4ohm Head into 16ohm cab.

[hunter1970]

What affect will plugging a 75 watt 4 ohm head into a 16 ohm 4x12.
I'm curious because I'm paying on a Peavey"5150" 16 ohm 4x12 and I currently have a 4ohm Line 6 Spider II head,but I plan on selling the Line 6 in order to purchase a head to match the speaker impedance.I really don't want to even try playing through the cabinet until I get a different head.
Can someone shed some light on this for me?

[marcus]

Plugging a solid state amp into a cabinet of higher impedance than it is rated for is fine, you should have no problems. This is not true of tube amps, though.

[yabba]

^^ what he said. most solid state heads (like the spider II) have a minimum impedance that you don't want to go below, but it will most definetely be lower than 16 ohms, so you can use that cab with that head with no issues

[thetroy]

It will be fine

[CharvelRocker]

Not to hijack this thread, but on the flipside, could I plug a 8ohm tube amp into a 4ohm cab?

[thetroy]

That's when it's a bad idea. Check with the amp manufacturer first, but often the printed stat is the minimum impedence to be used.

[DonP]

If your feeling adventurous, rewire the 16 ohm cab to 4 ohms. At 16 ohms, you will not get full power output.

Tube amp 8 ohm into 4 or 16 should be ok from what I've heard, but don't go two steps off (4 -> 16 or 16 -> 4). For tube amps, it's really best getting the impedance correct.

[Dreamland_Rebel]

cab ohms higher than head ohms = safe
cab ohms matching head ohms = ideal
cab ohms lower than head ohms = bad

2 cabs on same head = half the ohms (impedance).
i.e 2 16ohm cabs draw 8 ohms on the head.

[CharvelRocker]

Well heres another one thne:

It has a Speaker out and an Extension Jack. The speaker in it is rated at 8ohms (what it runs at now). If I lead that speaker in and plugged in my cab to the extension out, what would be the ohms resistance on that extension out with the amp using the single 8 ohm speaker on it?

[Cygnus X1]

Well heres another one thne:

It has a Speaker out and an Extension Jack. The speaker in it is rated at 8ohms (what it runs at now). If I lead that speaker in and plugged in my cab to the extension out, what would be the ohms resistance on that extension out with the amp using the single 8 ohm speaker on it?

What amp are you referring to? I would suppose that the extension outlet would be 8 ohms, also. It should be labeled as such. If not, refer to the owner's manual, even if you have to find it online.

I prefer not to mess around, and stay within the amp's ratings. Even if I have to rewire the cab, or replace speakers to make it work. I'm an old tube amp user, and replacing output transformers is an expensive mistake.

[CharvelRocker]

What amp are you referring to? I would suppose that the extension outlet would be 8 ohms, also. It should be labeled as such. If not, refer to the owner's manual, even if you have to find it online.

I prefer not to mess around, and stay within the amp's ratings. Even if I have to rewire the cab, or replace speakers to make it work. I'm an old tube amp user, and replacing output transformers is an expensive mistake.

A Crate vintage Club 60. You can selector 16 or 8 ohms. Right now it has a single 8 ohm speaker plugged into the speaker out, with the extension jack sitting empty. I'm wondering if it would change the resistance by having the regular speaker plugged in while the amp is also run to the extension cab.

[marcus]

A Crate vintage Club 60. You can selector 16 or 8 ohms. Right now it has a single 8 ohm speaker plugged into the speaker out, with the extension jack sitting empty. I'm wondering if it would change the resistance by having the regular speaker plugged in while the amp is also run to the extension cab.

Yes, the resistance will be changed. If the extension cab is the same impedance as the speaker, the impedance seen by the amp will be halved, or 4 ohms in this case. If they are different you can use the formula:

R1*R2/(R1+R2)

where R1 and R2 are the impedances of the cabinet and the speaker.

[Dreamland_Rebel]

to be on the safe side, if you plug in the ext cab, disconnect the combo speaker.

[Cygnus X1]

to be on the safe side, if you plug in the ext cab, disconnect the combo speaker.

But...don't run the amp without a load through the primary jack. Plug the cabinet into the primary side. Never run a tube amp without a load.

[toejam]

But...don't run the amp without a load through the primary jack. Plug the cabinet into the primary side. Never run a tube amp without a load.

I run my one amp without a load all the time... then again, it's a THD Univalve that has its own built-in load and can be used that way.