Low-cost DIY practice/coffeehouse tweeterless 110 [long]

[DukeLeJeune]

I know this isn't a high x-max driver, but is there enough room b/t the surround and the grill? I can't tell from the pics.

Speaking of the driver loosening up: Would this woofer benefit from some free-air break-in before installation? It's Fs is 46Hz, so maybe a 55 or 60Hz tone run at moderate volume for an hour or so? Thoughts?

I don't think the driver has enough excursion to reach the grill. I use a woofer with over twice as much excursion and a similar grill, and have gotten no reports of grill-smacking.

Free-air sinewave would be good for break-in, or in-box a sine wave well below the tuning frequency (like 20 Hz or so).

 

[mikeddd]

I'm confused, Duke. Playing a woofer in a ported box below the tuning frequency unloads the woofer from the cab. Wouldn't that launch the voice coil across the room?

 

[MX21]

MX21: Looks great! The grill appears to fit just fine; looks like I was incorrect. I know this isn't a high x-max driver, but is there enough room b/t the surround and the grill? I can't tell from the pics. Wouldn't want the surround slapping into the grill at high volumes; that would be bad...

The grill clears it just fine

 

[MX21]

Removed the stock terminal plate, marked for dual speakon plate.

A silver paint pen is useful for marking rat fur.

 

[MX21]

Hole cut. Be sure to have a good vacuum handy. It's hard to get sawdust out of the fur.

 

[MX21]

Also cut some 1/2" birch ply leftover from my fEarful builds. They will be glued inside to give more material to screw into for the handle and speaker mounting.

 

[MX21]

Dual speakon fit in place.

 

[billoetjen]

Hi Duke,

Another great, and practical thread. Thank you so much.
Just a question. Maybe I missed it, but I saw no mention of batting or other damping material. Why the omission?

 

[Turock]

Hi Duke,

Another great, and practical thread. Thank you so much.
Just a question. Maybe I missed it, but I saw no mention of batting or other damping material. Why the omission?

Yeah,you missed it. First post.

But before you install the speaker, I suggest lining the inside of the cab with some 1" open-cell foam. 75% coverage is good. I think Jo Ann Fabric sells open-cell foam cut to the length you specify, and you won't need much. An 18" by 24" piece should be plenty, and you can get the cheapest the sell. Just make sure you haaaaah your breath through it; if not, it's closed-cell foam. Glue or staple in place, your choice, and keep it an inche or two away from the inner opening of the port.

 

[mikeddd]

@MX21: Very nicely done. I don't have any scrap wood to use as backing for the handles, so I'm going to use t-nuts on them. How did you cut the hole for the Speakon plate? Jigsaw? I'm planning on using a router with a 1/4" straight bit. Weird yeah, but I've got to use what I've at hand. Are you planning on lining the cab? With what? I'd appreciate a pic of that if possible.

 

[MX21]

Jigsaw for the cutout, quilt batting for lining the interior. My daughter does quilting so there's plenty of pieces around.

 

[MX21]

Gluing in backing pieces for handle and speaker.

 

[Turock]

I'm gonna cut my batting out of a 1" mattress topper... $10 at Target.

 

[MX21]

By the way, even drilling holes tends to chip out pieces of the MDF, so plywood backing is recommended for any load bearing fasteners.

 

[Turock]

By the way, even drilling holes tends to chip out pieces of the MDF, so plywood backing is recommended for any load bearing fasteners.

That's good to know. Looks like you're doing a good job with yours.

 

[DukeLeJeune]

I'm confused, Duke. Playing a woofer in a ported box below the tuning frequency unloads the woofer from the cab. Wouldn't that launch the voice coil across the room?

This would be just for break-in, to loosen up the suspension a bit. You'd only want to see about a 1/4" of cone movement, so it wouldn't be at high power.

In order to get significant cone movement with the woofer in the box up closer to the tuning frequency, you'd have to put in a lot higher wattage.

By the way, even drilling holes tends to chip out pieces of the MDF, so plywood backing is recommended for any load bearing fasteners.

Thanks for the tip!

I use a fairly cheap variable-speed drill, one that the speed goes up as you pull the trigger back farther. When I'm drilling a through-and-through hole, I use a fairly slow speed most of the way, using enough pressure to get the bit to bite into the wood. Then when the bit is about to break on through to the other side, I ease up on the pressure and speed up the drill so that it's taking smaller bites. This usually minimizes chipout on the other side if the bit is sharp.

The reason not to use high speed all the way through is, that heats up the tip of the drill bit. And it is primarily heat, rather than abrasion, that dulls the bit. Or so says my woodworker.

Break on through, break on through, break on through to the other side...

 

[MX21]

Dual-speakon jack installed. Wired in parallel, 1+ and 1-.
You can also see the screws for the handle going through the backing plywood.

 

[MX21]

Speaker and grill installed. You can see the strap handle here too.

 

[MX21]

With the GK MB200 hooked up. The feet on the MB200 are tall enough to clear the handle.

 

[MX21]

and ready for action. Sounds pretty darn good with the MB200. Still a little weak on the low B string. Maybe still needs some break-in. Also, my little office where I'm assembling this is very bad for testing low sound. I'll get a better feel Thursday when I try at rehearsal.

Note: no batting installed yet. I'm out of spray-on adhesive. I'll have to add that later.

Edit: cheapo bathroom scale says 23.4 pounds. Take that with a grain of salt since this scale doesn't work very well at lower weights.