PVL and RMS.......

S

Steve Ferreira

Sophomore
Jan 12, 2011
189
0
16
Toronto, Canada
So I have decided to start using some more of the features in my IT8000s. I was just using the rms limiters set to the speakers rms. Speakers are SRX 725, 728 and 712.

So I had the rms set the following way.
1200w @ 4ohms for the 725s
2000w @ 4ohms for the 728s. I know it's not the matched rms on the spec sheet.
800w @ 8ohms for the 712s

I have set up the PVL in the following way, I'm being a bit conservative.
95v for the 725s = 2256w
110v for the 728s = 3025w
105v for the 712s = 1378w

Does the amp use the ohms from the rms limiters?
Does this look "right"? Should I get closer to the program power? Even though it won't make that much of an audiable difference.

TIA
 
Re: PVL and RMS.......

Steve,

Personally I'd set your RMS limiters at half that, at least. That 3dB isn't such a big deal to our ears but in terms of driver heating and power compression it means a lot. I would suggest the continuous (whatever the lowest power rating for the driver is) number as a maximum.

Your peak numbers are probably best determined experimentally, at least with cone drivers. The problem is whatever you set now with the driver "cold" will be meaningless after half an hour at a gig. As the voice coil heats up the resistance increases and you need to apply more volts to get the same driver movement... this is what power compression is all about. However, if your RMS limiting scheme can keep power compression low, then you can add those volts without overexcursing your driver. You need a reasonably accurate model of VC temp though, or else a good impedance reading, and I'm not sure you can do that kind of thing in the iTech amps (or any non-manufacturer-specific amp).

Long story short, I would tend to pick an RMS number that is low, and a peak number that is high. The more you have time to really screw around and see what your box does under duress the better you can set these numbers. For those peak numbers your amp rails are probably your limiting factor, when you take a pro driver and heat it up and lose 2-3dB to power compression... well, who has twice the amp rails to throw at it now? Not I, said the cow.
 
Re: PVL and RMS.......

Steve Ferreira said:
Bennett,

The speaker specs for the 725s are as follows: 1200/2400/4800. So your saying to set the rms limiter to 600w, and the pvl to 2400w?
Click to expand...
RMS at 600w for a 15" woofer is probably still going to cause you some power compression, but is a good starting point. I ASSume that the PVL could be 4800w or higher, but is frequency dependent and driver dependent and tuning dependent and... well, you get the point. If JBL thinks you can put 4800w into that box peak you probably can. The problem here is we're trying to drive a car by looking at a map, we're missing a lot of information and might just drive off the road anyway.
 
Re: PVL and RMS.......

That's why I was even trying to be conservative with my pvl numbers.
JBL's setting say for the 728s is 131v @8 ohms. That puts 2145w into each driver, or if you run the sub in parrallel like I do 4290w. The 728 spec sheet claims the following power ratings: 1600/3200/6400.

I have heard stories of people driving there srx rigs pretty close to program power with no problems. I'm not the type of person to drive my rigs hard or to the limit, if it's loud and comfortable in the venue then no need to go louder just because I have it on tap.
 
Re: PVL and RMS.......

Steve Ferreira said:
That's why I was even trying to be conservative with my pvl numbers.
JBL's setting say for the 728s is 131v @8 ohms. That puts 2145w into each driver, or if you run the sub in parrallel like I do 4290w. The 728 spec sheet claims the following power ratings: 1600/3200/6400.

I have heard stories of people driving there srx rigs pretty close to program power with no problems. I'm not the type of person to drive my rigs hard or to the limit, if it's loud and comfortable in the venue then no need to go louder just because I have it on tap.
Click to expand...

The VerTec 4880, version 4 presets for 80Hz crossover has a peak voltage limit of 120v. The nature of the program material we most frequently encounter is such that I'm more worried about the peak voltage (excursion) than I am about long-term power handling, most of the time. On the rare occasions I've set the RMS power limits, I've used numbers smaller than the continuous transducer rating. How much? That's proprietary, and subject to change... ;)

Have fun, good luck.

Tim Mc
 
Re: PVL and RMS.......

Thanks for the reply so far guys.
Most of the stuff I do is with a live band, and I go the ocassional DJ gigs. I'm the only person that drives the rig, I just want to "try" and make it as bulletproof as possible.
 
Top Bottom