Uncorrected Corrected
20Hz 76 83.5
25Hz 83 88
31.5Hz 81 84
40Hz 76 78.5
50Hz 73 74.5
63Hz 81 83
80Hz 86 88
100Hz 87 89
125Hz 85 85.5
160Hz 82 81.5
200Hz 82 79.5
250Hz 80 84.5
315Hz 84 82.5
400Hz 84 84
500Hz 84 83.5
630Hz 81 81
800Hz 82 82
1khz 81 81
1.25Khz 80 80.5
1.6Khz 81 81.5
2Khz 79 77.5
2.5Khz 79 77.5
3.15Khz 81 79.5
4Khz 82 80
5Khz 84 82.5
6.3Khz 86 84
8Khz 79 87
10Khz - -
12.5Khz - -
16Khz - -
20Khz - -

If you graph the numbers, there is a peak at 25Hz, a dip at 50 Hz, and another peak at 6.3Kh. A dip starts at 8Khz and continues down and off the scale from 10Khz to 20Khz.
Can anyone tells me what these numbers mean? Is it normal for speakers to fall off at 8Khz on? The only room treatments I am considering are Risch DIY tube traps and HF panels. Will these help?
Any suggestions would be greatly appreciated. Thanks.

You need to take it outdoors and do measurements. Indoors, reflections and stuff are completely wrecking your measurements. Move the microphone even half an inch in another direction, and you could get a completely different freqeucny response. Take 'em all outdoors and do measurements there, and make sure its far away from any surrounding walls to avoid reflections which will ruin your measurements.

Instead of using test tones and them measuring the SPL, a much more accurate way I'd reccomend to measure the frequency response of your system is to use a computer based program. Speakerworkshop is a program which runs on the computer and takes a number of various acoustical measurements including the freq response which you want to do. You can use your RS meter with speakerworkshop, just hook it up with the loop back cable to your sound card. Make sure your sound card supports the full functions in Speakerworkshop though, theres a test option in the program to test your sound card for compatibility. www.speakerworkshop.com

A large rolloff above 8KHz isn't "normal". It means theres a huge lack of the very highest frequencies, like cymbols and stuff. It should be very noticable when you listen to a system with the major HF rolloff and then one which doesn't.

What sort of speakers are you using? Have you also upgraded the mic in the RS meter to one which is flat? The mic in the RS meter actually has a huge rolloff above the same frequency which you noticed the big rolloff. Get the Panasonic WM-60AY from Digikey. Its about 2 bucks + shipping and linear right throughout the entire audio spectrum. I'd also reccomend putting the mic on the end of an external rod, so you can move the microphone around while having the meter seperate from it, as having your body near it introduces reflections too. It also makes it easier to use, so you can have the microphone placed way away and hold the meter in your hand and read it easily. See http://www.gti.net/wallin/audio/rsmeter/33-2050/33-2050.html for this microphone modification.

Adrian

The tube used for plumbing the cold water supply to a toilet is available in plastic, and it's the perfect size for fitting the Panasonic condensor microphones, including the WM-60AY. These tubes are about 20" (1/2 meter) long and work very well for this purpose. You can pick them up at just about any hardware supply store.

The capsule can be pressed in and it fits in snugly. Run a shielded microphone cable up through the tube and solder it to the tabs on the microphone so that the solder joints do not extend wider than the diameter of the capsule. Press the microphone down into the tube a little bit so that it is held firmly.

This makes a neat little measurement boom. One end is the microphone and boom, and the other end is shielded cable to RCA plug.