LSS Rhetoric Page

I put this together as a bit of a primer on audio reproduction. It's not designed to be comprehensive but may help explain some of the factors that affect your audio enjoyment.

Psychoacoustics

First, we need to take a brief look at musical content. Most audio gear is quoted at 20 Hz to 20000 Hz (Hertz = cycles per second) considered to be range of human hearing. The illustration below shows the range of some typical musical sources. (Illustration by Peter Smith, used with permission)

The vast majority musical information is contained in 45 - 4000 Hz range with most vocals in the 70 - 1000 Hz range. So what happens to the rest of the range? Harmonics. A 1000 Hz tone has harmonics at 2000, 4000, etc. (For more on basic acoustics visit the Physics Classroom)

Reproduction of music (or movies) has a lot of variables beside the speaker. The source material, room geometry, electronics, and the hearing capability of the listener to name a few. When people listen to reproduced music, there are several well-documented phenomena at work. Vocals tend to dominate. (Midrange) If there are peaks, (exaggerations), most folks will hear them. If there are gaps (holes) most people will mentally fill them in.

When you go to the audio store for an audition, there are additional phenomena at work. If speaker X is a little bit louder than speaker Y, most people will prefer speaker X. There is also an order bias. If I demo A, then B, then C, most will prefer C. Listener's are also influenced by expectations (marketing hype) People who make and sell audio understand these phenomena.

So how do those expensive, little systems do such a great job? They really don't. Reproduction is focused on the midrange, there are large gaps at the top and bottom, deficiencies are masked by custom electronic compensation that takes advantage of harmonics. Ever notice how those systems are always in a room or area by themselves? The sales person always demo's them last, (they typically show you cheaper stuff first.) Throw in the marketing hype (they told you it's the best so it must be the best). If you don't hear it, you don't miss it. I gotta hand it to them. They've studied the problem, and consumers are buying them.

How does the room affect sound?

Answer: A lot! Sound bounces off of walls, get absorbed by carpets and furniture, and will be altered by obstructions. Where you place your speakers will have a lot to do with how they sound. This is particularly true for bass. Typically the F3 point is quoted by the manufacturer. That's the point where the bass is down 3 decibels from normal. (The decibel (dB) is the basic unit of volume. One dB is about the smallest increment most folks can hear.) Put a speaker close to a wall and you'll add about 3dB to the perceived bass. Put it in a corner, and you'll add up to 6 dB.

Another factor is know as the Baffle Step. As you move a speaker farther away from the wall, there's a notch created in the response. The speaker designer can adjust for this. So can the people who mix the music (a lot of rock music compensates for this, most jazz and classical does not)

Rooms with a lot of carpeting, upholstered furniture and drapes are acoustically "dead". Tile floors, windows and mirrors tend make a room "bright". Dead rooms are typically more pleasant for listening. Bright rooms often need the high end toned down a bit. Higher frequencies are more directional as well. Putting a small bookshelf on the floor will essentially kill most of the high end.

Subwoofer placement can be tricky. Bass becomes non directional at about 70 hz (not 200 hz like the "hose" company would have you believe.) Moving a big sub is not a pleasant task. So locating speakers (and a sub) for best listening is a science in itself. Throw in the logistics of wall plugs, interior decorating tastes, lifestyle, kids, pets, traffic etc. and every room presents a unique listening environment. (This is why I like to visit your room before building)

What Kind of Equipment Do You Need?

People love to compare numbers. Power ratings, distortion, all kinds of numbers are thrown at the consumer. Here's a brief run down on the physics. Each 3 db increase in volume requires that you DOUBLE the power. Most adults listen to music at 80-90 dB, 130 dB is the pain threshold. Most loudspeakers will produce 82-90 db with 1 watt of power. So if your speaker is quoted at 85 dB (1 Watt) then you'll use 8 watts for 95 db. But this isn't linear. 5 watts at 8,000 Hz would probably make your ears bleed, 5 watts at 30 Hz may be barely audible. Low tones need more power to push all that air.

Whoopie ding. What does this mean to the consumer?. For full music reproduction, 50-60 watts of clean power is all you really need. If you want the true home theater experience, (25 hz) then a self powered subwoofer with it's own amp is the right choice. It also means that a 160 watt receiver will not be perceptibly louder than a 120 watt receiver. If you have to pick one spec, compare weight – the heavier the amp the better. I'm not going to get into peak, RMS and all that stuff.

Your audio system is only as good as it's weakest link. Putting a pair of high quality speakers on a boom box will only reveal problems with the rest of the system. So what should you buy? It depends. Budget, perfection quotient, aesthtics etc... all affect your choices. In the end, buy what YOU like (not what the salesman says is best).

Cables and Cords are hotly debated. Speaker wire should be copper, 12-16 gauge. You'll find it easier to work with the flexible stuff. IMHO, throw away the patch cords that came with your component. Patch cables are worth spending $10 -$25 for a decent installation. I've been pretty happy with Parts Express Dayton cables and Sound King wire as good bang for the buck.

As far as brand names go,Yamaha, Onkyo, Denon, Outlaw, NAD, AMC, Harmon Kardon, Pioneer Elite, Sherwood, Adcom and Marantz typically make better than average products for reasonable prices. Sony and Techniques both make some great products and some real dogs. You don't have to spend a bundle either.

In 2004 several new all digital HT receivers hit the market. These are very small, and using optical or coax feeds from a decent DVD player, they will yield excellent quality. My current favorite is the all digital PANASONIC SA-XR55. It can be purchased for under $300.  Some great values are also available from Outlaw Audio. For stereo, older receivers from these companies frequently show up on Ebay and pawn shops. If you have doubts, it may be worth while to check out the component at Audio Review. Here are a couple of other sites you may find enlightening: