4Channel DSP
Author: Bogen
Description: Nyquist

Compressor

A compressor reduces the dynamic range of a signal. This effect is perceived as quieting loud sounds and boosting quiet sounds.

Figure 1. Compressor Settings

To adjust the compressor settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Compressor.

4​Make desired adjustments using the controls described in Table 13, “Compressor Settings,” on page 28.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

5​Select Enable to apply the settings to the selected channel.

Table 13. Compressor Settings

Enable | Enables or disables the compressor DSP effect for this channel.
Threshold | Sets the threshold level, which is the point where the signal activates the compressor circuit. The range is −135 to +21 dB.
Attack | Sets how quickly or slowly compression will be applied to the signal once the audio signal goes above the threshold level. It specifies the length of time over which the compression ratio will gradually increase from no compression to full compression. The range is 1 to 500 ms.
Hold | Sets how long compression will be applied after the signal has fallen below the threshold. The range is 1 to 500 ms.
Decay | Sets how quickly or slowly compression will be removed from the signal after the signal has dropped below the threshold and the Hold interval has expired. It specifies the length of time over which the compression ratio will gradually decrease from full compression to no compression. The range is 0 to 2000 ms.
Knee | Sets how far below the threshold compression will begin to be gradually applied to the signal. A very low value, known as a hard knee, immediately applies full compression once the threshold is reached. A high value, known as a soft knee, will gradually start applying compression before the signal reaches the threshold, not reaching the full effect until the threshold is reached, thereby “rounding off” the compression effect. Increasing the knee level decreases the obvious transition from the uncompressed to the compressed sound. The range is 1 to 100 dB.
Ratio | Sets the compression ratio to be applied to the signal. For example, if the ratio is set for 6 (6:1), the input signal must increase by 6 dB for the output level to increase by 1 dB. The range is 1 to 100.
Input meter | Shows the strength of the input signal.
Output meter | Shows the strength of the output signal, providing a visual indicator of the effect of the compressor on the output signal.
Comp LED | Illuminates when compression is being applied to the signal.

Delay

A delay effect causes the signal to be delayed by a configurable time interval from 0 to 30 milliseconds. This can be useful for synchronizing playback between different channels which, for various reasons, may be playing out-of-sync.

To adjust the Delay settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Delay.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Make desired adjustments using the controls described in Table 14, “Delay Settings,” on page 30.

Table 14. Delay Settings

Delay (ms) | Sets the number of milliseconds by which the input signal will be delayed before sending it to the output channel.
Signal LED | Illuminates when the input signal is present.
Clip LED | Illuminates when the input signal is clipping.
Input meter | Indicates the strength of the input signal.

Graphic EQ

The graphic equalizer allows you to tailor the audio signal to optimize the frequency response of the sound system.

The graphic equalizer parameters are set per channel.

Figure 3. Graphic EQ Settings

To adjust the graphic equalizer settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Graphic EQ.
The Graphic EQ provides 16 slider knobs that can be moved between +12 dB and −12 dB. The frequency of each slider is different and range from 25 Hz to 20,000 (20k) Hz. By default, each knob is set at 0 dB, which means that no frequencies are being boosted or cut.

Note: For the best results, frequencies should be cut only. Boosting frequencies to compensate for room dimensions or speaker response deficiencies usually results in a loss of headroom in the signal chain.

4​Adjust frequencies as desired, ensuring the Enable LEDs are green for the selected frequencies.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

High/Low Pass

High-pass filters allow signals that are higher than the specified frequency and attenuate signals that are lower. Low-pass filters allow signals that are lower than the specified frequency and attenuate signals that are higher. When combined, they are known as a band-pass filter. Band-pass filters can be used to tailor the frequency response of a microphone exclusively for vocals, which can be very useful in a noisy environment to filter out the higher and lower frequencies that could mask the human vocal range during announcements.

You can specify the range of frequencies that will pass through the high-pass and low-pass filters and select the type of filter that is used through the channel’s High/Low Pass drop-down menu option.

