The JohnBomb build - Page 2

Yes. They are 160v.2 drivers.

http://www.edesignaudio.com/product_...products_id=36

trimmed, caulked, primed, and painted . . . VICTORY!

A few more... and some chalk art by my daughter.

I still have to clean up all this crap...

But I'm feelin' good!

Totally unrelated to progress: I just measured the cicadas here in Nashville at 92 db!!! Can you believe that @#!$!#!

OK, time for a work update. I've built boxes that go in between the joists of the ceiling. These boxes are made out of OSB/drywall, and probably weigh up to 80 pounds- two of them hold can lights. The boxes float on 7/8" 25 gauge hat channel, with R13 interspersed between the boxes and joists.

The point of the boxes? I can fill them with whatever acoustical treatment I need, based on how my REW sweeps turn out. I'll cover the edges of the boxes with drywall and the actual cavities with GOM panels.

As you can see, I had to use pulleys to get the things up


John

Also, I had my HVAC lineset run down the outside of theater wall, in order to cut down on the noise. It's not the prettiest thing on earth, but no one can see it from the street. You can see one of the joist bays lined w/ rockwool- to cut the remaining internal noise down.

"Why are the clips and channel so close together on the ceiling? Are you doing something different in the middle of the room where there are no clips and channel?"

Good question. I'm leaving space within the center of the boxes so that I can fit PVC pipe bass traps into the bins. These tubes will be either 1/4 or 1/2 wavelength of whatever the low floor to ceiling nodes measure and will be tunable. This probably seems odd at the moment, but I'll post pics, graphs, construction methods, etc whenever I finally get to that point- it'll all make sense then.

Thanks everyone,
John

Yeah... how 'bout that. That's how much I love weekends at work! I may take you up on the extra set of hands offer, as I've got ceiling drywall coming up in the (hopefully) not too distant future.


Awesome, man. You'll probably do it better than I did.

John

I've decided that I need to get the room sealed up so that I can start running some acoustical tests, and that means... build the door. Or, in my case, a section of wall that swings open. So, for the last couple of evenings, I've worked on the door jamb.

I didn't realize that shimming this thing would require so much effort! Take a look at the twisted and bowed 2x4 I had to work around behind the jamb and you'll see why. I took a 2x6 and cut it down to about 1x4 inches, planed and jointed nice and flat. I'm going to attach cherry pieces to the sides and top of the jamb to complete the door frame and trim the frame and door with cherry. The drywall mud is there to fill large gaps- I won't be surprised when it cracks, but as I'll probably cover the stairwell with wallpaper, hopefully I'll never know... :/

John

Well, I know this won't be a popular move: I've decided to scrap the double bass array! Reality has set in, and I've realized that the seats need to be moved as far back as possible in order to allow for reasonable viewing angles as well as appropriate acoustical treatment. Therefore, the riser has to butt up against the rear wall and partially cover what would have been the rear speaker mounts.

The good news, I hope, is this: it won't matter. My sub response is pretty good up to about 60 hz (see post #22), and likely will will improve once I add lots of bass trapping. I think this response represents that of the entire basement, as I currently have no door and lots of open space above the rear speaker box. So, my plan is to "let the bass out" of the theater. That is, drill lots of large holes through the MDF of the (former) rear speaker box and cover them with very thin material, such as 1/8" luan or 1/4" drywall. I'll have to experiment to find out what works best.

Speaking of bass trapping, I'm probably going to stuff the entire rear speaker box with R30, creating a bass trap that's about 32" deep, 7 feet tall, and about 9 feet wide. I'll add lots of side/ceiling fiberglass and helmholtz resonators (either tuned pipes or membrane traps) where needed. My plan is to go for a very dead room and use electronics to make up for the lost ambience. I'll get into LEDE (live end dead end) theory, ISD (initial signal delay), ambience, etc. later when I finally get to acoustical analysis.

Here's my riser progress as of now. I'll mount 2 more 15" Elemental Designs 160 v2 subs in the front of the riser and leave the back hollow, to be filled with bass trapping- fiberglass and or helmholtz resonators as needed. Check out the home brew clamp jig I concocted to get my frame level- that worked out really well.

The riser will be covered with cherry wood and will support two "zero gravity" Relax the Back chairs. If any of you have back problems, these chairs are a must have. I've never fallen asleep in any other chairs but these.

John

A bit of progress:

1) Riser (mostly) framed and subs installed. Will still use front single bass array speaker closet w/ 4 ED subs from 10-60 hz or so, depending on modes. Will cover riser w/ cherry wood later.

2) Cutting my own cherry trim- when using hand planes and scrapers, this takes time. I spent all day on the router table and then worked from 10:30 pm to 3:00 am just scraping the header for the door jamb- and it's still not done...

Thanks, Fred. I used diagonal supports to (hopefully) allow more air to enter the speaker enclosure more quickly, thereby lowering the woofer's compression ratio... plus, it looks cool

John

Another update... Door jamb done! I would have had it done sooner if I hadn't spent about a month of sanding and re-mudding drywall to try to get the header flush with the wall. As you can see, I just tore it out and will re-mud it later.

The jamb: cherry wood from my father in law's barn, that he ripped down on his antique sawmill about 15 years ago. It's been sitting in my shop, waiting for a project

I used handplanes and scrapers for all final finishing and dimensioning. The finish from a power planer isn't uniform enough for my taste. I sealed the wood with two coats of Charles Neil's blotch control preconditioner, to minimize blotching- cherry is really bad about that.

https://charlesneilwoodworking.3dcar...trol_p_47.html

I then finished with two coats of shellac, and I'm pretty happy with the results.

John

Thanks, Jon. Yeah, I'm getting pretty good at thread necromancy. I've clicked the "I acknowledge that this thread is old" button more times than I can count