Alpine box is wierd

[Dewayne89]

Trying to build box for alpine swr-1542d. This is a 15 type r. Manual gives box dimension that include a 1.5 inch wide slot port for starters... Wierd. Anyways their suggested enclosure is 3cubes tuned to 27 with 22.5 inches of port area 7.46 per foot according to my calculations. Somehow I don't think that is gonna sound good. Input anyone?

[Triticum Agricolam]

Alpine gives really sub-optimal port recommendations in their manuals. Probably to make the box as small as possible. The way they have it the port doesn't have enough area IMO and has a really high aspect ratio as well, which doesn't help anything either.

Assuming you want to keep box volume and tuning the same, which should be fine, I'd widen the port from 1.5" to 2.5". It will have to be a good bit longer to keep tuning the same (increase it to about 34"). It still will have a higher aspect ratio than I would like, but it should have enough port area to make up for that. This recommendation is assuming you are going to be putting RMS power to the sub, if you are going to be putting much more than that, let me know.

[Dewayne89]

Thanks I'm not limited to 3 cubes and I think I'll tune it around 32-33. I came up with a 3" by15.5" port in a 3 cube box is right at 15 inches per foot. I'm open to any suggestions I just figure it needs to be somewhere in that range. I can do up to 1200 watts rms but I'll probably turn it down a bit.

[Triticum Agricolam]

Thanks I'm not limited to 3 cubes and I think I'll tune it around 32-33. I came up with a 3" by15.5" port in a 3 cube box is right at 15 inches per foot. I'm open to any suggestions I just figure it needs to be somewhere in that range. I can do up to 1200 watts rms but I'll probably turn it down a bit.

That should work just fine.

[Dewayne89]

Aspect ratio refers to the width and height of port?

3 to1 is ideal? Tried to read up on my own not a lot to read on the subject.

[Triticum Agricolam]

1:1 is ideal, though as long as you are under 5:1 there isn't much performance difference. Above 5:1 I'd increase port area and I try to never go above 8:1.

[Troy Ellenburg]

Aspect ratio refers to the width and height of port?

3 to1 is ideal? Tried to read up on my own not a lot to read on the subject.

Aspect ratio OF the port is H x W, yes.

Reason being that 1:1 is ideal, since you said you researched it and couldn't find anything...:

squares(1:1) have less perimeter for the same area than any rectangle:

Area: Perimeter:

3x15.5=46.5, 3+3+15.5+15.5=37

6x7.75=46.5 6+6+7.75+7.75=27.5

that is a 9.5 difference, and that will be throughout the port, so 34 inches for port length is a total of 323 sq inches!

The more perimeter the air has to travel on, the more resistance there will be. In this example, the almost square port is 30% more efficient.

Granted MDF is smooth af, and can be sanded making it baby-bottom smooth, but efficiency is efficiency!

For that reason I will try to keep all my ports below 2:1, and square if I can.

FYI: Aero ports are the most efficient way to go(circle are more efficient that squares, sorry Kicker), but do not fit every application.

-Troy

[Dewayne89]

Thanks guys amazing how there is always more to be learned about speaker boxes.