The miniDSP Flex HTx has a range of input sources and output connections. This section provides an overview of the basics so you can quickly get started with playing audio.
Ensure all equipment is powered off when making audio connections.
The diagram below shows the audio sources that can be connected to the miniDSP Flex HTx. The USB and HDMI eARC inputs accept multichannel linear PCM audio (8 channels), while the SPDIF and TOSLINK inputs accept stereo audio only. For more about HDMI and eARC, see the HDMI audio page.
The SPDIF and TOSLINK inputs accept stereo PCM audio only. They will not decode bitstream audio.
Connecting an amplifier and speakers¶
The diagram below illustrates a basic connection of a multichannel amplifier, speakers and subwoofer to the miniDSP Flex HTx. The default settings of the Flex HTx route the input channels to all output channels with no bass management or crossovers active.
For a typical home theater system, bass management will need to be set up.
Before playing audio for the first time, turn the volume down using the front panel encoder. Increase it gradually after audio playback starts.
LFE channel gain¶
The LFE channel of movie soundtracks is recorded 10 dB lower than the speaker channels, so that the higher signal levels required do not overload the recording medium. This 10 dB must be regained in the playback chain.
There are several elements to accomplishing this effectively with the Flex HTx:
- Higher playback gain in the LFE/Sub channel
- Calibration for 10 dB higher Sub output
- 10 dB adjustment when mixing channels in bass management
- Adjusting the Sub channel gain before and after Dirac Live calibration
"LFE" refers to the source channel containing low-frequency effects. "Sub" or "Subwoofer" refers to the output channel that drives the subwoofer. When there is no bass management, they are used interchangeably. However when bass management is used, the Sub (output) channel includes both the LFE channel and low-frequency content from the speaker channels.
Sufficient Sub channel gain¶
Set the gain on your subwoofer to maximum to ensure that there is sufficient analog gain on this channel. (Note: this refers to your actual subwoofer, not the Sub output channel of the Flex HTx). Otherwise, you run the risk of digital clipping on the Sub channel output.
Use REW to run measurement sweeps on each channel. Adjust the output channel level or subwoofer gain so that the LFE channel measures 10 dB higher, as shown here:
When the low frequencies of a speaker channel are mixed to the LFE channel, the speaker channel must be reduced 10 dB in order for the relative levels to be correct. The Flex HTx provides this with the Reduce 10 dB toggle on the LFE Management tab.
After bass management is set up, the channels should look like this:
Dirac Live gain adjustments¶
When Dirac Live calibrates, it will lower the level of the Sub channel to match the speakers. This is not desired. Therefore, we recommend this procedure:
- Reduce the output level of the Sub channel by 10 dB.
- Run the Dirac Live calibration.
- Raise the output level of the Sub channel by 10 dB.
Confirm that the levels are as expected by running a measurement with REW.
About USB Audio¶
The miniDSP Flex HTx accepts multichannel (8-channel) PCM audio over USB at sample rates of 44.1, 48, 88.2, 96, 176.4, and 192 kHz. The same USB connector is used for playing USB Audio as well as for configuration and Dirac Live calibration.
To play USB Audio from a computer, use the supplied cable to connect the USB 2.0 (Type B) port of the miniDSP Flex HTx to a free USB port on your computer.
Alternatively, connect a network streamer to the USB port. For examples using the Raspberry Pi, see these application notes on our website:
The miniDSP Flex HTx is USB Audio compliant, so no drivers need to be installed to play audio on macOS. Open Audio MIDI Setup (in Applications->Utilities) and click on its name in the list on the left-hand side.
Set sample rate¶
Click on the selector next to Format to bring up the sample rate and bit depth selector. Sample rates up to 192 kHz can be selected:
Default audio device¶
To set the miniDSP Flex HTx as the default audio output device, right-click and select "Use this device for sound output":
Note that individual audio playback apps may allow the miniDSP Flex HTx to be selected for audio output independently of the system default. They may also control sample rate automatically.
Note: to play USB audio from Windows, the miniDSP UAC2 driver package must be installed first.
Default audio device¶
To set the miniDSP Flex HTx as the default audio output device, open the Settings app and navigate to the System → Sound page. Select the Flex HTx with the radio button:
Set sample rate¶
To change the bit depth and sample rate, click on the rightward angle symbol >. Click the selector next to Format to pop up the sample rate menu. Sample rates up to 192 kHz can be selected:
If your audio application supports ASIO® audio drivers, we recommend selecting the miniDSP ASIO Driver in its settings. This typically allows the application to automatically change sample rate. For example, in JRiver Media Center:
miniDSP UAC2 control panel¶
The current settings of the miniDSP Flex HTx can be viewed by opening the miniDSP UAC2 Control Panel from the Windows Start menu (under the miniDSP Ltd folder). This control panel allows you to view current settings. In addition, it can be used to set buffer size, although we recommend that you leave this setting at the default. If you are having an issue with inadequate output volume over USB playback, check the Volume tab.
To see the installed version of the UAC2 driver, use the About tab: