Hi all,
So I finally put together my subwoofer using the tang band 5.25" driver with the advice of some very helpful people here, thank you!
All seems to be well except for port noise when I have it at a loud volume and I wonder if I can ask for some advice on how to stop it.
My port is 0.5" wide and terminates with part of the end of the cabinet. I have attached three images that should hopefully show what I mean. The port runs along the front edge of the baffle and I was hoping to terminate it with some flaring but the panels I had cut weren't as they should have been so I carried on anyway.
The port is 6" high, 0.5" wide and 9" long.
Is the port noise from the shallow width or could it be the terminating panel that the air is smashing in to?
Again, I have searched the threads but there is not conclusive theme on what could be the culprit. Some people have said a narrow port makes it whistle? Or could it be the sharp edges?
Would appreciate any suggestions or feedback on my little project!
Cheers!
So I finally put together my subwoofer using the tang band 5.25" driver with the advice of some very helpful people here, thank you!
All seems to be well except for port noise when I have it at a loud volume and I wonder if I can ask for some advice on how to stop it.
My port is 0.5" wide and terminates with part of the end of the cabinet. I have attached three images that should hopefully show what I mean. The port runs along the front edge of the baffle and I was hoping to terminate it with some flaring but the panels I had cut weren't as they should have been so I carried on anyway.
The port is 6" high, 0.5" wide and 9" long.
Is the port noise from the shallow width or could it be the terminating panel that the air is smashing in to?
Again, I have searched the threads but there is not conclusive theme on what could be the culprit. Some people have said a narrow port makes it whistle? Or could it be the sharp edges?
Would appreciate any suggestions or feedback on my little project!
Cheers!
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Port noise is generally due to the port being to small (the cross sectional area), so if you can still make it larger, that would be the most effective option. The increased cross sectional area would of course mean that the port would have to be longer to keep the same tuning frequency. Rounding over edges can slightly lower the noise, so it might work depending on how sever the effect is. Sharp edges in general, like near the end of your port should be avoided.
Johan
Johan
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Interesting! Is there a ratio for port volume versues length to keep the same tuning? I used somebody elses length and adjusted cross sectional area so I have guessed a little!
During loud music. I haven't tested it with sine tones. Is there a procedure to debug with sine tones?
Rule of thumb is port cross section should be 1/3 of the cone area (SD) of the speaker driver.
The W5-1138SMF has a cone area of just under 15 square inches. The cross section of your port, however, is 3 square inches. This is taylor made to "fart" at higher output levels.
The port termination won't help but it's not the main problem.
If you could double the port x-section and the length of the port (to 6 inches square and 18 inches length), that would help immensely. Maybe run the port along the floor, then up the back?
Other "size" combinations should also work. (4.5"2 by 13.5" etc... Just keep the proportions).
J.
The W5-1138SMF has a cone area of just under 15 square inches. The cross section of your port, however, is 3 square inches. This is taylor made to "fart" at higher output levels.
The port termination won't help but it's not the main problem.
If you could double the port x-section and the length of the port (to 6 inches square and 18 inches length), that would help immensely. Maybe run the port along the floor, then up the back?
Other "size" combinations should also work. (4.5"2 by 13.5" etc... Just keep the proportions).
J.
Ah ha! I see, thanks for this!!!
So, if I increased the port x-section and length will I need to up the cabinet volume to accommodate this extra internal structure? From what I have been told I read I will have to add the port volume and structure on top of the recommended cabinet volume. Is this the case here?
So, if I increased the port x-section and length will I need to up the cabinet volume to accommodate this extra internal structure? From what I have been told I read I will have to add the port volume and structure on top of the recommended cabinet volume. Is this the case here?
Yes, port volume is "extra" on top of cabinet volume.
Depending on tuning 11-12 litres seems right for the W5. It does want a very long port though.
You're supposed to allow for the intrusion of the woofer into the cabinet too.
One issue with slot port is tuning it. You need to be able to adjust the port length if you want to measure the response in the real world. So it needs to be built without glueing everything up, first time.
Depending on tuning 11-12 litres seems right for the W5. It does want a very long port though.
You're supposed to allow for the intrusion of the woofer into the cabinet too.
One issue with slot port is tuning it. You need to be able to adjust the port length if you want to measure the response in the real world. So it needs to be built without glueing everything up, first time.
Needed air velocity to reduce turbulence chuffing depend of power, size of vent, but is really frequency dependent.
Here all you need, with a little reaaaaally useful app :
Flare-it - Free Speaker Design Software
Here all you need, with a little reaaaaally useful app :
Flare-it - Free Speaker Design Software
The port noise could also come from frequencies, which aren't audible anymore. You can try to set a subsonic filter/low cut below the tuning freq., that could improve it a lot too. Besides that, it gives you a lot more headroom (or in other words more undistorted max spl).
Generally are sharp edges and especally hard turns very bad for the port performance, you should always try to avoid them, they cause losses and compression. Another improvement would be to reduce the circumference while maintaining the same port cross section area.
-> i.e. round or less shallow port
The reason is you get turbulences on the port surface. More surface at the same port area means more losses.
The most important thing is the port dimensions. You can simulate the air velocity in winisd pro to keep it below audible levels and use it to optimize the port dimensions.
Generally are sharp edges and especally hard turns very bad for the port performance, you should always try to avoid them, they cause losses and compression. Another improvement would be to reduce the circumference while maintaining the same port cross section area.
-> i.e. round or less shallow port
The reason is you get turbulences on the port surface. More surface at the same port area means more losses.
The most important thing is the port dimensions. You can simulate the air velocity in winisd pro to keep it below audible levels and use it to optimize the port dimensions.
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