Dual GR SW-12-08 + Rythmik A370PEQ Servo Sub (sealed) - AVS Forum
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post #1 of 38 Old 01-29-2009, 11:49 AM - Thread Starter
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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.
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post #2 of 38 Old 01-29-2009, 11:55 AM
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thats kind of a small room; what's your reasoning for going dual in one box? You certainly won't need the output, and you won't get the benefit of multiple placement to tame room modes...
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post #3 of 38 Old 01-29-2009, 12:33 PM - Thread Starter
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Quote:
Originally Posted by zero the hero View Post

thats kind of a small room; what's your reasoning for going dual in one box? You certainly won't need the output, and you won't get the benefit of multiple placement to tame room modes...

  • 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
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post #4 of 38 Old 01-29-2009, 01:03 PM
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Quote:
Originally Posted by Stereodude View Post

  • 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

You know you can do two drivers in two boxes and only use one amp.

YID DIY
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post #5 of 38 Old 01-29-2009, 01:10 PM - Thread Starter
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Originally Posted by Looneybomber View Post

You know you can do two drivers in two boxes and only use one amp.

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
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post #6 of 38 Old 01-29-2009, 07:01 PM
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I just did a Rythmik DS1500 kit in a sealed sono tube. Maybe you could do a couple of 14-16" sealed sonos. I know Brain gives a max cable length of 12' between a single sub and servo amp, how is the dual wired?

They also offer an OB version, which would also take up less space, but I don't know how that would do in a small room.
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post #7 of 38 Old 01-29-2009, 07:15 PM - Thread Starter
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Quote:
Originally Posted by jkhome View Post

how is the dual wired?

Voice coils in parallel. Sense coils in series.
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post #8 of 38 Old 01-30-2009, 05:00 AM
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Quote:
Originally Posted by Stereodude View Post

Voice coils in parallel. Sense coils in series.

So the sensing run may end up too long? If it were I, I would build two enclosures, and stack them, maybe put the amp in a separate enclosure (check out the OB amp thread in the GR forum at AC).
I'm assuming you could add a second amp later?

I'm sort of doing that, building two cubes for some 12" Rythmik LT drivers, that will be driven by a couple of pro amps. But I designed the cabinets so I could upgrade/add servo drivers and amps later if so desired.
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post #9 of 38 Old 01-30-2009, 07:14 PM - Thread Starter
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Quote:
Originally Posted by jkhome View Post

So the sensing run may end up too long?

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.
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post #10 of 38 Old 04-25-2009, 03:43 PM - Thread Starter
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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.

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post #11 of 38 Old 04-25-2009, 08:38 PM
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That's an excellent build. Looks good--now peel the film off!

How'd the laminate application go?

I do like that Rythmik servo sound. Let us know some further impressions once you spend some time.
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post #12 of 38 Old 04-26-2009, 05:16 AM - Thread Starter
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Quote:
Originally Posted by Fatawan View Post

That's an excellent build. Looks good--now peel the film off!

That's crazy talk! I must protect the finish!
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How'd the laminate application go?

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.
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post #13 of 38 Old 04-26-2009, 05:23 AM
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That must sound fantastic, do you have anything to compare it too. I have heard these are a little tigher and faster than some other designs. Is there some sort of design advantive buy installing the drivers opposite one another (push-pull) or something? Looks great!
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post #14 of 38 Old 04-26-2009, 07:52 AM
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is this laminate like a veneer? How thick is it? Does it come in sheets, or rolls?
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post #15 of 38 Old 04-26-2009, 09:58 AM - Thread Starter
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Quote:
Originally Posted by nick53 View Post

That must sound fantastic, do you have anything to compare it too. I have heard these are a little tigher and faster than some other designs. Is there some sort of design advantive buy installing the drivers opposite one another (push-pull) or something? Looks great!

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.
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post #16 of 38 Old 04-26-2009, 10:04 AM - Thread Starter
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Quote:
Originally Posted by random username View Post

is this laminate like a veneer? How thick is it? Does it come in sheets, or rolls?

