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Old 03-06-2004, 05:24 PM   #1
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What is the difference between an 8 ohm sub and a 4 ohm sub?
I just purchased a new RF Punch 3812 by mistake (8 indicating 8ohms) instead of a 4 ohm 3412. I installed it and it doesn't sound as loud as i think it should. I was trying to run it with a JBL amp at 4 ohm. I am going to try and return it for the proper one tomorrow without using it anymore but was curious what the difference is. Thanks.
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Old 03-06-2004, 06:42 PM   #2
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the difference is the ressistance. that may be why it isnt that loud because they arent getting enough power.
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Old 03-06-2004, 10:26 PM   #3
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Heres the deal: 8 ohm presents twice as much resistance than 4 ohm, so it will take a little more "gain" from a 4 ohm amp to make an 8 ohm speaker sound good. If you had an 8 ohm amp, it would sound okay.

To clarify a bit further, a 4 ohm amp powering a 4 ohm speaker will use about the same amount of electrical power from your car (alternator/battery) as a 8 ohm amp with 8 ohm speaker at same wattage.

The reason you don't want to use 8 ohm speakers with a 4 ohm amp is that for the volume you want, your chips need to run more power through them, which decreases their life, so it'* not recommended.
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Old 03-07-2004, 01:11 AM   #4
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hear a amp bridged with to 8ohm will=a 4ohm load total on the amp and 4ohm will equal a 2ohm load mine you that with 2 subs at hand
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Old 03-07-2004, 09:26 AM   #5
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u can do this as long as ur amp is 2 ohm stable
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Old 03-07-2004, 02:05 PM   #6
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most amps get the most power rated at 2ohms (thats if its stable to do so)
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Old 03-12-2004, 08:17 PM   #7
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You never stated which JBL amp you have. If you have one of the class D'* bp150. bp300.1 or bp1200.1 you will need a dual 4 ohm sub
If you have any of the othe BP series amps you will need the 4 ohm sub
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Old 03-13-2004, 12:12 AM   #8
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Whoa. Where'd TaylorD go? An 8 ohm sub will pull half the current a 4 ohm sub will.
To put it simply, ignore all the marketiing BS, when you bridge a 4 ohm sub, you will THEORETICALLY get twice the power out of your amp as you would with an 8 ohm sub.
When bridging an amp it sees half of the ohms (impedance) of your driver. Basic electical laws. Feel free to abuse me due to the fact I've had a few pops..
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Old 03-15-2004, 07:56 PM   #9
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Why not buy another 8 ohm sub and wire them up in parallel to your amp? Then you'll have a 4 ohm load and you'll be good to go.
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Old 03-15-2004, 07:57 PM   #10
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Also becareful with impedance...... the LOWER the impedance (i.e. the lower the number) the more 'work' the amplifier has to do...not the other way around. Running a 8 ohm sub with a amplifier that is rated for 4 ohms won't do any damage.
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