You don't "bridge" the sub. You bridge 2 channel amps into a single channel. If you have two mono amps, you strap them (if they are strappable).

With subs, you wire the coils in series to raise the impedance. Add the coils together. So if you have dual 3 ohm coils, you will have 6 ohms nominal. If you have dual 4 ohm coils, you will have 8 ohms nominal. You wire the coils in parallel to lower the impedance. If you have dual 3 ohm coils, you will have 1.5 ohms nominal. If you have dual 4 ohm coils, you will have 2 ohms nominal. This works with other impedances and with quad coil subs as well.

 

You don't.

 

Not always true. I have an amp that is stable to .5 ohms so why wouldn't I wire up my driver at 1 ohm?

Did you read my Rane article above?

Not true. As long as you have a subsonic filter set right below the enclosure's Fb (tuning frequency of the port) then trunk open or trunk closed doesn't mean squat. If you don't have an SSF, then you risking your sub no matter the trunk's status. The driver unloads like it is free air when you send a signal below the enclosure's Fb.

 

so from my understanding.. I would need two 8w7's which is 3 ohm's each, wire it in a series to produce 3 ohms?

i wouldn't mind shelling out for another 8 but will the JL 500 be able to push both?? or should i get a JL 1000 to push both 8's?

according to my RF amp specs and JL sub Specs.. Do I need a different amp? or would i just have to wire it differently?

 

Are the 8w7's dual 3 ohm? Not only do you have to specify the nominal impedance of the coil, you have to also specify the number of coils. A pair of dual 3 ohm subs will end up with a final impedance of 3 ohms. Parallel the coils on each driver and series connect the drivers.

Like I said earlier, the JL500 will push a pair of these subs. Heck, it would push a dozen subs. But the 500w of power is spread among all subs connected to the amp.

Bridged into 6 ohms, your RF amp can push about 375w The difference between that and 500w is about 1.5db on paper. In real life, more like 1db or so of max output. To get get a 3db gain on output, you have to double the input power all else being equal. To double the output (10db gain) you have to have 10x the input power all else being equal.

 

Lots of good advice here as these guys know what they are talking about. Back in the late 80's early 90's I used to compete and did quite well against a pretty impressive field of cars. Most of your questions are pretty basic and I think that you will understand it all completely once the light bulb goes on.

 

Yes i'm slowly understanding. I only started off with mY IS following the DIY to install and make it work but never knew anything about how it works. I really appreciate it guys. I think i've got a good grasp of it. Google helps a ton too haha.

i'm gonna assume that its not a dual 3ohm if the audio guy mentioned it was cut in half. Instead of a new amp perhaps i will buy another 8w7 and have two in my useless back seat

Robert - when you said the 500 watt is spread for all subs does that mean if the amp was running at 250 watts rms, running two subs, each will be pushing out 250 watts? Or would it be "spread"/ split having only 125 watts pushed for each of the two subs?

 

Another question: i just watched a youtube video explaining paralle and series wiring.

My jl8w7 is a single voicecoil with 3ohm rating. I remember that the sub was wired in a reverse effect. Positive was hooked up to negative on my amp and negative on the sub was hooked up with the positive to my amp to work properly. When it was pos to pos and neg to neg the subwoofer bass Cone was going inward. Can someone explain why it was switched? Does that make it a "series" wiring or does that only apply to the dual voice coil??

 

If you reverse the polarity - and + of the speaker to the amplifier you are reversing the polarity and that is why the cone goes in instead of out. Sometimes wiring the speaker in the manner "Out of Phase" will result in the bass sounding smoother. Most decent aftermarket car decks have this built into them so you don't have to do it at the speaker or amplifier. It just takes the sub out of phase with the rest of the system.

Since you only have one voice coil you can't wire it into a series and can only wire it in parallel. You have to have more than one voice coil or more than one speaker in order to wire in a series.

 

very interesting... so lets say I had two 8w7's.. on one sub1, i would connect that negative to the positive on the other sub2. and vice versa. then on sub one i would take the positive and connect it to my amp and on sub2 i would take the negative to my amp. that would be series correct?? quite interesting the youtube video showed me.

http://www.youtube.com/watch?v=PQ3CQE_NB0c

 

First, subs don't push anything except air. They are an electro-mechanical transducer. They convert electrical energy to mechanical energy.

If your amp is pushing 250w into a pair of identical speakers, then each speaker is receiving 125w. That's why in line arrays, you wire up 64 10w speakers and hit them with a 500w amp (home theater type stuff) and they handle it without issue).

 

Mounted either in phase or out of phase, the cone goes both in and out. Normally, when a positive signal is sent to a speaker, the cone moves out. When a negative signal is sent to the speaker, the cone moves in. If the signal is a 50hz tone, the cone moves in and out 50 times per second.

Some amps have a phase control switch that does the same as reversing the wires. Others have a dial with adjustable phase. That is even more useful in that instead of being 0 degrees (in phase) or 180 degrees out of phase, it can be adjusted to anything in between those two.

 

RobertJ, I am just trying to keep it simple for a newbie to the car audio world.

 

This is one of the few times I think that the newbie is actually interested in learning. If it shoots over his head, come back in a few months and re-read it.

 

You really know your stuff, do you work in the industry or are you an engineer???