Figure 4. High/Low Pass Parameters

To adjust the high/low pass parameters for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select High/Low Pass.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Set the parameters described in the following table:

Table 15. High/Low Pass Parameters

High-Pass (Low Cut) This feature helps eliminate low-frequency noise (signals of 100 Hz and below, such as background rumble from ventilation systems, etc.) and is used primarily with microphone-level input. It is particularly effective when handheld microphones are used.
Enable | Enables or disables the High-Pass filter.
Frequency | Set the cutoff frequency. You can adjust the frequency by moving the knob (click and move up or down) or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 Hz to 20,000 Hz can be entered. The high-pass filter attenuates content below this frequency and lets frequencies above this cutoff frequency pass through the filter.
Type | Available filter types are: Linkwitz-Riley (12, 24, 36, and 48 dB per octave) Butterworth (6, 12, 18, 24, 30, 36, 42, and 48 dB per octave) Bessel (12, 18, and 24 dB per octave) Note: The term “dB per octave” describes how steeply frequencies below the selected cutoff frequency are attenuated. For example, if the cutoff frequency is 100 Hz and the filter type specifies 12 dB per octave, a 50-Hz signal (i.e., one octave lower) will be attenuated by 12 dB and a 25-Hz signal (i.e., two octaves lower) will be attenuated by an additional 12 dB.
Low-Pass (High Cut) This feature helps eliminate high-frequency noise (signals of 8000 Hz and above) such as background hiss and sibilance (excessive "S" in vocals, etc.) and is used primarily with microphone-level input. It is particularly effective when handheld microphones are used.
Enable | Enables or disables the Low-Pass filter.
Frequency | Set the cutoff frequency. You can adjust the frequencies by moving the knob (click and move up or down) or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 Hz to 20,000 Hz can be entered. The low-pass filter attenuates content above this frequency and lets frequencies below this cutoff frequency pass through the filter.
Type | Available filter types are: Linkwitz-Riley (12, 24, 36, and 48 dB per octave) Butterworth (6, 12, 18, 24, 30, 36, 42, and 48 dB per octave) Bessel (12, 18, and 24 dB per octave) Note: The term “dB per octave” describes how steeply frequencies above the selected cutoff frequency are attenuated. For example, if the cutoff frequency is 8,000 Hz and the filter type specifies 12 dB per octave, a 16,000-Hz signal (i.e., one octave higher) will be attenuated by 12 dB and a 32,000-Hz signal (i.e., two octaves higher) will be attenuated by an additional 12 dB.

Limiter

A limiter is a compressor with a high slope (i.e., attack) that is used to prevent a signal from exceeding a set decibel level. Limiters are used as safeguards against signal clipping.

Limiter parameters are set per channel.

Figure 5. Limiter Settings

To adjust the limiter settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel or select the Menu button for the Output.

3​From the drop-down menu, select Limiter.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust the following settings as needed:

Table 16. Limiter Settings

Threshold | Sets the signal level at which the limiter is triggered. Any signal exceeding this threshold will be compressed to this level. The range is −24 to +24 dB.
Decay | Sets the rate for turn off of the limiter after the signal is below the threshold. Decay range is 5 to 2300 milliseconds.
RMSTC (Root Mean Square Time Constant) | Sets how fast the limiter reacts to a signal that has exceeded the threshold. RMSTC range is 50 to 10000 dB/sec.

Noise Gate

A noise gate controls the volume of an audio signal by attenuating the signal when it registers below the threshold. This is typically used to eliminate or minimize background noise.

Figure 6. Noise Gate Settings

To adjust the noise gate settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Noise Gate.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust the following settings as needed:

Table 17. Noise Gate Settings

Enable | Enables or disables the noise gate DSP effect for this channel.
Threshold | Sets the minimum threshold level that the signal must reach for the noise gate to “open,” allowing the signal to be sent to the output channel. Threshold range is −135 to +21 dB.
Attack | Sets how long it takes for the gate to open once the signal reaches the threshold level. Attack range is 1 to 500 ms.
Hold | Sets the length of time the gate will stay fully open after the signal reaches the threshold level. Hold range is 1 to 500 ms.
Decay | Sets hows quickly or slowly the gate will close once the signal has dropped below the threshold level and the Hold interval has expired. Decay range is 0 to 2000 ms.

Parametric EQ

A parametric equalizer is a multi-band variable equalizer that allows control of frequency amplitude (boost/cut), center frequency, and frequency bandwidth, or Q.

