dual voice coil 4ohm sub = 4ohm out? - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 02-22-2009
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dual voice coil 4ohm sub = 4ohm out?

I have a single 12" sub with dual 4ohm voice coils. My amp will be bridged to the single sub, and the amp handles 4ohms bridge, it will not handle 2omhs. How do I wire the sub in the box to make the 2 4ohm coils = 4 ohm to the amp?
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Old 02-22-2009
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this is my amp:
http://www.sonicelectronix.com/item_...k+LT980-2.html
Would it be better to just wire each voice coil to the different channels?
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Old 02-22-2009
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I think one voice coil to each channel would be better right? since my amp is 4ohm stable and if i put the coils in parrallel it will be 2 ohms = blow the amp, but if i wire them in series it will be 8ohms and the sub will have half the power. Right?
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Old 02-22-2009
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Correct, wire each VC to each amp channel. Just make sure they are phased correctly (+ to +, - to - for each VC).
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Old 02-22-2009
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Originally Posted by Takeda View Post
Correct, wire each VC to each amp channel. Just make sure they are phased correctly (+ to +, - to - for each VC).
No - don't do this.

Series the coils, and bridge the amp to the now "single" voicecoil sub.

If you wire each coil in stereo, the coils could fight eachother electrically if the left and right channels are destructively interfering.

Bridging the amp into an 8 ohm load will give you the same power output as running 2 independent 4 ohm speakers.
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Old 02-22-2009
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Originally Posted by Jp7 View Post
No - don't do this.

Series the coils, and bridge the amp to the now "single" voicecoil sub.

If you wire each coil in stereo, the coils could fight eachother electrically if the left and right channels are destructively interfering.

Bridging the amp into an 8 ohm load will give you the same power output as running 2 independent 4 ohm speakers.
WRONG Bridging the amp will give you higher current drive, but no more voltage. And with an 8 ohm load, you need more voltage to bring the current up with the higher impedance. If both channels are phased correctly, they will not be opposing each other!!

Last edited by Takeda; 02-22-2009 at 07:10 PM.
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Old 02-22-2009
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WRONG Bridging the amp will give you higher current drive, but no more voltage. And with an 8 ohm load, you need more voltage to bring the current up with the higher impedence. If both channels are phased correctly, they will not be opposing each other!!
I still disagree. Power = Voltage X Current

I had mine set up this way for a long time until I finally bought single voice coil 4ohm subs.
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Old 02-22-2009
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I still disagree. Power = Voltage X Current

I had mine set up this way for a long time until I finally bought single voice coil 4ohm subs.
But, you are forgetting, or don't know this equation for power:

Power = V*V/R

....and this is where the 8 OHM is going to kill your power, even if the amp is bridged......
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Old 02-22-2009
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But, you are forgetting, or don't know this equation for power:

Power = V*V/R

....and this is where the 8 OHM is going to kill your power, even if the amp is bridged......
I'm not going to argue - I still disagree.

To the OP: I suggest you email the manufacturer of the amp and ask.
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Old 02-22-2009
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I'm not going to argue - I still disagree.

To the OP: I suggest you email the manufacturer of the amp and ask.
To the OP, wire each VC up to the amp as I have suggested and you will be fine!

Obviously Jp7 has a very limited electronics background......
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Old 02-22-2009
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To the OP, wire each VC up to the amp as I have suggested and you will be fine!

Obviously Jp7 has a very limited electronics background......
Just an engineering degree... so b*** me buddy..

and oh.. 12volt agree's with me...

http://www.the12volt.com/caraudio/wo...s.asp?Q=1&I=42

Last edited by Jp7; 02-22-2009 at 07:46 PM.
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Old 02-22-2009
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I still disagree. Power = Voltage X Current
Not when you're talking about AC current on an inductive load.

It doesn't matter which way you wire it, really. Personally I'd do 8ohm one channel because high voltage low current means impedance rise is lower proportionally.
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Just an engineering degree... so blow me buddy..
You aren't very confident in yourself telling the OP to contact the AMP manufacturer!!!
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Old 02-22-2009
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You aren't very confident in yourself telling the OP to contact the AMP manufacturer!!!
I did that because I don't care. It's not my system. Now I'd rather just post in this thread just to aggravate you.
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Old 02-22-2009
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Not when you're talking about AC current on an inductive load.

