Optimize before correction

An important point : before doing any correction, try to find best place for your loudspeakers, try different presets if you have and optimize as far as possible. Correction works best if you have less problems to solve.

Some steps are recommended before using any electronic correction :

  • if possible, do some acoustics treatments, ie absolutely avoid flutter echos at listening place : this is due to reflecting parallel walls, ie a window at your right and a bare wall at your left. Clap your hand and listen for a kind of zziiiing sound.
  • listen and do some measurements
  • look at low frequencies : especially avoid dips, those cannot really be corrected by EQ. If cancellation occurs, correction of +10dB on the signal also gives +10dB on the reflected signals, so cancellation won’t change !
  • maybe use a subwoofer to setup a 2.1 system : a subwoofer may be easier to place it at an acoustically good position, when main speakers do not have many possibilities with position
  • A tip about subwoofer place : acoustics is symetrical between source and listener, so you can swap both and have same response. Sometimes, it is easier to place subwoofer on a chair at listening place and listen at different positions in the room where the response is correct and so find best positions for the subwoofer.
  • If a bad dip is seen at listening position, try to know what is the room dimensins causing it and use well placed acoustic treatments but it is not so easy : at low frequencies, ie 80Hz, you need a minimum of 0.5m of absorbant thickness to be efficient. A membrane resonator may be less deep but you need measurements before tuning it to the good frequency. Another solution is PSI AVAA : those active bass-traps need no adjusment, can be very efficient but are quite costly (about 3500€)
  • If you have active filters, low and high frequencies adjustments, all kind of settings : first do measurements and try to come closer to recommended target response before correction with parametric or FIR filters.
  • Before using FIR correction, and especially when FIR is limited to 2048 taps or less, you can manually setup parametric filters in lowest frequencies (if your processor has both parametrics and FIR), ie under 100Hz. This could ease FIR correction. To set those parametric filters, you will find a folder REW in the 48kHz folder with wav files (L, R and LR). Import those files into REW (import audio datas), apply some smoothing and use the EQ automatically or manually. Use the correct equaliser : not allways easy if your own processor is not listed.