259 lines
10 KiB
HTML
259 lines
10 KiB
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<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
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<meta name="generator" content="Adobe RoboHelp 9">
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<title>Crossover</title>
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<style title="hcp" type="text/css">
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</head>
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<body class="ns-0 ltr">
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<div id="globalWrapper">
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<div id="column-content">
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<div id="content">
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<h1 class="firstHeading">Crossover</h1>
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<div id="bodyContent">
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<p id="siteSub"><img src="Crossover.JPG" alt="" border="0"></p>
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<p>A fully featured loudspeaker management processor consisting
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of various alignments of crossover filters, <a href="MAINGainMute.htm">gain</a>
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controls, and mid-band <a href="Limiter.html">limiters</a>.
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The limiter is a two-stage protection limiter for protecting
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against amplifier clipping and loudspeaker damage. The
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first stage has ballistics suitable for long term protection
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whilst retaining transparency and minimising signal level
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loss. The second stage has much faster ballistics to protect
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against loudspeaker over-excursion. Limiter ballistics
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are automatically set by the system to give the optimum
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performance based on the high-pass frequency of the band.
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Options include <a href="Delay.html">delays</a>, <a href="MAINPhase_Filter.htm">phase
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filters</a> and limiter metering.</p>
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<p> </p>
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<h2>Inputs and Outputs</h2>
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<p>The single channel crossover has</p>
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<ul>
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<li class="p"><p class="hcp1">One audio
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output per band</p></li>
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<li class="p"><p class="hcp1">One common
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audio input.</p></li>
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<li>When the option for Inserts On is selected, there
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is one input per band.</li>
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</ul>
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<p> <br>
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The stereo crossover has</p>
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<ul>
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<li class="p"><p class="hcp1">2 audio
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outputs per band</p></li>
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<li class="p"><p class="hcp1">2 audio
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inputs.</p></li>
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<li>When the option for Inserts On is selected, there
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are 2 inputs per band.</li>
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</ul>
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<p>Adjustment of controls has the same effect on both input
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channels and the corresponding band output channels.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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<h2>Properties</h2>
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<h4>Number of Bands (1-6)</h4>
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<ul>
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<li class="p"><p>Select the number of output bands
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in the crossover.</p></li>
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</ul>
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<h4>Delay (off/on)</h4>
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<ul>
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<li class="p"><p>A delay-line may be inserted into
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each band for aligning loudspeaker drivers in
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time.</p></li>
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</ul>
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<h4>Meters (off/on)</h4>
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<ul>
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<li class="p"><p>Metering may be added to monitor
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the action of the limiters.</p></li>
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</ul>
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<h4>Phase Filters (off/on)</h4>
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<ul>
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<li class="p"><p>Phase filters may be included
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to apply phase shifts between adjacent bands for
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fine-tuning alignment.</p></li>
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</ul>
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<h4>Inserts (off/on)</h4>
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<ul>
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<li class="p"><p>The input feeds to the crossover
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filters are normally internally connected together
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to form a single common input, they may optionally
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be split into separate inputs so that <a href="Equalisation.htm">equalisation</a>
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(for example) can be uniquely applied to individual
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outputs without disturbing the calibration of
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the limiter.</p></li>
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</ul>
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<h4>Filters (out/24dB/48dB)</h4>
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<ul>
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<li class="p"><p>For each band the high and low
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filter roll-off slopes can be set individually.</p></li>
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</ul>
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<h4>Signal Names</h4>
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<ul type="disc">
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<li class="p"><p>Custom signal names can be inserted
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for each output band. Placing the '$' symbol in
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front of the name will cause that output name
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to be preceded by the signal name at the input</p></li>
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</ul>
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<h4>Low Frequency Optimisation</h4>
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<ul type="disc">
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<li class="p"><p>Defaults to YES.  Optimised
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IIR filter for improved low frequency performance.
