can this work?
lets say you had a 4inch diameter port, and a 6inch, in the same enclosure, both the same length.
would you simply take the total port area when determining the required length?
lets say you had a 4inch diameter port, and a 6inch, in the same enclosure, both the same length.
would you simply take the total port area when determining the required length?
Yes,You use the total area of the two tubes to the determine the length and both tubes shall be the same length.
jer 🙂
jer 🙂
not quite, if both tubes are the same length the smaller one would be tuned lower than the larger one. basically it's a bad idea as the larger port would blow out before the smaller one, you'd be making a leaky BR box.
Also when tuning for multiple ports you have to divide the Vb by the number of ports then do the calculation for each. That's why port length gets longer the more ports you add.
Also when tuning for multiple ports you have to divide the Vb by the number of ports then do the calculation for each. That's why port length gets longer the more ports you add.
No,I haven't done this before it was just a therotical calculation I would use tubes of the same size Myself.
But I don't see why it wouldn't work as the work of the port is its total area with its length. Even when using mutiple ports in Winlsd it still works out as one port the the same area as the total area of two or more ports.
Maybe some one whom has tried this can elaborate more on the subject.
I don't have a box readily availible to test this theory at the moment.
jer 🙂
But I don't see why it wouldn't work as the work of the port is its total area with its length. Even when using mutiple ports in Winlsd it still works out as one port the the same area as the total area of two or more ports.
Maybe some one whom has tried this can elaborate more on the subject.
I don't have a box readily availible to test this theory at the moment.
jer 🙂
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I've tried it. it dosen't work. The ports couple to the internal volume differently and it makes a slurry mess.
plug this into winisd
open two project boxes with the same driver ported 2.5ft^3
first project with one port 5" diameter 18.84"
second with two ports 3.535" diameter
they have the same cross area but the box with two ports will be longer by an inch
this was years ago,
I wanted to get a dual tuned box one port tuned to 14Hz the other larger tuned to 18Hz. I thought i'd use it to tune the box with a larger region of port output but the two ports worked against each other and there was almost no port output. This was before I understood the physics of resonators. knowing what i know now I would have just plugged one or the other to get a tunable box
but thats not the same thing.
it sounds like you had the same port area for both ports, but different lengths.
it sounds like you had the same port area for both ports, but different lengths.
two ports different lengths
Hi there: I recall reading an article in "Strings Magizine", where a professor was reproducing music with a box speaker enclosure with ports of different lengths. The ports shown in a picture, were external to the box (probably for ease of tuning). There were no details for the box, drivers or ports, however the results were discribed as amazing. So as usual, our new ideas have been considered by others in the past. ...regards, Michael
Hi there: I recall reading an article in "Strings Magizine", where a professor was reproducing music with a box speaker enclosure with ports of different lengths. The ports shown in a picture, were external to the box (probably for ease of tuning). There were no details for the box, drivers or ports, however the results were discribed as amazing. So as usual, our new ideas have been considered by others in the past. ...regards, Michael
Yes,I see your point and I am not sure about the math that is causing this.
But the diference in tuning in the example is a rise by .7 hz for using two ports.
Also the area of 2 X 3.535 is slightly smaller than a 5"dia. tube.
This could account for maybe .5%.
A difference of only 2% to 3% total between the two.
Something that will doubtfully be heard by ear anyhow, As it is a difference of less than .2db on the peak in this particular example.
I will look more into this in the future and see what else I can find on the subject.
jer 🙂
But the diference in tuning in the example is a rise by .7 hz for using two ports.
Also the area of 2 X 3.535 is slightly smaller than a 5"dia. tube.
This could account for maybe .5%.
A difference of only 2% to 3% total between the two.
Something that will doubtfully be heard by ear anyhow, As it is a difference of less than .2db on the peak in this particular example.
I will look more into this in the future and see what else I can find on the subject.
jer 🙂
this page has a good description of what's going on.
JL Audio - Car Audio Systemsd
edit: basically more ports = more friction loss which rases tuning, so you have to make the ports longer to compensate.
JL Audio - Car Audio Systemsd
edit: basically more ports = more friction loss which rases tuning, so you have to make the ports longer to compensate.
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Great Link!
I do recall reading about that,But I never knew how much of a factor it is.
I will read it more throughly later tonite so that I can fully understand it.
jer :
I do recall reading about that,But I never knew how much of a factor it is.
I will read it more throughly later tonite so that I can fully understand it.
jer :
I’m a bass reflex junky and have tuned many a speaker. You can certainly experiment with 2 different ports but agree with the consensus. You would be better off with a second speaker/box and tune it a different frequency. Additionally, I’ve had way better results with slotted ports.
This works well, and actually easier than round ports:
semi build the box, to the point where the front baffle board and “slot” (glued together like an “L”) can be slid up and down, which changes the port’s area/volume - using a generator/volt meter you can tune the box and then do the final glue up; you’ll need a good number of clamps. A dry fit, so to speak.
This works well, and actually easier than round ports:
semi build the box, to the point where the front baffle board and “slot” (glued together like an “L”) can be slid up and down, which changes the port’s area/volume - using a generator/volt meter you can tune the box and then do the final glue up; you’ll need a good number of clamps. A dry fit, so to speak.
just wondering did you ever actually build a box to see if the predictions in the program came out to match the actual f b,with the added 1". Just to see if the program was correct?
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