How do you determine the 4 Ohm rating for an Amplifier?

[LEN671 0]

Just as the topic states. For example, what would be the 4 ohm rating for a AB 1100.1 be? I know on their Website it says or shows what it does at 1 Ohm, but what would it do at 4 Ohms?

Is there a Formula to this Madness or do you simply divide the RMS of the Amp by 4 to get the 4 Ohm Rating?

I know I am going to get some Stupid answers, BUT I would really like to hear Educated and Smart Answers. Thank you in Advance my Fellow Bass Heads.

Also if you know the 4 Ohm Ratings for your Amps for you Sub Stage, would you kindly list your info in this Format.

Make:

Model:

1 Ohm or whatever Ohm Load your Amp's RMS is rated at:

The Amp's 4 Ohm RMS Rating:

Again Thank you in Advance for your help gentlemen and women.

I am just trying figure this out for USACi and what Class I can or should run in. I would like to Run in the 0-1000 Trunk Class, but I have a feeling with that Amp I will be in the 1001 and Up Trunk Class. LOL!!

[suicideking602 8]

most manufactures will post wattage of each ohm load.

I ran a...

Rockford fosgate

T3000.1bd

4 ohm- 1000w

2 ohm- 2000w

1 ohm- 3000w

Thats dealer specs.

[Quentin Jarrell 671]

No you can't just calculate it like that bc efficientcy is different depending on the impedance f the driver.

And you can't just use clamp meters bc you have no way to tell how much distortion is being created(unless u got a super duper SMD distortion detector)

On a side note you'd know the rated power at 4 ohms if it was cea 2006 rated.

[CrazyKenKid 64]

I have ran in the past:

SAZ-2500

2 ohm linkable/dual mono - 5000W x 1CH----RMS power,

1 ohm - 2500W x 1CH

2 ohm - 1200W x 1CH

4 ohm - 600W x 1CH

SAZ-2000

2 ohm linkable/dual mono - 4000W x 1CH----RMS power,

1 ohm - 2000W x 1CH

2 ohm - 1000W x 1CH

4 ohm - 500W x 1CH

SAE 1200 v1

1 ohm - 1200W x 1CH

2 ohm - 600W x 1CH

4 ohm - 300W x 1CH

SAZ-1000

2 ohm linkable/dual mono - 1800W x 1CH----RMS power,

1 ohm - 1000W x 1CH

2 ohm - 600W x 1CH

4 ohm - 300W x 1CH

SAX-100.4

----RMS power, 4 ohm stereo - 100W x 4CH

----RMS power, 2 ohm stereo - 160W x 4CH

----RMS power, 4 ohm bridged - 320W x 2CH

SAX100.2

100 x 2 watts @ 4 ohms

200 x 2 watts @ 2 ohms

400 x 1 watts @ 4 ohms bridged

Orion 2500D

1200 watts x 1 chan. @ 4 Ohms

1700 watts x 1 chan. @ 2 Ohms

2500 watts x 1 chan. @ 1 Ohm

Orion 1200D

425 watts x 1 chan. @ 4 Ohms

725 watts x 1 chan. @ 2 Ohms

1200 watts x 1 chan. @ 1 Ohm

Orion 8002

200 watts x 2 chan. @ 4 Ohms

400 watts x 2 chan. @ 2 Ohms

800 watts x 1 chan. @ 4 Ohms (Bridged)

and that is all the ones i can remember off the top of my head! notice a patern?

[Impious 1,476]

Easiest way for any amplifier would be to utilize basic Ohms Law and work backwards.

First thing we need to find is the voltage the amplifier produces. The reason we need to do this is because in most (not all) modern amplifiers the voltage output the amplifier is able to supply will be the same regardless of the impedance of the load connected to the outputs (this is an assumption).

With Ohms Law we can use the formula sqrt(Power * Resistance) = Voltage.

So sqrt(1100*1) = 33.17V

Now we can use that voltage to guesstimate what the power output would be at 4ohm with the formula Voltage^2/Resistance = Power.

So 33.17^2/4 = 275w.

So, in a perfect world, the 4ohm power would be 275w. Now you'll notice the end result is the same as just dividing the 1ohm power by 4, but I thought it was more beneficial to walk through the steps using Ohms Law as it can then be applied to any scenario. In general most amps will be rated to about double their power every time impedance is halved (see below) for basically the reason that (ideally) the voltage output will be the same at any impedance so as impedance is halved power output will double (which is easily enough verified with Ohms Law).