It doesn't matter which way you wire it, really. Personally I'd do 8ohm one channel because high voltage low current means impedance rise is lower proportionally.
Your wrong too!! With an inductive load and AC, frequency is going to
determine current, and total power....With an inductive load, as frequency goes up, current is going to decrease.
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Old 02-23-2009
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Originally Posted by Jp7 View Post
Just an engineering degree... so b*** me buddy..

and oh.. 12volt agree's with me...

http://www.the12volt.com/caraudio/wo...s.asp?Q=1&I=42

Bad example!!! That's for a mono amp!!!!

Check No. 1 out, exactly as I suggested, and phased as I suggested:

http://colomar.com/Shavano/dvc_spkr_wiring.html


And you got your engineering degree in what???? I remember having to help you with powering up LEDs!!!



Last edited by Takeda; 02-23-2009 at 06:29 AM.
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  #17  
Old 02-23-2009
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Your wrong too!! With an inductive load and AC, frequency is going to
determine current, and total power....With an inductive load, as frequency goes up, current is going to decrease.
WTF? Where in the hell did you see me even mention frequency? Are you just looking up web pages and posting the stuff you read?
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Old 02-23-2009
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Whats all this talk about AC? I thought subs and speakers ran off of DC?? lol jk!
I called the manufacturer and the guy told me to wire each coil to a seperate channel on the amp. This is best way to get the most sound and performance out of your sub. If I put the coils in series, the 8 ohm load will only perform at half the power. I also went to a tech high school for electronics, and now Im in college taking some electronics courses for my IT major. And it does make sense. Simple resistor circuits, resistance equals force against current. More resistance = less current = less power. I just didn't know if it was safe it seams weird wiring one sub to two different channels.
Colomar suggested using a cross over with subs wired this way, but I won't need one right?
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Old 02-23-2009
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Originally Posted by rizoss16 View Post
Whats all this talk about AC? I thought subs and speakers ran off of DC?? lol jk!
I called the manufacturer and the guy told me to wire each coil to a seperate channel on the amp. This is best way to get the most sound and performance out of your sub. If I put the coils in series, the 8 ohm load will only perform at half the power. I also went to a tech high school for electronics, and now Im in college taking some electronics courses for my IT major. And it does make sense. Simple resistor circuits, resistance equals force against current. More resistance = less current = less power. I just didn't know if it was safe it seams weird wiring one sub to two different channels.
Colomar suggested using a cross over with subs wired this way, but I won't need one right?
The AMP manufacturer echo'ed what I said, and also what the site I posted said! You wire each VC to each channel of the AMP, keeping the phase the same. You DO NOT need cross-overs. Audio is AC, and falls within the 20HZ to 20KHZ frequency spectrum.

You are correct about the power....... P = V*V/R

Keep in mind that each VC in a dual VC sub are electrically isolated.
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Old 02-23-2009
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I was joking about speakers being dc by the way.
I put together my box with liquid nail caulk stuff. I didnt make the box from scratch, just took my dual box cut it down about 3/4 of its original size, took out the separating board inside to give myself a smaller box with more air space (for one sub). I blocked up the half hole from the other sub with 3/4 mdf board, and the side with the existing board. So now its connected with liquid nail. What size screws do i put in and do i pre drill first? How do I got about making the physical connections without splitting the wood?
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Old 02-23-2009
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Originally Posted by rizoss16 View Post
This is best way to get the most sound and performance out of your sub. If I put the coils in series, the 8 ohm load will only perform at half the power. I also went to a tech high school for electronics, and now Im in college taking some electronics courses for my IT major. And it does make sense. Simple resistor circuits, resistance equals force against current. More resistance = less current = less power. I just didn't know if it was safe it seams weird wiring one sub to two different channels.
Colomar suggested using a cross over with subs wired this way, but I won't need one right?
The manufacturer is, in general, incorrect.

An amp which can handle 4ohm bridged can handle 2ohm stereo.

Say an amp can do 50wx2 @ 2ohm, it can do 100w bridged at 4ohm.

If you put each channel on a 4ohm load your total power output will be 50w. 25w x 2. If you put a single 8ohm load bridged on the amp, total power output will be 50w.

The thing is, power limitations are usually current related (with maximum voltage being constant). The amp will be less efficient and (depending on the design of the amp) possibly put out less power at the lower load. However, in either case the differences will most likely be undetectable by ear.

Going back to impedance rise. The biggest cause of impedance rise aside from induction vs frequency is heat. Heat raises the resistance of the coils which in turn adds a constant amount of impedance. So if your impedance rise from heat is 1ohm that is a 25% rise on a 4ohm load but only a 12.5% rise on an 8ohm load.

