A Audio and hi-fi forum. AudioBanter

Go Back   Home » AudioBanter forum » rec.audio » Pro Audio
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Why don't these signals null?



 
 
Thread Tools Display Modes
  #1  
Old October 17th 19, 06:51 AM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

Let's say I record a DI guitar part into a looper, then re-amp that looped part and record the output twice to separate tracks in a DAW, time-align them and invert the phase on one. I know the tracks won't null, but I don't fully understand the why.
Ads
  #2  
Old October 17th 19, 08:11 AM posted to rec.audio.pro
John Williamson
external usenet poster
 
Posts: 1,659
Default Why don't these signals null?

On 17/10/2019 06:51, James Price wrote:
> Let's say I record a DI guitar part into a looper, then re-amp that looped part and record the output twice to separate tracks in a DAW, time-align them and invert the phase on one. I know the tracks won't null, but I don't fully understand the why.
>

When you re-amp the part, that changes the waveform in both shape and
amplitude, so it will not null out. To null completely, the waveforms
and the amplitudes of the two tracks have to be identical.

--
Tciao for Now!

John.
  #3  
Old October 17th 19, 07:01 PM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Thursday, October 17, 2019 at 2:12:02 AM UTC-5, John Williamson wrote:
> When you re-amp the part, that changes the waveform in both shape and
> amplitude, so it will not null out. To null completely, the waveforms
> and the amplitudes of the two tracks have to be identical.


I'm talking about re-amping the part using a looper in order to
eliminate any inconsistencies that would normally occur when playing the
part twice.
  #4  
Old October 17th 19, 07:21 PM posted to rec.audio.pro
John Williamson
external usenet poster
 
Posts: 1,659
Default Why don't these signals null?

On 17/10/2019 19:01, James Price wrote:
> I'm talking about re-amping the part using a looper in order to
> eliminate any inconsistencies that would normally occur when playing the
> part twice.
>

Are you recording the part, saving that as one track in the mix, then
re-amping that recording using a plugin and saving that as another track?

If so, then the re-amped version will not be identical to the original
recording due to the changes made by the plug in. There will be changes
in the frequency response as a minimum. What you will hear when you
invert the phase of one of the tracks is the difference added by the
re-amp plugin.

Or are you just copying the original recording to another track in the
mix? In which case they should null exactly unless the settings on the
two tracks differ.

--
Tciao for Now!

John.
  #5  
Old October 17th 19, 08:55 PM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Thursday, October 17, 2019 at 1:21:07 PM UTC-5, John Williamson wrote:
> On 17/10/2019 19:01, James Price wrote:
> > I'm talking about re-amping the part using a looper in order to
> > eliminate any inconsistencies that would normally occur when playing the
> > part twice.
> >

> Are you recording the part, saving that as one track in the mix, then
> re-amping that recording using a plugin and saving that as another track?


I've done that, and also recorded a DI to a track in a DAW using a DI box
and routed the output from the interface to a miked cab, which is recorded
twice (separate passes) to two tracks into the DAW.
  #6  
Old October 17th 19, 11:00 PM posted to rec.audio.pro
Phil Allison[_4_]
external usenet poster
 
Posts: 451
Default Why don't these signals null?

John Williamson wrote:

-----------------------
>
> Or are you just copying the original recording to another track in the
> mix? In which case they should null exactly unless the settings on the
> two tracks differ.
>


** IMO you are wasting your time - the OP is an idiot.

Reminds me of an event years ago when a local small studio operator had a problem with his Yamaha REV 7 digital reverb.

On the phone he claimed it had stopped working in stereo - he could no longer pan pot sounds coming out in in a stereo mix.

Being an unfamiliar model to me, I agreed to take a quick look at it and soon realised the despite having L & R inputs and outputs, it was not a genuine stereo unit but rather it simulated stereo from a mono path at the output.

His claim that it used to work in true stereo was bogus, but nothing I said would convince him otherwise. He eventually picked up the unit and left in a huff to find a better tech.

His business card said "Enterprise Studios" with a pen drawing of the famous space ship.

So I dubbed the guy "Captain Jerk".


