Amp Hook Up...Mono?

[mrsteve]

I have a Rockford Fosgate 150a2 and 2 RF Punch woofers each are 4ohm and can handle 100watts RMS. The amp puts out something like 37.5 watts x 2 RMS and around 70 watts x2 peak at 4ohms. Is it possible to wire this amp in a mono setup to the two woofers? I want somemore power and I don't really need stereo sound coming from my subs. This is my first amp install so I really don't know much about bridging amps and wiring them for mono. Thanks

 

[donquixote1014]

The easiest way you can do this is to run them in a combination of bridged/series. You can do this fairly easily and it will run at a 4 ohm load. You run the (+) positive lead from the amp to the positive lead on the first sub. You run the (-) negative lead from the first sub to the positive lead on the second sub. You then run the negative lead from the second sub to the negative lead on the amp.

 

[JTang]

Hi MrSteve,

Unfortunately, you can't wire your 4 ohm subs up in mono to get more juice. For that, you'd either need to get two 8 ohm subs, or dual voice coil 4 ohm subs. The example noted above is wiring two 4 ohm subs in series, which will then give you a total ohm load of 8. When wired in series, it's just 4+4=8. With the 8 ohm load, your amp will simply put out 4 ohms per channel, which is no different than wiring the subs up normally, one sub per channel.

 

[mrsteve]

Oh well. Thanks anyways.

 

[donquixote1014]

umm...no

wiring those two subs in series will bring it to a 8 ohm load. But then i had him bridge the 2 channels giving him a four ohm load in "mono" which is bridged mode. In mono most high end amps do put out a little more power. I'm not sure about RF but i assume they will also hold true to this. If you want a lower ohm load so you can get more power, you could run the 2 positives off of the subs to the positive of channel 1 and the 2 negatives off of the subs to the negative of channel 2. This will give you a 2 ohm load in mono which should give you about double the power. Check your amp specs to make sure.

hope this helps

 

[JTang]

Wiring in series like that gives a total load of 8 ohms for the amp. Yes, it will be bridged in mono, but only at 8 ohms like you stated before. He will still only get 37.5 watts x 2 or bridged, the 75 x 1 at 8 ohms. An 8 ohm total bridged load simply means that each channel will simply put out the equivalent of 4 ohms of power, the 37.5 watts RMS each channel. He CAN wire like you noted, but it's not going to give him any more power. You can't just assume that by bridging an amp, it's going to cut the total ohm (8)load in half (4) and that's how it works. It only happened to work that way for amps wired in *parallel* with 2 subs, noted in your second response. When I mean "happened" it's because it worked out mathematically, but under normal circumstances, you never just take all the subs add up the resistances and divide by two. Series is totally different.

If he wants to pull more power from the amp, meaning the 2 ohms per channel to get the 70-75 watts RMS per channel, the total bridged ohm load needs to be 4 ohms.

Your second suggestion, wiring in parallel is totally correct, but that specific amp isn't designed to work under those conditions, each channel being able to work at one ohm each.


[Edited by JTang on 08-03-2000 at 08:34 PM]