Hi,
I am building a subwoofer enclosure for a 21" driver and need a slot port that is bent once to get the total length for the tune (30hz). But I am wondering at what conditions require the port to be rounded at the elbow as opposed to a 90° join?
I have modeled in win isd and with a port area of 1500cm2, i have quite a bit of area to avoid chuffing and turbulence. Modelling in win isd gives me a port velocity of 9.5m/s at max input power (likely at a frequency i will eq out anyway, so more like 8m/s at a realistic frequency..).
My question is whether this is enough to avoid any chuffing or major turbulence effects that will affect the sound if i make my port with a 90° bend as opposed to rounding the elbow of the port by cutting the corner on the turn to be 45° (and mirroring on the other side to maintain consistent port area throughout the bend). I assume i am fine to keep it at 90° with a low-ish port velocity, but wanted some advice from someone who has built something similar before i glue up and going back becomes a major pain in the...
A cursory Google search mostly lists posts for round ports and home audio applications but as this is a PA speaker with a beefier driver pushing out more air than a home audio sub, i was wondering if the community here could advise me.
Thanks 🙂
I am building a subwoofer enclosure for a 21" driver and need a slot port that is bent once to get the total length for the tune (30hz). But I am wondering at what conditions require the port to be rounded at the elbow as opposed to a 90° join?
I have modeled in win isd and with a port area of 1500cm2, i have quite a bit of area to avoid chuffing and turbulence. Modelling in win isd gives me a port velocity of 9.5m/s at max input power (likely at a frequency i will eq out anyway, so more like 8m/s at a realistic frequency..).
My question is whether this is enough to avoid any chuffing or major turbulence effects that will affect the sound if i make my port with a 90° bend as opposed to rounding the elbow of the port by cutting the corner on the turn to be 45° (and mirroring on the other side to maintain consistent port area throughout the bend). I assume i am fine to keep it at 90° with a low-ish port velocity, but wanted some advice from someone who has built something similar before i glue up and going back becomes a major pain in the...
A cursory Google search mostly lists posts for round ports and home audio applications but as this is a PA speaker with a beefier driver pushing out more air than a home audio sub, i was wondering if the community here could advise me.
Thanks 🙂
9m/sec is not all that high. At the 90deg bend I would try to sort of chamfer the corner a bit. It is very likely the sharp internal corner (e.g. like an "L") sticking into the port that will cause the most turbulence so the more you can relieve this the better. You can then just put a block across the outside corner to make it smoother, but that is probably much less of a source of turbulence... I would not worry too much about keeping the port cross-sectional area exactly the same thru the bend since you will probably need to adjust the port length a bit to fine tune the box tuning anyway.
