The first thing you have to keep in mind is that the level of one set of test tones vs. the next that you use has no bearing on what EQ settings you may or may not need.
The second thing is that the receiver’s equalizer does not have the capability to accomplish what you’re attempting to do. You’re trying to fine tune the response of your system with an equalizer that’s merely a sophisticated tone control. You’d need a much more powerful and precise equalizer to accomplish an accurate system equalization.
Not that you can’t accomplish some improvement in sound quality with the EQ provisions you do have, but you need to first determine where in the frequency spectrum EQ might be needed, then weigh that against your equalizer’s capabilities – i.e., can the equalizer make an effective change where (and in the way) that it’s needed, or not.
To determine where equalization might be needed, you’ll need 1/6-octave test tones from about 30-20 kHz, preferably sine wave tones. There are various websites where you can find these. Also needed will be some graph paper to plot your readings, or even better, download the Excel Workbook from the
BFD Guide website. It’s mainly for measuring subwoofers, but it’s easy to modify for full-range measurements.
To make your measurements, first establish a baseline volume level. A good way to do this is to use the pink noise calibration tone the receiver has for adjusting the speaker levels of the various channels. Something between 75-80 dB is good.
Once that is done, play the test tones one by one, measure them with your SPL meter, and enter them on your graph paper or the Excel program.
After that, connect the dots to see what your frequency response looks like.
The thing to consider at this point is the equalizer’s capabilities. Keep in mind that this equalizer by its nature will cut a very broad path. In other words, it won’t just boost or cut specifically at say, 2.5 kHz. No, everything around 2.5 kHz, both above and below, will be raised or diminished with the EQ adjustment.
So, look at the graph you’ve made and the EQ adjustments you have available. Basically, what you’re looking for is rather broad (wide) depressions or peaks that are near one of the EQ adjustments you have available. You’re looking for an overall [/i]trend,[/i] even if there are small “ripples” present “inside” the broader peak or dip.
For instance, the graph below shows a broad dip between 1200-45 kHz, even though there are smaller dips and peaks in between.
If you see issues like this, that are centered at or near one of the EQ adjustments you have available, then you can make an improvement. This particular wide depression “bottoms out” at about 3 kHz. That’s pretty close to the 2.5 kHz EQ filter you have available, so if this was your response graph you’d be able to make an adjustment there. However, probably no more than 3-4 dB at most, because your filters are so wide that getting too aggressive would end up pushing the peaks at 1200 Hz and 4.5 kHz even higher. Just keep in mind that the objective is an
improvement in sound quality, not a picture-perfect graph. Improvements in sound quality can be accomplished with moderate eqaulzation.
Something like the peak at 1200 Hz in the graph above is an example of what you
wouldn’t be able to adjust, because it’s fairly narrow. Equalizing it down with the EQ you have would also pull down the substantial dips at 800 Hz and 2.5 kHz even lower.
Anyway – hope this helps. Good luck.
Regards,
Wayne A. Pflughaupt
