T
Tittentei
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Denne artikkelen om flere subwoofere og hvordan fase og romakustikk påvirker SPL er bra.
Data-Bass
Avsnittet "Side Test: How much SPL from adding an identical subwoofer?" er veldig interessant. Der står det følgende:
[h=3]Side Test: How much SPL from adding an identical subwoofer?[/h] One other short test we conducted was to measure a subwoofer system with four separate, identical subwoofers placed away from each other in room and measure what happens to the frequency response and output when you start with one operating and add in the others one at a time until all four are operating at the same output level. This is shown in the chart below.
It is often times stated that the maximum gain that can be seen from adding an identical subwoofer producing the same output level is 6dB and that the full 6dB will only be realized if they are within 1/4 wavelength of each other or in other words, co-located or placed very close to each other. This is not correct in practice, in a confined environment, or basically anywhere other than very large anechoic chambers, outdoors, and huge spaces. There are a variety of factors that can cause a different interaction at the listening position such as the room acoustics, the distance from the individual subwoofers to the listening position, and the placement of each subwoofer in room.
In the example given, the green trace is one subwoofer, red is two, blue is three and the black trace is with all four of them operating. It is easy to see that adding in the second subwoofer caused a gain larger than 6dB at the listening position in quite a few places – 12, 30, 40, 50 and 90Hz for example. Over some ranges output was actually lost (58-65Hz and 97-116Hz) most likely due to the phase relationship at those frequencies.
Looking at the gain seen from adding in the third subwoofer, note that again at 30Hz more than 6dB is gained and the system’s total radiation is not even doubling at this point by adding a third sub. At 80Hz we again see a slight loss.
By the time the fourth subwoofer is added in, the gain is between 2-4dB for the most part. However, note that the overall response has been flattened out and smoothed significantly, fitting within a 12dB window from 5-120Hz, where it was about an 18.5dB window before with much more overall variation.
Obviously, you cannot simply assume a static gain of any amount over a substantial frequency range when the system is emitting from multiple points within a room or other confined space. Put simply, gain is not assured at all at any specific frequency. Nor is the maximum gain by doubling the system capped at 6dB at any one frequency due to the complex interaction of all of the forces in play once you confine the system inside an enclosed vessel.
Data-Bass
Avsnittet "Side Test: How much SPL from adding an identical subwoofer?" er veldig interessant. Der står det følgende:
[h=3]Side Test: How much SPL from adding an identical subwoofer?[/h] One other short test we conducted was to measure a subwoofer system with four separate, identical subwoofers placed away from each other in room and measure what happens to the frequency response and output when you start with one operating and add in the others one at a time until all four are operating at the same output level. This is shown in the chart below.
It is often times stated that the maximum gain that can be seen from adding an identical subwoofer producing the same output level is 6dB and that the full 6dB will only be realized if they are within 1/4 wavelength of each other or in other words, co-located or placed very close to each other. This is not correct in practice, in a confined environment, or basically anywhere other than very large anechoic chambers, outdoors, and huge spaces. There are a variety of factors that can cause a different interaction at the listening position such as the room acoustics, the distance from the individual subwoofers to the listening position, and the placement of each subwoofer in room.
You cannot simply assume a static gain of any amount over a substantial frequency range when the system is emitting from multiple points within a room or other confined space.
In the example given, the green trace is one subwoofer, red is two, blue is three and the black trace is with all four of them operating. It is easy to see that adding in the second subwoofer caused a gain larger than 6dB at the listening position in quite a few places – 12, 30, 40, 50 and 90Hz for example. Over some ranges output was actually lost (58-65Hz and 97-116Hz) most likely due to the phase relationship at those frequencies.
Looking at the gain seen from adding in the third subwoofer, note that again at 30Hz more than 6dB is gained and the system’s total radiation is not even doubling at this point by adding a third sub. At 80Hz we again see a slight loss.
By the time the fourth subwoofer is added in, the gain is between 2-4dB for the most part. However, note that the overall response has been flattened out and smoothed significantly, fitting within a 12dB window from 5-120Hz, where it was about an 18.5dB window before with much more overall variation.
Obviously, you cannot simply assume a static gain of any amount over a substantial frequency range when the system is emitting from multiple points within a room or other confined space. Put simply, gain is not assured at all at any specific frequency. Nor is the maximum gain by doubling the system capped at 6dB at any one frequency due to the complex interaction of all of the forces in play once you confine the system inside an enclosed vessel.
