I found this info about port location and was wodnering what yall think. it makes perfect sense to me. Which in turn says i could technically put my port anywhere its not close to an object.
Questions on Vents
by
John L. Murphy
Physicist/Audio Engineer
Q: "How critical is the placement of the port(s) in an enclosure?"
To understand the sensitivity of a vented (ported) speaker to the location of the vent it is
first necessary to understand why it would matter at all. In a vented box type of woofer
subsystem all of the acoustic out put of the system is from the woofer driver itself at
frequencies well above the vent tuning frequency of the box, that is, the F(B). At lower
frequencies, specifically a narrow band of frequencies centered on the box tuning
frequency F(B), all of the acoustic output is from the vent. Thus the speaker system
consists of two acoustic sources: the driver and the vent. The total output of the speaker
system is the acoustic sum of the outputs of these two sources. In order for these two
sources to sum as intended the two sources must be largely "in phase". It is this phase
relationship between the two sources that is affected by the location of the vent. The phase
difference is also affected by the location of the listener.
What really matters is the DIFFERENCE in the distance of the listener from each of the
two sources. As long as the listener is the same distance from the driver and the vent the
space between the driver and the vent doesn't matter. But as a general rule we want the
frequency response to be constant no matter where the listener is located. Therefore we
want the vent and the driver located "close" to one another. In this case "close" means
within a small part of an acoustic wavelength at the box tuning frequency. Now, since
most vented systems are tuned below 100 Hz that means that the wavelength at the box
frequency is generally longer than about 10 feet (the approximate wavelength of a 100 Hz
tone). So as long as your vent is within, say, 1/4 of a wavelength the location of the vent
will not matter much. If the vent is more than about a 1/4 wavelength then the frequency
response in the bass range will become dependent on how the listener is positioned with
respect to the driver and vent.
So, if your speaker is tuned to 100 Hz you want to keep your vent no more than about 2.5
feet (1/4 wave) from the driver. But if your box is tuned closer to 50Hz (a more realistic
figure) then the vent only need be within 5 feet of the woofer. Since this is an easy criteria
to meet for most systems it seems fair to say that for most speakers the vent placement is
not critical.
Below is a table of frequencies and corresponding 1/4 wavelengths.
Frequency ---Wavelength ---1/4 Wavelength
200 Hz 5.65 ft 1.41 ft
100 Hz 11.30 ft 2.83 ft
80 Hz 14.13 ft 3.53 ft
60 Hz 18.83 ft 4.81 ft
50 Hz 22.60 ft 5.65 ft
40 Hz 28.25 ft 7.06 ft
30 Hz 37.67 ft 9.42 ft
20 Hz 56.50 ft 14.13 ft
10 Hz 113.00 ft 28.25 ft
Topic Closed)
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