Sub Port Avise

[Caio Ferrari]

Folks,

I'm about to finish the box for my DIY sub (JBL speaker GTO1014D).

The enclosure has 40 L free (same as the manual value) and tuned to 30 Hz.

It turns out that the manual indicates a 3 " Port (which gives about 30 cm of length), while the theory says that a 4" Port is the ideal due to the blow (which results in an almost 60 cm length and which I will need curves to fit the box).

With the 4 "port, the air velocity is around 33 m / s and rises to almost 60 m / s in the 3" port.

Here, I am :

The 4 " meets the technical requirements of speed of sound, less compression and therefore less loss of SPL and etc. But, it becomes too big to be manipulated inside the box

A 3 " port fits well inside the box, without skidding, is the one recommended by JBL USA in the design of the box .... but, it disrespects the reasonable limits of air speed so as not to generate blowing.

Given this, I ask: Does anyone have any tips?

 

[richie00boy]

Go with the bigger port and use bends, also ensure to include the volume wasted by the port in the final box size.
The design is aimed at car use where the port noise will not be noticed much. I assume you have a hifi application.

 

[Caio Ferrari]

That's right.
I'll go for 4". Thank you

 

[GM]

With the 4 "port, the air velocity is around 33 m / s

The 4 " meets the technical requirements of speed of sound

Sorry, not even close, it's normally listed as < 5% SoS and some say as low as 3% for any sort of HIFI/HT app or at least < ~17 m/s, which means a huge long, pipe, so might as well make it a TL. That, or seal it up and use DSP to shape it's response if you need to keep it small.

GM

 

[cspieker]

It sucks to have it all made and find that the port chuffs, ask me how I know. Gm is right, don't build it with a single 4". My 12" subs have two 4's now.