Bridging a Polk 4000.4 amp

[sfjakey]

So I figured out my 2 Roswell tower speakers are being powered by just one channel of my Polk Audio 4000.4 amp. I’d like to try to bridge it and see if it improves the volume while surfing before I commit to new speakers.
my understanding of how to do this is I use a RCA splitter so that I use both RCA channels. I then connect the two speaker wires to the bridged connections on the speaker out put side. Is this correct? Finally, the amp has a 4 channel and a stereo switch. Would simply switching to stereo bridge the amp internally vs having to use the RCA splitters?
If I have to use the splitters, do I leave the amp in 4 channel mode or stereo?

[StormTrooperZ28]

Bridging the amp will double the output going to the speakers. But my first question is how is it wired up currently? If you are running 2 speakers to 1 channel than the ohm load on that channel is going to be too low. Can you snap a pic of the amp and wires? On that amp you should double bridge the amp and have the front 2 outputs bridged to 1 speaker and the rear 2 outputs bridged to the other speaker.
Also when you run a splitter on the RCA inputs you are cutting that voltage in half as well. Do you only have 1 set of RCA coming from your stereo to the amp, so 2 channels instead of 4 channel RCA's.

[sfjakey]

Yes, one rca to the amp. Amp has speaker wires in all 4 channels, but only 2 speakers are connected. It’s the way Nautique wired it so additional speakers are plug and play. I want to bridge the amp and just run one set of speakers. Is splitting the rca so I use both inputs necessary, or can I simply use the bridged speaker connections and switch the amp from 4ch to st and it will bridge itself internally?
Basically it is wired for 4 tower speakers but only 2 are connected and being used. The other 2 speaker connections are unused in the tower, but connected at the amp. Hope that makes sense.

[StormTrooperZ28]

Yes you are going to change it from 4ch to ST. But I don't think that will internally bridge the amp, it just changes the input from 4 RCA down to 2 to use the full amp. Does it show on the amp where the speaker wires go in, which (+) and (-) to use for bridged mode. You can remove the 2 extra set of wires coming from the amp that go to nothing in your tower (just remove them from the amp output and ziptie up, do not remove from boat) and then change the wiring to the current speakers for the bridged output.

[sfjakey]

So run the rca splitter to provide input to all 4 channels, then connect the speaker wires I am using to the indicated bridged speaker connections? Flip the switch from 4 ch to St?

[MLA]

Each tower speaker needs its own + and - wire at the amp. Does not matter if they where previously wired in parallel to one channel at the amp. Disconnect and set aside, the unused pre-wired wires.

Follow the diagram on the outputs to properly connect the bridged speaker leads.

Since you will need a pair of RCA splitters and populate all 4 RCA inputs, the amp needs to be in 4 chnl mode. This tells the amp you intend to use all 4 RCA inputs.

[sfjakey]

Thank you!

[TXtiki hut]

look up the polk 400 manual. it shows all the connections for bridging the amps. there are specific connections you have to run ie. front right to rear left.
from the manual, terminals that can be used in bridging mode are identified by the black and outlined boxes above each terminal.

it took a couple tries before i broke down and looked up the instructions.... now running 4 tower speakers off 2 polk 400.4 amps bridged.
sounds ok for the price of admission. running a polk 5 channel for the boat.