C-DSP 6X8
6-IN 8-OUT IN-CAR AUDIO PROCESSOR
User Manual
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Revision
Description
Date
V0.1
Preliminary version
28 August 2015
V1.0
First release
9 September 2015
Revision history
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CONTENTS
Important Information ......................................................................................................................................... 5
System Requirements ...................................................................................................................................... 5
Disclaimer/Warning ......................................................................................................................................... 5
Warranty Terms ............................................................................................................................................... 6
FCC Class B Statement...................................................................................................................................... 6
CE Mark Statement .......................................................................................................................................... 6
A note on this manual ...................................................................................................................................... 6
1 Product Overview .......................................................................................................................................... 7
1.1 Sample usage ....................................................................................................................................... 7
1.2 The miniDSP concept ............................................................................................................................ 8
1.3 Plugin feature summary ....................................................................................................................... 8
2 The miniDSP workflow................................................................................................................................... 9
3 Installation and setup .................................................................................................................................. 11
3.1 Software installation .......................................................................................................................... 11
3.1.1 Windows .................................................................................................................................... 11
3.1.2 Mac OS X .................................................................................................................................... 12
3.2 Hardware connectivity ....................................................................................................................... 13
3.2.1 Analog inputs .............................................................................................................................. 13
3.2.2 Digital input ................................................................................................................................ 14
3.2.3 Analog outputs ........................................................................................................................... 14
3.2.4 DC power .................................................................................................................................... 15
3.2.5 Remote ....................................................................................................................................... 16
3.2.6 USB ............................................................................................................................................. 16
3.3 Synchronizing with the processor ....................................................................................................... 17
4 Configuring the processor............................................................................................................................ 18
4.1 Input tab ............................................................................................................................................ 19
4.2 Routing tab......................................................................................................................................... 20
4.3 Output tab ......................................................................................................................................... 20
4.3.1 Channel strip layout .................................................................................................................... 21
4.3.2 Channel label .............................................................................................................................. 21
4.3.3 Gain control and level monitoring ............................................................................................... 21
4.3.4 Crossover.................................................................................................................................... 22
4.3.5 Parametric EQ............................................................................................................................. 24
4.3.6 Time delay .................................................................................................................................. 26
4.3.7 Invert and mute .......................................................................................................................... 26
4.4 Custom biquad programming ............................................................................................................. 27
4.4.1 What’s a “biquad? ...................................................................................................................... 27
4.4.2 Using custom biquad programming ............................................................................................ 27
4.4.3 Biquad design software............................................................................................................... 29
4.5 Working with configurations .............................................................................................................. 30
4.5.1 Online and offline mode ............................................................................................................. 30
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4.5.2 Selecting a configuration ............................................................................................................ 30
4.5.3 Saving and loading configurations ............................................................................................... 31
4.5.4 Loading configurations from microSD card .................................................................................. 31
4.5.5 Restoring to defaults................................................................................................................... 32
4.6 Keyboard shortcuts ............................................................................................................................ 32
5 Using the C-DSP 6x8 .................................................................................................................................... 33
5.1 Status indicators ................................................................................................................................. 33
5.2 Controls ............................................................................................................................................. 33
5.3 Infrared remote control ...................................................................................................................... 34
6 Additional information ................................................................................................................................ 35
6.1 Specifications ..................................................................................................................................... 35
6.2 Troubleshooting ................................................................................................................................. 36
6.3 MCU firmware update ........................................................................................................................ 37
6.4 Obtaining support .............................................................................................................................. 37
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IMPORTANT INFORMATION
Please read the following information before use. In case of any questions, please contact miniDSP via the
support portal at minidsp.desk.com.
SYSTEM REQUIREMENTS
To configure the miniDSP audio processor, you will require a Windows PC or Apple Mac OS X computer with the
following minimum specification:
Windows
PC with 1GHz or higher processor clock speed. Intel® Pentium®/Celeron® family, or AMD K6®/AMD
Athlon®/AMD Duron® family, or compatible processor recommended.
512 megabytes (MB) of RAM or higher
Keyboard and mouse or compatible pointing device
USB 2.0 port
Microsoft• ® Windows® Vista® SP1/ XP pro SP2/Win7/Win8.1
Microsoft• ® .NET framework v3.5 or later
Adobe AIR environment (latest version)
Adobe Flash player (latest version)
Mac OS X
Intel-based Mac with 1 GHz or higher processor clock speed
512 megabytes (MB) of RAM or higher
Keyboard and mouse or compatible pointing device
USB 2.0 port
Mac OS X 10.4 or higher
Adobe AIR environment (latest version)
Adobe Flash player (latest version)
DISCLAIMER/WARNING
miniDSP cannot be held responsible for any damage that may result from the improper use of this product or
incorrect configuration of its settings. As with any other product, we recommend that you carefully read this
manual and other technical notes to ensure that you fully understand how to operate this product. The miniDSP
audio processor is a powerful tool, and misuse or misconfiguration, such as incorrectly set gains or excessive
boost, can produce signals that may damage your audio system.
As a general guideline, you should perform the initial configuration of the miniDSP audio processor before
enabling audio through any connected output device or amplification. Doing so will help ensure that the
software is correctly configured.
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Finally, note that the miniDSP audio processor is a very flexible device, and many of the questions we receive at
the tech support department are already answered in this user manual and in the online application notes on
the miniDSP.com website. So please take the time to carefully read this user manual and the online technical
support. Thanks for your understanding!
