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Is this a functional ported box?

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Umbra

Umbra

Hobbyist & CA Tenderfoot
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Long Island, NY
The other day I was buying a AQ 15" sub on Craigslist and the guy also had this homemade box:

01616_112kdWZj7di_600x450.jpg


I'm not sure if he ever ran the AQ or any other sub in it. He told me it originally housed a 15" woofer and a horn tweeter and it was later modified for sub use. I could tell it was way too small to run a 15 ported in, but I bought it because I thought I could run a 12 or maybe the 15 sealed in it. Before you knock it, it's solidly built and I paid $10 for it, but yes, it does look like ***.

Anyway, I bought it and later put the dimensions into a calculator and figured it should be tuned to around 34Hz:

The box is 14" deep, 15.5" high, and 24" wide. About 2.2 cubes taking into account the wood thickness (but not the port or woofer displacement)

The port is 3.5" x 3.5" and extends 10" into the box.

I made an adapter out of 3/4" MDF so it fits a 12 and I flared the left and right sides of the port with cut PVC. I believe the extra length brings the tuning down a bit. I don't actually know what the flares do, aside from possibly prevent port noise.

I've never had a ported box before, but it sounds pretty good to me. The sub in it is a Memphis Mojo PR, which I believe is more suited for a sealed box. It isn't crazy loud on 250W, but it definitely boosts the low end with only a little bit of SQ loss.

Without any further digression, let me just ask: is that a proper port? Most slot ports I've seen have at least one angle and often run along the back. Is this 3.5" square column a functional port, or am I retarded?

Thanks

Click to read more...
 
The port can be straight. Is the 10" length from the opening of the port to the rear of the box, or just until the actual column stops? With ports, if your port is 10" long but it's 3.5" from the rear wall, that will act like an extension to the port, so it's more like a 13.5" port (roughly). This would drop the tuning a bit. As is with a 2 cube box and the port like how you're describing, you're looking at around a 32-36hz tuning. That's not very much port area though.

 
Only at very low SPL levels. Much over 100 watts and the port isn't doing it's job anymore. It should be tuned in the mid 30's somewhere, but the port is so small it can't move much air. It's about the same amount of port as a 4inch aero. Honestly, it'd work better with a 10 or even an 8. For a low power 12 though it's better than nothing, but not ideal.

Most ports have turns because once you have enough port area to match the subs displacement capabiltiies, the port has to be longer to maintain the same tuning. Ideally ports would be have adequate port areas without turns, but that often wont' fit in a box that fits in the car.

 
Yes, a port can be a square column like that. That's probably not enough port area though. Honestly, you maybe be better off cutting out most of the front panel (including port) and running a 12" sealed in that enclosure.

 
The port can be straight. Is the 10" length from the opening of the port to the rear of the box, or just until the actual column stops? With ports, if your port is 10" long but it's 3.5" from the rear wall, that will act like an extension to the port, so it's more like a 13.5" port (roughly). This would drop the tuning a bit. As is with a 2 cube box and the port like how you're describing, you're looking at around a 32-36hz tuning. That's not very much port area though.
Click to expand...
It's 10" long and then stops. There's another 3.25" between that and the back wall. Thanks for the information, I had no idea it would do that.

Only at very low SPL levels. Much over 100 watts and the port isn't doing it's job anymore. It should be tuned in the mid 30's somewhere, but the port is so small it can't move much air. It's about the same amount of port as a 4inch aero. Honestly, it'd work better with a 10 or even an 8. For a low power 12 though it's better than nothing, but not ideal.
Most ports have turns because once you have enough port area to match the subs displacement capabiltiies, the port has to be longer to maintain the same tuning. Ideally ports would be have adequate port areas without turns, but that often wont' fit in a box that fits in the car.
Click to expand...
Since I'm listening to a low of music with long drawn out basslines I'm probably over 100W most of the time. I have a 250W 10" and a 400W 8" I could play around with. I'll just make another adapter plate. I take it that's why people use aeroports that extend outside the box.
Yes, a port can be a square column like that. That's probably not enough port area though. Honestly, you maybe be better off cutting out most of the front panel (including port) and running a 12" sealed in that enclosure.
Click to expand...
That's a good option. I have a matching sub, so if I end up going sealed I'll most likely do that pair.
Thanks for the info. I'll play with it some more tomorrow. I'll try the smaller subs in there first

 
It's 10" long and then stops. There's another 3.25" between that and the back wall. Thanks for the information, I had no idea it would do that.

Since I'm listening to a low of music with long drawn out basslines I'm probably over 100W most of the time. I have a 250W 10" and a 400W 8" I could play around with. I'll just make another adapter plate. I take it that's why people use aeroports that extend outside the box.

That's a good option. I have a matching sub, so if I end up going sealed I'll most likely do that pair.

Thanks for the info. I'll play with it some more tomorrow. I'll try the smaller subs in there first
Click to expand...
If you have a 10", throw a baffle and a couple of 4" aero's (or PVC) ports and it should be right around the right size. Little small for most 12's but should give you a little under 2cf which works for most 10's ported I think.

