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Discussion Starter · #1 ·
A few months ago I came up with this crazy idea of using subwoofers as a platform to set my tower speakers on behind my screen, bringing them up to ear level. I decided to go the DIY route to accomplish this. After much research, I found that 4 Full Marty's laid on their sides end to end would be the perfect dimensions to accomplish my goal. Having never built a subwoofer before, I decided to go with flat packs from GSG Audio. For the drivers, I chose Eminence NSW 6021-6. For the amps, a pair of Behringer NX6000.

I ordered at a good time for pricing, but at a bad time for getting anything in a timely manner. I knew there would be some delays due to COVID, but was expecting ~3-4 weeks to get everything. A series of unfortunate events occurred, and it ended up taking a little over 2.5 months to get everything.

First the NX6000 amps were out of stock and an ice storm in the southern US was causing major shipping problems. Kevin at GSG called me right away to let me know, and gave me a refund for the amps since he wasn't sure when he'd be able to get them back in stock. I was able to find them on Amazon for the same price and had them in hand a week later.
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Kevin @ GSG let me know when I placed my order that he didn't keep the NSW drivers in stock, and that they would be shipped directly from Eminence. However, Eminence was behind on production due to COVID, so expect some delay. The delay was a few weeks longer than expected, but just a few days short of 2 months after my order was placed, I received the NSWs.

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The MDF/lumber shortage hit like the day after I placed my order. This left GSG without enough MDF to complete my order. This caused the biggest delay out of everything. It took a while for them to find another supplier and obtain the rest of the MDF necessary to fill my order. Kevin was upfront with me throughout the whole process though, excellent customer service for sure.

A couple weeks after receiving the NSWs, I finally received the flat pack shipment. All 931lbs of it! The freight company backed a full semi down my 1/4 mile long gravel driveway. The pallet was about 100lbs over the lift capacity of the fork lifts on my John Deere 1025R compact tractor, but it still managed to unload it from the semi and get it into my garage.

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Unfortunately someone rammed a forklift into one side of the pallet and damaged 3 of the panels. The freight driver stuck around for me to unwrap the pallet and do a quick inspection. He took pictures and noted it on the receipt before leaving.
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I e-mailed GSG and gave Kevin a quick call. They're going to handle the shipping claim and send me replacements for the damaged panels ASAP.

I wasn't able to carry all the pieces down into my basement until the next day. I organized all the panels by number in one room, and laid out all the pieces to build the 1st one in my (functional but still under construction) theater.
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I didn't have time to start building until the weekend, so everything sat like that for a few days.

The top and side panels (1 - 3) were glued first, and then I dry fit the port panels and bracing (4 - 9) while the glue was drying.
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The instructions said to tip it upright and then insert the braces and clamp. It didn't mention gluing for this step, but I figured that was implied by clamping. Why clamp if you hadn't glued? The bracing fit so easily into place with it laying down when I dry fit it, so I decided to glue them in that position first, then tip it upright and clamp. This worked out well.
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I only had a pair of 36" bar clamps, and a pair of 48" bar clamps. Didn't seem like enough, but I got a little creative with clamp placement and made it work. I went out and bought more clamps to use for building the remaining 3 cabinets.

I skipped ahead in the instructions to see if there was anything else that could be done while waiting for the glue on the bracing to dry. I found that the baffle (panels 12 and 13 + supplemental ring) and the bottom (panel 10 + an unnumbered panel) could each be glued together at the same time. Forgot to get pictures of that, but I used the recommended dowel pins to make sure those panels were aligned and glued them together. I set weights on them and allowed it to dry.

Missed a few photos (will try to get some on the next build), but here's after gluing the baffle, bottom, and port braces in.
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Next the rear panel (11) was glued into place. Again, a couple extra clamps would have been nice, and I'll definitely be using more for the remaining cabinets.
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The last assembly step was to glue the roundover panel to the front baffle.
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After all the glue was dry, I put the cabinet on a furniture dolly and moved it into a paint booth I setup in the unfinished portion of my basement behind where I'm building my theater. I gave it a quick sanding to remove glue drips in a few places.
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I had some Behr Marquee One-Coat paint left over from painting the ceiling and wall behind the screen in my theater. I decided to use this instead of the Duratex or separate primer + paint recommended in GSG's shopping list. The subs are going behind my screen wall and will be hidden from view, so the paint didn't need to be perfect.

