Ohmage-question

[MortenP]

I've seen the recent questions about ohm-settings, but none seemed to fit my case, so I'm gonna ask anyway...

I run my Laney GH100L through a Marshall Anniversary 4x12..I figured the cab didn't sound the same on both sides when running it in stereo, and to my surprise there was two 16 ohms 12's, and two 8 ohms 12's..My local shop told me that these cabs had four 16 ohms, and that explains why it doesn't sound right.

So what would be the right ohmage(?) to run my cab on? This is gonna be some weird resistance, right? Will it hurt my amp by running it through this cab?

Thanks in advance!!

[jackson1]

Speculating aside, you will have to explain how the speakers are connected inside the cab for us to come up with a useable answer. I could try guessing here, but you should really open up the cab and follow the wires. It should look like this:

[MortenP]

Well, at least pic shows the same speakers that's in my cab: G12t-75's,
but two of mine are 16 ohms and the other two are 8 ohms...

And you're sure that's the way they're supposed to be wired? (Just want to make sure you're not messing around)

[jackson1]

I'm not pulling your leg. This is factory as far as i know. My second stereo cab is shown below. Same config.

I bet one side in your cab was blown and erroneously renewed with 2 x 8 ohm speakers, without changing / moving any wires. So, when running stereo, one side is 8 ohm and the other is 4 ohm.

Question: how do you know they are 8 ohm? My G12T-75's aren't labelled with ohm value.

Pic of second cab:

[MortenP]

Mine are labelled 16 and 8 ohms actually..

Thanks for the great pics!

[mccullpl]

You could swap the speakers around so there's a 16 Ohm and an 8 Ohm on each side...that would give you 5.33 Ohms. If you have 4 Ohm outputs on the head, I'd use those.

[MountainDog]

You could swap the speakers around so there's a 16 Ohm and an 8 Ohm on each side...that would give you 5.33 Ohms. If you have 4 Ohm outputs on the head, I'd use those.

This would be correct.....however, in looking at the Laney website owner's manual, the GH100L has output jacks as "1 x 16 ohm, 2 x 16 ohm, 1 x 8 Ohm, 2 x 8 ohm, 1 x 4 ohm".
What this translates to is the amp will handle the following:
16 ohm load (one 16 ohm cab put into the 1x16 jack)
8 ohm load (two 16 ohm cabs put into the 2x16 jacks, or one 8 ohm cab put into the 1x8 jack)
4 ohm load (two 8 ohm cabs put into the 2x8 jacks, or one 4 ohm cab put into the 1x4 jack)

The above tells us the 2x16 and 2x8 jacks on the amp are wired in parallel. Putting your 8/16 combo wired in stereo yields 5.333 ohms per side. Putting these into the 2x8 jacks would result in the amp seeing 2.6667 ohms.....NOT GOOD!

The best thing of course would be if you could go back to the store and have them give you the correct 16 ohm speakers and wire in parallel like the pics in this thread (they would be 8 ohm per side, so you'd plug into the 2x8 jacks). If they won't help you, then you'd have to buy the 16 ohm speakers on your own and install.

In the meantime, if you want to run your cabinet without damage to the amp, you could just run either a) one 16 ohm speaker per side (plug into the 2x16 jacks) leaving the 8 ohm speakers disconnected or b) one 8 ohm speaker per side (plug into the 2x8 jacks) leaving the 16 ohm speakers disconnected. Or, because running a higher impedance doesn't hurt amps, wire the 16 & 8 ohm speakers per side as series wiring. This would give you 24 ohms per side and you'd plug into the 2x16 jacks. You'd loose efficiency and have to turn the amp up a little higher.
Here's Series wiring:

http://www.usspeaker.com/images/speaker-wiring1-size255.gif

[MountainDog]

By the way, kudos to mccullpl for the correct ohm calculation!

2 more posts and you'll be a full fledged member!

[mccullpl]

I was hoping I was right!...I'm a electronic eng. tech by trade, but I don't do a lot of parallel impedance calculations.

Pat

PS: Pretty sad it took me 4 years to become a full fledged member! hahaha

[MortenP]

This would be correct.....however, in looking at the Laney website owner's manual, the GH100L has output jacks as "1 x 16 ohm, 2 x 16 ohm, 1 x 8 Ohm, 2 x 8 ohm, 1 x 4 ohm".
What this translates to is the amp will handle the following:
16 ohm load (one 16 ohm cab put into the 1x16 jack)
8 ohm load (two 16 ohm cabs put into the 2x16 jacks, or one 8 ohm cab put into the 1x8 jack)
4 ohm load (two 8 ohm cabs put into the 2x8 jacks, or one 4 ohm cab put into the 1x4 jack)

The above tells us the 2x16 and 2x8 jacks on the amp are wired in parallel. Putting your 8/16 combo wired in stereo yields 5.333 ohms per side. Putting these into the 2x8 jacks would result in the amp seeing 2.6667 ohms.....NOT GOOD!

The best thing of course would be if you could go back to the store and have them give you the correct 16 ohm speakers and wire in parallel like the pics in this thread (they would be 8 ohm per side, so you'd plug into the 2x8 jacks). If they won't help you, then you'd have to buy the 16 ohm speakers on your own and install.

In the meantime, if you want to run your cabinet without damage to the amp, you could just run either a) one 16 ohm speaker per side (plug into the 2x16 jacks) leaving the 8 ohm speakers disconnected or b) one 8 ohm speaker per side (plug into the 2x8 jacks) leaving the 16 ohm speakers disconnected. Or, because running a higher impedance doesn't hurt amps, wire the 16 & 8 ohm speakers per side as series wiring. This would give you 24 ohms per side and you'd plug into the 2x16 jacks. You'd loose efficiency and have to turn the amp up a little higher.
Here's Series wiring:
http://www.usspeaker.com/images/spea...g1-size255.gif

Well, I didn't buy the cabinet from a store, so I'd have to get a couple of 16 ohms elsewhere..Or buy a new cab

Thanks for the feedback guys!