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I sure hope you're OK. Unflanged ends are more succeptible to port noise. How far the ends are away from the baffle simply effects the effective length of the port. I'm still confused as what your actual net volume is, but if your gross volume is 8.25 ft^3 before port displacement and you have 3 ports 14 1/2" long with 4 1/4" o.d. which stick out 2" beyond a 3/4" thick piece of mdf then it should be 7.96 ft^3(HP calculators rock!).

This yields a 27.6Hz tuning frequency with unflanged ends(full space) or 27.3 Hz with one end flanged(half space). Since your port termination lies within one diameter of the top of your box the actual tuning frequency should lie somewhere between the two.

How much internal depth do you have between the top and bottom of your box? If you've got 17" between the top and bottom(on the inside) you could mount 3 4" ports 13.5" long "flush" with the top of the box. If indeed the box has 8.25 ft^3 before port displacement that'd give you a tuning frequency just over 28 Hz. Port noise wouldn't be as likely with that scenario.

No matter. I'd just build it and see how it sounds. You can always shorten the port lengths form the outside later or possibly build up "baffles" on the top around the smokestacks to reduce port noise.

Oh and about the gall bladder. Don't think I needed it. Modern day laparascopic surgery is amazing. I already feel better than I did before the operation and am scheduled to work a triple tomorrow. Too bad. Not gonna have as much time for this now. Was a nice vacation.

:)

ok well im sitting right about right then for my ports. Box is all carpeted and tomorrow night ill start glassing it down to the floor and sealing things up. Then maybe tuesday i can finish the glassing and install my amps. O well hopefully things will be running by wednesday weather prohibitting. And with those smoke stakes how high out do you have them sitting? they are only out of the box two inches... And sorry about he galbladder bet you have felt better!!! lol well heal up quick get that setup in the explorer i kinda wonna see it!!!

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.

:)

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.

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

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

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

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 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.

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.