Box i built sounds like da fudge

[skylineTT 10+ year member]

Well I built a box using RE box calc as always (they usually turn out sounding alright) and to achieve the tune I wanted, it called for a 28" port length in the back.. well the box wasnt wide enough for that so I took length off of the end of the port and glued it to the wall with the port width being the distance from the port to the wall.. you can see from the pics.. anyways, I figured that the port length would still be the same but just in a diff configuration and area was the same so tuning shouldnt suffer. well it did! seems to be tuned much higher than I aimed. I also used an FI X in the box which needs about .5 cubes more than what the box offers (didn't know at the time). anybody see any design flaws in the box or is it just that the sub wants a higher freq? thanks

Calculated box. you can see the port is too long so i cut the end and placed it forward

built box

18" of port area btw

Click to read more...

 

[THATpurpleKUSH 5,000+ posts]

Was it a 12inch speaker that was used? If so that box is too small, needs 45s in the corners and by adding the 2nd port wall that comes in from the side, that ate into your airspace and lowered it even more.

Dont use the RE box calc, it is very inaccurate

 

[CAT MAN 5,000+ posts]

because re calc is terrible

 

[skylineTT 10+ year member]

It was a used 12 in fact.. lol it has worked well on 3 other boxes i built. what do you all use besides math? would an 8 sound better in here?

 

[THATpurpleKUSH 5,000+ posts]

I would try a 10 first, then an 8. The size is about perfect for a 10 and little on the large side for an 8. If you give exact dimensions of what you have, I can give you a final volume and tune, but it looks close to 1 cube tuned in 32-34 range.

 

[skylineTT 10+ year member]

well the box is made out of .75, measures 24 wide, 13.5 high, and 12 deep with 1.5" port width. it is supposedly 1.2 cubes at 30hz but it doesn't play like it is. the sub displacement would subtract from that a little too, and the way i configured the port might have stolen some area from that unless the box calc factored that in.

 

[pro-rabbit 5,000+ posts]

1.2 ported for a 12"? What sub are you trying to use..also that port is hell thing...not a good thing.

 

[skylineTT 10+ year member]

haha it is an FI X i had laying around. the wood was also laying around so i didnt design it for any specific speaker. it was the biggest and lowest tuned box i could build with the little amount of wood I had. all of them were 12" by 8ft strips too.

 

[double 07 10+ year member]

add a couple more boards and you will have a T-Line..........sorry I couldnt resist.....left off my LOL

 

[pro-rabbit 5,000+ posts]

add a couple more boards and you will have a T-Line......

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[THATpurpleKUSH 5,000+ posts]

Well I'm not the greatest at slot port calculation but heres what I came up with

24x12x13.5 overall dimensions = 2835cubic inches

subtract port displacement of 1080 cubic inches

leaves you with 1755cubic inches divide by 1728 = 1.0156 cu/ft

figure around .1cu/ft for sub displacement so about .9cu/ft

total port length is 42.25inches, combined with the port area and volume comes out to about 34.3hz tune

 

[THATpurpleKUSH 5,000+ posts]

The reason it raised it is because the added piece cut into the airspace and decreased it and the length added was not enough to maintain the same tune after the volume was decreased.

 

[skylineTT 10+ year member]

yeah i figured, just didn't know if RE's calc considered the entire length to be internal or not. so .9 at 34-35? .. looks like 8" city

 

[THATpurpleKUSH 5,000+ posts]

Yea depending on the driver an 8 would work

 

[VWBobby 10+ year member]

Definitely looks longer than a 40-42" port in there.....just from looking at it. The extra board decreased your net volume (took up space) so that raised the tuning a lot higher than your port calculation.

Use WinISD if you want a better calculator. I'm sure there's better ones out there, but this is what I use in a pinch. I just take the calc for a rectangle port and adapt it for use as an L-port.

LinearTeam