Resistor across speaker
09-04-2004, 06:36 AM
#1
50 Watt CAFz'r
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Join Date: Jul 2004
Posts: 68
Hey Guys,
It is not as though I have a pressing need to do this, however, I was curious if it is a common practice.
If you have a speaker with a 4 ohm impedance and want more power from that speaker without wiring another 4 ohm speaker in parallel with it, is it common practice for an installer to wire a 4 ohm resistor across it?
The reason I ask is that it seems to be a common problem on a car forum that I belong to. The stock car speakers are 2 ohm. When guys want to upgrade only their speakers, they are finding that they lose power when installing an aftermarket 4 ohm speaker. If this is a common practice, what is the power rating of the resistor that is commonly used? (Watts)
It is not as though I have a pressing need to do this, however, I was curious if it is a common practice.
If you have a speaker with a 4 ohm impedance and want more power from that speaker without wiring another 4 ohm speaker in parallel with it, is it common practice for an installer to wire a 4 ohm resistor across it?
The reason I ask is that it seems to be a common problem on a car forum that I belong to. The stock car speakers are 2 ohm. When guys want to upgrade only their speakers, they are finding that they lose power when installing an aftermarket 4 ohm speaker. If this is a common practice, what is the power rating of the resistor that is commonly used? (Watts)
09-04-2004, 08:19 AM
#3
50 Watt CAFz'r
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Join Date: Jul 2004
Posts: 68
"the extra power goes to the resistor which just heats up."
Why in amplifer specifications is the output (RMS) rated higher when a 2 ohm load is connected as opposed to a 4 ohm load? By adding a 4 ohm resistor across a 4 ohm speaker are you not creating a 2 ohm load?
Why in amplifer specifications is the output (RMS) rated higher when a 2 ohm load is connected as opposed to a 4 ohm load? By adding a 4 ohm resistor across a 4 ohm speaker are you not creating a 2 ohm load?
09-05-2004, 07:42 AM
#5
2000 Watt CAFz'r
Join Date: Jan 2001
Posts: 2,026
^^^ Exactly.
And depending on the kind of amp you have you may lose power by doing that . . .
ie: An amp rated at 80 wrms @ 4 ohm also rated at 120wrms @ 2 ohm.
When dropped down to 2 ohm, the two 4 ohm loads will each receive half of the 120 given to the 2 ohm load (because both 4 ohm loads are required to make the final 2 ohm, they share the power). Therefore, the 4 ohm speaker would only get 60 wrms instead of 80wrms. In addition to this, the amp will be working harder because the load is lower.
End result, amp works harder & heats up quicker, and the speaker gets less power.
A resistor (Unless being used in a complex passive crossover) is never beneficial in wiring a speaker.
And depending on the kind of amp you have you may lose power by doing that . . .
ie: An amp rated at 80 wrms @ 4 ohm also rated at 120wrms @ 2 ohm.
When dropped down to 2 ohm, the two 4 ohm loads will each receive half of the 120 given to the 2 ohm load (because both 4 ohm loads are required to make the final 2 ohm, they share the power). Therefore, the 4 ohm speaker would only get 60 wrms instead of 80wrms. In addition to this, the amp will be working harder because the load is lower.
End result, amp works harder & heats up quicker, and the speaker gets less power.
A resistor (Unless being used in a complex passive crossover) is never beneficial in wiring a speaker.
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