Cab ohms?

[IbanezShreds]

I just purchased an avatar 4x12 with two v30s and two g12k100s wired in a cross pattern. I have a 5150 signature with a switch for 4 8 and 16 ohms. The cab is 8 ohms. Where should i have the head set ohms wise? Im also playing a 7 string tuned to drop E if that means anything (not my idea...)

 

[MaxOfMetal]

I just purchased an avatar 4x12 with two v30s and two g12k100s wired in a cross pattern. I have a 5150 signature with a switch for 4 8 and 16 ohms. The cab is 8 ohms. Where should i have the head set ohms wise? Im also playing a 7 string tuned to drop E if that means anything (not my idea...)

 

[axxessdenied]

Cab is 8 so your head should match.


And....

 

[drgamble]

I think what you are saying here is the Avatar cab is 8 ohms. Set the 5150 to 8 ohms and run the head at 4 ohms. If I am understanding you correctly than this is what you wanna do. Two 8 ohm cabs would be a 4 ohm load on the head.

 

[glpg80]

The cab is 8 ohms.

Set the amplifier to 8 ohms.

 

[drgamble]

Set the amplifier to 8 ohms.

He's running 2 cabs not 1. 4 ohms for 2 8 ohm cabs. It's pretty simple math as since it is not a mixed load.

 

[MaxOfMetal]

He's running 2 cabs not 1.

Where does it say that?

 

[glpg80]

He's running 2 cabs not 1. 4 ohms for 2 8 ohm cabs. It's pretty simple math as since it is not a mixed load.

As an Electrical Engineer and someone who does this for a living, set the cabinet to 8 ohms for maximum power transfer and be done. Re-read the question and read it carefully before giving advice which could cause someone serious damage to their amplifier. The math does not matter if you cannot read

 

[Wrecklyss]

How to figure out impedance load:

In series: add impedances of all speaker cabinets together (Ztotal=Z1+Z2....)

In parallel: add impedances of all cabinets together, then divide by twice the number of cabinets (Ztotal= Z1+Z2..../2NumCabs)

How to tell if your hooking up in series or parallel? read the jack. Going in to out on a cab is almost always parallel, Using jacks on the back of your amp, look for specific "series" or "parallel" labeling on the jacks.

 

[glpg80]

Wrecklyss is correct, except most jacks are not labeled series or parallel for tube amplifiers but rather the expected impedance load the secondary of the transformer expects to see. One the cabinet, you may see a plate that has stereo or mono mode or an in/out jack. In this particular case there is no math involved - you set the impedance of the amplifier to the cabinet impedance, make sure the cabinet is set to mono and you're simply done - no math involved.

You may want to check to make sure the cabinet is indeed 8 ohms of the speakers have been changed or wired by someone else. You can use a multi-meter to get a very general idea by measuring the resistance + to - on the jack, or by drawing a wiring diagram of the cabinet wiring, run the above math, and make sure everything matches.

Would hate to answer your question only to find out the cabinet you purchased was 16 ohms.

 

[bob123]

where the hell are you guys getting 2 cabs from?



And... How the hell is 4 speakers wired in parallel 8 ohms lol

 

[Wrecklyss]

And... How the hell is 4 speakers wired in parallel 8 ohms lol

4 8ohm speakers can be wired to 8ohms when you wire 2 pairs of speakers in series, and then wire the pairs together parallel OR you wire two pairs of speakers in parallel and wire the pairs together in series. Sometimes, the running of the speaker wire on the inside makes what looks like an "X" pattern.

 

[axxessdenied]

He's running 2 cabs not 1. 4 ohms for 2 8 ohm cabs. It's pretty simple math as since it is not a mixed load.

 

[jesebullet]

Hey guys, noob question here:

I'm currently using an old amp as my cabinet, it has a 2x12 speakers load each one marked as 8ohms. Also, each one has a cable input to be connected to the head. Should I be running the head at 4ohms? Thanks in advance.

 

[mnemonic]

Each speaker being 8 ohms, wired in parallel (which it is with that plug) equals 4 ohms load. So that looks right to me as it is set in the picture

 

[DudeManBrother]

As long as each speaker has only one + and - connected directly to a separate speaker jack, then yes it's a 4 ohm load. If they're wired together, it could be series (16 ohm) or parallel (4 ohm).

 

[Thanatopsis]

First, not sure if you're aware of this but an ohm is a unit of resistance. Lots of higher end car stereo amps for putting huge amounts of power to subwoofers for example can run at very low impedance, some as low as half an ohm. They can put out more power lower because there's less resistance, pushing an 8 ohm load like pushing something 100lbs vs 50lbs for a 4 ohm load. However they will generate more heat and the damping factor will be lower but that's a bunch of stuff you don't need to care about nor can a simple explanation here do what you can easily learn via a web search.

Are all 4 speakers in the cab wired together so you have just one output or is each pair separate? The other ones impedance would depend on if the speakers are wired in series or parallel. If in series 2 4 ohm would be an 8 ohm load. In parallel they would be 2 ohms.

Here's a couple articles you can check out to learn more about speaker impedance and there's plenty more out there you can find easily.

http://www.audiogurus.com/learn/speakers/speaker-impedance-rating/1092
http://www.prestonelectronics.com/audio/Impedance.htm

 

[bostjan]

First, not sure if you're aware of this but an ohm is a unit of resistance. Lots of higher end car stereo amps for putting huge amounts of power to subwoofers for example can run at very low impedance, some as low as half an ohm. They can put out more power lower because there's less resistance, pushing an 8 ohm load like pushing something 100lbs vs 50lbs for a 4 ohm load. However they will generate more heat and the damping factor will be lower but that's a bunch of stuff you don't need to care about nor can a simple explanation here do what you can easily learn via a web search.

Are all 4 speakers in the cab wired together so you have just one output or is each pair separate? The other ones impedance would depend on if the speakers are wired in series or parallel. If in series 2 4 ohm would be an 8 ohm load. In parallel they would be 2 ohms.

Here's a couple articles you can check out to learn more about speaker impedance and there's plenty more out there you can find easily.

http://www.audiogurus.com/learn/speakers/speaker-impedance-rating/1092
http://www.prestonelectronics.com/audio/Impedance.htm

I suppose that's a fair enough analogy. However, there are a number of reasons why its more complicated than that. The higher the DC ohms, the more winding on the voice coil. The beefier the voice coil, the more power can be delivered.

It's like, in your analogy, pushing something that weighs 100 pounds, versus something that weighs 50 pounds: pushing 100 pounds requires twice the power, and the energy of the moving 100 pound weight is twice as much, therefore, twice as much power (power = energy used per unit time). If you use the same power amp, it's like using the amount of muscle to push. Twice the cab ohms and the same amount of amplifier power is like twice the weight and the same amount of muscle. There will be a decrease in overall efficiency if the amount of muscle is not ideal for the amount of weight.