6 lvl 3 15s in 4th order

[02gmc92dcaudio]

I was thinkin 12.5 cubes sealed and 25 ported before subs , subs normal mounted in sealed part so il be just over 11 cubes seales and surports all around

[CJSmith]

Look at tuning lower then around 43hz, with a 2:1 ratio you should crush that frequency range and still have a nice roll off up in the mid 50hz area.

You want your sealed chamber to be whatever size causes it to have a sealed resonance the same as your tuning. Or another way of looking at it, you want your sealed impedance peak to be at your tuning frequency. Some box building software will be able to get a good estimate on what size sealed enclosure that would be but imo if youre investing this much into the build I would build up a small test sealed enclosure for one of the 15s and measure it until you find the correct size sealed per 15. It will probably be around 2 cubes but even being .25 cubes off in eaither direction can hurt your output by a few dbs. So be ready to test!

Thanks for taking me to school lol. I'm glad someone else chimed in to help bc box designs give me a headache, and I know net to nothing about 4th's. I just read him DC's specs.

[02gmc92dcaudio]

So how do i figure out what sealed side resonance is. I thinking 11.3 cubes with subs in i was i will have ,how do i go about this

[Namosh]

When I built a 4th order for my XL 15's I only did 1.5 cubes sealed side per sub. That seemed to work out well.

[mrd6]

Look at tuning lower then around 43hz, with a 2:1 ratio you should crush that frequency range and still have a nice roll off up in the mid 50hz area.

You want your sealed chamber to be whatever size causes it to have a sealed resonance the same as your tuning. Or another way of looking at it, you want your sealed impedance peak to be at your tuning frequency. Some box building software will be able to get a good estimate on what size sealed enclosure that would be but imo if youre investing this much into the build I would build up a small test sealed enclosure for one of the 15s and measure it until you find the correct size sealed per 15. It will probably be around 2 cubes but even being .25 cubes off in eaither direction can hurt your output by a few dbs. So be ready to test!

Thanks for taking me to school lol. I'm glad someone else chimed in to help bc box designs give me a headache, and I know net to nothing about 4th's. I just read him DC's specs.

Haha yeah, there are a few ways to design 4ths. This is the way I have read to go about it and it has turned out some great results in the 4ths I have built.

So how do i figure out what sealed side resonance is. I thinking 11.3 cubes with subs in i was i will have ,how do i go about this

You need to test it. There really is no way to guess perfectly. If I were building this system I would build a big sealed box say 3 cubic feet after displacement of a single 15. Put the level 3 in the box and measure the sealed resonance. It will probably be too low. So then shrink the box by some known quantity, for example say shrink it down to 2 cubes. Then measure it again, this time it might be too high so you know you will need more airsplace so you try 2.25 cubes next. Basically keep going back and testing like that until you nail down the sealed resonance that you want. The easiest and most accurate way to take the sealed resonance is with an SMD IM-SG, you can hook it up to the terminals and it will read out the resonance on the screen, doesn't get much better than that haha.

Once you have the sealed size for 1 15 just multiply it by 6 of course and thats what you've got.

When I built a 4th order for my XL 15's I only did 1.5 cubes sealed side per sub. That seemed to work out well.

Higher motor force subs generally can get a low enough resonance in smaller enclosures, so a level 3 will probably need a larger box.

[CJ18]

I would recommend 1.5ft3 sealed per sub with the Level 3 15s. I have done a 4th order build with 8 m2 Level 3 15s running on 1 12k and this worked out very well for me.

[02gmc92dcaudio]

Ok i did 1.7 cubes per sub might be a little smaller. so how do i figure out port? Do 15- 22 per cube ported for port area? Then what should length be ?

I would recommend 1.5ft3 sealed per sub with the Level 3 15s. I have done a 4th order build with 8 m2 Level 3 15s running on 1 12k and this worked out very well for me.