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How To Understand Speaker Specs

April 11, 2013 | Comments

If you were asked to name the top two or three things that matter most when assembling a home entertainment system, what would you say? For most of us it would be a late-model HDTV (or video projector) with a huge screen and a great sound system. No quibbles with the TV part, but what exactly do we mean by a "great sound system"?

Many ingredients go into a system that produces lifelike sound, but nothing is more important than the speakers themselves. You can have the best Blu-ray player and A/V receiver in the world, but if the speakers are poorly designed, it's all for naught.

And while the only way to judge sound quality is to sit back and listen to familiar music (or soundtracks), useful information can be gleaned from the spec sheets enthusiasts love but everyday folks ignore. (Reviews in enthusiast magazines, forums, and websites may provide independent measurements with an explanation of the findings, but they tend to be technical.)

What to Look For in Speaker Specs

The ironic thing about speaker specs is that they tell you little to nothing about a speaker's sound quality. Still, three are worth a look:

Frequency response describes the range of audible frequencies the speaker can reproduce between 20 Hz (deep bass) and 20 kHz (a piercingly high frequency), which is considered the range of human hearing. In reality, our hearing does not typically extend up to 20 kHz (especially as we get older), and bass frequencies below 30 Hz tend to be felt more than heard.

The most meaningful ratings include a plus/minus deviation (±3 dB is typical), which indicates how far the sound deviates from a neutral or "flat" response; the lower the number the better, although in practice, speaker placement and room acoustics greatly affect what you hear. Still, the number at the lower end of the range gives you an idea of how low the speaker can play. For example, a rating of 50Hz - 20kHz ±3 dB means you will need to add a separate subwoofer if you want to reproduce the deepest bass.

Sensitivity describes nothing about the sound itself but will give you an idea of how efficient a speaker is - that is, how loud it will play when fed a standard test signal and measured at a specific distance (usually 1 meter). Sound-pressure level (volume) is expressed in decibels: the higher the number, the higher the efficiency. Numbers in the mid-80s are typical, while anything over 90 dB is considered excellent.

Impedance sheds no light on sound quality but tells how much strain the speaker places on an amplifier. The lower the number, the more strain; most speakers are rated at 8 ohms, which is considered an easy "load." If you come across 4-ohm speakers, just make sure the amplifier driving them can handle the extra load (most good quality amps can).

Which Speaker Materials Are Best?

As far as materials go, if a speaker is well designed it doesn't matter whether its tweeter, midrange driver and woofer are made of aluminum, titanium, Kevlar, pick-your-exotic-material or treated paper. Any of these materials can be used to build an excellent-sounding speaker.

What to Listen For When Selecting Speakers

There's no substitute for listening, so gather some favorite discs, perk up your ears, and ask yourself…

  • Do instruments and voices sound natural, or are they muffled or shrill? With movies, is the dialogue intelligible?
  • Is the overall sound balanced? You'll miss out on a lot of wonderful detail in the midrange - where voices and most instruments fall - with "boomy" speakers that over-emphasize the bass (a common pitfall).
  • Do you feel like you've been transported to another space - a concert hall or the location of a movie scene? The better the speakers, the more convincing the illusion. Even a good stereo pair will produce sound that extends beyond the speakers, creating a sound stage that is wide and deep.
  • Most important: Trust your instincts. You'll know good sound when you hear it!

A trained home tech pro with audio and video installation and calibration experience will be able to help you get the most out of your speaker purchase, from selection to room layout and installation. To find a qualified professional in your area, click here.