Hello guys,
I have built a PA box consisting of a horn and 2 15 inch woofers.
The horn is a 1.4inch B&C DE610 and the woofers are B&C 15NDL76, crossed at 1.8khz with a driverack. Woofers are high passed at 80hz.
My concern is with the woofers. They are wired in parallel giving an impedance of 4 ohms. It is powered by a QSC CX302 in bridge mode giving 1200watts. The woofers are rated for 500 watts RMS each totaling 1000watts. Im thinking that I can get more out of the woofers. They suck up all the power from the CX302 with ease...
I am thinking that my amplification could be better....
Im thinking of using a QSC RMX1850 or 2450 to get more power and dynamics out of the woofers.....
Good or bad idea???
Im open to suggestions.
Thanks all,
Lawrence
I have built a PA box consisting of a horn and 2 15 inch woofers.
The horn is a 1.4inch B&C DE610 and the woofers are B&C 15NDL76, crossed at 1.8khz with a driverack. Woofers are high passed at 80hz.
My concern is with the woofers. They are wired in parallel giving an impedance of 4 ohms. It is powered by a QSC CX302 in bridge mode giving 1200watts. The woofers are rated for 500 watts RMS each totaling 1000watts. Im thinking that I can get more out of the woofers. They suck up all the power from the CX302 with ease...
I am thinking that my amplification could be better....
Im thinking of using a QSC RMX1850 or 2450 to get more power and dynamics out of the woofers.....
Good or bad idea???
Im open to suggestions.
Thanks all,
Lawrence
Your two vulnerabilities are exceeding the max excursion which will damage the driver, and melting the voice coil.
Lookup the max excursion spec and use this calculator to help you to avoid exceeding it.
If the 500W rating is continuous power (sinewave) then the music rating would be higher. Check if the mfg specifies the normal usage power rating. Do not exceed that. Make sure the voice coil has as much ambient air for cooling as possible.
For 2 woofers in parallel the sensitivity is the rated sensitivity for a single driver plus 6dB. 3dB for having two drivers instead of one, plus another 3 dB for halving the impedance. But you can always add more woofers. Adding two more in series parallel would keep the sensitivity the same, but increase the impedance, thus cutting the current in half. This may be your solution if the 2 woofers still can't keep up with the horn.
Two things to keep in mind: If you run any machine at max power you will significantly shorten it's life, and the distortion of a driver increases with excursion, so it could be that running the woofers at full throttle will sound bad.
When considering max excursion, if you use 80Hz LR4 crossover, then the SPL will be -6dB at 80Hz, so your actual max excursion will happen at a higher freq above the attenuation of the HP filter. I don't know how to calculate where that would be. Somewhere 120-150Hz I would guess.
Lookup the max excursion spec and use this calculator to help you to avoid exceeding it.
If the 500W rating is continuous power (sinewave) then the music rating would be higher. Check if the mfg specifies the normal usage power rating. Do not exceed that. Make sure the voice coil has as much ambient air for cooling as possible.
For 2 woofers in parallel the sensitivity is the rated sensitivity for a single driver plus 6dB. 3dB for having two drivers instead of one, plus another 3 dB for halving the impedance. But you can always add more woofers. Adding two more in series parallel would keep the sensitivity the same, but increase the impedance, thus cutting the current in half. This may be your solution if the 2 woofers still can't keep up with the horn.
Two things to keep in mind: If you run any machine at max power you will significantly shorten it's life, and the distortion of a driver increases with excursion, so it could be that running the woofers at full throttle will sound bad.
When considering max excursion, if you use 80Hz LR4 crossover, then the SPL will be -6dB at 80Hz, so your actual max excursion will happen at a higher freq above the attenuation of the HP filter. I don't know how to calculate where that would be. Somewhere 120-150Hz I would guess.
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