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
  #11  
Old October 18th 19, 09:04 PM posted to rec.audio.pro
John Williamson
external usenet poster
 
Posts: 1,658
Default Why don't these signals null?

On 18/10/2019 17:24, James Price wrote:

> 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.


No two recordings of any instrument (Whether digital or analogue) played
by a human will ever null completely. Apart from environmental factors
such as the air temperature, the player's will differ timing between the
two recordings.

Getting them as close as you did is actually damn consistent playing.


--
Tciao for Now!

John.
Ads
  #12  
Old October 18th 19, 11:54 PM posted to rec.audio.pro
Tobiah
external usenet poster
 
Posts: 615
Default Why don't these signals null?

On 10/18/2019 1:04 PM, John Williamson wrote:
> On 18/10/2019 17:24, James Price wrote:
>
>> 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.

>
> No two recordings of any instrument (Whether digital or analogue) played
> by a human will ever null completely. Apart from environmental factors
> such as the air temperature, the player's will differ timing between the
> two recordings.
>
> Getting them as close as you did is actually damn consistent playing.
>
>

His original post was difficult to understand, but if you look at it
again, he performs once, then copies the track through the air twice.
The result he got is to be expected. The inverted track mostly nulled
the other, but the differences caused by amp distortion and air medium
inconsistencies and even his position in the room, lingered in the
difference.



  #13  
Old October 19th 19, 02:22 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 3:04:40 PM UTC-5, John Williamson wrote:
> On 18/10/2019 17:24, James Price wrote:
>
> > 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.

>
> No two recordings of any instrument (Whether digital or analogue) played
> by a human will ever null completely. Apart from environmental factors
> such as the air temperature, the player's will differ timing between the
> two recordings.
>
> Getting them as close as you did is actually damn consistent playing.


The recordings weren't played by a human twice. A 10 sec. *recording* of a
guitar DI was played into an amp/cab twice, consecutively, one after the
other, the output of which was recorded and cut up into separate tracks.
Both tracks were time-aligned and the phase inverted on one.
  #14  
Old October 19th 19, 02:54 PM posted to rec.audio.pro
Ralph Barone[_3_]
external usenet poster
 
Posts: 40
Default Why don't these signals null?

James Price > wrote:
> On Friday, October 18, 2019 at 3:04:40 PM UTC-5, John Williamson wrote:
>> On 18/10/2019 17:24, James Price wrote:
>>
>>> 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.

>>
>> No two recordings of any instrument (Whether digital or analogue) played
>> by a human will ever null completely. Apart from environmental factors
>> such as the air temperature, the player's will differ timing between the
>> two recordings.
>>
>> Getting them as close as you did is actually damn consistent playing.

>
> The recordings weren't played by a human twice. A 10 sec. *recording* of a
> guitar DI was played into an amp/cab twice, consecutively, one after the
> other, the output of which was recorded and cut up into separate tracks.
> Both tracks were time-aligned and the phase inverted on one.
>


And what happens if due to the vagaries of when you hit the “Play” button,
the second recording is a half sample out of sync with the first?

  #15  
Old October 19th 19, 03:17 PM posted to rec.audio.pro
John Williamson
external usenet poster
 
Posts: 1,658
Default Why don't these signals null?

On 19/10/2019 14:22, James Price wrote:

> The recordings weren't played by a human twice. A 10 sec. *recording* of a
> guitar DI was played into an amp/cab twice, consecutively, one after the
> other, the output of which was recorded and cut up into separate tracks.
> Both tracks were time-aligned and the phase inverted on one.
>

It takes a fraction of a millimetre movement or a tiny difference in
atmospheric pressure or temperature to change the time delay between the
speaker and the microphone enough to give the symptoms you describe.

Even a difference in the background noise in the room will do it.

Have you tried normalising the difference signal to hear what it is?

--
Tciao for Now!

John.
  #16  
Old October 20th 19, 06:31 PM posted to rec.audio.pro
Scott Dorsey
external usenet poster
 
Posts: 16,649
Default Why don't these signals null?

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.


They don't sound the same, so why would you expect them to null?

The whole reason you run the signal through a cabinet is to change the
waveform. So don't be surprised when it does just that.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #17  
Old October 20th 19, 11:13 PM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Sunday, October 20, 2019 at 12:31:59 PM UTC-5, Scott Dorsey wrote:
> 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.

>
> They don't sound the same, so why would you expect them to null?
>
> The whole reason you run the signal through a cabinet is to change the
> waveform. So don't be surprised when it does just that.


I'm curious why the signals don't null when changes imparted by the cabinet
are controlled for, though? For example, sending a looped guitar DI to
an amp and then running that through an impulse response of a guitar cabinet.
Again, the caveat is that clean tones *will* null, thus I'm referring to
distorted and overdriven tones.
  #18  
Old October 23rd 19, 06:35 AM posted to rec.audio.pro
PStamler
external usenet poster
 
Posts: 881
Default Why don't these signals null?

On Sunday, October 20, 2019 at 5:13:37 PM UTC-5, James Price wrote:
> On Sunday, October 20, 2019 at 12:31:59 PM UTC-5, Scott Dorsey wrote:
> > 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.

> >
> > They don't sound the same, so why would you expect them to null?
> >
> > The whole reason you run the signal through a cabinet is to change the
> > waveform. So don't be surprised when it does just that.

>
> I'm curious why the signals don't null when changes imparted by the cabinet
> are controlled for, though? For example, sending a looped guitar DI to
> an amp and then running that through an impulse response of a guitar cabinet.
> Again, the caveat is that clean tones *will* null, thus I'm referring to
> distorted and overdriven tones.


If I understand what you're describing, you're trying to null a signal that's been run through a guitar cabinet with one that's been run through a *simulation* of a guitar cabinet. Two possible explanations occur to me right off; the first is that simulations aren't perfect. The second is that though the impulse response you're trying to null the cab against may have been made using the same make and model of guitar cabinet, it wasn't made with the *same* guitar cabinet you're trying to null it with. Nor in the same room, nor with the same microphone.
  #19  
Old October 23rd 19, 09:56 AM posted to rec.audio.pro
James Price[_6_]
external usenet poster
 
Posts: 11
Default Why don't these signals null?

On Wednesday, October 23, 2019 at 12:35:16 AM UTC-5, PStamler wrote:
> If I understand what you're describing, you're trying to null a signal that's
> been run through a guitar cabinet with one that's been run through a
> *simulation* of a guitar cabinet.


No. In the first instance, I'm referring to nulling a signal that's been sent through a miked guitar cabinet exclusively. However, you can also try sending the signal through an impulse response of a guitar cabinet and it won't null.
  #20  
Old October 23rd 19, 02:01 PM posted to rec.audio.pro
[email protected]
external usenet poster
 
Posts: 608
Default Why don't these signals null?

the op is trying to null the 2 re-amped re- recordings to each other.

OP, you got a -30 dB to -50 dB result which is very good.

There are bound to be slight differences in room noise between the two takes. Or a window curtain moved slightly.

Consider that a -40 dB down null means the two signals matched each other to within 1 part in 100.

What did the null signal sound like?

Mark


 




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 10:24 AM.


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