Sub flapping sound

[Jglaser]

So I have my two alpine type r 12 in a ported box under my back seat with 1.70 cubic feet of air space per side tuned to 36 hertz and I'm having this weird sound comin from the port like a flapping sound it sounds like I put a piece of paper in front of the vent it's not too noticeable but on lower freq you can hear it bad can't figure it out looked at sub it's not blown surrond was coming off reglued still making the sound is the port loose or is it maybe port noise if you could help me figure it out that would be great

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[blazian87 10+ year member]

So I have my two alpine type r 12 in a ported box under my back seat with 1.70 cubic feet of air space per side tuned to 36 hertz and I'm having this weird sound comin from the port like a flapping sound it sounds like I put a piece of paper in front of the vent it's not too noticeable but on lower freq you can hear it bad can't figure it out looked at sub it's not blown surrond was coming off reglued still making the sound is the port loose or is it maybe port noise if you could help me figure it out that would be great

Maybe your subsonic filter is too low or not on.. Try setting it around 27hz or higher and see what that does. If it's not that, then maybe your port is not wide enough.

 

[Jglaser]

Subsonic is at 25 it's a 2" port is that too small

 

[quakerroatmeal 10+ year member]

Port noise caused by port being too small? Is this a prefab box?

 

[Jglaser]

It was originally a sealed prefab with quite a bit of airspace 1.75 per sub to be exact so I put my own port in tuned to 38 hrtz using pvc

 

[CSCStang]

It was originally a sealed prefab with quite a bit of airspace 1.75 per sub to be exact so I put my own port in tuned to 38 hrtz using pvc

Shat size pvc? Is it flared? Def port noise....

 

[Jeffdachef 5,000+ posts]

Subsonic is at 25 it's a 2" port is that too small

I Already said in the other thread that you have a horribly undersized port setup. List your max dimensions in Height, depth and width so we can even recommend the proper size since I HIGHLY DOUBT ANY PREFAB WILL BE THAT big.

You might be doing your cubic feet calculations completely wrong too. We can recommend whatever port size all we want but it will be inaccurate if your 1.7 cubic feet per side claim is inaccurate because in the other thread you claimed 1.53. No more guessing, use tape measurements and measure the box and give us the 3 measurements for your dimensions.

Your port air velocity is through the roof. You are losing both output and having horrible port noise.

PICTURES WOULD HELP TOO

BTW you can bump threads up instead of making a new one.

Answer this checklist if you want any real help.

1: box dimenions in Height x Width x Depth

2: max trunk dimensions in Height x Width x Depth

3: is your box a seperate chamber with a divider and using a 2 inch round port in each side?

4: Are your ports even flared?

 

[Jglaser]

Length 51" depth 13.5" broth 13.75" divided by 2" 2" port will post pics in a little

 

---------- Post added at 08:09 AM ---------- Previous post was at 08:08 AM ----------

 

I have no trunk it's in my 2001 chevy Silverado that is the max demensions of the back seat

 

[Jglaser]

And yes it's flared

 

[Jeffdachef 5,000+ posts]

Length 51" depth 13.5" broth 13.75" divided by 2" 2" port will post pics in a little 

---------- Post added at 08:09 AM ---------- Previous post was at 08:08 AM ----------

 

I have no trunk it's in my 2001 chevy Silverado that is the max demensions of the back seat

Cool, ran the numbers, you need at least a 4 inch port on both sides. Im guessing this is side ported with the port firing to the right and left correct?

If you can find it, a 5 inch port will be a lot better but 4 is the minimum.

 

[Jglaser]

Front port because the subs are downfiring I can fit a 4" what length

 

[Jeffdachef 5,000+ posts]

Front port because the subs are downfiring I can fit a 4" what length

you'd want the port to load(reflect) off a wall if possible or else you'll lose a lot of output. If there is no room, get elbow bends put the port on top of the box and have it bend towards the sides and have the port load off the sidewall. Each 4" port should be 9 to 14 inches long, which will be 37.5hz down to 32hz The longer it is, the lower the tuning, which one you choose would depend on your musical preferences.

 

[Jglaser]

I'll get back with you if it works

 

[Jglaser]

Fixed it

 

[Jeffdachef 5,000+ posts]

Fixed it

how does it sound now?