Acoustics Matter: Easy Home Theater Audio Tweaks

Setting up a surround sound system isn’t rocket science, but most people take the easy way out by simply plugging everything in and leaving it at that. Remember though that every room affects sound differently, and receiver manufacturers don’t know what kind of speakers you’re using.

To get the most out of your surround sound system, you’ve got a bit of work to do and the below seven tips should help you get started.

1. What Are You Doing, Dave?
Many modern A/V receivers and surround sound processors come packaged with a calibration microphone and an automated setup wizard. Using test tones, this dynamic duo will “listen” to your speakers and automatically adjusting the optimal settings for your room acoustics and your speakers. However, some of these software-based calibration utilities are more effective than others, and many older receivers don’t have them at all. Consequently, it’s important to verify that your speakers are set up properly in the receiver’s configuration menu; don’t assume the microphone and a computer are smarter than your ears.

2. Size Matters
The first thing to check when setting up your speakers is size. Receivers differ on how they label this, but it’s usually some variant of “Speaker Size” or “Speaker Type.” The important thing to note here is that what the receiver is really asking about is driver size (and even that’s misleading), not the physical dimensions of your speaker. The question you’re essentially answering is, “Can this speaker handle a full-range signal (20Hz-20kHz) or does it require the help of a subwoofer to reproduce the low end?”

Although there is some debate on this, the safest rule of thumb is to set all of your speakers – any speaker, for that matter – to “Small” and establish a crossover frequency that’s closest to the low end of your speaker’s frequency response. For example, consider Paradigm’s Monitor 7 floorstanding loudspeaker, which has a published Frequency Response of :±2 dB from 54 Hz – 20 kHz. Even though this is a fairly big speaker, your best sound will likely come from setting it as “Small” and using a crossover of 60Hz. This lets your subwoofer worry about everything below 60Hz and the Monitor 7 can relax while reproducing everything between 60Hz and 20kHz.

3. Don’t Be Afraid to Cross Over
Continuing on with the previous example and Paradigm’s Monitor 7, remember too that every room has unique acoustic properties, and based on the fact that Paradigm claims a “Low-Frequency Extension” of 41 Hz for the Monitor 7, it would be worth experimenting with a crossover of 50Hz if your receiver offers this. Small satellite- and bookshelf-style speakers will definitely require a “Small” setting and a crossover frequency somewhere between 80Hz-120Hz. Read your speakers’ manual to find their published frequency response, and you may also find that the manufacturer recommends a specific crossover frequency. Find a bass-intensive sequence from one of your favorite DVDs or Blu-ray Discs, and put it on a loop. Experiment with different crossover frequencies and see if one sounds better. THX recommends 80Hz, but depending on your speakers and your room, 60Hz or 70Hz may yield better results.

4. Two is Greater Than One
There’s a great line in Robert Zemeckis’ criminally-underrated Contact, where John Hurt’s Dr. Hadden character shares the first rule of government spending with Jodie Foster’s character, Ellie: “Why build one when you can have two at twice the price?” When it comes to subwoofers, and bass performance in your home theater, Dr. Hadden is right on the money: two is better than one.

There has been much debate surrounding the optimal number of subwoofers for a home theater, and where they should go. While there have been studies indicating that four subs is best – with one at the midpoint of each of your four walls – the collective wisdom is that two subs can get you most of the way there without creating substantial financial or logistical headaches. Placing a sub in each of your two front corners is a great way to even out your bass response and create a more consistent and dynamic low end. Insert a Y-splitter just before sub #1, and connect the cable for sub #2 to the other leg of your “Y.”

5. Level Out
Before we move on from tweaking your receiver settings, make sure your speaker levels are properly set. This is another item that can be set automatically using a calibration microphone if your receiver came with one, but the surest way to equalize your levels is to do it yourself with a Sound Pressure Level (SPL) meter. Holding your SPL meter where your ears typically are when seated, use a calibration disc such as Avia, Digital Video Essentials, or Disney’s WOW disc to play test tones in each channel and adjust your speaker levels until the meter reads the same for each speaker. This will ensure smoother, more consistent sound when music or movie effects pan across the sound field.

6. Mirror, Mirror on the Wall
When sound leaves your speaker, it disperses into the room and reflects off of everything it encounters. Not surprisingly, the sound that comes to you directly (“direct sound”) arrives sooner than the sound that first reflected off your side walls. This slight delay or echo can muddy a room’s audio performance. To deaden the room, the best thing you can do is add absorption (bookshelves, curtains, absorption panels) at your “first reflection” points. To find your first reflection points, you’ll need a friend and a mirror. Sit in your prime listening spot and have your friend slide a mirror along the right side wall until you can see your front speaker’s tweeter in the mirror. Mark the spot and repeat the process for the left side wall. Placing something with absorptive properties at these locations should help deaden your room’s acoustics and improve audio performance.

7. Viva Lossless
To make sure you’re taking advantage of the highest quality sound from your Blu-ray Discs, always check to make sure you’ve selected the lossless soundtrack option. These days, most discs feature DTS-HD Master Audio, but Dolby Digital TrueHD and uncompressed LPCM can also be found on some discs. Also, some older Blu-ray Discs, such as Batman Begins and The Dark Knight, default to standard Dolby 5.1. In the case of those two titles, you have to navigate the pop-up menu to engage the lossless Dolby TrueHD soundtrack. And what a difference it makes!

If you have a newer A/V receiver with built-in DTS-HD Master Audio decoding, set your Blu-ray Disc player’s audio output to “Bitstream” and you should see a light or text on the receiver’s front panel to confirm that you are in fact listening to DTS-HD Master Audio. If it’s only reading “DTS,” you may need to disable or turn off the “Secondary Audio Channel” in your Blu-ray player’s setup menu. This is used during Picture-in-Picture video commentary modes, where the player is essentially providing two soundtracks simultaneously. And even if you’re not watching one of those commentaries at the moment, some players cannot bitstream a lossless soundtrack if Secondary Audio is enabled in the menu. Read your owner’s manual to see how your player should be configured for lossless audio output.

Read about audio room correction and why you need it here.