Port Calculations

[Hecta G]

What is a good way to calculate port size and length? Is it a straight measurement down the middle?

How does port area/volume affect the relationship with the volume of the box and ultimately the desired acoustic effect?

Any help would be great.

I guess before you guys ask, i like clear deep bass, I'm not into the BOOM BOOM or competition, I want to hear everything that's on the track. Knowing this what frequency should my box be tuned to?

Okay, i'm done with the questions.

Thanks guys

[dman4486]

you must subtract the port area from the total volume...
I like the same..having response below 40 hz is my goal, and IMO you should look to tune for a flat response if u want sq.

[Hecta G]

i have a lot of restrictions on my build and was wondering of i needed a really long port i was going to snake it around on the inside of the box but didn't know of what calcs to use

[Mr Cabinetry]

i have a lot of restrictions on my build and was wondering of i needed a really long port i was going to snake it around on the inside of the box but didn't know of what calcs to use

The port length is determined based on the following:

Volume of the enclosure
Port Area - Width x Height for a slot port or Port Diameter for a round port
Port Tuning you want or desire.

You say their are restrictions as to how the port needs to fit within the interior of the enclosure and that the length is cause for concern. If the lenght becomes so long that fitting it will be a royal PITA, then the only option to decrease the ports length without changing the port tuning is to reduce the size of the port area.

However, in reducing the size of the port area will increase the " vent mach " of the air moving within the port, so you have to find a balance per say that vent mach increases yet stays below the threshold that port noise would start to occur.

Since you goal is SQ rather than SPL for the design ported, keep the vent mach at a 90ft/sec level given the max wattage you intend to operate at and you will be fine.

Phil
Woodlawn Cabinetry

[Hecta G]

The port length is determined based on the following:

Volume of the enclosure
Port Area - Width x Height for a slot port or Port Diameter for a round port
Port Tuning you want or desire.

You say their are restrictions as to how the port needs to fit within the interior of the enclosure and that the length is cause for concern. If the lenght becomes so long that fitting it will be a royal PITA, then the only option to decrease the ports length without changing the port tuning is to reduce the size of the port area.

However, in reducing the size of the port area will increase the " vent mach " of the air moving within the port, so you have to find a balance per say that vent mach increases yet stays below the threshold that port noise would start to occur.

Since you goal is SQ rather than SPL for the design ported, keep the vent mach at a 90ft/sec level given the max wattage you intend to operate at and you will be fine.

Phil
Woodlawn Cabinetry

Thanks Phil,

I will be putting roughly 300-500 watts into the sub and I think that I am able to get 1.5ft^3 for the box. I was initially looking at an ABC box but learned from the guys here that it wouldn't work as how I wanted it to, so it lead me to a ported box in which i will try and make a grill to protect it from my kids.

As for calculations do you know of a decent site would shed some light on more than just a straight port calculation?

Thanks again for your help

[Mr Cabinetry]

Thanks Phil,

I will be putting roughly 300-500 watts into the sub and I think that I am able to get 1.5ft^3 for the box. I was initially looking at an ABC box but learned from the guys here that it wouldn't work as how I wanted it to, so it lead me to a ported box in which i will try and make a grill to protect it from my kids.

As for calculations do you know of a decent site would shed some light on more than just a straight port calculation?

Thanks again for your help

There was a calculator I found on net that dealt with what you asking about and for the life of me I didn't bookmark the d@mn site when I found it.

There are some calculators online that will provide slot port layout detail, but they only work with the port size being whatever the height of the box is, but, I don't see why they could not be use for the same thing, just use them in different manner to get the layout of the port.

Phil
Woodlawn Cabinetry

[bluelceii]

http://www.carstereo.com/help2/Articles.cfm?id=31

scroll down to 'calculate your vent length'

[Hecta G]

Thanks Bro!!

MAN!! This site rocks!!!

to all of you!