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The miniDSP SHD includes not only Dirac Live® but also a full set of crossover functions on its four output channels. One use of this is as a flexible tool for integrating subwoofers into your system along with Dirac Live.

Note: This application note requires the use of Room EQ Wizard (REW) to measure the speakers and subwoofer and to generate correction filters for the sub. If you are not familiar with REW, refer to the following application notes:

To integrate a subwoofer without using REW, instead use the procedure in the User Manual, which uses only the Dirac Live app.

Getting connected[Top]

Connect the system as shown in this diagram:

SHD subwoofer integration - system connections

Start the SHD plugin and click the Connect button. Use the Outputs tab to change the displayed labels on the output channels. In the example below, we have used "Left Sp", "Right Sp" and "Sub". Then set up the Routing matrix like this:

SHD subwoofer integration - routing matrix

1. Decide where to put the sub[Top]

The location of the subwoofer can make a big difference. If you can, move the subwoofer to a few different locations and measure it. To measure the sub:

  1. Mute the speaker channels (channels 1 and 2).

  2. Bypass the subwoofer low pass crossover filter (the Xover block of channel 3).

Figure 1 shows the measurements we obtained with a subwoofer in two different locations. For this example, we chose the one in green despite the notches in the response, because it has more output down low. Each room is different and you will need to experiment in your own room to find the best compromise.

Two subwoofer locations

Figure 1. A subwoofer measured in two different locations

2. Equalize the subs[Top]

Use the REW Auto-EQ feature to flatten the subwoofer response around the crossover region. There is no need to try and get the response exactly flat, because Dirac Live will do that correction later. The purpose here is just to get a clean crossover to the speakers.

Figure 2 shows our equalization window in REW. Blue is the target, the darker green curve is the original measurement and the lighter green curve is after EQ. We used one-third octave smoothing.

Equalization of the subwoofer

Figure 2. Equalization of the subwoofer

Here are the key settings we used in REW:

  1. Equalizer: miniDSP 2x4 HD

  2. Target type: Full range speaker

  3. Target level: 72 dB (this will depend on your own measurement)

  4. Match range: 20 to 300 Hz

  5. Allow narrow filters below 200 Hz: Off

3. Enable crossovers[Top]

Click on the Xover button for channel 1. Here you will set a high pass filter to remove low frequencies from the left speaker. For example:

SHD subwoofer integration - high pass filter

Click on the Xover button for channel 3. Set a low pass filter to remove high frequencies from the subwoofer. For example:

SHD subwoofer integration - low pass filter

With the speaker still muted, run a measurement sweep. This will give you the response of the subwoofer with the EQ and low pass filter in place. Now mute the subwoofer, unmute the left speaker, and run another measurement sweep. This will give you the response of the left speaker with the high pass filter in place. Use the Overlays screen in REW to display both measurements.

If necessary, adjust the level of the subwoofer so that it aligns with the speaker near the crossover. You can do this by adjusting the level control on channel 3 and then re-measuring. Figure 3 shows the result we obtained:

Subwoofer with low pass filter and speaker with high pass filter

Figure 3. Subwoofer with low pass filter and speaker with high pass filter

4. Set and adjust time delay[Top]

Set the time delay between the speakers and the sub. As a starting point, use the difference in the distance of the speakers and the sub to the listening position. For example, if the sub is 1 meter further away from the listening position than the speakers, set the delay on the speakers to 2.9 ms:

SHD subwoofer integration - delay on speakers

If the sub is 1 meter closer to the listening position than the speakers, set the delay on the sub to 2.9 ms:

SHD subwoofer integration - delay on sub

Now unmute both the left speaker and the subwoofer and run a measurement sweep. Overlay this new graph with the highpass and low pass measurements from above. You should see that the new measurement has a reasonably smooth transition between the subwoofer and speaker. If it does not (for example, there is a dip at the crossover frequency), then adjust the time delay up or down by 1 or 0.5 ms at a time until you obtain a better result.

Figure 4 shows the result we obtained in mauve. In our case, the speaker was about a meter closer to the microphone than the subwoofer, but we got the best result with a time delay of 1.5 ms on the speakers.

Final integration of speaker and subwoofer

Figure 4. Subwoofer integrated with speaker

5. Check the right channel[Top]

Copy all your settings to the right speaker channel. In the case of the Xover and PEQ blocks, you can do this by using the linking feature:

miniDSP SHD: linking Xover or PEQ

Measure the right speaker and subwoofer together. If the result is not comparable to the left channel, you may need to adjust the time delay and try again. In this case, you will need to find the best compromise between the measurements for the left and right channels.

