Early's DIY Sub

tryrrthg

Originally posted by Early B.
Thanks.

Can someone calculate the tuning frequency of this sub for me? I thought it was tuned for 20 Hz, but I'm not sure. The sub is 6 c.f. and has two 4" diameter ports 17" long. What other stats are needed for the calculation?

Probably around 24 or 25hz.

Does that 6 cu ft include all the bracing and port volume taken out of the total volume? If it doesn't, you're probably tuned a little higher.

Willow

Very nice job on the sub !

1 question for you, how did you find in relation to buying the equivilant pre-made what was the price diff ?

Early B.

Probably around 24 or 25hz.

What formula or software did you use to calculate this?

The 6 c.f. is the box itself. Don't know how much space the inner braces and ports take up.

Early B.

how did you find in relation to buying the equivilant pre-made what was the price diff ?

This DIY cost me about $400 to make. A comparably priced sub would be the Hsu STF-2 which I've owned. You simply can't compare the power and performance between a 10" and 15" driver, plus a higher quality amp and bigger box. I'd say you'd have to spend at least three times the money for the same level of performance.

gmorris

Originally posted by Early B.
This DIY cost me about $400 to make. A comparably priced sub would be the Hsu STF-2 which I've owned. You simply can't compare the power and performance between a 10" and 15" driver, plus a higher quality amp and bigger box. I'd say you'd have to spend at least three times the money for the same level of performance.

I've thought about this myself.

Does anyone know what a 9 cubic foot, 15" driver, 272 watt subwoofer, tuned to 18 Hz would cost from SVS? (obviously I mean what would the closest thing SVS sells cost?)

tryrrthg

Originally posted by Early B.
What formula or software did you use to calculate this?

The 6 c.f. is the box itself. Don't know how much space the inner braces and ports take up.

I used unibox. It's an excel spreadsheet that someone created. I'm using it to design my sub for the Atlas 15.

tryrrthg

Originally posted by gmorris
I've thought about this myself.

Does anyone know what a 9 cubic foot, 15" driver, 272 watt subwoofer, tuned to 18 Hz would cost from SVS? (obviously I mean what would the closest thing SVS sells cost?)

This is just a guess but I'll bet it performs around the PB2 subs performance. The 15" driver probaby displaces as much air as the two 12" ISD drivers, but that's just a guess. The two Plus drivers might out do a single atlas 15, but that's also just a guess. Maybe Doc will chime in...

Early B.

I used unibox. It's an excel spreadsheet that someone created. I'm using it to design my sub for the Atlas 15.

OK, but I'm just wondering why your 24-25 Hz figures differ from the fellas on the Ascendant Audio forum at www.soundillusions.net. They say a 6 c.f. box would yield 20-21 Hz. They are referring to Chad's own box design which is the model I used for mine. Are you taking into consideration both ports?

I downloaded unibox last week. Couldn't figure out how to use it. It ain't for the novice (not this novice, at least).

I like to keep it simple. Can I test this myself in the real world with a Rat Shack SPL meter and some low bass tones?

tryrrthg

Originally posted by Early B.
OK, but I'm just wondering why your 24-25 Hz figures differ from the fellas on the Ascendant Audio forum at www.soundillusions.net. They say a 6 c.f. box would yield 20-21 Hz. They are referring to Chad's own box design which is the model I used for mine. Are you taking into consideration both ports?

I downloaded unibox last week. Couldn't figure out how to use it. It ain't for the novice (not this novice, at least).

I like to keep it simple. Can I test this myself in the real world with a Rat Shack SPL meter and some low bass tones?

Yes, both ports are taken into consideration. I'd have to see his design to figure it out myself but I don't know why they would get different numbers. The software isn't an exact science, I'm sure.

You could test it yourself. You'd probably have to take the sub outside to get the best results, but I think you need to measure the freq response from about 1 meter away. once the response starts diving off a cliff then you've hit the tune point. Be careful when you get below the tune point because that is when the woofer can go beyond it's excursion limits.

Early B.

Thanks, tryrrthg. I might try that. I'll need some bass tones. Anybody know of a website where I can download them?

