Building a Subwoofer?

[Omega]

Alright, i was wondering who has experience with this.

First off, i was looking at This subwoofer (http://www.allelectronics.com/cgi-bin/item/GW-2128/580/12%22#34;_120W_WOOFER,_8_OHM_.html) for the configuration.

To make it run off of a standard headphone jack (like the kind out the back of our computers) what kidn of amp would i need to be able to power it, and if you could also make a wiring diagram, that would be nice.

Also, how much does an enclosure normally run? i already have one, but i think my enclosure is for a 11" or 10" sub.



Any help is appreciated,
Omega

[DaveW]

I was looking into this myself. It's a little bit complicated making a good woofer enclosure, because in theory, it's supposed to mostly airtight to provide the best sound.

Unless you have a specific need for a custom woofer enclosure, then i'd be honest and have a look on ebay for a woofer with an amp already. When i get home i'll post some links to some Amp circuits. The thing about Amp circuits to remember is that they work on a logarithmic scale. So if you have a 30Watt amp, and you want to produce double the signal, then you need to move up to a 90Watt Amp. Note: This could be wrong. I'm not great with Audio.

Anyway, you're also looking at a bit of trouble with getting power to your amp as well. I'll help where i can but unless you have a specific need then i'd recommend getting your woofer from ebay with an enclosure allready.

Oh, and running it off a standard headphone jack won't be a problem at all.

-Dave

[xmastree]

IThe thing about Amp circuits to remember is that they work on a logarithmic scale. So if you have a 30Watt amp, and you want to produce double the signal, then you need to move up to a 90Watt Amp. Note: This could be wrong. I'm not great with Audio.
It's the ear which responds logarithmically to acoustic power.
From what I remember, doubling the power will increase the sound by 3dB

So, an increase from 10 to 20W will sound the same as an increase from 100 to 200. An increase of 3dB in each case.


Need a headache?
http://en.wikipedia.org/wiki/Decibel

[sega01]

hmm... as far as i rember, having an airtight of near airtight encloser lowers the volume by 3 db, and a vented encloser increases it by 3db. i would recommend walmart for a speaker amp. they aren't the greatest, but i got a 115 watt car amp for 20$ (originally 80$).

good luck!

[Omega]

okay, that car amp seems like it would work fine, but they run off of 12v (assuming they need power, i really don't know **** about amps), then i would need a converter (no way i am running it off of my PSU) from 110v AC to 12v DC.


Also, i realize that Ohms are resistance, but what does that represent with the subwoofer? (it says it's a 12", 120w, 8 Ohm).



Thanks,
Omega

[DaveW]

It's the internal impedence of the speaker-it's important for working out certain things. Everything has a resistance, and speakers usually have a resistance of 4ohms or 8ohms. 4ohms is best i think.

Anyway, if i remember correctly, you want it airtight in order to force the speaker's skin back to it's original position after the magnet has moved it. This will result in less echoing in the speaker, and much more crisp, clear sounds. If the space behind the speaker isn't airtight then i understand it can lead to the skin sort of 'penduluming' back to it's original position. If it's airtight it's forced back into position.

Maybe this is only important for tweeters?


lowers the volume by 3 db, and a vented encloser increases it by 3db.

Don't think i've heard that before-obviously i'm not an audiophile, in fact, i'm around 20% deaf. But i've been looking into speaker technology for the Integration Project and it seems strange that anyone would say a specific numerical value for a difference between airtight and vents-surely other things, like number of vents, type of speaker, size of enclosure, speaker size, etc. would make the difference? And obviously how loud the noise is as well...

...just seems to me those numbers must be wrong by logical thinking...

-Dave

[Omega]

Actually, i don't think vented or not makes that huge of a difference (not dB levels, but crispness etc) because a speaker will automatically return back to it's original position, plus it's a subwoofer, and i'm not looking for a subwoofer for voices or anything, i am looking for a sub for my computer (and i listen to alot of alternative/rock/metal etc) because my little 5" ain't cutting it, and, as a bassist, i love bass. like, alot. That's how i relax, is i get into the bass and really just feel the music, as opposed to listening to it.

=]

[DaveW]

The only books i have on the subject are targetted at audio engineers. I think they're for people who actually care about that extra 0.1 of a decibel.

It's hard trying to decipher what they mean, but i can't find an 'entry level' book on audio engineering anywhere.

-Dave

[xmastree]

Actually, i don't think vented or not makes that huge of a difference (not dB levels, but crispness etc) because a speaker will automatically return back to it's original position,
Hmm... I may be completely wrong here but... I think if it's sealed then it will be more damped and sound crisper. If the cone, as Dave says, can 'pendulum' it would lead to resonance, or booming at certain frequencies.
I've heard systems where the bass is up real loud and it just seems to be one note I can hear. Not sure why, but it has to be resonance of some sort.

Although I'm just guessing...

Talking of speakers, if a woofer is the bass, tweeter is the treble, what's the mid range? Well, that's the mid range... Why doesn't it have a name, the name of an animal somewhere between a big dog and a bird. A small dog, a yapper!

[Omega]

It's called either a plain speaker or a midrange driver.

Like this (http://www.allelectronics.com/cgi-bin/item/SK-214/580/2_1_4%22#34;_SPEAKER,_8_OHM_.html) or this (http://www.allelectronics.com/cgi-bin/item/GM-858/580/5.25%22#34;_60W_MIDRANGE_DRIVER,_8_OHM_.html)


Althogh the latter is more approiate for midrange than the former.

[xmastree]

That's my point, it ought to have a nickname.

Bass driver = woofer
High range driver = tweeter
Mid range driver = erm, Mid range driver. :rolleyes:

[Omega]

But you see, Woofer is just a shorter version of Subwoofer, which is another name for them.

And mid range drivers, i call those midranges.


Honestly, i don't care either way, i don't call tweeters that, i call them highranges(if you ever listen to me talk), and Subwoofers is the only thing i call by it's unofficial name

[TheAtomicMan]

But, you can also define a subwoofer and a woofer seperately. For example: I have some Woofers that only go down to 70 Hz for my car system, and my dad has some subwoofers that go down to 10 for his home system. It's really preference for sealed/ported, depending on what kind of sound you're looking to achieve. A sealed cabinet will give you more snap, but a port will give you more punch. Ideally, you should do infinate baffel, with the sub mounted in the ceiling or wall. But that's rarely an option. Make sure you build your box with at least as much, if not more volume than the driver requires, otherwise, you're limiting it's capabilities. You'd need an amp (since you're planning on running it out of the headphone jack). You can get a decent plate amp for about 300 money, I'm not sure what the low end market looks like.