Re: JBL SRX / QSC PL236 underpowered?
As I've previously pointed out, the band own the PA. I'm their sound engineer. They do the gig with their PA or with one they hire in if their PA isn't big enough. All I'm trying to do is ascertain whether I'm getting the best out of the PA the band have currently, which will allow the band to hire a bigger PA less and save money.
I didn't think I was under powered. I've always done the gig properly, with the equipment at hand or hired in when I knew it wasn't going to be enough. In both cases, I've not had a problem. It was only when I started looking seriously at the spec of the amps and speakers that I began to wonder what was possible. At that point, I also began to question what the specs were actually telling me. Hence this thread popped up.
I don't see the maths as being important here. I know that's the right way to do it if you're being asked to spec a system for a certain application, but I'm not doing that. I will always use this system if it will do the job. I can't make the system any smaller or bigger. It is what it is, maths or no maths.
Hmmm... Having only got two tops and two subs, I run them one sub either side with the tops on poles. I don't really see how I could centralise the subs like that, so I've not considered it before.
Again, it's a moot point. The band will use whatever I decide. I'm the sound engineer and I'm running the PA.
Again, it's the bands PA. I'm a member of the band as the sound engineer. It's not a case of money or who gets paid what for what.
I'm none of these. I'm just a sound engineer that is confused by the way JBL have specified their numbers in the SRX manual and trying to get the best out of my amps because I'm not convinced the system is set up 'right' or the band will get the most out of it. In other words, all I'm really asking is, three fold:
1. If you had two JBL SRX718 speakers, how many subs would you run alongside them to consider the system 'correct' for rock type bands.
2. What power would you drive them with and how (mono bridged, stereo, what impedance?)?
3. Given the answers to the first two questions, how would you then use a couple of QSC PL236 amps as a best fit for those answers?
The 'application' that people have mentioned is purely; "to get the most out of the system without going daft, so that we can use the PA to its full ability and not hire a PA in as often."
I'm running the system bi-amped. That is, subs and tops. I have a dbx DriveRack PA on crossover duties. I wouldn't expect the subs to have to deal with full range. It's being done properly.
In the interest of spreading some understanding of the band and the type of gigs we are doing, here's the full collection of videos we have online. All were filmed on a Sony Z5E (go look it up - I'm not an amateur). The audio in all cases is straight into the camera mic (which probably costs more than most YouTube style cameras you normally see from amateur or semi-pro bands). So it's not exactly great, but it is more accurate than a lot of stuff out there.
Mama - UK 'all era' Genesis Tribute Band on Vimeo
I'm also running an X32 but I've yet to get chance to mix down one of the many multitrack recordings of a gig so that I can use superior audio for the videos. Shame that but I've just got too many wedding edits to complete professionally before I can dabble with the band videos. The videos are mostly of bigger gigs without our PA. The ones filmed at The Diamond are also not our PA. The most recent two are the JBLs, as are the early rehearsal videos. None of them are mixed on the X32. Hope you enjoy. 
The band are performing at The Cavern in Liverpool tonight, so if I get chance, I'll grab some static video with X32 multitrack audio.
