Digital Room Correction (DRC) is a set of processes and algorithms that correct for response problems caused by the room. Solving this is a complex problem that involves a lot of sophisticated mathematics. miniDSP's DRC-capable processors use the Dirac Live system from Dirac Research, considered to be one of the most advanced and (importantly) best sounding room correction algorithms.
This app note explains the basics of digital room correction with miniDSP and Dirac Live.
Step 1: Measurement [Top]
The first step in any room correction process is acoustic measurement. In Dirac Live, this involves first placing a miniDSP UMIK-1 or UMIK-2 measurement microphone in the center of the listening area. Each microphone is individually calibrated for accuracy:
The Dirac Live software running on your PC or Mac generates test signals that play through your amp and speakers, which it captures with the UMIK. They are a "sweep" that starts at very low frequencies and increases through the whole audio range. It sounds a bit like a slow "whoop".
Because room effects change depending on where the microphone is located, Dirac Live asks you to move the microphone and make measurements in different locations. A total of nine to 17 locations are measured, depending on the size of your listening area. This way Dirac Live gets as much information as possible about how your room affects the response.
Step 2: Filter generation [Top]
This step is where the advanced math comes into play! Fortunately, for the end user (you) it's pretty simple as it's all built into the Dirac Live software.
On the Filter Design screen, you can adjust the target curve – this is the frequency response that you want. Because the response varies in the different measurement locations, Dirac Live uses some clever algorithms to figure out how to best way to correct the response overall.
If you wish, you can change the frequency range that is corrected by moving the "curtains" on either side of the graph:
While these controls are simple to use, there are a lot of digital smarts going on under the hood. Dirac Live also corrects the impulse response of the speakers. Essentially, this corrects the "smearing" in time caused by the crossover in the speakers. This correction is more subtle than the frequency response correction but improves imaging and realism. The Dirac Live app will show you the "before and after" impulse responses of your speaker:
Step 3: Processing [Top]
Once you've set up your target curve, you can download up to four different sets of correction filters into your miniDSP processor. You could have presets with different amounts of bass boost or correction frequency range, as in this example we set up in our system:
You could also have presets for solo listening and some for group listening (with a wider area for measurements).
Once your presets are all set up, all you need to do is play music! This time, all of the processing is done in the miniDSP processor – the computer is not needed any more. You can turn Dirac Live processing on and off with the remote control if you want to compare.
So what do I need?[Top]
miniDSP has a range of Dirac Live-capable processors, in two key types:
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Stereo processors are used with stereo sources and have two channels of Dirac Live processing. Choose from the DDRC-24†, miniDSP Flex (with Dirac Live upgrade), and the SHD Series†.
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Multichannel processors are used with multichannel audio input and have eight channels of Dirac Live processing. Choose from the DDRC-88A† or DDRC-88D† for studio and home theater application, or the C-DSP 8x12 DL† or Harmony DSP 8x12† for car audio applications.
You will also need a UMIK-1 or UMIK-2 measurement microphone. The processors with a dagger (†) include a UMIK-1 by default, while the others will need a UMIK-1 or UMIK-2 added to your order if you don't already have one.
If you have questions about the best miniDSP processor to choose, feel free to contact our support team and we'd be happy to help! You can also ask our customer community in our online forum.
