Anyone have a table or conversion for power ratings at different Ohms?

[Intercooler 10+ year member]

Just curious if a table exists showing what power you would have going to say X speakers and have an amp with certain power ratings at 1 Ohm, 2 Ohm and 4 Ohm. If one doesn't exist and someone can give me the basics on how to break everything down I would like to make one up in Excel so it is easy to figure Watts at all the different Ohm ratings for amps and speakers.

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[SuperJETT 10+ year member]

If an amp can put out 40 volts to 4 ohms, that's 10 amps (I=V/R) so it puts out 400 watts (P=I^2*R) It depends on the amp, but if it's truly 2 ohm stable and can still output the same voltage, then since the ohms went down by half, the power will double to 800 watts. And same for 1 ohm, it would quadruple to 1600 watts.

But, it's all dependent on the construction of the amp. Some can't hold the voltage but are still stable at lower ohms, so they will put out more power but not double/quadruple/etc.

 

[Raven 10+ year member]

http://forums.caraudio.com/vb/showthread.php?t=63933

 

[squeak9798 5,000+ posts]

As was mentioned......Just follow ohms law.

http://www.bcae1.com/ohmslaw.htm

 

[helotaxi 5,000+ posts]

Ohm's law holds true in a perfect world with no losses and unfortunately, we don't live in that world. The limiting factor is the capacity of the power supply and the output section of the amp in question. The power supply can only provide so much current at its design voltage. Ask it to provide more and it chokes, and drops the voltage and consequently clips the signal. Additionally, even if the power supply could provide infinite current at the desired voltage, the output devices can only flow a finite amount of current. Try to get them to flow more and they go *poof*. They are also limited by the amount of heat that can be dissipated be the transistors and their respective heatsinks. Flowing current within the design limits of the device for extended periods with inadequate heat removal will also cause the release of the magic smoke.

To these ends most all modern amplifiers have "smart" power supplies that roll back the power supply voltage when larger current demands (low impedence loads) are placed on the amp. The lower voltage (because of Ohm's law) reduces the current demand for the given load compared to the higher voltage. The overall result is a reduction of power compared to the perfect system that doubles it's power into half the load.

Also consider that as you flow more current through a system it will heat up (also Ohm's law with the resistance of the amplifier components as the R). The hotter it gets, the more power lost to heat and the more voltage lost that heat.

Many amps are rated to double their 4 ohm power into 2 ohms. Most of them will make their 2 ohm power and those that do are designed to that end and as a result typically make considerably more power than their rating into 4 ohms.

 

[squeak9798 5,000+ posts]

Holy Heck.....He's Alive !!!!!!!!!!

 

[helotaxi 5,000+ posts]

Holy Heck.....He's Alive !!!!!!!!!!

The rumours of my demise were slightly exaggerated...