Need help with sub/amp

[Mike437 10+ year member]

So i bought a dmm and found that on each of the two terminals on my sub box is about .8-1.2 ohm. I did not install my sub but want to know if my subs are wired to a load of 1 ohm. The people who installed my subs messed up a little when they installed. They also used 22 gauge wire from the terminals to the amp, will be changing to 12 gauge once my package from knu comes in.

Back on topic, so the two terminals are connected to the amp in this way: 2 positive wires ( 1 per terminal per sub) is joined together at the amp to go into one slot of the positive amp, same goes for the positve.

What i want to know is is this is a 1 ohm load? Please let me know if you need any other info, pics are below

Pictures:

The two sub terminals:

The inputs on my amp:

Click to read more...

 

[johnson 10+ year member]

 

[shavenblazer 10+ year member]

Just pull the subs out and take pics of how they are wired.

 

[Mike437 10+ year member]

I understand that, i gave them that picture and asked them to wire the subs to that. A simple yes or no answer would be much appreciated. I am just confused of the fact that they used both terminals instead of joining the speaker wires inside the box. The subs are 4 ohm dvc, and at both terminals it is roughly 1 ohm using the dmm, so if you join the speaker wires at the amp what does that equal? 1 ohm?

 

[Mike437 10+ year member]

does anyone know?

 

[XanderMoser 10+ year member]

If there are 2 subs, 4 ohm DVC each, then I'm guessing each one has its coils wired in parallel, and put on a terminal. That would be 2 ohms nominal impedance each. DC ohm resistance ratings are usually lower than nominal impedance, don't worry about it. These put in parallel on the amp would make a 1 ohm nominal impedance.

 

[Mike437 10+ year member]

If there are 2 subs, 4 ohm DVC each, then I'm guessing each one has its coils wired in parallel, and put on a terminal. That would be 2 ohms nominal impedance each. DC ohm resistance ratings are usually lower than nominal impedance, don't worry about it. These put in parallel on the amp would make a 1 ohm nominal impedance.

Thanks a bunch, very helpful. I just want to be sure the subs are at there peak power, 1 ohm.

 

[Mike437 10+ year member]

but wait, i am really confused now. If each terminal is 1 ohm, doesnt that mean that if you combine the two you get 2 ohm? or is it when you join two 1 ohm positive they still equal 1 ohm? and same for negative?

 

[XanderMoser 10+ year member]

but wait, i am really confused now. If each terminal is 1 ohm, doesnt that mean that if you combine the two you get 2 ohm? or is it when you join two 1 ohm positive they still equal 1 ohm? and same for negative?

Each terminal is 2 ohms, because each subwoofer has two 4 ohm coils. And when you put the voice coils from each sub in parallel, it gives each terminal 2 ohms. Put those terminals in parallel on the amp and you get a final nominal impedance load of 1 ohm.

Here's another way to think of it.

You have 4 voice coils. All 4 ohms. They are all in parallel. Here's the equation for resistances in parallel:

R=1/((1/R1)+(1/R2)+(1/R3)+(1/R4))

R=1/((1/4)+(1/4)+(1/4)+(1/4))

R=1/(1)

R=1 ohm

Does that make sense now? I'll keep trying to explain it until it makes sense.

 

[Mike437 10+ year member]

Each terminal is 2 ohms. Because each subwoofer has two 4 ohm coils. And when you put them in parallel, it gives each terminal 2 ohms. Put those terminals in parallel on the amp and you get a final nominal impedance load of 1 ohm.
Here's another way to think of it.

You have 4 voice coils. All 4 ohms. They are all in parallel. Here's the equation for resistances in parallel:

R=1/((1/R1)+(1/R2)+(1/R3)+(1/R4))

R=1/((1/4)+(1/4)+(1/4)+(1/4))

R=1/(1)

R=1 ohm

Does that make sense now?

Yes that makes perfect sense, but why when i use the dmm on each terminal it reads .8-1.2 ohm? Is it only reading half of what the terminal is at? I am just confused over why my dmm says 1 ohm per terminal?

 

[XanderMoser 10+ year member]

Yes that makes perfect sense, but why when i use the dmm on each terminal it reads .8-1.2 ohm? Is it only reading half of what the terminal is at? I am just confused over why my dmm says 1 ohm per terminal?

The DC resistance of a voice coil is rarely going to be the same as the voice coil's nominal impedance. The nominal impedance is a number given to you to match a subwoofer with an amp. When the subwoofer is working (or any other speaker) the actual resistance of the voice coil changes drastically based on frequency. Your DMM is measuring constant voltage or DC, when in actuality the subwoofer is running on AC voltage. The resistance during operating a 4 ohm nominal impedance voice coil will be anywhere from 1 to 10 ohms, it varies. I believe the Fs of the sub is where its impedance is maximum.

 

[Mike437 10+ year member]

The DC resistance of a voice coil is rarely going to be the same as the voice coil's nominal impedance. The nominal impedance is a number given to you to match a subwoofer with an amp. When the subwoofer is working (or any other speaker) the actual resistance of the voice coil changes drastically based on frequency. Your DMM is measuring constant voltage or DC, when in actuality the subwoofer is running on AC voltage. The resistance during operating a 4 ohm nominal impedance voice coil will be anywhere from 1 to 10 ohms, it varies. I believe the Fs of the sub is where its impedance is maximum.

ok thanks, so basically i am running at 1 ohm?

 

[XanderMoser 10+ year member]

ok thanks, so basically i am running at 1 ohm?

yes. As close as I can tell without actually being there to triple check everything.

But if you subs really are DVC 4 ohm like you say, then I would say by your description and pics that there is a 99% chance that you're at 1 ohm

 

[Mike437 10+ year member]

yes. As close as I can tell without actually being there to triple check everything.
But if you subs really are DVC 4 ohm like you say, then I would say by your description and pics that there is a 99% chance that you're at 1 ohm

alright awesome, thanks. Yeah the subs are 2 12" Alpine 1242D, i asked the installer to wire it to 1 ohm and was just making sure he did what he was supposed to do. Thanks again