A couple caveats to this:

Obviously this isn't going to work on amplifiers that are intentionally designed to supply the same power into different loads, such as the JL RIPS amps (the Slash series) or the Alpine PDX amplifiers. Both of those amps (and similar designs) will intentionally adjust the rail voltage when connected to a different load, so the rail voltage (output voltage the amplifier is able to supply) won't be the same at different impedances.

Second the world isn't perfect, neither are amplifiers. For starters there are some internal losses in amplifiers for various reasons and these losses become more significant as the power output increases (increases in current running through the amplifier increase heat and heat losses, components within the amplifier are running hotter, etc). On top of that, some amplifiers have a weaker power supply that isn't able to fully support the amp as the power output increases. For these reason, and some others, often times as impedance is halved the power output won't truly double. So the amplifier may actually be rated for 350-400w @ 4ohm, even though using the above process we guesstimated it should only be able to provide 275w. But even then the difference between 400w and 275w is only about 1.6db, so not really much if any of an audible difference so our rough guesstimate is "close enough".

On the reverse if we know the amp is rated 400w @ 4ohm and we want to know the 1ohm power we can use the above process.

sqrt(400*4) = 40V

40^2/1 = 1600w

But again, due to the losses in the amp, the ability of the power supply to support 1600w, etc etc etc.....the amplifier might not truly be able to output or be rated for 1600w @ 1ohm, it might only be rated 1000-1200w.

[Impious 1,476]

On a side note you'd know the rated power at 4 ohms if it was cea 2006 rated.

[Quentin Jarrell 671]

On a side note you'd know the rated power at 4 ohms if it was cea 2006 rated.

Funny thing is 85 bucks a year with cea (plus 125 membership). And about a 500 bucks to powercube to rate the amp is all it takes.....

....oh and an amp that does actually does rated power.

[LEN671 0]

Audibel,

So you don't think American Bass Amps do rated power?

I might have read your comment the wrong way. LOL!!

[LEN671 0]

Impious,

Not that I am knocking your knowledge or expertise, but the amp I am talking about does 11,000+ Watts RMS @ 1 Ohm. But you probably already knew that. LOL!!

So by using your Calculations, a AB 1100.1's 4 Ohm RMS Rating would be 2750 Watts RMS.

[LEN671 0]

Correction.

The American Bass AB 1100.1 does 12,500 Watts RMS.

My bad. No one bite my head off!!

[bassahaulic 155]

CEA 2006 rating is a joke......

[Robert 9]

good to see you here Len theses dudes will help you out this will be very helpful to you.

[Quentin Jarrell 671]

Impious,

Not that I am knocking your knowledge or expertise, but the amp I am talking about does 11,000+ Watts RMS @ 1 Ohm. But you probably already knew that. LOL!!

So by using your Calculations, a AB 1100.1's 4 Ohm RMS Rating would be 2750 Watts RMS.

As he and I both said in the real world it doesn't work that way bc amps aren't 100 percent efficient.

Higher the ohm load you gain efficientcy, lower the ohm load you lose it.

[NDMstang65 403]

So figure that by 65-70% or so..and that's what you are looking at..

..then hook it to a < 1% efficient speaker and you're really on to something

[LEN671 0]

Audibel,

I understand what you and Impious are saying. Thank you both as well the rest of you who have provided your input to my question.

So as far as the amp I used in my example, That Amp's 4 Ohm Rating will put it's User into the 1001 and Up Trunk Class for the USACi Organization.

[Quentin Jarrell 671]

Correct, I'm no competitor but these organizations don't have an official list that states amplifiers rated outputs( or outputs that they consider rated). I know there is a lot of amps on the market but it would seem it would be worth the time to ensure no unintentional cheating would occur in power classes.

[LEN671 0]

So I guess it is looking like my friend will be going the Multiple Amp route.

Again thank you all who have given their input to this subject. And again Thank you in advance to those of you who might add or do add on to this Topic after I write this.

[LEN671 0]

Yes, that would be great to have somewhat of a listing as far as what Amps you can use and the amount for each class. But then again like you stated, There are SO MANY different kinds of Amp's out there. There would be constant and repetitive changes done to the list.

[Impious 1,476]

Impious,

Not that I am knocking your knowledge or expertise, but the amp I am talking about does 11,000+ Watts RMS @ 1 Ohm. But you probably already knew that. LOL!!

So by using your Calculations, a AB 1100.1's 4 Ohm RMS Rating would be 2750 Watts RMS.

Actually no I had no idea, I don't follow SPL or American Bass so I have no idea of their power ratings and/or model #'s. I used 1100 because of the model #.

Either way the same process applies.