listening rooms

is there any specific size,longer than wide, rectangular vs square, how about height ? considering turning a bay in my shop currently 18 feet by 48 feet with 16 ft ceilings,is there a limit on size ? thanks robin
Square- NO! As total volume goes up, amplifier power to reach a specific sound pressure level goes up. 16' ceiling will be more than 2x the volume of a conventional room w 7.5' ceilings.
15'x 20' with an 8' ceiling is an excellent size for good sound.
I think your large room presents challenges but if you meet them, it should work very well.

Among the challenges are these:

1) Assuming your listening distances will be greater than in a normal room, the reverberant field will be stronger relative to the first-arrival sound. Since the reverberant field will be making a greater contribution to percievel timbre, you want speakers that do a good job in that area. If not, the timbre of voices and instruments will not be natural-sounding.

2) Your speakers will have to work considerably harder to reach a given loudness level in a room that big, so you want a speaker/amplifier combination that can get there without either becoming strained. Rated power handling alone doesn't tell the whole story; for instance, most woofers run into excursion limitations well before they reach their thermal limits.

3) A big room like that provides less reinforcement in the bass region than most speakers are typically "voiced" for, so most speakers will sound anemic in a room that large.

On the other hand, a large room results in long-length-induced delays before the onset of reflections. This is highly desirable from a psychoacoustics standpoint, and if this relatively late-arriving reverberant field is dominated by lateral reflectsions (that is, reflections off the side walls) the sense of "envelopment" or "immersion in the acoustic space" can be pretty spectacular. So if you can put together a system that addresses the challenges, the potential rewards are quite good.

Sorry, this is the one I meant to post:
would seriously consider running compression drivers in a volume this huge - you have a LOT of air to move therein
Are you asking what size room would be good to build inside
your shop building?That would give you different suggestions.
some clearification might be needed,i dont have to use this whole space,i can readilly put up walls lower ceiling etc.
If you are going to use the 70 watt monos you will need to shrink your room to something like what I recommended previously. If you put up walls you want something sturdier than just sheet rock if you want to hear bass.
The "Master Handbook of Acoustics" by F Alton Everest has exactly the info you're looking for.
looked at cardis web site,i believe i will build the golden trapagon,2x6 walls with osb instead of sheetrock,any other suggestion,thanks robin