1st speaker project - was: New Idea For a Small Business, at age 15! (Moved) (1 Viewer)

[Robert_J]

Let me quote my 7 year old niece - "stoopid". Build the D8 as shown. On your second, third or fourth set of speakers, then start experimenting with existing designs or try your luck at your own.

-Robert

 

[bobbyg2]

I just wanted to know what y'all would think. My head was wandering off and that's what I happened to be thinking about atm. Now, I have the fronts all planned out.

The center is the one mentioned above. Now, for the surrounds. Should I just build the same speakers as the center? That seems like the better choice. Unless getting one 8" driver is better. And for the subwoofer, to keep down the consequences for error, here's what I'll do:

Driver: DAYTON DCS380-4 CLASSIC 15" SUBWOOFER 4 OHM (maybe a smaller size for my first?)

Amp: DAYTON SA240 240W SUBWOOFER AMPLIFIER(It has a xover [40hz-180hz] so I'll just set it at 180)

Enclosure (depending on if I want to build it myself or not): DAYTON SWC15 15" SUBWOOFER CABINET

Acc:
ACOUSTA-STUF POLYFILL 1 LB. BAG
DAYTON DSS4-BC BLACK CHROME SPEAKER SPIKES 4 PC SET
PORT TUBE 6" x 6"
36" SPEAKER SEALING CAULK

Anything I miss?

 

[Robert_J]

ACOUSTA-STUF - Wal-Mart polyfil works almost as good and costs around $1/pound.

BLACK CHROME SPEAKER SPIKES - Nice way to dress up an enclosure but the 1" rubber feet will work as well in all but the thickest carptes.

SPEAKER SEALING CAULK - if this is the same stuff PE used to send out with their subs, DON'T USE IT. It's a black, sticky mess. I use closed cell foam weatherstripping available at your local hardware store.

PORT TUBE 6" x 6" - Why? Are you going to port a 2.5cf box? With that port, it would be tuned to 54hz. Here's the math:
Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)
where,
Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of each port (cm)
Np = number of ports
k = end correction (normally 0.732)
At least read up on the different sub alignments at http://www.diysubwoofers.org.

The PE 240w amp and 15" Quattro are a proven combination. I've seen both sealed and ported designs. Just search the PE Tech Talk Board for details of them. Your proposed design would have killed that sub even at moderate listening levels. That is if you could have turned it up that high. It would have sounded horrible tuned to 54hz.

-Robert

 

[bobbyg2]

Ohh, alright then. But which works better?

Here's what I came up with in the math:
Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)
Lv = (23562.5*Dv^2*1/(20^2*Vb))-(k*Dv)

And that's how far I can get. I don't know the Dv, Vb, Lv, and k.

 

[Robert_J]

You have all of these except they are in English and not metric measurements. 1 inch = 2.54 cm, 1 cubic foot = 28.3 liters

Or you can use the port calculator at PSP Inc..

And I missed that you had picked the Classic 15". That's a woofer, not a sub. There's a huge difference in what they were designed to do. If you want to make a copy of Fisher speakers I had in the 7th grade, then it will work. If you want a real sub, the Quattro is the minimum you should look at.

-Robert

 

[bobbyg2]

The MINIMUM? That's the best sub on parts-express...

*EDIT*
Oops, I thought you were talking about the titanic! Haha!

 

[Robert_J]

Look at the xmax parameter of the 15" classic. It's 8.5mm. Also, if you go to the Dayton Loudspeaker section of PE, it's listed along with the other classics like the 5.25" that I'm using for my Dayton Home Theater, the 6.5" that I used in the DII and DIII and the 8" that you are using in the D8. The marketing department labeled it on the site. In my opinion, the Quattro barely qualifies as a sub.

When calculating the ports that you will use, you have to not only pay attention to the length (fitting it in the box), you have to pay attention to the air speed. If your port is too small, you will get "chuffing". Use the formulas here to find the sweet spot between size and air speed. Or you can download WinISD Pro and it will calculate the air speed along with box size, etc. for you.

-Robert

 

[bobbyg2]

Alright, I'll get the dimensions and everything from WinISD and put them here... Once I find WinISD...