WARRANTY TERMS
miniDSP Ltd warrants this product to be free from defects in materials and workmanship for a period of one
year from the invoice date. Our warranty does not cover failure of the product due to incorrect connection or
installation, improper or undocumented use, unauthorized servicing, modification or alteration of the unit in any
way, or any usage outside of that recommended in this manual. If in doubt, contact miniDSP prior to use.
FCC CLASS B STATEMENT
This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:
This device may not cause harmful interference.
This device must accept any interference received, including interference that may cause undesired
operation.
Warning: This equipment has been tested and found to comply with the limits for a Class B digital device,
pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection. This
equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance
with the instructions, may cause interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause harmful interference to radio
or television reception, which can be determined by turning the equipment off and on, the user is encouraged to
try to correct the interference by one or more of the following measures:
Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.
Notice: Shielded interface cable must be used in order to comply with emission limits.
Notice: Changes or modification not expressly approved by the party responsible for compliance could void the
user’s authority to operate the equipment.
CE MARK STATEMENT
The C-DSP 6x8 has passed the test performed according to European Standard EN 55022 Class B.
A NOTE ON THIS MANUAL
This User Manual is designed for reading in both print and on the computer. If printing the manual, please print
double-sided. The embedded page size is 8 ½” x 11”. Printing on A4 paper will result in a slightly reduced size.
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1 PRODUCT OVERVIEW
Thank you for choosing the miniDSP C-DSP 6x8 audio processor. The miniDSP C-DSP 6x8 is a powerful and
flexible digital audio processor specifically designed for in-car audio systems. It features:
Isolated power supply designed for in-car use
Stereo digital S/PDIF input (RCA connector)
Four analog input channels, by terminal block (8 VRMS) or RCA connector (4 VRMS)
Eight analog output channels (RCA)
Volume control by external wired remote or infrared remote
Advanced audio tuning on every channel:
o Parametric EQ (peaking/high shelf/low shelf)
o Butterworth and Linkwitz-Riley crossovers up to 48 dB/octave
o Individual time delay and level adjustment
o Advanced biquad programming for an unlimited range of filters and crossover types
Matrix mixer for flexible channel assignment and configuration
Real-time configuration of all processing parameters
Four on-board presets, selectable by external wired remote or infrared remote
1.1 SAMPLE USAGE
The C-DSP 6x8 typically connects to a head unit with four output channels, and directly drives power amplifiers
for multiple loudspeakers or drivers. Because of its flexible internal routing, the C-DSP 6x8 can be used in a
variety of situations involving a mix of passive speakers, active speakers, and subwoofers.
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C-DSP 6x8 plugin
Number of digital input channels1
2
Number of analog input channels
4
Number of analog output channels
8
Digital input sample rate
44.1 to 192 kHz
Internal sample rate
48 kHz
Number of PEQ bands per block
6
Crossover order
6 to 48 dB/octave
Compressor block
No
Maximum per-channel time delay
15 ms
1.2 THE MINIDSP CONCEPT
The miniDSP concept is “one hardware unit + one software plugin = audio processing solution.” This concept
leverages the inherent flexibility of DSP (digital signal processing) to deliver a range of flexible but cost-effective
solutions.
Hardware unit
In this case, the hardware unit is the miniDSP C-DSP 6x8.
Software plugin
The software plugin is installed on your PC or Mac, and determines the processing that the DSP
will perform. It provides a friendly user interface, and downloads instructions into the miniDSP
hardware unit that tell it how to process the audio signal.
Other platforms
miniDSP makes many other boxed and kit hardware units with analog, stereo digital, and
multichannel digital (HDMI) connections. Some units feature inbuilt Class D amplification. See
the full range of miniDSP products.
1.3 PLUGIN FEATURE SUMMARY
The table below summarizes the key features of the C-DSP 6x8 plugin:
*1 two channels = single stereo digital signal
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2 THE MINIDSP WORKFLOW
We strongly recommend taking a methodical approach to your new miniDSP audio processor. Remember that
the audio processor is a powerful tool, and incorrect settings can potentially cause damage to your system.
Please follow the steps below carefully.
1. Download and install the plugin
When your order ships, your ordered plugin will be available from the User Downloads section
of the miniDSP website. Download and install your plugin, as described in Software installation
on page 11.
2. Familiarize yourself with the plugin
Before connecting your computer to the processor, it’s worth familiarizing yourself with the user
interface presented by the plugin. Click on and explore each of the tabs (Input, Routing, and
Output). For more information, see Configuring the processor starting on page 18.
At this time, the plugin is still in offline mode, so any changes you make will not be downloaded
into the miniDSP hardware. Since we will reset all of the processing parameters in the next step,
you can feel free to experiment at this point.
3. Reset all parameters
From the Restore menu, select the Factory Default option. This will reset all processing
parameters back to the defaults and ensure that you have a "clean slate" for the next step.
4. Perform initial configuration
Use the plugin to set up an initial audio processing configuration as intended for your
application. For example, typical things that can be done at this point are to:
Set the labels of input and output channels
Mute unused input and output channels
Set crossover frequencies and slopes
Set up any essential equalization
5. Save configuration
At this point, save your initial configuration to a file. A configuration is the set of all audio
processing parameters. You should save your configuration to a file on a regular basis, to ensure
that you do not lose your work if you inadvertently restore the miniDSP to default settings. For
more information on configurations, see Working with configurations on page 30.
