OT: How wide is a node in a room 15'x36'x7.5'?

[VolvoHeretic]

Watching DVD Pink Floyd concert; Pulse-1994-Earls Court-London, and wonder how wide the harmonic nodes are? I Can't really tell, but it sounds best about 2/5ths of the way from the speakers and standing up. About 100-105db, and I like it. Room is 35.34' long and 14'x18' jogging down to 10.5'x17.34' kitchen area, single slope ceiling height is 7.75'x8.75'. Do I need to paint racing stripes around the room to show where not to stand?

[mah]

This may help: Room modes calculator calculate 3 modes - app rectangular room control room eigenmodes eigenfrequencies formula frequency standing waves room acoustic node equation - sengpielaudio Sengpiel Berlin

or

play individual frequencies through your system, walk around, and use your ears as a guide.

It is a compromise in the end because each frequency has its own reflection pattern.

[GM]

Basic rule-of-thumb is for your speaker drivers, ears to be at odd orders, 1st, 3rds, 5ths, etc. in 3D.

If the speakers are pulled out into the room, them both the speakers and your ears should normally be at odd orders.

This holds true for high aspect ratio rectangular cabs [MLTLs] also, i.e. placing the driver at 1/3 and the vent at 4/5ths typically yields a smooth response needing little damping. There's some math I use that smooths this further in a sim, but I'm not sure there's an audible difference.

GM

[mah]

Drink a Fifth and all is mellow.

[VolvoHeretic]

Ok Mah, I input the average dimensions just to see what it would spit out-lots of numbers. I guess that nodes are what they are, I will mark out on the bare plywood subfloor the even and odd measurements and see what they sound like when I stand on that spot. Speakers are crammed into the corners.

I have ripped up the carpet and linoleum and am getting ready to place down PVC snap together flooring. The sub-floor consists of one layer of 1/2" plywood laid perpendicular to the 2x10 floor joist with 8d nails, covered with 5/8" plywood laid parallel to the joists with more 8d nails. All seams are placed on a joist and the perpendicular seams of the top layer are screwed to the lower layer at 8" o.c.

I have re-screwed the sub-floors down with #8 torx screws @ 8" o.c. There is a layer of construction paper between the plywood layers. I will be stapling another layer of 1/4" plywood underlayment on top of all of this. Will all of these layers of plywood vibrate and make noise?

Interestingly though, the nails nearest the speakers are working their way out.

[johnobub]

Use screws near the speakers.