1)
Determine the voltage needed from the RMS output
The RMS output of the amp will
determine the voltage to set. Take the stated RMS from the manufacturer and
multiply that by the speaker resistance. The square root of that number is the
voltage to set the output at.
Voltage (RMS) =√(〖Resistance〗in Ohms ×〖RMS Power〗in watts )
So if the Amp is 200
RMS and the Speaker is a 4 ohm speaker the desired output voltage is 200*4=800
and the square root of 800 is 28.28. The ideal voltage output would therefore
be 28 volts.
The table below shows
the voltage at 2, 4 and 8 Ohms for common RMS outputs. Find your RMS on the
left and go to the column with the resistance of the speaker.
|
RMS |
2W |
4W |
8W |
|
150 |
17.32 |
24.49 |
34.64 |
|
165 |
18.17 |
25.69 |
36.33 |
|
175 |
18.71 |
26.46 |
37.42 |
|
200 |
20.00 |
28.28 |
40.00 |
|
225 |
21.21 |
30.00 |
42.43 |
|
250 |
22.36 |
31.62 |
44.72 |
|
300 |
24.49 |
34.64 |
48.99 |
|
350 |
26.46 |
37.42 |
52.92 |
|
400 |
28.28 |
40.00 |
56.57 |
|
450 |
30.00 |
42.43 |
60.00 |
|
500 |
31.62 |
44.72 |
63.25 |
2)
Next download a 50 or 60 Hz test tone. You can
also just stream it if you find one online. The longer the better.
3)
Next set your volume to about 75% of the maximum
volume. Turn your bass boost and amp
gain to 0.
4)
Take a multimeter and set it for A/C voltage. Connect
the probes to the speaker wires coming from the amp.
5)
Play the test tone. Slowly turn up the gain
until it matches the number from the table. The example above used 28 volts. At
28 volts the amp is putting out 200 watts RMS.
6)
Now hook the speaker wires back up to the
speaker and play a familiar song. Listen to make sure there aren’t any unwanted
distortions, hums, or buzzes. The system is tuned to about the maximum it will handle
so don’t increase the gain any more. The bass boost can be adjusted now and the
filters can be adjusted as well.