6. Make audio connections
With the initial configuration done and now that you are familiar with the various controls, it’s
time to connect the miniDSP C-DSP 6x8 into your system. Ensure that all power is turned off
when making audio connections. See Hardware connectivity on page 13.
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7. Go into online mode
Apply power to the processor. (See DC power on page 15 for more information. Leave other
equipment turned off at this stage.) Connect the USB cable to your computer, click on the
Connect button, and select the Synchronize option. If all goes well, you are now in online mode,
and any changes that you now make in the plugin user interface will be immediately sent to the
processor.
Before proceeding, click on each Configuration preset button (Config 1, 2, etc.) to ensure that all
presets have been synchronized and/or set to defaults.
For more information, see Synchronizing with the processor on page 17.
8. Initial audio check
Power on your connected equipment, first on the input side (e.g. head unit), then on the output
side (e.g. power amps). Turn the volume on your C-DSP 6x8 down low (view the Master Volume
display in the plugin while turning the knob counter-clockwise) and start playing music or a pink
noise test signal. Gradually increase the volume until you hear audio quietly coming from the
speakers. Verify that the plugin is performing the intended function. (For example, if
implementing a two-way crossover, confirm that the tweeter is playing high frequencies, and
that the woofer is playing low frequencies.)
9. Fine-tune your configuration
With your initial setup running, you can now proceed to fine-tune and optimize your system.
You will need to perform acoustic measurements and use the configuration screens to adjust
processing parameters.
Be sure to save your configuration on a regular basis while working on fine-tuning it.
Configurations can be saved to different files, in order to archive different versions, or to enable
auditioning of alternative configurations.
10. Continue to operate offline
With your miniDSP processor configured, you can continue to operate in offline mode—that is,
without the computer connected. To do so, simply disconnect the USB cable. The processor
“remembers” the configuration last set, and will continue to operate without the computer.
Note: while in offline mode, the configuration can still be modified in the plugin interface. These
changes will not be downloaded to the processor until it is synchronized again. See Working with
configurations on page 30.
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3 INSTALLATION AND SETUP
3.1 SOFTWARE INSTALLATION
When your order ships, your ordered plugin (or plugins) will be available from the User Downloads section of
the miniDSP website. You will need to be logged into the website with the account you created when
purchasing. The User Downloads link is visible from the dropdown menu at the top right of the website page:
Navigate to the miniDSP Plug-ins section of User Downloads, then download the zip file under the heading C-
DSP. Double-click on it to unzip it. Then follow the installation procedure below according to your computer
type.
Note: the Adobe Air framework may need a network connection the first time the plugin is used. If the plugin
does not start properly, see Troubleshooting.
3.1.1 Windows
Prior to installing the miniDSP software, download and install the following programs. You will need to accept
the license agreements in order to successfully complete the installation.
Microsoft .NET framework (version 3.5 or later)
Latest version of Adobe Flash
Latest version of Adobe Air
If you haven’t updated these recently, you should download and install the latest versions prior to running the
miniDSP install program.
To install the miniDSP software, open the Windows folder of the download and double-click on the C-DSP-
6x8.exe program. We recommend accepting the default installation settings. Once installation is complete, the
C-DSP 6x8 plugin will automatically start. Since the plugin checks for a network connection when starting up, a
warning such as the following may appear. In this case, click on Allow access.
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3.1.2 Mac OS X
On versions of OS X from 10.7 (Lion) and later, you will need to inform the GateKeeper program that it is OK to
install and run this software. Go to System Preferences, then click on Security & Privacy and select the General
tab:
1. Click on the padlock icon in the lower left corner and enter your password, in order that you can make
changes to the settings.
2. Under the text “Allow Applications downloaded from:”, click on “Anywhere.”
Then, download and install the following programs. You will need to accept the license agreements in order to
successfully complete the installation:
Latest version of Adobe Flash
Latest version of Adobe Air
If you haven’t updated these recently, you should download and install the latest versions prior to running the
miniDSP install program.
To install the miniDSP software, open the Mac folder of the download, and double-click on the C-DSP-6x8.dmg
file to open it in a new window. Then double-click on the installer program, Install-C-DSP 6x8.app. Once
installation is complete, the C-DSP 6x8 plugin will automatically start.
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3.2 HARDWARE CONNECTIVITY
Connections to the C-DSP 6x8 are made on the front and rear panels.
3.2.1 Analog inputs
There are four analog output channels. Unbalanced connections can be made directly to the RCA jacks on the
front panel. Be sure to take careful note of the channel numbering shown in this diagram and on the front panel.
These inputs accept a maximum input voltage of 4 VRMS.
Alternately, connections can be made by connecting bare wire ends to the push-in terminal block. Remove the
terminal, and connect individual positive and negative wires to each set of screw terminals. After all connections
are secure, firmly re-insert the terminal blocks. These inputs accept up to 8 VRMS.
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3.2.2 Digital input
Connect a digital source to the S/PDIF coax (RCA) connector on the front panel.
Note: the digital input accepts only a stereo PCM digital signal. It does not accept encoded or multichannel
digital audio.
3.2.3 Analog outputs
There are eight analog output channels. Unbalanced connections are made from the RCA jacks on the rear panel
to the power amplifiers. Be sure to take careful note of the channel numbering shown in this diagram and on the
rear panel.
