Posted November 13, 201014 yr No matter how many times it's told, there are always nonbelievers; assuming because you have a hole in an enclosure, it is ported, yes your enclosure has a hole in it but it is not a properly vented box, what you have is a leaky sealed box, and sadly it lacks the good things gained when you properly port a enclosure.Here is a technical understanding: http://www.bodziosoftware.com.au/PORTS.pdf
November 22, 201014 yr pretty good stuff, only a few things. Reynolds number is pvD/u not pvr/u and typically laminar air transitions to turbulent at around 50,000 to 70,000 not 20,000. Also it should be noted that the Re # is HIGHLY dependent on factors in the port such as relative roughness and the resulting pressure gradient. Looks like a well thought out little paper though. I didnt read the whole thing but looks like it might be worth it. I say these things since im in mechanical engineering and will be starting my masters in fluid dynamics and thats basically all a port is (fluid mechanics). I plan to do some CFD modeling of them in the future. Also a slot port can be approximated as a infinitely wide parallel plates and you can obtain the veloctiy profile of the air, and from that find you can find the volume flow rate, pressure gradient, shear stress on the box wall, max and average port velocity etc. Not sure if the paper covers it but the compressibility effects of air are WAY beyond the scope of anything in that paper. If it doesnt mention it I would take everything with a large grain of salt. Compressibility effects will alter almost everything as much as 40%
April 15, 201114 yr Just me or is the link dead? I probably could have used this for my Fluid Dynamics exam I wrote this morning...
September 28, 201113 yr Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct?
September 28, 201113 yr Author Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct?What driver(s) are being used?
January 5, 201213 yr 4.2 before or after displacement?I believe the generally accepted ratio is 12"-16" of port area per cubic foot of box...You currently have 6.72" of port per cube - about half what you probably should (if that 4.2 is after displacement)...Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct? Edited January 5, 201213 yr by n8skow
January 5, 201213 yr Original link works for me. Click on it/file/save as and name it and choose a location and then open it.
January 5, 201213 yr 4.2 before or after displacement?I believe the generally accepted ratio is 12"-16" of port area per cubic foot of box...You currently have 6.72" of port per cube - about half what you probably should (if that 4.2 is after displacement)...Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct?the "generally accepted rule" is bs, it depends on the driver used. Edited January 5, 201213 yr by trod2902
January 5, 201213 yr 4.2 before or after displacement?I believe the generally accepted ratio is 12"-16" of port area per cubic foot of box...You currently have 6.72" of port per cube - about half what you probably should (if that 4.2 is after displacement)...Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct?the "generally accepted rule" is bs, it depends on the driver used.It comes down to the tuning frequency of the enclosure, area of port, and acoustic power output from driver.
January 5, 201213 yr I think you've mistaken 'generally accepted' for 'universal'.At any rate - care to enlighten us? How do 'you' determine how much port for a given woofer?I'm all ears...4.2 before or after displacement?I believe the generally accepted ratio is 12"-16" of port area per cubic foot of box...You currently have 6.72" of port per cube - about half what you probably should (if that 4.2 is after displacement)...Okay, so what I'm picking up here, my single flared 6" aero in my 4.2 cube net box, is too small. Basically, if I play a lower note (I'm tuned to 33hz) ~35hz and lower, it blows a tremendous amount of wind out. My burp frequency is 38 hz and I raise from .7 to 4.5 ohms. This all has to do with my port being to small and it acting more like a severely leaky sealed box correct?the "generally accepted rule" is bs, it depends on the driver used.
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