Tube amp bias adjustment advice

How about using your cell phone, buy a SPL plug in mic. Calibrate the mic and do a test or two. Quit guessing and see if one is actually louder than the other.

https://www.amazon.com/Dayton-Audio-iMM-6-Calibrated-Measurement/dp/B00ADR2B84/ref=sr_1_2?crid=3KHWP

ES posted this little mic and it works quite well. 19-20.00 usd

Order now and Prime usually gets it there in a day.
How are those ears? Make sure.

Most important, make sure you don’t have a speaker wired out of phase or something simple like that. A wire that is mismarked, or hooked up wrong.. Being that far off center is more than a balance issue.
Balance is time arrival, somehow that’s being messed with, right?
Phase shift, will cause a lower spl and late arrival..

Check for proper connection on the monitor section to the bass section.
Make sure they are in phase.
Check the SPL, make sure.. 20.00 one day...

Regards

You got the answer.. Don't ride home with the window down, there is all kinds of stuff, to help.. That use to really mess with my listening sessions.

Take care of your ears... Make a big ear for one ear.. really. Take your hat off, NO HATS... The chair back.., needs to be BELOW your neck.. 

NO Smoking, cheap tobacco, or weed. Gargle with warm salt water...

YUP, you know what makes a good mechanic?   One that takes care of their ears... and hands, ALWAYS....

Regards