i got an ohm question....
11-16-2002
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i got an ohm question....
ok, my uncle was telling me that i have a messed up setup, he doesn't know that much about car audio, but from what i told him, he thinks i have the wrong equipment.
he says that a 4 ohm sub wired in series will get a 2 ohm load from an amp.
i have a 12W3-D4, so thats for 4 ohm, and my rockford 550X does 275 watts x 2 @ 4 ohms, if all this is right, what the heck is my sub getting right now? i am going to get a rockford 250M amp for my sub, and its rated at 250 watts x 1 @ 2 ohms.
i'm just getting confused, and i can't believe i did an install without knowing this basic info.
someone please, ease my mind, tell me i did my setup right, and that my uncle is wrong.
he says that a 4 ohm sub wired in series will get a 2 ohm load from an amp.
i have a 12W3-D4, so thats for 4 ohm, and my rockford 550X does 275 watts x 2 @ 4 ohms, if all this is right, what the heck is my sub getting right now? i am going to get a rockford 250M amp for my sub, and its rated at 250 watts x 1 @ 2 ohms.
i'm just getting confused, and i can't believe i did an install without knowing this basic info.
someone please, ease my mind, tell me i did my setup right, and that my uncle is wrong.
11-16-2002
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Rep Power: 0 ok... so this will take formulas here...
list the givens:
2 coils
each has 4 ohm impedance, therefore
R(coil1) = 4
R(coil2) = 4
series wiring : R(total) = R(coil1) + R(coil2)
in your situation, this is when you connect : (<-> = wired to)
+amp <-> +coil1 <-> -coil1 <-> +coil2 <-> -coil2 <-> -amp
so we put the formula into practice R(total) = 4 + 4
therefore, in a series wiring, your sub will get an 8 ohm impedance
parallel wiring : 1/R(total) = 1/R(coil1) + 1/R(coil2)
in your situation this is when you put all the positives together and all the negatives together
so ya take the formula: 1/R(total) = 1/4 + 1/4
1/R(total) = 1/2 , therefore R(total) = 2
parallel wiring will yeild a 2 ohm load
sorry for the excessively long explanation here, but i gotta practice it somehow, im studyin to be a high school physics teacher =)
list the givens:
2 coils
each has 4 ohm impedance, therefore
R(coil1) = 4
R(coil2) = 4
series wiring : R(total) = R(coil1) + R(coil2)
in your situation, this is when you connect : (<-> = wired to)
+amp <-> +coil1 <-> -coil1 <-> +coil2 <-> -coil2 <-> -amp
so we put the formula into practice R(total) = 4 + 4
therefore, in a series wiring, your sub will get an 8 ohm impedance
parallel wiring : 1/R(total) = 1/R(coil1) + 1/R(coil2)
in your situation this is when you put all the positives together and all the negatives together
so ya take the formula: 1/R(total) = 1/4 + 1/4
1/R(total) = 1/2 , therefore R(total) = 2
parallel wiring will yeild a 2 ohm load
sorry for the excessively long explanation here, but i gotta practice it somehow, im studyin to be a high school physics teacher =)
11-16-2002
#3
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[hr]Originally posted by: LudlamTheory
ok... so this will take formulas here...
list the givens:
2 coils
each has 4 ohm impedance, therefore
R(coil1) = 4
R(coil2) = 4
series wiring : R(total) = R(coil1) + R(coil2)
in your situation, this is when you connect : (<-> = wired to)
+amp <-> +coil1 <-> -coil1 <-> +coil2 <-> -coil2 <-> -amp
so we put the formula into practice R(total) = 4 + 4
therefore, in a series wiring, your sub will get an 8 ohm impedance
parallel wiring : 1/R(total) = 1/R(coil1) + 1/R(coil2)
in your situation this is when you put all the positives together and all the negatives together
so ya take the formula: 1/R(total) = 1/4 + 1/4
1/R(total) = 1/2 , therefore R(total) = 2
parallel wiring will yeild a 2 ohm load
sorry for the excessively long explanation here, but i gotta practice it somehow, im studyin to be a high school physics teacher =)[hr]
[hr]Originally posted by: LudlamTheory
ok... so this will take formulas here...
list the givens:
2 coils
each has 4 ohm impedance, therefore
R(coil1) = 4
R(coil2) = 4
series wiring : R(total) = R(coil1) + R(coil2)
in your situation, this is when you connect : (<-> = wired to)
+amp <-> +coil1 <-> -coil1 <-> +coil2 <-> -coil2 <-> -amp
so we put the formula into practice R(total) = 4 + 4
therefore, in a series wiring, your sub will get an 8 ohm impedance
parallel wiring : 1/R(total) = 1/R(coil1) + 1/R(coil2)
in your situation this is when you put all the positives together and all the negatives together
so ya take the formula: 1/R(total) = 1/4 + 1/4
1/R(total) = 1/2 , therefore R(total) = 2
parallel wiring will yeild a 2 ohm load
sorry for the excessively long explanation here, but i gotta practice it somehow, im studyin to be a high school physics teacher =)[hr]
cool, thats a great explaination. i guess i didn't know what series and parallel was, cause i thought i had my subs wired in series, but they are in parallel, all positives together, all negatives together.
so from your explaination, my 4 ohm sub is getting a 2 ohm load from the sub, is that correct?
so how many watts is my sub getting from the amp? i'm really confused now. if my sub is getting a 2 ohm load, and my amp does 275 x 2 @ 4 ohms, uh.....me=confused.
EDIT:
i looked at the specs on the amp again, 137.5 watts x 4 @ 2 ohms, which now makes sense, cause the rear channel is bridged for the sub, so 137.5+137.5=275watts, thats how the sub is getting a 2 ohm load, correct?
11-17-2002
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Rep Power: 0 When you have something wired in series, adding resistors increases the amount of resistance. In a parallel circuit, adding resistors decreases the resistance.
Man, it's scary that I know those equations... I learned them recently in my electricity & magnetism physics class.
Man, it's scary that I know those equations... I learned them recently in my electricity & magnetism physics class.
11-17-2002
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Rep Power: 0 I am running 2 12w3v2 D2s in my car off of a 500x. You shoukd have gotten 2 ohm coils, wire them in series with eachother giving you a 4 ohm load per sub, bridging the rockford at 275 per sub. With a dual 4 ohm you can eitehr run it in parallel at a 2 ohm load or series at an 8 ohm load. The rockford 550x is not stable bridged at 2ohms. you could technically run each coil to one channel of the amp but unless you have the gains absolute perfect you could damage the sub.
11-17-2002
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Rep Power: 0 And I don't knwo where you got the idea that dding resistors wil help. Yes you can change teh resistance but that means that the resistor is also now consuming power so it gets divided between the 2, and teh resitor will most likely overheat and pop.
11-17-2002
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Rep Power: 293 thanks for the info and help guys, and now that i know more about this, i feel like a dumbass. i should have done some more research before getting what i got.
whats done is done, i'm going to get a new amp anyways, leaving the 550X to power the fronts and rears, and getting a 250M for the sub.
250M specs are 125 watts x 1 @ 4 ohms and 250 watts x 1 @ 2 ohms, this is the correct sub for me, right? i dont want to get it and find out i made another mistake.
whats done is done, i'm going to get a new amp anyways, leaving the 550X to power the fronts and rears, and getting a 250M for the sub.
250M specs are 125 watts x 1 @ 4 ohms and 250 watts x 1 @ 2 ohms, this is the correct sub for me, right? i dont want to get it and find out i made another mistake.
11-17-2002
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Rep Power: 0 are you running just one sub? If so my bad. Yeah I guess the 550x would be a bit much power then. If it is just oen sub then the 250M is a good choice. I run a 750x for my highs (Yes I know I love overkill) and a 550x for 2 12w3v2d2 subs
11-17-2002
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[hr]Originally posted by: Abstract
are you running just one sub? If so my bad. Yeah I guess the 550x would be a bit much power then. If it is just oen sub then the 250M is a good choice. I run a 750x for my highs (Yes I know I love overkill) and a 550x for 2 12w3v2d2 subs[hr]
[hr]Originally posted by: Abstract
are you running just one sub? If so my bad. Yeah I guess the 550x would be a bit much power then. If it is just oen sub then the 250M is a good choice. I run a 750x for my highs (Yes I know I love overkill) and a 550x for 2 12w3v2d2 subs[hr]
hey abstract, how hot do your amps get? i'm surprised that my amp, after about 30 minutes of use at a decent volume, doesn't even get hot, its just warm to the touch. my friends have memphis, pheonix gold, kicker, and sony amps and they all are amazed at how cool my amp stays compared to theres.
11-17-2002
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Rep Power: 0 My amps stay pretty cool. The 750x is running boston 3 ways up front and rockford fanatic q seperates in the back which is way more power than needed. The 550x bridged to 2 12w3v2s can get a little warm, got hot once when I took a seriously long road trip but it will be in a covered amp rack with crossflow fans soon. But most of my friends amps get burning hot.
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