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 This is optional to maintain backwards compatibility
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with existing designs.</p></li>
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</ul>
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<h2>Control Panel</h2>
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<p><img src="Crossovercp.JPG" alt="image:crossovercp.JPG" title="image:crossovercp.JPG" style="border-width: 2px;
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border-style: solid; margin-top: 0px; margin-bottom: 0px;
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margin-left: 0px; margin-right: 0px;" width="665" height="654" border="2"></p>
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<p>The graphical representation of crossover areas
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indicates what part of the frequency range each band
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occupies. Each band is represented by a different
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colour curve. A triangular control handle is provided
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at each band edge, an upward triangle for the lower
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band edge and a downward triangle for the upper band
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edge. These are initially paired with the corresponding
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control handle of the adjacent band edge at thge same
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frequency, but can be split to provide a frequency
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offset between bands. A further set of control handles
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allow the crossover point of both bands to be adjusted
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together maintaining any offset.</p>
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<p> </p>
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<h2>Parameters</h2>
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<h4>Filter Type</h4>
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<ul>
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<li class="p"><p class="hcp1">This
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combo box selects the type of response for a crossover
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band edge (the crossover filter 'shape').</p></li>
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<li>Note that the shape can be set differently
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on each band edge and, even on adjacent band edges,
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although this latter situation is probably best
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avoided in audio terms.</li>
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</ul>
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<p>The filter types available are:</p>
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<ul>
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<li class="p"><p class="hcp1">Butterworth
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6dB/Octave</p></li>
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<li class="p"><p class="hcp1">Butterworth
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12dB/Octave</p></li>
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<li class="p"><p class="hcp1">Bessel
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12dB/Octave</p></li>
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<li class="p"><p class="hcp1">Linkwitz-Riley
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12dB/Octave</p></li>
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<li class="p"><p class="hcp1">Butterworth
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18dB/Octave</p></li>
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<li class="p"><p class="hcp1">Butterworth
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24dB/Octave</p></li>
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<li class="p"><p class="hcp1">Bessel
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24dB/Octave</p></li>
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<li class="p"><p class="hcp1">Linkwitz-Riley
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24dB/Octave</p></li>
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<li class="p"><p class="hcp1">Neville
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Thiele Method 36dB/Octave</p></li>
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<li class="p"><p class="hcp1">Butterworth
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48dB/Octave</p></li>
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<li class="p"><p class="hcp1">Butterworth
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48dB/Octave</p></li>
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<li>Neville Thiele Method 52dB/Octave</li>
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</ul>
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<h4>Frequency</h4>
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<ul>
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<li class="p"><p class="hcp1">Drag
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nodes horizontally with the mouse to change the
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crossover frequency. Normally the node at the
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intersection of two adjacent bands would be moved
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so that the adjacent bands track together.</p></li>
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<li class="p"><p class="hcp1">Some
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applications require adjacent crossover frequencies
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to be offset (overlapped for example). This can
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be done by selecting one band edge so it can be
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moved independently.</p></li>
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<li>Alternatively, the Frequency control below
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the window may be adjusted.</li>
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</ul>
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<h4>Gain control</h4>
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<ul>
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<li class="p"><p class="hcp1">Trims
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the output level of the band.</p></li>
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<li>The gain control is before the limiter, so
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does not alter the calibration of the limiter
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threshold.</li>
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</ul>
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<p><span style="font-weight: bold;">!</span> This control
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is capable of raising signal levels beyond the clipping
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point; so, care should be exercised when using positive
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gain values.</p>
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<h4>Delay spin box (for each band)</h4>
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<ul>
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<li class="p"><p>This sets a delay time on the
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band with default units in milliseconds. Units
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may be changed in the properties grid to metres,
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feet or frames.</p></li>
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</ul>
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<h4>Polarity button</h4>
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<p>Reverses the polarity of the band.</p>
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<h4>Mute button</h4>
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<ul>
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<li class="p"><p>Silences the band output.</p></li>
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</ul>
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<h4>Limiter Threshold control</h4>
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<ul>
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<li class="p"><p class="hcp1">Adjusts
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the level threshold above which limiting will
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take place.</p></li>
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<li>If other processing objects are connected between
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the output of the crossover and the output, the
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limiter threshold setting may be inaccurate, and
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the user must compensate for level changes which
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occur in these objects.</li>
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</ul>
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<h4>Meter</h4>
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<ul>
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<li class="p"><p>Displays the input signal level
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relative to the limiter threshold.</p></li>
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</ul>
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<p>A reading of 0dB corresponds to the limit threshold,
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whereas a reading of +6dB for instance means the signal
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is exceeding the threshold by 6dB, and is being compressed
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by 6dB.</p>
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<h4>Phase spin box (on control panel)</h4>
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<ul>
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<li class="p"><p class="hcp1">Adjusts
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the phase shift applied between a pair of bands.</p></li>
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<li>As there is some interaction between the phase
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controls, it is recommended that the highest frequency
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band phase be adjusted first, and then successively
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lower ones.</li>
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</ul>
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</div>
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</div>
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</div>
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</div>
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</div>
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<p class="hcp1"> </p>
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</body>
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</html>
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