> Step by step
1. Find your listening position
1
The first step is to use a mic and a spectrum analyser to see what an even bass response looks like. Put your best condenser mic a couple of inches away from one of your speakers and use your DAW or a synth to send a sine wave test tone at 500Hz to that speaker only. Set up an input channel for the mic in your DAW and mute it.
2
Set the test tone and input level of the mic so that the level meters at around -12dB. Insert a spectrum analyser on the input channel, set it to ‘peak hold’ and slowly sweep the test tone from 500Hz all the way down. Take your time so that the analyser has time to register each frequency, and repeat the sweep two or three times.
3
Freeze the spectrum analyser display. You should see that the bass response drops away evenly. Typically, you might find the slope beginning at around 100Hz and dropping off 10dB by around 60Hz, then gradually plummeting nearer 40Hz. This will vary hugely depending on your mic and speakers, but we’re looking to see an even slope for comparison purposes.
4
Now move the mic to your proposed listening position, reset the tone to 500Hz and boost the mic input so that it still meters -12dB. Insert a second spectrum analyser and repeat the sweep procedure. Now freeze this second curve and you’ll probably see a few lumps and bumps in the journey from 500Hz down to 20Hz. If the trace matches Step 3, you’re sorted. If it’s lumpy, find a new position.
5
Draw a plan of your room and measure out the 38% points. Measure both length and width to give four possible options for our new listening position. (Of course, some of these points won’t be practical.) Once you’ve found a likely spot, move the mic there and put a speaker where it would be if you were monitoring from that position, then repeat the sweep and measure process.
6
After trying a couple of options, hopefully you’ll have found the place with the smoothest bass response curve. If there are any persistent humps you’ll need further bass/broadband absorption, but this will be the best listening position bass-wise, and you should build your control room around it. The next thing is to get your speakers correctly placed.