TWEETERS, WAVEGUIDES AND OPTIMAL FREQUENCY RESPONSE
The dispersion pattern of the sound produced by a speaker is different at low frequencies than at high frequencies. At frequencies with wavelengths greater than the circumference of the speaker’s cone – the speaker’s piston range – the sound is radiated in all directions. At higher frequencies, the dispersion pattern narrows. At frequencies for which the circumference of the speaker is about five times the sound’s wavelength, the coverage area narrows sharply and the
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| On Axis |
110 dBSPL |
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| Off Axis |
100 |
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90 |
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80 |
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70 |
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60 |
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50 |
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40 |
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30 |
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20 |
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10 |
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20Hz | 50 | 100 | 200 | 500 | 1K | 2K | 5K | 10K | 20K |
Figure 4. On- and
When we listen to speakers, we hear a combination of the sound that comes directly from the speaker (the
In cars, the boundaries are much closer to the speaker and to the listener, so the intensity of the reflections is more similar to the intensity of the direct sound. Additionally, the reflective surfaces in a car are so close that our brains can’t distinguish between the direct sound and much of the reflected sound. Reflections contribute greatly to the quality of the audio experience in cars. Since it isn’t practical to change the overall shape or size of the car to minimize the effects
of the reflections, closely matching the on- and
0°
030°
60°
270° | 90° |
Figure 2. Woofer dispersion pattern in the crossover region.
0°
030°
60°
270° | 90° |
Figure 3. Tweeter dispersion pattern in the crossover region.
Sound from Speakers
Reflected Sound
Figure 5. Reflected sounds are attenuated at the listening position because the boundaries are far from the speakers and the listener.
Reflected Sound
Sound From Speakers
ENGLISH
Figure 6. The intensity of reflected sounds in a car closely match that |
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of the direct sound, because the boundaries are close to the speakers |
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and the listeners. | 7 |