first diy - dayton reference + rythmik audio
 

I am completing my first diy speaker project, and was wondering if this community would be kind enough to comment.

I wanted to make two subwoofers to use as speaker stands, and maybe build an M-T(-M) two way.

At the suggestion of Kyle at Acoustic Visions, I selected the Dayton HF 12 driver, and the Rythmic Audio 350 plate amp. My criteria was the best sounding driver for a sealed unit, playing music at reasonable loudness. He also recommended a 2 cubic feet enclosure.

I built a box out of MDF. The inner dimensions are 12x15x21 inches, all the walls are 1.5" MDF sandwich. I constructed it sort of like linkwitz's thor design with wood bars in the corners to screw into. I don't have any bracing, I hope the box doesn't resonate too much.

I still haven't yet attached the amplifier side of the box, I don't yet have the amplifiers, but I layed the box down with the carpet floor as the fourth wall, and played some test tones. It sounds bassy and can get sort of loud, but I probably need to wait to make judgements until I get the last wall up. I wanted to ask some questions before I build another one:

How do you get wood cut straight from a supplier? Do cabinet makers usually cut wood for reasonable charges? I think the lowes could have cut the panels a lot better than they did.

How important is the rule about lengths of the box not being multiples of eachother?

Do you think I should add bracing, I don't want to make the boxes any heavier, should I have gone single layer, and used bracing instead?

How did you all go about making the circular cutout for the driver in the MDF? I got a cheap jig-saw, which works, but has a tendency to not cut straight down.

How did you drill the bolt pattern, and is there any good technique to make holes straight without a drill press? All my holes are sort of sideways.

How is the driver best mounted to the MDF? I decided to get some T-Nuts from partsexpress, I'm worried that screws in the MDF won't hold at all.

When I played loud low (25hz) test tones, it started to have a mechanical sounding chuffing noise, but it wasn't a painful noise. Is this due to the driver bottoming out, or the fact that the back of my subwoofer was the carpet floor? How do you tell if something is bottoming out?

I live in a place without a garage or basement, and have limited tools which has made this tricky.

There are several places that will cut the panels for you but it depends on what "reasonable" is to you (since it's different for everybody). Since MDF is heavy shipping typically adds quite a bit to the total so I'd recommend finding somebody local if you can.

It isnt with subs because of the size of the sound waves.

Bracing always helps and is a better solution than extra thick walls if the bracing will fit in the enclosure. Sometimes the enclosure is small enough that bracing just wont fit with the amp and driver.

As long as the driver fits in your hole and doesnt have leaks then your jigsaw cut is fine. For a "prettier" and more accurate circle most people use a router with a circle jig.

T-Nuts are fine. Actually, wood screws work just fine too and will hold well. The drawback about using wood screws is if you need to remove the driver several times then your screw holes have a good chance of stripping out.

You are essentially playing sine waves to the driver freeair since you dont have the back wall on. Be VERY, VERY careful doing that because it doesnt take a lot of power to overdrive the driver freeair. Until you get your rear wall on and everything sealed up I wouldnt do any testing because it will be a completely different sub once its completed. That is also why the sub isnt all that loud currently as well.

Thanks for the help, I hope I didn't damage the subwoofer. Definitely been doing a lot of stupid stuff, I think I may end up with a total of one subwoofer out of two boxes worth of parts.

Thanks for assisting my education.