I know this is The End Of CDs, but here’s a quick rundown on how to rip a CD in OS X, mix the stereo down to mono, then burn it back to a blank CD.

The speakers in my MR2 are so bad, I think it’ll help to run a mono mix through them (spoiler: it did help). Right now, they’re kind of hard to hear. Not that I want anything to drown out the engine1, I need that to drive.

Mono used to be all there was.

Ripping

Just use iTunes. Customize your Import Settings before you import: just use AIFF and defaults. Hard drives are so big these days, I think we can look at MP3 as the cassette of the era. WAV/AIFF are unbeatable, IMO.

I like to let/have iTunes “manage” the iTunes Library folder structure, so it’ll move a copy into my iTunes Library.

Downmixing to mono

You’ll need sox, available through Homebrew:

  $  brew install sox

You’ll need a folder to put the mono files in (I do not want them in iTunes, I just want to burn them2). That folder will be set as cddir. The folder containing the music I want to downmix/burn is set as itunesdir. You’ll want to be running bash to run this.

  $  itunesdir=/Volumes/R1500G/iTunes Library/Music/ARTIST/ALBUM/
  $  cddir=/Volumes/R1500G/Stuff/../ALBUM
  $  mkdir -p "$cddir"
  $  cd "$itunesdir"
  $  for f in *.aif ; do sox "$f" "$cddir"/"$f" remix - ; done

Something like that. I wouldn’t put a trailing slash on the $cddir, but I’m not sure it matters.

Some people say remix 1-2 or remix 1,2 but don’t say what the difference is. The man sox says if you just put a - it’ll basically fill in the left side with 1 and the right with N (N channels), so it’ll come out to 1-2, supposedly.

I did find that generating 3 mono files with -, 1-2, and 1,2 had exactly the same size, sounded alike (to me, at least), but had different shasums. Is there some nondeterministic random seed thing inside the AIFF format?3

They all sound the same (hopefully), so I go with -.

Burning to CD

You don’t need iTunes! How nice.

  $  drutil burn -audio "$cddir"

It logs a bunch of stuff. There’s probably a --verbose or something. Don’t worry about it! You’ll figure it out when &/ if there’s a problem.

Bottom line

It sounds really good in the MR2 now. You’ve got to understand, I don’t sit in the center of my car. The MR2 is so small, it’s got 2 speakers in each door and that’s it. There is not a single speaker in the dash, in the back, there’s no backseat.. no subwoofers in the back like a Nissan 350/370Z.

So you’re maybe a couple feet from the speakers in the driver’s door, and at least 4 feet from the passenger door. I just can’t imagine there’s a strong “stereo image” being so lopsided.

And besides, I’m listening to stuff like Jimi Hendrix! I want to listen to the guitar. Guitar is a mono signal into a mono amplifier4 into 1 maybe 2 maybe 4 speakers into 1 microphone. I’m not quite on the Mono Forever train (yet!), but I do think we don’t hear enough mono.

I’m not going to ABX it 30 times tomorrow; I’ll listen to the mono and see how it compares to the sound I know in my head (which has usually been stereo).

Updates / Errata

First, I made a mistake when I wrote

  $  drutil burn -audio $cddir

because you should pretty much always double-quote your bash vars. Write "$cddir", not $cddir.

Second, one time I got clipping when I combined the channels. The error looks like

sox WARN dither: dither clipped 21 samples; decrease volume?
sox WARN dither: dither clipped 3 samples; decrease volume?

What you want to do is slowly decrease the volume until it fits, run sox as sox -v 0.99 or sox -v 0.98, et cetera, until you find a volume that does not clip. Not an ideal solution, I know; best I got.

If that does happen, I would clean out the output directory, then start again:

  $  rm -i "$cddir"/*
  $  for f in *.aif ; do sox -v 0.99 "$f" "$cddir"/"$f" remix - ; done
  1. only thing more embarassing than stalling is not realizing you’ve stalled, or “putting down” power out-of-gear 

  2. I hate having to import it, find it, create a playlist, .. no thanks 

  3. I kid you not, I’m pretty sure PDF is like that; comparing PDFs is shall-we-say non-trivial 

  4. ok, some guys use 2 amps, but you’re probably not John Frusciante