changable tuning.. port questions

[abrhino 10+ year member]

im shooting for a Tunable port for my DC LV5.. i need help with my design.. its gonna be sub up/ port back around 3.2 after wood/port/bracing displacement

External

36w X 14t X 17d

Internal

34.5w X 12.5t X 15.5d = 3.87cuft minus .68cuft port disp = 3.19cuft

Im going to divide the port into 2 horizontal sections using sanded and rounded .75MDF. directly in half so the port height will be 11.75H or 2 5.87h X 6w sections.. port displacement is .68cuft

If my calculations are right tuning will change if i plug the bottom port..

Unplugged

11.75h X 6w X 17.3L = 45hz

Plugged

5.87h X 6w X 17.3L = 33-34Hz

Will the 35.3sqin of port work for daily on the DC LV5? unplugged it is 70.6 SQin of port

Click to read more...

 

[CoilBurner]

Your daily plugged low tune port needs more area. Do interchangeable ports. Much easier

 

[abrhino 10+ year member]

its 11sqin per cube.. how is it much easier? i dont understand interchangable ports very well

 

[abrhino 10+ year member]

what if i change the port

5.87t X 7w X 21L = 33hz and 41sqin port. nearly 14sqin port per cuft.

port displacement is 1cuft 3.87-1= 2.87cuft

or

5.87t X 8w X 24.3L = 33hz and 46.4sqin port. 18.2 sqin port per cuft

port disp is 1.32. 3.87-1.32 = 2.55cuft

 

[Fuknmovin 10+ year member]

I would try to stay as close to the DD calc as possible and that is 16" per CuFt. But I think your 14"er will work good...

 

[abrhino 10+ year member]

yeah imma go with the 14sqin. unless sumthin comes up

 

[abrhino 10+ year member]

bump for opinions?

 

[bubbagumper6 5,000+ posts]

Did you actually calculate the tuning using 2 ports or did you just calculate it for one then plan on dividing the port? Because you can't just divide a port and keep the same length, it will affect the tuning. Also, for when the one is plugged, did you take into account the fact that one of your ports is now part of the net volume? That also will affect the tuning.

I think this is more complicated than you think...interchangeable ports would be better.

 

[Fuknmovin 10+ year member]

Good point....

 

[abrhino 10+ year member]

yes, i accounted the port displacement into both of my designs.. the one with 7in port width is 2.87 cuft after port displacement.. and YES i calculated both ports in the12volt port calculator..

in a 36w X 14t x 17d box it is 3.87cuft before port displacement

port (account for .75 brace/separator) 11.75t X 7w X 21L = 45hz

half the port height (bc its plugged) 5.88t X 7w X 21L = 33hz

thats what my calculations came up with. Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

 

[abrhino 10+ year member]

if thats incorrect, plz help me understand. i crunched numbers for an hour comin up with this

 

[bubbagumper6 5,000+ posts]

yes, i accounted the port displacement into both of my designs.. the one with 7in port width is 2.87 cuft after port displacement.. and YES i calculated both ports in the12volt port calculator..
in a 36w X 14t x 17d box it is 3.87cuft before port displacement

port (account for .75 brace/separator) 11.75t X 7w X 21L = 45hz

half the port height (bc its plugged) 5.88t X 7w X 21L = 33hz

thats what my calculations came up with. Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

That's not what I'm talking about. All your calculations for when you have both ports open say that the port is 11.75H, which it's not, you have two ports that equal 11.75H. You can't just take a port and divide the height in half, it will affect the tuning. And I know for a fact you didn't do this because the12volt calculators don't allow you to enter that you have more than one port.

 

[RAM_Designs 5,000+ posts]

Use the carstereo.com calc, you can enter as many ports as you'd like. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[abrhino 10+ year member]

That's not what I'm talking about. All your calculations for when you have both ports open say that the port is 11.75H, which it's not, you have two ports that equal 11.75H. You can't just take a port and divide the height in half, it will affect the tuning. And I know for a fact you didn't do this because the12volt calculators don't allow you to enter that you have more than one port.

you're right. thanks

Use the carstereo.com calc, you can enter as many ports as you'd like. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

will do man, thank you

 

[abrhino 10+ year member]

why is the12volt and carstereo.com port calculators so far off? I pluged in my current box on the12v and it it was 3hz off of carstereo's calculations

current box

is 4.99cuft before port displacement.. port is 14.5h X 5.5w x 16.75d which equals 40hz on Carstereo and 43hz on 12v