ADVANCED? SPL Readings (1 Viewer)

[AllanN]

I stumbled accross this thread that had SPL readings listed like this

10Hz +20.5
12.5Hz +16.5
16Hz +11.5
20Hz +7.5
25Hz +5
31.5Hz +3
40Hz +2.5
50Hz +1.5
63Hz +1.5
80Hz +1.5
100Hz +2
125Hz +0.5
160Hz -0.5
200Hz -0.5
250Hz +0.5
315Hz -0.5
400Hz 0
500Hz -0.5
630Hz 0
800Hz 0
1KHz 0
1.25Khz 0
1.6KHz -0.5
2Khz -1.5
2.5Khz -1.5
3.15Khz -1.5
4KHz -2
5KHz -2
6.3KHz -2
8KHz -2
10Khz -1
12.5KHz +0.5
16KHz 0
20KHz +1

From what I read its seems to test they are testing the DB level at specific frequencies to make EQ adjustments?
Am I at all on base with this subject? Or do I have no clue whta is going on?
Explanition anyone?

 

[Vince Maskeeper]

Yep

That's probably what they're doing. First you choose a median level (say 80db of SPL) and then play tones for each freq and measure how far above of below the 80db mark the tone is.

Many people do this, graph the response of their rooms (oddly, this has been a common "advanced" practice for years, but seems to now have trickled down to the dabbler crowd). Serach the speakers area for "House Curve" or "BFD".

One thing to note when doing so is that this technique of using sine wave and a spl meter is usually only effective for sub freq- as complexities of stereo speakers often make it more accurate to EQ with pink noise and an RTA. You can "graph" the upper stuff with tones- but if you're planning to use the graph to design an EQ- I'd start with the sub as it will be easiest.

The second thing is, the RS meter is a bit inaccurate in low freq-- so there is a correction chart available to let you know how to adjust your SPL readings at a given tone.

-Vince

 

[Wayne A. Pflughaupt]

From what I read its seems to test they are testing the DB level at specific frequencies to make EQ adjustments?

It could be, Allan, but that’s not what this particular table is.

This is the commonly used corrections table for the Radio Shack SPL meters that Vince mentioned, supposedly to adjust for the meter’s shortcomings.

The idea is to add or subtract the corrections figure to the readings the meter gives at a specific frequency. For instance, if you get a reading of 85dB at 100Hz, you check the corrections table and see you should add 2dB for a corrected reading. So your reading is actually 87dB.

And so on for the other frequencies.

Regards,

Wayne A. Pflughaupt