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The paint is pretty shiny when wet, but dries to a nice matte/flat black. I made a mistake while spraying and had a big run just above the port. I tried to wipe it off with a paper towel and re-spray it, but that really only made it worse. The rest of it looks great, especially for a quick 5 minute paint job. If I ever build something like this to put in an area where it would be visible, I would definitely use this paint again, but just take a little more time with it. I kind of liked the shiny-ness when it was wet, so I'd maybe go with a high gloss instead of flat if I intended to have it on display.
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Once the paint dried, I installed the NSW. The instructions said to use 4' of speaker wire, so I measured exactly 4' and used it. I will add an extra 6" for the rest of them, because it was a little difficult to get the NSW into place with the speaker wire just barely reaching the top of the baffle. I had to have my wife and oldest son struggle to hold the NSW above the opening while I squeezed my hand under it to attach the wire.
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The instructions said to drill 7/64th pilot holes and then screw #6 1-5/8" drywall screws in to mount the driver. I noticed that the head on the screws fits right through the mounting holes on the NSW. Didn't seem like it'd properly hold in in place. I had some lock washers that were just the right size laying around, so I backed the screws out and added the lock washers. Seemed like a better fit. I was a little confused at this step, since I had bolts, washers, and wing nuts that were listed in GSG's shopping list, but not used at all in the build. It wasn't clear to me that those were only used on the original Full Marty where the baffle is removable. They aren't used on the v2.1 Roundover Full Marty at all.

After getting the NSW into place, I moved the subwoofer over next to my screen and hooked it up for testing. My youngest (he's 9) says "It's ridiculous!" I told him we still had 3 more to build, and he said "Why do you need 4 huge subwoofers?!" :ROFLMAO:
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After verifying everything worked, I put it behind my screen. The door I installed to access behind the screen was just a little too narrow to fit it through, so I had to squeeze it through the opening on the right side of the screen. The narrowest part of the cabinet is 23.5" wide, and the opening is only ~23.75" wide. Scraped the paint quite a bit, but we managed to get it back there.
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After getting it into place, I re-ran the YPAO calibration on my Yamaha CX-A5200. I like to use the opening scene of Mad Max Fury Road as a test. With the lights off you can't see the sub, and that's WITHOUT having built the fabric panels to cover the exposed areas around the screen.
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I built the room with soundproofing. My living room is directly above it, and you usually can't hear movies playing from up there. With the just one of these NSW powered Full Marty's in place and the volume cranked up, my kids came running downstairs and into the theater yelling "DAD, YOU'RE SHAKING THE WHOLE HOUSE!" :ROFLMAO:

To be fair, I did have the volume a bit higher than normal, higher than I'd comfortably be able to watch a whole movie. ;) I can't wait to get the rest of them built and dialed in. Just one already blows away the SVS PC-4000 I was using. I'm able to build 4 of these monsters for about the same amount of money that the pair of SVS PC-4000's cost me when I bought them a couple years ago.

Even though the new V2.1 Roundover series was labeled as "intermediate" skill level, I found it to be really easy for my first ever build. The laser cuts are great and all the pieces fit together perfectly. Highly recommended if you're a first timer like me. The whole assembly of this first cabinet was done in just a few hours on Friday afternoon. Painting took 5 minutes on Saturday afternoon, and less than an hour on Sunday afternoon to install the driver, put the cabinet in position, and start enjoying it. Fun little weekend project!
 

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Very nice. I have Marty’s on my list for my dedicated room in my new house being built. I bet they thump!

I’m currently sitting on two new sub cabinets, desperately looking for a capable carpenter to finish the cabinets in an expensive veneer I’ve purchased to match my Palladium’s.

In Charlotte, NC if anyone knows anyone nearby.
 
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Discussion Starter · #4 ·
Very nice. I have Marty’s on my list for my dedicated room in my new house being built. I bet they thump!

I’m currently sitting on two new sub cabinets, desperately looking for a capable carpenter to finish the cabinets in an expensive veneer I’ve purchased to match my Palladium’s.

In Charlotte, NC if anyone knows anyone nearby.
Thanks! They do indeed thump. That vaneer sounds like it should look nice if you can get it done.

wow NSW 21 nice have you test SPL how many dB hit let say 10hz hit dB ULF try EOT = edge of tomorow
Yeah, 4 of them by the time I'm done! I'm getting ready to paint #2 and start building #3 now. I don't have an SPL meter yet. Still need to order a UMIK-1 so I can take measurements with REW. I don't have EOT, going to have to pick up a copy.
 

