post pictures of the codes on the basket and cone of each speaker and someone here will be able to tell you if they are Pulsonic or not!