..... Phil




















  #7  
Old October 17th 19, 11:52 PM posted to rec.audio.pro
geoff
external usenet poster
 
Posts: 1,543
Default Why don't these signals null?

On 18/10/2019 8:55 am, James Price wrote:
> On Thursday, October 17, 2019 at 1:21:07 PM UTC-5, John Williamson wrote:
>> On 17/10/2019 19:01, James Price wrote:
>>> I'm talking about re-amping the part using a looper in order to
>>> eliminate any inconsistencies that would normally occur when playing the
>>> part twice.
>>>

>> Are you recording the part, saving that as one track in the mix, then
>> re-amping that recording using a plugin and saving that as another track?

>
> I've done that, and also recorded a DI to a track in a DAW using a DI box
> and routed the output from the interface to a miked cab, which is recorded
> twice (separate passes) to two tracks into the DAW.
>


.... and you're wondering why they don't completely null ?!!!

geoff
  #8  
Old October 18th 19, 12:53 AM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Thursday, October 17, 2019 at 5:52:58 PM UTC-5, geoff wrote:
> ... and you're wondering why they don't completely null ?!!!



The caveat is that they will null completely with clean tones.
  #9  
Old October 18th 19, 04:47 PM posted to rec.audio.pro
Tobiah
external usenet poster
 
Posts: 615
Default Why don't these signals null?

On 10/16/19 10:51 PM, James Price wrote:
> Let's say I record a DI guitar part into a looper, then re-amp that
> looped part and record the output twice to separate tracks in a DAW,
> time-align them and invert the phase on one. I know the tracks won't
> null, but I don't fully understand the why.
>


When you run the signal through an amp, through the air, into a microphone
you open yourself up to some variables that may change between passes. Were
you in the room during the recordings? Did you move at all, or breath with
a different pattern the second time? Was the ambient noise exactly the same
both times? The acoustic space that you sent the signals through will never
be the same during both passes. Even if you recorded the straight and inverted
tracks at the same time, you'd use two different mics that would collect altogether
different signals because of their mismatch, and necessarily different positions.

Also, you say you time aligned the two tracks, but did you get that sample perfect?
what about clock drift that may have been different between takes?

What was the result anyway, if not null? Was it pretty quiet anyway?


  #10  
Old October 18th 19, 05:24 PM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Friday, October 18, 2019 at 10:47:52 AM UTC-5, Tobiah wrote:
> On 10/16/19 10:51 PM, James Price wrote:
> > Let's say I record a DI guitar part into a looper, then re-amp that
> > looped part and record the output twice to separate tracks in a DAW,
> > time-align them and invert the phase on one. I know the tracks won't
> > null, but I don't fully understand the why.
> >

>
> When you run the signal through an amp, through the air, into a microphone
> you open yourself up to some variables that may change between passes. Were
> you in the room during the recordings? Did you move at all, or breath with
> a different pattern the second time? Was the ambient noise exactly the same
> both times? The acoustic space that you sent the signals through will never
> be the same during both passes. Even if you recorded the straight and inverted
> tracks at the same time, you'd use two different mics that would collect altogether
> different signals because of their mismatch, and necessarily different positions.


These were short (approx. 10 seconds), close-miked recordings, recorded
in two passes, back-to-back using the same mic, through the same cab and fed
a DI guitar via a sampled loop. The recordings were time-aligned perfectly at
the sample level.


> What was the result anyway, if not null? Was it pretty quiet anyway?


The residual noise fluctuated somewhere between -30 to -50 dB.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Ethan Winer's Null Tester Les Cargill[_4_] Pro Audio 33 November 14th 18 02:47 PM
Null speaker test [email protected] High End Audio 14 October 28th 05 02:41 AM
Null speaker test [email protected] Pro Audio 13 October 18th 05 06:17 PM
Null speaker test [email protected] Tech 16 October 15th 05 05:58 AM
Null speaker test [email protected] Audio Opinions 21 October 13th 05 02:08 AM


All times are GMT +1. The time now is 06:18 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 AudioBanter.
The comments are property of their posters.