Speaker cable length

@cakyol. My new lengths are 15 and 20 feet of 10g cable. 

Simao,

you will be fine with a 10 awg wire for those distances. No worries. 

Here is what I just personally did. Your mileage may vary.

I had my 2 power amps on the side. Therefore, my cable runs were about 10 feet for the front speakers and about 18 feet for the second set.

I decided to place my power amps in the center on the floor instead. This allowed me to shorten my cables in the front to 5 feet and the sides down to about 13 feet.

I am listening right as I write this. I can hear much more detail in material I am quite familiar with.

Shorter is better. The shortest is best.

I was doing a guitar session once at the Record Plant with a bigtime producer. (name dropping not necessary). This was probably 40 years ago. I brought my whole rig in including my full pedal board of effects. Each effect had a very short cable in between.

The producer asked me, "what the F* is that?" I said it was my rig.

He said, "Get rid of it". I said, What??? That's my sound, that's my tone".

He said, " No it isn't. The tone is in your fingers and not in all that crap on the floor".  He told me that he wanted me to stand right next to my Marshall, and use the shortest possible cord possible. I did this. And guess what?TONE CITY. Les Paul. 6 foot quality guitar cable. Marshall. 

Since then, I have never used any effects. None. The tone was indeed in my fingers. I only use transmitters now live, and if I am in the studio,...

Yep! Les Paul. Quality 6 foot cable. Marshall. Battaging.

Quality of cable is just as important as length of cable. (to me)

Enjoy!

Logic would dictate that if both the left and the right cables are the same in length, regardless of length, and all of the components provide equal balance in volume and tonality, then all things would be the same/equal.

Using one 5' speaker cable and one 15' speaker cable, no matter what, creates a set of different conditions. Now, you may not hear it, but it cannot logically be "balanced". 

You picked good cable with the 4S11 but there is a lot more to it than gauge. At higher frequencies inductance will dominate over resistance. The 4s11 is good in this respect. Worst case use 2 runs to half impedance.  People go gaga over damping factor but cable runs are normally a very small fraction of voice coil resistance and other impedances in the cross over.  Inductance at high frequeny of the cable can be impactful speaker dependent.