Dual GR SW-12-08 + Rythmik A370PEQ Servo Sub (sealed)

I'm seriously considering a build of a Dual GR SW-12-08 sealed servo sub powered by the Rythmik A370PEQ amp. I've built a few subs before (sealed, ported, & PR'd) so I'm not new to the whole DIY thing.

I'm after a solid performer for music with not much emphasis on movies or TV. It will be used in a 2.1 setup with ported floor standing GR Research Neo-2X's in my small office / library (11' x 9.5' x 9). Right now I'm thinking a sub around 3.0cu-ft internally that's about 25" tall, 16 wide, and 17 in deep with the drivers being mounted on the opposing 16"x25" sides with the amp on the side.

Thoughts?

Edit: The build is finished. Pictures are in Post #10.

• Two 8 ohm SW-12's seem to play much nicer with one 370W amp, than one 4ohm SW-12 with the single 370W amp (in terms of excursion vs available power).
• It also looks like I need two drivers to get over 100dB at 20Hz.
• Two drivers in one box with one amp is cheaper than two drivers spread between two boxes with two amps

Yes, I know that, but then you have long wires between the two connecting them. Besides, in an ~11x12' room I don't have a lot of space to place two subwoofers.

Here's an updated picture of the front of the room:


I have not yet turned the X-SLS's into Neo-2X's, and obviously the X-LS's will go away

Voice coils in parallel. Sense coils in series.

It could. Basically, there just isn't room for two subs in the room so I plan to make myself a miniature version of Mark Seaton's Submersive.

On a related note I updated the room dimensions in the first post since I had them wrong.

Well, I finished...

So I started with this idea:



And ended up with this:



I just finished the box yesterday. The protective film over the polished black Formica laminate hasn't been peeled off in the pictures.

I put in the drivers last night and took some pictures of the finished sub this afternoon.



And, no I haven't brought myself to pull of the protective film yet.

And here's some change balancing on the sub as it was pushing 109dB peaks.



At those levels the sub about was the only thing that wasn't vibrating.

The long story short.... It sounds great with my GR Neo-2X's. The Neo-2X's are set to small and crossed over at 80Hz, and they can't keep up if I crank it. I guess I didn't need to go dual, but what fun would that have been?

Here are a few pictures of the Neo-2X's that I retrofit into X-SLS enclosures.

That's crazy talk! I must protect the finish!

I went OK once my Dad and I figured out the tricks. We found out that you need to mask off the edges of the adjacent sizes to keep the contact cement from getting around the corners onto the adjacent sides when you're rolling it on. The first side we didn't do that and the contact cement on the back of the extra laminate that the router was trimming would stick itself really well to the small amount that made itself around the corners. On the second side we learned to pull off the masking tape right after rolling the second coat of contact cement instead of waiting. By the third side we pretty much had a working routine down.

Oh yeah... One roller made it the whole day and a half. I used a ziplock bag and squeezed out the air.

I have a UFW-12 to compare it to. It sounds good, though I'm having a bit of a hard time getting it to really blend into my system. I tried it in place of the UFW-12 in my HT system (RS1000 Sig's) in the Great Room, and then with the Neo-2X's in my Library. In both systems it seems to stick out with music. It's level matched and I used the distance setting that MCACC reported back (which has worked well with with other subs I've used), but it still seems too loud. I tried turning it down some, but also didn't really seem to help.

I'm going to get my measurement system with ETF going today and see if I can figure out what exactly is going on.

The laminate I used is .8mm thick. It's similar in concept to a veneer. It's the same type of stuff that's very often used on kitchen and bathroom counters. Formica doesn't recommend using the polished laminates on surfaces that see wear because it's not as durable as the matte finish you usually see on counter tops.

It's sold in sheets. The polished black is only sold in 4' x 10' sheets. However, it is shipped rolled up in a box about 12" x 12" x 4'

Two things. The first one is that there is a protective film on the laminate. The second is that we had the flush trim bit extend only just enough to cut the laminate to prevent it from rubbing on the rest of the laminate.

Sorry I forgot to answer this one earlier.

The opposing design results in a rock solid cabinet without making a crazy heavy box because all the forces from the two drivers cancel out.

The Formica was about $86 for a 4' x 10' sheet. I bought it from a local cabinet shop that was listed on the Formica website as being a dealer. Home Depot is a Formica dealer, but they can't get the polished Formica. Apparently it's only sold through cabinet shops.

I'd like to see it with the film off too.

I need to work up the courage to start peeling.

Well, I spent some time with ETF today and my room has a huge spike (like 12db+) at 50Hz. I messed with the parametric EQ in my Pioneer Elite for both the main channels and the sub, then messed with the single band parametric EQ on the sub. It blends better now, but the room definitely needs some room treatments. Being that it's also our home office / library I'm not sure how crazy I can go on the treatments.

I also think some of my feeling that it's not blending well is from the vibrations in the floor. Sound travels faster in wood than air, and I swear the vibrations my feet feel are tell my brain the bass is arriving out of sync with the mains.

It's a balanced enclosure because the drivers can't move the box. Sure they can pressurize it, but they can't impart any movement to the enclosure. Any force that's applied from one driver is canceled out by the drive on the opposite side of the box. It's similar to how a boxer 4 cylinder engine is balanced.

And the box is built strong with ample bracing. It doesn't have a bunch of sand in it though and additional layers of MDF to make it completely immovable like this sub though.