Figure 7. Parametric Equalizer Settings

The parametric equalizer settings for your device allows you to adjust the Q and gain for seven separate frequencies, which then become plot points on the screen’s graph.

To adjust the parametric equalizer settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Parametric EQ.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust frequencies as desired, ensuring the Enable LEDs are green for each selected frequency. You can adjust the frequencies by moving the Freq knob or by double-clicking the knob and typing the frequency. When typing the frequency, only numeric values from 20 to 20,000 can be entered.

5​Make desired Q adjustments by adjusting knob (or double-clicking and typing the desired adjustment). Q can be from 0.1 to 20 and sets how wide to either side of the selected frequency the adjacent frequencies are affected.

Q is the Quality or Quality Factor, which refers to the bandwidth of one band of a parametric equalizer. Q is calculated by dividing the center frequency in Hz by the width of the boost or cut zone, +3 dB or −3 dB above or below 0 dB.

6​For each frequency, use the Gain knob or double-click the knob and type the gain to either boost (turn up) or cut (turn down).

Gain knobs can be moved between +12 or −12 dB. By default, each knob is set at 0 dB, which means that no frequencies are being boosted or cut.

7​Select Save Settings to Server.

Peak Limiter

The primary purpose of the Peak Limiter is to eliminate very high signals, which can not only create unpleasantly loud sound, but potentially cause mechanical damage to the speaker. Any signal that exceeds the threshold will be compressed, thereby reducing the signal.

This type of limiter is triggered by the peak, or loudest part, of a signal, not the overall strength or volume. This means it can be triggered any time the signal exceeds the specified threshold, however briefly. This is in contrast to the RMS Limiter, which is triggered by a signal whose level exceeds the threshold over a period of time.

The primary purpose of the Peak Limiter is not typically to shape or enhance the audio signal, but to limit any (hopefully uncommon) signals that exceed the mechanical tolerance levels of the speakers.

Tip:​The Presets feature contains predefined Peak Limiter settings for a number of specific speakers.

To adjust the Peak Limiter settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Peak Limiter.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Make desired adjustments using the controls described in Table 18, “Peak Limiter Settings,” on page 37.

5​Select Enable to apply the settings to the selected channel.

Table 18. Peak Limiter Settings

Enable | Enables or disables the Peak Limiter DSP effect for this channel.
Threshold | Sets the threshold level, which is the point where the signal activates the compressor circuit. The range is −135 to +21 dB.
Attack | Sets how quickly or slowly compression will be applied to the signal once the audio signal goes above the threshold level. It specifies the length of time over which the compression ratio will gradually increase from no compression to full compression. The range is 1 to 500 ms.
Hold | Sets how long compression will be applied after the signal has fallen below the threshold. The range is 1 to 500 ms.
Decay | Sets how quickly or slowly compression will be removed from the signal after the signal has dropped below the threshold and the Hold interval has expired. It specifies the length of time over which the compression ratio will gradually decrease from full compression to no compression. The range is 0 to 2000 ms.
Input meter | Shows the strength of the input signal.
Output meter | Shows the strength of the output signal, providing a visual indicator of the effect of the compressor on the output signal.
Limiting LED | Illuminates when compression is being applied to the signal.

Presets

The DSP configuration settings for a channel can be stored as a DSP preset. A DSP preset stores the settings for the DSP preset effects: Hi/Low Pass Filter, Peak Limiter, RMS Limiter, and Parametric EQ. When a DSP preset is applied to a channel, the settings of the DSP preset effects are replaced with the settings in the preset. Presets can also be exported or imported to or from (JSON-encoded) files, which allows them to be backed up or shared between devices.

Bogen has provided a number of predefined DSP presets. These configurations are defined and optimized for specific speakers.

DSP presets can be selected and applied to each individual channel. Selecting a preset will apply the predefined settings for that channel, potentially overwriting any existing settings. If any of those settings are later modified by the user, the existing preset will be unselected, but all other settings from the preset will remain. To completely remove the preset configuration from a channel, click the Clear button, which returns the DSP preset effect settings to their default values for the selected channel.

Note: To completely remove an uploaded preset from the list, the Firmware Update view has a Restore Factory Settings option, which will clear out all custom presets along with all other configuration settings. Use this feature with caution.

