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In Reply to: RE: Division of labor in PA system-More posted by tomservo on February 07, 2011 at 18:32:21
Thank you, Tom.
"In a room, one adds the fact that it is the total acoustic power and room absorption that governs the reverberant sound level for any given frequency."
That's pretty much what I was trying to say, though my wording may have been unclear. The application I'm looking at is in-room-only at this stage.
"Lastly, keep in mind that the theoretical peak output figure has nothing to do with how loud the system might actually go or how loud it can go and still sound acceptable."
Ah yes, I'm well aware that the real-world distortion-limited power handling is often far less than the thermal power handlng. I'm doing bass guitar cabs now, and fartout @ well below the rated power handling is a classic example of that.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Follow Ups:
Yes, room and people absorption will tend to make things sound "bass heavy", due to greater absorption at progressively higher frequencies. This is one reason why bands can get away with putting the subs on the floor but need to have the mids and uppers above the audience's heads.Getting to the directivity issue... Bands often have a hard time getting the system to sound "right" throughout the room. At the risk of giving away one of my sound reinforcement "secrets" ;) , this is often because the mids and uppers are too directional for the venue, and so I always designed systems to have wide dispersion as high up as possible. This improves both the direct sound and the reverberant sound, and makes it much easier to tune the system, and have people coming away saying "wow, that band sounded great!". Along that line, one thing I'd avoid is a 2-way 15" design. Inevitably, the crossover has to be much higher than a 15 should be used - they get too beamy.
Regarding the JBL system you mentioned... It's fairly easy to get a lot of output from the main boxes, which is one reason why you'll often see them capable of more output than the subs. It's not that the system is mismatched, it's just harder and more expensive to get lots of output at lower frequencies (but you already know that!), and so you'll see systems which have similar mids and uppers, but increasingly more "oomph" on the low end, as the price point goes up - effectively - it's beefing up the low end to "catch up" with the capabilities of the mids/highs. But, remember that the waveform peaks (especially snare drum, cymbals, and other fast rise-time sounds) are created by the mid and upper harmonics, so some extra headroom there is often necessary. This is one reason why so many systems which are driven to near their max levels sound so distorted - the peaks are clipped.
In a lot of ways, a really good sound reinforcement system is like a really good home stereo system - only bigger and louder. :)
Edits: 02/08/11
"At the risk of giving away one of my sound reinforcement 'secrets' ;) , this is often because the mids and uppers are too directional for the venue, and so I always designed systems to have wide dispersion as high up as possible. This improves both the direct sound and the reverberant sound, and makes it much easier to tune the system, and have people coming away saying 'wow, that band sounded great!'."
Dangit, that was gonna be MY secret!
I get to design the mains and subs for this system, so a lot of attention is being paid to the off-axis sound. Since this is an indoors-only system, that approach pays dividends in the oft-neglected reverberant field (at the expense of maximum SPL per dollar). Or so I theorize, not having done it on this scale before; must say that your experience along these lines is most encouraging. Thanks!
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
"In a lot of ways, a really good sound reinforcement system is like a really good home stereo system - only bigger and louder. :)"
+10
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