Which target curve to use in REW

Speakers are designed to measure flat in front of them in an anechoic chamber, where there are no reflections. Your microphone is not in an anechoic chamber. It hears the direct sound plus everything the walls, floor and ceiling send back, and how much the room sends back depends on frequency.

At low frequencies a speaker radiates in every direction, so the room receives a lot of energy and returns it. At high frequencies it beams forwards, so less reaches the walls. The sum is an in-room response that slopes gently downward from bass to treble, even from a speaker that is perfectly flat on axis. Add the bass that a small room builds up below 100 Hz and you get the shape every good target shares.

The analyser on this site judges tonal balance against a downward tilt of 0.8 dB per octave above 200 Hz, plus a bass shelf of up to 4 dB that is halfway there at 70 Hz. That lands in the same family as the curves that came out of Harman's listening research and the older Brüel & Kjær house curve. The values below are computed from the same function the analyser runs.

Only the shape matters. Absolute level depends on the volume knob and the microphone, so the analyser lines the measurement up with the target between 200 Hz and 2 kHz and judges everything else relative to that band. REW does the same thing with its Target Level control.

REW's EQ window builds its target from the Target Type you pick (Full Range, Bass Limited, Subwoofer or Speaker driver) and then adds either a room curve or a house curve file on top. A house curve file is the more exact of the two. It is a plain text file of frequency and offset pairs, one pair per line, separated by spaces, tabs or commas. This is the table above as a file:

20 3.3
40 2.6
60 1.9
100 0.9
200 0
300 -0.7
500 -1.4
1000 -2.2
2000 -3.1
5000 -4.1
10000 -4.9
20000 -5.7

1. 1.Save those lines as a .txt file.
2. 2.In the EQ window's target settings, load it as the house curve. An H appears next to the Target value in the Filter Adjust graph while one is active.
3. 3.Press Calculate target level from response, then check the target runs through the middle of the measurement, with the peaks you want to tame sitting above it.

Below about 300 Hz, fit the response to the target with cuts. That is where the room's resonances live, where the peaks are large and stable across the listening area, and where EQ does its best work.

Above that, use the target as a yardstick rather than something to fit filters to. The fine ripple up there changes every time you move your head, and narrow filters fitted to it make every other position worse. What the target is good for in the treble is checking the broad trend: if the whole top two octaves sit 3 dB above it, one gentle shelf is a reasonable correction.

The tilt is physics. The bass shelf is preference, and it is where most of the disagreement about target curves actually lives. Some listeners want 2 dB of lift, some want 8.

• Change one thing at a time. Try the bass shelf 2 dB lower and 2 dB higher, and live with each for a few days rather than switching back and forth in a single evening.
• Mind the volume. Hearing loses sensitivity to bass faster than to midrange as level drops, which is what equal-loudness contours describe. A target that sounds right at a loud listening level will sound lean late at night, and one that sounds right quietly will sound heavy when turned up.
• Leave the tilt alone unless the speakers are unusual. Very directional speakers such as horns or large panels measure with less slope in the room, and forcing a standard tilt onto them overcorrects.