NEw BOX for the Q18

subster87 · Post by **subster87** » Tue Mar 20, 2007 9:05 pm

i hate ghetto box i have made to many of them this one is suppose to be clean to an extent lol.... SO how long do these ports have to be exactly.... a little over 20???

subster87 · Post by **subster87** » Tue Mar 20, 2007 9:06 pm

and am i puttint a flare on top and bottom of these ports or just top? I could get the ports back out of the front for sure just take the sub out and pull them through.. but i hate hole pathcin and i cant glass the box down until its been carpeted SHIT!!!!

Fishy · Post by **Fishy** » Tue Mar 20, 2007 9:16 pm

What I think you ought to do is mount some HO train tracks on top of your box and have the locomotive cruise around red and white striped smokestacks.

http://maps.google.com/maps?hl=en&t=k&l ... 1,0.010131

Make a little industrial city-scape out of the thing, hehe.

But no, lol, although having the inside port termination flared would smooth out airflow you don't need it. Any chuffing there should be inaudible.

Fishy · Post by **Fishy** » Tue Mar 20, 2007 9:24 pm

subster87 wrote:and am i puttint a flare on top and bottom of these ports or just top? I could get the ports back out of the front for sure just take the sub out and pull them through.. but i hate hole pathcin and i cant glass the box down until its been carpeted SHIT!!!!

Well then we better get it right the first time............ or just install all three port configurations, carpet, then glass and "patch" the port openings you aren't using. All you should have to do is screw in an mdf plate over the "side" ports you're not using and seal a PVC end cap over the smokestacks. GHETTOOOOOOOO! hehe, but if sounds good who cares. You can clean up the looks later.

subster87 · Post by **subster87** » Wed Mar 21, 2007 4:38 pm

well i just ordered new metal covers for all my amps to get rid of the scratches and dings on them. It was like 25 bux no big deal but it should clean things up a bit. And ive decided to take my chances and put the 20.4 inch pvc ports blowing into the trunk lid i think it should be fine... Well wish me luck out to cut the finishing trim boards adn call it good. Saturday is comming up fast on me now

subster87 · Post by **subster87** » Thu Mar 22, 2007 7:31 pm

FI Forum says use 12-16 cubic inches for every cubic foot of box. My 8.25 cubic foot box needs about 120 inches of port to sit on the high end of that ratio. So 3 4 inch ports is what im gonna use each at about 12.5 inches. Any thoughts go ahead and fire away but thats what seems to be correct from scotts stand point

solacedagony · Post by **solacedagony** » Fri Mar 23, 2007 6:01 am

Try modeling it in WinISD so you can get some exact numbers for the tuning. It'll do all the math for you.

subster87 · Post by **subster87** » Fri Mar 23, 2007 4:34 pm

k well i got my ports in they are kinda a mini stack ill post pictures after its all carpeted probably sunday night. Ill be gone till then. Thanks guys. yeah i know but honestly for some reason i just dont get winsd im win sd retarded lol

Fishy · Post by **Fishy** » Fri Mar 23, 2007 11:22 pm

Sorry subster.

Finally went to the Emergency Room Wednesday after seeing two of my doctors about a mysterious lump on my right side and came out yesterday afternoon minus a gall bladder. Oops. Thought it was just some sort of hernia. Guess not. :P

Good thing is my calculator got here and it seems I'll have some time away from work to mess with things on my system too. Unfortunately no MDF lifting and cutting will be involved. Once I feel a little better I'll sit down and figure out some port calculations for you.

Got three Audison amps and four Seas Xovers laid out in formation on the kitchen bar and a stealth box sitting in the living room. Should look pretty cool in the Explorer if I can fit the amp rack in the rear storage compartment. Once I get my camera back from a friend on the west coast I'll post some pics.

So your'e goin with the smokestack idea huh? OK, hehe.

Fishy · Post by **Fishy** » Fri Mar 23, 2007 11:41 pm

Quick calculation in WinISD:

To get a 28 Hz tune with 3 4" ports you need a little over 14 1/2" lengths for unflanged ends(smokestack) in a 7.7 ft^3 net volume. Unfortunately you'll be hitting 26+ m/s @ 28 Hz with 1000 watts and 19 m/s with 500. This is with a 12 dB/oct subsonic filter at 20 Hz as well! You may be fine for every day listening, but if you crank it you're probably going to get some port whistle. Remember 5% of the speed of sound or about 17 m/s is the limit you want to stay under. I'll post the graphs later.

Oh WinISD isn't that difficult. The hardest part of designing a box is actually figuring out volume. If you can handle that, with some time and effort you should be able to handle WinISD no problem. I'm sure there are plenty of WinISD users here who could help get you up to speed. There's plenty of info here as well:

http://linearteam.proboards12.com/index ... ard=winisd

A little searching there combined with checking out the program's FAQ's should answer any questions you might have. If not there's always us.

:)