New to BFM, planning a medium-venue system

[Bill Fitzmaurice]

http://eminence.com/pdf/kappalite-3012lf.pdf
"Watts 450W / Music Program 900W" - The limiting should be at which of those?.

IITP. And you can't limit to a watt figure, only to volts.

[Bruce Weldy]

http://eminence.com/pdf/kappalite-3012lf.pdf
"Watts 450W / Music Program 900W" - The limiting should be at which of those?

I also read somewhere that some people exceed their Xmax by 10% on subs since the distortion isn't a big deal, and the Xlim is still a safe distance away. Any truth to that? Probably not worth the stress.

450 watts for the 3012LFs. That's 60 volts. I've got mine set to limit at 56 volts using the Driverack. You won't hear distortion on these boxes - they'll just blow up. So, limit them below full power...and if you are doing that, there is no real need to buy the extra wattage if you aren't going to use it......

This is a departure from what you (and most of us) have always done with direct radiator boxes. I'm almost embarrassed by the tiny amps I'm buying to run these cabs. But, when someone marvels at how loud they are - I'm proud to tell 'em that they only get 450 watts.

Your thinking will change.

[sine143]

dude, I'm glad to tell my inquiring listeners that the tops only see 50 hehe.

[yeahforbes]

Haha, well it should sound equivalent to 1800W going through a conventional 99dB cab. Good news for the circuit breakers anyway!

So basically I could set my DriveRack limiter at say +14 dB (that lets it limit clean input by 6 dB since it's input stage clips at +20). Play a 60 Hz sine wave from a CD and let the dbx squash it. Put an AC voltmeter across the amplifier output, and then tweak the amplifier's attenuators until the meter reads the desired voltage*. Sound like a good gain structure? My board's outputs are close enough to the dbx's input range to not worry about aligning anything there, and when I see +14 coming out of my board I will know that I am just about to bump the limiters (save for any EQ boosts that cause earlier limiting).

*Does this reading change based on the load?

[Bruce Weldy]

Haha, well it should sound equivalent to 1800W going through a conventional 99dB cab. Good news for the circuit breakers anyway!

So basically I could set my DriveRack limiter at say +14 dB (that lets it limit clean input by 6 dB since it's input stage clips at +20). Play a 60 Hz sine wave from a CD and let the dbx squash it. Put an AC voltmeter across the amplifier output, and then tweak the amplifier's attenuators until the meter reads the desired voltage*. Sound like a good gain structure? My board's outputs are close enough to the dbx's input range to not worry about aligning anything there, and when I see +14 coming out of my board I will know that I am just about to bump the limiters (save for any EQ boosts that cause earlier limiting).

*Does this reading change based on the load?

Here's my opinion....

Hook up your tone generator to the board. Run up the volume of the tone until the board's main output meters register -0-. Turn the amps up to full volume. Put your voltage meter on the outputs and adjust the DriveRack until it hits the desired level of volts. Then run the fader on the board up even higher and see if the voltage stays where you set it. If it does, you are good to go. Then you know that when you hit 0 VU on the board, that's all there is and there ain't no mo'.

[yeahforbes]

Sounds good as well... running the board a little lower like that means each channel strip is farther from clipping too which is nice. I think it's quiet enough... Yamaha MG24/14FX. Occasionally borrow my friend's PreSonus StudioLive too (which is an AMAZING value by the way).

So if I have a voltmeter reading the output and then plug in a speaker without changing anything else, does the reading sag? If so, I guess I'd want to calibrate with the load connected (being extremely careful during the process).

[Bruce Weldy]

Sounds good as well... running the board a little lower like that means each channel strip is farther from clipping too which is nice. I think it's quiet enough... Yamaha MG24/14FX. Occasionally borrow my friend's PreSonus StudioLive too (which is an AMAZING value by the way).

So if I have a voltmeter reading the output and then plug in a speaker without changing anything else, does the reading sag? If so, I guess I'd want to calibrate with the load connected (being extremely careful during the process).

It doesn't change. Voltage is voltage. You don't want to do this with the speakers plugged in. First of all, it'll blow out your eardrums, secondly - hitting the speakers with a continuous sine wave until you get it limited properly will probably blow the speakers too.

I also run the same Yamaha board for the church band. I like it a lot, especially the built-in effects engines. I've been drooling over the Presonus boards too. A friend of mine has a big sound company and they are going with those for all of their small and medium rigs....probably for the big rig when they get the channel count up higher.