# How to bridge 4 channel amp to 2 channels at 4 ohms



## carter_adcock (Jan 28, 2021)

I am buying 2 ds18 NXL-8M, and would like to run a Skar audio 75.4 amp with them, I am just wondering exactly how to wire these the best way to safely get the most power to the speakers that they can handle. I am normally a sub guy and never work with 4 channel amps.


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## lithium (Oct 29, 2008)

I dont see a switch to turn the amp into a 2 channel input mode so you will need a pair of RCA y adapters. Send the Left channel RCA input to ch1 and 2 using one of the Y adapters. Bridge the speaker output 1 and 2 for the left driver (see diagram in manual or on the amp). Repeat for the Right RCA input channel (use y adapter) to send signal to channel 3 and 4. Bridge 3 and 4 in the same manner to the right speaker.


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## carter_adcock (Jan 28, 2021)

What wattage would this method of bridging put each speaker at? I am still very confused on how to calculate the final wattage going to each speaker after bridging.


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## gijoe (Mar 25, 2008)

carter_adcock said:


> What wattage would this method of bridging put each speaker at? I am still very confused on how to calculate the final wattage going to each speaker after bridging.


The specs on your amp claim 250 watts per channel bridged. You don't need to calculate anything.


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## miniSQ (Aug 4, 2009)

I would not buy that amp if you don't already own it. Find a mono amp that is 2ohm stable.


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## gijoe (Mar 25, 2008)

miniSQ said:


> I would not buy that amp if you don't already own it. Find a mono amp that is 2ohm stable.


OP is trying to run some marine speakers fullrange, from the looks of it. As long as it's a fullrange mono amp, that's a good idea.


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## miniSQ (Aug 4, 2009)

gijoe said:


> OP is trying to run some marine speakers fullrange, from the looks of it. As long as it's a fullrange mono amp, that's a good idea.


woops sorry, i thought those were subs.


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## carter_adcock (Jan 28, 2021)

gijoe said:


> The specs on your amp claim 250 watts per channel bridged. You don't need to calculate anything.


Okay so if those speakers are 125 watts rms each, how would I get the correct power to them using that amp


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## miniSQ (Aug 4, 2009)

carter_adcock said:


> Okay so if those speakers are 125 watts rms each, how would I get the correct power to them using that amp


The spec sheet says the amp is bridgeable. So bridge it and turn the gain down. You can set the gain to less than the 250 watts x 2 its rated for.


RMS Power at 4 Ohms (Bridged): 250 Watts x 2 Channels (14.4v)


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## carter_adcock (Jan 28, 2021)

miniSQ said:


> The spec sheet says the amp is bridgeable. So bridge it and turn the gain down. You can set the gain to less than the 250 watts x 2 its rated for.
> 
> 
> RMS Power at 4 Ohms (Bridged): 250 Watts x 2 Channels (14.4v)


okay thank you very much!


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## e39 touring (Oct 19, 2012)

I set the full range gains by ear


Sent from my iPhone using Tapatalk


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## miniSQ (Aug 4, 2009)

e39 touring said:


> I set the full range gains by ear
> 
> 
> Sent from my iPhone using Tapatalk


me too!


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## e39 touring (Oct 19, 2012)

miniSQ said:


> me too!


Hell, my subs too....I’ll admit.
It helps during level matching via RTA as well.

I agree with bridging to your midbass. I’ve always had great results from the extra headroom.
150-200wpc ...any good midbass should be able to roll with that power available, Just need to listen for an unhappy driver.

Sent from my iPhone using Tapatalk


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## James19900909 (7 mo ago)

I think this is difficult


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## 96jimmyslt (Jan 31, 2011)

First check the manual. It might say how to bridge.

Take the positive from channel 1 and negative from channel 2...usually.


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