Connecting two Subwoofers to Naim Monoblock power amps amps

I am running my Naim 135 pair of mono block power amps with 2 subwoofers and my Naim SBLs. The subwoofers each have high level inputs for the left speaker and the right speaker. I have at present one 135 amp connected to the left input of subwoofer1 and the other 135 amp connected to the right speaker input of subwoofer2. I feel that the output level of each subwoofer is being set too high to achieve the volume I would like and that I am only utilising half of each subwoofer’s internal amplifier. Could I possibly bridge the left and right inputs of each subwoofer? Should I possibly run a second pair of speaker cables from the unused inputs of each subwoofer back to the !35’s outputs?
Any help would be appreciated here please.

I think it would be helpful to know the brand and model of your subwoofers but let’s assume that your subwoofers are similar to Rels in that they have a high level input designed to run direct off the power amp. As an aside: whether you connect the subwoofer cables directly to the power amp terminals or, alternatively, to the jacks on the back of your main speakers makes no difference at all except for some specific amp designs.

High level subwoofer inputs of this type are “measuring” the voltage across the main speaker wire and then using that information to drive the subwoofer power amp. Most, if not all, subwoofers have just one power amp section so that bridging is not possible. Bridging the L and R sub inputs could be easily done but my rather shaky electronics knowledge suspects that any increase in total voltage is exactly compensated for by the change in the effective input impedance.

Thanks for the input. The 135 mono block amps are connected each to a separate Martin Logan Dynamo 1100x subwoofer - see diagram. REL say to connect 2 subwoofers to 2 mono block amps that the live and neutral cables are commoner at each amp and the third black wire is connected to the 135’s chassis/earth.