To adjust the Presets settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Presets.

4​Make desired adjustments using the controls described in Table 19, “Preset Settings,” on page 39.

Table 19. Preset Settings

Ch A/Ch B/Ch C/Ch D | Select a predefined DSP preset configuration from the list of options for Channels A, B, C, and D. These configurations will be applied when the Apply button is clicked. Note: This field will be blank if no preset has been selected for this channel. To deselect an existing preset, click Clear. Selecting the blank entry has no effect.
Details | Displays the name and description of the preset, as well as an optional link to a web page related to the preset (if available).
Generate | Prompts the user to specify a new name and stores the current settings of the DSP preset effects (Hi/Low Pass Filter, Peak Limiter, RMS Limiter, and Parametric EQ) under that name. Valid characters: A–Z, a–z, 0–9, - (hyphen), and _ (underscore).
Download | Downloads the selected preset configuration (as a JSON file) to the user’s local computer.
Clear | Deselects the currently selected preset configuration and returns the DSP preset effect settings for the channel to their default values. Note that these changes take effect immediately, without having to click Apply.
Upload Presets | Prompts the user to select one or more preset configuration files from the local computer. These files must contain JSON-encoded DSP preset configurations that were previously downloaded or provided by Bogen technical support. Once uploaded, the new DSP preset configurations will be available for use.
Apply | Applies the selected preset configurations to the DSP channels.

RMS Limiter

The primary purpose of the RMS Limiter is to protect the speakers from the thermal damage that can be caused by extended periods of excessive power usage. Any signal whose RMS level exceeds the threshold will be compressed, thereby reducing the signal.

The RMS Limiter uses the RMS (root mean square) level, which is proportional to the average amount of energy over a short period of time, to determine when a signal has met the threshold. Because the RMS level is more closely related to the perceived volume of a signal than the peak level, this type of limiter is less sensitive to extremely short signal peaks, and more sensitive to the overall volume of a signal. This is opposed to the Peak Limiter, which is triggered by any signal that exceeds the threshold, however briefly.

To adjust the RMS Limiter settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select RMS Limiter.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Make desired adjustments using the controls described in Table 20, “RMS Limiter Settings,” on page 40.

5​Select Enable to apply the settings to the selected channel.

Table 20. RMS Limiter Settings

Enable | Enables or disables the RMS Limiter DSP effect for this channel.
Threshold | Sets the threshold level, which is the RMS level above which the signal will activate the compressor circuit. The range is −135 to +21 dB.
Attack | Sets how quickly or slowly compression will be applied to the signal once the audio signal goes above the threshold level. It specifies the length of time over which the compression ratio will gradually increase from no compression to full compression. The range is 1 to 500 ms.
Hold | Sets how long compression will be applied after the signal has fallen below the threshold. The range is 1 to 500 ms.
Decay | Sets how quickly or slowly compression will be removed from the signal after the signal has dropped below the threshold and the Hold interval has expired. It specifies the length of time over which the compression ratio will gradually decrease from full compression to no compression. The range is 0 to 2000 ms.
Input meter | Shows the strength of the input signal.
Output meter | Shows the strength of the output signal, providing a visual indicator of the effect of the compressor on the output signal.
Limiting LED | Illuminates when compression is being applied to the signal.

Router

Router settings allow you to specify where to output a line input signal and how much to adjust its level. For each input, you can:

Adjust the Analog Input Gain. This adjusts the electronic gain for the input signal.

Enable or disable the input.

Adjust the Input Gain. This adjusts the digital gain for the input.

Route the input to one or more output channels.

Adjust the gain per output channel.

For each output channel, you can:

Enable or disable the output channel.

Adjust the overall output gain, which includes all of the input signals that are routed to that output channel.

Figure 11. Router

Note: The number of output channels that appear on the Router screen depends on whether the output channels are configured for Bridged or 2-Channel mode. For example, if Channels A and B are in Bridged mode, then three output channels appear: A, C, and D. If Channels C and D are also in Bridged mode, then only two output channels would appear on the Router screen: A and C.

To adjust the router settings:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for any channel.

3​From the drop-down menu, select Router.

4​Enable the desired Inputs (green).

5​Enable the desired Outputs (blue).

6​Enable the output channels to which each input is to be routed (gray).