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Thanks! They do indeed thump. That vaneer sounds like it should look nice if you can get it done.


Yeah, 4 of them by the time I'm done! I'm getting ready to paint #2 and start building #3 now. I don't have an SPL meter yet. Still need to order a UMIK-1 so I can take measurements with REW. I don't have EOT, going to have to pick up a copy.
ohh so you plan getting UMIK-1 right

you fell like IMAX Theater sound beat NSW 21 right
 

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So with that volume of air being moved what keeps the screen from waving? About 20 years ago I had 2 15" that would make my screen move back and forth an inch or two....very annoying and that didn;t last long
 

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Discussion Starter · #7 ·
So with that volume of air being moved what keeps the screen from waving? About 20 years ago I had 2 15" that would make my screen move back and forth an inch or two....very annoying and that didn;t last long
The subs are mostly below the screen, so the air isn't being directed at the screen. They're also sitting on cement and not touching any of the walls, so no vibration issues (yet), but I only have 1 of 4 built and in place at the moment. It's a Stewart Filmscreen Balon borderless frame with their StudioTek130 Perf material. The screen material is stretched extremely tight around the frame, it was difficult to get it to move to install it, so I doubt waving will be an issue (it hasn't been an issue so far). The few inches that you see the bottom of screen extending over where the sub is, isn't just loose screen material. It's a very sturdy aluminum frame. There are steel pucks screwed into the 2x4 studs the screen is mounted to, and magnets along the bottom edge of the screen frame that hold it to the wall. It's very sturdy. ;)
 

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Discussion Starter · #8 · (Edited)
Finished up build 2 of 4 last night. Got more clamps, and did a couple things a little different. This one came together better and easier than my 1st attempt.


I started by gluing panels 1, 2, and 3 (top and sides) and used 4 clamps to hold it together, plus temporarily inserted panels 4 and 5 (port top and back) backwards for bracing to keep things straight. At the same time I glued the 2 panels for the bottom (10 + unnumbered) and the baffle together. I let all this dry for 30 minutes.
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Next I glued panels 4-9 (port and bracing pieces) in with it still laying on it's back. The instructions say to tip it upright here, but I found it easier to glue first before setting it upright. I attached 7 clamps on the front before tipping it upright, then 3 clamps on the back, and let it dry for 30 minutes.
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Next I flipped it over and glued the bottom (panel 10) in. 2 clamps in front, 2 in back, and 2 across the sides. There was a little bit of a gap where panel 4 and 5 meet, so I slid 2 clamps under the bottom to correct it. Let it dry for 30 minutes.
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Next I laid it face down and glued the support pieces into place and let it dry for 30 minutes.
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After this step, the instructions have you flipping it over and gluing the baffle on. I did that on the first one, but thought it was odd to not glue the back panel (11) on while it was already face down. I decided to deviate from the instructions here and glue the back panel on first. Clamps and weights and let it dry for 30 minutes.
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Next I decided to slide a couple 2x4's under it when I flipped it over to glue the baffle on. This allowed me to do much better clamping than how I did the 1st one. Let it dry again for 30 minutes.
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Last assembly step, remove all the clamps and weights, glue the roundover baffle panel, and re-clamp. It was getting late, so I opted to call it a night and let the glue dry over night.
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The next day I wheeled it into my paint tent in the other room, gave it a quick sanding, and a quick coat of paint using the extra flat black Behr Marquee One-Coat paint I had on hand. While the paint dries within about an hour, I had other things to do, so I just let it dry over night.
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The next day I installed the 21" Eminence NSW 6021-6 driver. A bit of a shame that I scuffed the paint up putting the driver in. It is going to get scuffed up even more getting it into position behind the screen, but it's hidden and won't be seen.
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After the driver was installed and tested, I put it behind the screen right next to the 1st one.
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With 2 of 4 NSW Full Marty's in place, I decided it was time to take the SVS PC-4000 out of the theater and put it back upstairs in the living room with the other one I have there.

I'm only at the halfway point, and really impressed already! Going to start #3 tonight.
 

