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 Post subject: SPEC 4.0
PostPosted: Wed Sep 16, 2009 7:25 am 
SBU Wiki Team
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Joined: Sun Aug 30, 2009 7:01 am
Posts: 212
Note: Not the current version. Attachment deleted.

SPEC 4.0

SPEC 4.0 is a powerful Plogue Bidule layout giving you several processing options:

  • CC (Center Cut): An algorithm borrowed from Center Cut GUI but implemented using Plogue spectral bidules
  • SLICE: An algorithm slicing the stereo field up into SL, FL, C, RF, SR using multiple stages of SPEC Center Cut
  • LCR: A set of simple spectral algorithms combining the original L and R channels
  • ArCTan: An algorithm smoothly expanding and spreading the stereo field up to 360 degrees; ArcTan also has an option to blend in SLICE rears
  • ZPan: A Constant Power Panner allowing you to widen or narrow your conversion and make your speakers disappear into the soundfield

SPEC 4.0 and ZPan were developed by Glenn C. Newell. All methods except LCR are written in C++ utilizing the Bidule SDK, to minimize DSP Load.

For a complete workflow on performing a full conversion using SPEC 4.0, see this guide: Your first conversion.

Important note: If you are running a 64 bit OS and the 64 bit version of Plogue Bidule, the current SPEC 4.0 plugins probably will not work because they were compiled for 32 bits. In general, running the 32 bit version of Plogue, even on a 64bit OS, is recommended. Otherwise, you are going to run into the 64 vs. 32 bit issue again and again with any VSTs and/or plugins. We are not aware of any advantage to running the 64 bit version of Plogue Bidule for what we do on this site.


  1. Preparing for SPEC 4.0
  2. Using the SPEC 4.0 layout
  3. Using ZPan

  1. Preparing for SPEC 4.0

    • Install and get familiar with Plogue Bidule as described in this guide.
    • Install the Microsoft Visual C++ 2008 SP1 Redistributable Package. At the time of this writing, you can download this package here.
    • Download the following package and extract its full content to a temporary folder with a rar unpacking utility:

      • In the temporary folder, double-click on install.bat. Answer the question about the drive where Bidule is installed (normally "C:") and press Enter. This will quickly and automatically perform the following steps:

        • Create a "Bidule\plugins" folder if it does not exist. Note that this is not the "VST Plugins path" as described in the Plogue Bidule guide. It is rather a specific folder named "plugins".
        • Copy the SPEC 4.0 layout file into your Bidule\layouts folder.
        • Copy the four required SPEC dll's into your Bidule\plugins folder.
        • Copy the LivePC dll into your Bidule\plugins folder. LivePC was written by "pcournoyer" and its home page is here. Live PC shows up in Plogue as “Live PC” on the palette menu.
        • Install a new VST plugin (HNM_filter.dll) in the "Bidule\VSTPlugins" folder. If this is not your "VST Plugins path", you should manually move HNM_filter.dll to your "VST Plugins path" before restarting Bidule.

      • In the installation package, the "non-SSE2 ArcTan plugin" folder contains a version of the ArcTan plugin for CPU's not supporting SSE2 extensions. Should you have a CPU that doesn't support SSE2 extension (doubtful), you should extract the ArcTanPanMB-non-SSE2.dll to the the Program Files\Plogue\Bidule\plugins folder (one or the other ArcTan dll's goes into your plugins folder, NOT both!).
      • At the end of the installation, you MUST restart Bidule to let it detect the new dll's.
      • Open the SPEC 4.0 layout in Plogue Bidule.

  2. Using the SPEC 4.0 layout

    • Double-click on the SPEC 4.0 group to open the group controls:

      • Instructions: Click this check box to open a short and crisp set of instructions.
      • Pre Gain – Input Gain: This slider uniformly affects the volume level of all channels. Typical values are -10 to –4 dB. To set this value, you have a couple of options:

        • Follow the Plogue Bidule - Monitoring Surround Output on your PC guide and raise the slider until you start hearing distortion and/or clipping in loud passages. Lower the slider to eliminate the distortion. Note that it is safer to use a low pre-gain value to avoid clipping.
        • While playing the audio, right-click on the SPEC 4.0 group, select Monitor and watch for clipping (red clip indicators) in the lower left six channels. Lower the slider to eliminate the clipping.

