winisd help 4 15s

[ryanrj828]

I was trying to make a 4th order box for my 4 obsidian 15s, but cant squeeze out the extra cubes needed. So im back to a ported wall in my car, i've been fooling around with Winisd and for some reason if i set the cubic feet to 14.2 (thats after woofer, bracing, and port displacement) and tuning to 32 hz with 14.7 inches of port per cubic feet. The box seems really peaky, I'm not all to familiar with this program but the frequency peaks at 48 hz with +10.4 db, and rolls off to +2db at 32 hz. is this normal? is this an ok set up? it just seems off to me

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[ryanrj828]

anyone?

 

[ryanrj828]

come on someone has to have some insight

 

[Electrodynamic 10+ year member]

If you're going to listen to your system in an anechoic chamber you can trust what WinISD tells you. However, if you put your system (subwoofer system - woofer and enclosure) in a car or a home, etc, you can kiss that response plot that WinISD shows you goodbye. A 4'th order peaking at/around 45 Hz usually peaks in the mid 20's in a vehicle. Do not look at WinISD for in-car response plots.

 

[ryanrj828]

ok thank you for that information, since im building a wall is there certain things that i should be doing different compared to building a normal box? I tweaked a couple things last night so as of now ill have 16 cubes after all displacement with 16 inches of port area per cubic foot. Is that to small? i know typically it's suggested to use 12-16 but when i look at other peoples walls it seems like there port is way bigger then what i plan on doing. I want to make this system a ground pounder

 

[Electrodynamic 10+ year member]

Building a fourth order is tough and takes a LOT of tuning. You won't be able to build one design, play it, and everything be perfect. They are very very touchy alignments but when they are dialed in correctly they are very impressive. Larger port area raises tuning, smaller decreases, etc, but you have to balance everything. If you're shoving 4,000 watts to each driver and getting them to move full stroke on burps at 50 Hz you will need a lot of port surface area. If you are not doing that, you don't NEED a gigantic port area. As long as you are in for building and testing, building and testing, modifying and testing, modifying and testing, then a 4'th order is probably a good type of enclosure for you. If you are not ready to do the latter I do not recommend going forward with a 4'th order.