What makes an enclosure work???

[hotshot27 10+ year member]

I have built a couple boxes now and i want to try and design my own. I have always used somewone elses plans or a tool online. Now i want to make my own design and concept similar to what a snail shell/folded horn does; increase efficiency. i dont have the money to go out and build 10 different boxes to experiment and see what combinations work the best so i thought i would ask for some of your personal opinions about what really matters when i come to designing an enclosure. I will set using 3/4 MDF as a constant, as well screws every 3'', woodglue liberally applied, sealant on the inside [silicone, resin, etc give me your opinion], and ported to somewhere near 30hz.

What i want to know is what factors [lamens terms or physics] are affected by port area? is there a such thing as too much??? I also wanted to know if you can make a ported enclosure too big?

I'm looking for the best factors to go with decent spl while maintaing the ability to hear distinct notes. my current setup is in my sig and it sounds great to me, but i'm scared that when i play tones around 15-20 hz that the woofers are being put in jeopardy. [i like low notes because they flex my car //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif ] So i'm looking for an enclosure that will be able to allow my subs to play low without extreme risk of damage [oh well that is what the extended warranty is for].

Sorry for the long post but i'm trying to experiment and learn the trade tricks of car audio withour spending a few years and couple hundred dollars to find out how everything works, so i'd appreciate any advice [other than leave it to the experts]

thanks in advance

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[nosaj070 10+ year member]

Alright, well first off designing a snailshell and a folded horn is substantially more complex than a basic ported box, I think you should learn the basics then work your way up to the extremely advanced boxes for two reasons. First they take a lot of trial and error. Second, very few people on this board could really help you with something that advanced, I'd be surprised if more than ten or so regulars could actually design a snailshell or folded horn.

Port area affects a few things, but the most obvious/annoying is port noise due to high velocities in a small port. As far as ideal size goes, its typically 15 sqin per cubic foot of enclosure volume.

Yes a ported box can get too big.

Yes you are risking severe damage to your subs by playing them below the tuning frequency, especially that far below tuning. In a ported enclosure below tuning there the enclosure does nothing to dampen the suspension of the driver, and you could rip it to shreds, especially if you are clipping it at 15hz. On top of that, you can't even hear 15hz (Unless you are special) so as far as music goes thats obviously not a realistic frequency.

If you search around this forum and google you will find all the answers to your questions and then some. JL's site has some good info do that is easy to understand.

Designing a ported box is simple, once you know the characteristics of the driver you can model it and know exactly what you need in a couple of minutes.

 

[hotshot27 10+ year member]

that was a very good answer, preety much everything i wanted to know. my only thing now is how much airspace. specs call for 1.75-2.25 for each sub so is 2 cf per sub ok or should i go the full 2.25 or even 2.5? [yes i'm one of those guys going down the road with my trunk rattling and windows moving and you can barely hear the words, if that helps in finding what is my ideal airspace.

^^^^^thanks for the in depth answer, i may still try to look into physics and try to find a balance of how it it all comes together [possibly a good thesis paper for my diploma????]