This should be pretty straightforward but I want to make sure I'm getting it right, so I figured I'd ask here before I started cobbling something together.

I want to build a new box for one of my old Coustic HT-812 subs. It would be easy enough to just make a square box, with the sub firing out the side (and I may still do this just for the sake of simplicity) but I have a Jeep with a soft top and I don't really want the sub visible, so I was thinking about going with something downfiring, and carpet the box black to match the rest of the interior.

According to the literature I have, for an "Optimally flat with heavy fill" box it recommends it to be 1.27cf with a 4" diameter port 17.9" long. Seems simple emough, but I'm sure I'm missing something.

I can calculate the internal volume of the box when I'm building it easy enough, but I don't know about woofer and port displacement.

If there's somebody here who's sporting enough to slap together a simple design that would be super awesome, or even just some info about getting my volume correct would really help. I only want to do this once, so I want to get it right.

I still have the literature for the sub, so if there are any specs needed just let me know. Any and all help is greatly appreciated.

Thanks!

 

Nobody huh?

Well maybe somebody can at least answer a shorter question. Would it be simpler to build the box with a slot port instead of a round ABS one? The last time I had these subs in a proper box with the ABS port I had to have an elbow to get the proper port length.

 

This should help you. <Click Port displacement equates to .583 not sure about the sub.

 

slot port is simple. thats what I would go with. As for boxes, I would design something that is down firing, this was the shock waves from the sub will transfer into your jeep and you'll feel it more. This will help for when you have the top down, and like you said, it won't be as noticeable.

Good luck

 

Sweet, this is definitely helpful!

The sub is an old Coustic HT-812 that I've had since high school. I beat the snot out of them for about 10 years until I got the Jeep in September and I've just had them kicking around since. I figured I might as well dust one of them off, build a new box for it and give it another shot at life. If nothing else, I'm quite sure it'll beat the heck out of the stock sub/enclosure I'm dealing with right now.

 

if ur going to give help or advice atleast give correct help and advice...ive never been able to get over a half cube of displacement on a 4" port 17.9" long... but hey maybe you can teach me something new.

most abs pipe is 0.25" thick or so... giving it a total diameter 4.5" now doing simple math for area = pi*r^2 = 3.141592654*2.25^2 = 15.9 in. sq.

now to get volume =area * length 15.9 * 17.9 = 284.61 in.cu. to convert that to ft.cu divide by 1728 = 0.165 cubic feet

i could be wrong

 

lol, nope your right. Just rechecked Bass Box, I had the thickness still set for wood.... Your right, I may want to double check that before posting numbers, I thought that seemed like a big number????? My apologies Geezle I was not trying to mislead you. Just checked in a little too big a hurry and didn't change all the settings. I should have known better.

 

The only thing that I would add for calculating port is to subtract wood thickness from port length. This also effects overall Vb. So when you remove the wood thickness from port length you have .158 for a port displacement. Using .25 as the material thickness.

Again MTA thanks for the schooling.... lol I guess this is why people should use pen and paper vs programs. There's no presets with a paper and pen. lol

 

Haha thanks for sorting that port business out for me guys, I wonder what it would have sounded like with that much port area!

I really want to get this box built but my work situation is keeping me too busy for it at the moment, but as soon as I have a spare day this is going to be my project.

Now I just still need to figure out the actual design for it!

 

It would not have changed the port area, just would have made you design a larger box to accommodate the extra (wrong) port displacement. Basically it would have made the subs play in a larger box than anticipated. Also it would have changed your port frequency seeing as the port is dependent on the enclosure volume for frequency response.

eg. 4" port, 1.25cuft box, tuned to 36hz, = 17.978" length. If you added an extra .5cuft to the enclosure to accommodate the wrong port displacement it would actually be tuned to 30.5hz using the same port.

I even double checked this info, It's good. lol

HTH