 

[JeremyErwin]

look here

 

[bobbyg2]

It doesn't give me enough parameters.

I'm missing:
fLe, kLe, Hc, Hg, and Xlim.
Is there any way to get those?

 

[Robert_J]

You don't need them all and there's a particular order to enter them. If the Help files don't help, here are some links:
http://www.the12volt.com/installbay/...TID=74558&PN=1
http://www.subwoofer-builder.com/WinISD.htm
http://www.hometheatershack.com/foru...ating-sub.html

-Robert

 

[bobbyg2]

Thanks very much. Here's what I got:








Is there anything that I should change? Did I make a stupid mistake? (seeing that it's suggesting a 7+cu.ft. enclosure, I think I may have messed up a bit)

 

[Robert_J]

On the Signal tab, the System Input Power should be the amp's max power. In your case, that would be 240.

If I'm not mistaken, the standard design is about 4cf, tuned to around 22hz. Play around with the box size and tuning frequency.

Finally, don't just look at the transfer function graph. Look at the SPL and the excursion graphs as well.

-Robert

 

[bobbyg2]

Alright, thanks:




Now, should the series resistance be 4ohms?




Why does the SPL go on for ever and the Excursion doesn't have any slope in the line?

 

[Robert_J]

Yes, Z should be 4 ohms. That's the nominal resistance while Re is the DC current resistance.

SPL goes on forever because you haven't added a low pass filter into the equation. That's an estimate of how much output the sub would have if it were run full range. Just ignor anything above 120hz. That's the max you would ever run any sub.

Your cone excursion is for a PR (passive radiator). You aren't building one of those. You are building a ported box. There should be another excursion graph to choose.

-Robert

 

[bobbyg2]

Alright, thanks! Here's the other excursion with 4 ohms series resistance:




Wow, that's a huge difference in SPL just by switching the series resistance from 0.100 ohms to 4.000 ohms.

Oops, I didn't realize the PR. I knew what a PR was and if I noticed it would have questioned which one I chose. I would then have went back into the list and saw there was two excursions.

Thanks Rob, and all of the other people that have put in there input on this. You will always be in my debt. I am looking forward to showing you all what I have built, and hopefully one day be building your speakers!

 

[Robert_J]

The series resistance field on the Signal tab is the resistance of the speaker wire. It should be .1 or whatever it was set to originally. Re is the DC resistance of your speaker. Z is the nominal impedance of your speaker.

Your excursion graph still isn't looking right. Go back to the parameters screen and enter the Sd of the driver. Along with Pe (RMS power).

I just got in a PE sale catalog. Look at their DVC series. The 12" model is $88 while the 15" is $99. The 12" will beat a quatro. The 15" will stomp it in the dirt.

-Robert

 

[bobbyg2]

Alright, back to the drawing boards.

Ohh ya...

DAYTON DVC385-88 15" DVC SERIES SUBWOOFER - $127.50

*EDIT*
Here's what I got for the DVC one:


It gave me A LOT more parameters. I think I got it pretty accurate. Did you get close to the same thing?

 

[bobbyg2]

And I just thought about the size of this thing, it's gona be absolutely COLOSSAL in my bedroom. 4cu.ft. is 2fthx2ftwx2ftd. I'm looking for something around 1.5fthx1.5ftwx1.5ftd. That'd be 3cu.ft.. Now, seeing that this is 15", that'd be a pretty tight fit, unless it wasn't deep.

So, I looked around the room, and decided on the following dimentions:

20" WIDE x 20" HIGH x 11" DEEP. That'd be 3cu.ft (I believe, please check my math) and it would fit nicely into my bedroom theater.

Thanks for you help so far! If you feel this isn't headed in the right direction (15" too big, which I would like to see a smaller driver with same or better parameters) please let me know![url=https://static.hometheaterforum.com/imgrepo/f/f1/htf_imgcache_7025.gif] [/url]

 

[Patrick Sun]

2'x2'x2' would be 8 cubit feet.

2'x2'x1' would be 4 cubit feet.

1.5'x1.5'1.5' would be 3.375 cubit feet.

20"x20"x11" would be 2.5463 cubit feet.