How to Calibrate Dual Subwoofers with Anthem’s ARC Room Correction System

In this article, I’m going to cover how to setup and calibrate two subwoofers in a dual subwoofer configuration when using room correction systems.  Two or more subwoofers will always make your music and home theater configuration sound better and have more impact because two or more subwoofers address the issues associated with room modes better that a single sub can.  While this method we’ll be covering can be applied to many of the room correction offerings out there, we’re going to look at this setup specifically through Anthem’s Room Correction (ARC) system.

Anthem’s ARC has been widely regarded as one of the better room correction systems available on the market today and has won a long list of praise from reviewers and installers alike.  ARC is available in their higher-end preamp processors such as the D2v 3D and the AVM50v 3D as well as in their mid-line MRX receiver series.

I’ll be using dual SVS SB13-Ultra subs, which are in for a forthcoming review, as the subwoofers in a 7.2 home theater setup that I’ll be referring to in this article.   Remember, the .x always refers to the number of subwoofers.  So a 7.1 system is seven speakers and one subwoofer and a 7.2 system is seven speakers plus two subwoofers, etc.

Before we start, I wanted to provide you with a graph (courtesy of SVS) of the anechoic measured response of the SB-13 Ultra subs.

Anechoic SPL and frequency response of the SVS SB13-Ultra Subwoofer courtesy of SVS.

Most room correction systems (ARC included) need some special attention when setting up a dual, triple, or quad subwoofer setup—regardless of how many subwoofer outputs are located on the pre-pro or receiver.  One would think that all you need to do is setup the microphone, run the calibration and you’re done.  It’s not that simple.

Instead of calibrating each subwoofer individually, most room correction systems will play all the subwoofers together and then apply the necessary EQ.  That means that you’ll need to take some preliminary steps before you start the EQ process.  You can see my individual subwoofer measurements below to give you an idea of what my setup looked like.

Even though the SB13-Ultra has a good anechoic response, look at how the room plays a huge factor in the sub’s performance.  Measurement of the right SVS SB13-Ultra Subwoofer from the primary listening position. There’s a peak SPL reading of about 78db.

Notice the huge frequency response difference with the second SVS SB13-Ultra subwoofer, which is placed in the left corner of my room.  There are several SPL peaks as high as 80db but also many pronounced dips.

With Anthem’s ARC, here’s how you setup and properly calibrate a dual (or more) subwoofer configuration.

1. Setup your subwoofers properly.  First and foremost, setup your subwoofers in their optimal position.  Even though ARC is great, no room correction is a perfect cure for improper speaker placement.  Note: Remember, ARC has a “Quick Measure” feature that you can use to see what the frequency response of your subwoofer (or any speaker) is in real-time so that you can make adjustments.
   1. If you have two subwoofers you can try and of the following initial configurations:
      1. The 1/4 and 3/4 mark along the front wall
      2. The middle of the front and back wall
      3. Opposing corners of your room
   2. If you have three or more subs, place those subwoofers in the middle of the walls or in the corners of the room.
2. Set Each Subwoofer’s Phase: ARC does not set phase so you will need to do that individually for each subwoofer.  Setting phase is easy. Simply play the Pink Nose from the Level Calibration menu and with an SPL note the volume of the subwoofer as you change its phase settings.  The loudest SPL reading is the correct phase.  Some subwoofers have a variable phase dial, some only go in 90 degree increments.  Others, like the SVS SB13-Ultra subwoofers go in 15 degree increments.
3. Calibrate each subwoofer individually  Calibrate each sub in your setup using the pink noise in the Setup Menu’s Level Calibration.  Level each subwoofer individually to 72db (the Anthem user manual says 71db but I find that too low) using an SPL meter.  Do not use the Anthem’s Level Calibration to set the subwoofer volume.  Use only the subwoofer’s built-in volume control to calibrate each subwoofer.  You can calibrate each subwoofer individually by turning all the other subwoofers off and doing one at a time.  The combined SPL of the subwoofers together will bring the total to 75db.
4. Note about subs with built-in calibration: My personal preference is to let only your receiver do the room correction.  However, I realize there are some who may still want to try overlapping room correction systems if their sub has it as well.  One note for those of you who may have subwoofers that already have room correction kits or features.  If you chose to use the subwoofer’s own room correction, it’s imperative that you run that system prior to running ARC.  ARC should be the final step in your calibration process.  The way ARC handles the room correction process—by correcting the average—is the correct approach.
5. Run ARC. Once you have all your subwoofers setup, corrected for phase, and calibrated, you then run ARC as you normally would.  Because you have been turning subwoofers on and off individually, make sure all your subwoofers are now on before you run ARC!
6. Test your Results. Once ARC is finished, you will see a single, corrected curve and you should now test out the results.  As with any system—no matter how good it is—always let your ears decide.  In my particular case, I wasn’t happy with the final volume that ARC set for the SVS subwoofers.  Post-ARC, I ended up increasing the subwoofer’s output +3db vs. what ARC had set it at.