2ohm / 4 ohm + Subwoofer Dilemma

broguearcher

I've got this 10" DVC MOMO that I'm going to be hooking up shortly. I've never used a DVC sub before but I have read up online about wiring options. I realized though that I do have a problem that I'll need to get advice on.

The amplifier I have is only stable on bridged mode (150 WATTS) to 4 ohms. If I wire both voice coil in series?? then I'll be presenting the amp with a 2 ohm load and the amp can't take that in bridged....right??? In stereo mode, the amp CAN go down to 2 ohms and puts out 75 watts per ......

How should I wire the sub for best sound? Can I just ignore the one set of voice coils, go with the amp in bridged mode into the other voice coil and still get the same performance as I would if I were using a "standard" SVC sub?

Thanks!!

Sam

hoosier21

Each VC is 4 ohm, right?

What amp is it you are using?

I think I would just hook up one VC to each channel of the amp in stereo.

broguearcher

The amplifier is a Lightning Audio... I know, I know.... it's a piece of junk, etc... however, the amp has performed very well so far for me and I'm rather impressed.

Each of the voice coils is 4 ohms..... problem I see is though that the amp can't put that much out in stereo mode into 4 ohms. If I wire both of the voice coils together (in series?) and then run each of the stereo channels into the same line of input I'm thinking that each channel would then "see" a 2 ohm load. If this is the case, then what's the difference really in doing that compared to running the amp bridged?? 150 W X 1 channel bridged @ 4 ohms or 75 W X 2 channels in stereo @ 2 ohms.

Zen Dragon

broguearcher wrote:

Each of the voice coils is 4 ohms..... problem I see is though that the amp can't put that much out in stereo mode into 4 ohms. If I wire both of the voice coils together (in series?) and then run each of the stereo channels into the same line of input I'm thinking that each channel would then "see" a 2 ohm load. If this is the case, then what's the difference really in doing that compared to running the amp bridged?? 150 W X 1 channel bridged @ 4 ohms or 75 W X 2 channels in stereo @ 2 ohms.

broguearcher:
When you wire resistances in "series" they are additive. ie 4 ohms in series with 4 ohms = 8 ohms. 4 ohms wired in parallel with 4 ohms would give you 2 ohms.

Zen Dragon

Your problem unfortunately lies with your amplifier. Polk recommends a 200W minimum amp to drive this sub to a level where it is having serious impact. You really want an amp that is bridgeable to 200W or more that can drive into a 2 ohm load.
In your current configuration I would wire the voice coils in series per page 4 of the manual near the right hand corner. http://www.polkaudio.com/downloads/manuals/car/MM_2_Subs_Manual.pdf
This will give your ampliifer an 8 ohm load. You will not be driving 150W RMS into 8 ohms, but probably much closer to 75W. Even though you are bridged the higher resistance will cause the sub to draw less power. The sub will work fine in this configuration and give you some decent sound.
Ultimately your goal if you wish to fully enjoy this sub is to get an amp that will drive 200W or more bridged into a 2 ohm load. At that point you can wire the voice coils in parallel for the larger power draw.

Tour2ma

Do bridged car amps see half the apparent nominal load as is the case with home amps?

(He asked expecting the answer, "Yes. Circuits is circuits.")

Zen Dragon

Tour2ma is correct.
Anyway, had to revisit some technical info after Tours response, and a bridged amp will only see half the apparent load.
It also follows that an amplifier bridged will only be able to be operated at a load which is double the load of 2 channel. ie your amp is rated to drive 75W into 2 ohms stereo, but can only drive a 4 ohm load bridged.
That being said the amp appears to be clearly specifying that it's power will be 150W when bridged into a 4 ohm load. Even though the amp see's it as a 2 ohm load the mfr was specifying the O/P power into a 4 ohm load.
This being said, the power driven will be less into an 8 ohm load, regardless of the fact that the amp see's it as a 4 ohm load....Make sense?
Nice catch Tour. Made me have to dig back through some theory.

Tour2ma

Something I just learned from F1 a couple months ago about home amps. Suspected that car was no different, but now I know.

So he can bridge and wire the twins in series or go non-bridged and assign each it's own channel (as hoosier pointed out).

I don't see much difference... Coin flip?

Zen Dragon

I can't remember where, but I definitely read somewhere that dual voice coils should not be run off separate channels of an amplifier. It may have to do with the possibility of sending different signals, or out of phase signals to each coil with separate channels. Something along those lines.

Tour2ma

WTF do I know.... besides this should be in the Car Audio section anyway...

Completely missed that this was about a dual VC set up, but see what you are saying. Doesn't seem like using two ch's would damage except the quality of the listening experience.

So looks like broguearcher is left with bridging and wiring the twin VC's in series.

Zen Dragon

No damage likely to the sub, just degraded audio I suspect.
Agree, thread belongs in car audio.
WTF do we know bout a bunch o car audio. :eek: