Building a box for 2 Obsidian 15"

[DanP 19]

Just spent the past hour trying to understand the entire deal with box specs and this is what I got

Didn't really do any displacement math which is why I put in the Tuning Freq. at 26 Figured after all displacements highest it'd be would be at highest around 35 Hz

Anyone see any design flaws with this?

The Box is going in a 2002 Jeep Grand Cherokee Laredo

and I listen to Rock/Rap but more so Rap music.

Edited December 22, 2012 by DanP

[OuTLaWeD 110]

I would get all of the variables entered in so you have a better idea of the tuning and the net volume of the enclosure.

[DanP 19]

This thing is killing me I'm close to just ditching the port and going with a Sealed enclosure

[lithium 358]

tuning to 26 hz is really low. the website recommends 28-32 hz.

i'm plugging your stuff into bcae1.com's calculator.

[DanP 19]

tuning to 26 hz is really low. the website recommends 28-32 hz.

i'm plugging your stuff into bcae1.com's calculator.

Maybe im wrong with this but it would be 26 Hz before the adding in the sub displacement and the bracing displacements, so Empty It would be nearly 26 Hz but adding 2 15" Subs alone take up a lot of space reducing the actual tune of the box? Or maybe I'm just over thinking it.

[lithium 358]

http://www.bitpusher.in/?p=ported#bottom

works so much better!

[lithium 358]

tuning to 26 hz is really low. the website recommends 28-32 hz.

i'm plugging your stuff into bcae1.com's calculator.

Maybe im wrong with this but it would be 26 Hz before the adding in the sub displacement and the bracing displacements, so Empty It would be nearly 26 Hz but adding 2 15" Subs alone take up a lot of space reducing the actual tune of the box? Or maybe I'm just over thinking it.

ya it would raise the tuning but you already know the space the sub will take up so why not factor that into the net volume.

just use the calculator above. super simple

[DanP 19]

So apparently My port was off 3.5" now correct me if I'm wrong but the underlined part is that the ft^3 of space in my box? If it is I should probably make the box a bit smaller? as its recommended 2.5 to 3.75 ft^3 ?

[lithium 358]

net volume is after port volume and woofer displacement is subtracted

so yes. reduce the the net volume to 3.75 per sub or less.

[lithium 358]

also, i think port height should be 17-1.5 =15.5 where 1.5 is the top and bottom mdf

[OuTLaWeD 110]

what size amp are you going to have on these subs? you should always factor that in as well. if you are running higher power levels to them you want to keep the box volume down a bit, but if you are running around the rms range for the sub then going larger will be louder and more efficient. I vote 7.5 cubes@30hz

[ssh 924]

what size amp are you going to have on these subs? you should always factor that in as well. if you are running higher power levels to them you want to keep the box volume down a bit, but if you are running around the rms range for the sub then going larger will be louder and more efficient. I vote 7.5 cubes@30hz

That's pretty much null after accounting for average power being lower due to impedance.

[DanP 19]

Gonna be running these on an HFI 1500D so 1500 @ 1 Ohm

[OuTLaWeD 110]

what size amp are you going to have on these subs? you should always factor that in as well. if you are running higher power levels to them you want to keep the box volume down a bit, but if you are running around the rms range for the sub then going larger will be louder and more efficient. I vote 7.5 cubes@30hz

That's pretty much null after accounting for average power being lower due to impedance.

right, it will always be lower. you'll never see full power out of an amp in the real world.

[OuTLaWeD 110]

Gonna be running these on an HFI 1500D so 1500 @ 1 Ohm

you would be just fine running in that 7.5 cube net area. with that amp on them you will want to run a larger enclosure to get the most out of the system. the amp is alright, but it doesn't put out rated power so you'll need a more efficient enclosure to achieve a higher output. also, I would make the port opening at around 15.5Hx6W

[Impious 1,476]

what size amp are you going to have on these subs? you should always factor that in as well. if you are running higher power levels to them you want to keep the box volume down a bit, but if you are running around the rms range for the sub then going larger will be louder and more efficient. I vote 7.5 cubes@30hz

Design the enclosure for desired response, not the amount of power you are running.

[OuTLaWeD 110]

what size amp are you going to have on these subs? you should always factor that in as well. if you are running higher power levels to them you want to keep the box volume down a bit, but if you are running around the rms range for the sub then going larger will be louder and more efficient. I vote 7.5 cubes@30hz

Design the enclosure for desired response, not the amount of power you are running.

I do for both the amount of power and the response.

[Impious 1,476]

Power can be adjusted. Design for response.

[DanP 19]

Well as the first design I made had a flaw and you guys pointed that out, Figured I'd post this design as well and hopefully any flaws(if any) will be pointed out

Gross volume: 8.537109375ft^3

Gross volume after driver displacement (0.38): 8.157109375ft^3

Port displacement: 0.813828125 ft^3

Port final tuning: 32.49hz

Port length: 17.35"

Net Volume: 7.23ft^3

^^From Bitbusher

Edited December 26, 2012 by DanP

[altoncustomtech 773]

Dan sent me a pm and asked for some help with this enclosure since he'd seen where I've helped a few others out. He offered to send me $10 for my trouble, however I declined since I won' take any money for this. I'm only doing this for the fun of the hobby and for the experience calculating the enclosure specs and drawing in Sketchup, not to make any money or to try to make a business for myself nor take any business away from anyone else. I told him that if he used what I drew up and felt so compelled that he had to pay something for it then to send the $10 to the Leg Fund so at least it went to a good cause.

I drew up an enclosure for him 7.5cuft NET tuned to ~30hz with 110sqin of port area, double baffle with no flush mount per his request. It measures 40" W x 32" D x 18" H, the port is 7" x 15.75" and these are just the preliminary drawings.

Dan, let me know how close this is to what you're looking for and what changes you want to make to it.

[DanP 19]

Looks great, I'm not a very picky person and am 100 content with how it is now

[altoncustomtech 773]

Awesome, well here's the finished product. I took the liberty of giving it a finished look just to make it look good. While the top and bottom of the enclosure are cutout to the same dimensions you'll just need to cut a third panel to those dimensions to put on the top for the double baffle, nothing difficult.

Here's the cutsheet

Here's the enclosure with the top off and all the dimensions on each panel for clarity.

Here's a couple of pictures of it with a finished look.

7.5cuft NET tuned to ~30hz with 110sqin of port area, 40" W x 32" D x 18" H

[swift 501]

That should sound awesome! Love a good low tuned street box

[DanP 19]

Yeah looks great only one question, Whats the spacing on the subwoofer holes?

[altoncustomtech 773]

I guess I usually figure that people need to figure out the spacing on their own since there's always a possibility that measurements aren't quite perfect or something like that. I don't have any problem posting up the spacing measurements I used based on the specs posted on Obsidians website. I'd be sure to make certain that the spacing works before making cuts though. That's a LOT of wood to scrap if it's not right.