[ec114]

So these drivers have been sitting around for over a year(!), but as you can just sorta make out from the first pic below, there's now a stack of cut 3/4" Baltic birch panels. Which I would call a bona fide build start. Hence the post. Assuming anyone else likes build threads as much as I do.

The box sim is outlined here. It's gonna be a 26" cube of 1.5" Baltic birch all around, which is nominally 200l, but driver and passives might make it more like 180l. Hopefully a bit more, not less. PR mass of 2500g is John at AE's suggested max, making tuning 15Hz or so. Something of a size/tuning/SPL compromise, several dB down from Ilkka's tested results, probably, but I'll live...

This is one of a future pair, but no room for the other twin yet, so that set of driver/PRs will just have to chill even longer. Power will be via Crown CE4000 fronted by Behringer DEQ and DCX.

Present sub is a 15" Tumult MkI in 100l sealed powered by a Keiga KGND52100 fronted by Behringer DEQ. Hoping this PR'd box will outwoof it some, especially in the lower end. raying:

More pix as build progresses.

 

[Mike P.]

Looking forward to this build!

Present sub is a 15" Tumult MkI in 100l sealed powered by a Keiga KGND52100 fronted by Behringer DEQ. Hoping this PR'd box will outwoof it some, especially in the lower end.

I don't think that will be a problem.

 

[tcarcio]

Good luck, Keep us informed........:yes:

 

[Owen Bartley]

I love to follow the threads with the big woofers I can't fit into my system yet. I will definitely be tuning in to this thread.

 

[Ricci]

Hey...where'd you get a black frame? :foottap:

 

[Nat Ward]

I too will be following this. Did you ever try the Tumult with the PRs? I haven't started cutting yet, but will be building a ~200L PR box with a Mk1 Tumult and 2 2500g AE PRs. I ran it in a smaller ~125L PR'd enclosure and was pretty happy, now that I've got a house and a larger room I decided to go bigger.

Any issues with the Tumult, or just looking to upgrade?

 

[ec114]

Hey...where'd you get a black frame? :foottap:

Heh. Original owner supposedly had TC make them special to match the cone. He then mounted them innards-out.

 

[Owen Bartley]

Heh. Original owner supposedly had TC make them special to match the cone. He then mounted them innards-out.

Well La-dee-daa, Mr. Custom LMS! Thanks for sharing with us common folk.

 

[ec114]

I too will be following this. Did you ever try the Tumult with the PRs? I haven't started cutting yet, but will be building a ~200L PR box with a Mk1 Tumult and 2 2500g AE PRs. I ran it in a smaller ~125L PR'd enclosure and was pretty happy, now that I've got a house and a larger room I decided to go bigger.

Any issues with the Tumult, or just looking to upgrade?

Nope, never tried PRs with the Tumult. Too small of a box to bother: if building another box, why not new driver as well? So said cold, hard logic. :innocent: And then in case one new driver wasn't gonna be enough, I'd need a pair. And then there's my presently-subless buddy who'd love the Tumult...

Wouldn't say I ever had any issues with the Tumult per se, but since I've always had it set up in an open floorplan, it's never been quite enough. Optimal setting always seems to be a bit much at low levels, then MIA during the loud, low stuff. Never tried any other amp, though, so not sure how hard it's actually getting driven by the Keiga plate. Which, by the way, I modded to move boost to a lower frequency.

Update: Oops. How could I forget? Looking at Ilkka's test data on a MkI, 6% THD at 80dBSPL at 20Hz is really not inspiring. Not that I can claim I ever heard said distortion as such. But all I know is once I heard my first LMS demo, I knew they were literally orders (ok, at least one) of magnitude better...

 

[ec114]

Well La-dee-daa, Mr. Custom LMS! Thanks for sharing with us common folk.

Am I supposed to dignify that with a reply? :bigsmile:

BTW, no progress last couple days due to epic battle (not really) with a low-level cold of some sort. Can't let the bugs win, so holding off on sawdust production... :teeth:

 

[ec114]

Some minor progress today. Thought I'd show my router-based circle-cutting method.

Cut circle to within 1/16-1/32 from backside, with scrap underneath, just in case:

Cut out from backside:

Caster in recess:

'Cuz that's how this sub rolls! :rofl2:

On a less happy note, turns out the panels are a bit less than square. :gah: Kinduva problem when the plan is for miter joints all around. Loads of fun coming right up... :hissyfit:

 

[digital desire]

Are you going to attach the roller plate to the sub? Or just a cart to roll it around on?

 

[ec114]

Ok, so some time might have elapsed since the last post. Lost some momentum due to life and nonsquare boards. But back with a greatly simplified build. Single-layer Baltic birch, and butt joints with glue/screw blocks rather than the original double-layer mitered deal. And only 25.5" on a side. :huh:

Nevertheless, progress has been made. Driver and one PR just sitting there to verify clearance.

Edges have just been roughly trimmed flush, and will be chamfered once the big bit arrives.

 

[ec114]

Are you going to attach the roller plate to the sub? Or just a cart to roll it around on?

That was originally the bottom of the box, but now the holes are too close to the edge. New plan is to cut out the holes, and use them as cutting templates/recesses in the box, if that makes any sense. So each caster will be recessed by two layers. There will of course be a third layer to hold the caster in place.

 

[Owen Bartley]

Hmmm, do you have room to fit any bracing in that box, or do you think the panels are small enough that you'll be OK? Maybe instead of the usual windowpane style ones you could slide a couple of dowel cross pieces in, just to help damp the walls from flexing a little bit? This is a pretty powerful driver, after all!

 

[ec114]

Hmmm, do you have room to fit any bracing in that box, or do you think the panels are small enough that you'll be OK? Maybe instead of the usual windowpane style ones you could slide a couple of dowel cross pieces in, just to help damp the walls from flexing a little bit? This is a pretty powerful driver, after all!

What I've done and yet to document was to attach my driver cutout scraps, ~16in circles, to the top, back, and bottom. At this size BB ply, the intrinsic panel resonant frequency is extremely high, at least in the context of bass notes. Once I added the circles, the frequency got a bit lower, but the amplitude went down a bunch in return. I really think it woulda been fine either way, but I had the circles lying around.

New reason for self-kicking: the big chamfer bit arrived, and I went hog wild cutting down most of the edges. Problem is, chamfer bits, unlike their roundover cousins, are completely UNUSABLE for three-way corners. Worst part is, I actually knew this factoid once upon a time, due to careful premeditation on a previous project, but totally forgot this time around. So there's a an ugly corner. Still wondering what to do about it... :hissyfit: Doubleplusunpleased...

 

[Mike P.]

Post a pic of the corner, it will help in finding a solution.

 

[ec114]

Post a pic of the corner, it will help in finding a solution.

While I'm at it, should I go ahead and give myself some paper cuts and pour salt and lemon juice on them? :teeth: Alright...I know how to fix it, just unsure if I wanna go through the hassle, but I can post it as a cautionary tale...

 

[Mike P.]

Sandpaper is your friend! :yes:

 

[Owen Bartley]

Sounds like the scrap circles will do the job nicely. And don't worry about the corner! I'm pretty sure that everyone's DIY projects have that one little mistake somewhere (at least mine always do), but that just makes it a little more personal. Although I would also like to see a pic to satisfy my morbid curiosity.