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Need Port Help ASAP
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<blockquote data-quote="T3mpest" data-source="post: 8279117" data-attributes="member: 560148"><p>It's not all about port noise.. If it was JUST noise, big ******* deal, 140db of bass and the trunk muffle that anyways. The MAIN issue is that even before a port chuffs it "compresses" and when it's chuffing its REALLY compressing. Basically realize what you see in WINISD is a 1w/1m response. It's the acoustic combination of your port and your woofer. Woofer does the higher notes, port plays notes near tuning, they both play stuff just above tuning, and below tuning they play stuff together as well, but out of phase.. However, a smaller port has a lower potential for moving air than a bigger one.. So when the port compresses all your notes near tuning will stop getting louder while the woofer keeps going.. So once you turn up the volume knob that nice low end the program shows you goes away as the port compresses.. Imagine a response much closer to sealed box, but even higher distortion due to the air noises and turbulence. So yes, it's a mess.. Will it sound terible, hard to say, turn it up and see what you think.. Generall speaking I try to keep port velocity below 20m/s for a box tuned at 30hz or below.. As I tune closer to 35hz I can do as high as 25m/s without worrying at all about port noise. These are just my main goals a little higher than this won't be a problem. When you get the sub in play something like White Girl" by Young Jeezy. It has a 32hz tone and 58hz tone.. Play it at low to medium volume and listen to the difference in SPL between the high and low note.. Then do it again at full tilt and see if the higher note isn't abit more overbearing than it was compared to at low volume.. If it is, that's port compression</p><p></p><p>I would still strongly suggest finishing it for now, run it for the time being, but build a new box with the guidance I and SQ have given you.. I think you'll find the A/B comparison enlightening.</p></blockquote><p></p>
[QUOTE="T3mpest, post: 8279117, member: 560148"] It's not all about port noise.. If it was JUST noise, big ******* deal, 140db of bass and the trunk muffle that anyways. The MAIN issue is that even before a port chuffs it "compresses" and when it's chuffing its REALLY compressing. Basically realize what you see in WINISD is a 1w/1m response. It's the acoustic combination of your port and your woofer. Woofer does the higher notes, port plays notes near tuning, they both play stuff just above tuning, and below tuning they play stuff together as well, but out of phase.. However, a smaller port has a lower potential for moving air than a bigger one.. So when the port compresses all your notes near tuning will stop getting louder while the woofer keeps going.. So once you turn up the volume knob that nice low end the program shows you goes away as the port compresses.. Imagine a response much closer to sealed box, but even higher distortion due to the air noises and turbulence. So yes, it's a mess.. Will it sound terible, hard to say, turn it up and see what you think.. Generall speaking I try to keep port velocity below 20m/s for a box tuned at 30hz or below.. As I tune closer to 35hz I can do as high as 25m/s without worrying at all about port noise. These are just my main goals a little higher than this won't be a problem. When you get the sub in play something like White Girl" by Young Jeezy. It has a 32hz tone and 58hz tone.. Play it at low to medium volume and listen to the difference in SPL between the high and low note.. Then do it again at full tilt and see if the higher note isn't abit more overbearing than it was compared to at low volume.. If it is, that's port compression I would still strongly suggest finishing it for now, run it for the time being, but build a new box with the guidance I and SQ have given you.. I think you'll find the A/B comparison enlightening. [/QUOTE]
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