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aeroport location

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=126997
Printed Date: October 31, 2024 at 5:59 PM


Topic: aeroport location

Posted By: rboutin2
Subject: aeroport location
Date Posted: April 18, 2011 at 9:10 AM

Any advice on where to put my 4" aeroports? Got 2 15" type r subs. 2.9 cub feet after sub displ. Per chamber. One 4" aeroport per chamber. I can't put the port on the front or back of the box. Rather not put on top. I am tuning to 33 hz. The box sits roughly 5 or so inches off the ground. Can I put the ports on the bottom facing the floor? Or maybe the side. How much distance do I need between the port opening and any object? My seat sits right against the port on the front of the box. About an inch at top of the port and 3 inches at bottom. Could I still put it there?

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Disturbin' Tha Peace



Replies:

Posted By: DYohn
Date Posted: April 18, 2011 at 10:52 AM
Ports should be on the same baffle as the drivers for best performance.  Why can't you put them there?  But for subwoofers since what you likely want is SPL, put them where they fit.  You do NOT want ports or drivers up against seats or any other surface.  They move air to make sound, so you have to let them.

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Posted By: rboutin2
Date Posted: April 18, 2011 at 11:34 AM
Well the port will be literally a foot from my ear. And the subs are gna move a lot of air and it will ne blowing right on me and passengers. Also it is mostly dd and sol on the side kinda system. Just want loooooud. What about slot port? What's up with the 1:8 h to w ratio? If I go by that rule my port needs to be way too long. If the slot is height of box.

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Disturbin' Tha Peace




Posted By: rboutin2
Date Posted: April 19, 2011 at 10:27 AM
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
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Disturbin' Tha Peace





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