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3.2.4 DC power
The C-DSP 6x8 incorporates an isolated DC power convertor and is designed for direct connection to the
vehicle's power supply (nominally 12V). Power is connected via the four-way terminal block:
The terminal block also provides two pins for remotely switching power on and off. To enable the remote
enable, a jumper inside the unit needs to be moved.
REMOTE IN
This input will turn the C-DSP 6x8 on and off. This is a
useful feature for battery-operated systems, to avoid
draining the battery. A simple example is shown at right.
The behavior is as follows:
o 0V <REM IN <4V: C-DSP 6x8 is OFF
o 4V < REM IN < 12V: C-DSP 6x8 is ON
REMOTE OUT
This output supplies a delayed version of REM IN, to
trigger external equipment after a 2-second delay.
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3.2.5 Remote
The wire remote can be positioned anywhere in the vehicle and is connected via the supplied cable. The RJ11
plugs on each end simply plug into the base of the remote and into the rear panel of the C-DSP 6x8. The wired
remote also contains the receiver for infrared remote control.
3.2.6 USB
To configure the processor, connect its USB port to a USB 2.0 port on your computer using the supplied cable.
Note that USB is used only for configuration—audio data cannot be streamed to the processor over USB.
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3.3 SYNCHRONIZING WITH THE PROCESSOR
Communication with the processor takes place over a USB connection. Note that USB is used for control
purposes only. Audio data cannot be streamed to the processor over USB.
Ensure that the computer is connected to the processor by a USB 2.0 port. Then click on the Connect button:
The first time you connect, or if you have made any changes to any data in the user interface, the following
dialog box will appear:
The options are:
Synchronize Config
Download the currently selected configuration into the corresponding configuration preset of
the processor. After downloading the configuration data, the plugin is in online mode and any
changes to processing parameters will be downloaded immediately in real time. That is, the user
interface is now “live.”
Synchronize and Upgrade
This is similar to Synchronize Config, but also upgrades the internal data of the processor. This
option may appear after downloading and installing an updated version of the plugin.
Restore Config
Restore the data in the currently selected configuration to the factory defaults. When using this
option, any connected output equipment should be muted or powered off until you have set the
configuration to a working state. Note that the configuration data will be lost, so ensure that you
have saved the configuration to a file prior to using this option.
Cancel
This option cancels the attempt to connect to the processor. The plugin will remain in offline
mode.
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4 CONFIGURING THE PROCESSOR
The C-DSP 6x8 processor is configured with the C-DSP 6x8 plugin / user interface program. Once fully
configured, the computer is no longer required, as source and preset selection can be done with the wired
remote or an infrared remote control—see Using the C-DSP 6x8. If desired, however, the plugin can remain
connected during use for real-time (“live”) control of all audio processing.
This screenshot shows the C-DSP 6x8 plugin with the key areas highlighted:
During initial configuration of the processor, it is strongly recommended that any connected
amplification be muted or powered off.
The Mute button disables all audio output:
The Master volume display shows the current volume setting:
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4.1 INPUT TAB
The Input tab displays a row of input channel control strips:
Channel label
Each input channel has a customizable
label, which is shown at the top of the
channel strip. This label also appears on
the Routing tab. To change the label, click
on it, type a new label (up to eight
characters), and press the Return key.
Gain adjustment
The gain of each channel can be adjusted
by moving the Gain Adjustment slider, or
by typing the desired gain into the Current
Gain text box. The maximum gain setting is
12 dB, and the minimum gain setting is –72
dB. (0 dB, the default, is unity gain or no change in level.)
Meter
Click this button to bring up an overlay that displays the current signal level in real time. (The
plugin must be in online mode to display signal levels.)
PEQ
Click on this button to open the parametric EQ settings window for that channel. There are ten
parametric EQ filters on each input channel. For more details, see Parametric EQ on page 24.
Mute
Press this button to mute that input channel. A visual indicator shows that the channel is muted.
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4.2 ROUTING TAB
The Routing tab displays the matrix mixer, which sets up the routing from input channels to output channels.
The input channels are labeled along the left, and the output channels along the top. To make the routing matrix
easier to view, the labels of the input and output channels can be changed in the Input and Output tabs.
Each input-output channel assignment is turned on and off by clicking the button corresponding to the two
channels. This is the default routing:
Each output channel can have more than one input channel routed to it. In that case, those input channels are
mixed together. This can be used, for example, to mix left and right inputs for a subwoofer feed.
4.3 OUTPUT TAB
The Output tab displays a row of output channel control strips. All channels are identical.
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4.3.1 Channel strip layout
Each output channel has a complete "strip" of controls.
4.3.2 Channel label
Each output channel has a customizable label, which is shown at the top of the channel strip. This label also
appears on the Routing tab. To change the label, click on it, type a new label (up to eight characters), and press
the Return key.
4.3.3 Gain control and level monitoring
Gain adjustment
The gain of each channel can be adjusted by moving the Gain Adjustment slider, or by typing the
desired gain into the Current Gain text box. The maximum gain setting is 12 dB, and the
minimum gain setting is –72 dB. (0 dB, the default, is unity gain or no change in level.)
Meter
Click this button to bring up an overlay that displays the current signal level in real time. (The
plugin must be in online mode to display signal levels.)
