Subwoofer Wiring

[christjared]

Hello,

I was wondering on differnt ways to wire 3 dual 4ohm subs. I know that if i wire each sub in a series and then parallel them together i would be getting a 2.67ohm load. I was wondering what would the impedence be if i paralleled each sub, and then paralleled them all together?

Thanks

JC

[michael hurd]

Way too low for most any amplifier known to man. Some exotic car amplifiers will drive rediculous loads like this.... 0.667 ( two-thirds of an ohm ) like the Incriminator Audio amps, Sundown Audio, and a few others.

[DrWho]

I would run every VC in parallel, so that each driver is a 2 ohm load...and then I would wire all 3 drivers in series, which will show 6 ohms to the amplifier.

What amp are you trying to drive these subs with? And in what kind of application?

[christjared]

I will be trying to do SPL comps with these subs. So its either a 2.67 or a 6 ohm load....hmmm

JC

[DrWho]

What kind of SPL competition is it? Like what are the rules?

The impedance of a driver is not flat, and it also changes with the

type of enclosure you put the driver in. For example (since this is the

easiest scenario), if you put the subs in sealed cabinets, there will

be an impedance peak at the Fb of the box. Attached are two plots of

the JL Audio 10w3 dual 4ohm in parallel configurations. One box is ~2

cubic feet and the other is ~10 cubic feet.

If you are allowed to limit the bandwidth that the subwoofer operates

over, then there is absolutely no reason that you couldn't wire

everything in parallel and operate only over the region of increased

impedance. After measuring cabin gain, it would be a balancing act to

find the enclosure size required to maximize output at the impedance

peak of the system.

As you can see, the impedance peak is about 18ohms (for the sane sized

cabinet). Three of these drivers in parallel would yield about a 6ohm

load to the amp when operated at that specific frequency. Since cabin

gain increases as you go lower in frequency and your amp puts out more

power into a smaller impedance, you can try to expand the bandwidth of

the amplifier to reach lower where the impedance is also lower. If your

amp is 2 ohm stable, then you could reach down to 31Hz where the

impedance of the system is about 6ohms. And for the ease of filter

design, you can go as high as 41Hz. If you're lucky, the cabin

resonance of your car will hopefully fall in this range too.

Anyways, if you're allowed to play test tones or burps or whatever, you

can just make yourself a CD that only has frequency content from

30-40Hz (in this example).

Btw, there is an advantage to running sealed cabinets over ported

cabinets....basically being that you're better able to slosh the air

inside the cabin (kinda like sloshing water in a bathtub). This

sloshing is going to get you the high SPL readings, much more so than

trying to play off resonances and craziness like that. Or at least

that's what I'm told by the experts - I don't quite understand how this

is to be achieved, but apparently that is what is happening (must be

something to do with the signals they play).

One thing to note....simulations (like winisd) are just simulations.

You will probably want to measure the actual impedance of your system

if you want to play it on the safe side...or narrow the bandwidth over which you'll operate (so like 35Hz to 45Hz).