I know that 4ohms is 4 ohms,2 ohms is 2 ohms and those properties cannot change because of the motor structure of a given sub but I am curious if you could use a small 4 ohm DC electric motor wired to a 4 ohm SVC sub to achieve a 2 ohm load.
The reason I am thinking out loud about this is because most amps(Class D specifically)reach maximum rms output @ 2 ohms and many people including myself only use a single sub for a bass engine.
As I am typing I realize that to achieve this the DC motor would have to be wired parallel to the sub and amp and that would be 1 ohm.Hmmm..I dont know but there seems like there should be a way for the amp to see a 2 ohm load.
I am going to do some experimenting today on my bench to
see how close I can get.
Your comments would be appreciated.
Tell me I am an Idiot for thinking I can fool the ohms laws.
Mike
Replies (4)
compvr15s on 05/1/2004 12:32:32
i think there is a way to do this, im not to sure how it works, i think you need resistors and other technical things to change the resistance that your amps sees. i thnk i remember seening a reply that ttocs wrote to somebody a long time back about this but i may be wrong, wait for the pros on this. good luck
swez on 05/1/2004 13:31:03
There is a correlation between output power and resistance. However, any ohmic load that is used to drop the resistance to a given speaker, will also absorb some degree of power, based on resistance value (or impedance) of the new load.
You can use a 4 ohm resistor, but this resistor will have to handle the watts output of the amp it is being fed by. If we have a 4 ohm voice coil and add a 4 ohm resisor in parallel with V-coil, half the power wil go to the resistor and half will go to the V-coil. The net result will be more output power from the amp... YES.... but half of th total power the amp will put out, goes to the resistor in the form of heat loss. You will end up with less net power, going to the V-coil by doing this.
Example:
Amp puts out 75 watts RMS @ 4 ohm load
Amp puts out 125 watts RMS @ 2 ohm load
Since both loads are in parallel and of same ohmic value, they share 50% of the total wattage available from the amp.
125/2 = 62.5 Watts per device as they are in parallel right? So, in this case, we are actually losing power to the V-coil that would,stand alone as a 4 ohm load. We have lost 16.67% power using the 2 ohm load resistance.
Does that make sense to you Saint?
Swez COFFEE
saintanddolphin on 05/1/2004 14:15:12
Yes that makes sense.Correct me if I am wrong with this anaology: The amp is rated @ 200x1 @ 4ohms and 300x1 @ 2ohms.I would net only 150 rms @ 2 ohms versus a full 200 rms @ 4ohms because of heat dissapation by the resister.
Is that your point?
Is there a way to internally (bridge) modify the amp so that it sees a 2 ohm load?
The is an open topic for me.I am willing and hope others are taking notes(especially the future Golds).
If you care to expound further, I am listening.
Mike COFFEE
compvr15s on 05/1/2004 14:21:16
i think most of the class d amps are interally bridged like the jbl pb lines and the mtx class d lines that have 2 pos and 2 neg speaker inputs. so if you only use one pos and one neg it automatically gives all the power to the one side. but my 2 class d amps kicker kx600.1s only have 1 pos and one neg so im not sure how it works there.
The reason I am thinking out loud about this is because most amps(Class D specifically)reach maximum rms output @ 2 ohms and many people including myself only use a single sub for a bass engine.
As I am typing I realize that to achieve this the DC motor would have to be wired parallel to the sub and amp and that would be 1 ohm.Hmmm..I dont know but there seems like there should be a way for the amp to see a 2 ohm load.
I am going to do some experimenting today on my bench to
see how close I can get.
Your comments would be appreciated.
Tell me I am an Idiot for thinking I can fool the ohms laws.
Mike
Replies (4)
compvr15s on 05/1/2004 12:32:32
i think there is a way to do this, im not to sure how it works, i think you need resistors and other technical things to change the resistance that your amps sees. i thnk i remember seening a reply that ttocs wrote to somebody a long time back about this but i may be wrong, wait for the pros on this. good luck
swez on 05/1/2004 13:31:03
There is a correlation between output power and resistance. However, any ohmic load that is used to drop the resistance to a given speaker, will also absorb some degree of power, based on resistance value (or impedance) of the new load.
You can use a 4 ohm resistor, but this resistor will have to handle the watts output of the amp it is being fed by. If we have a 4 ohm voice coil and add a 4 ohm resisor in parallel with V-coil, half the power wil go to the resistor and half will go to the V-coil. The net result will be more output power from the amp... YES.... but half of th total power the amp will put out, goes to the resistor in the form of heat loss. You will end up with less net power, going to the V-coil by doing this.
Example:
Amp puts out 75 watts RMS @ 4 ohm load
Amp puts out 125 watts RMS @ 2 ohm load
Since both loads are in parallel and of same ohmic value, they share 50% of the total wattage available from the amp.
125/2 = 62.5 Watts per device as they are in parallel right? So, in this case, we are actually losing power to the V-coil that would,stand alone as a 4 ohm load. We have lost 16.67% power using the 2 ohm load resistance.
Does that make sense to you Saint?
Swez COFFEE
saintanddolphin on 05/1/2004 14:15:12
Yes that makes sense.Correct me if I am wrong with this anaology: The amp is rated @ 200x1 @ 4ohms and 300x1 @ 2ohms.I would net only 150 rms @ 2 ohms versus a full 200 rms @ 4ohms because of heat dissapation by the resister.
Is that your point?
Is there a way to internally (bridge) modify the amp so that it sees a 2 ohm load?
The is an open topic for me.I am willing and hope others are taking notes(especially the future Golds).
If you care to expound further, I am listening.
Mike COFFEE
compvr15s on 05/1/2004 14:21:16
i think most of the class d amps are interally bridged like the jbl pb lines and the mtx class d lines that have 2 pos and 2 neg speaker inputs. so if you only use one pos and one neg it automatically gives all the power to the one side. but my 2 class d amps kicker kx600.1s only have 1 pos and one neg so im not sure how it works there.
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