My First Ever DIY Sub - Page 5

Unibox doesn't exactly agree with Bass Box Pro 6. 3.33cu-ft box / 25Hz tune

19Hz HPF:


no HPF:


FWIW, a 19Hz HPF just barely keeps driver excursion in check with a 25Hz tune.

What diameter is your port?

You're going to have serious problems if that's really the diameter of the ports you're using. With the 19Hz HPF in play you're looking at >70m/sec air velocities at 24Hz with 500W.

2 4" ports or a single 6" port is about where you want to be IMHO, but they'll be hard to fit in the box. Twin 4" diameter ports need to be ~30" long (each) for a 25Hz tune. A 20Hz tune is even worse with twin 4" diameter ports @ ~48" long . "Small" high output ported boxes that are tuned low is challenging.

Sufficient for holding carpet on, probably. Gluing the box together, no. To glue the box together use wood glue.
I'm possible to say. right now.
I would suggest using flared Precision Ports that are already black.
I would probably recommend caulk / silicon over hot glue.
If you're carpeting the box, it doesn't matter unless they're visible under the carpet.
The spray adhesive might stick better if the outside surface is a little rough, but it might not be necessary. You could test using some scraps of the carpet and wood.
MDF is fine for bracing.
Hard to say since it's not clear what you mean by crossbeam. What are the dimension of your planned box?
Something like Cut, glue, screw, wait, seal, wait, assemble, test, disassemble, carpet, final assembly
For a sub, it doesn't matter.
You should glue in between each piece. The glue is largely what end up holding the box together. The screws largely hold things in place while the glue dries.
After.
bracing isn't to reinforce the joints. It's to reduce panel resonances. The joints don't need bracing the large unsupported open spaces in the middle of the panels do.

Here is a link to my build http://www.avsforum.com/t/1432689/my-epic-12-build

You can mimic the build, easy way to get a long port in the box.

Dan

*Spray adhesive is fine for carpet. Spray the box and the back of the carpet. Let it sit for 3-5 min, then apply the carpet to the box. Overlap seams and trim using a utility knife and straight edge.
*I paint the ports w/ rustolium prof rattle can paint
*Use PL Premium adhesive for the joints and you won't need to seal. It's an expanding glue and very forgiving if your cuts are not perfect.
*Screw holes don't need to be filled if you are using carpet. When I do fill them I use bondo...or pl premium if the tube is already open.
*I don't sand if covering in carpet. I will use a plane to knock down any uneven edges.
*MDF is good for braces. I've never used boards. MDF is more stable. I don't brace corners. Corners are the strongest part of the box anyway.
*One beam across, one vertical, one strip about 2" high as a spine against the back wall of the box since you can't tie it to the baffle. That's a minimum. Every panel should be braced to reduce resonance. Ideally a brace every 8-10".
*Cut panels, rout holes, glue & screw, brace, carpet, line, install driver.

Also, for ported boxes I line the box w/ mattress topper from Wal-Mart. I think the full size bed topper is $10 vs $18 for a bag of poly quilting from the fabric store. Don't use pollyfill pillow stuffing in a ported box.

Sounds like a good plan.

There are 2 types of grill cloth at PE last I checked. One is a 3D weave made with nylon strands. This one needs to be stretched with a good bit of tension across the frame and stapled on the back. I've used this product to restore a guitar cab and it looks good and is durable. However, it does have a classic 60's radio/ Marshall guitar cab look and probably isn't what you want unless durability is your primary concern.

The other, cheaper type is more like a modern home speaker grill. It's a lighter weight, more fabric-like material. Again, staple it on the back of the frame using a little tension to keep the fabric tight. In either case a little glue along the cut edge of the fabric may help keep it from fraying.

Hi Mfrey,

Since your now in the build stage, starting a new thread or having a Mod change title might get more visibility......

Lookin good so far!

Nice! Put a couple pillows in there!

Hey buddy... Been following your thread from the beginning. Banter, lively discussiom and all.

Just wanted to say good job and I think ultimately you will like going sealed in the end.

About your polyfill question. 1lb (bag) per cuft has always been a standard rule of thumb (sorry, I can't find my old reference).

I didn't read any mention that you did some inital freeair testing before installing your driver in your cabinet. Not a huge deal, just a preference of mine.

One thing to keep in mind is that I've heard several TC Sub owners mention that you should potentially gain some output after the suspension lossens up a bit from inital breakin.

Hey, so... Ultimate end goal? Now that you've built, let's re-asess. You good with everything?

you did wire the coils in series, right?

great. that is how it should be set up.

i was reading back through the thread and saw that you asked a question about wiring a 1 ohm load to your amp and that would be a bad idea.

Can either you or someone else please explain the science of port velocity, and how ports affect the sound based on their size and length? I am slowly learning about how to use WinISD but all of this talk about port velocity and optimal port size and shape, I am confused. Could you please explain this?

As air velocities in the ports increase you get boundary layer turbulence (audible chuffing). If you continue to increase the velocities the port past the point of chuffing you will get core turbulence and compression. When that happens the port no long acts like a port and the and the box no long acts like the models predicts.

This page / program gets into things further.

With the sort of giant sonosubs you're looking at building you can use 8" sonotube for the port and keep the air velocities low enough to where you shouldn't have any audible problems.

Wow, that went quick. Looks good for a first timer.