The level meters are useful in many situations. For example, when adding filters with boost, monitor the level
meters with typical signals and maximum levels to ensure that there is no clipping. The meters can also be used
during normal operation to monitor for or to help locate level or gain structure problems.
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4.3.4 Crossover
Each output channel has independent high pass and low pass filters. Click on the Xover button to open the
crossover settings window:
Crossovers “split” the frequency band to send to different drivers. In a two-way loudspeaker, for example, a low
pass filter is used to remove high frequencies from the signal sent to the woofer, and a high pass filter is used to
remove low frequencies from the signal sent to the tweeter. In a three-way speaker, the midrange driver will
use both the high pass and low pass filters. Crossover filters can also be used to limit low frequency content
delivered to a speaker or subwoofer, to help protect it from over-excursion.
Unlike conventional analog crossovers, the flexibility of DSP allows a completely arbitrary mix of different filter
slopes and types. Filters can be set at any frequency, or disabled completely. This allows maximum flexibility in
matching your crossover to the acoustic characteristics of the loudspeaker drivers.
Hovering the mouse over the curve brings up an overlay showing the frequency and the attenuation at that
frequency.
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Basic/Advanced
By default, the crossover is in basic mode, and shows the controls described below. Advanced
mode enables custom biquad programming for almost infinite flexibility in crossover filter
implementation. This is described in Custom biquad programming on page 27.
Cutoff Frequency
Sets the nominal cutoff frequency of the crossover. In actual fact, the crossover has a more or
less gradual transition from “full on” to “full off,” as determined by the filter slope.
Filter type
Selects the type and slope of the filter. The steeper the slope, the more quickly frequencies
above or below the cutoff frequency are attenuated. There are three types of filter:
Butterworth (BW)
Available in 6, 12, 18, 24, 30, 36, 42, and 48 dB/octave, Butterworth crossover
filters are 3 dB down at the cutoff frequency.
Linkwitz-Riley (LR)
Available in 12, 24, 36, and 48 dB/octave, Linkwitz-Riley crossover filters are 6 dB
down at the cutoff frequency.
Bessel
Available in 12 dB/octave only, a Bessel filter gives a more gradual roll-off
through the crossover region.
Bypass
Clicking on the Bypass button disables or enables that
high pass or low pass filter. The filter is bypassed when
the button is greyed out, as shown at right.
Each channel can be linked to one other channel. When a channel is linked to another, the crossover settings of
that channel are mirrored to the other. Typically, the corresponding drivers on the left and right channels are
linked: left and right tweeter, left and right woofer, and so on. To link a channel, select the other channel from
the drop-down menu at the top left of the Xover screen, and click the Link checkbox.
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4.3.5 Parametric EQ
Parametric equalization (PEQ) is a flexible type of equalization filter. It can be used to correct for errors in
loudspeaker output, to compensate for acoustic room effects, and to tailor the overall system response for best
sound. Click on the PEQ button to open the parametric equalizer settings window:
There are six parametric EQ filters on each input and output channel. The window displays a frequency response
graph showing the combined response of all enabled parametric filters on that channel. For example, the
screenshot above shows a response curve created with a low-shelf boost filter at 100 Hz, a dip at 500 Hz, and a
high-shelf cut filter at 5000 Hz.
Hovering the mouse over the curve brings up an overlay showing the frequency and the gain at that frequency.
Each channel can be linked to one other channel. When a channel is linked to another, the PEQ settings of that
channel are mirrored to the other. Typically, the corresponding drivers on the left and right channels are linked:
left and right tweeter, left and right woofer, and so on. To link a channel, select the other channel from the
drop-down menu at the top left of the PEQ screen, and click the Link checkbox.
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EQ band selection
Click on the radio buttons EQ1, EQ2, etc. to display the parameters for that filter.
Basic/Advanced
By default, each filter is in basic mode, and shows the controls described below. Advanced mode
enables custom biquad programming for almost infinite flexibility in filter implementation. This
is described in Custom biquad programming on page 27.
Filter type
Selects the type of filter:
PEAK Create a dip or a peak in the frequency response.
LOW_SHELF Reduce or increase part of the frequency spectrum below a given frequency.
HIGH_SHELF Reduce or increase part of the frequency spectrum above a given frequency.
SUB_EQ Create a dip or a peak in the frequency response at low frequencies (10 to 50
Hz). This filter type is similar to PEAK but gives more accurate results for low
frequencies. Note that activating any SUB_EQ filter reduces the number of
available filters on that channel from six to five.
Frequency
For the PEAK and SUB_EQ filter types, this is the center frequency of the peak or dip. For the
HIGH_SHELF and LOW_SHELF filter types, this is the frequency at which the gain is half of the set
value.
Gain
For the PEAK and SUB_EQ filter types, this is the gain in dB at the center frequency. For the
HIGH_SHELF and LOW_SHELF filter types, this is the gain in dB reached at high or low
frequencies respectively. A filter has no effect if its gain is set to 0 dB. Gain can be adjusted in
increments of 0.1 dB up to +/- 16 dB.
Q
Q controls the “sharpness” of the filter. For the PEAK and SUB_EQ filter types, lower Q gives a
broader peak or dip, while higher Q gives a narrower peak or dip. For the HIGH_SHELF and
LOW_SHELF filter types, Q controls how quickly the filter transitions from no gain to maximum
gain.
