What REW is (and isn’t)

Room EQ Wizard (REW) is free measurement software. It won’t make a mediocre design “audiophile,” but it will stop you from arguing with yourself about bass bumps that are actually the room — or a port that’s an octave off.

Minimum kit

  1. USB measurement mic with calibration file (or a known interface + mic)
  2. Audio interface or USB mic path you can calibrate
  3. Computer with REW installed
  4. Ability to play a sweep from REW to your amp/DUT

Prefer a calibrated measurement mic over a random headset boom. If you buy gear, the parts card below is an example merchant link we already use on this site — affiliate, disclosed. Soft until the rest of the kit list has real carts.

First useful measurement: near-field woofer

Goal: see what the driver+box are doing below ~200–300 Hz without the room dominating.

  1. Place the mic close to the dustcap / cone center (near-field).
  2. Run a sweep at a moderate, safe level — don’t clip the mic or amp.
  3. Look at the low-frequency shape: sealed rolloff vs ported peak/dip pattern.
  4. For ported: also mic the port and combine per REW near-field guidance when you’re ready.

You’re looking for: Does Fb / rolloff match your design intent? Weird notches often mean leaks, panel issues, or bad mic placement.

Second useful measurement: gated far-field (sanity check)

At listening height, 0.5–1 m on axis if space allows. Use gating/windowing so early reflections don’t invent fake treble. This is where you catch baffle diffraction and crossover suckouts — not where you “EQ the room” yet.

Distortion: a simple honest pass

REW can show harmonic distortion. For DIY:

  • Sweep at a realistic level, then a louder level
  • Watch HD climb at excursion-heavy bass notes
  • Don’t chase 0.001% — chase “does it fall apart when I turn it up?”

EEAT note (how we test)

We describe methods you can repeat. We don’t invent lab certifications. If a later “buyer guide” claims preference, it will list criteria (bandwidth, distortion behavior, build fit) — not vibes.

Common beginner traps

  • Measuring with AGC / “enhancements” on
  • No mic cal file loaded
  • Judging in-room bass without near-field context
  • EQ’ing a broken enclosure

Next steps

Enclosure sanity → then crossover checks. Pair with Enclosure mistakes that kill DIY speakers. More in DIY builds and the measurement primers on this bench.