improve explanation of test setup

diff --git a/_manual/17_mixing/02_panning/01_stereo_panner.html b/_manual/17_mixing/02_panning/01_stereo_panner.html
index 81af117a7a91a8cb3acaf68de4587089dbafbcc7..b0807386b6261acb26e4270a2118b20a31791fd8 100644 (file)
--- a/_manual/17_mixing/02_panning/01_stereo_panner.html
+++ b/_manual/17_mixing/02_panning/01_stereo_panner.html
@@ -10,7 +10,7 @@ title: Stereo Panner
   position=center (L=50%, R=50%). This panner assumes that the signals
   you wish to distribute are  either uncorrelated (that means totally 
   independent), or they contain a stereo image which is 
   position=center (L=50%, R=50%). This panner assumes that the signals
   you wish to distribute are  either uncorrelated (that means totally 
   independent), or they contain a stereo image which is 

-  mono-compatible<sup><ahref="#caveat">*</a></sup>.
+  mono-compatible<sup><a href="#caveat">*</a></sup>.

 </p>
 <div class="well">
 <p>
 </p>
 <div class="well">
 <p>


@@ -191,40 +191,57 @@ title: Stereo Panner
 <dd>move position 1&deg; / 5&deg;to the right</dd>
 </dl>
 
 <dd>move position 1&deg; / 5&deg;to the right</dd>
 </dl>
 

-<h2><a name="caveat" />Panning caveats</h2>
+<h2><a name="caveat"></a>Panning caveats</h2>

 
 

-<p>
+<div class="well">

 Note that the stereo panner will introduce unwanted side effects on
 material that includes a time difference between the channels, such
 as AB, ORTF or NOS microphone recordings, or delay-panned mixes.<br />   
 With such signals, when you reduce the with, you are summing two signals
 with different delays, which will introduce comb filtering.
 Note that the stereo panner will introduce unwanted side effects on
 material that includes a time difference between the channels, such
 as AB, ORTF or NOS microphone recordings, or delay-panned mixes.<br />   
 With such signals, when you reduce the with, you are summing two signals
 with different delays, which will introduce comb filtering.

-</p>
+</div>

 <p>  
 Let's take a look at what happens when you record a source at 45° to the
 <p>  
 Let's take a look at what happens when you record a source at 45° to the

-right side with an ORTF array (cardioids, spacing 17cm, opening angle
-110°):<br />
-The time difference is 350 usecs or approximately 15 samples at 44k1. The
-level difference due to the directivity of the microphones is about 7.5dB.
+right side with an ORTF array and then manipulate the width.
+</p>
+<p>
+For testing, we apply a pink noise signal to both inputs of an Ardour stereo
+bus with the stereo panner, and feed the bus output to a two-channel analyser. 
+Since pink noise contains equal energy per octave, the readout is a straight line:

 </p>
 <img src="/images/stereo-panner-with-ORTF-fullwidth.png" />
 <p>
 </p>
 <img src="/images/stereo-panner-with-ORTF-fullwidth.png" />
 <p>

-For testing, we apply a pink noise signal, which displays as a straight line
-in the analyser. To simulate an ORTF, we use Robin Gareus' stereo balance
+To simulate an ORTF, we use Robin Gareus' stereo balance

 control LV2 to set the level difference and time delay. Ignore the Trim/Gain
 control LV2 to set the level difference and time delay. Ignore the Trim/Gain

-- its purpose is just to align the test signal with the 0dB line of the
+&mdash; its purpose is just to align the test signal with the 0dB line of the

 analyser.
 </p>
 analyser.
 </p>

+<p> 
+Recall that an ORTF microphone pair consists of two cardioids spaced 17 cm
+apart, with an opening angle of 110°.<br />
+For a source at 45° to the right, the time difference between the capsules 
+is 350 usecs or approximately 15 samples at 44.1 kHz. The level difference 
+due to the directivity of the microphones is about 7.5dB.
+</p>

 <p>
 Now for the interesting part: if we reduce the width of the signal to 50%,
 the time-delayed signals will be combined in the panner. Observe what
 <p>
 Now for the interesting part: if we reduce the width of the signal to 50%,
 the time-delayed signals will be combined in the panner. Observe what

-happens to the frequency response:
+happens to the frequency response of the left and right outputs:

 </p>
 <img src="/images/stereo-panner-with-ORTF-halfwidth.png" />
 <p>
 </p>
 <img src="/images/stereo-panner-with-ORTF-halfwidth.png" />
 <p>

+You may argue that all spaced microphone recordings will get comb filters
+later, when the two channels recombine in the air between the speakers. But
+perceptually, this is a world of difference, since our hearing system is
+very good at eliminating comb filters in the real world, if their component
+signals are spatially separated. But once you combine two delayed signals
+inside your signal chain, this spatial separation is lost. As usual, you
+get to keep the pieces.
+</p>
+<div class="well">

 Depending on your material and on how much you need to manipulate the width,
 Depending on your material and on how much you need to manipulate the width,

-the comb filter may be acceptable. Then again, it may not be. Listen
-carefully for artefacts if you manipulate unknown stereo signals - many
+the comb filter may be acceptable. Then again, it may not. Listen
+carefully for artefacts if you manipulate unknown stereo signals &mdash; many

 orchestra sample libraries for example do contain time-delay components.
 orchestra sample libraries for example do contain time-delay components.

-</p>
+</div>