Bypass
The Bypass button enables or disables a filter. The filter is
bypassed if the button is greyed out, as shown at right.
(Note that all other filters are still operational unless
individually bypassed.) A filter will also have no effect if its gain is set to 0.0.
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4.3.6 Time delay
A delay of up to 15 ms can be applied to each output channel. To set the delay, click in the delay entry box for a
channel. The delay value can be entered numerically, and the up and down arrows can be used to change the
delay in small (0.02 ms) increments.
The time delay corresponds to a distance. This distance is shown in cm when the cursor is hovered over the time
delay box. The maximum time delay of 15 ms corresponds to a distance of approximately 5.2 meters (about 18
feet).
Time delay can be calculated from distance using one of the following formulae:
(Time delay in ms) = (Distance in cm) / 34.4
Or:
(Time delay in ms) = (Distance in inches) / 13.54
4.3.7 Invert and mute
Each channel can be inverted in polarity, and individually muted. When either of these options is selected, the
display changes color and the label of the button reflects the current state.
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4.4 CUSTOM BIQUAD PROGRAMMING
Custom biquad programming is available in the PEQ and Crossover blocks. Its purpose is to allow you to directly
provide the low-level parameters aka biquad coefficients that control the digital filters of the processor, thus
providing an almost infinite degree of flexibility.
For example, you can create hybrid crossovers with staggered cutoff frequencies, create parametric EQ filters
beyond those provided in the easy-to-use “basic” interface, implement a Linkwitz transform, or mix crossover
and EQ biquads in the same block.
4.4.1 What’s a “biquad?
A biquad is the basic unit of processing that is used to create digital filters. It can be described either with an
equation or with a signal flow diagram, as shown here:
A single biquad like this can perform a great many functions, including all of the functions of a single parametric
EQ filter, one 6 or 12 dB/octave high pass or low pass filter, and more. Biquads are combined in series
(cascaded) to create more complex filters. The function that each biquad performs is determined by just five
numbers: a1, a2, a0, b1, and b2. These numbers are called the coefficients.
4.4.2 Using custom biquad programming
Each crossover block and PEQ filter has a selector that switches it to advanced mode:
In advanced mode, the biquad coefficients can be pasted directly into the user interface. These coefficients must
be calculated using a design program – see Biquad design software below for suggestions.
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Parametric EQ advanced mode
In the parametric EQ blocks, advanced mode allows each individual filter to be specified by its
biquad coefficients. After pasting in the coefficients, click on the Process button for them to take
effect.
Parametric EQ file import (REW integration)
Multiple biquads in the parametric EQ block can be set at once by importing a coefficient file.
(Click on the IMPORT button.) This file can be generated by Room EQ Wizard (REW) or by other
programs. The design program must be set for a 48 kHz sample rate if using the C-DSP 6x8
plugin. The number of filters is limited to a maximum of six.
This example illustrates the correct file format:
biquad1,
b0=0.998191200483864,
b1=-1.9950521500467384,
b2=0.996920046761057,
a1=1.9950521500467384,
a2=-0.9951112472449212,
biquad2,
b0=0.999640139948623,
b1=-1.9981670485581222,
b2=0.9985489719847982,
a1=1.9981670485581222,
a2=-0.9981891119334211,
biquad3,
...
biquad4,
...
biquad5,
b0=1.0010192374642126,
b1=-1.9950555192569264,
b2=0.9940580112181501,
a1=1.995060938714333,
a2=-0.9950718292249559
Note that the last line must not have a comma at the end. If the file has less than six biquads,
then only that number of biquads will be imported. For example, if importing a file with four
biquads, the first four filters will be set, and the last two will not be changed. (Be careful: if the
last line ends with a comma, that counts as an extra biquad.)
If the file contains more than six biquads, then an error will be reported and no filters will be
changed.
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Crossover advanced mode
The Crossover blocks have eight biquads on each output channel. In Advanced mode, all eight
biquads need to be specified. After pasting in the coefficients, click on the Process button for
them to take effect.
4.4.3 Biquad design software
Following are programs that can be used to design your biquad coefficients.
4.4.3.1 Biquad calculation spreadsheet
The community-developed biquad calculation spreadsheet allows many filter types to be calculated, including
notch filters, Linkwitz transforms, and filters with arbitrary Q-factor. Access this spreadsheet here (requires
Microsoft Excel):
http://www.minidsp.com/images/fbfiles/files/All_digital_coefs_v1-20101026.zip
4.4.3.2 Room EQ Wizard (REW)
Room EQ Wizard is a free acoustic measurement and analysis tool, available for Windows, Mac and Linux
platforms. It includes the ability to automatically generate a bank of parametric EQ biquads based on a
measurement. These coefficients can be saved to a file from REW and loaded directly into a PEQ bank in a
miniDSP plugin. Room EQ Wizard can be downloaded here:
http://www.roomeqwizard.com/#downloads
For guidance on using this feature, please refer to the app note Auto EQ with REW.
4.4.3.3 Active Crossover Designer (ACD)
Active Crossover Designer (ACD) by Charlie Laub performs the complete set of functions for active crossover
design and generates biquad coefficients as its output. Download it here (requires Microsoft Excel):
http://audio.claub.net/software/ACD/ACD.html
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4.5 WORKING WITH CONFIGURATIONS
The data that controls the audio processing is called a configuration. The processor stores four configuration
presets in its internal memory, which can then be selected from the wired remote panel or via infrared remote.
