Hi, I am using a 3" tube on a 15" subwoofer. I was limited with space, so I decided to using one port only.
Winisd gave me 0.09 vent mach, it was a green number, so I tough it would be just ok, the truth is that it makes noise at high level (max power is about 150-200w). Instead of adding a second 3" tube, which would drop vent mach to 0.02, I can first try adding some port flare adapters on each side, maybe this would fix the problem. The actual flares are about a couple millimeters, considering the port walls are about 4-5mm. Do you think I can fix it by simply adding two big flares on the ends? thanks.
Winisd gave me 0.09 vent mach, it was a green number, so I tough it would be just ok, the truth is that it makes noise at high level (max power is about 150-200w). Instead of adding a second 3" tube, which would drop vent mach to 0.02, I can first try adding some port flare adapters on each side, maybe this would fix the problem. The actual flares are about a couple millimeters, considering the port walls are about 4-5mm. Do you think I can fix it by simply adding two big flares on the ends? thanks.
For what input power did WinISD give 0.09 vent mach?
The effect of flares can be checked using a Flare-it: http://www.subwoofer-builder.com/flare-it.htm A 5 mm roundover on a 76 mm port allows the air speed to be ~1.3 times as high before chuffing; a 15 mm roundover ~2 times.
The effect of flares can be checked using a Flare-it: http://www.subwoofer-builder.com/flare-it.htm A 5 mm roundover on a 76 mm port allows the air speed to be ~1.3 times as high before chuffing; a 15 mm roundover ~2 times.
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Hi, if you gave us more details, we would be able to assist better. eg, what driver & the internal size & frequency of your box ?
You should also update to the latest version http://www.linearteam.org/download/winisd-07x.exe
You should also update to the latest version http://www.linearteam.org/download/winisd-07x.exe
Historically, 'critically' damping the vent was done: https://www.flickr.com/photos/515b/5408539714/in/dateposted-public/
Nowadays, thanks to computers, freeware, folks usually do an impulse response test in lieu of the battery/switch.
GM
Nowadays, thanks to computers, freeware, folks usually do an impulse response test in lieu of the battery/switch.
GM
I just decided to add a second 3" port, will go external installing the pipes outside the enclosure, so their space displacement won't be a problem anymore. Vent mach at 30hz will be touching 0.03, which I think won't give any bad noise even without big flares.
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The Loudspeaker Design Cookbook shows flared ports only allow for less than 2dB more output before 'chuffing' comes back.
What driver are you using, and as others have asked what power are you modelling at?
Winisd shows vent mach at 1w unless you change the signal power tab. Use the xmax window and increase the power until xmax reaches its limits, then check your vent mach to make sure it's reasonable. (I try to keep it around 10 m/s at xmax)
Winisd shows vent mach at 1w unless you change the signal power tab. Use the xmax window and increase the power until xmax reaches its limits, then check your vent mach to make sure it's reasonable. (I try to keep it around 10 m/s at xmax)
I am very disappointed about such extreme long lengths big (3", 4") pipes ask, especially on low fs (around 30hz), but just playing a little on winisd found that when setting for example five 1.25" tubes, the lengths now are totally friendly even on low fs's, around 10" instead of 20" or lots more, and vent mach shows very low noise, around 0.01. I would have no problem installing five 1.25" tubes on the outside of the enclosure, actually for me it would look just amazing, nice and interesting, you can glue some 1.25" 90degree elbows, and add some clamps to keep it rigid along the length. What do you think about this?
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gives bass reflex a bad name
This is a typical mis-design which leads to poor performance. If you stop and think about what a port needs to do--- and that is to uload the driver at a certain frequency and become the new source of output. So, how can a single 3 inch diameter port equal what the 15 inch driver does the rest of the time ?
Answer is: It simply can not.
The rule of thumb (which is not written anywhere that I am ware of) is that if ducted, the port diameter should be at least 1/2 the diameter of the driver. In this case a minimum port diameter would be 7 inches. 8 inches probably slightly better.
If this results in too long of a duct length, then you probably have the wrong box volume/driver/tuning frequency relationship.
This "rule of thumb" as explained to an associate speaker builder of mine, who has stacks and stacks of trophies, winning car audio SPL contests.
This is a typical mis-design which leads to poor performance. If you stop and think about what a port needs to do--- and that is to uload the driver at a certain frequency and become the new source of output. So, how can a single 3 inch diameter port equal what the 15 inch driver does the rest of the time ?
Answer is: It simply can not.
The rule of thumb (which is not written anywhere that I am ware of) is that if ducted, the port diameter should be at least 1/2 the diameter of the driver. In this case a minimum port diameter would be 7 inches. 8 inches probably slightly better.
If this results in too long of a duct length, then you probably have the wrong box volume/driver/tuning frequency relationship.
This "rule of thumb" as explained to an associate speaker builder of mine, who has stacks and stacks of trophies, winning car audio SPL contests.
Hi
You can try design with slot ports if space were limitation. Slot port can save space as the port can follow the walls of the enclosure
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