      • Method Selection: You need to have processing turned on (the On/Off button in Plogue Bidule) when you change methods. Check the processing indicators, below the method selection drop down, to make sure your selection is effective (processing). Also note, you need to select the CC method when setting the FFT Latency. Once set, change your method back to the one you want to use for conversion.
      • Method Controls: Use these checkboxes to open or close the additional method specific controls.
      • FFT Window Type: All of these sound pretty similar except Rectangular. Choose the one you like (Rectangular may require a more negative pre-gain than the others).
      • Check and Set FFT Latency: This procedure is required to set the FFT Delay time and thereby keep all the channels in sync.

        • Turn processing ON, but stop any audio playback.
        • Select the CC Method. Make sure the indicator says “Processing” next to CC.
        • Press the "Check and Set FFT Latency" button in the SPEC 4.0 group controls. The Resulting number of samples will show. A result of Zero, or 44544 means you did something wrong.
        • After saving the SPEC group, for use in other layouts, and saving the current layout you shouldn't have to do this again, unless you change your DSP FFT settings in Plogue Preferences.

          On faster computers, your DSP settings (in Plogue Bidule Preferences) should be:

          FFT Window Size: 8192
          FFT Overlap: 16
          Higher Precision FFT: Checked

          However, if that creates too much DSP load, you can still get good quality with:

          FFT Window Size: 4096
          FFT Overlap: 4
          Higher Precision FFT: Checked

          The "overlap" seems to be what affects the DSP load the most.

      • Additional Bass Boost: Adds bass in the LFE channel, using HNM filter.
      • Open Bass Boost Controls: Opens additional controls for Bass Boost.
      • Output Gains: Use to control surround balance in standalone methods, or to control the levels to other bidules in your layout. The FL and SL Gains will move the FR and SR gains as a pair, but you can adjust the FR and SR gains independently if you need to. To calculate the proper gain values, use the tools and procedures described in the Toolkit - Gain Calculation Spreadsheet guide.
      • Method-specific controls: Near the top of the SPEC 4.0 group controls are four checkboxes to open controls specific to each algorithm (SLICE, CC, LCR and ArcTan).

        • SLICE controls

          • Stage One Humidity: A humidity of 1 = 100% wet, or SLICE processed signal. A humidity of 0 = 0% wet or 100% dry signal from the previous stage (or original left and right in the case of stage one). Humidities near one are used to decrease any artifacts heard in the outputs. Stage one is the humidity setting for the input of stage 2; it affects FL, FR, SL, and SR. A value of 0.70 is a good starting point.
          • Stage Two Humidity: Stage two is the humidity setting for the SL and SR outputs. A value of 0.85 is a good starting point.
          • Wrap Rears: Check this box to add a third stage of separation. This has the effect of taking what was the extreme outsides of the original stereo field and placing them in both rear speakers, creating a virtual center rear. This causes the sound field to wrap around you 360 degrees.
          • Wrap Humidity: This setting is enabled when the Wrap Rears checkbox is checked. A value of 1.0 is a good starting point.

        • CC controls

          • Rear Humidity: Sets the humidity for the SL and SR outputs.
          • Wrap Rears and Wrap Humidity: These settings work as for SLICE.

        • LCR controls

          • N and M Factors: These settings affect only the SL and SR output channels, but they psycho-acoustically interact with all the other channels. Standard values are 1.0.

        • ArcTan controls

          • Image Width: ArcTan stretches the angle over which the stereo image is spread out to your surround speakers. The Image Width parameter sets the full angle over which this stretching takes place, with the center speaker in the middle of this angle. Typical values range from 240 to 360, or in other words, 120 to 180 degrees on both sides of the center speaker.
          • Rearward Bias: This parameter accentuates the soundfield more towards the rear speakers from the front and center without going over the specified Image Width angle. The default value is 1.0, which preserves the original bias of the soundfield and saves a small amount of DSP load.
          • Re-Center: As you move the Rearward Bias control to the right, you may find that the center channel sound “slips away” from the center channel to one side or the other. The Re-Center parameter brings the “central” sound back to the center speaker. The Re-Center control is only needed in combination with larger settings of the Rearward Bias parameter. Otherwise, Re-Center should be left at the center or 0.0 position.
          • Mode: This parameter sets how the sound is distributed into the surround field:

