NEw BOX for the Q18

Post by **GlassWolf** » Sat Mar 17, 2007 11:49 am

if you're worried about dirt and stuf getting in the port, just cover the outside end of it with acoustically transparent cloth.

if you use a ported enclosure, you NEED a subsonic filter.. unless you like the idea of gutting your sub.

subster87 · Post by **subster87** » Sat Mar 17, 2007 3:25 pm

glasswolf where can i get a good cost effective subsonice filter??? and thank you fishy for the info so im gonna go with your recommendations on the port length stick to 3 inches wide and 18.5 hieght. And a cover for the port will probably be nessacary even with the air velocity of a port it wouldnt make noise wiht acoustical transparent covers????

subster87 · Post by **subster87** » Sat Mar 17, 2007 3:26 pm

o yea bill told me to put the port facing toward the trunk lid, in my application that wont work so if i put the port facing to the side will that be my next best option????

subster87 · Post by **subster87** » Sat Mar 17, 2007 3:34 pm

ok update i called my local rockford dealer the power t1001bd has a 20hz subsonic filter i jsut have to make sure i have it turned on!!! lol im a tard sometimes i swear thanks fishy and glass wolf on that one!!!!

Fishy · Post by **Fishy** » Sat Mar 17, 2007 6:54 pm

I was going to suggest you port on one of the sides, but wasn't sure if you had the clearance. I'd think facing the rear of the trunk would be best,

http://www.teamrocs.com/technical/pages/aiming.htm

but I defer to those with more practical experience.

In 20 years of playing with car audio I've only had three enclosures that "worked" for me, a pair of ported 10w5's, a sealed 15w5, and the ported 10w3's I've now had for 8 years. Of these the 15w5 enclosure is the only one I built myself. It actually sounded the "best" of all three. It just didn't get as loud. I guess what I'm saying is you should take my recommendations with a grain of salt as they're based mostly on things I've read coupled with an Ocean Engineering background which included two sonar related acoustics courses. Theory is great and all. It can point you in the right direction, but "doing" is what counts. Just ask any tech. The surest way to screw up a project is let an "Engineer" become involved, hehe.

That being said, a picture is worth a thousand words. Post a couple. Diagrams would help too.

:)

Fishy · Post by **Fishy** » Sat Mar 17, 2007 7:31 pm

I'd be a little worried about putting grill cloth right over the port termination. I'd build me a grill cloth "box" that let the port breathe just a bit. If I understand acoustic transparent materials they're beneficial because they allow sound waves to propagate through them w/o reflections. Still, it'd seem to me anything covering a port termination would inhibit airflow, but if you allowed a little space and place it where the air velocity is not so high the effects should be lessened quite a bit. All the ported home loudspeakers I've seen leave some "breathing" room between the port and speaker cover.

Of course this is all conjecture. I've never tried it.

:P

subster87 · Post by **subster87** » Sun Mar 18, 2007 7:44 pm

ok soo ive been thinking i dont know how much clearance i would have facing ports toward the trunk ill post a picture or two tomrorow evening of the back half of the box in place and show you guys the design i cant find the damn camera or i would have done it sooner

Fishy · Post by **Fishy** » Mon Mar 19, 2007 1:46 pm

Its good to see you're taking the time to do things right. One question. How did you come upon 8.25 ft^3 gross internal volume? Is that right on or a guestimate? Its important to get an accurate measurement in order to get the tuning frequency right.

subster87 · Post by **subster87** » Mon Mar 19, 2007 4:30 pm

its exact im quite good at math i understand oddly enough the box came out to exactly 8.25 it took me a couple days to get it all right but yeah its sound weird but its right. And how many angles can i put in a slot port becuase to reach that length i will need at least two will that make a difference

Fishy · Post by **Fishy** » Mon Mar 19, 2007 5:19 pm

I was wondering how you figured out the volume of your spare tire well. Before I learned about "sand" I filled my JL stealthbox with water and poured it into a measuring cup, hehe.

I've never built a slot port but JL uses "L" ports all the time in their designs:

http://mobile.jlaudio.com/pdfs/11636.pdf

The only thing I might be concerned about is the "corner" of the "L". You'd probably want to radius the inside corner with a sander/grinder and fill the outside with something to smooth out the airflow(maybe calk in 1/4 of a piece of PVC cut lengthwise?). It may not be that big of deal however, if there's not a significant amount of energy loss due to eddies and such. Its also way inside so you probably won't have to worry about audible effects from any turbulence.

Best thing to do is ask someone who's built an L-port.