Home-Theater Audio Quiz

I cringe when I see a "home theater" consisting of a 60" high-definition video display and a $400 home-theater-in-a-box. Why don’t you ever see "home theater" systems with a huge speaker array and a 19" flat panel? Because it "doesn’t make sense"? Well, what makes sense about a big, beautiful video display and a dinky audio system that can’t come remotely close to holding up its end of the home-theater experience?

Here’s a home-theater audio quiz. Answer the questions, then score yourself and see if you’re already on top of home-theater audio, or whether you still have things to learn that will help you get better sound from your system.

1) Which one of the following audio coding/decoding (codec) formats will you not find on the hi-def HD DVD and Blu-ray video formats?

A) Dolby Digital Plus
B) DTS-HD
C) Dolby TrueHD
D) DTS
E) DTS-HD HR (High Resolution)
F) Dolby Digital
G) DTS-HD MA (Master Audio)
H) A, C, D, E, F, G
I) A, B, C, E, G

2) The middle of a rectangular room is a good place to put the listener-viewers.

A) Always
B) Sometimes
C) Probably never

3) Which of the following are drawbacks about using 5.1- or 7.1-channel analog connections for music or movies?

A) Six or eight good cables are expensive
B) When you use multichannel analog inputs, AVRs and processors often can’t perform bass management, adjust speaker levels, compensate for speaker distances, or apply enhancement modes such as Music or Cinema (which add the surround back channels, THX modes, etc.).
C) Remembering to switch the source player and/or AVR to Multichannel Analog mode.
D) The .1 LFE or subwoofer level can be way too high or way too low.
E) All of the above
F) B and C only

4) What is the frequency range of "the bass octave"?

A) 30-60Hz
B) 20-100Hz
C) 40-80Hz
D) 20-80Hz

5) In this age of discrete 5.1- and even 7.1-channel surround sound, are dipole surround speakers (which radiate sound to the front and to the rear, instead of only towards the listener) ever the right choice?

A) No. With discrete sound now available for each soundtrack channel, there’s no longer any reason for dipole surrounds.

B) Yes. Dipole surrounds are always the best choice.

C) Yes. Dipole surrounds may be appropriate in rooms that are so small that direct-radiating speakers would be much too close to one or more listeners.

6) HDMI 1.3a provides Dolby TrueHD, DTS-HD, Deep Color, and other performance enhancements.

A) True
B) False

7) An inexpensive, handheld sound-pressure level meter is all you need to check your system’s bass levels from 20 to 100Hz.

A) True. Handheld SPL meters are most accurate when measuring bass frequencies.
B) False. Handheld SPL meters are least accurate and most misleading when measuring bass frequencies.

8) To get the best sound from your home theater,

A) use a combination of diffusion and absorption to smooth the frequency response.
B) make the room quieter by eliminating or reducing noise from all sources.
C) find the best locations for the speakers, subwoofer, and listeners.
D) properly use all the adjustment parameters in your AVR/processor.
E) All of the above
F) A and B only
G) A, B, and C only

9) What type(s) of speakers are most likely to produce the best sound when properly installed?

A) Speakers that mount on the wall or in a cavity in the wall.

B) Freestanding speakers placed on the floor or on sturdy stands.

C) Bookshelf speakers placed in a bookshelf or in an entertainment center.

D) Speakers mounted to the ceiling and aimed straight down.

10) Peaks in bass response can be reduced or eliminated by:

A) moving the subwoofer or listeners to positions where the peaks are not present.

B) using a parametric equalizer with a real-time analyzer.

C) placing 1"-thick absorbing panels on the wall(s) near the subwoofer.

D) using the bass tone control on the AVR or processor.

E) All of the above

F) A, B, and C

G) A and B

Answers:

1) B. There is no such thing as DTS-HD; it must be followed by HR (High Resolution) or MA (Master Audio). These two varieties of DTS-HD are different.

2) C. Probably never. Strong axial room modes exist in the middle of just about every rectangular room. You want to be away from those if you want good sound.

3) E. All of the above. All audio processing takes place when the sound is in digital PCM format in the AVR/processor. If you have six channels of analog sound coming into the AVR/processor, it must be converted to PCM digital audio for all the processing to be done. Many AVR/processors have only one stereo analog-to-digital converter. Three stereo A/D converters are required to digitize incoming 5.1 sound; four are required for incoming 7.1 analog sound. Multichannel analog is often passed to the amplifiers or preamp outputs without any processing applied.

4) C. The bass octave is 40-80Hz. The deep-bass octave is 20-40Hz, and the upper-bass octave is 80-160Hz. Any doubling (or halving) of a frequency represents an octave; 30-60Hz also describes an octave, though not the bass octave.

5) C. Time and progress have mostly passed dipole speakers by. When surround was decoded from matrixed analog, dipoles served a purpose in many home theaters, but if the room is large enough, direct-radiating speakers are the best choice for localizing sounds at the rear of the room because soundtracks are being recorded with localization effects, such as dropped keys or a door slammed behind the listeners so they know something is happening in a specific location back there somewhere.

6) B. False. By itself, HDMI 1.3a does nothing at all. It’s up to the equipment manufacturers to include all the enhancements HDMI 1.3a is capable of transmitting. HDMI 1.3a allows Dolby TrueHD, DTS-HD, and Dolby Digital Plus signals to be sent from one component to another via an HDMI cable, but the manufacturer of the component must build those features into the product itself or they will not be available. Some new hi-def disc players with HDMI 1.3a are still incapable of sending some hi-rez audio formats via HDMI; if this feature is important to you, research these products carefully.

7) B. False. When measuring bass frequencies, you can be easily misled by a handheld SPL meter. You really need a Real Time Analyzer or equivalent combination of hardware and/or software to get reasonably accurate bass measurements. Even then, bass is not easy to measure accurately. If you think what you hear in the bass doesn’t agree with what your handheld SPL meter tells you, it’s probably your ears that are correct.

8) E. A, B, C, and D are the fundamentals of getting better sound in your home theater system.

9) B. High frequencies tend to be reproduced best when not surrounded by large, flat surfaces. Speakers that can be placed in a room with some flexibility can end up sounding dramatically better than speakers that must be mounted in or on a flat surface.

10) G. Moving the subwoofer or listeners and/or using a parametric equalizer are the most effective solutions. Absorbing panels only 1" thick are too thin to affect bass frequencies at all. And the bass tone control changes the entire bass region, not just the peaks.

If you answered nine or ten questions correctly, congratulations -- your system probably already sounds pretty good. Seven or eight right answers mean you have the basics covered, but there’s room for improvement. Five or six correct means you’re either just getting started or you still have a lot to learn. One to four right answers? Well, maybe you need some outside help to get your system on the road to sounding great -- or a lot of studying.

 ...Doug Blackburn
db@hometheatersound.com

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