Hours of reading, and still lost on Aero port volume VS slot port volume

[eismanx 10+ year member]

IM trying to build a box for a DD9515 and im gonna be using 4 inch pvc pipes with mdf baffles on each end flared over like the aero ports.

How can 3 - 4" (37.68"^) ports at 12.2" length (according to PSP-INC.com) EQUAL up to DD's specs at 72"^ at 19" long. There's no way that the improved turbulence of 3 rounds ports can cut the volume of a slot port IN HALF, it just doesnt sound right, and if it does, i'd like someone to confirm that and maybe give me an explanation as to how.

This "baffles" me to death, lol

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[eismanx 10+ year member]

22 views and not even a yes or no or a maybe. Dont everyone speak out at once! lol

 

[subzero 5,000+ posts]

fuck that box. do a slot port box and round the corners inside. RE Enclosure Calculator

 

[Haunz 10+ year member]

Forget about port volume, or port area... that is about as usefull as trying to look at tits in a nunnery... End correction factors are readily found in any box building book; and I'd be using bassbox or winisd rather then an online calculator...

 

[eismanx 10+ year member]

fuck that box. do a slot port box and round the corners inside. RE Enclosure Calculator

That's boring, all the boxes i've built are like that.

HAUNZ- Are you effin with me? Forget about port volume and area? Isnt that sorta like sayin "oh forgot about the transmission, well just hook the driveshaft straight to the engine". I thought end correction is only used when one of your port walls is an exterior wall.

 

[amartin_72]

Tell us the power, vehicle and what you want to do with it is it for loud daily or for spl metering. cause there is a huge difference a dd tuned to 40 or more for high spl does not sound very loud on music you have to tune to 37 or lower to get it to feel loud.

 

[amartin_72]

and yes 3 4" is too small you need at least 4

 

[Wingman0121 10+ year member]

Many people have custom ports outside of the box so they can trim/lengthen it for different tuning frequencies as they desire.

Circumference of a circle is R x Pi x 2, whereas R equal radius and Pi equals 3.14.

A 4" port at 12" long will give you 2 x 3.14 x 2 x 12 = 150.72 Sq inches of surface area. Remember the flared part of the port does NOT count as part of the total length of the port.

 

[roarzorz 10+ year member]

Many people have custom ports outside of the box so they can trim/lengthen it for different tuning frequencies as they desire.
Circumference of a circle is R x Pi x 2, whereas R equal radius and Pi equals 3.14.

A 4" port at 12" long will give you 2 x 3.14 x 2 x 12 = 150.72 Sq inches of surface area. Remember the flared part of the port does NOT count as part of the total length of the port.

You have that all kinds of wrong. Circumference is the distance around a circle (circumference = pi * diameter). Area = pi * radius^2. A 4" port has 12.56" of surface area. Factoring in length gives you volume (volume = area * length). You do use the flares as total straight length of the port. Just don't measure around the curve. The calculator at Precision Sound Products works great for calculating tuning using round ports.

 

[eismanx 10+ year member]

Tell us the power, vehicle and what you want to do with it is it for loud daily or for spl metering. cause there is a huge difference a dd tuned to 40 or more for high spl does not sound very loud on music you have to tune to 37 or lower to get it to feel loud.

Thanks guys, i feel like im starting to get somewhere in this thread.

My plan is to build a middle console box for my ext. cab Silverado. It will more than likely have to go all the way to the back seat to get around 4 to 4.5 cubes NET, around 5.5 gross. Im going for a daily SQ setup, no comps. I planned on tuning between 37 - 40 Hz. I hear cabin gain on trucks and suv's is around 45, i know that plays more into SPL, but figured i'd throw that in there just in case. Sub is a dual 2 ohm, power will be coming from a MTX1501d, stable to only 2 ohms, but my research tells me that it will run at 1 ohm/1800rms if i have a stable electrical system, or i can just un-solder and remove the q240 resistor, which i dont wanna have to do. If it wont run at 1 ohm i will have to use my Sundown SAE-1000 which is stable at 1ohm/1000watts.

The only reason i am going with round flared ports is because of space issues. I recently found out that round ports take up less space. I know DD subs arent like other subs, thats why i dont trust the web calculators. I was hoping to get advice from some people that have first hand experience with my type of setup. Im gla di havent started on the box yet, because i was just gonna take a shot in the dark and use 3- 4 inch ports.