Sub placement on baffle & port location

[Rail 0]

I've been reading the Loudspeaker Design Cookbook and found the effects of lobing due to driver placement on the baffle, but am still left wondering two things. Use the picture below as a reference to how the placement would differ. Assume same port length and volume for each. 

 

#1: The port ends in a different location inside the box, does this have different loading effects on the sub? From appearance, it would seem that the air flow in each would be somewhat different and affect the subwoofer? 

 

#2: What happens to the subwoofer and response as you move it closer or farther away from the port? Is it best to have it centered or off to a particular side? 

 

[Sencheezy 689]

SPL testings have shown increase in DB's by having Slot port on one side. For aero ports, increase pressure from having it centered as possible (away from any near walls). 

 

great drawings btw lol

[Sencheezy 689]

as far as sub and port placement is concerned, this will very per vehicle. And I mean every vehicle. Not only vary by vehicle, but also by physical alterations to the vehicle. 

 

Example A:

 

If in my SUV, I have Sub up and port back, I may find my highest score with the the rear doors open. But if I flipped the orientation, now my highest score may be with only the passenger front door open. 

 

I hope this makes sense.

[Rail 0]

Had to make it all pretty with a ruler, don't know what it would have looked like otherwise haha

 

Ok so slot port enclosure A would have a slightly higher SPL than B due to the increased pressure for air to be pushed and pulled through the port? My initial thoughts were that that would be the case. 

 

I understand that subs up and port back or whatever variation depends on the vehicle, but what about the placement of subs relative to the slot port if the port and sub directions are not changed? Still centered? Because I would think that if you had the sub either very close or far from the port then the excursion might change slightly due to how the cone interacts with the pressurized air inside the enclosure? 

[Sencheezy 689]

Had to make it all pretty with a ruler, don't know what it would have looked like otherwise haha

 

Ok so slot port enclosure A would have a slightly higher SPL than B due to the increased pressure for air to be pushed and pulled through the port? My initial thoughts were that that would be the case. 

 

I understand that subs up and port back or whatever variation depends on the vehicle, but what about the placement of subs relative to the slot port if the port and sub directions are not changed? Still centered? Because I would think that if you had the sub either very close or far from the port then the excursion might change slightly due to how the cone interacts with the pressurized air inside the enclosure? 

 

This sucks man, but I hate to tell you, lol. EVERY sub/port orientation will alter SPL response per vehicle. There is no clear cut way I can tell you, or anybody tell you, the best way. Hell, it can even change on the frequency played. It's just too many variation that NO software will be able to tell you. There is no formula that tells you an equation or algorithm that Subwoofer enclosure design #376 is the best enclosure for a 1997 Toyota four door Camry. 

[Quentin Jarrell 671]

You will never hear the difference but you want the sub as close to the vent mouth as possible and as far away from the vent end as possible.  Having the driver and vent next to each other also normally puts them the same distance form you.  This causes superposition making the system louder.  By having the two say on different sides of the box it is possible they would be different distances from you causing superposition to cancel the sound waves to some degree making the system not as loud.  As far as the baffle is concerned ideally you want it non symmetrical, again anything symmetrical can increase superposition.  Depending on what your trying to do this can be good or bad.

 

For the most part the only thing to concern yourself with is to try to keep the sub from the end of the vent so it doesnt prematurely unload.  

[Rail 0]

You will never hear the difference but you want the sub as close to the vent mouth as possible and as far away from the vent end as possible.  Having the driver and vent next to each other also normally puts them the same distance form you.  This causes superposition making the system louder.  By having the two say on different sides of the box it is possible they would be different distances from you causing superposition to cancel the sound waves to some degree making the system not as loud.  As far as the baffle is concerned ideally you want it non symmetrical, again anything symmetrical can increase superposition.  Depending on what your trying to do this can be good or bad.

 

For the most part the only thing to concern yourself with is to try to keep the sub from the end of the vent so it doesnt prematurely unload.  

Alright that clears it up a lot, thanks both of you guys! Makes sense now that its explained.

[1two3 16]

You will never hear the difference but you want the sub as close to the vent mouth as possible and as far away from the vent end as possible.  Having the driver and vent next to each other also normally puts them the same distance form you.  This causes superposition making the system louder.  By having the two say on different sides of the box it is possible they would be different distances from you causing superposition to cancel the sound waves to some degree making the system not as loud.  As far as the baffle is concerned ideally you want it non symmetrical, again anything symmetrical can increase superposition.  Depending on what your trying to do this can be good or bad.

 

For the most part the only thing to concern yourself with is to try to keep the sub from the end of the vent so it doesnt prematurely unload.  

 

by end of the vent do you mean were the port begins/ends INSIDE the box or the opening visible from outside?

 

im asuming inside i just want to be sure though

[lithium 358]

 

You will never hear the difference but you want the sub as close to the vent mouth as possible and as far away from the vent end as possible.  Having the driver and vent next to each other also normally puts them the same distance form you.  This causes superposition making the system louder.  By having the two say on different sides of the box it is possible they would be different distances from you causing superposition to cancel the sound waves to some degree making the system not as loud.  As far as the baffle is concerned ideally you want it non symmetrical, again anything symmetrical can increase superposition.  Depending on what your trying to do this can be good or bad.

 

For the most part the only thing to concern yourself with is to try to keep the sub from the end of the vent so it doesnt prematurely unload.  

 

by end of the vent do you mean were the port begins/ends INSIDE the box or the opening visible from outside?

 

im asuming inside i just want to be sure though

 

yes

[STS2013 0]

So how far away from a sub would an aero port internal opening have to be to avoid premature unloading?