understanding ports, a lesson in dimensions vs efficiency.

[lightfoot]

So in my particular instance I have a single RE Audio XXX 12 in a ported box that is 3 cubic feet with a port that is 28 sq." x 16" tuned to 35 hz. If I wanted to tune it lower would I just make the port longer?

[Bumpindemlowzz]

So in my particular instance I have a single RE Audio XXX 12 in a ported box that is 3 cubic feet with a port that is 28 sq." x 16" tuned to 35 hz. If I wanted to tune it lower would I just make the port longer?

why would your 12 need 3cuft most are roughly 1.5-2.5...

to answer your question yes typically

[Krakin]

So in my particular instance I have a single RE Audio XXX 12 in a ported box that is 3 cubic feet with a port that is 28 sq." x 16" tuned to 35 hz. If I wanted to tune it lower would I just make the port longer?

Correct, adding a longer port will lower the tuned frequency.

Just make sure you either keep the exact same internal volume or you account for the added displacement for the internal volume.

[lightfoot]

appreciate it. Thanks for the knowledge.

[lightfoot]

So in my particular instance I have a single RE Audio XXX 12 in a ported box that is 3 cubic feet with a port that is 28 sq." x 16" tuned to 35 hz. If I wanted to tune it lower would I just make the port longer?

why would your 12 need 3cuft most are roughly 1.5-2.5...

to answer your question yes typically

It is a very large woofer, with an xmaxx of 54mm. I called and spoke with tech support and that is what he told me to build it to. before woofer and port displacement it it actually 3.9 cubes

[yairemil01]

Shit this is like for engeneers im so lost

[AstoSoup]

This was very helpful when figuring out my net volume.... A lot of information I would have otherwise had to make threads to get! Thanks for this!

[mdwerner6942]

I can only think of negatives when considering multiple sized ports.

Don't be a negative Nancy :-P

Seriously though, what are your concerns?

Resonances.

Would you not have to separate resonances based off of the two areas of the ports?

And then you get the harmonics of the ports getting worse and worse over every next f₁*x?

Or would you just use this formula instead to find the resonance of the ports?

f₁= velocity of sound divided by two times the length of the column?

With the area having no affect on the second (and third possibly) resonance of the ports?

Now for a tip I read a long time ago from some JBL papers. If you are going to be using a system where you are trying to get every last amp through those coils, you need design your system around the parameters of your speaker when it is hot not when it is cold, as the parameters are going to drastically change from this variable.

Then after you get a hot coil what does it do to the inside of the enclosure? That's right! It gets hot as well, which means you need to go about tuning based off of the temperature of the internal volume of the cavity. As the temperature of air changes the speed in which sound travels through it changes, to find this you need to use this formula.

For air, the average molecular mass for dry air is 28.95 gm/mol, and the adiabatic constant γ = 1.4.

I skimming through this and new at the box building idea and guess my writing is not always the best, but anyways, I been working with a 6.1 box after displacement and tried 2 6" aero ports 18", then went back to old school design and changed box side tried 5 4" ports which unfortunately same time we sold Brz 2400 amp for Q12200. harder to tell what makes the difference now! I was wondering if the extra multi ports in 4" ported box (22" Long) is as effective as 2 6" were. Harder now to tell, box measures 25x25.5x21 with about 1.75" of port extending out of the box just in case I wanted to play with lower tuning to see little less output and flatter sound wave etc would sound been tuning 33-34 Hz area usually.

I just wondered if using too many ports could be a issue. 5 4" we were wondered how the extra port area would sound, but now sort of leaning back to the 6" little more net box maybe without the outside flare only inside flare wondered if maybe to many ports. Guess we could try plugging one :-) Needed a least net 5 cu ft. Son just brought up maybe tune lower use 4 instead of 5 4 " ports. Or cap one for test, not sure that be accurate since there is 22" PVC port still in the box might try that before going back to 2 6" ports.

[Damiend Kayla]

I have a orion hcca 12.2 I was thinking about double porting my box but can't figure out the port size I should make my box dimensions are 28 1/2 width 16 1/2 height and 16 1/2 width

[STEvil]

I think you could do multiple ports (size, I actually referred to this in another post not too long ago) but they would have to be in series to work properly. The resulting box size could be ridiculous though as in effect it would be A very, very long ABC box. Kind of makes me think of a naughtilus sea shell now that im trying to model it in my head..