bass port

[121rickie]

which is best, bassport in rear of cabinet or front

[Altec Best]

Originally Posted by 121rickie

which is best, bassport in rear of cabinet or front

Depends on type of speaker,location,is it in a corner,etc...

You need to provide all the variables, that will determine what is best for a specific speaker.IMHO

[whgeiger]

Originally Posted by 121rickie

which is best, bassport in rear of cabinet or front

As [fb] is approached, output from the port increases while that of the driver approaches a null. Therefore, front ports are preferred. When [fb] is very low, then a rear port may be used instead. Here, signal wavelength is many times longer than the distance between the driver and the port, and port noises due to increased air-flow are obscured.

Regards,
WHG

[Mustang Man]

I know there must be a formula somewhere, but I am new to this forum. I know AB from the Altec users forum. I thought this might be a better place to post this question.

I am building speaker enclosures and need to determine port size. Using speaker specs anlog with enclosure dims, there is a formula for determing port size. Could someone please point me in the right direction.
Thanks,
MM

[chris661]

Running simulations in winISD would likely be easier than a formula. It's very easy to tweak the design.

[speaker dave]

Originally Posted by 121rickie

which is best, bassport in rear of cabinet or front

The wavelengths are usually very long so you are unlikely to notice any difference between a port on the front or a port on the back. The port output is nondirectional. Room standing waves might have a small but hard to predict effect.

David S.

[Ron E]

Originally Posted by Mustang Man

I know there must be a formula somewhere, but I am new to this forum. I know AB from the Altec users forum. I thought this might be a better place to post this question.

I am building speaker enclosures and need to determine port size. Using speaker specs anlog with enclosure dims, there is a formula for determing port size. Could someone please point me in the right direction.
Thanks,
MM

Lv=2360*Dv^2/(Fb^2*Vb)-0.73*Dv
Lv, Dv in mm, Vb in liters

[Mustang Man]

Thanks Ron, but I have no idea how to interpret the formula. Could you please explain. I am new to this hobby and this old brain wasn't any good in math even when it worked better.

Sorry I am so ignorant...

[Altec Best]

MM maybe start a new thread here with your cabinet dimensions and a frequency you are trying to reach say 25-30 Hz or whatever that maybe and maybe someone would be able to help calculate for you.I'm pretty much in the same boat WRT determining port dims as you.GM calculated my ports for me.

[head_unit]

Presuming the port is tuned low, it shouldn't make much acoustic difference where it is placed. Rear ports can be harder to position (needs to be several radii away from the wall or other obstacles). But since some midrange can reflect/leak out through the port, and the port may have its own resonant peak, front placement may aim that right at the listener.

My "Safe" rule of thumb for port size was 3" for an 8"; 4" for a 10"; 5" for a 12." Smaller than that, best check a simulation to see that at maximum output the flow is still a low % of the speed of sound. Yes, it can become hard to fit the port. NO you should not bend it, I don't care what anyone says. End flares/flanges help at medium SPLs but actually not at high SPL, according to JBL research.