Help with box design for 4 12s

[Matt A 10+ year member]

this is probably gunna sound dumb but when designing a port for a box do you use the amount of airspace thats in the box before the port is added or the desired amount of airspace in order to find the amount of port area you need? also how long should the port be if i want to tune the box to 33hz....my desired net is 8.8-9 cubes..thank you

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[THATpurpleKUSH 5,000+ posts]

It depends on the manufacturer but slot ported boxes almost never take into consideration the port airspace, only driver displacement. Round ported boxes sometimes include the port displacement along with driver displacement but still the manufacturer always notes what is included in the owners manual. I say this based off of my 2 years experience.

 

[Vossy 10+ year member]

There's really good calcs for it, I found one that you save to your cpu... I don't remember where I found it though.

 

[SicAudio 5,000+ posts]

you go based on net volume after all displacements... including the port... you just have to chug away at it...

 

[SicAudio 5,000+ posts]

It depends on the manufacturer but slot ported boxes almost never take into consideration the port airspace, only driver displacement. Round ported boxes sometimes include the port displacement along with driver displacement but still the manufacturer always notes what is included in the owners manual. I say this based off of my 2 years experience.

if you built the enclosure for your boston G5 subs based on that I bet your tuning is alot closer to 40 than 33...

 

[pro-rabbit 5,000+ posts]

figure out your airspace wanted. Then figure out port size and length. then figure out the dispacement of the port. Add port displacement to the airspace, then add sub displacement to the airspace wanted. then build said box

 

[Matt A 10+ year member]

ok so that means that if i need to have 9 cubes after all displacements then i should base my port on the box being 9 cubes correct therefore for audioque hdc3s i take 16*9=144 as my port area correct

 

[SicAudio 5,000+ posts]

correct

then figure what the length needs to be for the tuning you want and add that cf airspace to the 9cf and thats the gross airspace you need //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[pro-rabbit 5,000+ posts]

then you need to figure out tuning and port length. If you using an L slot port, when you go to figure out the displacement of the port be sure to add the thickness of the wood (.75 or what ever size wood you are using) to the width of the port.

I may know a little about some box designs for AQ //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[akheathen Premium Member]

where did you come up with the net desired figure? is that what space you have available to fit the box? or is that the ammount of airspace you are looking to give the subs? (2.2-2.25 per sub) when you are limited to net that much, then you tweak the numbers back and forth (start with guestimations of port displacement, wall thickness, and driver displacement to get a rough internal space to go off of, then tweak them back and forth. now, if you want to start at that as your definate internal space, then that gets easier. i play off of the calculator at "the12volt.com" but there is much more i just do off my head and on paper. now, if your question is what size/length port to incorporate to that much internal space, then i would say, depending on your driver specs, 125-145sq/in port area, and 25.5-29.5. but that's just an estimate off little info. are you looking to have a box designed for you?

 

[THATpurpleKUSH 5,000+ posts]

if you built the enclosure for your boston G5 subs based on that I bet your tuning is alot closer to 40 than 33...

Actual airspace on those is about 3.8 cu/ft. Sub displacement is .12 cu/ft each and I ran external aeroports so no need to work around their displacement. The port tubes are around 14in long. I did go with a slightly bigger airspace than recommended though but tuning is within +/-1 hz of recommended.

 

[Matt A 10+ year member]

ic ic...so i want the port to be tuned to 33 hz (if u think there is a better frequency to make the 4 12s sound like 15s let me know).....how long should my port be?

 

[akheathen Premium Member]

wow, that quick post" wasn't very quick, lol

 

[SicAudio 5,000+ posts]

Actual airspace on those is about 3.8 cu/ft. Sub displacement is .12 cu/ft each and I ran external aeroports so no need to work around their displacement. The port tubes are around 14in long. I did go with a slightly bigger airspace than recommended though but tuning is within +/-1 hz of recommended.

gotcha...

 

[pro-rabbit 5,000+ posts]

9ft^3 is fairly small for 4 tuning that low