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[Vladimir Katilevskiy <truaddict@xxxxxxxxx>]

It seems I found the answer to my question/bugreport.
My macbook pro 8.1 13-inch really has 3 speakers: left, right and so called (by Apple) "subwoofer" - standalone additional speaker, which is located on the right side (this is important!). It is a really new thing for me (after 2 years of using laptop).
So alsamixer (and intel-hda driver) is absolutely correct naming one of the controls as "Bass speaker".
Other items in alsamixer are: Master, Speaker, Headphone and PCM.
Now the important thing: if I set to 0 right channel of Speaker in alsamixer, the left sounds like it was in Mac OS in the same mode (balance shifted to left speaker) - that is the right way how the balance should work!
But balance slider in Ubuntu sound panel (let's call it slider U) works very strange: at first, when i start to move it to the left - alsamixer's Speaker right channel (slider A) goes down as it should be. But when slider U is approx. 5% till the end, slider A is already 0! At this point the sound is ok (coming from left speaker, but with bass as it should be).
And if I continue to move slider U till the end, I see right PCM going down dramatically fast in alsamixer. And now the sound is incorrect (as stated in my bugreport).

So I can say that when in normal mode (balance set to 50/50) the sound is ok and identical to Mac OS.
The questions are:
1) Why does ubuntu's sound panel (and pavucontrol too) treat subwoofer speaker as the right one?
2) Why does ubuntu's sound panel balance slider behave in such strange way (described above)?
2) Why is the subwoofer speaker included in right channel of PCM control (in alsamixer)?

Overall, I am happy to solve this puzzle (the answer looks so simple if to look back). Please tell me, should I post a new report(s) or leave it as is?
And sorry for my Russian English :)

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https://bugs.launchpad.net/bugs/1234252

Title:
  [MacBookPro8,1, CS4206] Left speaker low volume  and absence of low
  freqs

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu 13.04 fresh install or fully updated - no difference.
  While listening music through internal speakers I noticed that left speaker sounds differently from the right one. I would describe left speaker's sound as those from the headphones lying on the table: low volume level and mostly high frequences are heard.
  1) Trying to check mixer levels in alsamixer, muting/unmuting, balance channels etc didnt help.
  2) In alsamixer there is a mixer item called "Bass Speaker". If I mute it, other playback items (including Master) are muted too. If I make its level to 0, then sound from both speakers become identical: low volume and without bass frequences. Level of the Bass Speaker resets if I adjust volume level from Unity volume control tool.
  3) Trying to set model parameter for intel_hda module to "mbp55" or "imac27" didnt help.
  4) Sound from headphones is perfectly ok.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: alsa-base 1.0.25+dfsg-0ubuntu4
  ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
  Uname: Linux 3.8.0-19-generic x86_64
  NonfreeKernelModules: wl
  ApportVersion: 2.9.2-0ubuntu8
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  vkat       1970 F.... pulseaudio
   /dev/snd/pcmC0D0c:   vkat       1970 F...m pulseaudio
  Date: Wed Oct  2 19:12:40 2013
  InstallationDate: Installed on 2013-10-02 (0 days ago)
  InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
  MarkForUpload: True
  PackageArchitecture: all
  SourcePackage: alsa-driver
  Symptom: audio
  Symptom_AlsaPlaybackTest: ALSA playback test through plughw:PCH failed
  Symptom_Card: Built-in Audio - HDA Intel PCH
  Symptom_Jack: Speaker, Internal
  Symptom_Type: High background noise, or volume is too low
  Title: [MacBookPro8,1, Cirrus Logic CS4206, Speaker, Internal] Background noise or low volume
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 01/24/12
  dmi.bios.vendor: Apple Inc.
  dmi.bios.version: MBP81.88Z.0047.B27.1201241646
  dmi.board.asset.tag: Base Board Asset Tag#
  dmi.board.name: Mac-94245B3640C91C81
  dmi.board.vendor: Apple Inc.
  dmi.board.version: MacBookPro8,1
  dmi.chassis.type: 10
  dmi.chassis.vendor: Apple Inc.
  dmi.chassis.version: Mac-94245B3640C91C81
  dmi.modalias: dmi:bvnAppleInc.:bvrMBP81.88Z.0047.B27.1201241646:bd01/24/12:svnAppleInc.:pnMacBookPro8,1:pvr1.0:rvnAppleInc.:rnMac-94245B3640C91C81:rvrMacBookPro8,1:cvnAppleInc.:ct10:cvrMac-94245B3640C91C81:
  dmi.product.name: MacBookPro8,1
  dmi.product.version: 1.0
  dmi.sys.vendor: Apple Inc.

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