A car test means playing your mix in a car, then on earbuds, a phone speaker and a Bluetooth speaker, to hear what changes away from your monitors. Each system exaggerates or hides a different part of the mix. The test is useful when you compare two versions on the same system at the same level, with a commercial track you know as a check. A mix that sounds different in the car is normal. A mix where the bass swamps the vocal in the car but not on your reference track points at a fix.
Why a mix sounds different in the car
Your studio, the car and a pair of earbuds put different speakers in different rooms. A car cabin is small and closed, so low frequencies build up and some bass notes ring louder than others. The speakers sit low in the doors and off to the side, so you rarely sit in the middle of the stereo image. Road and engine noise cover quiet detail, so reverb tails, soft backing parts and low-level automation can disappear.
Level changes the picture too. Ears are less sensitive to lows and highs at low levels (ISO 226, the Fletcher-Munson curves). A mix played quietly in traffic sounds thinner than the same mix played loud on a motorway. Keep the volume knob in one place while you compare, or you are comparing volume settings instead of mixes.
What each system reveals
Pick systems your listeners use. Four cover most of them.
| System | What it shows | Listen for |
|---|---|---|
| Car | Low-end build-up, masking from road noise, off-centre stereo | Kick and bass fighting, boomy notes, a vocal that drops under the band |
| Earbuds | Detail close to the ear, wide stereo, bass that depends on the fit | Harsh sibilance, panned parts that sound too far out, noise and clicks |
| Phone speaker | Little deep bass, a narrow or mono image | Whether the bass line still reads, the vocal level, parts that vanish in mono |
| Bluetooth speaker | Small speakers, often mono, often with added bass | Balance between vocal and drums, overloaded low mids, a mix that turns muddy |
Car
The car is where low-end problems show first. Play the chorus and listen to the kick and bass together. If one note of the bass line jumps out, that note may also be loud in the mix, or the cabin may boost it. Your reference track tells you which. If the reference has the same boom, the car causes it. If it doesn't, look at that note in the mix.
Earbuds
Earbuds put the sound straight into the ear canal, so they expose harsh top end, edits, breaths and noise that monitors at a distance can hide. Bass depends on how well they seal, so push them in and check the fit before you judge the low end. Hard-panned parts can sound further out than on speakers.
Phone speaker
A phone speaker can't play deep bass, so a sub-heavy bass line can disappear. If the bass part still reads on the phone, it has enough upper harmonics. Many phone speakers play close to mono, so this is also a quick mono check. If a part cancels or vanishes here, look at its stereo processing.
Bluetooth speaker
A small Bluetooth speaker usually plays in mono and often adds bass of its own. It shows whether the vocal sits on top of the drums when everything comes out of one small box, and whether the low mids turn to mud.
How to compare versions on each system
One listen to one mix tells you how that system sounds. Switching between two versions, and a reference, tells you what to change.
- Bounce the versions you want to compare, for example the current mix and one with the bass 1 dB lower. Add a commercial reference in the same style. See how to choose and use reference tracks.
- Match their loudness. A version 1 dB louder can sound fuller and brighter and win for that reason alone. The level matching guide explains how to do it by integrated LUFS.
- Set the volume once and leave it. Pick a level you would normally listen at.
- Play the same section of each version and switch at the same moment in the song, so you compare the same notes.
- Write down what you hear in plain terms: "bass louder than reference in the chorus", "vocal drops under guitars at 1:40". Fix those notes in the studio, then repeat the test.
In ABSeq, load up to four versions into A, B, C and D. Auto Gain turns every track down to the quietest one, and the A/B key moves to the next track at the same moment in the song. ABSeq keeps playing and switching with the screen locked, and the next-track control on the Lock Screen or in Control Center moves to the next version, over Bluetooth, wired headphones or car audio.
Switching without touching the phone
Set the comparison up before you drive, and switch only when parked or let a passenger do it. A sequencer that changes version on its own lets you listen without handling the phone. A whole bar (1/1) at 120 BPM switches every 2 seconds. To hear longer passages from each version, set a lower tempo by hand: at 60 BPM a whole bar lasts 4 seconds, at 30 BPM 8 seconds. The sequencer section of the help guide covers the tempo and division settings.
Reading the results
Not every difference you hear needs a fix. Judge each system against the reference track, not against your studio.
- If the reference and your mix both get boomy in the car, the car causes it. Leave it.
- If only your mix gets boomy, its low end is heavier than the reference. Compare the two on a spectrum or tonal balance graph back in the studio.
- If the vocal drops under the band on every system, raise it. If it drops only on one, check how the reference behaves there before you change anything.
- If one version wins on three systems out of four, take it, unless the fourth system is the one most of your listeners use.
When two versions are close and you can't decide, a blind A/B test on your main headphones settles it without your expectations getting in the way.
Questions
Why does my mix sound different in the car?
A car cabin is small and closed, so low frequencies build up and some bass notes ring louder. The speakers sit low and to the side, and road noise covers quiet detail. Play a commercial reference in the same car at the same level. If it changes the same way, the car causes the difference and the mix is fine.
What is a car test in mixing?
A car test is playing a mix in a car to check how it translates to the system many people listen on. Compare it with a reference track at the same loudness, note what differs, fix it in the studio and test again.
Why does my mix sound bad on a phone speaker?
A phone speaker can't play deep bass and often plays close to mono. A bass line with few upper harmonics disappears, and parts that rely on stereo width can thin out or vanish. If the reference track keeps its bass line on the same phone and your mix doesn't, add harmonics to the bass part.
How do I check my mix on earbuds?
Push the earbuds in so they seal, set a normal listening level and leave it there. Switch between your mix and a reference at matched loudness, and listen for harsh top end, sibilance, noise and hard-panned parts that sound too wide.