Help needed choosing a design for live sound

[davygrvy]

There's a large jump in efficiency when you use many (small) speakers together. Here's an example of tapped horns (from Tom Danley)

many == good

 

[BP1Fanatic]

Nice!!!

 

[davygrvy]

I hope Pyroibw considers jbell's small cubes. Although the cost is a bit higher due to the need for more drivers, the end result is a more configurable system and is better on the back and will go louder compared to fewer larger cabinets.

 

[panjilaras]

on the outer cabs, the amount of delay is calculated from the outer distance the center stack?

 

[jbell]

on the outer cabs, the amount of delay is calculated from the outer distance the center stack?

umm... I'm not sure how to 'calculate' the amount of delay. Based on the edge to edge spacing of the mouths -- it's different. There is a maximum spacing edge to edge for subs to 'combine', and It is directly related to the upper frequency you want your subs to produce, however a good rule of thumb is about 4' or less. (the wider the spacing the more delay needed, however it will be somewhere between 1 and 4 milliseconds.)

What I did is use a spl meter and sine wave. Start the sinewave and measure straight on. Then move the spl meter to 45degree off axis. Start dialing in delay until the 45 degree off axis and straight on are about equal. As you add delay, at some point you'll start to hear a 'hollow' or weird kind of sound head on -- that's what tells you, you delayed too far.

 

[Top Shelf]

umm... I'm not sure how to 'calculate' the amount of delay. Based on the edge to edge spacing of the mouths -- it's different. There is a maximum spacing edge to edge for subs to 'combine', and It is directly related to the upper frequency you want your subs to produce, however a good rule of thumb is about 4' or less. (the wider the spacing the more delay needed, however it will be somewhere between 1 and 4 milliseconds.)

What I did is use a spl meter and sine wave. Start the sinewave and measure straight on. Then move the spl meter to 45degree off axis. Start dialing in delay until the 45 degree off axis and straight on are about equal. As you add delay, at some point you'll start to hear a 'hollow' or weird kind of sound head on -- that's what tells you, you delayed too far.

Its about 1.1 milliseconds per foot.

 

[jbell]

Its about 1.1 milliseconds per foot.

yea... I got that.
TopShelf Can you fill in this word problem?

edge to edge spacing = 2' in a 4 box group.
45 degree off axis is -6db down with no delay.
how many ms delay to make 45 degree spl = 0 degree spl at 40hz?

(hint, I know the answer for MY BOX only.... because I measured it. anyone else's box, no idea...)

just knowing the speed of sound doesn't help me 'calculate' the outer box delay.
anyone got any formula's that might help?

 

[Top Shelf]

Pythagorean theroum should Work. Depending on how far away the measurment is taken from test or listening point in front of the mmiddle or(reference) box.

 

[jbell]

Pythagorean theroum should Work. Depending on how far away the measurment is taken from test or listening point in front of the mmiddle or(reference) box.

ok, lets see if a2 + b2 =c2 comes up to the right answer.

30 feet measurement distance... measured in arc so its 30' head on, and 30' at 45degree off axis, measured from the center of the 4 box cluster. you have all of the numbers... lets see if you come up with what I know works.

btw, how does -6db relate to pythagorean theorum?

(bonus points for showing your work)

 

[Top Shelf]

Ill get back tomorrow really busy now.

 

[panjilaras]

hi jbell
that idea is covered in dave rat youtube video, live sound subwoofer configuration part 2.
dave shows us that if using virtual arc setup, by delaying outer stack consecutively, will sacrifice sound quality, less thump, slower low end attack.

 

[Top Shelf]

Jbell I've done some figuring and come up with something that looks promising. I have some more refining to do to make it as accurate as possible and maybe get it into an easy to use formula, so bear with me

 

[Osse]

Interesting discussion regarding widening horizontal coverage when adding delay to outer pair of a stack of four speakers horizontally.

I wonder if the stereo image could be widened even further if stacking the speakers in an inverted arc in accordance to picture #21 in Rogs paper, combined with delaying the outer pair of speakers?

http://www.voidaudio.pl/attachments/article/147/A Practical Guide To Bass Arrays (angielski).pdf

The difference at 100 hz is 3.5 dB more horizontal spl with the inverted arc compared to a straight stack without delay.

Sorry for necromancy.. ��