port velocity help please

[CleanSierra]

1 to 1.25 is your sealed/ported ration..... 2cubes sealed to 4.2cubes ported is not a 1/1.25 ratio by the way...it's 1/2.1 again before port displacement

as for your port, I would go with a square port tuned to your resonant frequency

what frequencies are you trying to play that a regular ported box won't perform like you want?

Your ratio math is wrong. It's not 2.1:1, you have to include displacement of that port. His ratio IS close to basically 1:1 with port displacement considered.

OP, port area is really your key here with a 4th order. Why in the world are you tuning so damned low for a 4th? You're not going to get a great response, in my opinion with any music on a tune that low. you'll need to get that tuning into mid 40s to high 40s( again In my opinion) to get a musical tune.

[brent379]

I've been using win isd to help with the design/ porting... Like I said my goal is for the box to peak around 35hz

[CleanSierra]

I do agree with Stroupe about porting to resonant frequency. I don't think you'll get much out of an enclosure with such a narrow bandwidth, especially with the subs you intend to use.

[stroupe79]

1 to 1.25 is your sealed/ported ration..... 2cubes sealed to 4.2cubes ported is not a 1/1.25 ratio by the way...it's 1/2.1 again before port displacement

as for your port, I would go with a square port tuned to your resonant frequency

what frequencies are you trying to play that a regular ported box won't perform like you want?

Your ratio math is wrong. It's not 2.1:1, you have to include displacement of that port. His ratio IS close to basically 1:1 with port displacement considered.

OP, port area is really your key here with a 4th order. Why in the world are you tuning so damned low for a 4th? You're not going to get a great response, in my opinion with any music on a tune that low. you'll need to get that tuning into mid 40s to high 40s( again In my opinion) to get a musical tune.

that's what I was getting at...before any displacements he was at 2:1...I posted it backwards, as the previous poster had posted it...

your right, he should aim for mid/high 40s for tuning....

[CleanSierra]

I've been using win isd to help with the design/ porting... Like I said my goal is for the box to peak around 35hz

WinISD is dandy for a home enclosure, but the minute you put that enclosure into a vehicle, you've completely changed you're model and response. You're gonna peak where you're cabin peaks anyways, not where a box program will tell you that you peak. So if you want that box to be the least bit musical, I highly suggest bumping your tuning up. It's the same situation you have with regular ported boxes. The sub will still play below tuning, there is hardly any need too tune to like 28 Hz on a box just because you wanna" smash the lows". You will still have plenty of response with a mid 40s tune.

[brent379]

Ok I do see what your saying. Makes sense. So for port area I should get as close to half of my total cone area an tune to mid 40s right??

[CleanSierra]

That's a great start, yes. You want to be able to PRESSURIZE that ported section, while still having enough port AREA to feed the subs. Don't skimp on port, since that is gonna be your "window" to hearing your subs. That's opening to which you'll be getting your output through, don't be afraid to feed them some good port area. 4 10s with the xmax and mid 40s tuning, should want around maybe 80-100" of port? So an 8X10 to a 10X10" port might be about where I would start.

[brent379]

Ok half of my cone area is about 134 inches... Ill make the port interchangeable and start with a 9.5 by 13 which is about 123 sq in and tune between 43 and 47 and go from there! Thanks for the help!!!

[CleanSierra]

Perfect, I thought my guess might be closer. Let us know how it works out

[stroupe79]

now your heading down the right path!