Where to place the port (part 2)

[carshateme]

Getting 2 12 level 3 DC subs. Got a box designed out for them that fits the volume perfectly and has a smallish port.

The design I made has 2 layers on the top part (I don't know if that's necessarily but I heard it's best to reinforce the top plate since they take the most beating...but if not.. It'll take less work off my shoulder.)

Board being used is 3/4 MDF board. Port size 8x3x15 Box size 30x13x19
Suggested ported box for these subs are 1.5 cubic feet per sub, so the total volume is about 3.2 (the speaker displacement is .15)

Subs will be pointed up towards my glass and the port will be pointed toward my truck lock.
The box is tuned to 32 hz

Xray



Normal


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[weltersys]

Other than the port is too small for high power use, and appears too close to one wall, nothing wrong with the placement, 32 Hz is completely omnidirectional.
Using four or six triangular ports on the front panel would probably allow the same tuning with more port area.

[dangus]

Chunks of ABS sewer pipe are easier to adjust the length of. With a router circle guide and patience (make trial cuts on scrap MDF first to get the size right), you can cut the holes precisely enough for a friction fit. Optionally, cut the same diam hole through some scraps and glue those on the inside for more support. With a right-angle screwdriver you could put a screw or two through the inside of the port to lock it in place.

I guess the top piece of your duct could be just screwed in place, so you could remove it to adjust the length of the port. Or just don't glue the bottom pieces to the floor, so you can remove the whole duct to trim the length.

[DrDyna]

Originally Posted by dangus

Chunks of ABS sewer pipe are easier to adjust the length of. With a router circle guide and patience (make trial cuts on scrap MDF first to get the size right), you can cut the holes precisely enough for a friction fit.

This is exactly what I do and it works wonderfully, except I use a cheap hole saw bit for my cordless drill.

[carshateme]

So you guys are recommending a circular port..instead of a slot port.

[DrDyna]

Originally Posted by carshateme

So you guys are recommending a circular port..instead of a slot port.

If it works easier. As far as I understand, the only thing that's important is the volume of the port, but I could be mistaken.

[carshateme]

I don't know, I'm used to doing sealed boxes so this port stuff is new to me...I may just add 2 slot ports about 2 " in width and 8.5" high and 16" in length...leaving a 2 " gap for the port end to wall. Slot ports to me, seem easier. I would either put the ports on the side of the box (facing the trunk) or the bottom part

[weltersys]

Originally Posted by carshateme

So you guys are recommending a circular port..instead of a slot port.

This guy is recommending triangular ports. Slot ports and triangular and corner ports tune lower than equivalent area circular ports.

Large ports are needed for high excursion, a small port "blows".
Large ports reduce cabinet volume, catch 22.
Triangular front ports optimize the port area available.
Best to make the ports too long and reduce them to the optimum tuning.

Art

[carshateme]

Ah thank you for the picture, I didn't know what he was talking about...now I gotta go look for a triangular port calculator.

Only problem with that is that I'm sure the triangle ports have to be on the faceplate where the subs are right? If that is so..it isn't going to work. I need to have my ports pointed to my trunk. and my subs are too big to fit on the side.

[weltersys]

Originally Posted by carshateme

Ah thank you for the picture, I didn't know what he was talking about...now I gotta go look for a triangular port calculator.

Only problem with that is that I'm sure the triangle ports have to be on the faceplate where the subs are right? If that is so..it isn't going to work. I need to have my ports pointed to my trunk. and my subs are too big to fit on the side.

Why do you "need" the ports pointed to your trunk?
Is that where you like to listen to your sub?

Port calculators only get you so far, if you want to "get it right", you will need to measure excursion (it will be at minimum at the Fb) and adjust port length.