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#1
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Ported Enclosure
If I've done all the algebra and stuff to tune a ported box, by
dertimining the length of the port. Does the port necessarily need to be within the sub enclosure? My idea is to have a subwoofer enclosed in a ported box, in the trunk, and to have the port actually come up into the car... Any thoughts? Has this been done before? Does it work? Mister.Lull |
#2
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On 29 Mar 2005 09:58:21 -0800, "Mister.Lull"
wrote: If I've done all the algebra and stuff to tune a ported box, by dertimining the length of the port. Does the port necessarily need to be within the sub enclosure? My idea is to have a subwoofer enclosed in a ported box, in the trunk, and to have the port actually come up into the car... Any thoughts? Has this been done before? Does it work? Mister.Lull I dont believe the port has to be inside the box, but keep in mind that the internal box volume will change depending on whether you put the port inside or outside the box. Any part of the port that is *inside* the box is counted as a solid object and must be subtracted from the internal volume. For instance, if you have a box with an internal volume of two cubic feet (3456 cubic inches), and you have 12 inches of 4-inch diameter port inside the box, you have to subtract about 150 cubic inches from the internal volume. With ported boxes, it's important to be as exact as you can with the internal volume and the port size, since they're not as forgiving of inaccuracies as sealed boxes are. Also, don't forget to subtract out the volume of the sub's magnet/basket structure when you calculate box volume. -- Scott Gardner "Marge, dont discourage the boy. Weaseling out of things is important to learn. Its what separates us from the animals...except the weasel." (Homer Simpson) |
#3
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Thank You!!! If I can put the ports outside the box without hurting
the sound, that'll help two ways: First, I can be more accurate on tuning the port since I won't have to calculate the length over and over again due to the changing volume of it (I hope that makes sense). Second, I can port directly into the car therefore enhancing the sound in there... Best news I've had all day! Mister.Lull |
#4
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Mister.Lull wrote:
Thank You!!! If I can put the ports outside the box without hurting the sound, that'll help two ways: First, I can be more accurate on tuning the port since I won't have to calculate the length over and over again due to the changing volume of it (I hope that makes sense). Second, I can port directly into the car therefore enhancing the sound in there... Best news I've had all day! Mister.Lull I did exactly what you are describing ... I am very happy with the results. HOWEVER, I now realize that I am only happy because of blind luck. When you port the box into the cabin of the car (I assume through the rear deck like I did) you are in essence creating a VERY huge bandpass enclosure, as opposed to a vented/bass reflex enclosure. The sub is still inside the confines of the trunk, but the backwave (through the port) is not in the trunk ... it is in the cabin. Hence the trunk becomes the "front" enclosure of the bandpass, and the box itself becomes the "rear" enclosure that is vented. Does that make sense? The reason this is important is that depending on the vehicle and just about every other variable you can think of, the end result may sound like complete ass. I believe (and this is complete conjecture) that I was lucky because I planned to tune the box ridiculously low when I fist built it (27Hz). This made for a very large box with a very large port (2.6 cuft with an 11" long / 3" diameter port for one 10" sub). This matched the "rear" enclosure of the bandpass well with the trunk space. Believe me .... the deep bass is astounding, although overexcursion is an issue with this setup so I keep the gains down and bass boost off. Hope any of that helps. Any thoughts or ideas about my thinking from you all? -- Dan Snooks |
#5
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On Tue, 29 Mar 2005 22:06:28 -0500, "Daniel Snooks"
wrote: trim The reason this is important is that depending on the vehicle and just about every other variable you can think of, the end result may sound like complete ass. trim That one sentence pretty much sums up all of car audio. You plan your system, do the research, pick your parts and do the math. Then, you have to install all of it into a car, which is one of the least predictable, least uniform environments you can imagine, and hope for the best. You can improve your chances by making good design decisions and picking the right parts, but there's always that nagging possibility that you're going to get everything installed, and it's going to sound like hammered dog****. -- Scott Gardner I'm all out of altitude, airspeed, and ideas..." |
#6
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Thanks you two,
I agree completely with that last statement especially, Scott! I think I'm going to give this a try on my friend's system... I was doing some beginning math with a sub that I happened to have the manual sitting around for, and found out that if he has a comparable 12" (the 10" shouldn't be so bad), then he'll have a 4" port that'll be around 21" long (I think that this was to tune it to 31hz or somewhere around there)!! It will be a lot more fun (and kind of neat looking) to have that huge length of port hanging around outside the box. Also, I do understand what you were saying about the box becoming a giant bandpass box, Dan. That's what I was worried about. I've been screwing around with subs and enclosures for a couple of years now, and out of all of the pictures I've seen (thank you google image search) I still have yet to see a ported enclosure with an external port... This was leading me to beleive that there was something faulty with the idea. Now that I have a better idea what to look out for, I can try and avoid a pitfall that I hadn't seen before. Again, thanks to you all! Mister.Lull |
#7
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Mister.Lull wrote:
Thanks you two, I agree completely with that last statement especially, Scott! I think I'm going to give this a try on my friend's system... I was doing some beginning math with a sub that I happened to have the manual sitting around for, and found out that if he has a comparable 12" (the 10" shouldn't be so bad), then he'll have a 4" port that'll be around 21" long (I think that this was to tune it to 31hz or somewhere around there)!! It will be a lot more fun (and kind of neat looking) to have that huge length of port hanging around outside the box. Also, I do understand what you were saying about the box becoming a giant bandpass box, Dan. That's what I was worried about. I've been screwing around with subs and enclosures for a couple of years now, and out of all of the pictures I've seen (thank you google image search) I still have yet to see a ported enclosure with an external port... This was leading me to beleive that there was something faulty with the idea. Now that I have a better idea what to look out for, I can try and avoid a pitfall that I hadn't seen before. Again, thanks to you all! Mister.Lull Remember ... there is no fault with designing a box that has the port sticking out of it. That box will act the same as any other ported enclosure if the port is working in the same airspace as the driver (eg. the trunk). The difference (read "bandpass instead of ported") occurs when venting into a seperate airspace (eg. the cabin) -- Dan Snooks |
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