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'
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post #17 of 38 Old 04-26-2009, 10:34 AM
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did I understand correctly that you used a flush trim bit on a router (the kind with the bearing on the end) to trim the edges? I"m surprised this didn't scratch. Must be pretty durable stuff.
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post #18 of 38 Old 04-26-2009, 01:00 PM - Thread Starter
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Quote:
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did I understand correctly that you used a flush trim bit on a router (the kind with the bearing on the end) to trim the edges? I"m surprised this didn't scratch. Must be pretty durable stuff.

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.
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post #19 of 38 Old 04-26-2009, 03:41 PM
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Stereodude, how much is the formica cost? Where can I get those?

I would like to see a picture of the protective film off

Thanks.

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"When the opponent expand, I contract,
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And when there is an opportunity,
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post #20 of 38 Old 04-26-2009, 05:28 PM - Thread Starter
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Quote:
Originally Posted by nick53 View Post

Is there some sort of design advantage by installing the drivers opposite one another (push-pull) or something?

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.
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post #21 of 38 Old 04-26-2009, 05:34 PM - Thread Starter
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Quote:
Originally Posted by wackii View Post

Stereodude, how much is the formica cost? Where can I get those?

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.
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I would like to see a picture of the protective film off

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

I need to work up the courage to start peeling.
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post #22 of 38 Old 04-26-2009, 05:41 PM
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Quote:
Originally Posted by Stereodude View Post

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.

I'm not sure I follow this one. Both drivers move either in or out at the same time, right? So if anything, you are pressurizing the enclosure more than you would with one driver...which will try to bend the panels outwards...which is why you would need good bracing.

Maybe you meant building the sub heavy just so it wouldn't move around too much?
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post #23 of 38 Old 04-26-2009, 05:42 PM - Thread Starter
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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.
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post #24 of 38 Old 04-26-2009, 05:45 PM
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Quote:
Originally Posted by random username View Post

I'm not sure I follow this one. Both drivers move either in or out at the same time, right? So if anything, you are pressurizing the enclosure more than you would with one driver...which will try to bend the panels outwards...which is why you would need good bracing.

Maybe you meant building the sub heavy just so it wouldn't move around too much?

The box still needs to be built very strong. By putting the subs on opposing sides the box will not rock at all during operation. The forces from both subs of trying to rock the enclosure back and forth will cancel each other out. This way the enclosure does not need to be anchored to the floor.
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post #25 of 38 Old 04-26-2009, 06:04 PM - Thread Starter
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Quote:
Originally Posted by random username View Post

I'm not sure I follow this one. Both drivers move either in or out at the same time, right? So if anything, you are pressurizing the enclosure more than you would with one driver...which will try to bend the panels outwards...which is why you would need good bracing.

Maybe you meant building the sub heavy just so it wouldn't move around too much?

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.
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post #26 of 38 Old 04-26-2009, 06:10 PM - Thread Starter
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Originally Posted by tsloms View Post

The box still needs to be built very strong.

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.
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post #27 of 38 Old 04-26-2009, 06:25 PM
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I'm making the sand filled version myself, but it's a double stack and not opposing. It will be immovable in ever sense of the word
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post #28 of 38 Old 04-27-2009, 07:13 AM
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Quote:
Originally Posted by Stereodude View Post

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.

Thanks. It looks like an inexpensive way to get gloss black. Now if someone is man up and peel off the protective film then take a few pics of it. Right now your sub is in "cloudy" black and not the "polished" black that you bought

Come on... PEEL IT OFF... PEEL IT OFF....

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When he contracts, I expand,
And when there is an opportunity,
I do not hit--it hits all by itself."
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post #29 of 38 Old 04-27-2009, 07:35 AM
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Quote:
Originally Posted by Stereodude View Post

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.

Sand is hard core, but I want to see someone use lead. Would molten lead burn MDF? Maybe you could melt it down and pour it into the box. If that wouldn't work maybe lead powder mixed into a very dense epoxy and poured in and allowed to cure before sealing. Density ftw!
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post #30 of 38 Old 04-27-2009, 04:39 PM
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lead shot bonded with some type of very thin epoxy resin poored in the wall...not sure if that would really dampen vibration but man would it be solid. Of course concrete would work for just adding mass and would be much cheaper and safer.

Or how about getting ahold of the lower section of a large tree (stump), and just hollowing out an area?
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