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  #1  
Old 2013-02-28, 07:42
aisling aisling is offline
 
Join Date: Nov 2001
Posts: 220
Could somebody school me on the physics of acoustics?

I ran a session stereo via unbalanced cables from the audio out of my Mackbook pro via 1/8 inch stereo plug/1/4 inch L&R adapter, and finally into a PA via 2 tip/ring 1/4 cables. My drums, bass, and anything panned dead center was like 20db quieter than originally....It ruined a lot of the vibe of the session.

Can anybody sum up as to why and what is happening that causes the drastic signal attenuation?
Thanks
  #2  
Old 2013-02-28, 10:47
normen's Avatar
normen normen is online now
 
Join Date: Sep 2006
Posts: 3,516
Sounds like you have the phase of a speaker or some other part of the system inverted on one channel, causing the sound to cancel itself out.
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  #3  
Old 2013-03-01, 20:13
aisling aisling is offline
 
Join Date: Nov 2001
Posts: 220
I agree it is a phasing issue, but I was wondering if the unbalanced out cables had any contribution to the attenuation?

Bump?
  #4  
Old 2013-03-01, 22:32
normen's Avatar
normen normen is online now
 
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Quote:
Originally Posted by triphop55 View Post
I agree it is a phasing issue, but I was wondering if the unbalanced out cables had any contribution to the attenuation?

Bump?
If you don't connect the "-" signal instead of ground then yes, that might happen.
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Plugin latency issues? Phasing on parallel channels? Want to know the real latency of your audio interface? Try the VMG-01!
Professional Audio Engineer at Theater Bremen, Germany • Part Time Programmer
  #5  
Old 2013-03-02, 01:09
aisling aisling is offline
 
Join Date: Nov 2001
Posts: 220
Thanks. It was a spontaneous thing, I did not have an audio interface on me. I'll retry the same PA with XLR cables coming from my 828. The PA owner swears his rig is wired correctly....
  #6  
Old 2013-03-02, 03:12
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PureSynthesis PureSynthesis is offline
 
Join Date: Apr 2012
Posts: 10
this isnt really an acoustics question... I dont think.
If the problem is that you are getting a 'weird sound' on all of your recording playback I would reccomend moving monitors away from corners and reading up about standing waves via wiki ...but the way I'm reading this its the fact that you have a problem with the mix.

Was the original session done in the same location? what was the playback location? - if the playback location was a large room/hall then standing waves might still apply.
...if not it might be down to the initial mix where phase problems might be cancelling out that kick/

Listen to the thing in mono and tell us if any thing seems to drop out of the mix,
If the the problem was down to playback in a large hall type location then it will be down to one of the following:
* Standing wave issues with the room
* Poor playback system (or wrong kind of PA - as in vocal pa system)
* Cabling issues.

I suspect however the problem is due to stereo images being panned to center which has inherrant problems with regards to phase... I would suggest checking this by both trying a mono-summed mix (not just the left channel) and then try replicating the mix but this time try flipping phases (or monoing) problem areas.

Peace,
L
 

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