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4 ohms is 4 ohms, right?


tylytle

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My band has 2 415 Peavey cabs for subs. They are 8 ohms each. I am looking at buying an amp that will bridge at 4 ohms. My singer thinks that because there are 8 speakers it will be to much load. But 4 ohms is 4ohms, right??

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Im quite a supporter of Peavey stuff, but arent they the ones that are only 300W? Not a lot of power for subs.

Do they make your pants flap?

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Thats just 75w to each 15" driver.

 

Either way.. you want a power amp with about 600W per side at 8 ohms.

Peavey CS series would suit you down to the ground!

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It's a bit tricky but I'll try to make it simple.

 

Ohms are used to measure resistance. They are also used to represent impedance. Impedance is what matters in the case of speakers.

 

Ohms used as impedance are what are called 'nominal' measurements, not absolute measurements. Same as with a 2x4: They actually measure as 1 1/2 x 3 1/2.

 

So a speaker labeled as '4ohm' won't actually read as 4ohms resistance because of the 'nominal' value (and the fact that impedance is a different thing than resistance.)

 

In terms of 'how many speakers' what matters most is the impedance, but there does reach a point where there simply isn't enough power to push them all. You'll neeed to keep an eye on that.

 

A cabinet's power handling is determined by the number of speakers and how they are wired. A cabinet's impedance is determnined by the number of speakers in it, their individual impedances and how they are wired.

 

Ideally the cabs should have around 50% more power handling than your amp puts out, and NEVER less.

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yeah these subs are very nice. They handle a lot more than 300 watts. We are now running a cs 800 bridged to each one. I am going to put a Europower 2500 on them. We lost an amp and this is the cheapest way to get back up. I have had great luck with these amps so far.

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yeah these subs are very nice. They handle a lot more than 300 watts. We are now running a cs 800 bridged to each one. I am going to put a Europower 2500 on them. We lost an amp and this is the cheapest way to get back up. I have had great luck with these amps so far.

Oh, man!

The Europower will make you sad.

1 peavey Watt is equal to about 15 Europepower watts.

You would serioulsly be better off limping by on the CS800 stereo to both until you can afford a real amp. Please consieder seriously before throwing money away.:eek:

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Oh, man!

The Europower will make you sad.

1 peavey Watt is equal to about 15 Europepower watts.

You would serioulsly be better off limping by on the CS800 stereo to both until you can afford a real amp. Please consieder seriously before throwing money away.
:eek:

 

 

have you had these two amps side by side? I have.

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I second the motion of not bridging an amp, unless you are working with pros, and even then the company I work for opts for more amps than running the risks involved with bridging amps.

 

I have not A/B'd those two amps, but I can tell you that less expensive gear tends to have less in the way of actual protection, so running a lot of watts for a show may cause it to thermal out or worse. again I have not compared those two amps specifically.

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Nope not made up. Just wanting real use/comparison. I also love cs 800's, Just can't afford or find one at the moment. I need this back up and running soon. I guess I could just buy a smaller amp and swap the 800 that runs the monitors for the smaller wattage/cheaper amp and put that 800 on one of the subs... Hmmmm might be an idea.

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Nope. 4 Ohms resistance is very different from 4 Ohms reactance, which is very different from 4 Ohms impedance.

 

 

True, but what we care about here is only impedance, which cannot be accurately directly measured by a multimeter.

 

However, relative to amps and speakers, 4 ohms is indeed 4 ohms (because it's all in terms of impedance). Just make sure you have the proper power handling capacity.

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For your purposes, 4 Ohms is 4 Ohms. :D

 

Any given amp will drive a 4 Ohm cab with 4 speakers in it just as well as it will drive a cabinet with 1. The amp only sees the total impedance of the load, it doesn't care how that impedance was arrived at.

 

As for the 'risks' of bridging amps, there really aren't any as long as you observe the minimum speaker load impedance for bridge mode and connect the speakers to the amp correctly.

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For your purposes, 4 Ohms is 4 Ohms.
:D

Any given amp will drive a 4 Ohm cab with 4 speakers in it just as well as it will drive a cabinet with 1. The amp only sees the total impedance of the load, it doesn't care how that impedance was arrived at.


As for the 'risks' of bridging amps, there really aren't any as long as you observe the minimum speaker load impedance for bridge mode and connect the speakers to the amp correctly.

 

 

Thanks! I have been bridging amps for years. What you said is true.

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The only complaint I ever had with bridging is the fact that virtually ALL amps shed a bunch of watts in the process.

 

 

I'm not sure what you mean here. Bridging certainly limits your minimum load impedance (because each half of the amp 'sees' half the load impedance) but it allows you to get full power out of the amp at higher load impedances. If an amp can do 400W per channel into 4 Ohms it will put 800W into an 8 Ohm load in bridge mode. Bridging doubles the maximum output voltage swing of the amplifier and is only limited by the current capacity of the power supply and output devices.

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LOL. I mean the number of speakers isn't going to matter right? 4ohms is 4 ohms whether it's one speaker or 8 speakers...

 

 

The number of speakers doesn't matter. If anything, it makes it easier, because the drivers will operate in a more linear region, and put out more sound per watt.

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It's a bit tricky but I'll try to make it simple.


Ohms are used to measure resistance. They are also used to represent impedance. Impedance is what matters in the case of speakers.


Ohms used as impedance are what are called 'nominal' measurements, not absolute measurements. Same as with a 2x4: They actually measure as 1 1/2 x 3 1/2.


So a speaker labeled as '4ohm' won't actually read as 4ohms resistance because of the 'nominal' value (and the fact that impedance is a different thing than resistance.)


In terms of 'how many speakers' what matters most is the impedance, but there does reach a point where there simply isn't enough power to push them all. You'll neeed to keep an eye on that.


A cabinet's power handling is determined by the number of speakers and how they are wired. A cabinet's impedance is determnined by the number of speakers in it, their individual impedances and how they are wired.


Ideally the cabs should have around 50% more power handling than your amp puts out, and NEVER less.

 

 

Your post is good, except for this: "In terms of 'how many speakers' what matters most is the impedance, but there does reach a point where there simply isn't enough power to push them all. You'll need to keep an eye on that." Simply not the case. More drivers are more efficient than fewer drivers, and will produce more sound per watt than fewer drivers.

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I'm not sure what you mean here. ...

 

 

Looking at my earlier post and seeing what a {censored} I took in writing that sentence, I'm not suprised to hear this!

 

With sarcasm I was trying to say that they shed watts when NOT bridged (ie when run in stereo). Obviuosly what I meant was not what I said.

 

Apologies.

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