:)
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Old 02-23-2009
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Originally Posted by CBFranger View Post
The manufacturer is, in general, incorrect.

An amp which can handle 4ohm bridged can handle 2ohm stereo.

Say an amp can do 50wx2 @ 2ohm, it can do 100w bridged at 4ohm.

If you put each channel on a 4ohm load your total power output will be 50w. 25w x 2. If you put a single 8ohm load bridged on the amp, total power output will be 50w.

The thing is, power limitations are usually current related (with maximum voltage being constant). The amp will be less efficient and (depending on the design of the amp) possibly put out less power at the lower load. However, in either case the differences will most likely be undetectable by ear.

Going back to impedance rise. The biggest cause of impedance rise aside from induction vs frequency is heat. Heat raises the resistance of the coils which in turn adds a constant amount of impedance. So if your impedance rise from heat is 1ohm that is a 25% rise on a 4ohm load but only a 12.5% rise on an 8ohm load.

:)

The minimum impedance an amp can drive in stereo or mono (bridged) depends on the amplifier. Some amps can handle a lower impedance in stereo mode, while others can handle a lower impedance in mono (bridged) mode.

As previously posted, the drive voltage will be the same in stereo or mono (bridged) mode, while the current drive is increased in mono (bridged) mode.

With the bridged specs on his amp, the RMS power @ a 4 ohm load is 560WATTS, which will be 280WATTS with a 8 ohm load, while it will deliver 220WATTS * 2 with a 4 ohm load in stereo mode. So, with each VC wired to separate channels on his amp, he will get 160WATTS more power, than the voice coils wired in series giving a total of 8 ohms in bridged mode.

And even with a 1 ohm increase in 4 ohm mode due to heating, this won't come close to the power being lost with 8 ohms.

Last edited by Takeda; 02-23-2009 at 04:35 PM.
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Old 02-23-2009
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Alright so we got the wiring down. Im all set with that. Now here's my modified box:





The two pieces I added are held together by a crap load of liquid nail caulk, I did it last night and the stuff still isnt dry. Now, what do I do, get some small wood screws and put those in?
For cosmetics...I am going to cut off the wood hanging over that was a mistake. But, can I paint over the carpet with spray paint? I was thinking about painting the box red, the color of my truck. Will this work? Or should I tear off the carpet and paint it? Or leave the carpet and just have that one spot where I patched up the hole without carpet? That is the side that will face towards the rear wall anyways.
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Old 02-23-2009
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There is supposed to be 1.5 cubic ft of air space, does that look like enough space? I am back at school for the week and once again don't have a tape measurer.
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Old 02-24-2009
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Originally Posted by Takeda View Post
The minimum impedance an amp can drive in stereo or mono (bridged) depends on the amplifier. Some amps can handle a lower impedance in stereo mode, while others can handle a lower impedance in mono (bridged) mode.

As previously posted, the drive voltage will be the same in stereo or mono (bridged) mode, while the current drive is increased in mono (bridged) mode.

With the bridged specs on his amp, the RMS power @ a 4 ohm load is 560WATTS, which will be 280WATTS with a 8 ohm load, while it will deliver 220WATTS * 2 with a 4 ohm load in stereo mode. So, with each VC wired to separate channels on his amp, he will get 160WATTS more power, than the voice coils wired in series giving a total of 8 ohms in bridged mode.

And even with a 1 ohm increase in 4 ohm mode due to heating, this won't come close to the power being lost with 8 ohms.
It's a Power Acoustik amp and those specs are a ****ing joke and probably no where near real world outputs. With out the ability to raise the voltage more than double when bridged, the amp CAN NOT make more power bridged at 4ohm than it can 2ohm stereo. Essentially when you bridge two channels the amp knows no difference between 4ohm bridged and 2ohm stereo.

For someone who likes to lecture people about electronics, you sure have minimal brand recognition.

Case in point, this little beauty of mine. These are real world, rested power outputs.

USamps USA-100:
2 x 52W @ 4 ohms
2 x 105W @ 2 ohms
2 x 158W @ 1 ohm
1 x 315W @ 2 ohms bridged

at 4ohm bridged it makes about 200w.

Bridging amps can work like this (higher loads have proportionally more power than you would think) but they can not work the way PA has stated in their specs except under certain, highly regulated conditions, and AFAIK PA does not use a regulated power supply because if they did, they may as well have the same power ouput 2-8ohm.

Last edited by CBFranger; 02-24-2009 at 09:48 AM.
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