Note: if you have delay on the speaker channels, they must both be the same – do not set different delays on the left and right speaker channels.

Another method of adjusting the response near the crossover frequency is to change the frequency or the type of high pass filter on the right speaker. This will change the phase relationship between the speakers. Choose the best compromise between the two channels.

6. Run Your Dirac Live Calibration[Top]

You can now run your Dirac Live calibration. Adjust the target curve to suit your preference. For example, this screenshot shows a target curve with an elevated bass level, which many people prefer:

SHD subwoofer integration - after optimization

Multisub integration[Top]

For even better subwoofer integration, two or more subs can be used to reduce the variation in subwoofer frequency response across the listening area. Using two or more subs can also help eliminate or reduce notches in the response such as shown in Figure 1.

A simple approach is to just connect a second subwoofer and follow the procedure described above in this app note again. For more advanced approaches, refer to the following app notes:

Wrapping up[Top]

That's it for this app note! Have fun, and please let us know how you go in our forum.

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Guenter Villnow
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Guenter Villnow
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There are a number of well-regarded music players that can stream audio to the miniDSP SHD Series over your local area network (LAN). In this app note, we will show you how to use BubbleUPnP for Android. You can download it for free, and upgrade it by purchasing a low-cost license.

To begin, in the Volumio interface (e.g. http://minidsp-shd), check that UPnP is enabled. Go to Settings, then My Music, and scroll down to Functionalities Control. If UPNP Renderer is not on, turn it on as shown here:

Enable UPnP on miniDSP SHD

Set the SHD to LAN input:

Select LAN input on miniDSP SHD

On your Android device, install BubbleUPnP from the Play Store. Go to the Now Playing screen of BubbleUPnP and tap on the icon indicated by the red arrow here:

Select miniDSP SHD for UPnP playback

On the overlay, select the miniDSP SHD:

Select miniDSP SHD for UPnP playback

You can now select the source of music by tapping on the dropdown menu at the top left of the screen:

Select source of music playback

If you have a DLNA/UPnP music server on your network, tap on "Select library..." and select it. For this app note, however, we decided to use Qobuz as an example. Tap on "Local and Cloud" and then Qobuz. Log in to your Qobuz account at the prompt:

Log in to Qobuz

You can now navigate through Qobuz:

Navigate Qobuz

Browse to find music that you like:

Navigate Qobuz

Tap on an album and press the triangular play button. Then tap on Now Playing where you can control playback in real time:

Navigate Qobuz

That's it for this app note! Have fun, and please let us know how you go in our forum.

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This app note is a short example of recording multichannel audio on Linux using miniDSP devices.

Please note: miniDSP can't provide support for non-miniDSP hardware and software. In particular, we cannot trouble-shoot Linux-related issues. If you get stuck with Linux and miniDSP hardware, try a simple configuration such as the one we describe here and then proceed from there.

What you will need [Top]

For multichannel recording, you will need one of the following USB interfaces:

  • The USBStreamer (or kit version) supports 8-channel ADAT and 8-channel PCM over I2S (with an additional two channels via TOSLINK).

  • The MCHStreamer supports many different formats, including 8-channel ADAT and 8-channel PCM over I2S (optionally with an additional two channels via TOSLINK or SPDIF), PDM and TDM.

  • The USB microphone array series (UMA-8/UMA-8SP/UMA-16) support multichannel audio for custom beamforming algorithm development

  • The U-DIO8 supports 8 channels of input and output via AES/EBU or SPDIF (BNC).
miniDSP USBStreamer   miniDSP U-DIO8

These devices are all USB Audio class-compliant, so will work on Linux without any driver installation required.

In the case of the MCHStreamer and USBStreamer, the correct firmware must be loaded to configure it for the desired I/O format. For example, for ADAT I/O, load the ADAT firmware. See the relevant user manual for the procedure.

Linux setup and DAW installation [Top]

As a concrete example for this app note, we installed Linux Mint, a user-friendly distribution of Linux, on an Intel NUC. Because of the wide variety of Linux systems, you may need to do things a bit differently depending on the Linux distribution you have installed on your own computer.

For multichannel recording, you will also need a DAW (Digital Audio Workstation) application. For this app note, we installed Ardour. Once the installer is downloaded, open and install it. In Mint, for example, double-click on the downloaded file and then click on the Install Package button.

