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#1 Canadian

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Posted 07 Jun 2018 - 12:47

Hey Mates,

 

 

 

I have an Alpine PDX V9 amp speced 500rms both in 4 and 2 ohms, I also have it running an Infinity 120.9w which impedence is switchable.

 

what is better?

 

 

1) run the sub 2 ohms with gains low but in 2ohm meaning harder on the amp ( I assume)

 

 

2) run the sub 4 ohms with gains relatively higher in 4ohms?

 

 

also when I take the T/S parameters for somereason according to the program and infinity's specs the 2ohm configuration results in a 3-4hz lower F3 & FC (not sure if thats anything to notice anyway but nonetheless its there I guess)


Edited by Canadian, 07 Jun 2018 - 12:47.


#2 frostbite

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Posted 09 Jun 2018 - 19:13

The lower the impedance the easier it is to drive, that’s why you have more power


Roanapur is an old Thai port in southern Thailand, where the deserters of the Vietnam war took refuge and were joined by the worst villains and criminals of the world.

Prostitutes, drug-addicts, mercenaries, killers and psychopaths of any nationalities compose the population of Roanapur.

 

 


#3 Canadian

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Posted 09 Jun 2018 - 21:26

The lower the impedance the easier it is to drive, that’s why you have more power



Not really in my case


The alpine pdx 2nd gen amps produce the same power in both 2ohm and 4ohm configuration.


The question is is it better to drive the sub in 2ohm mode and allow for a lower gain or 4ohm with higher gain but less stress

#4 Cristian

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Posted 11 Jun 2018 - 13:42

Not really in my case


The alpine pdx 2nd gen amps produce the same power in both 2ohm and 4ohm configuration.


The question is is it better to drive the sub in 2ohm mode and allow for a lower gain or 4ohm with higher gain but less stress

 

The amplifier will be more efficient drawing power with the 4ohm load. e.g. 4ohm load = 80% efficient and 2ohm load 60% efficient. That extra power is turned into heat.

You might find that some amplifiers have less distortion at 4ohm compared to lower too.

When you set the gain, you are setting it against the input voltage, the gain should be the same regardless of 2ohm or 4ohm loads.

 

If you have a choice of 4ohm and 2ohm, provided the amplifier has a regulated power supply (meaning it makes the same power at either load), go for 4ohm. If your amplifier doesnt have a regulated power supply, they tend to make more watts at lower impedance. In that situation you have to offset the gain in power vs the potential for more current draw on the system/potential for introducing distortion.

 

When I speak of distortion, we are talking tiny amounts, but if you have paid £1,300 for a Sony RSX-GS9, then you don't expect the performance of a £50 cd player.



#5 Canadian

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Posted 11 Jun 2018 - 14:43

The amplifier will be more efficient drawing power with the 4ohm load. e.g. 4ohm load = 80% efficient and 2ohm load 60% efficient. That extra power is turned into heat.

You might find that some amplifiers have less distortion at 4ohm compared to lower too.

When you set the gain, you are setting it against the input voltage, the gain should be the same regardless of 2ohm or 4ohm loads.

 

If you have a choice of 4ohm and 2ohm, provided the amplifier has a regulated power supply (meaning it makes the same power at either load), go for 4ohm. If your amplifier doesnt have a regulated power supply, they tend to make more watts at lower impedance. In that situation you have to offset the gain in power vs the potential for more current draw on the system/potential for introducing distortion.

 

When I speak of distortion, we are talking tiny amounts, but if you have paid £1,300 for a Sony RSX-GS9, then you don't expect the performance of a £50 cd player.

 

 

 

 

Hey Christian,

 

 

 

thanks for the help mate, this is exactly where I get confused, say your adjusting with the Digital Multi meter method.

your supposed to play a 50hz sinewave for the sub right? then do your math according to the ohms,square root etc.

 

 

well in this case to achieve 500rms on 2ohms I need to get 31.62v while on 4ohms its 44.73v and in the end these do not align to be the same setting on the gain dial.

 

 

 

am I looking at this wrong,making an idiotic misstake somewhere here :) (as usual) ?



#6 Cristian

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Posted 12 Jun 2018 - 14:29

Hey Christian,

 

 

 

thanks for the help mate, this is exactly where I get confused, say your adjusting with the Digital Multi meter method.

your supposed to play a 50hz sinewave for the sub right? then do your math according to the ohms,square root etc.

 

 

well in this case to achieve 500rms on 2ohms I need to get 31.62v while on 4ohms its 44.73v and in the end these do not align to be the same setting on the gain dial.

 

 

 

am I looking at this wrong,making an idiotic misstake somewhere here :) (as usual) ?

This sounds like the JL audio method. - This is a way to make a safe setting, but it isn't the only way.

http://mediacdn.shopatron.com/media/mfg/9013/media_document/dev_1/gainSetting.pdf?1314072349

 

If it is an amplifier with a regulated power supply, go for the highest resistance i.e. 4ohm.