How To Compare and Buy Audio Equipment — How We Test Sound on Advicesisters.com
By Anthony Sabatini
People ask how do you review a headphone or a speaker? How do you know what it is supposed to sound like? In the audio field, we measure and compare based upon known standards, specifically recordings where we know every note of every instrument and what it should sound like. We come to this by picking an excellently recorded piece of music and listening to it on literally hundreds of different playback devices from $30,000 speaker systems to $30.00 clock radios and from $6,000 headphones to $10.00 earbuds. You must love this song in order to be able to listen to it critically.
Since I have been in rock and roll for much of my life, my standard has been “The Chain” from the Fleetwood Mac album “Rumors.” (in fact the album is so well produced that many of the songs on this album can be used for critical comparison ). I listen for each individual note of each instrument, listening for the highs and transience of the cymbals which will tell me about the quality of high frequency reproduction and the thump of the base drum (it is a “splat,” or can you actually hear the foot pedal hitting the skin of the drum)? In the mid range, does it sound like the singers are too far away, or do the sound reproducers overload when driven to their maximum which will cause distortions in the “busy sections” of the song. By listening for these things, I can tell an awful lot about the headphones and about their construction. One can hear uncompensated resonance which causes distortion in certain passages. One can hear over-compensated base or bad transient response (the sharp strike of a cymbal, for example) by a dullness in the sound.
This information is important to you (as a consumer) whenever you audition to buy any piece of sound reproduction equipment. Always take a known recording (your own Cd or that piece of music on your music player) and listen to it on many of the speaker or headphones systems, so that you know what they can handle (you want to do a comparison by switching back and forth between speakers or headphones in the middle of a passage so that you can compare more directly). One last note to check is whether the sound reproducer sounds good at a number of different volume levels, or only at one particular volume level. Our ears are not linear. They respond less well to lower volume at certain frequencies than others (such as bass). A good sound reproduction system sounds good at many volume levels, not just one.
Open-ness: Does the sound seem to be all around you or does it really feel like it’s either left or right? You want open-ness because it makes you feel like the sound is all around you, almost as though you are swimming in the sound. Inexpensive headphones make the sound feel as if it was only on the left oe right not seamlessly around the whole environment
Clarity: When a sound element is driven beyond its ability to respond, that is, it has not completed the last wave of sound before the next wave begins. you get “muddiness,” where the notes seem to run together. This is a problem with sound elements that are either too heavy or their suspension is too stiff, leading to this condition.
Distortion: Distortion is heard on the low end as almost a buzz, and the high end as crackling at the edge of the music. It happens because the sound element reproducing the sound is driven beyond its capabilities.
Resonance: A good speaker or headphone does not interact with the music it is reproducing. When it does, this is called “resonance.” Resonance happens when the materials in which the sound reproducing elements are mounted, vibrate audibly, due to the music. In a properly designed system, the structure which holds the sound reproducing elements must be totally rigid, materials like cheap plastic will audibly vibrate in this environment.
Frequency Response The element in a speaker or a headphone that produce sound, require more power to do so the lower the frequency, yet the signal provided to the headphone or speaker is not adjusted in that manner. If it is not compensated properly within the headphone or speaker, the frequency response, and thus the ratio of different instruments as reproduced, is changed.
Transient Response: Much of what we love in music are single notes. The pluck of a guitar string, the single notes a piano refrain, the striking of a drum, the crash of a cymbal. All of these are transients. All of these involve the reproduction of many frequencies at the same time for a short period, and it is for this reason that it is the most challenging issue for someone designing sound reproduction equipment. When they fail to do it properly, the music becomes colorless and dull.
Linearity: The frequency response of many headphones and speakers changes with the amount of power applied, although it should not. The ideal headphone or speaker should reproduce frequencies faithfully no matter at what level. This is however complicated by the fact that our ears are not necessarily linear in their response to lower level sounds. This is why we test at three different volume levels. The first level is where we feel comfortable with the volume level (ie. a reasonable listening level in a quiet room). The second level is where the headphones or speakers seem to have the best reproduction of the sound. This is often quite a bit louder than normal listening levels on less capable headphones or speakers. Our third check is for linearity where we cut the level so that the music is quieter, to check to see if we can still hear the highs and low end of the speakers or headphones.