Question

Which amplifier should you choose for the job?

You are a mobile sound guy/lady deciding on whether to pack a 150W/channel power amp (20 lbs) or a heavy 400 W/channel power amp (30 lbs) for your next gig. You will be traveling with 2 speakers with an efficiency of 30% (meaning it will output 30% of the power you supply to it).

You visited the site of your gig, and found out that you will need to have enough sound for people standing 50 feet (15.24 meters) from your speakers.

Answer 1

(Cont). As a professional, you know what sound level you want; you want to be sure that when you stand 50 feet away from the speakers, you measure a sound level of β = 100 dB.

You know from pre-calculus that the intensity of the sound decreases as you move away from the speakers according to the following formula:



where I is the intensity of the sound in Watts/meters2, P is the power coming from the speaker and r is the distance from the speaker in centimeters.
You also know from calculus that your sound level meter measures intensity (in decibels, dB) using the following formula



Which power supply would be best for the job? (provides the sound you need without burdening you on the road)