[LAU] Pro Audio? OT rant.

Tim E. Real termtech at rogers.com
Mon Dec 31 22:44:30 UTC 2012

On December 31, 2012 03:39:45 PM Charles Henry wrote:

On Mon, Dec 31, 2012 at 3:17 PM, Neil <djdualcore at gmail.com> wrote:

> On Mon, Dec 31, 2012 at 2:57 PM, Charles Henry <czhenry at gmail.com> wrote:
> > At the ends of the frequency range, the group delay becomes significant and
> > shifts some components of the signal more than others.
> So, the wider the band, the less likely you are to hear the shifted
> parts of the signal?
> Yes, in general.  
> In the case we're describing, the top end of the passband is outside the 
range of hearing.  The phase shifts might still be audible at the low end of 
the transducer's range.
> However, phase shifts aren't much of a problem by themselves--they're all 
over the place in any typical multi-driver system and placement in the room 
matters just as much.  The loudspeaker crossover introduces the same effect.
> Subwoofers are much more prone to phase shift problems.  You notice it a lot 
when the bass seems to lag behind the beat--and this results from not having a 
continuous frequency response that goes down to 0 Hz (the ideal case) or bad 
resonance characteristics.
> Really clean sounds have a lot to do with the tightness of the temporal 
response--but there are of course tradeoffs in any kind of design choice like 
> Chuck

Gabba gabba hey!
Caught you off guard, eh? 		My my what a long thread...
Happy new year y'all.

Just an offside comment and question:

I've repaired a lot of subwoofers.
After repair we had to let them run by themselves with audio.

I noticed a very strange phenomenon with all of them.

When you listen to a subwoofer all by itself, the music which
 comes out of it seems to be noticeably off-key, until you
 turn up the rest of the audio system.

For example, take oh, say the bass guitar in Ozzy's "Crazy Train".
The bass would sound like it's playing in say G rather than F#.
Then I would turn up the rest of the system, and all of a sudden 
 everything sounded correct.

At first I thought it was my proximity to the sub, or some kind
 of atmospheric effect similar to helium and the human voice.
But it's weird that the effect instantly disappears when you 
 turn up the rest of the system.

Has anyone else ever noticed this?

Of the MusE project.

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