Members FinalFarewell Posted November 22, 2003 Members Share Posted November 22, 2003 Hey guys. I don't want to sound like a complete idiot, but it looks like I will. What exactly is dispersion or nominal coverage? What does it mean when it's 85x85 or 70x50? I have an idea of what it means, but I'd rather not assume. How would you arrange four trapazoidial (is that a word?) 90x50 boxes? I've been reading about putting one box upside down on top of another and turning it slightly... is this what you'd do? Thanks. Keith Link to comment Share on other sites More sharing options...
Members Audioeast Posted November 22, 2003 Members Share Posted November 22, 2003 these specs are simply the amount of dispertion the horn will have - so if it's 90/90 you will have great dispertion (wide) but you cant array them (more than 1 per side) if you have 60x90 then you can array them side to side but not one on top of each other (with the horns flipped to meet each other) if they are 60 / 60 then you can array both ways but 60 degrees will not work very well alone in a big room Link to comment Share on other sites More sharing options...
Members flanc Posted November 22, 2003 Members Share Posted November 22, 2003 Think of a garden hose nozzle. A 90/90 dispersion would be a wide mist only reaching things close to the nozzle, a 60/40 setting would tighten the pattern and throw sound (like water) farther. If you were to hold two garden hose nozzles next to each other (array) with a 90/90 dispersion, they would be seriously overlapping with the water droplets smashing into each other...same with sound. Link to comment Share on other sites More sharing options...
Members Scodiddly Posted November 22, 2003 Members Share Posted November 22, 2003 It means degrees of flare or spread. So 90x90 would mean 90 degrees for both vertical and horizontal, or 45 degrees from dead-center. 60 degrees would be narrower. The two numbers are for horizontal and vertical, since most horns can do different dispersion for those two axes. Not sure which is which for the "60x40", though. Link to comment Share on other sites More sharing options...
Members Kennykeys Posted November 23, 2003 Members Share Posted November 23, 2003 Originally posted by Scodiddly Not sure which is which for the "60x40", though. It's horizontal x vertical, and it's measured in degrees (as in 360 degrees.) Link to comment Share on other sites More sharing options...
Members FinalFarewell Posted November 24, 2003 Author Members Share Posted November 24, 2003 Thanks Scodiddly. That's what I thought it meant but I just wanted to make sure. The garden hose analogy just clicked with me. So I'm looking to get four JBL SR4732X boxes (dual 12"/3 way) with a nominal coverage of 90x50. How would you set those up? Would you put one upside down on the other? I'm just looking to make sure I'm understanding this properly. Thanks. Keith Link to comment Share on other sites More sharing options...
Members Drumtech Posted November 24, 2003 Members Share Posted November 24, 2003 Side by side would be most practical... Just splay them enough (butt ends touching) to avoid too much overlapping and / or cancellation... Link to comment Share on other sites More sharing options...
Members FinalFarewell Posted November 24, 2003 Author Members Share Posted November 24, 2003 Drumtech, Thanks. I was thinking that one on top of the other would make for a huge stack. Would putting them at a 90 degree angle work? That would seem logical to me but then again, I could be wrong. Thanks. Keith Link to comment Share on other sites More sharing options...
Members Scodiddly Posted November 25, 2003 Members Share Posted November 25, 2003 Basically you want to have the the faces lined up, to make a surface. You could have 2 wide and 2 high, which might be the best & most stable stacking scheme. Having the top cabs upside down so that the horns are closer together is a decent idea; it'll make the system act more like a point source. Whether that makes a dramatic difference is debatable, but I do a lot of little PA tweaks from theory anyways. What you get with the trapezoid shape is the opportunity to splay them out to increase spread, or point them all in the same direction for limited spread but longer throw. As long as the fronts are all together, the angle can vary depending on the room shape. That's basically where line arrays start. Link to comment Share on other sites More sharing options...
Members RickJ Posted November 25, 2003 Members Share Posted November 25, 2003 Originally posted by FinalFarewell Drumtech, Thanks. I was thinking that one on top of the other would make for a huge stack. Would putting them at a 90 degree angle work? A 90-degree horn means that the coverage is down 6dB at 45 degrees off center from each side. A 60-degree horn is down 6dB at 30 degrees off axis. Many trap boxes allow for a maximum 22 - 30 degree splay (while still coupling the lo-mid sections). That's plenty of angle to avoid comb filtering with a 60-degree horn, but not enough to prevent 90's from interfering with each other. Technically, it's better to stack the top cab upside down in a vertical stack because comb filtering is less noticeable in the vertical axis than it is in the horzontal. (IOW, people move side to side, but they rarely move up & down.) You can also flip one of the cabs upside down in a side-by-side arrangement as long as you can still get the lower horn about six feet off the floor. Best bet is to change the 90-degree horn out for a 60 or narrower. The 4732 comes stock with a 2381 horn, which is 90 x 50. Same horn that's used in the 4733's. The 2383 horn is an option on the flying version of the 4733. It's a 60x50. It may also be available as an option on the '32. Link to comment Share on other sites More sharing options...
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