 
The port can be straight. Is the 10" length from the opening of the port to the rear of the box, or just until the actual column stops? With ports, if your port is 10" long but it's 3.5" from the rear wall, that will act like an extension to the port, so it's more like a 13.5" port (roughly). This would drop the tuning a bit. As is with a 2 cube box and the port like how you're describing, you're looking at around a 32-36hz tuning. That's not very much port area though.
Click to expand...
I read somewhere today ideally you'd want the distance between the end of the port and the back wall at least the length of the port diameter. I did a bunch of research and crunched a bunch of numbers and right now my plan is to widen the box to get to ~2.75 cubes (I'm going to try to add to it, but I may just scrap it and start fresh), put two 4" tubes in it, and drop a pair of 10s in it. I'm playing with the numbers in Torres, but I can't follow that rule and get the tuning down to ~35Hz. Then I thought about what you said.

I understand diameter, port area, and length and how it affects tuning, but not much beyond that. I'm looking for some trick to extend the length without it sounding terrible. I don't have room to have any of the port be external because I've only got about 4" between the box and the trunk lid, so I either need to somehow manipulate the effect you mentioned to my advantage, put 90 degree couplers on the pipe either inside or outside the box, or give up the idea of using aeros and design a slotted box.

Here's what I've got so far:

kcKTbmc.jpg


If anyone has any ideas or notices anything amiss with this design please chime in.

 
That box is total crap. How he managed to squeeze a 15 in that mounting hole w/o hitting the sides is beyond me and judging byt the pics. Gotta love the white caulking too....I'm very picky when it comes to boxes....and when I make them. Seeing that tells me they put it together quicikly, didn't care as long as it made bass.

A properly well made built box would have wood glue and caulking inside, unseen. Love the looks of @CSCStang boxes. That's a person that takes care in his crafsmanship.
 
[quote name='boomintahoe']That box is total crap. How he managed to squeeze a 15 in that mounting hole w/o hitting the sides is beyond me and judging byt the pics. Gotta love the white caulking too....I'm very picky when it comes to boxes....and when I make them. Seeing that tells me they put it together quicikly, didn't care as long as it made bass.

A properly well made built box would have wood glue and caulking inside, unseen. Love the looks of @CSCStang boxes. That's a person that takes care in his crafsmanship.[/QUOTE]

Thank you, sir.
 
I read somewhere today ideally you'd want the distance between the end of the port and the back wall at least the length of the port diameter. I did a bunch of research and crunched a bunch of numbers and right now my plan is to widen the box to get to ~2.75 cubes (I'm going to try to add to it, but I may just scrap it and start fresh), put two 4" tubes in it, and drop a pair of 10s in it. I'm playing with the numbers in Torres, but I can't follow that rule and get the tuning down to ~35Hz. Then I thought about what you said.
I understand diameter, port area, and length and how it affects tuning, but not much beyond that. I'm looking for some trick to extend the length without it sounding terrible. I don't have room to have any of the port be external because I've only got about 4" between the box and the trunk lid, so I either need to somehow manipulate the effect you mentioned to my advantage, put 90 degree couplers on the pipe either inside or outside the box, or give up the idea of using aeros and design a slotted box.

Here's what I've got so far:

kcKTbmc.jpg


If anyone has any ideas or notices anything amiss with this design please chime in.
Click to expand...
Just start from scratch. It's more trouble than it's worth to try to Frankenstein that into something worth using. The enclosure is a huge part of a subwoofer system and getting the right sound. You shouldn't skimp there if at all possible.

 
I found a resource that addressed some of my questions: Port Flares

Right now the plan is to have the ports towards the center at the bottom and the subs above them and off to each side. The ports will need a 90 degree gradual bend and will turn away from each other as it gets towards the back.

 
Alright, I've got a design and I'm pretty sure it should work out well enough, but I have two concerns:

3LxDA4V.jpg


The second view is an overhead and the first is head-on. One port is above the other and they turn in opposite directions.

I know you're supposed to keep port openings away from walls. Is that only when the port is facing the wall, or should that also apply when the port is alongside it?

Is the opening inside the box in an okay spot relative to the subs? I don't know much about the guidelines here. I think it's supposed to be out of the way.

I'm sorry the MS paint sketch is ****. Hopefully you get a chuckle of it.

These are the only two potential issues I see. If you can lend some insight, please do, otherwise I'm going to go ahead and build it tomorrow.

 
I would go with a wood port....utilizing the front baffle as part of the port area. Tricky part is figuring out how much port area those need and then a design from there. Rectangle skinny port might work....then the bends with the wood.

 
Alright, I've got a design and I'm pretty sure it should work out well enough, but I have two concerns:
3LxDA4V.jpg


The second view is an overhead and the first is head-on. One port is above the other and they turn in opposite directions.

I know you're supposed to keep port openings away from walls. Is that only when the port is facing the wall, or should that also apply when the port is alongside it?

Is the opening inside the box in an okay spot relative to the subs? I don't know much about the guidelines here. I think it's supposed to be out of the way.

I'm sorry the MS paint sketch is ****. Hopefully you get a chuckle of it.

These are the only two potential issues I see. If you can lend some insight, please do, otherwise I'm going to go ahead and build it tomorrow.
Click to expand...
having elbows on the port kinda defeats the purpose of having aeroports. Either go side ported or go slot ported.

 
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Umbra

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