Guide · Measuring
Room correction with an iPhone: what a phone measures well, and where a microphone does better
Yes, an iPhone measures a listening room well enough for room correction: its microphone is accurate where the room does most of its damage, in the bass and lower midrange, and audiolaz Room uses it to correct the whole range by default, fading out from about 13 kHz. Above 4 kHz the iPhone’s microphone is not linear, so the treble correction is approximate; a calibrated USB microphone (UMIK-1, UMIK-2, Dayton iMM-6C) is better there. Another phone corrects the bass, 40 to 500 Hz.
Updated by Alexandre Besson, who makes audiolaz. audiolaz Room is in beta.
How
Three points, at ear height.
- On the computer that runs audiolaz Room, open the app, and on the iPhone open the address it shows, in Safari (or use the audiolaz Room app for iPhone). Nothing else to install on the phone.
- Pick what to correct: the audiolaz corrector, which takes every source, or a Roon zone. Put the iPhone at your seat, at ear height, on a stand or something steady. Nobody in the seat.
- Set a loud listening volume. Three short sweeps: the seat, 50 cm to the left, 50 cm to the right.
- A measurement that is too quiet, clipped or spoiled by a knock is refused on the spot, with the reason. Do it again.
Three points rather than one keep the filter from chasing a detail that exists only at one spot in the room.
Which microphone
What each one corrects.
- An iPhone: the whole range by default, fading out from about 13 kHz. Above 4 kHz its microphone is not linear: the app says so and keeps a range that stops at 4 kHz, the sure part, one tap away.
- Another phone: 40 to 500 Hz, the bass, where the room matters most. Above, the speakers are left alone.
- A calibrated USB microphone: the whole range, fully up to 18 kHz and fading out by 19 kHz, lower in the bass too. It also lets the app align left and right in time and optimise the bass at the seat. See room correction with a UMIK-1.
Boosts stop at 2 dB with a phone, 3 dB with a calibrated microphone; cuts go to 12 dB.
Then
A filter, then a sound.
The app shows the response before and after against its target, with a score out of 100, then builds a minimum-phase FIR filter for those speakers and that seat. On top, a sound: Neutral, Balanced (bass +3 dB below 80 Hz), Warm (+7 dB) or Analogue (round and soft). It is played by the audiolaz corrector, whatever the source (Roon, AirPlay, Spotify Connect, UPnP, the Mac’s apps), or installed in Roon (DSP › Convolution, one preset per sound). Measuring and the result are free.
Then measure again with the filter on: the app lays what it measured over what it predicted.
Plainly
What a phone will not do.
- Accurate treble: above 4 kHz, the iPhone gives an approximation. For the treble, use a calibrated microphone.
- Fill a null: no microphone changes that; where two sound paths cancel, the filter leaves it alone.
- Correct the whole room: the correction is for the seat you measured.
Questions
Short answers.
Do I need an app on the iPhone?
No: the measuring page opens in Safari. There is also an audiolaz Room app for iPhone, if you prefer.
Does it work with an Android phone?
Yes, in its browser, for the bass: 40 to 500 Hz.
How long does it take?
About an hour the first time, installing the app on the computer included; a few minutes to measure again later.
Is a phone enough, or should I buy a microphone?
A phone is enough to start and hear what the correction does to the bass. A calibrated microphone is worth it for accurate treble, alignment in time and the bass optimisation.
A question this page does not answer?