First I would like to thank everyone for replying. While being a two channel enthusiast in 30 years i have never set up and configured an AVR. SO let me provide more info to help.
When you say tested do you mean listened or did you use an instrument to measure like an SPL meter (you can get an app with smartphones too)?
No I only listened by ear to various tv, movies etc. I did not measure any spl's as i have always tuned by ear. So not sure how or what id be looking for.
What is the subwoofer frequency response? If the subwoofer is fine with 100Hz, I would set the crossover there.
I imagine that nothing bad happens and that you won't notice a difference if you keep it at 80.
The subs are dual TBI modules which spec at
FREQUENCY RESPONSE 20 Hz –200 Hz (-6DB)
POWER CAPACITY 100 W RMS (175W IHF)
SENSITIVITY 90db 1w/1m @ 35Hz
IMPEDANCE 8 ohms nominal
Dont know if this changes our reply, but given this are you saying to try the center at 100 and leave the Fronts at 80 where they are?
If playing at high volume the 80hz crossover could cause some distortion to your center channel speaker since its specs is at 100hz....If that is not a concern then 80hz should be fine.
Other considerations to take into account on your AVR is the Center EQ as most up to date Yamaha AVR have it.....followed by SPL adjustments L/C/R....then Distance adjustments L/C/R.
I only noticed a hint of distortion coming from the center at 80...nothing dramatic .....
Re Center EQ: are you saying there may be a separate eq adjustment for the center channel. im only using a basic AVRX-683 and while i recall seeing general eq settings for YPAO, i dont recall one for each speaker. I will have to check. I doubt this basic model has that, but f so what am I looking for here?
RE other adjustments
Im totally a rookie here but after running YPAO with the yamaha flat eq i find that the distances set were very very accurate- kind of cool actually.
RE SPL not sure again here. Are you suggesting to get an spl meter app like the one suggested above and check that the spls are all the same or that in room measurements correlates with what the AVR automatically set ? This may be beyond my skills (cue Aragon reference) Even so the AVR has plus minus db on the basic menu...not sure how i would check to see actual spl numbers. With that said how would the spl measurements relate to the center cross over in general?