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-   -   Could somebody school me on the physics of acoustics? (https://www.propellerheads.se/forum/showthread.php?t=176960)

aisling 2013-02-28 07:42

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

normen 2013-02-28 10:47

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.

aisling 2013-03-01 20:13

I agree it is a phasing issue, but I was wondering if the unbalanced out cables had any contribution to the attenuation?

Bump?

normen 2013-03-01 22:32

Quote:

Originally Posted by triphop55 (Post 1247479)
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.

aisling 2013-03-02 01:09

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....

PureSynthesis 2013-03-02 03:12

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

PureSynthesis 2013-03-02 03:16

sry ...I never seen any previous replies when responding :/


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