How many cubic ft is my box, what is my tuning? Box for 3 Sundown SA 8s...

[Parker22 10+ year member]

I just had a custom box made for 3 Sundown SA 8 v.3s. Sundown reccomends .5-.75cu ft per sub, I was wanting to be closer to the .75 I am also hoping the tuning is 33hz.... (.08 per sub displacement)

The INTERIOR dimensions of my box are 28.5" (width) X 15.5" (height) X 9.5" (depth). THESE are the INTERIOR dimensions. The exterior dimensions are obviously more but due to the inset on the sides of the box I have chosen not to list them.

The two ports are 3" flared aero ports the total length of the port (including what is not part of the interior space of the box) is 11" this is what confuses me on what my NET cubic feet is as well as my tuning. My calculations tell me the box is right around 2.1 NET cubes after ports and subs, but I am not sure if I am right on the ports, and I have no idea on the tuning...

Attached is a picture. Any input I would greatly appreciate.

Click to read more...

 

[THATpurpleKUSH 5,000+ posts]

I came up with about 2.08cf

Edit: As far as tuning goes- subtract 1 inch from your total port length because of the flares, that number is your port length- 10". Divide the net volume by the number of ports. Use that number as your airspace to calculate what tuning corresponds with that port length of 10" with a 3" round port.

The magic # is 38.75hz

 

[pw91686 10+ year member]

tuning is around 38-39 based on precision aero ports calculator

 

[pw91686 10+ year member]

I came up with about 2.08cf
Edit: As far as tuning goes- subtract 1 inch from your total port length because of the flares, that number is your port length- 10". Divide the net volume by the number of ports. Use that number as your airspace to calculate what tuning corresponds with that port length of 10" with a 3" round port.

The magic # is 38.75hz

beat me to it

 

[Parker22 10+ year member]

So if I want to change the tuning to around 33 Hz what can I do with the ports? I will probably try as is then buy 2 new aero ports and make them the size I want...

 

[THATpurpleKUSH 5,000+ posts]

So if I want to change the tuning to around 33 Hz what can I do with the ports? I will probably try as is then buy 2 new aero ports and make them the size I want...

You can go up to 14 3/4 total port length which would yield a tune of about 34hz and 2.06cf. Assuming 3/4 thick material that leaves a distance of 1/2 the port diameter between the end of the flare and the wall of the box. That is the shortest distance I would recommend before running into issues

 

[Boomin_tahoe 5,000+ posts]

Yikes....I'd be a little upset knowing I shelled out my hard earned $$ for a box and turned out to be something I didn't want. Did you have a car audio shop build it for ya or was it someone private you enlisted thru CL or Offerup, or a box builder that does just that in his garage? IF it was a car audio shop, I'd take it back and try to get a refund, since they didn't build it to your standards.

Couple of choices I guess, try and get some longer pvc lengths for what Thatpurple kush suggested and use it even tho the lows aren't gonna be as strong as a lower tuned enclosure. But, the upper bass will be loud,...or try and get a refund it, or if that's not possible, try and sell it....and start all over.

 

[Parker22 10+ year member]

You can go up to 14 3/4 total port length which would yield a tune of about 34hz and 2.06cf. Assuming 3/4 thick material that leaves a distance of 1/2 the port diameter between the end of the flare and the wall of the box. That is the shortest distance I would recommend before running into issues

Any harm in just cutting what I have and adding on some PVC in between?

Yes wood is 3/4. That would put the flare of the port only 3/4" away from the wall of the box....

 

[Parker22 10+ year member]

Yikes....I'd be a little upset knowing I shelled out my hard earned $$ for a box and turned out to be something I didn't want. Did you have a car audio shop build it for ya or was it someone private you enlisted thru CL or Offerup, or a box builder that does just that in his garage? IF it was a car audio shop, I'd take it back and try to get a refund, since they didn't build it to your standards.
Couple of choices I guess, try and get some longer pvc lengths for what Thatpurple kush suggested and use it even tho the lows aren't gonna be as strong as a lower tuned enclosure. But, the upper bass will be loud,...or try and get a refund it, or if that's not possible, try and sell it....and start all over.

I am pretty upset.... I'll contact the builder Monday but shipping the box back will be a hassle and if it something I can fix pretty easily i would rather just fix it myself. 32-35 Hz and I'm happy. I told the builder 33.....

 

[Parker22 10+ year member]

I could buy 4 of these:

https://www.parts-express.com/precision-port-psp-3rg-3-connecting-ring-for-port-tube--268-372

And one of these:

https://www.parts-express.com/precision-port-psp-3tb-3-dia-x-12-long-port-tube--268-374

If I add 3 inches to each port that should get me to 14" port length and I would have 1.5" between the end of the flare and the bottom wall of the box. This should get me between 34-35 Hz which I can live with. Sundown recommends 35Hz anyway.... I will try this.

If I'm not happy I will definitely be building my next box myself... I'm already contemplating 3 X8 v.3's (for later on down the road) when they come out on a T2500bdcp if I get back into bass like I used to be. If I ever do this I will have to build a bigger box, I will go for a net of 3 cubes.

 

[THATpurpleKUSH 5,000+ posts]

Any harm in just cutting what I have and adding on some PVC in between?
Yes wood is 3/4. That would put the flare of the port only 3/4" away from the wall of the box....

PVC might have a different od/id and might not fit the aero port parts, idk. At the minimum you want a distance of half the width of the port between the wall and flare.

I am pretty upset.... I'll contact the builder Monday but shipping the box back will be a hassle and if it something I can fix pretty easily i would rather just fix it myself. 32-35 Hz and I'm happy. I told the builder 33.....

I would definitely contact the builder if you wanted 33hz and ended up with almost 39hz. I would ask for some sort of reimbursement for it not being correct.

 

[Parker22 10+ year member]

PVC might have a different od/id and might not fit the aero port parts, idk. At the minimum you want a distance of half the width of the port between the wall and flare.


I would definitely contact the builder if you wanted 33hz and ended up with almost 39hz. I would ask for some sort of reimbursement for it not being correct.

Monday I will call him and explain what is wrong and see what he is willing to do. For now I will just make the port 14" which allows for the minimum you distance from the wall of the box you recommend. This will still be 34-35 hz and I am happy with that.

I really appreciate the help!

 

[Boomin_tahoe 5,000+ posts]

Oh, you had a box built from another state.....hmm. I wonder how he messed it up, either didn't know, forgot, or doesn't know what he was doing. I'm a box builder myself but seasonal.