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wow NSW 21 nice have you test SPL how many dB hit let say 10hz hit dB ULF try EOT = edge of tomorow
10hz is well below the tuning point, so you're really just demo'ing his room gain at that point. With my 4 18's (2 behind the screen, 2 nearfield to the MLP) and the same amps, I was showing ~119db @ 20hz, and 125+ from 30hz on up, sitting at the MLP. (Meter is maxed at 125). With the added cone area, I'd imagine he'd be +6dB or so over me?
 

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Not that you’ll see it often, but great job on the paint finish!
Your theater is looking great man!


Sent from my iPhone using Tapatalk
 

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The subs are mostly below the screen, so the air isn't being directed at the screen. They're also sitting on cement and not touching any of the walls, so no vibration issues (yet), but I only have 1 of 4 built and in place at the moment. It's a Stewart Filmscreen Balon borderless frame with their StudioTek130 Perf material. The screen material is stretched extremely tight around the frame, it was difficult to get it to move to install it, so I doubt waving will be an issue (it hasn't been an issue so far). The few inches that you see the bottom of screen extending over where the sub is, isn't just loose screen material. It's a very sturdy aluminum frame. There are steel pucks screwed into the 2x4 studs the screen is mounted to, and magnets along the bottom edge of the screen frame that hold it to the wall. It's very sturdy. ;)
As soon as you said screwed into the studs that would certainly dcrease any movement. I couldn't tell, and still can't, that the drivers are below the screen so I'll take your word for it. 4 21" drivers would be putting a lot of pressure on the fabric no matter how tight it is. Let us know how it worked out once you have the other 3 built.
 
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Discussion Starter · #12 ·
As soon as you said screwed into the studs that would certainly dcrease any movement. I couldn't tell, and still can't, that the drivers are below the screen so I'll take your word for it. 4 21" drivers would be putting a lot of pressure on the fabric no matter how tight it is. Let us know how it worked out once you have the other 3 built.
You can't see them in the pics with the lights on showing the screen? 2nd and 3rd to last pics in the original post, and the very last pic in my follow up post for build #2. They're huge and nothing is covering them up yet... The subs are on their side below the screen acting as a platform for my towers to sit on. Only the left tower is sitting on top of one at the moment since only half the subs have been built.
 

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@Everyone Small World Sir. I was talking to an old coworker / friend of my from IL Chris (I live in AZ now) and was telling him I decided to replace my HSU subwoofer with some Marty builds and suddenly he sends me the pictures in this thread stating his friend from the Nat guard is building four of them. I had seen this thread a week back before talking to him LOL.
 

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Discussion Starter · #14 ·
@Everyone Small World Sir. I was talking to an old coworker / friend of my from IL Chris (I live in AZ now) and was telling him I decided to replace my HSU subwoofer with some Marty builds and suddenly he sends me the pictures in this thread stating his friend from the Nat guard is building four of them. I had seen this thread a week back before talking to him LOL.
Ha! He mentioned that to me yesterday. He hasn't been out here since before I started building the theater (stupid pandemic)... thinks I'm totally insane building these four 21" Full Marty's. :ROFLMAO:
 

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Discussion Starter · #15 · (Edited)
Number 3 is in position. Thought I'd give a behind the scenes look for this one...

As I mentioned in my first post, the door I installed for access behind the screen is too narrow to fit these 21" Full Marty's through. Luckily the opening to the right of the screen is just wide enough to fit them through. Unfortunately there's a 2x4 nailed into the cement across the bottom of it, so the Marty's have to be lifted over that while squeezing them through.
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I place a furniture dolly on the other side of the wall. There's just enough room to rotate the Marty's once they've been squeezed through the opening.
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After rotating and rolling into position, I carefully lay it on it's side. Yes I left the bottom unpainted. Once the final Marty is in position it won't be visible.
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After climbing over it, I push it up against the other Marty's and set the center channel tower on top. My wife thought it was funny that I was climbing on it. :rolleyes:
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The right channel tower will go on top the 4th Marty once it's built. Replacements for the panels that were damaged during shipping just went out today, so it'll probably be a couple weeks before I get the last one built.
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View from the front with the 3rd Marty in place:
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Discussion Starter · #17 ·
Replacements for the panels that were damaged in shipping arrived on Saturday. Got the last cabinet built and painted over the weekend, then finally put it into position last night. I might try to slide them over to the right a bit to center them under the screen more. Sounds good where they're at though.

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