how to find out where the main speakers roll off

[comet]

Give me step by step as to how to do it. Speakers say that the low cut off is 50Hz.

[Dudley]

Download test tones at

http://www.snapbug.ws/sinewaves/

burn them to a cd.

Play the cd and measure the tones gradually going lower. When the volume starts to drop that is where your mains roll off.

[comet]

what should i set the vol to

[Dudley]

Some medium volume should be fine. 85 dB is used on some setup discs, so that should be fine, and it won't damage your speakers or your ears. If you want to see how much output your speakers have at real low frequencies (20,25,30 hz) you should start even higher to account for sever drop in volume in the lower frequencies. I would try to keep from going much above 100 dB with the tones though.

Have fun, and keep us posted.

[comet]

still dont under stand explain more in how to do it

[Dudley]

Download the test tones. You could do 160, 142, 125, 100,89, 80, 71, 63, 56, 50, 45, 40, 36, 32, 28, 25, 22, 20, 18, 16. This would be 6 tones per octave (per halving of the frequency). See post 2 for the web address.

Burn the tones onto a CD.

Play the CD and set the level of the first few tones at 85-90 dB. Leave the volume control where it is set.

Play the entire CD and write down the level for each tone. Ie 160 dB 90 Hz, 142 Hz 89 dB (you will need an SPL meter)

Remember to add the compensation factors to your readings
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB

Just interpolate for the missing frequencies.

Draw a graph of your response. The point where the bass is -3 dB down from the average is where your bass starts to drop off. -10 dB you can easily notice, and -20 dB you are really loosing output.

You can do this from near the speakers (1 meter) or at your listening position.

Let us know how it turns out.

[comet]

ok u lost me in this part

[QUOTE]Play the entire CD and write down the level for each tone. Ie 160 dB 90 Hz, 142 Hz 89 dB (you will need an SPL meter)

Remember to add the compensation factors to your readings
16Hz add 11.5dB
20Hz add 7.5dB
25Hz add 5dB
31.5Hz add 3dB
40Hz add 2.5dB
50Hz add 1.5dB
63Hz add 1.5dB
80Hz add 1.5dB
100Hz add 2dB
125Hz add .5dB

Just interpolate for the missing frequencies.

Draw a graph of your response. The point where the bass is -3 dB down from the average is where your bass starts to drop off. -10 dB you can easily notice, and -20 dB you are really loosing output

im a little new so some of this is greek to me. i have a spl meter but still dont under stand it fully

[Dudley]

Oops I mixed up my dB and Hz. It should be 160 Hz and 90 dB in the first line.

So you play the CD and measure the volume of each tone, and that will tell you where the frequency drops off. The Radio Shack meter looses accuracy at lower frequencies, so you need to add the values I posted above to your readings to get the correct data.