4.5.1 Online and offline mode
Initially, the plugin is in offline mode. When the Connect&Synchronize button is used, the plugin downloads
configuration data into the processor and goes into online mode. Changes made in the plugin user interface
therefore fall into two categories:
The plugin is in online mode
The plugin user interface is “live” – that is, any changes made to the audio processing
parameters in the user interface are immediately downloaded to the processor. The effect of
these changes will thus be audible as the changes are made.
The plugin is in offline mode
Changes made to audio processing parameters in the plugin user interface will be made locally
only. The next time the plugin is synchronized to the processor, the parameters will be
downloaded to the processor (as long as the Synchronize Config button is selected).
The configuration contained in the miniDSP hardware unit cannot be uploaded back to the
computer. Therefore, you must save your configuration to a file if you wish to recover from any
changes you make while in offline mode.
4.5.2 Selecting a configuration
The active configuration is selected by one of the four buttons in the Configuration Selection area. By default,
configuration 1 is selected:
To switch to a different configuration, click on a different button. There are two cases:
The plugin is in online mode
Audio processing will switch to the parameters contained in the selected configuration. If,
however, parameters of the newly selected configuration have been changed since the last that
particular configuration was synchronized to the processor, then a dialog will appear asking you
if you want to synchronize the configuration.
The plugin is in offline mode
The user interface will update to show the parameters of the newly selected configuration. If
this configuration is changed in the user interface, it will be downloaded to the processor the
next time it is synchronized.
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4.5.3 Saving and loading configurations
Configurations can be saved to and loaded from files. Each configuration is stored in a separate file. It is very
strongly recommended that each configuration programmed into the processor be saved to a file, to ensure that
the configuration is not lost if the processor is inadvertently reset.
To save the currently selected configuration to a file, drop down the File menu, then select Save and then Save
current configuration. In the file box, select a location and name of the file, and save it.
To load a configuration, first select the configuration preset that you wish to load into. Then drop down the File
menu, select Load, and then Load configuration to current slot.
If the plugin is in online mode, the new configuration data will be downloaded to the processor immediately. If
the plugin is in offline mode, the configuration will be loaded into the user interface only, and will be
downloaded to the processor the next time it is synchronized.
To copy a configuration from one preset to another, save the configuration to a file, then select
a different configuration preset and load the file.
4.5.4 Loading configurations from microSD card
The C-DSP 6x8 can load a set of configurations from a microSD card. This can be used to load new configuration
sets without requiring a computer connection.
1. Connect a microSD card to the computer. If the computer has an SD card slot, you can use a microSD
card adapter. Or, use an external card reader connected via USB. If the card hasn't previously been
formatted, format in FAT format.
2. Start the plugin. Don't connect or synchronize to the C-DSP 6x8. From the File menu, select Save and
then Save all configuration to SD card.
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3. From the file save dialog box that opens, type in a file name, navigate to the SD card and click on Save.
4. Eject the (micro) SD card from the computer.
5. Power off the C-DSP 6x8. Insert the microSD card into the slot. (It pushes in and latches.) Power on the
C-DSP 6x8.
6. The C-DSP will load all four configurations. Each button on the wired remote will light as that
configuration is loaded.
7. Eject the microSD card. (Push it in gently to unlatch it, then pull it out.) The C-DSP 6x8 is ready for use
with a new configuration set.
4.5.5 Restoring to defaults
Configurations can be reset to the factory defaults from the Restore menu. There are two options:
Factory Default
Reset all four configuration presets to the factory default settings.
Current Configuration Only
Reset only the currently selected configuration preset to the factory default settings.
If the plugin is in online mode, the configuration data on the processor (all or just one configuration, as selected)
will also be reset to factory defaults. Otherwise, the reset will take place in the user interface only, and the new
configuration data will be downloaded to the processor next time it is synchronized.
4.6 KEYBOARD SHORTCUTS
The C-DSP 6x8 plugin supports the use of the keyboard for many operations.
Tab
The Tab key moves the focus from the current user interface element to the next. A blue-grey
surrounding box usually indicates the user interface element with the focus. Shift-Tab moves the
focus in the opposite direction.
Up/down arrows
The up/down arrow keys (and in some cases, the left/right arrow keys) adjust the value of many
parameters, if they have the focus:
Output channel gain
Crossover frequency and filter type
PEQ filter frequency, gain, and Q
Space
The Space bar toggles buttons that have two states, such as Bypass, Invert, and Mute, if they
have the focus.
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5 USING THE C-DSP 6X8
Once configuration is complete, the computer is not required and can be disconnected. The wired remote
and/or an infrared remote can be used to control:
Master volume
Master mute
Preset selection
5.1 STATUS INDICATORS
The currently selected preset is indicated by a blue LED in one of the selection buttons.
5.2 CONTROLS
To change the volume
Rotate the control knob clockwise to increase the volume, and counter-clockwise to decrease it.
The LED bar graph on the left indicates the master volume level setting.
To mute and unmute
Press on the control knob.
To change the preset
Press one of the four buttons. The LED of the selected preset will flash several times. When it
stays lit, the selected preset in now in operation.
The preset cannot be changed from the wired remote while there is a USB connection to the
computer. To change presets while connected via USB, connect via the plugin and use the Config
selectors.
