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Old 6th January 2001, 09:33 PM   #1
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As I said in my last message I plan building a subwoofer.
Today I purchased the following driver:
12" subwoofer
4 Ohm impedance
250 W Max. Input power
30 Oz. strontium magnet
P.P. injection cone
rubber edge
sensivity 92 db/w/m
freq. response: 30 Hz -3500 Hz
please note this driver is UNISTAR Acoustics.
Please let me know if this is good buiding a subwoofer, and if it worth 40$ (includding subwoofer crossover)
Please help me with that!
PS: How large should be the box.
What enclosure type should I use!
Thanks.
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Old 15th January 2001, 04:41 PM   #2
Eric is offline Eric  United States
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Lightbulb Subwoofer Design

Hi Revy,

Download the WinISD program from here http://www.linearteam.dk/winisd.html. It is simulation software for designing subwoofers and will model both vented and sealed subwoofers. All you need to know is the Thiel/Small parameters for your driver which should have come with it, or should be available on the manuf web page.

I used it to build my subwoofer and the results are quite impressive! I used a Mass 2012 S24 http://www.audiomobileinc.com/main.htm driver in a 145liter vented enclosure tuned to about 19Hz.

Since you've already purchased your driver, just plug the parameters into the WinISD, and play around for a while. The help file for the software contains a good deal of learing material and is highly recommended.

In general: Vented enclosures play louder (in dB)and play lower (in Hz). Sealed enclosures are smaller, more accurate (what some people call 'tight'), but will require more power to reach the same output levels as a vented enclosure, and will not play as low as a vented enclosure will. Same old "no free lunch" tradeoff argument.

You first need to decide what your goals for the subwoofer are. If you want it for mostly music, I'd recommend a sealed enclosure. If you want it for mostly home theater & DVD, I'd recommend a vented enclosure. Then decide how big you want it to be, and play around from there. My 145 liter sub is quite large, but I've disguised it as an end table next to the couch, so it really doesn't take up any "extra" room at all.

Eric

[Edited by Eric on 01-15-2001 at 10:46 AM]
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Old 15th January 2001, 05:43 PM   #3
Eric is offline Eric  United States
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Default Additional Resources

You may also want to spend some time at http://www.subwoofers.org/. There is a ton of good articles about general speaker design as well as subwoofers.
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Old 17th January 2001, 07:54 AM   #4
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Default Re: Subwoofer Design

Thanks for your reply.
I really don't know the T/S parameters.
WHat should I do?



Quote:
Originally posted by Eric
Hi Revy,

Download the WinISD program from here http://www.linearteam.dk/winisd.html. It is simulation software for designing subwoofers and will model both vented and sealed subwoofers. All you need to know is the Thiel/Small parameters for your driver which should have come with it, or should be available on the manuf web page.

I used it to build my subwoofer and the results are quite impressive! I used a Mass 2012 S24 http://www.audiomobileinc.com/main.htm driver in a 145liter vented enclosure tuned to about 19Hz.

Since you've already purchased your driver, just plug the parameters into the WinISD, and play around for a while. The help file for the software contains a good deal of learing material and is highly recommended.

In general: Vented enclosures play louder (in dB)and play lower (in Hz). Sealed enclosures are smaller, more accurate (what some people call 'tight'), but will require more power to reach the same output levels as a vented enclosure, and will not play as low as a vented enclosure will. Same old "no free lunch" tradeoff argument.

You first need to decide what your goals for the subwoofer are. If you want it for mostly music, I'd recommend a sealed enclosure. If you want it for mostly home theater & DVD, I'd recommend a vented enclosure. Then decide how big you want it to be, and play around from there. My 145 liter sub is quite large, but I've disguised it as an end table next to the couch, so it really doesn't take up any "extra" room at all.

Eric

[Edited by Eric on 01-15-2001 at 10:46 AM]
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Old 17th January 2001, 02:43 PM   #5
Eric is offline Eric  United States
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Default Need T/S parameters

Unfortunately, without the T/S parameters, you can't do anything - your results would be completely random and unpredictable - and most likely unsatisfactory. The simulation programs are based upon known pricinples of physics dealing with the driver, the enclosure, and the interaction between the two.

