HT8 and 4x JBL GX1200 Build - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 12 Old 03-22-2020, 10:51 AM - Thread Starter
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HT8 and 4x JBL GX1200 Build

Hello, I've built up a good head of steam (and enough posts), so it's time to post a build thread. I've been following this forum for a while, and am finally in a position to make some saw/MDF-dust. Everyone loves pictures, so lets get to it


Here is the "before." We got a 75" Samsung LED for black friday. I hooked up some powered bookshelf speakers to get us by.



After a lot of reading, I settled on HT8s for the L/R and some JBLs for the subs. This is a living room and while my wife is cool with whatever I build, I'd rather build something nice than betray that trust. To that end I came up with this design:



There are 4 subs, each with ~1.6cuft. I left space for the upcoming DIYSG HT-series horizontal center channel.

After I started cutting, I changed the design by rotating the sub boxes 90deg so now they're standing on end, with just isolation feet. I did this because 1. I realized woodworking is a lot harder than I expected, so I should simplify the design and 2. Now I have room for a 1099 center channel.


Once the HT8s arrived, I got to work. I live OCONUS so to cut down on shipping I decided to cut my own flat packs. Here they are near completion:



All done! I've still got some touch-ups to do, but I was so excited that I hooked them up as soon as the paint dried. They need to break-in, but they're a clear improvement over my last speakers:




Onto the subs. I got some 5x5 3/4" Baltic Birch. It was a pain to move:



Luckily I've got access to a community wood shop, where I got to use this guy:



I took the panels home to glue-up since the shop charges for storage, and ran into the eternal problem of not having enough clamps:



Test fitting the sub. The goal was to not block this light-switch: mission accomplished!




Once my wife heard the HT8s, she went from "cool" to really excited about the project, and asked if I could build the subs where you could see the drivers. A huge win, but now they actually have to line up



I was going to cut some scraps at the woodshop for the bracing, but now they're closed due to COVID-19. I have limited tools (and a less-than-square box) so I went with the through-dowel method. This is the progress as of last night:



I've got a week before my amp (XLS1502) arrives, so I'd like to have the boxes ready for glue-up by then. It looks like I'll have plenty of time the way things are going.

Any advice will be greatly appreciated. Thanks for reading!
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post #2 of 12 Old 03-22-2020, 11:32 AM
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given the co-location of the subs
they may need only1 channel of the amp,
if wired up properly (above my pay grade)

what sort of DSP can that amp provide
being a Berry fan / minidsp 2x4, 2x4Hd myself
and this: Now I have room for a 1099 center channel.

good looking clean tight work

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
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post #3 of 12 Old 03-22-2020, 04:13 PM
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@shellshox345 crazy timing dude, I am going to be doing the same thing in our new place. Pray to God jackass governor Newsome and covid-19 doesn't crash my RE market here in Sac. I will be doing ht8 with ht8 center (unless 1099 will fit) and instead of doing my dual jbl cs1214 end tables, I am going to be doing the single sealed 4x since it will fit under the tv between LR.



For you, everything looks good but as Asarose said, you might need some dsp. You can get the 2x4 minidsp or a behringer inuke amp that has dsp? As for bracing, here is an idea since you cannot get your wood guy involved.
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post #4 of 12 Old 03-22-2020, 04:34 PM - Thread Starter
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Thanks for the feedback. The XLS has a high/lowpass, but I'm going to get a MiniDSP down the line. I considered the Behringer, but given the price difference, plus the fan mod, plus the features the Crown has (more input types, dimmable display, the 12v trigger), it was a clear choice for me
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post #5 of 12 Old 03-22-2020, 05:00 PM
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^
for the subs, seriously consider the 2x4HD
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post #6 of 12 Old 03-22-2020, 10:28 PM - Thread Starter
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Didn't get a ton of time to work on the boxes today, but did manage to make some solid progress

Got all the dowels put in. Did a lot of measuring to make sure they wouldn't hit the driver, but until it actually went in I was nervous:



Got the baffle put on. I used PL Premium to make sure I got a good seal. It's nasty stuff. I was able to use the squeeze-out to seal up the gaps, so that's one less step. Once it's cured I'm going to wedge in the front/back braces. Definitely need more clamps...

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post #7 of 12 Old 03-23-2020, 10:59 PM - Thread Starter
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Another day of slow, but steady progress

Got all the through-dowels installed and cut flush. You can see the progression in spade-bit skills



Then I moved on to the front/back braces. These I cut to fit and wedged in, using PL if the fit seemed a little loose. I got a little over eager with this one and had to shim it:



I also glued the baffle on the other box. These things are getting heavy. I don't know how you guys are building these 21" Devastator monstrosities



Definitely going to have to clean the porch after this build...


The goal tomorrow is to get all the bracing done, flush-trim, and fill the seams. Fingers crossed
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post #8 of 12 Old 03-25-2020, 10:29 AM - Thread Starter
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Got everything I wanted done! I know MDF dust gets a bad rap (rightfully so), but routing the baltic birch was no picnic either. It kicked up this stuff that was like snow and it blew up behind my saftey glasses. I had to fish out my swimming goggles to finish it up



I also finished my bracing. I tried to put them no further than 8in apart. I guess we'll see if it's enough.



Both boxes are trimmed and the seams filled with drywall compound. Today I'm going to sand and prime them. We just got word we won't be back to work until April, so it looks like I'll be finishing these up quickly
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post #9 of 12 Old 03-25-2020, 11:00 AM
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FTR

Bracing- it depends

from observation over several years of a great variety of diy offerings

the range for separation when not usually or specially specified
seems to be most often between 6" to 8"


i.e.

in a 24" THTLP, braces at 8-ish and 16-ish
in a 30"- 7.5, 15, 22.5

the dowels , 3/4' or 1" depends on the beastlyness and PL3
not as easy to work with as short pieces and Kregs screws but
everything seems to work out . .

HTH

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
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post #10 of 12 Old 03-29-2020, 12:58 PM - Thread Starter
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All done! I had a little snag with a wire coming loose during assembly, but other than that there were no issues. It sounds so much better having the bottom octaves filled and letting the HT8s stay in their element. Here's a pic of them set up. I've got the HT8s on blocks because the paint hasn't fully cured on the subs (it's super humid here so that stuff takes forever)



I'm already building a TV stand that will fit all my gear. Luckily hardware stores are essential businesses!
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post #11 of 12 Old 03-30-2020, 11:20 AM
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Looks great! Good job!
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post #12 of 12 Old 03-30-2020, 11:38 AM
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Very nice!

Automation: Alexa- Harmony Hub- Wemo Dimmer Switch- Wemo Smart Plug BatCave: SY Triple Black
Video Image: JVC RS500- Sony UBP-800X- Chromecast- 125" wide 16x9 white over black spandex screen
Audio: 5.2.4 Marantz SR7011- (LCR) QSC 2180 - (Surrounds) (4) BIC FH6-LCR- (Atmos) (4) Dayton Audio B652 6-1/2-Inch- (Subs)2 23ishcuft ported HS24s 14-15Hz tune - 2 Devastator Minis B&C21ds115 - 4 PA460 in ported cabs 40Hz tune- FP20000Q- 2 Sanway FP10000Q- Crown XLS1500- . To be continued...
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