Air Velocity on WinISD Pro

[Triticum Agricolam]

Brace option #1 is exactly how I would do it.

To post a file on here you can use something like dropbox and post a public link, or you can use a site like www.filehosting.org and then post the link they give you. Filehosting.org is probably the easier of the two if you aren't already a dropbox user.

[mrazandrewm]

Cool. Here's the link. Thanks.

[Triticum Agricolam]

Thanks for the link, I took a look at your design. From a layout perspective everything looks great. You have a net airspace minus the sub of 1.03 cubes. With sub displacement this puts you at .87 cubes and you will be tuned to about 34 Hz.

I'm concerned your port area isn't going to be enough. With 18 sq in your port velocities are going to get over 40 m/sec on 1500 watts. It will only take 750 watts to get over 30 m/sec. If you widened your port from 3 to 4 inches for a total of 24 sq in of area that would get you where you need to be, but your port would have to get another 10" longer in addition to being wider and I'm guessing you don't have the space to make the box bigger.

[Joe X]

Besides that OP what vehicle is this box going to? looks like something for a hatchback but i see you have a truck.

[mrazandrewm]

Sorry for the late reply guys. I own a 2013 F150 Ext. Cab truck. Enclosure will be going under the rear bench on the driver's side. Subwoofer will be upfiring, and the port will be front firing. This will be my first time building an enclosure for a vehicle.

Triticum, I used Torre's box calculator and I modeled the enclosure based on what it gave me. I can include a ss of the window and the sketchup file of the touched up enclosure. Here's the ss:

Here's the link to the revised enclosure: LINK

[mrazandrewm]

I also changed my mind about the subwoofer. I'll either be using (1) SA-10, (1) Incriminatory Audio Lethal Injection 10", or (1) FI SSD 10" on 1000w RMS. I'll post up all three WinISD Alpha files later in the day.

[mrazandrewm]

Forget the above posts. I have an enclosure designed that is .9998 FT^3 tuned to 30.81 Hz. This enclosure sounds like it'll dig deep. So what should I set the subsonic filter at? Hope you guys have a good holiday!

[brent379]

set the subsonic at 24. they should be set half an octave down from the tuning frequency.

one octave down from 30hz would be 15hz. half of 15 is 7.5..... so 30-7.5=23.5

so either 23 or 24 would work.

little tip about port velocity that i have learned thru using winisd....when modeling the velocity i like to keep it under 25m/sec...and if you put in both your lowpass and highpass filters it will drop the vent volocity quite a bit and make it more reasonable.

for instance: my current box build...2.84 cubes net at 36 hz with 2 dc lvl 3 12 m2's on 1800 rms.....with no high/low filters i would need a port area of about 95 sqin to keep velocity in my liking.

with a lowpass of 70hz and a subsonic at 27.... 52 sqin of port at 36 hz puts my max velocity at 22m/sec.

not sure if you already know this or not but reading thru this thread i did not notice anything about high/lowpass filters. make sure you put them in winisd.

[mrazandrewm]

Brent, I have never learned how to input filters in WinISD. Do I just go to the EQ tab, add new, click highpass (for subsonic filter) and input 24 Hz? What order should I do? As for lowpass, add new, click lowpass and input whatever I want the crossover frequency to be? Also, what order for lowpass? Thanks.

[brent379]

Yes that is correct! Leave both filets selected to the Butterworth option. Don't even mess with it. Just put your low pass frequency in and your highpass in.