Speaker Impedence questions

[shihan]

I have a fantastic sounding souped up Princeton Reverb. I also have an old Peavy cabinet that’s big enough to convert into a PR with 2 10” speakers.
My question is can 2 speakers be wired so that I can disconnect 1 speaker for home use and reconnect it when I need it for playing with a band? Is it possible to have 8 ohms either way? Thanks.

 

[AcornHouse]

Yes, you can wire it to use 1 or 2 speakers. No, there is no way to have them equal the same ohms both ways. With 2 speakers, you will either double, or halve, their individual ohm rating, depending on whether you wire them in series or parallel. So, if they are, individually, 8 ohms, then they would be 16 ohms if wired in series, or 4 ohms if wired in parallel.

 

[JohnW63]

If you wire the speakers in "series" the ohms add. So a pair of 18 ohm speakers = 16 ohms
If you wire the speakers in "parallel " , the ohms = 4 ( Product over the sum or 8X8 over 8+8 which is 64 over 16 which equals 4 )

Yes, 2 tens will be louder, but to be honest, I'm not sure just how much louder. The best way to deal with the volume and not get into extra switches and loads is to just use your volume knob. There are devices that go in between the speaker and amp that can load the system and make it not send all power to the speakers. The nice ones aren't cheap. You might want to read up on the JHS one, listed in the link below with all the others.

Sweetwater Load attenuators

 

[shihan]

Thanks for the replies. My thinking was sort of a mini-Vibrolux Reverb; but I guess it’s not really practical. John, thanks for the link, but that’s more than I want to mess with. I still want to use the bigger cabinet, maybe I’ll cut a baffle for a 12” speaker. I know PR’s sound great with 12’s. Appreciate the input!

 

[DThomasC]

If you really want to run external cabs with your Princeton, one option would be to replace the output transformer with one that has taps for other impedance loads. The Classic Tone 14-18045 is a good transformer and only cost $40. Probably another $75 to have a tech install it, but it's not difficult. Maybe you have a capable friend that will help you do it yourself.

 

[shihan]

If you really want to run external cabs with your Princeton, one option would be to replace the output transformer with one that has taps for other impedance loads. The Classic Tone 14-18045 is a good transformer and only cost $40. Probably another $75 to have a tech install it, but it's not difficult. Maybe you have a capable friend that will help you do it yourself.

Good suggestion, but more than I want to mess with. The amp has already been upgraded and sounds fantastic, but I can’t leave well enough alone. I should have realized that if a 2x10 PR was a good thing, someone else would have done it already.

 

[GAD]

Let's back up a sec. Why do you want to be able to remove one speaker? Double the speakers doesn't mean double the loudness (I'd say probably 3db vs the expected 10db?) given the same amp. If you like the sound of the amp cranked but the extra speaker makes it just too much then consider an attenuator. I used to run a 2x12 Bassman that was LOUD but with an attenuator I could play it in my home office. Yeah, you lose the "speaker air moving your pants legs" effect, but the tone of pushing the power section is there.

 

[JohnW63]

The JHS attenuator was 45 bucks.

 

[Nuuska]

Here's one alternative

I'm assuming the speaker cable plugs into amp back.

Your Princeton has 8 ohm speaker - right?

Your Peavey cabinet could have two 16 ohm speakers wired parallel. Making it 8 ohm cabinet.

At home you would use the PR as is - at gig connect the Peavey cabinet instead.


Another alternative

If the Peavey cabinet is big enough for 4x8 - then you could have 4 8 ohms wired series-parallel - product being 8 ohms - for home use there could be a switch that let's you select between all-or-one speaker.

 

[Nuuska]

Then of course the three disconnected speakers would form a passive radiator enhancing low frequencies . . .

 

[shihan]

I didn’t make it plain in my first post; I have a cabinet big enough to install the amp and 2x10, that was my original thought. From the comments, I see now that it’s not practical. I’m going to cut a baffle for a 12” speaker instead. Ive hooked it up to a 12, before, and it sounds extra good.
Thanks for explaining why my idea was a bad one.

 

[Nuuska]

let's speculate a bit more.

Ok - so you could convert that Peavey cabinet to be a Princeton combo with 2x10 ( 16 ohms each ) - 1x12 - maybe even 1x15. But there remains the option of pulling the speaker plug and connecting other speaker. This way for home use you could have a small cab with an inefficient 8 inch or even smaller speaker. Just connect that and have a quiet alternative

 

[Nuuska]

Hello

Any progress ?

 

[shihan]

Yeah, I’ve decided to put a 12” speaker in the larger cabinet. The 2X10 was just an Idea. I don’t want to buy 2 4 ohm 10” speakers. If I go with a 12, I have several other amps that could also use it; so I can swap speakers around if I’m so motivated.
Just trying to figure out which 12 to get....

 

[Quantum Strummer]

A Jensen C12Q style speaker will put you in the vintage ballpark. Weber makes an excellent one. If you're looking for a warmer sound maybe try a Celestion Vintage 30.

-Dave-

 

[shihan]

Yes, I’m leaning toward the Weber version of the C12Q. I have Weber speakers in a Pro Reverb; I’m very satisfied with them.