8" Subwoofer cabinet schematics needed.

[hernanstafe]

First of all i introduce myself since i'm new to the community, My name's Hernan i'm 19 and i love evrything related to audio, amplifiers, speakers, etc, i've built some things of my own and now i want to build a subwoofer with an old 8" speaker i have at home. The problem is i can't find any vented subwoofer cabinets for an 8" speaker. I want to build one similar to those 2.1 speaker system for computers but i can't find any schematics. Does anyone have an idea where i can find them? I'd apreaciate that a lot.
Thanks in advance.

[AKN]

Hi hernanstafe and welcome!

First of all your box configuration is determined by woofer parameters, intended use and your sound preferences, hard, loud, soft, low etc.
No universal box for every woofer exists, at least not if you expect some quality sound.

I'll start with, do you have any specs such as Thiele-Small parameters for your woofer?

[hernanstafe]

Ok 4fun, thanks a lot for your reply! Now i'm gonna answer what you asked me:

About the woofer parameters, sadly i don't have them. I Can still send you a picture of the woofer (i'm don't think that'll help) since it was a very cheap speaker i bought ages ago and it doesn't come with any kind of technical specs. Actually, it's not a subwoofer it's just a woofer, but since i have it there doing anything and i got just 1, i'd like to try to do a sub anyways, even if it doesn't have the bestest sound.

Intended Use: Well i'm trying to do a multimedia speaker system for my computer, you know, a subwoofer and two satellites. It's of course for home use, to use with a computer to be precise (of course i'll also build an sub. amp too).

Sound preference: errr that's a tough question lol, it's difficult to explain with words. Of course i'd like to to sound loud, but also i want good hard bass, you know a good "punch" sound lol, i don't know if i'm being clear. I've heard some Edifier, Sony, Aiwa speaker systems for computers with subwoofer (tho they were 4" subs) and they all sounded nicely, so i want to do something similar to that (i'm assuming with a 8" speaker the bass can be even better).

So that's it for now, if you need something else please let me know, i'm sending you my email adress on pvt in case you need pictures of the speaker or something, you let me know.
Thanks a lot for your help.

[Cal Weldon]

Hi hernanstafe,

It's pretty hard to suggest what size of cabinet for you without the parameters but you can always just wing it if you have to. If I were guessing, I would start with about a 1 cu ft. cabinet, maybe 1.5 if there's room. Start with a test box, and you can adjust the internal volume by adding pieces of wood until you're happy. Then calculate the volume of box by subtracting your internal pieces.

BTW, this is the wrong way to do it but if you don't have any info on the driver, it's a guess and by golly. Maybe.

How loose is the supension in comparison with other drivers?

[zlast]

If you have a multimeter and a 10 ohm resistor you can measure the speaker parameters as outlined here:

http://sound.westhost.com/tsp.htm

tone generating software:

http://www.nch.com.au/tonegen/index.html

[AKN]

hernanstafe,

If you are able to do what zlast suggested you have come a long way. Next step is some geometric measurements of the speaker then off to some simulation program.
Please do mail some pics. Got no mail from you, maybe you are not allowed to mail through the mail button yet?

[hernanstafe]

Cal Weldon, that 1, or 1,5 cu ft cabinet is closed or vented? and how big is the vent? and the suspension is quite hard.
I might just try to calculate the thiele-small parameters like zlast told me to...like i said i'll TRY to do that lol!!
Thanks a lot guys!

Pd: 4fun! yeah i can't send pvt messages yet.

[Cal Weldon]

If you can measure the T/S parameters, do it.

If the supension is very stiff, you may have a large Vas. It may also have a high Q but we don't know for sure. The box is sealed as there is no point in trying a vented box without the specs.

You are free to post and email now.

[hernanstafe]

Ok guys, there you go some pictures of the speaker i just took, they're in a rar file


http://rapidshare.com/files/14596966/Speaker.rar.html

Some other specs i found on the box, idk if they're any good:

Music Power: 200W Max
Impedance: 4+-15%Ohms
Frecuency Response: 55-55000Hz
Charasteristic Sensitivity Level: 91+- 2db

Hope this is useful for something lol.

[AKN]

Cal,

If the supension is very stiff, you may have a large Vas

Oh, it's the other way around.
Vas is the volume of air that has the same compliance as the speaker's suspension, so stiff suspension means less Vas.

hernanstafe,

Ok, saw the pics.
It looks like a driver for car use, open air type, those drivers usually have high Q less useful in a box unless it's very large.
I hope I am wrong.
Is it possible for you to do the measurements suggested?
The values you will get tells very much of your driver.