does the shape of the port matter?

Status
Not open for further replies.
Jump to Latest
K

kcducttaper

Member
Joined 2014
#1
I'm working to make a 3 way and got to wondering if the shape of a port really mattered much. Would a small diameter flared port (high velocity) sound identical to a larger port with lower velocity? What about slot ports? Would a straight port sound different than the same length slot port with an elbow or a U? Would a slot port sound the same as a round port provided tuning frequency is the same? I have the general impression that small flared circle ports are 'best' in terms of SQ, but I don't really know why I have that impression or if it's true.
 
#2
Wide, flat ports have a very big port surface. That's where the air 'rubs' on the port walls. That leads to turbulences and losses, the higher the velocity, the worse it gets. How does that affect the sound? It's compression and the port dimensions virtually change. High velocity should always be avoided because of the losses and the audible chuffing it can produce, you can reduce the velocity by making the port bigger but that, ofcourse, makes the port significantly longer.

If you can't put a that long port into your enclosure (also remember the port volume doesn't count for the driver volume), it's better to use a passive membrane instead of a port.
 
#3
I'm trying to make a 3-way with the TangBand W5 as the woofer. It's surprisingly hard to get 3 drivers, and ports, on the baffle while keeping the baffle small enough that the speaker doesn't look funny. I went with 2x 1.55" ID (measured) ports with an elbow in each. WinISD shows a max velocity at 20 m/s, but it's chuff city even at low volumes. I must've botched my porting job somewhere and am creating a bunch of turbulence somewhere.
 
#5
kcducttaper said:
I'm trying to make a 3-way with the TangBand W5 as the woofer. It's surprisingly hard to get 3 drivers, and ports, on the baffle while keeping the baffle small enough that the speaker doesn't look funny.
Click to expand...

TangBand W5 you say? Well, there are at least 5 different 'W5'.
You've still got the option to put the port on the back. Or use a passive membrane (probably also on the back or side).

kcducttaper said:
I went with 2x 1.55" ID (measured) ports with an elbow in each. WinISD shows a max velocity at 20 m/s, but it's chuff city even at low volumes. I must've botched my porting job somewhere and am creating a bunch of turbulence somewhere.
Click to expand...

~20cm² isn't very much for a high excursion driver even at 5" and 20m/s is already too high. You could improve it by rounding the edges of the port at the baffle aswell as inside. And the port needs to have 'breathing room' in the enclosure aswell.
 
#6
kcducttaper said:
I'm working to make a 3 way and got to wondering if the shape of a port really mattered much. Would a small diameter flared port (high velocity) sound identical to a larger port with lower velocity? What about slot ports? Would a straight port sound different than the same length slot port with an elbow or a U?
Click to expand...

To me slightly oversized flared slot ports, no less than 1, better 1.5 inch in width sound best despite the disadvantages.

Every angle or corner will introduce losses and will virtually lengthen the port and compromise sq.

In terms of sq port length is much more critical than shape given adequate diameter.

For sq I would not go above 0.7 feet in length.
The shorter the port the better it will sound.
 
#12
kcducttaper said:
Dangit. That means I'll have to stuff even more port in that box.
Click to expand...

No. The port volume is subtracted from the enclosure volume, that means you will very likely lose too much volume or have to fold the port (or both). Use a passive membrane instead, no chuffing and no mid-garbage (in case you'd use it for something different than a subwoofer).
 
Status
Not open for further replies.
Top Bottom