why does efficiency increase when ohm load increases?

[caseyarndt 10+ year member]

So I know that heat is the result of lower efficiency but you would think that more resistance would cause more heat and lower amp efficiency but it doesn't....right?

If anyone can shed some light I would appreciate it.

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[05trailblazer 10+ year member]

you see less power when ohm load increases

 

[caseyarndt 10+ year member]

less power but why greater efficiency?

 

[Buck 5,000+ posts]

Well, higher ohm load means you pull less current, less current = less heat.

 

---------- Post added at 07:40 PM ---------- Previous post was at 07:40 PM ----------

 

I guess.

 

---------- Post added at 07:41 PM ---------- Previous post was at 07:40 PM ----------

 

What perspective are you talking about, like ohm load on your amp or imp. rise or...?

 

[caseyarndt 10+ year member]

so if an amp puts out 1000 rms at 4 ohms and you ran it at 1000 watts at 1 ohm would it have the same efficiency?

well I'm just trying to understand a little bit more about how amps work, I guess just ohm load vs efficiency.

because manufacturers rate amps at let's say 80% efficient at 4 ohms and 70% at 1 ohm...just an example but is the efficiency lower just due to more watts or is there something about the lower ohm load that makes the amp less efficient?

 

[Buck 5,000+ posts]

Edited for removal of d-baggery.

If you had an amp do 1000 @ 4 ohms

and one that did 1000 @ 1 ohm

the one a 4 ohm is going to be more efficient and probably sound pretty good too.

 

[caseyarndt 10+ year member]

well I'm saying lowering the ohm load and adjusting the gain down to the same watts it puts out at 4 ohms

 

[RoYALbLUE08 10+ year member]

ddd

 

[TaylorFade 10+ year member]

so if an amp puts out 1000 rms at 4 ohms and you ran it at 1000 watts at 1 ohm would it have the same efficiency?

That's an excellent question. Efficiency ratings are usually given for rated power at a particular ohm load. i.e. - 90% @ 4 and 78% @ 1ohm. My contention is that if you were to run the amp at a lower load yet set it for less output, the efficiency would increase, but I doubt it would still meet the original 4 ohm efficiency.

I'm sure there's some complex mathmatical forumlua to illustrate this using Ohm or Hoffman, but I imagine it has to do with the "work" the amp is doing. A lower ohm load is actually more of an actual load meaning the amp is working harder.

I'm trying to come up with an analogy but all I can come up with is... imagine your car with just you in it as a 4ohm load and mpg's being it's efficiency. Every passenger you add is like another sub added to the amp. Your car is still going 70mph at 2,500rpm, but the efficiency (mpg) is going to suffer because of the added "load."

 

[Buck 5,000+ posts]

well I'm saying lowering the ohm load and adjusting the gain down to the same watts it puts out at 4 ohms

See, I don't know if there is some kind of current pull to efficiency ratio.

If you are low gain at 1 ohm and not drawing that much current, I'm not sure if your efficiency rises or not.

 

[caseyarndt 10+ year member]

That's an excellent question. Efficiency ratings are usually given for rated power at a particular ohm load. i.e. - 90% @ 4 and 78% @ 1ohm. My contention is that if you were to run the amp at a lower load yet set it for less output, the efficiency would increase, but I doubt it would still meet the original 4 ohm efficiency.
I'm sure there's some complex mathmatical forumlua to illustrate this using Ohm or Hoffman, but I imagine it has to do with the "work" the amp is doing. A lower ohm load is actually more of an actual load meaning the amp is working harder.

I'm trying to come up with an analogy but all I can come up with is... imagine your car with just you in it as a 4ohm load and mpg's being it's efficiency. Every passenger you add is like another sub added to the amp. Your car is still going 70mph at 2,500rpm, but the efficiency (mpg) is going to suffer because of the added "load."

it would seem that efficiency would rise if the gain was turned down.

but I think I understand what you are saying.

there has to be someone who has tested this though

 

[Buck 5,000+ posts]

Nah, if it's at one ohm, it's full power baby //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[quackhead 10+ year member]

less power but why greater efficiency?

As the resistance (ohm load) rises, the amp is producing more voltage, but less amperage, thus requiring less amperage. The output is restricted by the resistor(speaker), the amp is more stable and produces less heat. Amps are rated by power output, Dampening factor, THD, Signal to noise ratio, etc. These factors indicate not only how much, but more importantly, how well the amplifier handles the signal being amplified. These ratings are 99.9% of the time taken while using the highest ohm rating of the amplifier.

As the resistance to the amp decreases, the amplifier works harder to provide more amperage, causing the amplifier to destabilize and produce more heat. When this happens, the amp looses dampening ability(sub cone control), produces more noise and distorts the signal passing through.This is why most amps are not even measured for distortion and dampening below 2 ohms...some amps are made more tolerable than others and can perform better at a lower impedance than others. this is why some 1000 watt amps cost $800 and some cost $150.

 

[quackhead 10+ year member]

it would seem that efficiency would rise if the gain was turned down. but I think I understand what you are saying.

there has to be someone who has tested this though

the only way to increase efficiency is to increase resistance...the gain is simply to match the components of your system...amp input voltage to HU output voltage..that is all it is.

set it too low, you risk clipping the input signal, set it too high, you risk over driving and clipping the amplifier's input section.

 

[quackhead 10+ year member]

These are all close enough in power to be compared based on 4 ohm power due to the inaudible differences in power ratings at 4ohms.

Based on rated specs at 4 ohm power output, with no reference to cost, which would you buy?..and why?

SSA Shop - Sundown Audio SAZ-3500D amplifier

Incriminator Audio 40.1 Mono Block - 3600W

Zapco DC1100.1 1 Channel Amplifier with On-Board Digital Processing

AQ3500D.1 Amplifier

DC Audio - 3.5k