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How do you plan for 45s in port?

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Umbra

Umbra

Hobbyist & CA Tenderfoot
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Long Island, NY
I have an SA-18 that's been sitting on my floor for almost a year now. I think it deserves a solid box. I want to build a slot port box, sub up, port back (it's going in a '99 Jeep Cherokee). I've designed boxes in Torres and built them, but with 90 degree corners, nothing remotely fancy. This time I'd like to do kerfs and/or 45s in the design.

I'm having a hard time wrapping my head around going from torres to something like this:

neon_sub_enclousre.jpg


(not the sketchup design, just going from a basic L shape to one with angles)

If anyone has experience with this, what's your process? After figuring out the port dimensions, how do you plan for those 45s when making your cuts so you can keep the port width uniform?

Thanks for any assistance you might be able to provide.

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imo just guess on the length.

but for accurate measuring, measure the port length from the middle of the port.

if you get close like within 2-3" of the calculated length you will be close to your desired tuning

then i wouldnt kerf the outside edge. as you can see it adds on a ton of area for nothing.

if you want a full kerf do an aero port.

 
imo just guess on the length.but for accurate measuring, measure the port length from the middle of the port.

if you get close like within 2-3" of the calculated length you will be close to your desired tuning

then i wouldnt kerf the outside edge. as you can see it adds on a ton of area for nothing.

if you want a full kerf do an aero port.
Click to expand...
Thanks, yeah, I get how to measure the port, it's the construction part that's throwing me.

I'm not a fan of that second kerf either. It's just an image I pulled from google. I'm thinking of doing a horizontal port along the bottom. I considered doing kerfs at every corner, so it'll kind of look like an "e", but I believe they weaken the box, even when filled and sanded.

Sent from my stang5litre Edition 5.0 using Tapatalk

 
@CSCStang

You're an enclosure guru, do you have any tips on how to go from a 90 degree L to one like in the picture?

The best I've come up with so far is physically making the pieces for the regular L, making the larger corner piece some arbitrary length, then figuring out how much I have to cut away to keep the port width uniform. I'll try to guess how much volume would be taken up beforehand and figuring that into the calculations.
 
[quote name='Umbra']@CSCStang

You're an enclosure guru, do you have any tips on how to go from a 90 degree L to one like in the picture?

The best I've come up with so far is physically making the pieces for the regular L, making the larger corner piece some arbitrary length, then figuring out how much I have to cut away to keep the port width uniform. I'll try to guess how much volume would be taken up beforehand and figuring that into the calculations.[/QUOTE]
The best and easiest way to accomplish this type of turn in the corner is to draw it all out on the bottom sheet before you make any cuts. The corner 45 needs to be exaggerated (oversized) and when in place you'll measure across from the face of it, the port width at that same angle through the bend. The goal obviously is to keep the port width as uniform as possible. Hope this helps you visualize what I'm saying.

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if you go on the bottom make sure your port opening is less than 9:1 for the width to the height

If the port is long and skinny it can cause problems

 
Sub and port firing up has given me best sounding results in my Jeeps. Sub(s) up port to the side is slightly louder on the meter but not by a lot and if you don't have adequate room outside of where the port fires it won't load right so up is a lot easier.

Assuming you're 6.5-8 cube box if you are off by half a cube or even a full cube in your calculations the difference should be mostly inaudible. If you don't have an exact frequency goal for the sake of SPL competitions don't worry so much about splitting hairs on whether you're off a little bit on volume or a couple inches give or take of port length, you'll never hear the difference.

 
The best and easiest way to accomplish this type of turn in the corner is to draw it all out on the bottom sheet before you make any cuts. The corner 45 needs to be exaggerated (oversized) and when in place you'll measure across from the face of it, the port width at that same angle through the bend. The goal obviously is to keep the port width as uniform as possible. Hope this helps you visualize what I'm saying.
Sent from my SCH-I605 using Tapatalk
Click to expand...
Thank you! As silly as it sounds I didn't think to sketch it out on the bottom so the measurements are 1:1. With the pieces to scale it should be easier to flesh out.

if you go on the bottom make sure your port opening is less than 9:1 for the width to the height
If the port is long and skinny it can cause problems
Click to expand...
Thanks for the tip, gotta be wary of that port noise.

Sub and port firing up has given me best sounding results in my Jeeps. Sub(s) up port to the side is slightly louder on the meter but not by a lot and if you don't have adequate room outside of where the port fires it won't load right so up is a lot easier.
Assuming you're 6.5-8 cube box if you are off by half a cube or even a full cube in your calculations the difference should be mostly inaudible. If you don't have an exact frequency goal for the sake of SPL competitions don't worry so much about splitting hairs on whether you're off a little bit on volume or a couple inches give or take of port length, you'll never hear the difference.
Click to expand...
This is for a daily, music only, no competitions. So close is good, but I won't lose any sleep if it's off a bit. Thank for the suggestion. I've looked around for other people doing sub up port up and it's always due to a space constraint. I agree though, it'd be better than not giving the port enough space to breath. The cherokee is a small vehicle and there's not a ton of room behind the second seat, so if I don't have enough room I'll consider that. It might not be as loud, but I'm sure either way would be loud enough for music.

 
This is for a daily, music only, no competitions. So close is good, but I won't lose any sleep if it's off a bit. Thank for the suggestion. I've looked around for other people doing sub up port up and it's always due to a space constraint. I agree though, it'd be better than not giving the port enough space to breath. The cherokee is a small vehicle and there's not a ton of room behind the second seat, so if I don't have enough room I'll consider that. It might not be as loud, but I'm sure either way would be loud enough for music.
Click to expand...
I'm talking 3-4 tenths of a dB difference so totally inaudible and I've found the overall sound of port and sub(s) up quite good for music. I have had no luck subs and/or port to the rear in my Jeeps.... Every other configuration except forward (including subs to the side and port up) would be superior.

 
I'm talking 3-4 tenths of a dB difference so totally inaudible and I've found the overall sound of port and sub(s) up quite good for music. I have had no luck subs and/or port to the rear in my Jeeps.... Every other configuration except forward (including subs to the side and port up) would be superior.
Click to expand...
I'll do that then. No use learning the hard way when someone else can offer you their first-hand experience.

Was the box taller than the window line?

Sent from my stang5litre Edition 5.0 using Tapatalk

 
I'll do that then. No use learning the hard way when someone else can offer you their first-hand experience.
Was the box taller than the window line?

Sent from my stang5litre Edition 5.0 using Tapatalk
Click to expand...
Some yes some no. As you get too close to the ceiling you run into the same loading issues that you'd have with any port location but you should not have to be more than a couple inches above the window line to come up with adequate volume for the SA18

 
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