Channel Balance Tester
Verify your stereo left/right balance by ear. This channel balance tester works for both speaker balance and headphone balance — play alternating L↔R beeps (you should hear left, then right, equally), feed pink or white noise to one channel at a time, check that an equal-both signal sits dead-centre, and run an intentional offset test to confirm you can actually detect a small imbalance.
ℹ This is a listening test, not a measurement. It plays known signals through your whole playback chain — your speakers or headphones, the amp/DAC, and your operating-system or app balance/pan setting — so you judge balance by ear. The on-screen meter is drawn from the signal this page generates, not from a microphone, so it shows what is being sent to each channel, not what your speakers actually produce. It is relative: it cannot read absolute dB SPL, cannot prove the two channels are electrically matched, and a perceived offset can come from your hearing, room, or seating position as easily as from the gear. For a true channel-matching measurement use a calibrated SPL meter or a measurement mic with REW. Browser audio is stereo (2 channels) only — this tool cannot address discrete 5.1/7.1 channels.
Choose a mode and press Play. No microphone is used; nothing is recorded or uploaded.
This meter shows the level this page sends to each channel — it is not a microphone reading and does not reflect what your speakers actually produce.
How It Works
Stereo balance is simply whether the left and right channels reach your ears at the same level. When they do, a centre-panned sound (a lead vocal, a mono kick) appears to come from a point exactly between your two speakers or in the middle of your head on headphones. When one side is louder, that phantom centre image slides toward the louder side, and the soundstage feels lopsided — this effect is sometimes called "stereo image skew" or "pan law asymmetry." Using this audio balance checker, you get four ways to verify that, all generated in your browser with the Web Audio API and routed to your normal stereo output. The offset mode also doubles as a pan test: dial in a known dB difference to learn exactly how far off-centre a signal must be before you hear it. If you want to go beyond simple level matching and probe the full width and depth of your stereo field, the stereo imaging test covers phantom centre, soundstage width, and side-channel coherence.
The alternating beep mode plays one short sine tone hard-panned fully left, then fully right, over and over. Because the two bursts are produced from the same oscillator at the same level, any difference you hear — one side louder, quieter, late, or silent — comes from your playback chain, not the signal. The single-channel noise mode sends pink or white noise to the left only or right only by feeding two mono noise sources into a 2-channel ChannelMerger, which is the simplest way to address each channel discretely; it’s the fastest way to find a dead speaker, a swapped cable, or a stuck balance slider. Both-equal sends identical noise to both channels so you can confirm the image really centres. The offset test deliberately attenuates one channel by the dB you choose — useful to learn how big an imbalance has to be before you can hear it, and to sanity-check that you can hear one at all.
Two honest limits are worth repeating. First, what you are testing is the entire path: the operating-system or app balance setting, the amplifier or DAC, and the transducers, plus the room and your own hearing. A result tells you something in that chain is unbalanced, not which link. Second, this is a relative, by-ear check. The visual meter is driven by the gain values this page generates — it is not measuring your speakers — so it can confirm what is being sent but not what comes out. For a genuine, repeatable channel-matching figure in decibels you need a calibrated SPL meter or a measurement microphone with software such as REW, taken at the listening position.
A useful diagnostic sequence: start by checking your operating system balance slider (Windows: Settings → System → Sound → Output → Device properties; macOS: System Settings → Sound → Output → Balance). If it is centred and you still hear an imbalance, swap your left and right speaker cables or headphone channels to see whether the problem follows the cable or stays on the same side — if it follows the cable, the fault is upstream of the transducer. Integrated amplifiers and AV receivers often have a physical balance knob that can drift off-centre over time, especially in older units; cleaning the pot or reseating it can resolve a gradual one-sided fade. Persistent one-sided faintness that does not move with the cables can indicate a failing driver, a blown tweeter, or a faulty amp channel, all of which require service. For a more detailed sweep of your headphone drivers' frequency response by channel, try the headphone frequency response test.