            • Pythagoras: This should be the most accurate reproduction/expansion of the original mix (but not necessarily the most acoustically pleasing).
            • Across: With this setting, louder sounds are concentrated near the front speakers and quieter sounds near the rear speakers. Note that the end result is also affected by the output gain values applied to each channel. This will usually give a “fuller” sound, with more sound being concentrated toward the front and center speakers.
            • Diagonal: This setting puts sounds that are slightly off center behind you, in both rears. It works well with songs where harmony vocals are panned just a little left or right (vs. the lead vocal in the center). Note that larger Rearward Bias settings are another possible way to spread out things panned only slightly off center in the original stereo.
          • Speaker Angles: Because ArcTan depends on your speakers to accurately render each sound in the precise angle location calculated, it needs to pan it between the pair of adjacent speakers where it should fall. As a result, it needs to know where your speakers are located. Speaker angles are measured counterclockwise, starting from the center speaker at 0 degrees. The default values should fit most setups. Note that in this layout, the ArcTan speaker angles are linked from the ZPan speaker angles, so you can set your speaker angles once in Zpan, and have ArcTan also be set correctly (the reverse is not true).
          • Adjacent Speaker Controls: This checkbox opens/closes controls to add in some signal destined for each speaker to the speakers on either side of it. This can “fatten” or “fill in” the sound.

            • Adjacent Speaker Level: With the slider all the way to the left (default), this control is “off”.
            • Wrap Rears: This parameter lets you have the opposite rear speaker included (Wrap Rears ON) or not.
          • Blend Controls: Rather than simple humidity controls, ArcTan’s Blend Controls let you select the source of the “dry” signal to blend with its outputs. The below screen shot shows the default settings. With all controls set to 1.0 you will hear the “pure” output of the ArcTan method.

            The Rear Blend faders allow you blend in rears from the SLICE method. ArcTan fronts and 67% blended SLICE rears (sliders set at 33%) is an excellent combination for many types of music. Using ArcTan AND SLICE at the same time does increase the DSP load however, so you should keep the “Activate SLICE” drop down on “MUTE” if your not using SLICE blended rears.

  3. Using ZPan

    As an alternative to ArcTan, Zpan allows you to place the sound between speakers vs. having the sound come directly from the speakers. This widens or “opens up” the sound (or narrows it) as well as creates a balanced sound field in which your speakers “disappear”.

    • Pan Angles: For the right side, Pan Angles are measured in degrees clockwise from center (positive). For the left side, they are measured counterclockwise from zero (negative). So the range of panning is from -180 degrees to 180 degrees.

      A negative pan angle equal to the angle from center to your left rear speaker would result in the sound coming directly from your left rear speaker. The easiest way to get a feel for this is to use the Output Gain controls in SPEC to turn off all but one channel, and then move the ZPan pan control for that channel around to hear the result.

      The “C Pan” Control has no effect unless you check off the “Pan Center” checkbox. This is to save DSP load.

      When processing is ON in Plogue Bidule, angle sliders move in corresponding pairs as controlled by the "left" speakers.

    • Speaker Angle Settings: This checkbox opens a window to set the speaker locations. It works exactly as for ArcTan. Note that if the Pan Angles are set to match the position of your speakers, ZPan has no effect on the sound.


SLICE and CC use the Center Cut Algorithm, from:

ArcTan and Zpan use Constant Power Panning Algorithms from:

Portions of the C++ code come from the Plogue Bidule SDK 1.03:

Click here for comments, feedback and discussion.

Change History

2009-09-15 Initial version published (Zeerround and Fan51)
2009-11-05 Note added about 64 bit Plogue Bidule and OS (Zeerround and Fan51)
2009-11-12 Batch installer added in the package; installation instructions modified accordingly (Fan51)

This guide is Copyrighted © 2009, Except for the HNM_Filter.dll plugin, the content of the SPEC 4.0 Release.rar attachment is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License, (Attribution should be to “Glenn C. Newell”) and is work derived from other people's ideas, done in new ways.

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