Project Slopzilla (DIY Sub) continued...

[bcycle]

The e-mail that started the "Suggestions for DIY Home Audio Sub" thread. ("Project Slopzilla"......)

Hi All. You might recall that my goal was to not spend more than $200 on parts plus the materials to build the thing. After some research, some e-mails and help from (as they say here in Philly) "yous all", I've made some decisions which I would like to run by this message board for commentary, critique and suggestions.

I am learning much about Sub design including using WinISD to design my subwoofer. I'm not an engineer by any stretch but I have a pretty decent background in the audio realm. (I Sold High end for 8 years about 12 years ago). But I'm no engineer anyway.Your input and/or comments will be of great value.

Decisions thus far:

I'm seriously considering the Dayton 15" Quatro along with Dayton's 240 watt plate amp. (300-804) which totals

WinISD suggests a 6.962 sq. ft. box and I've plugged in 2- 4 x 17.35 inch ports which should yield a bottom end of 20.15hz (-3db). Also according to WinISD, 3 ports at 4.25 inches will produce a vent mach of .02 which is good. (yes?)

I'm going to make a box out of 3/4 inch mdf with hole cutouts for the amp, the woofer and vents. Dimensions I'm considering are just about 30 H x 22" W x 22" D which gives my 6.962 volume. I'm thinking PVC vents, screws with T-nuts and lots of silicone to keep it on the cheap.

I'm using the plate amp it has a hi pass/ x-over feature, phase adjust and it's pretty cheap.

Woofer location: I'm thinking abut locating the woofer in the middle of the box with a port above and below the woofer. Another idea idea was to locate the woofer on the top of my 30 inch tower similar to some of Roy Allison's speaker design theories. (He liked to get the woofers as close to the wall as possible to minimize low frequency wavelength cancellation). So, if I put the Dayton woofer on top, is there any benefit? Comments on woofer placement are welcome.

Finally, what about bracing? Do I need to brace this cabinet after screwing and gluing my pile of MDF? I've seen some braces where they had big holes and the holes were routed with a roundover edge. Should I do this? Should I double the faceplate?

Anything else? Thanks for your input. I'll post pics and results as I move along on this project!

Greg

 

[marrypoppins]

Hey Greg,

I built that same sub, only space was an issue for me so it ended up being 5.4 cubic feet. The thing rocks my house and puts down some seriously clean and powerful sound, im convinced that this is the best option for under $300 dollars, we compared it to my best friends KEF sub yesterday http://www.ultimateelectronics.com/shopping/product/detailmain.jsp?itemID=360&itemType=PRODUCT&iMainCat=1530&iSubCat=1651&iProductID=360&tabID=2 and now he wants one, the Quatro definitly kept up. I think your plan sounds pretty good, however I would go with a little bit of bracing just to make the box more solid. Have fun on your project.

Patrick

 

[MacManNM]

You can achieve very good results by using a sonotube instead of building a box ( i just put 2 layers of 3/4 MDF on the top and bottom, and secure them together with allthread. This method is much less likely to resonate and add color to the sound. Doesn't look great but the audible benefits are great.

 

[bcycle]

Pictures speak louder than words

That post (see below) was way too long. The very primitive (ok crappy) sketches show what I'm thinking of. Are these designs ok? What about the top mount idea? More details in the text under the pictures.

The e-mail that started the "Suggestions for DIY Home Audio Sub" thread. ("Project Slopzilla"......)

Hi All. You might recall that my goal was to not spend more than $200 on parts plus the materials to build the thing. After some research, some e-mails and help from (as they say here in Philly) "yous all", I've made some decisions which I would like to run by this message board for commentary, critique and suggestions.

I am learning much about Sub design including using WinISD to design my subwoofer. I'm not an engineer by any stretch but I have a pretty decent background in the audio realm. (I Sold High end for 8 years about 12 years ago). But I'm no engineer anyway.Your input and/or comments will be of great value.

Decisions thus far:

I'm seriously considering the Dayton 15" Quatro along with Dayton's 240 watt plate amp. (300-804) which totals

WinISD suggests a 6.962 sq. ft. box and I've plugged in 2- 4 x 17.35 inch ports which should yield a bottom end of 20.15hz (-3db). Also according to WinISD, 3 ports at 4.25 inches will produce a vent mach of .02 which is good. (yes?)

