Ok. I'm new to WinISD but getting it figured out I think. My question is when sizing my port for net box volume and tuning Hz the number of subs makes zero difference in port size/length. Is port size calculated solely on net volume and tuning? Four 10" subs in one 5.7 cu. ft. tuned at 32Hz. Thanks for any help.
I’m almost certain that port length is the combination of enclosure volume, port area, and tuning, oh, and number of ports. Maybe choosing a circular or square port plays some role but I wouldn’t bet the farm on that.
You (or at least how I approach it) choose the number of drivers, the ballpark enclosure volume, and tuning. Add a reasonable amount of wattage and check the excursion. Add a high pass filter and adjust until the excursion below tuning is about the same as the excursion above tuning, you’ll see the cone excursion dip at tuning. Continue to increase power until the excursion is about 75% of the maximum, or if you’ve seen klippel measurements, whatever the well behaved cone travel is.
Now we pull down the port velocity screen and try to stay below 18 meters per second or so to avoid port flow issues. Make the port opening larger to reduce air velocity and the port gets longer, and the 1st resonance frequency gets lower. This is where you are potentially cussing Mother Nature. Watch out for the first port resonance as that should to be at around an octave above the subwoofer lowpass crossover.
At first, aligning all the separate parameters can be frustrating, especially as input power increases or a small enclosure is desired. Soon enough you’ll be cranking out functional subwoofer alignments efficiently. That is, if physics allows for the design of course.
You (or at least how I approach it) choose the number of drivers, the ballpark enclosure volume, and tuning. Add a reasonable amount of wattage and check the excursion. Add a high pass filter and adjust until the excursion below tuning is about the same as the excursion above tuning, you’ll see the cone excursion dip at tuning. Continue to increase power until the excursion is about 75% of the maximum, or if you’ve seen klippel measurements, whatever the well behaved cone travel is.
Now we pull down the port velocity screen and try to stay below 18 meters per second or so to avoid port flow issues. Make the port opening larger to reduce air velocity and the port gets longer, and the 1st resonance frequency gets lower. This is where you are potentially cussing Mother Nature. Watch out for the first port resonance as that should to be at around an octave above the subwoofer lowpass crossover.
At first, aligning all the separate parameters can be frustrating, especially as input power increases or a small enclosure is desired. Soon enough you’ll be cranking out functional subwoofer alignments efficiently. That is, if physics allows for the design of course.
Last edited:
No idea why someone would think this is important. What is important is letting the software auto calculate some of the values.
jeff
No; here's what I used way back when to calculate minimum vent diameter, then used next size up unless really close to a standard size: dv min. i.d. (cm) = ((20*(Sd*Xmax/10)^0.5)/Fb^0.25)/10
Sd cm^2, so 4x = big pipe and likely very long and IIRC WinISD factors in number of drivers when properly inputted
Xmax 5, 5.2, whatever
WinISD calculates some parameters as data is entered. If the data is entered in the wrong order it's sanity checks can fail. The ones it calculates may be slightly different to the ones on the drivers data sheet. Actually the version I used states this in it's help file and suggests a data entry order, There are a couple of tutorials around that do as well. The one I used was this one
https://midwestaudio.club/?page_id=14662
Multiple drivers in the same cab? No idea what WinISD does with that but.... I had an Xmax problem with a woofer and thought stick 2 in. Then via some web reading I realised that this would 1/2 the volume of the cabinetmmI was using, The example given was using 2 separate enclosures but why? Pointing out that if the divider is removed the speakers don't know providing the box is tuned to the correct frequency - the same f as if they were in separate enclosures.
https://midwestaudio.club/?page_id=14662
Multiple drivers in the same cab? No idea what WinISD does with that but.... I had an Xmax problem with a woofer and thought stick 2 in. Then via some web reading I realised that this would 1/2 the volume of the cabinetmmI was using, The example given was using 2 separate enclosures but why? Pointing out that if the divider is removed the speakers don't know providing the box is tuned to the correct frequency - the same f as if they were in separate enclosures.
Pretty much the problem I was having is I didn't realize that changing your number of drivers only influenced the m/s tables. Then you have to adjust port size and number manually to get m/s where you want them
The box size it comes up with is interesting. Another tutorial and verified with another package. WinISD tends to come up with a large one. The speaker sets one limit and what tends to happen is that there is a sort of "optimum" smaller volume. Some bass is lost but not much is gained by making the box larger.
If you go that way it's possible to tune a bass shelf - few db drop. This can extend the bass range. SPL drops a bit and then levels off.
If you go that way it's possible to tune a bass shelf - few db drop. This can extend the bass range. SPL drops a bit and then levels off.