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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through November 17, 2003 » Run Amp at 4Ohm Mono or 2Ohm Stereo « Previous Next »
By Chaun Keating (big_poppa_pump) on Wednesday, August 27, 2003 - 10:48 am:    Edit Post Delete Post
I have a Fosgate 550S that I am connecting to two JL Audio 10W3v2 Subs. The subs are dual voice coils so I can make each sub be 8 ohm or 2 ohm.

That said, I can run the two subs at 8 ohm in parallel and bridge the amp, then I am getting 550 watts at 4 ohms. So split 550/2 subs and I get 275 watts to each one.

Amp Spec: 550 W X 1 @ 4 Ohms Bridged RMS


I can wire the subs to be 2 ohms each and then run two channels to the amp (not bridged). I also would be getting 275 watts to each sub in this configuration. btw, the amp is stable at 2 ohms running two channels.

Amp Spec: 275 W X 2 @ 2 Ohms RMS

So which way seems better?? I would be getting the same wattage either way.

The two subs will have quite a bit of separation, so I am somewhat leaning to running the 2 channels at 2 ohms. Maybe its easier on the amp to run it at 4 ohms bridged though?


By matt (supraman) on Wednesday, August 27, 2003 - 11:44 am:    Edit Post Delete Post
The more you run speakers in series instead of parrallel, the more distortion you introduce. Your option of 2 channels has no speakers in series. The mono option is wired in series in three places (the voice coils on each sub and then the subs themselves). You should have a cleaner sound running in two channels. The trade-off is that your amp will be working harder and hotter to operate at two ohms.
By Chaun Keating (big_poppa_pump) on Wednesday, August 27, 2003 - 12:12 pm:    Edit Post Delete Post

Didn't know about avoiding series wiring due to distortion problems. You are correct about that.

I looked at multiple sources and there does not seem to be a distortion problem with wiring the dual voice coils of a subwoofer in series.

Also, in that case I would be running the two subs in parallel...not I do not see where the mono option has any series wiring (except at the voice coils)


This would be the wiring setup for two channel operation (not bridged) at 2 ohms.


By salty87 (salty87) on Wednesday, August 27, 2003 - 1:17 pm:    Edit Post Delete Post
i would avoid bridging the amp and go for 2 ohms on each side. in my opinion, bridging is harder on the amp...especially if it says it can run at 2 ohms.

By Mike Jolley (mikeski) on Thursday, August 28, 2003 - 12:21 am:    Edit Post Delete Post
Here impedence are the formulas:
series: Rt=R1+R2+R3+...
parallel: Rt=1/(1/R1+1/R2+1/R3...)
Rt is the total impedence (just like resistors in this case)

Most amps do not like to go below 4 ohms when bridged. If your speakers (or voice coils) are identical and in seperate enclosures series wiring should not cause any issues. You don't have to use both voice coils but performance may suffer. There is also a phenomena known as acoustic coupling that happens in stereo systems. While the amp may produce more electrical power bridged, actual acoustic output of the system will not be significantly reduced if you run it in stereo due to the coupling.

Bottom line... it is easier on the amp to run more impedence than less impedence.

By Chaun Keating (big_poppa_pump) on Thursday, August 28, 2003 - 9:48 am:    Edit Post Delete Post
OK, I think we are getting a little off the track here or perhaps I am not explaining myself clearly.

Either way I run this is perfectly in line with both the speaker and the amp manufacturer's reccomendations. Also, either way I run these I get the same wattage output allbeit at one single 4 ohm bridged or 2 separate 2 ohm stereo.

If you re-read the above posts:

1) If I bridge the amp mono it will see a 4 ohm load since both subs will be 8 ohms and wired in parallel.

2) If I don't bridge the amp, then I will run the voice coils in series, the subs will be 2 ohms, and I will be running a left and right channel separately to each sub at 2 0hms.

* I am NOT attempting to bridge the amp and run it at a 2 ohm load.

* I am NOT wiring separate speakers in series in any configuration.

All I was wondering is what the advantage/disadvantage of either configuration would be?

(Message edited by big_poppa_pump on August 28, 2003)

By Tim Krutz (timmy) on Thursday, August 28, 2003 - 10:50 am:    Edit Post Delete Post
amp bridged at 4 ohms is same load to the amp as running both channels at 2 ohms.
By salty87 (salty87) on Thursday, August 28, 2003 - 11:25 am:    Edit Post Delete Post
alright, that's one lap around....

i still say 2 ohms. i have an RF 800.4 which is 1 or 2 years older, i've been running it at 2 ohms on both sides since i installed it. i also used an RF 500.2 for my sub- JL 12w3dvc, and decided that 2 ohm sounded better than bridged....i tried both.

i don't like bridging amps. give both a shot and decide which sounds best to you.

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