"Sump Basin" Subwoofer - MacGyver style - Page 2

I will find a place for the stuff! I just used some expanding foam in it as well!

Here's what's happening right now - foam is setting, should help seal the vents and maybe even dampen the sound a bit, who knows. If this sounds great, I'll be trying the poured cement trick to make this a 'final' design. I still need to sand the end of the tube to try and smooth it a bit. I'm not pushing my luck on this, there's plenty of spare port velocity. I'll be listening within the hour, very psyched to check out 16hz with 8db of extra oomph.

Ok. Holy cr**. Or whatever the usual first response is. Wow.

If nothing else it could (slightly help) break up some standing waves. Probably does nothing. Its main purpose is to act as an adhesive and sealant, for sure. The fact that it becomes rigid when dry and is very lightweight is why I used it.

Listening last night and this morning has been revelatory. I have zero doubt about the LLT concept's effectiveness. My current tuning is set at 17hz - the design allows port extenders to be added for lower tuning. A pair of 24" 'extension' tubes will give me a 12 hz tune, I'll be trying that out tonight after I head back to Home Depot once again. My thinking is to put the tubes in for HT duty, take them out for music listening sessions (unless the music explicitly demands the ability to play that low). I'm psyched. Bass is scary loud, visceral, tight, low, clean. Exactly the sound I was looking for.

The port plug models terribly - at 12 hz vent mach is .57 versus extension tubes mach .14 - at the current 17hz tune it's mach .10

That's going to happen today. I'm using dual 3" tubes as ports. I have my eye on a part that looks cool and should do that job rather well.

So it is: We enter 2013 and the sump basins are going strong. They survived the 'Small NE GTG' - one of my concerns was durability, especially in transport. No issues. It's nice to have heard them side-by-side with several 18" heavy-hitters. Considering the modest power and displacement, I couldn't be more pleased with the price/performance.

They are so good, I have zero inclination to upgrade. Bass is 'perfect' in my modest listening room.

As the spring GTG approaches, I am considering building a couple dipole arrays that I can mount to a pair of sump basins and create full-range speakers. Something really powerful, lightweight and keeping with the MacGyver theme - made with parts bought at Home Depot.

Cool! Yup you got it. My final setup is 4 sump basins, 1 in each corner of the system. Power comes from a Crown XTi-2002. I run pairs on each channel - parallel for a 2 ohm load. EQ has a slope of 6 db/octave. I have not found a need for a HPF, the sub seems to self-limit.

The other things you'll need - somethig to act as leg - I used long screws with rubber caps on the ends but the ideal is probably sofa legs or door stops. You'll also need 3" PVC couplers to terminate the ports, and finally some sort of sealant for the port's exit - I happened to use 'outdoor double-sided tape' to create the seal. I could just as well have used Silicone, epoxy, plumbers tape... just about anything that makes the joint between the pipe and the basin airtight. If you are lucky, you can probably achieve the seal with a careful cut and a tight fit, but I was not able to achieve that.

You'll also need something to use as legs - the ideal is Sofas legs but I'm just using long screws.

^^^ The way I did it, I first attached the coupler to the tube - you could glue it, but it sticks tight if you hammer it on. With the basin's bottom facing up, I inserted the tube until the coupler made contact. At that point I sealed it and sprayed the foam. The point of the foam is to bond the tubes to the side-walls of the basin, and perhaps to diffract some standing waves that would have bounced off the (flat) bottom. What's important is that you not manipulate the tubes once the foam is applied, until it cures. Seal the port before applying foam. Once the foam cures you're good to go. I used one can of 'large gap' good stuff per sump basin sub.

An 18" is a no-go with my design - you get 15.75" ID with the narrower 'bottom' - I'm relying on the flange to connect the two basins. A 15" would work and I intend to try such a build soon. Flipping it probably does give you an 18" opening, not sure about that, I need to go measure one at the store. Definitely curious. The main issue is that there isn't that much air space - 2.5 cubic feet per basin.

A dual-opposed 15" implementation could be a real winner - especially with an economical, lightweight 15" like the Polk MoMo.

That's correct what Lowes carries is totally unsuitable.

I looked at the huge basins as well. That hole on the side, I'm thinking it could be used to install a port. I have to go check those out. Sorry if it seems like a wild goose chase. I found that some Home Depot stores have no clue what they are, and you have to spot them in the upper shelves. My local Home Depot seems to have plenty, always in stock.

Edited by imagic - 2/20/13 at 8:50am