During the installation process, there were a number of options:

  1. We elected to install Jack (although we didn't use it for this app note).
  2. We chose to enable realtime scheduling:
    Enable realtime scheduling for jackd

Create a project [Top]

First make sure that your miniDSP device is connected to your Linux computer via USB. In the case of the U-DIO8, power it on.

To start Ardour, locate it in the main menu in the Sound & Video section. (Your version of Linux may be different.) When Ardour starts, set the parameters as shown here:

Project setup in Ardour

Note that the miniDSP MCHStreamer is automatically detected and can be selected from the dropdown menus for the Input and Output devices.

On the next screen, enter 8 for "Create Tracks," then click OK:

Create 8 tracks in Ardour

Record audio [Top]

Enable all tracks for recording. This screenshot shows the record enable button for one track:

Enable track recording in Ardour

Then press the main record and play buttons, in that order:

Record buttons in Ardour

Ardour will record all 8 input channels from the MCHStreamer, USBStreamer, or U-DIO8. Here's our screen after recording an 8-channel file over ADAT with an MCHStreamer:

8-channel recording with miniDSP MCHStreamer

You can now proceed to mixdown or export to a file. Have fun, and please let us know how you go in our forum!


 

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In this day and age of  Covid -19 social distancing where public events are cancelled, quite few of us are looking for ways to create immersive content. One way to do so is using a binaural immersive audio experience over headphones. This app note demonstrates the use of ambiMIK-1, a USB microphone featuring four low-noise microphone capsules and integrated preamps, as the perfect fit for an all in one solution for your next livestream concert or 3D audio recording . With the help of Dirac Research's binaural plugin, we will demonstrate how one can setup a powerful system with only few clicks and minimal investment.  For this scenario we'll be using the powerful open source Open Broadcaster Software (OBS) to record and process audio + video.

Please note that OBS is third-party software. miniDSP is not able to directly provide support for this software. For questions or issues specifically related to OBS, please refer to the OBS Forum and its online tutorials.

1. Software installation before you proceed [Top]

Let's list the software you'll need to download and install before you proceed

- Download and install all ambiMIK-1 drivers and Dirac Live Binaural plugin as per the ambiMIK-1 user manual

- Download and install OBS build for your OS. 

- Download and install the OBS ASIO plugin. This plugin will be used to discover the ambiMIK-1 multichannel interface inside your OS. Note that v3 version is based from a 3rd party library that needs to be installed separately (You need to download bassasio.dll from https://www.un4seen.com/bassasio.html.). You can find detailed instructions on the OBS ASIO plugin from here.

- Download and install the VST plugin host for OBS from here.

2. Configuring OBS for the ambiMIK-1[Top]

For OBS to be able to support the 4 ch USB audio interface from the ambiMIK-1, there are few settings to be configured first. To make sure the below steps are running smooth, make sure to connect the ambiMIK-1 to your PC/Mac before going further.

1. Configure OBS as a multichannel stream. Under OBS, go to File -> Settings - > Audio Tab. We'll select 4.0 as the audio configuration.

OBS settings multichannel

Note the general comment that we'll actually only feed 2.0 (binaural) with this configuration. Both Facebook/Youtube will take it as such.

2. Next we'll add the ambiMIK-1 as an ASIO audio input source to OBS. To do so, right click on the Source section of the GUI and select "ASIO Input" as per below.

OBS ASIO input

A dialog box will prompt you to name the source. We'll call it ambiMIK-1 for the purpose of this demo. 

3. Next stage is to configure the ASIO source. We'll select the miniDSP ASIO driver(previously installed) and follow the below example configuration.

ambiMIK asio properties

4. At this stage, the ambiMIK-1  should be live and ready to stream audio as you'll notice from the RMS meters in the Audio Mixer section. Make sure to use the ambiMIK-1 gain utility (see user manual) to modify the internal gain for proper signal as you speak/play music... The yellow section from -20~-10dB is what we'd typically recommend.

ambimik audiomixer

 You're now up and running with the ambiMIK-1 streaming into OBS.  Next stage is to configure the Dirac Live VST plugin so we're converting the ambisonic signal from the 4 mic capsules to a binaural signal one can enjoy with a headphone. 

3. Configure the ambiMIK-1 VST plugin[Top]

The next stage is to load the Dirac ambiSONIC VST plugin inside the VST host.

  1. Right on the ambiMIK-1 under the "Sources" section and select "Filters"

filters

2. Next, we'll add the VST plugin host as a filter by right clicking on the empty selection and click on Add - > VST 2.x plug-in as below.

