Date: Tue, 26 Apr 2011 12:11:35

Author: Jerry DiMarco

Subject: Re: speakers

Post:

At 4/26/2011 10:30 AM, you wrote:
>......
>1. Does the impedance of a speaker affect the sound quality/loudness?

The sound quality may be affected indirectly. One example is the
case of an amplifier with an 8 ohm output impedance connected to speakers
with 4 ohm input impedance. If the amplifier cannot handle the increase in
current drawn by the lower impedance speakers, the music signal peaks may
get clipped and sound distorted. A 16 ohm speaker in the same situation
would not cause signal distortion since it draws less current from the
amplifier.
The loudness can be affected by speaker impedance. A low impedance
speaker draws more power and would be expected to sound louder. A high
impedance speaker draws less power and would be expected to sound
softer. However, speaker efficiency (sound level/input power) is a factor
as well. If a low impedance speaker in also less efficient, it may not
sound louder...

> So for a given power, you need a certain "ideal" impedance (resistance). And
>if you use a speaker with a higher impedance, the power output will
>decrease (P = V2/R)?

Already answered...

>2. Are the crossover frequencies the lower limits of the midrange and
>tweeter, respectively?

Each speaker element has a characteristic frequency response curve
that shows the sound level output for a standard power input. Outside the
frequency range of the speaker, the sound level begins to drop. The
frequency where it is down 3 dB is usually chosen as a crossover
frequency. Then another speaker that operates in the adjacent frequency
range would be chosen that has the same -3 dB point. The 2nd speaker's
increasing response in that frequency range compensates for the decreasing
response of the 1st speaker. Their response curves crossover at their
shared -3 dB points, which is why it's called the crossover
frequency. There is a nice graph of this on Wikipedia's Audio Crossover
page...

Jerry
D



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