Learn — By WATMM Desk —
Is my mix ready for mastering? A delivery checklist built from studio specs
Your mix is ready for a human mastering engineer when it is a lossless 24-bit file at the session sample rate, peaks a few dB below full scale with no master limiter, and you are no longer changing balances. Here is the checklist, compared across five published studio and service specs, and every check can be done with free tools.
Key facts
- Abbey Road asks for uncompressed WAV or AIFF, ideally 24-bit, 44.1 to 96 kHz, no limiting or normalising, with -6 to -3 dB of headroom as a guide.
- Chicago Mastering Service prefers 24-bit WAV at the native project sample rate, asks for at least 2 dB of peak headroom, and says not to sample-rate convert.
- Sage Audio suggests the loudest peak sit between -6 and -3 dBTP and says no dither is needed when you export at the session bit depth.
- Splice notes engineers differ: some want -6 dB, some -10 dB, some only that the mix does not clip.
- Youlean Loudness Meter has a free tier that never expires and shows LUFS and true peak.
Your mix is ready for a human mastering engineer when you have stopped changing balances, it plays back cleanly with no limiter on the master bus, and you can export it as a lossless 24-bit file at the session's own sample rate with peaks a few dB below 0 dBFS. Everything else on this page is about checking those three things properly, and about the extras (notes, references, silence at the ends) that save a revision.
What is free here: all of it. You don't need to pay for anything to check a mix before mastering. Your DAW's export settings cover format, sample rate and bit depth, and the Youlean Loudness Meter has a free tier that "never expires" and reads integrated LUFS and true peak, which is the one number that matters most below. The Pro version is a one-off $39 plus tax, but you don't need it for this.
What the studios actually ask for
We read the published delivery pages of two mastering studios and one manufacturing service, plus two widely shared guides from a mastering service and a sample platform. They agree more than forum arguments suggest.
| Spec | Abbey Road | Chicago Mastering Service | Disc Makers | Sage Audio | Splice (Max Rewak) |
|---|---|---|---|---|---|
| File type | WAV or AIFF, uncompressed stereo | 24-bit WAV or BWF preferred; AIFF and others accepted | WAV or AIFF; no MP3, AAC or WMA | Same as session | Lossless (WAV, FLAC, AIFF); no MP3 or M4A |
| Bit depth | At least 16, ideally 24 | 24 or 32; 16 only if 24 is impossible | 24-bit | Same as the recording | Source bit depth |
| Sample rate | 44.1 to 96 kHz | Native rate; do not convert | 44.1 kHz or higher | Same as the recording | Highest rate used in the project |
| Peak headroom | -6 to -3 dB "is a good guide" | At least 2 dB | 3 to 4 dB | Loudest peak -6 to -3 dBTP | Varies: some want -6, some -10, some just no clipping |
| Master-bus processing | No limiting or normalising | Avoid heavy limiting and bus clipping | No compression, limiting or maximising on the stereo bus | No limiter; any bus compression or EQ under about 3 dB | Remove limiters used for loudness |
Sources: Abbey Road, Chicago Mastering Service, Disc Makers, Sage Audio, Splice (May 2024), all read 29 October 2026.
What we take from it. The headroom number is the thing people fight about, and it is the least important line in the table. Every source wants the same outcome: no clipping and no limiter. Whether your peaks land at -3 or -6 matters far less than whether the mix was squashed on the way there. Our default is to aim for peaks around -6 to -3 dBTP, because that sits inside the Abbey Road and Sage ranges and clears Chicago's 2 dB minimum, then to follow your engineer's own sheet if it says otherwise. If you want to know why headroom exists at all, see what headroom is.
The checklist
Work through it in order. The first group decides whether you are ready; the second is the delivery itself.
Is the mix finished?
- You have stopped changing balances. If you would still move the vocal up a dB, mastering can't do that for you without moving everything with it. Sage Audio makes the related point that a mix which doesn't sound "finished" yet is normal: loudness and final polish are the mastering engineer's job.
- You mixed without a limiter on the master, or you have taken it off and re-checked. Sage warns that mixing into a limiter changes how your earlier processing sounds, so balances made through one can fall apart when it comes off. Take it off, listen through once, fix anything that jumps out. Our bedroom mix mistakes guide has quick listening tests for balance and low end.
- Any bus processing is gentle. Sage lists as excessive: compression taking off more than 3 dB, EQ moves above 3 dB, distortion over 1% THD, and stereo-widening plug-ins. Light glue is fine; a "mastering chain" on your mix bus is not.
- Nothing clips. Play the loudest section with a true-peak meter on the master (Youlean's free tier will do). Splice's rule is simple: if it clips, turn it down before export. Turning a clipped file down afterwards doesn't remove the clipping.
Is the file right?
- Peaks a few dB below full scale. Use the table: around -6 to -3 dBTP covers most studios. Pull the master fader or every channel down equally to get there; don't normalise the export.
- Lossless format. WAV or AIFF (FLAC if your engineer takes it). Never MP3 or M4A. Splice adds a trap worth knowing: dragging audio into macOS Messages converts it to M4A, so send a download link instead.
- 24-bit (or 32-bit float), at the session sample rate. Chicago Mastering Service is blunt: "Do not sample rate convert." If your project is 48 kHz, send 48 kHz. Our sample rate and bit depth explainer covers what these numbers mean.
- No dither on your export. Sage and Splice both say you don't need to dither when you export at the session bit depth; the engineer handles it at the final step. More in dithering explained.
- Silence and fades left intact. Chicago asks for 2 to 3 seconds of silence or room tone before and after each mix, and says not to cut fades short; mastering trims them.
Will the engineer understand what you want?
- Notes and references. Chicago asks for reference recordings and specific notes (known problems, track spacing). Keep it short: one or two reference tracks and why you chose each, plus anything you already know is wrong.
- Correct titles and codes. Chicago asks for exact song titles, album title, and ISRC and UPC codes if you have them. Getting spelling right now saves a re-export later.
- One file per version, clearly named. Abbey Road bills each version or mix separately, so decide which mix you are sending before you upload a folder of five.
The question nobody's spec answers
None of these pages tells you whether your mix is good. That is a judgment call, and the honest test is boring: leave it for a day, play it once on something you didn't mix on (phone, car, earbuds), and write down only what bothers you. If the list is empty or only says "it's not loud enough", you are done, because loudness is what you are paying the mastering engineer for. If it says "the vocal disappears in the chorus", you are not.
Planning to master it yourself instead? The same file is the right starting point; go to our home mastering basics and the step-by-step streaming master recipe. Sending stems rather than a stereo mix? See stem mastering explained.
Sources
- What format should I send my track in?, Abbey Road Studios (primary source). Accessed 29 Oct 2026.
- Preparation, Chicago Mastering Service (primary source). Accessed 29 Oct 2026.
- What to keep in mind during your mixdown, Disc Makers (primary source). Accessed 29 Oct 2026.
- How to Prepare Your Mix for Mastering, Sage Audio (primary source). Accessed 29 Oct 2026.
- How to prepare your mix for mastering: 5 essential tips, Splice. Accessed 29 Oct 2026.
- Youlean Loudness Meter, Youlean (primary source). Accessed 29 Oct 2026.
Researched with AI assistance, written and checked by WATMM Desk.