What's ideal size for a listening room?

It's a stadium there i said it.has my favorite bands playing some of which are dead. Enjoy the music and find a room as big as you can get so you can put a big line array in. Many speakers make a choir. Not a soloist.

A case where bigger is better IMO. Any room with treatment and appropriate equipment can work. It’s not a case of blah blah mines the biggest and best it’s what you have to work with. Much is written, videos to watch, help is readily available the end result will be satisfying.

Cheers

Largest dimension of the room can determine the accurate reproduction of the lowest frequency of your audio system. At the sea-level where speed of sound is 1,130 ft/sec, longest dimension of the room should be about 56.5/2 = 28 ft to capture one half of the 20 Hz audio signal. This calculation is based on formula v = fxw where v = velocity of sound, f = frequency, and w = wavelength. 18 ft long room can reproduce 30 Hz and 14 ft one can reproduce 40 Hz accurately.  Your speaker specifications (3dB cutoff) can be used for this calculation. This is not a requirement for subwoofers as they reproduce lower frequencies by bouncing the sound off walls many times. Above theory applies only if you want accurate reproduction of the sound.

Show-boxed shaped rooms are subjected to many room modes where you will hear certain frequencies amplified at certain locations and dead spots on other locations. A trapezoidal shaped room can minimize most of these room modes. If you have room where roof/ceiling is at an angle, then it will most likely be a trapezoidal shape or one closer to it. I understand this may not be an option for some, but at least in theory those room shapes are better than shoe-boxed shape ones. 

This is just a start. Next you have room treatment which is a very big topic covered very well on this site. Do a search.

@pwerahera 

Thank you for the really Great reply and gives something to think about related to lower frequency waves in relation to room size.

I've done dirac sound analysis of the room and find that all frequencies seem to be coming through quite well and then when enhanced with DSP for home theater it makes a huge difference, really smooths out the curve.

Thanks

The bigger is the room, the better, just as simple as that.