My summertime DIY project. (1 Viewer)

[bobbyg2]

Since school is about to let out, I'm going to replace it with a little DIY subwoofer project. Not going to be anything big, probably just a little 10" sub to decide if I like to build DIY subwoofers. My budget isn't too big, just ~$100-$200, just in case I wire it up wrong or something and send a driver to its grave, it wont be the end of the world.

What I was thinking was a Dayton 10" DVC Subwoofer with a Dayton 100W Subwoofer Amplifier($117 combo).

Another combination I was looking at was a 10" Shielded Paper Cone Subwoofer with a AudioSource AMP100 2-Ch Source Switching Power Amplifier ($116 combo)but seeing as the price of that driver is only $16, I'm not sure if it would be as good of quality as the Dayton.

As for the enclosure it will be going into, I had mixed thoughts about either ported or sealed. Sealed would be easier to build but would be untunable. Ported would be harder to build with would probably sound better due to the tune ability. I'll probably end up going with a 12"H x 12"W x 15"D (internal) sealed enclosure, which should be a decent enough size.

The receiver I'll be using it with would be my computer, which I have a cable to connect from the computer to the subwoofer. The speakers I will be pairing it with is the Logitech X-530 (a friend gave them to me for free a few weeks ago.) which will only be used until next summer when I begin finding a receiver and speakers to replace them.

Thanks in advance.

 

[bobbyg2]

I used WinISD to model the Dayton (I hope I did it right):


Driver Parameters


Gain/Driver


Box/Phase Plot


SPL/Plot


Box dimensions

I don't know how accurate those would be, seeing that I don't know if WinISD factors in the driver displacement.

 

[Robert_J]

WinISD does not factor in driver displacement. Since it varies from driver to driver, it doesn't know. You need to factor that in before building the box. WinISD is giving you the net box size without driver or brace displacement.

You should also adjust the max and min range on your graphs so that they display better. You also need to tell WinISD that you are going to use 100w as your input and graph driver excursion. Finally, you should remember that your plate amp has a built in sub-sonic filter probably set at 20hz. Unless you can import that into WinISD (you can with Unibox), then your 20hz and below response is not accurate.

-Robert

 

[bobbyg2]

Is Unibox better than WinISD?

 

[Robert_J]

According to Dan Wiggins, Unibox is as accurate as some of the more expensive programs that he uses.

-Robert

 

[bobbyg2]

Would it really matter all that much if my sub is sealed? Shouldn't the amount of space in that box be enough for that little sub, anyways, regardless of driver/bracer displacement and the lowpass filter thingy on that amp?

 

[Robert_J]

WinISD is getting you very close. It's all about how accurate you want to be. I do tend to go a little towards obsessive/compulsive when I am designing something.

-Robert

 

[bobbyg2]

I don't have Microsoft Excel, so I guess WinISD is as close as I'll get to the best.

Anyways, would this little driver be able to go as loud (112db) as WinISD is telling me? Or is that just how loud it would get without bottoming out/bursting into flames?

 

[Robert_J]

112db at 100hz is easy. With room gain, the lower your sub plays, the more the room helps. So you should be able to better WinISD's predictions down low. Did you chekc your excursion graph to make sure you aren't pushing the driver past it's mechanical limits?

-Robert

 

[bobbyg2]

I can't find an excursion graph.

 

[SethH]

If you want to use Unibox without Excel go download OpenOffice (openoffice.org) and you should be able to use Unibox in the Calc program. Just make sure you enable all the macros and you should be good to go.

 

[Robert_J]

Are you using WinISD or WinISD Pro? I know the Pro version has it.

-Robert

 

[bobbyg2]

Ah, yeah, I had the normal version, now that I downloaded the Pro version, it's telling my my variables are inconsistent...

 

[Robert_J]

Check the Help. There should be an order in which you enter the parameters and WinISD will calculate missing parameters from there. At a point, it will have everything you need. You probably only need to enter Qms, Qes, Fs, Sd, Re and maybe Vas.

-Robert

 

[bobbyg2]

Do you know of a site where I can learn what those letters mean?

 

[Robert_J]

Those "letters" represent different parameters commonly known as Theile/Small parameters. Sometimes shortened to T/S data.

History and definitions - Thiele/Small - Wikipedia, the free encyclopedia
Less technical definitions - Eminence - The Art and Science of Sound
Another good thing to home - Hoffman's Iron Law - LDSG Appendix*A

-Robert

 

[bobbyg2]

I used those variables that you listed, and I got the excursion graph:



Somthing tells me 100 watts may be a tinsy too much power... I tried different wattages and the only way to get 20Hz under 6mm is at 25 watts...

 

[Robert_J]

Then you need either a smaller box (see Hoffman's Iron Law above), a smaller amp or a driver with more excursion. A less used option would be to adjust the amp's input so that it never puts out enough power to over drive the sub but that's not always practical. You will be tempted to push it. I remember when I was younger, friends would always come over and mess with my stereo's settings.

Try a few other 10" drivers and see how they perform.

-Robert

 

[bobbyg2]

A .5 foot enclosure seems to have fixed the problem, what would be the dimensions of that?

 

[Robert_J]

There are an infinte number of possiblities. Have you taken geometry and algebra yet? First, you know that one side of the box must be large enough to mount a 10" sub. So, let's make that 12" by 12". Now we have our hight and width. Since we use internal dimensions to determine enclosure volume, we have to subtract 1.5" (3/4" MDF on both sides) to get 10.5" x 10.5" or 110.25 sqare inches. We know we need 864 cubic inches. How do we know that? A cubic foot is 12x12x12 or 1728 cubic inches. 1728/2 = 864. 864/110.25 = 7.84". So your box needs to be 7.84" deep (internally). So outside dimensions will be 12" tall, 12" wide and 9.34" deep.

That's great that you are keeping your excursion under control but look at your system's Qtc. That's over 1.0. That will give you more of a boomy bass. I like a Qtc closer to .5.

-Robert