How to Spot a Fake WAV or Upscaled MP3 in Your DJ Library
A fake lossless file plays fine on earbuds but falls apart on a club rig. Here's a quick way to check your DJ library with free tools.
Why fake files end up in a DJ library
A "fake WAV" is a lossy file, usually an MP3, that got converted into WAV or FLAC without ever gaining back the data a lossy encoder threw away. The file extension and the bitrate tag say lossless. The actual audio is still MP3 underneath. The same thing happens with MP3s sold or shared as 320kbps that were really encoded at 128kbps or 192kbps and then relabelled.
These files are easy to miss. On phone speakers or cheap earbuds they sound close enough to the real thing. The problem shows up later, on a proper club system, where the missing top end turns into splashy cymbals, a flattened reverb tail, and a mix that feels thinner than everything around it.
The simple test: look at the frequency cutoff
Every lossy encoder removes frequencies above a certain point to save space. That cutoff shows up as a hard edge, almost a straight wall, when you look at a track's spectrogram. A genuine lossless file has no such wall: the energy tapers off naturally and keeps going close to 20-22kHz.
As a rough guide, based on how encoders behave: a real 320kbps MP3 cuts off close to 19-20kHz, a 256kbps source closer to 19kHz, 192kbps around 18.5kHz, and 128kbps around 16kHz. If a file is tagged as WAV or FLAC but its spectrogram shows a clean wall at one of these points, it was transcoded from a lossy source at some point, whatever the tag says.
Free tools that show this
- Spek — a small, free app built specifically to show a track's spectrogram. Drop a file in and the cutoff is visible immediately.
- Audacity — open a track and switch the track view to Spectrogram to see the same thing without installing anything extra.
A gradual fade at the top, rather than a sharp wall, usually just means an old master, a vinyl rip, or a deliberately dark mix. That's not a fake, just a quiet top end.
What to do once you find one
Don't rely on the file extension or the bitrate shown in your DJ software's library view. Both just repeat whatever tag is stored in the file, which is exactly what a fake gets wrong. If a track fails the spectrogram check, the fix is usually to re-source it: buy or re-download it from a store you trust, rather than re-encoding the bad copy into a bigger file. Re-encoding a lossy file into a bigger format never recovers the missing frequencies, it just makes the fake take up more space.
It's worth running this check on anything that came from a free download site, a random USB handed to you at a gig, or an old backup you're not sure about. One pass through a new batch of tracks before you add them to your main collection saves you from finding out the hard way, on a big rig, that a track doesn't hold up.
Check your files with Rimeo
The Rimeo app on your computer runs the same spectrogram test, so you don't need a separate tool for it. Rimeo also keeps honest what happens to a file once you've confirmed it's good: when you download a track for offline play, Rimeo sends the original file straight off your computer's drive, not the lighter version it uses to keep a live stream smooth. Whatever you checked on your computer is what lands on your phone.
Check a track before it reaches a club system.
Open Check quality in the Rimeo app on your computer, drop in a file, and a fake WAV shows its cutoff on the chart. Pulse also lists the tracks in your DJ library with no key, BPM or genre, so the rest of the cleanup is in one place.