Will my 2 amps draw more current if I do this?

[WOT]

Im going to install 2 15" subs in my car. 2 audique SDC 2.5's. I can either power them with one cadence txa 1000D, run it to 1ohm and give the pair 1000rms (500rms a piece).

Or, because I have 2 txa 1000D amps, I can run the amps @ 2ohm and give EACH sub 650rms @ 2ohm

Now my question is, would an amp running @ 2ohm pulling 650rms, which is its peak rms for the ohm rating, with the gains up all the way use AS MUCH current as the same amplifier running @ 1 ohm pulling 1000rms.

Id like to know if they would use the same ammount of current because they are both being pushed to the limit of there ohm rating, or if pulling 650w compared to 1000w means it would only consume 65% of the current?

hard to explain, get what im saying?

Click to read more...

 

[boltpride 10+ year member]

Hell yea GAINS ALL THE WAY FTMFW!!!

 

[WOT]

Well, if my subs wants 650, and my amps can efficiently meet that power demand, why not? Not going to be clipping

 

[lil_italy773 10+ year member]

Hell yea GAINS ALL THE WAY FTMFW!!!

u know it the only way to go:laugh:

 

[goonandbuck 10+ year member]

i "which is its peak rms for the ohm rating"

"they are both being pushed to the limit of there ohm rating"

both of these statements make me think you dont know about ohms or current and you have no idea what your talking about

 

[goonandbuck 10+ year member]

Well, if my subs wants 650, and my amps can efficiently meet that power demand, why not? Not going to be clipping

thats not how it works, your amps dont put out what your subs draw. amps put out what they put out and your speakers can either handle it or not

 

[blackbonnie 5,000+ posts]

run 2 amps, and set the gains properly with no clipping

 

[Jando86 10+ year member]

you guys are sarcastic little meanies!

assuming your amps are 65-80% efficient class D, one amp at 1000 watts will draw less current.

two amps at 650 a piece will draw more current and its not worth the hassle of installing two amps for the extra 150 watts per sub (unless you want looks or your car can handle the extra load).

either way do not clip the amps! fedding distortion to your subs is not worth the marginal output.

I'm assuming you have two DVC 4 ohm subs here...

hope that helps

 

[WOT]

I really dont mind if BOTH subs @ 2ohm use more power than the single @ 1ohm pushing 1000rms

What I wanna know I guess is, in better terms:

Will a Cadence TXA 1000D @ 2ohm 650rms, full gain. Draw as much power as a Cadence TXA 1000D @ 1ohm 1000rms, full gain.

Ive had these amps in there before, strapped together making 2000rms @ 2ohm and my voltage was starting to drop below 13.5 @ cruise, so I just wanna know if the 2 amps @ 650rms on there own, would match or exceed that power draw

 

[WOT]

bump it

 

[squeak9798 5,000+ posts]

What I wanna know I guess is, in better terms:

Will a Cadence TXA 1000D @ 2ohm 650rms, full gain. Draw as much power as a Cadence TXA 1000D @ 1ohm 1000rms, full gain.

First, you appear to not understand the function of the gain. I can set the gain at "minimum" and, given I supply the proper amount of signal input voltage to the amp, still achieve full power output. So "full gain" is a rather meaningless addition to the question, especially since "full gain" could result in "horrible clipping", which is never advisable.

Second, it depends on the difference in efficiency between 1ohm and 2ohm operation. If there isn't much loss in efficiency @ 1ohm, then running both amps at 2ohm may result in slightly more current draw. If there is a large loss in efficiency at 1ohm, then running the single amp at 1ohm may result in slightly more current draw.

But as was mentioned, there won't be an audible difference either way.

 

[Phiber Optik 10+ year member]

Usually amps are most efficient at full power, so running at 1ohm (full power) maybe 75% eff. but running at 2ohm your only making 65% of full power so the eff. might be down to 50%

That said 1 amp (with 75% eff.) at 1ohm will draw 86.81 amps

1 amp (with 50% eff.) at 2ohm will draw 67.71 amps

so 2 amps at 2ohm will draw 135.42 amps! 56% more current then 1 amp at 1ohm!

This is in theory, and to be sure you need to see an efficiency vs impedence graph.

 

[squeak9798 5,000+ posts]

Usually amps are most efficient at full power, so running at 1ohm (full power) maybe 75% eff. but running at 2ohm your only making 65% of full power so the eff. might be down to 50%
That said 1 amp (with 75% eff.) at 1ohm will draw 86.81 amps

1 amp (with 50% eff.) at 2ohm will draw 67.71 amps

so 2 amps at 2ohm will draw 135.42 amps! 56% more current then 1 amp at 1ohm!

This is in theory, and to be sure you need to see an efficiency vs impedence graph.

I think you're confusing several different concepts.

First is varying efficiency based on different power output for a given load. Class A/B amps are generally more efficient operating at full power (for a given load) compared to lower power levels at that same impedance. An example would be an amplifier rated 100w @ 4ohm. When operating at full power output at 4ohm (100w) it's efficiency may be 60%, but at 1/3 power (30w) at the same impedance (4ohm) it's efficiency may only be 33%. This is not relative to other impedances. It's only relative to a different level of power output at a given impedance.

Class D amps generally don't suffer from this issue to the same degree as class A/B. It's efficiency will (generally) remain relatively the same over it's power band. A 100w class D amp that is 73% efficient at full power @ 4ohm will likely still be in the ~68%+ efficiency range operating at 1/3 power @ 4ohm.

The second is differing efficiency at varying loads. This is the 2ohm load vs 1ohm type of efficiency. This efficiency, for most amplifiers, will decrease as impedance decreases. So while an amplifier may be 73% efficient at 4ohm, it may only be 60% efficient at 2ohm and 50% efficient at 1ohm.

So if we combine these two concepts, we can get a general idea of how efficiency will vary for a given amplifier. If we decrease impedance, we can expect a lower efficiency. If we are operating at a reduced power level at a given impedance, we can expect a lower efficiency. An example of the combined efficiency for a hypothetical mono class D amp may look something like this;

Amplifier Efficiency @ Full Power: 73% @ 4 ohm; 65% @ 2 ohms; 58% @ 1 ohm

Amplifier Efficiency @ 1/3 Power: 68% @ 4ohm; 60% @ 2 ohm; 53% @ 1 ohm

For a hypothetical class A/B, it may look something like;

Amplifier Efficiency @ Full Power: 65% @ 4 ohm; 53% @ 2 ohms; 47% @ 1 ohm

Amplifier Efficiency @ 1/3 Power: 36% @ 4ohm; 33% @ 2 ohm; 30% @ 1 ohm

So in regards to the question at hand, we'd be generally inclined to conclude that the efficiency will be higher at 2ohm than at 1ohm, but of course we'd need to see measurements of the amplifiers to confirm this and to identify the degree to which they will differ. If there is a decently large difference in efficiency, the 1ohm operation may draw more current. If there's not much difference in efficiency, the 2ohm operation may draw more current since it's a slightly higher [rated] power level.

The above is a generalization, but typically accurate.

 

[94Mazda626 10+ year member]

^^^^^What he said

If efficiency is close:

Amps= power/(volts*efficiency)