Contact the retailer you purchased the driver from and have them send you a copy of the T/S parameters. If the retailer cannot provide this information, find out who the manufacturer is for the driver, they can surely provide this information for you.

Attempting to build a subwoofer that performs well without this information is impossible!
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Old 18th January 2001, 09:29 PM   #6
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Default Re: Need T/S parameters

Ok, thanks for your answers.

I already have built a box for my driver and the results are
very poor.
I can bearly feel the bass. I used 18mm PAL wood for the 80l volume box. It is boomy, hard bass, it sounds like a emty box, I can't explain but it isn't like I planed!
Thanls for your help anyway.


Quote:
Originally posted by Eric
Unfortunately, without the T/S parameters, you can't do anything - your results would be completely random and unpredictable - and most likely unsatisfactory. The simulation programs are based upon known pricinples of physics dealing with the driver, the enclosure, and the interaction between the two.

Contact the retailer you purchased the driver from and have them send you a copy of the T/S parameters. If the retailer cannot provide this information, find out who the manufacturer is for the driver, they can surely provide this information for you.

Attempting to build a subwoofer that performs well without this information is impossible!
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Old 18th January 2001, 09:38 PM   #7
Eric is offline Eric  United States
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Lightbulb Give it another try...

Hi Revy,

I know its a pain, but give it another try! Boxes aren't that hard to build, and you can even build a cylindrical sub using "sonotube." Its like a giant cardboard tube that is used to pour concrete footings. That's how I built mine. Sometimes its a little hard to find, but the beauty is that you only have to construct a top and bottom circle to form an enclosure.

Check out http://www.io.com/~patman/sunosub.html for what I'm talking about. He has documented the entire process of building a subwoofer from sonotube. Mine is about 1/2 as tall as the one pictured. What cost me about $400 to build will easily outperform any commercial sub costing $2500-$3000!

Do some digging around until you turn up those T/S paramters.
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Old 19th January 2001, 03:21 AM   #8
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Lightbulb T/S Parameters

Hi.

There are some speaker building books that will tell you how to derive those specifications on your own. I have one by David B. Weems. It explains how to use some simple tools, like a cd w/ tones or a audio tone generator, multimeter, resistors, so you can figure out the Thiel/ Small parameters.

There are three major specs. that are needed,

1.)Qts: Total Speaker (or System?) Q (This is a combinaition of a few other specs. which might be helpful for more accuracy.)

2.)Vas: which I think has to do w/ compliance; it's harder to get because you need to build an arbitrary box to figure out this spec.

&

3.)FS: Free-air resononce


(F3: Freq cutoff at -3db is usful for building a ported box among other things.)

All DIY speaker books will show you how to use these three specs.

Best of all, it will be more accurate because what you find is for that specific driver. Most specs for drivers are averages. But as with all good things, it will be hard.

If you don't have any books maybe you can find one in a library. The net might have info on how to derive the T/S parameters own your own too.

Best of luck!!
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Old 23rd January 2001, 06:46 PM   #9
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Default HEY ERIC!!!!

Are you the one who built that sonotube 12" subwoofer that is posted on the internet with the HSU driver?

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Old 23rd January 2001, 07:05 PM   #10
Eric is offline Eric  United States
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Sorry, T-Bone. That one is not mine!

It seems that there has been a huge swell in the interest in sonotube subwoofers over the past year or so, so there are a great deal of people putting their projects on their web pages. I've not posted any pictures of mine, but its a 24" diameter tube cut to 23" high with a Mass 2012 12" driver. I used 2 layers of MDF for the top and bottom caps, and 6" pvc for my vent. Damn thing weighs in over 100lbs! The driver alone is 30 lbs, and I use an external amp to power it. Results are just AWESOME! I'll go head to head with ANY sub under $3,000...
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