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Topic: stereo won't convert to mono (Read 3842 times) previous topic - next topic
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stereo won't convert to mono

i recorded a cassette tape to computer using line-in. it was recorded as stereo. the stereo file plays fine. when i convert the file to mono the volume goes away.

the stereo file looks fine in cool edit, but the mono looks muted. i can increase to volume on the new mono file but the sound is completely distorted.


here is sample mp3 (10 seconds) i uploaded. try converting to mono and see for yourself:

http://rapidshare.de/files/38256547/sample_stereo.mp3.html


anyone know what the problem is? shouldn't converting to mono just merge the two channels into one and sound the same?

stereo won't convert to mono

Reply #1 –
Your file has a very little stereo separation and the signals are in antiphase.
Something is wrong with your recording setup.

If helps if you invert one of the channels before converting to mono, but I suggest you to find the cause of this.

Here is the stereogram of your file:
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stereo won't convert to mono

Reply #2 –
Quote from: her34 on
when i convert the file to mono the volume goes away.
The two channels are out of phase, so they result in (almost) silence when summed to mono. It should be easy to flip phase of either the Left or Right channel in an audio editing application.
If you can, it's best to find out where the phase was inverted in your analog chain and correct it.
Since the L and R channel in your sample are almost identical, you might even be better off by just using one of the channels instead of summing them to mono (which can give some phase problems).

stereo won't convert to mono

Reply #3 –
thanks for feedback

how can i determine if the phase problem is already on the tape (happened during original recording) or is happening now (happens during playback)?

current setup is: old cassette player headphone out--> 3.5mm cable --> computer line-in. cool edit for recording

stereo won't convert to mono

Reply #4 –
  Very strange!  I'm trying to figure-out how this could happen accidently...  I'm pretty sure the problem is with the original recording. 

I think this has to be caused by a speaker or microphone problem.    I suppose it could happen if the original recording was made with a pair of closely-positioned microphones, and one of the microphones was wired with "opposite phase".  (With a pair of good quality,  identical,  microphones, this shouldn't happen.)  Or, the microphones could have been located close to the speakers, and the speakers were wired out-of-phase.

In that case, the correction would also be to invert one of the channels, even if you want to leave it as stereo.  On my computer's "2.1" speaker system, it sounds much better with one channel inverted.  With the non-inverted file, the combined-channel woofer-sound is getting canceled before being sent to the woofer.

It's not unusual for the phase to get inverted somewhere in the electronics.  But with stereo electronics, both channels would get inverted identically, and you wouldn't have a problem.  On the other hand, its fairly easy to get a pair of microphones or speakers wired differently from each other.

P.S.
Some mixers also have a phase-reversal switch for each input, so there's another potential problem area during original recording.