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View Full Version : is there such a thing as ported fiberglass boxes?



ruckus
05-07-2005, 01:01 PM
Im wondering it appears every custom fiberglass box i see is sealed. I been reading and ported boxes are more common for SPL can you actually port a fiberglass shaped box like you would a sqaure mdf box? If so how would you figure out frequencies and such? Im making my first fiber box for a trunk and some 03C124 kickers i have laying around (until next year when i do my xxx or brahma system) and Im trying to get the best I can out of what I have laying around and I really want to play with fiber.

JimJ
05-07-2005, 01:03 PM
Sure, you can port a fiberglass box...You tune it the same way you'd tune a wooden box...

squeak9798
05-07-2005, 01:16 PM
The problem with porting a fiberglass box is that it's hard to determine the exact internal volume. Fiberglass is used to maximize space in oddly shaped areas. This is going to make it very difficult to determine the exact volume (yes, there are ways though). And to design a good ported box, you will need to know what the final net internal volume of the box will be. With 'glass boxes, you ususally won't know that until after the box is complete.

So, basically....yes, you can do it. It's not done very often because it's rather difficult to do.

whiplash
05-07-2005, 01:33 PM
Most people just build a ported box out of MDF and fiberglass that.

UndercoverPunk
05-07-2005, 01:35 PM
Just wait for REQ to come in here and tell us all about it... which he WILL do

WheresTheButta
05-07-2005, 01:37 PM
yeah somebody pls shed some light.... I'm going sealed because I need to glass to make things fit..... but I'd rather go ported if I could figure out a more simple way of doing that.

LightningStryk7
05-07-2005, 02:02 PM
somone actually did this with a xxx on the boards not to long ago. Yeah its posible. Just make it bigger then u think is ur cubic volume u want then u can add 2x4s or something to make the volume smaller to ur correct volume.

dbornotdb
05-07-2005, 02:05 PM
What if I was to share some info I have with you?






For starters, we use a quick reference "rule of thumb" and it usually works out great and can accurate. For example, if you have an enclosure (rectangle) measurements of 12x12x24 = 2 cuft, you would use this foundation (IE: bottom and back). When stretching your material over the rings you would get about 2/3's of this. 2cuft of airspace when your done. Its very close most of the time. Once its built, you can fill it with packing peanuts and transfer them to a square box to measure the volume the peanuts take up. Now that you have an airspace measurement you can configure your port size.

For pre build ported boxes, you will need to play with some airspce specs and calculate the range of sizes youll need in the event the box is bigger or smaller than you originally wanted. This is going to be a "give or take a 1/2 cube" situation. The basic port calculation will work for what you need...

To calculate the port length of a round port, enter the diameter of the port (D), the box volume (Vb) in cubic feet, and the desired tuning frequency (Fb). Here is the formula: (14630000*(D/2)*(D/2))/((Fb*Fb*Vb*1728)-(1463*(D/2)

If using a square port, just obtain the total area of the round port after calculations and match it to the area of the square one. Same for triangel ports, etc. If you round the edges on the end of the ports you use, subtract 1/2" from the length.






**pasted from another source**

Magmanta
05-07-2005, 06:15 PM
yea its possible, i did it =D i just kind of guesstimated the area, and built a mdf port into the box. Not very accurate, but it works good enough for me =D

What i was planning to do was make round ports out of pvc pipe, so i could change the tuning by adjusting how long the pipe was. Just make a ring for the port, like you do for the sub, and then you can glue the pvc into that once you figure out how much airspace you have. you can always use elbow pieces if the port ends up too long to be straight.

ruckus
05-07-2005, 07:44 PM
yea its possible, i did it =D i just kind of guesstimated the area, and built a mdf port into the box. Not very accurate, but it works good enough for me =D

What i was planning to do was make round ports out of pvc pipe, so i could change the tuning by adjusting how long the pipe was. Just make a ring for the port, like you do for the sub, and then you can glue the pvc into that once you figure out how much airspace you have. you can always use elbow pieces if the port ends up too long to be straight.

great idea. Im gonna do that.