VST plugin

3. Select the ambiMIK-1 plugin from the list.

VST plugin ambimik

NOTE: if you can't see the miniDSP ambiMIK-1 VST from this list, it's most likely because you didn't copy over the VST files in the correct folder as it will search the plugin in the following folders. Make sure to copy the VST files into one of these folders.

  • Windows (*.dll)
    • C:/Program Files/Steinberg/VstPlugins/
    • C:/Program Files/Common Files/Steinberg/Shared Components/
    • C:/Program Files/Common Files/VST2
    • C:/Program Files/Common Files/VSTPlugins/
    • C:/Program Files/VSTPlugins/
  • macOS (*.vst)
    • /Library/Audio/Plug-Ins/VST/
    • ~/Library/Audio/Plug-ins/VST/

4. The Dirac Research plugin should now be accessible by clicking on the "Open the plugin interface".

VST GUI

Make sure to configure the plugin to binaural audio output. See the ambiMIK-1 manual for other settings you might want to modify.  You can easily confirm that the VST plugin works as it should as only 2 channels will now become active under the Audio Mixer.

VST binaural output

4. Starting OBS streaming/Recording[Top]

- You're now up and running with the Audio side. You'll want to add your webcam or external video sources to the sources of OBS as per the manual of OBS.

- At this stage the steps to start your YouTube/Facebook/Twitch Live stream or recording a local stream will be similar to any stereo content. If you're not familiar with setting up OBS for Youtube/Facebook live, we recommend you follow some of the great step by step guides to get you started knowing this is a common question. Here are some great examples:

How to livestream on Youtube with OBS

How to livestream on Facebook live with OBS

 Make sure to google a bit more for better results.

Wrapping up [Top]

And this is a wrap on yet another interesting applications for the ambiMIK-1. We hope that it will help your future livestream concert, you next 3D immersive audio experience or maybe just learning a bit more about immersive audio!  Have fun and please send us feedback on this article and if you'd like to see more. We look forward to hearing from you!

 


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This app note is a short example of playing back stereo audio from a Linux desktop to a miniDSP device.

Please note: miniDSP can't provide support for non-miniDSP hardware and software. In particular, we cannot trouble-shoot Linux-related issues. If you get stuck with Linux and miniDSP hardware, try a simple configuration such as the one we describe here and then proceed from there.

Basic Linux setup [Top]

We'll assume that you already have a computer running Linux. Since there are so many different Linux distributions ("distros"), it's impossible to give instructions that will work for all of them. We chose a user-friendly distro to use as an example and installed Linux Mint on an Intel NUC.

Photo of miniDSP IL-DSP with Intel NUC

The photo above shows our IL-DSP headphone amplifier, which we've used for the screenshots below. However, all miniDSP devices that support audio playback over USB are class-compliant and so will also work with Linux without any need to install drivers:

Note: this app note describes stereo audio playback to a miniDSP device over USB. However, it's not possible to configure a miniDSP audio device using Linux, as our configuration plugins run on Windows and Mac only.

Install a music player[Top]

For high quality music playback, you'll probably want a dedicated music player. For this app note we installed Strawberry. Download the package that matches your version of Linux from the linked page. The current (as of 2019) version of Linux Mint is based on Ubuntu Bionic, so we downloaded the Ubuntu Bionic installer.

Once the installer is downloaded, open and install it. In Mint, for example, just double-click on the downloaded file. You will probably need to install a few additional packages:

Install the Strawberry music player

Configure playback [Top]

Connect your IL-DSP or other miniDSP device to the Linux computer with a USB cable. Start Strawberry (in Linux Mint, go to the main menu at lower left and then the Sound & Video section.) Drop down the Tools menu and select Settings.

  1. Click on Collection and add your folder containing music files:

    Add folders to the Strawberry library
  2. Click on Backend and select the option "Output to a sound card via ALSA." Then select the miniDSP audio device:

    Add folders to the Strawberry library

    Note that we disabled volume control in the player. This is because we use the volume control in the IL-DSP.

Play music [Top]

Navigate the library and double-click on an album to add it to your playlist, then press the Play button.

Strawberry player control buttons

And that's it!

Playing audio from Strawberry to the miniDSP IL-DSP

Have fun, and please let us know how you go in our forum!

Postscript: system-wide audio [Top]

While Strawberry allows you to select an audio device specifically for music playback, you may also want to select your miniDSP device as the default system-wide output for all audio playback. This will vary with the specific version of Linux that you use. On Linux Mint, open the main menu and go to the Preferences section, then select Sound. There you can choose the audio output device, like this:

miniDSP IL-DSP as system-wide audio device on Linux Mint