"The best way to evaluate a speaker is to listen to it but there are those of us who insist on thoroughly examining the specs and if you're going to read the specifications, make sure you know what they mean."
"Surrounds and spiders are kind of like shoes, they're not very flexible at first but with use, they become much more flexible and as the surrounds and spiders in your speakers become more flexible, your speakers will sound better."
"Before you rush out to begin frantic listening tests with a dozen of speaker systems, you might want to spend time preparing a few questions you might discuss with the audio consultant. What kind of amplifier or receiver will power the speakers? What is the maximum budget, and what budget is comfortable for me? Where are the speakers to be located, and what if anything, limits their placement? What kind of furniture, walls, and overall size describe the room?"
"The distance at which response is measured, the size of the room, the axis of measurement, the nature of the test signal, the power level used for the test… all of these factors, and more, affect the measured frequency response"
dB SPL - is used to described sound levels. "dB" or decibel is not a unit of measurement, rather it is a ratio and the dB scale was developed to handle large number ranges. To find the difference, in dB, between two numbers, take the ratio of the numbers, mathematically convert the fraction to a logarithm and multiply by 10 (for dB of power) or by 20 (for dB of voltage or sound level). They are not necessarily absolute numbers, and that twice the dB is not twice the power, voltage, level, etc….
Reference level for SPL (sound pressure level ) is the average threshold of human hearing at 1000Hz, also designated as “0dB SPL”. Highest level that our ears can handle before sound becomes painful is about 120dB SPL. That, in terms of loudness, is one million times as loud as the softest sound, (0dB SPL). Loudness of a sound and its SPL can be read by a SPL meter. It's very useful to have one if you want to properly set up your speakers for loudness, especially in setting up speakers for your home theater system. A good SPL meter should cost you no more than a hundred dollar.
Noise - Noise is described as any sound that is irritating to our ears. “White Noise” and “Pink Noise” are two types of mathematically predictable noises that can be produced by test equipment for speaker measurements. White Noise is a random mixture of all audio frequencies, at equal voltage levels. An example of White Noise is the Inter-station noise on an FM tuner. White Noise can be used to determine the directional characteristics of a loudspeaker. Pink Noise, because it has equal energy in each octave of the audio spectrum, is often used by a manufacturer for speaker system measurements. The use of either White or Pink Noise for power or sensitivity ratings is meaningful, but difficult to compare to other ratings.
Music - A "tone" is a musical note and it may be a pure single-frequency note or it may include numerous “harmonics” (over-tones and undertones). Harmonic structure of a tone, including the relative loudness of all frequencies, gives a tone its characteristics “timbre”. We can identify different instruments, and different people’s voices by their timbre. “Pitch” is the quality of a tone that determines its position in a musical scale and it is related to the primary or fundamental frequency in a tone but, because we do not hear in a strictly linear fashion, frequency alone does not determine the pitch. A low-frequency tone will become lower in pitch as its loudness is increased… even though the actual frequency remains the same. Try turning up the volume while listening to a bass note, and the note will sound lower in pitch. Other qualities of a tone also influence its sound, including Vibrato (wavering frequency), Tremolo (wavering volume), Attack (the time to reach full volume), Decay (the time to fall to sustained volume), Sustain (volume at which a tone is maintained without further intensity loss) and Release (time for a tone to die after it is no longer played).
When buying speakers, bear in mind that some speakers may do a better job reproducing some musical characteristics, while other speakers may do a better job with other characteristics. A speaker system with solid bass output may have poor transient response (transient is any short-duration musical or non-musical peak), preventing it from responding quickly enough to accurately reproduce music with fast attack times such as plucked strings. A speaker with good transient response may have poor frequency response or inadequate power-handling capability, detracting from its ability to accurately reproduce the harmonic content or dynamic range of certain instruments. Many speakers perform well in one respect, yet poorly in other respects, so listen to different types of music to different instruments, and to vocals in order to properly evaluate the speaker system.
Musical spectrum content - Spectrum analyzer chart above is an example of a frequency response measurement, averaged 1/3 octave "bands", that represents a recorded program material on a CD. The chart illustrates why a speaker with wide, flat frequency response is needed for accurate reproduction and observe how there is little program at the extremes of audible spectrum. It's hard to get much frequencies above 16kHz, and frequencies below 50Hz. You would not be losing much music program by purchasing less costly speakers whose frequency response falls off at the lowest and highest ends of the spectrum; as long as they are "flat" through the range of frequencies they do reproduce, the sound will be quite good...in some cases, indistinguishable from speakers with wider response. Compromise is a better way to save money than purchasing speakers that claim response from "20Hz to 30kHz", but give mediocre performance throughout the range they actually reproduce.
Dynamic range - Refers to the difference in sound pressure level between the lowest and highest levels in a recording. In live sound, the dynamic range can vary from low level sounds, near the threshold of human hearing (“0dB SPL”), up to the threshold of pain (approximately “120dB SPL”). Difference in acoustic power between these low and high levels is 10 to the twelfth power (one million times one million), or 120dB and Weber-Fechner Law describes how we react to sounds with such a great difference in level. Music in a live performance often has a dynamic range of up to 100dB and commercial recordings and FM broadcasts typically have only a 40 to 50dB dynamic range. Compression of the original dynamic range is necessary to avoid the loss of quieter passages due to background noise, and to minimize distortion of louder passages due to the limits imposed by the recording or transmission process.
Most homes have an ambient noise level of approximately 40dB SPL The ambient noise level refers to “background” noises such as air-conditioning, outside traffic noises, appliances, etc., so in order to hear the softest part of a recording, it must be played above this level. If the music has a dynamic range of 60dB (a good classical recording), then the peaks will be 100dB SPL (60dB above the 40dB SPL ambient noise) and few home stereo systems are capable of playing that loud. 10-watt amplifiers used in many compact “hi-fi” systems would give you a useable dynamic range of only 50dB, so it becomes obvious why good sensitivity and high power handling capability are both desirable in a speaker system.
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