How to measure l port length.

[ManzKea 152]

What's up guys so I started construction and completed my box for 2 12's. Gonna be used for dss ethos 12. Port is 4x20 and box net was 5.99. I used 12volt to see how long I need it for 32hz. It said 27.75 but I rounded up to 28. But I wasn't too sure on how to go about it since it's gonna have 2 bends. I researched it and it sounds super confusing, some saying gotta have the correction part at the end. But I found some that said just measure up the middle so that's what I did to achieve 28"

Could you guys she'd some info on if it's correct. If not, could you tell me what frequency I'm at. Alright thanks guys

[Triticum Agricolam 15]

For ports with bends in them you measure down the middle of the port.  However when you calculate your port length you need to use your net internal volume, so you have to subtract out the space your port takes up to get that number.  If you didn't do that you are going to be tuned higher than you intend.

 

I hope there is glue under all the silicone you used.

[ManzKea 152]

Yes there is. Gorilla glue. I used 12volt it says enter my width and height and the net volume and it calculates the length

[ManzKea 152]

The length is affected by the volume, how am I suppose to know the length and subtract it from the net volume first?

[///M5 2,833]

Rudimentary Geometry and Algebra.

Volume Box Net = Volume Box Gross - Port Volume

Volume of box is LxWxH

Not sure how much easier that could be...

[ManzKea 152]

For ports with bends in them you measure down the middle of the port.  However when you calculate your port length you need to use your net internal volume, so you have to subtract out the space your port takes up to get that number.  If you didn't do that you are going to be tuned higher than you intend.

 

I hope there is glue under all the silicone you used.

"The way he worded it was confusing and I believe wrong.

When you calculate your port length, You need to use your net internal volume, so you have to subtract out the space your port takes up to get that number."

But yea m5 I know that's how you find the met volume of the box with the port being displaced

[antoinez28 62]

Rudimentary Geometry and Algebra.

Volume Box Net = Volume Box Gross - Port Volume

Volume of box is LxWxH

Not sure how much easier that could be...

Your just a book of car audio...

[ManzKea 152]

Rudimentary Geometry and Algebra.

Volume Box Net = Volume Box Gross - Port Volume

Volume of box is LxWxH

Not sure how much easier that could be...

Your just a book of car audio...

What's up bro you running the ethos?

[ohio45113 24]

For ports with bends in them you measure down the middle of the port. However when you calculate your port length you need to use your net internal volume, so you have to subtract out the space your port takes up to get that number. If you didn't do that you are going to be tuned higher than you intend.

I hope there is glue under all the silicone you used.

"The way he worded it was confusing and I believe wrong.

When you calculate your port length, You need to use your net internal volume, so you have to subtract out the space your port takes up to get that number."

But yea m5 I know that's how you find the met volume of the box with the port being displaced

What did he say was wrong?

[ManzKea 152]

He said you gotta use the net volume. So, minus the volume of the port first to get that number.

But how would you minutes the port if you don't know the length? Because to get the length, doesn't that depend on the volume of the box? A 40square inch port 25inches long may be 32hz in a 3cubic ft box but in 5cubic foot box it won't be the same frequency.

[Triticum Agricolam 15]

He said you gotta use the net volume. So, minus the volume of the port first to get that number.

But how would you minutes the port if you don't know the length? Because to get the length, doesn't that depend on the volume of the box? A 40square inch port 25inches long may be 32hz in a 3cubic ft box but in 5cubic foot box it won't be the same frequency.

Yup, you have to use net volume.  I know it feels like you are trying to hit a moving target with your port dimensions.  This is the problem with designing/building the exterior of the box first and then trying to fit everything in.  Its a lot easier if you know what has to go on the inside first and then make the exterior dimensions the appropriate size to get the internal volume you need.  

 

If you use a program like Torres you can plug in your specs and it will tell you what your tuning is,  you can then tweak your port length to get your tuning where you want it to be.  It will take care of the math for you. 

Edited May 9, 2015 by Triticum Agricolam

[ManzKea 152]

Ya I used the 12volt. Com to tell me my port length.

So you're saying you build the port, then work around that???

Cuz I'd just measure the box size I can fit. Minus 1.5 from h, w, d, to get the total net. Then use that number in the 12volt calculator. Then if it's too large lessen some of the dimensions, then I re adjust the length to keep that tuning in the new net cubic ft

[///M5 2,833]

This should all happen before you even shop for a sub...

Determine max box dimensions

Estimate net volume with desired port and tuning

Determine if new max volume is enough

Rudimentary layout

Calculate port volume exactly

Add port volume to desired net volume

Lay out the box

Double check

Order sub

[Triticum Agricolam 15]

Ya I used the 12volt. Com to tell me my port length.

So you're saying you build the port, then work around that???

Cuz I'd just measure the box size I can fit. Minus 1.5 from h, w, d, to get the total net. Then use that number in the 12volt calculator. Then if it's too large lessen some of the dimensions, then I re adjust the length to keep that tuning in the new net cubic ft

I don't build the port first, but I do design it first.  I design all my boxes in SketchUp so I have everything completely figured out before I ever start making any sawdust.  Its the 7P process.  Proper prior planning prevents piss poor performance. 

[ohio45113 24]

How do you like the ethos?

[ManzKea 152]

Sorry hardly been on for a bit. But thanks for the information and tips. I need to get a laptop to use all those software I see people use. I just find the volume of a box for the location, use the 12volt to determine the length needed my port to be proper tuning, and I try to keep the port area within manufacture recommendations. Or 16- 18 I believe is a rule of thumb I seen somewhere.

But I know with the softwares, I guess you can measure the output at different frequency and what not

[ManzKea 152]

How do you like the ethos?

Hasn't came in yet. Quentin finnally shipped it last week and should be here in Tuesday, very excited can't wait. I'm using 2 re sxxv2 for now and I'm pretty content, so I know the ethos we blow these away which should make me go from content to ecstatic lol

[ohio45113 24]

How do you like the ethos?

Hasn't came in yet. Quentin finnally shipped it last week and should be here in Tuesday, very excited can't wait. I'm using 2 re sxxv2 for now and I'm pretty content, so I know the ethos we blow these away which should make me go from content to ecstatic lol

Did he give you the $325 shipped price? Didn't you say you were in Hawaii? If so he lost his ass on that deal lol

[ManzKea 152]

Naw I paid the regular price plus I think $80shipping. I used the lay away plan to pay for it.

[ohio45113 24]

Naw I paid the regular price plus I think $80shipping. I used the lay away plan to pay for it.

That layaway shit is nice lol.. Wish all these companies did that.

[ManzKea 152]

Ya it is. I didn't feel guilty at all dropping 7 something. Little here little there lol then when it gets to 200 pay it off