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5.3 INFRARED REMOTE CONTROL
Many standard and programmable remote control units can be used with the C-DSP 6x8. Rather than make you
acquire yet another remote, the C-DSP 6x8 can “learn” the control codes of your current remote if it supports
one of the following remote control codes:
NEC
Sony
Philips RC6
To initiate the learning process, drop down the IR Remote menu and select IR learning. Click on the Learn
button for an operation, and then press the desired button on the remote control. If the code is accepted, the
status will change to show a tick.
This screenshot shows the IR learning screen:
To "unlearn" a command, press the Learn button and wait for the plugin to time out.
The preset cannot be changed with the infrared remote while there is a USB connection to the
computer. To change presets while connected via USB, connect via the plugin and use the Config
selectors.
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Computer connectivity
Driverless USB 2.0 control interface for Windows and Mac OS X
Analog audio inputs
4 x high level (Terminal Block), Max 8 Vrms
4 x low level unbalanced (RCA) inputs, Max 4 Vrms
Digital audio Input
S/PDIF on RCA connector / Isolated with digital audio transformer
A high quality onboard Asynchronous Sample Rate Converter ensures compatibility
with most sample rates, from 44.1 up to 192 kHz.
Analog audio outputs
8 x outputs on unbalanced (RCA) connectors, 2.0V RMS full scale output
Audio resolution
24-bit input and output, 48 kHz internal sample rate
Audio processing
172MHz, 28/56bit Digital Signal Processor
Storage/presets
All settings controllable in real time from software user interface.
Up to 4 presets stored in local flash memory.
Wired external remote
External remote for control of active preset, master volume and master mute. LED
indication of master volume and active Preset.Provides power and data connection
to the external remote via RJ11 cable.
microSD Card
Allows setup without a laptop: a configuration can be built offline and loaded
automatically to the unit in the car via a microSD Card.
Infrared remote
“Learning remote” capabilities (NEC, Philips, Sony)
Controls master volume, mute, preset selection.
Power supply
Isolated DC-DC conversion for Car Audio environment
Dimensions (H x W x D)
41 x 205 x 122 mm
6 ADDITIONAL INFORMATION
6.1 SPECIFICATIONS
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Item#
Symptoms
Troubleshooting recommendation
1
Cannot install software
a. Confirm that you downloaded and installed the required
frameworks first (see Software Installation).
2
Software running in
background but not
showing
a. The Adobe Air environment may need a network connection
the first time you run a plugin. Close the plugin program,
ensure that your computer has a network connection, and
restart the plugin.
b. The Adobe Air environment may require a version update.
Download the latest version from http://get.adobe.com/air/.
3
Cannot connect to the
board by USB
a. Reset the processor by power-cycling the unit.
b. Make sure the processor is seen in the device manager as a
HID device.
4
No audio or low audio on
outputs
a. Check the cabling from the processor to your amplifiers.
b. Check that your amplifiers are turned on and that any volume
controls are turned up.
c. Check that the input meters and output meters are showing
adequate signal (if not, see item 5).
d. Check that master mute is not enabled.
e. Check that the mute buttons in the output control blocks are
not enabled.
f. Check that your crossover frequencies are correct e.g. that
you don’t have high pass and low pass frequencies incorrectly
set.
g. Check that the matrix mixer is sending the correct inputs to
the correct outputs.
5
No signal showing on input
meters
a. Check the cabling from your source/s.
b. Check that your source is playing audio and that it is not
muted or have volume control turned down.
c. Check that the plugin is synchronized with the hardware unit.
6
Audio sounds distorted
a. Check the input meters and ensure that you are not
overloading the inputs. If necessary, reduce the signal level
from the source or change the input sensitivity jumpers.
b. Check the output meter and ensure that you are not
overloading the outputs. If necessary, reduce the output gain
6.2 TROUBLESHOOTING
The following table lists the most common causes of issues. If following this table does not provide a solution,
see Obtaining Support below.
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and/or the amount of boost in the EQ blocks.
6
Audio is coming through
the wrong outputs
a. Check the cabling from the processor to your amplifiers.
b. Check the cabling from your source/s.
c. Check that you have correctly set up the matrix mixer to send
the correct inputs to the correct outputs.
7
Cannot reload a
configuration
a. Confirm the file format of your file (.xml).
b. Confirm the version of the file.
6.3 MCU FIRMWARE UPDATE
miniDSP may periodically provide an update to the C-DSP 6x8 MCU firmware to enable new features. The most
recent MCU firmware is always included in the installation folder of the plug-in download. To update the
firmware:
1. Connect a microSD card to the computer and copy the .hex firmware file onto it. The card will need to
have been formatted in FAT format.
2. Power off the C-DSP 6x8. Insert the microSD card into the slot. (It pushes in and latches.) Power on the
C-DSP 6x8.
3. The C-DSP will load new firmware.
4. Eject the microSD card. (Push it in gently to unlatch it, then pull it out.) The C-DSP 6x8 is ready for use
with new firmware.
6.4 OBTAINING SUPPORT
1. Check the forums on miniDSP.com to see if this issue has already been raised and a solution provided.
2. Contact miniDSP via the support portal at minidsp.desk.com with:
a. The specific product you are having an issue with (in this case, C-DSP 6x8).
b. A clear explanation of the symptoms you are seeing.
c. A description of troubleshooting steps (see Troubleshooting above) performed and your results.
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