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My summertime DIY project.

#1
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5/18/08 at 6:51pm
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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.

"Bobby is and idiot"
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#2
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5/18/08 at 11:14pm
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Re: My summertime DIY project.

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.

"Bobby is and idiot"
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#3
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5/19/08 at 5:50am
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Re: My summertime DIY project.

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
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#4
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5/19/08 at 11:47am
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Re: My summertime DIY project.

Is Unibox better than WinISD?

"Bobby is and idiot"
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#5
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5/19/08 at 1:57pm
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Re: My summertime DIY project.

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

-Robert
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#6
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5/20/08 at 4:14am
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Re: My summertime DIY project.

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?

"Bobby is and idiot"
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#7
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5/20/08 at 5:36am
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Re: My summertime DIY project.

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
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#8
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5/20/08 at 9:47am
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Re: My summertime DIY project.

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?

"Bobby is and idiot"
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#9
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5/20/08 at 1:53pm
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Re: My summertime DIY project.

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
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#10
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5/20/08 at 7:48pm
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Re: My summertime DIY project.

I can't find an excursion graph.

"Bobby is and idiot"
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#11
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5/21/08 at 4:17am
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Re: My summertime DIY project.

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.
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#12
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5/21/08 at 5:33am
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Re: My summertime DIY project.

Quote:
Originally Posted by bobbyg2
I can't find an excursion graph.
Are you using WinISD or WinISD Pro? I know the Pro version has it.

-Robert
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#13
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5/21/08 at 8:03pm
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Re: My summertime DIY project.

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

"Bobby is and idiot"
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#14
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5/22/08 at 5:57am
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Re: My summertime DIY project.

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
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#15
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5/22/08 at 10:50am
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Re: My summertime DIY project.

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

"Bobby is and idiot"
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#16
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5/22/08 at 1:41pm
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Re: My summertime DIY project.

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
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#17
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5/23/08 at 8:35pm
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Re: My summertime DIY project.

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...

"Bobby is and idiot"
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#18
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5/24/08 at 5:07am
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Re: My summertime DIY project.

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
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#19
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5/24/08 at 7:35am
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Re: My summertime DIY project.

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


"Bobby is and idiot"
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#20
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5/24/08 at 10:59am
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Re: My summertime DIY project.

Quote:
Originally Posted by bobbyg2
A .5 foot enclosure seems to have fixed the problem, what would be the dimensions of that?
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
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#21
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5/24/08 at 3:06pm
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Re: My summertime DIY project.

No way of getting a .5 Qtc without watching the cone shoot through the wall... So, I guess I just need a different driver?

"Bobby is and idiot"
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#22
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5/24/08 at 8:45pm
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Re: My summertime DIY project.

Have you defined any goals? What will this sub be used for - music, movies or both? How large is the room? How loud do you want to listen? Unless you define those, you are just building to be building. If you are on budget and want to learn, build a few boxes. The .5cf is great to start out with. Then build a larger one with a Qtc of .707. Finally the largest with a Qtc of .5. Learn how each sounds. That way when you graduate to largers subs, you will be able to relate those graphs to real experience.

-Robert
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#23
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5/25/08 at 10:15am
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Re: My summertime DIY project.

I want to use it mainly for music with occasional gaming, I'm in a small room (about 11' x 9'), I want it to be loud enough to fill the room but not so loud as to get complaints from the neighbors, and I don't really have the room for a gargantuan sized enclosure that will take up the whole room. But, I want it to be cheap, as I will be moving into my own house next year and will be putting this in my bedroom and buying a bigger and better one for the living room.

"Bobby is and idiot"
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#24
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5/25/08 at 2:11pm
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Re: My summertime DIY project.

Build the .5cf box. The hump in the frequency response will be beneficial for special effects of games and that @#$# rap music you kids listen to now days.

-Robert
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#25
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5/25/08 at 4:50pm
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Re: My summertime DIY project.

I don't listen to rap.

So, that Qtc is fine for my use? Just, not all that great for movies? I'm probably never going to use it for movies, anyways.

Edit 2:

I calculated the internal volume, and 12"w x 12"h x 6"d seems to be me best bet. I wouldn't be able to fit that driver on a 10.5" piece of wood, the outer dimension of it is 10.6".

I'll be building this enclosure in a week or two.


"Bobby is and idiot"
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#26
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5/25/08 at 8:18pm
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Re: My summertime DIY project.

Sorry, but it seems like this is turning out exactly how it did last thread I made. My mom gave me permission to do this, but now that I'm ready to build the thing she refuses to give me permission. Same reason as last time, I must save up for a car. Sorry if I wasted your time, next summer when I'm out of the house for sure will I build a subwoofer.

"Bobby is and idiot"
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#27
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5/26/08 at 6:38am
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Re: My summertime DIY project.

I can surely understand having a project vetoed at the last minute. My wife does that to me sometimes. But it is usually a very impractical project.

Speaker building is a very good hobby. I started with my first car back in '86 and it has been going ever since. It keeps my math and geometry skills sharp. It has also taught me to use tools that have benefited me as a homeowner and the confidence to tackle most projects. For example, when we moved into this house we had to have curtains for 7 arched windows. Arched curtain rods are over $150 each (do the math!). Using my woodworking skills as well as my knowledge of the different projects I have seen on the forums and TV, I built my own. That's right, all 7 for under $50.

Just wait patiently and next year start your project. In the mean time, start watching New Yankee Workshop on PBS. You may never build a table and chairs but you will see how a professional uses his tools.

-Robert
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#28
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5/26/08 at 10:19pm
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Re: My summertime DIY project.

Do you know what days/times that show airs?

"Bobby is and idiot"
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#29
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5/27/08 at 5:28am
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Re: My summertime DIY project.

It varies by local PBS affiliate. If you have a cable box/satellite receiver/etc with an EPG (electronic program guide) just browse through the shows on the weekend. It will be there somewhere.

-Robert
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#30
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6/4/08 at 12:17am
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Re: My summertime DIY project.

I think I may have convinced my Mom to allow me to build a subwoofer.

I was looking at the Dayton Reference Series HF 10" in a 5ft^3 ID enclosure, and a 240W amp.

Parts Express: Dayton RSS265HF-4 10" Reference HF Subwoofer 4 Ohm

Parts Express: Dayton SA240 240W Subwoofer Amplifier

Only thing is, how would I be able to get a 20Hz High-pass filter? It was the only way that I could get the driver to not bottom out under 20 Hz.

Here's some graphs:





Forgot to grab a snapshot of the filter, but you get the idea.

Reason why I went with a 12" x 1.5" port is to make it easier to add the port into the design. I don't even have to add the port volume into the enclosure volume. It's like having a port that sticks out of the enclosure, but building the enclosure so that it doesn't look like it is. All I have to do now is figure out the amount of space the amp and driver takes up, and how much I would have to add to the internal volume. I was thinking 1ft W, 2ft H, and 2.5ft deep and add whatever volume the driver and amp takes up to the depth of the subwoofer.

Was thinking of an enclosure somewhere alone the lines of this:




Reason why I raised my budget and went with a totally different design is because I'm planning on using this in my bedroom after I move into my own house. I'll using it for movies mainly, and the Dayton Reference HF Drivers have a pretty flat SPL response, which is what you want in a sub for movies, correct?

Thanks, Bobby.

"Bobby is and idiot"
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