BTW -- here's the link for the sub's design:
http://www.frontiernet.net/~trtinkerer/overview.html

I changed it from a square to a rectangle.

tryrrthg

Originally posted by Early B.
Thanks, tryrrthg. I might try that. I'll need some bass tones. Anybody know of a website where I can download them?

BTW -- here's the link for the sub's design:
http://www.frontiernet.net/~trtinkerer/overview.html

I changed it from a square to a rectangle.

I'll check out the design some time this weekend.

here are the tones I use. Download all the individual tones.

http://www.snapbug.ws/sinewaves/

BlueMDPicker

Originally posted by Early B.
OK, got some final pics here...

On this one, can you locate the sub?

Very nice, EB!

Have you re-checked the hangar/mount on that elephant head?!? I'd hate to see a headline like "Atlanta couple found impaled in home theatre - apparent case of sonic suicide."

Early B.

Have you re-checked the hangar/mount on that elephant head?!? I'd hate to see a headline like "Atlanta couple found impaled in home theatre - apparent case of sonic suicide."

That's funny. But since I've heard that some people's subs on this forum have knock things off the wall, I am a bit concerned about some of the art in the room. Also, the fireplace screen rattles a lot, so I'll probably have to remove it whenever we watch a movie.
Kinda annoying, too.

BlueMDPicker

Beautiful room, to say the least! Congrats on a successful project.

gatemplin

Looks good Early. It's great to see more people interested in, and participating in DIY audio.

Early B.

Thanks Sid and tryrrthg for the bass tones. I'll try them out this weekend and post my results.

michael_w

Thanks for the tips early. I have all the tools I need (dad's a cabinet builder) and he cuts all his wood in his "shop"... 5' by 8' room :rolleyes: I have some closed cell foam tape stuff that I'll use to seal the port openings. I belive the port openings should be about 6-1/4" or something like that. My ports didn't come with instructions. Did you use some kind of pvc cleaner and cement to put them together? Does the atlas come with a sealant gasket thing or do I need to get some more closed cell foam to put around the cutout?

Dr. Spec

Run a reverse sine sweep and keep your fingers on the woofer and a hand over the ports. When the woofer excursion gets minimal and a lot of air is rushing from the ports, that is the tuning frequency Fb.

If you want to get more technical, take a mic and place it very close to the woofer cone and run a sweep. There will be an obviously dip in the response at the tuning frequency.

Early B.

Did you use some kind of pvc cleaner and cement to put them together? Does the atlas come with a sealant gasket thing or do I need to get some more closed cell foam to put around the cutout?

Yeah, PVC cement. Extremely strong smell. Works in seconds, so move fast.

The Atlas does not come with a gasket. Not sure if using cell foam around the cutout is necessary. I used it because my cutout was slightly larger than it needed to be.

Early B.

Didn't like the black finish on my sub, so I went to Advance Auto Parts and bought two cans of black/gray Duplicolor splatter paint designed for truck bed liners. Here's the first coat:

Early B.

Pic of the top:

janmike

I like that better than the black. Adds a touch on uniqueness. Nice job.

michael_w

Looks good. Kind of rock like I thought about doin that too but I think I'm going to try bed liner first. I thought the plain gloss black looked a little too fingerprintable/smudgy at certain angles but this looks great.

tryrrthg

Nice! I like that look. I might have to run that one by the wife.

I'm still designing my sub but my Atlas 15 is due to arrive tomorrow! Can't wait!

Early B.

Yeah, thanks. It's looking real good right now. I added a second coat last night and checked on it this morning. Now I can set drinking glasses and other stuff on the sub without worrying about messing up the finish.

Gonna leave it in the garage for a couple of days to remove as much of the paint odor as possible. I'll admit, I got a bit overzealous and spray painted the box without covering the amp and ports (I left the back of the unit black, though). Some of the splatter paint splattered on the binding posts, so I'll have to clean that up. Next time I'll be more careful.

BTW -- the truck bed liner is great stuff. About $5/can. Very easy to apply and looks awesome.

VR3

That truck bed liner smell will last for weeks on end...

After it is dry, spray some type of febreeze, etc on it and then wipe it down immediately.