Dual AE AV15-X sealed subwoofers DIY Build

[Russell.Williams]

I thought I would start my own build thread, although there will be obvious similarities with at least two other adventurous (fool hardy?) builders on here....

The plan is to build a 75L sealed subwoofer around an Acoustic Elegance AE15-X driver, that will take the place of an Ikea Lack occasional coffee table and look much the same as if it had a box built under it. The main difference will be rounded edges, a real oak veneer and solid oak legs will be used. The end result (veneer colours excepted) should look much like this:

and here's another view:

For those sad enough, here's the full Google Sketchup to spin to your hearts content. For those even sadder, here's proof it can be cut from one sheet of 25mm MDF.

The whole shebang will be powered from a Behringher EP4000 PA amplifier which will deliver about 1200w into 4Ohms. The originally planned EP2500 would (according to WinISD) result in the driver reaching Xmax at 800w@10Hz. Xmech is higher still but with 1200w on tap, I will still have to keep an eye on bottoming the drivers, but based on 800w this should result in 103dB(SPL) at 20Hz, before you factor in 6-12dB of room gain. Factor in the additional 3-6dB of running two subs, destruction should only happen if I'm actually trying to kill them.

I may yet downsize to a 65L box to give a bit more driver protection, with the added bonus that effective box size and system Q can then be adjusted by adding fibre fill - a trick that does not work in reverse with too large a box to start with.

Just for a comparison against the predicted figures for a single AE AV15-X, the forum favourite SVS PB-13U when run in sealed mode is 'only' producing 99dB @ 20Hz and doesn't produce similar SPLs unless running the 15Hz tune, below which it rolls off twice as steeply as the proposed sealed box.

The Behringer has been bought at £244. The six drivers (two each) got us a quantity discount and resulted in much cheaper shipping, so each driver weighs in at about £181 each which is frankly, staggering. The Govenment will of course ruin this pleasant surprise with import tax and VAT, but even still, this is good stuff.

Any thoughts or input welcome, especially from anyone into DIY subs, speakers or furniture.

Russell

[micb3rd]

I am looking forward to hearing this !

[gperkins1973]

Russel

Is that all the PB13 produced. Very surprised at that especially as mine will be chucking out 120db without room gain.

Good luck with your build. That 2D drawing showing the cuts, is that an add on in sketchup cos I couldn't get mine to do that.

cheers graham

[AngelEyes]

As you know and true to form I still haven't decided which route to take.

My room is a pain so 2 subs should give me more options. I suspect I will build 3 cabinets and see which works best. One set like yours, probably at the smaller end of the scale and a single larger (130L) one similar to below, although I will probably be finishing in Walnut to match my speakers.

I am interested in how you will be joining the corners/legs? I am considering a few options but I think I will try cutting a rectangular section from each leg that the 'box' will sit in. This will involve some chiselling to finish off but it should fairly straightforward using a bench saw to do the main cuts.

The reason I am favouring this approach is that if my 65L test box doesn't work then I can use the legs on the bigger box as they won't be integral to the construction. That is the idea anyway, I am pretty new to this stuff.

Adam

[Russell.Williams]

That's exactly what I was thinking for the legs. It would also neatly side-step rough joins in the veneers, or rough cuts on the upright corners.

As a result of chatting on the Acoustic Elegance board, I'd also changed my mind to go with front firing for two reasons:

1. Driver sag - Big drivers don't much like hanging on the suspension as it reduces travel in the downward direction and eventually results in needing the suspension replaced. AE are certain this won't be an issue with their drivers, but why tempt fate?

2. If the driver is on a vertical face then, given the 55x55x45cm (WxDxH) dimensions of the sub the driver can effectively be moved from against the wall to 55cm from it and 55cm up or down the room, simply by turning the sub on the spot.

To do this I would make the legs stand out an extra 30mm on the driver face, and insert a grill fixed with magnets hidden behind the veneer.

Russell

[Russell.Williams]

Originally Posted by micb3rd

I am looking forward to hearing this !

So am I.

Mic, can you post that link to that glue you mentioned. IIRC this was a glue that rather than expanding to fill gaps, it gripped and contracted to pull surfaces closer together.

Russell

[Moonfly]

Looking good guys. Ive been pondering starting my own thread, but Ive no camera at present, couldnt be bothered to invest much time on google sketch up so Ive nothing really to put in such a thread a present.

One thing which may interest you though Russell, Ive decided to build 2 cabinets so I can test 2 designs to hopefully find which is the best of the 2. Murphy's law will probably dictate both have pro's and con's, and I'll end up being forced between the 2 though

@ Angel, out of interest how did you come about the 65 litres per driver figure. Its a touch smaller than Russ and I were looking into, so are you perhaps thinking of using more wadding? I ask because I was only intending on using it to re-coup a bit of lost performance due to lost volume due to driver and brace displacement, bu it loks as if you may be taking that one a step further, I dont know?

I have also been pondering if I should pad out the inside of the cabinet with foam to improve things a little, but remain undecided. Thoughts?

[AngelEyes]

I think winISD suggested my twin driver enclosure be 134 litres and as I am keen to keep things as small as possible the use of wadding seems ideal. What concerned me a little is when I ran simulations of EQ to boost the bottom end a little it had a dramatic effect on how easy it is to exeed the driver excursion, so I thought a slightly smaller box might protect the drivers more.

When you introduce EQ it really becomes a balancing act with Group Delay, -3dB point and Cone Excursion. I still have a lot to learn in this area so won't be making any snap decisions.

There are so many parameters, I will probably opt for a 'safe' design and then tweak in-room with wadding and EQ if necessary.

Adam

EDIT: The interesting thing about EQ is the effect it has on the group delay. For instance although it dramatically raises the GD at the frequency you add the boost it reduces is at lower frequencies. Maybe this is a bit of a reach but it may be possible an EQ of say +4dB at 25hz reduces the group delay in the more musical end of the spectrum? It also improves the -3dB point by 10 hz. As I said, loads to think about...

[Moonfly]

I see where you going, and I guess if your trying to keep size down then thats the route you'll be forced down.

Ive been trying to keep things as simple as possible (despite a push pull design), so have accepted a larger box to try keep this simplicity. Ive basically pushed the box to its limit size wise to get max performance but keep within xmax. I did notice a few things, like how much you can actually reduce box size and power without dramatic performance reduction.

Be interesting to see if your smaller box is just as good as my larger one, or perhaps better, it'll show the value of putting in a little extra effort with some in built eq.

[micb3rd]

Originally Posted by Russell.Williams

So am I.

Mic, can you post that link to that glue you mentioned. IIRC this was a glue that rather than expanding to fill gaps, it gripped and contracted to pull surfaces closer together.

Russell

This is what I use.

Polyurethane Glue

Bear in mind it has a 1 year shelf life so does not last forever.

[Russell.Williams]

Thanks Mic. Moonfly has sent Adam and I a skeleton gun cartridge of an adhesive he uses at works and that's Polyurethane too, so we're all working along similar lines.

I still seem to remember someone send me a link to an MDF adhesive that penetrated the hard MDF surface and then pulled the surfaces together to create an air tight seal, rather than expand to fill the gap. Mmm....I shall have to Google to make sure I didn't dream it.

Russell

[gregmcquaid]

Originally Posted by Russell.Williams

Thanks Mic. Moonfly has sent Adam and I a skeleton gun cartridge of an adhesive he uses at works and that's Polyurethane too, so we're all working along similar lines.

I still seem to remember someone send me a link to an MDF adhesive that penetrated the hard MDF surface and then pulled the surfaces together to create an air tight seal, rather than expand to fill the gap. Mmm....I shall have to Google to make sure I didn't dream it.

Russell

Gripfill by any chance?

Gripfill 350ml - Screwfix.com, Where the Trade Buys

Regards,
Greg

[gperkins1973]

That's what I got in the end. Gripfill.

cheers

Graham

[AngelEyes]

It was saBesto 'Bond+Seal'

Adam

[gujuboy]

Keeping myself updated on this thread...