I'm going to make a box out of 3/4 inch mdf with hole cutouts for the amp, the woofer and vents. Dimensions I'm considering are just about 30 H x 22" W x 22" D which gives my 6.962 volume. I'm thinking PVC vents, screws with T-nuts and lots of silicone to keep it on the cheap.

I'm using the plate amp it has a hi pass/ x-over feature, phase adjust and it's pretty cheap.

Woofer location: I'm thinking abut locating the woofer in the middle of the box with a port above and below the woofer. Another idea idea was to locate the woofer on the top of my 30 inch tower similar to some of Roy Allison's speaker design theories. (He liked to get the woofers as close to the wall as possible to minimize low frequency wavelength cancellation). So, if I put the Dayton woofer on top, is there any benefit? Comments on woofer placement are welcome.

Finally, what about bracing? Do I need to brace this cabinet after screwing and gluing my pile of MDF? I've seen some braces where they had big holes and the holes were routed with a roundover edge. Should I do this? Should I double the faceplate?

Anything else? Thanks for your input. I'll post pics and results as I move along on this project!

Greg

 

[MacManNM]

The 1st one is the best out of all of them. Do not put the woofer on top. It's too easy for dirt to collect, or damage to occur. Make sure the ports are at least 4" short of the back of the cabinet, they dont look like they will be. You can just put a 90 degree bend at the end. Also make sure that your ports are large enough, the ID of the pipe has to match the code.

 

[bcycle]

sonotube instead of box

Intriguing idea. Now I'm rethinking my box. I'm lousy at the math but to get 6.962 sq. ft (2.33 square yards?) in a Sonotube with that 15" Dayton Quatro driver I think I'm looking at a 6ft x 42 inch tube or a 26" x 16 foot tube!? My math has gotta be wrong. Look at their chart though.

If I went the Sonotube route I may have to rethink the driver...

You can achieve very good results by using a sonotube instead of building a box ( i just put 2 layers of 3/4 MDF on the top and bottom, and secure them together with allthread. This method is much less likely to resonate and add color to the sound. Doesn't look great but the audible benefits are great.

 

[MacManNM]

Intriguing idea. Now I'm rethinking my box. I'm lousy at the math but to get 6.962 sq. ft (2.33 square yards?) in a Sonotube with that 15" Dayton Quatro driver I think I'm looking at a 6ft x 42 inch tube or a 26" x 16 foot tube!? My math has gotta be wrong. Look at their chart though.

If I went the Sonotube route I may have to rethink the driver...

ok, first off you are dealing with cubic feet. You kneed a box with a volume of 7 cuft right? also you are going to have ports in the box, they are going to take up some space, lets say a total volume of .26 cuft, so you now need to build an 7.25 cuft box or so. So an 18" cyl cut 49" tall will give you 7.21 cuft. this should work fine.

 

[annunaki]

Finally, someone mentions displacement. It is especially critical, with ported enclosures, to figure in the displacement of the ports, subwoofer and bracing. One other thing to remember is that a port needs room to breathe on each end. It needs a minimum the diameter width before and solid surface. So, if you ports are 4" they will need to be 4" or more from any surface inside or outside of the enclosure.

 

[MacManNM]

Finally, someone mentions displacement. It is especially critical, with ported enclosures, to figure in the displacement of the ports, subwoofer and bracing. One other thing to remember is that a port needs room to breathe on each end. It needs a minimum the diameter width before and solid surface. So, if you ports are 4" they will need to be 4" or more from any surface inside or outside of the enclosure.

Absolutely. However with a cyl sub, internal bracing is not much of an issue if you build the ends nice and solid. This is why I use allthread to hold the ends together, really makes the unit strong.

 

[bcycle]

Calculating Cylinder Volume

See, I don't know the math to calculate the volume of a cylinder! There is an online calculator at http://www.the12volt.com/caraudio/boxcalcs.asp has some handy dandy calculators that confirm your result. Thanks

ok, first off you are dealing with cubic feet. You kneed a box with a volume of 7 cuft right? also you are going to have ports in the box, they are going to take up some space, lets say a total volume of .26 cuft, so you now need to build an 7.25 cuft box or so. So an 18" cyl cut 49" tall will give you 7.21 cuft. this should work fine.

 

[MacManNM]

To think that I did it by hand, got to love this internet.

 

[jaxvon]

Just for reference, the volume of a cylinder is pi*h*r^2 where h is the height and r is the internal radius (half the diameter).

 

[MacManNM]

Thanks Jax. I believe his trouble was in the conversion from in^3 to ft^3 to yd^3 and back.