7​Adjust the Analog Input Gain for each desired channel to ensure a strong input signal is being received.

Tip:​You may have to switch between the Router and mixing board views of the DSP page to view the input VU meters, Line-In LEDs, and Clip LEDs while adjusting the input gains.

8​Adjust the digital input, output, and routed channel gains as desired.

Settings

You can specify custom names and colors for each of the mixing board channels. Note that the number of channels that appear can range from two to four, depending on whether channels are configured for mono or single channel bridge mode.

Figure 12. Settings Parameters for 4-Channel Mono

For example, if channels A and B and channels C and D have been placed in Single Channel Bridged Mode, then only two channels appear.

To adjust the settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Settings.

4​For each channel, type the name that you want to display for the channel.

5​For each channel, select a color that will be used to highlight the channel.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

6​Select Save.

Signal Present

You can configure the threshold level that a signal must reach before the signal LED is lit, as well as how long the LED will remain lit. You can configure this for each channel.

Figure 13. Signal Present Parameters

To adjust the Signal Present settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Signal Present.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Adjust the following settings as needed.

Table 21. Signal Present Parameters

Threshold | Sets the minimum level the signal must reach before the signal LED is illuminated. Threshold range is −144 to +24 dB.
Hold | Sets the minimum number of milliseconds that the signal LED will remain illuminated. Hold range is 2 to 200 milliseconds.

Standby

The amplifier can automatically be put into a low-power Standby mode if the signal falls below a specified threshold level for 200 seconds or longer. This can be enabled and the threshold level set via the Standby settings. When a signal is received that exceeds the specified threshold, the amplifier will automatically recover from standby mode.

Caution​There may be up to a one second latency for the amplifier to recover from standby mode, which could cause the beginning of the audio signal to be lost. For this reason, it may be a good idea to include a second or more of “comfort noise” at the beginning of the signal to mitigate this effect, or if necessary, to disable this feature.

To adjust the Standby settings for a channel:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Standby.

Note: If you want to return to the factory settings, select the Reset icon that appears in the right corner.

4​Make desired adjustments using the controls described in Table 22, “Standby Settings,” on page 44.

5​Select Enable to use the Standby feature with the defined levels.

Table 22. Standby Settings

Enable | Enables or disables the standby feature for the amplifier.
Threshold Channel AB and Threshold Channel CD | Sets the threshold level for channels A/B and for channels C/D. If the signal level remains below this level for 200 seconds or longer, the amplifier is put into low power Standby mode. Normal operation will resume (within one second) once a signal is received that exceeds this level. The range is −144 to +24 dB.
Status | Indicates if channels A/B and C/D are in Standby mode (On) or not (Off).

Status

The Status selection for the power amplifier provides real-time status, such as whether the amplifier is operating in 2-channel mono or single-channel bridged mode, LEDs for thermal protection and clipping, a real-time reading of the appliance’s temperature, and indicators of the amplifier’s standby and mute status. Note that the number of channels that appear depends on whether the amplifier is operating in 2-channel mono or single-channel bridged mode.

Figure 15. Status for 2-Channel

Figure 16. Status When All Channels Are Bridged

To view status for the power amplifier:

1​On the appliance Web UI’s main page, select DSP.

2​Select the Menu button for the channel.

3​From the drop-down menu, select Status.
The view-only information that appears is described in the following table:

Table 23. Status

Switch Position | Indicates the position of the Amplifier Mode switch located on the rear of the appliance. Bridged mode is typically used when higher-power, single-channel operation with a high-impedance loudspeaker load is needed. For information about setting the Amplifier Mode, refer to the installation manual for the appliance.
Thermal Protect | Appears red if the output channel is being overloaded or there is an external short and the amplifier has placed itself into protection mode to prevent permanent damage. Otherwise, the LED is green.
Channel A/B/C/D Output Limit | Appears red if the output signal is too high and is being clipped or distorted. Otherwise, the LED is green.
Temperature | Provides the real-time temperature of the appliance in both Celsius and Fahrenheit. The amplifier enters protection mode if the temperature exceeds 85 °C.
Standby | Indicates if channels A/B and C/D are in Standby mode (On) or not (Off).
Mute | Indicates if channels A/B and C/D are in Mute mode (On) or not (Off).