port velocity and aeroport distance from enclosure wall?

[Jimcat]

looking to gain some knowledge on these 2 subjects what is port velocity and how does it create unwanted noise?

also how far does the end of my flared aeroport need to beefro the enclosure wall i think i read diamater of port itself?

[Joe X]

When the sub pushes or pulls a certain volume is displaced, that goes out or into the port, depending on the cross-sectional area of the port you will have more or less airspeed through it, when airspeed becomes too high turbulence sets in and causes port noise, any sharp edges inside the port or at it's ends can make port noise worse, mainly you control noise increasing port cross-sectional area.

[Jimcat]

thanks for the imput joe i downloaded winisd pro but still dont know all its functions can it measure port turbulance or velocity?

[mothra]

if you are using a program that shows PV than you'll want to keep it between 15-25m/s. above 25m/s you are very likely to get port noise. increasing your port area will get your PV lower but don't increase it by too much b/c too low of a PV and you'll get low output. I make my boxes with a port length less than 12" or longer than 20" as well as a PV faster than 24m/s or slower than 20m/s.

[Krakin]

Noise with respect to velocity is also dependent on area. Larger areas can have larger velocities without compression, so generalizing it to 15-25m/s is also an inaccurate rule of thumb.

[Joe X]

thanks for the imput joe i downloaded winisd pro but still dont know all its functions can it measure port turbulance or velocity?

I believe you can although not sure how accurately, at what point turbulence presents itself depends on the layout of the port and if it has optimizations or not, like flares, etc not only airspeed.

[Ritch40]

yes, you can see simulated port velocity with winISD.

the software also does have a few options for the end of the ports as well, although imho those options are limited. I also think the lack of options there was to keep the software less confusing for less experience people(like myself).

[Ritch40]

Noise with respect to velocity is also dependent on area. Larger areas can have larger velocities without compression, so generalizing it to 15-25m/s is also an inaccurate rule of thumb.

Is there a way to simulate this in a effort to be more informed before the saws come out?

I am aware that simulations can only be just so accurate, but, always nice to have a rough idea when you go from the design stage to the building stage.

thanks