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post #121 of 127 Old 08-16-2014, 10:05 PM - Thread Starter
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Originally Posted by TMcG View Post
1. Details are still being released, but a common theme stressed by Dolby and noted by those involved in the system's development is that timbre-matching all of your speakers in the system is critically important. Moreover, the radiation pattern of that speaker is recommended to be 90x90...or in other words, the same focused dispersion pattern in both horizontal and vertical axis.
The reason I was thinking that maybe it would be okay to have ceiling speakers that didn't match the others was the fact that they will be offering "add-on speaker modules" that add up-firing capabilities to your existing speakers. The white paper stresses that you don't need to give up your existing speakers. Now, there's virtually no way that those speaker add-ons will be voice matched with the majority of speakers that they are added to... which suggests to me that the ceiling sounds aren't as critical to be perfectly matched. But yeah, you're right that the white paper is incredibly light on useable details.

As far as the ceiling speakers being 90x90... I wonder how you can tell if the documentation doesn't say anything like that?
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post #122 of 127 Old 08-17-2014, 04:31 AM
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The reason I was thinking that maybe it would be okay to have ceiling speakers that didn't match the others was the fact that they will be offering "add-on speaker modules" that add up-firing capabilities to your existing speakers. The white paper stresses that you don't need to give up your existing speakers. Now, there's virtually no way that those speaker add-ons will be voice matched with the majority of speakers that they are added to... which suggests to me that the ceiling sounds aren't as critical to be perfectly matched. But yeah, you're right that the white paper is incredibly light on useable details.

As far as the ceiling speakers being 90x90... I wonder how you can tell if the documentation doesn't say anything like that?
I was going by memory and was slightly off....the dispersion pattern should be minimum 90x90. From the bottom of page 8 in the Dolby Atmos White Paper PDF:

[/quote]Dolby recommends ceiling speakers with wide dispersion patterns. If you use ceiling
speakers with narrow dispersion (less than 90 degrees x 90 degrees) or those with aimable
drivers, angle the drivers slightly toward your listening position.[quote]

As for the timbre matching, I also should have been more clear - as you would expect, having everything timbre-matched is the recommended ideal. There's absolutely no way Dolby is expecting that every system have the same type of speakers. Heck, in their most recent "home" demo rooms, THEIR speakers are different and not completely timbre-matched. Many in attendance mentioned this. And let's face it, to be successful, Dolby needs your average Joe to buy in to the technology, fully expecting that *any* sort of ceiling speakers will be used and mounted just above a dusty Billy Bass and store-bought "art" hanging on the walls.

Apparently Dolby is preparing to make another round of announcements with even more technical details during CEDIA and shortly thereafter. Since you have attic access and the ability to cut into the ceiling after-the-fact, I'd just run four speaker wire tails up into the attic and wait for the whole matter to be sorted out.
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post #123 of 127 Old 08-17-2014, 02:04 PM - Thread Starter
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Insulation - August 17, 2014

Talked Down from the Ledge

I mentioned in my earlier update that I had installed outlet boxes in the walls and was vacillating on whether or not that was a good idea. Well, when @cw5billwade voiced his concerns, my doubt kicked into high gear and I was just seconds from going back in the room and ripping them all out! My wife talked me down from ledge, though. In the end, I'm going to keep them where they are and use them as my entry points for the outlets for the rest of the room, rather than run the outlet cables through the soffits/columns. I'll still have the speaker wire and lighting cable run through there, but not the outlet cable.

I wrote up an entry on how I applied the putty pads to the boxes in the Soundproofing Master thread: Applying Putty Pads.

One thing I didn't show in that bit was how I set the depth of those adjustable boxes. Those who have followed this build thread know that I try to avoid actually measuring things whenever possible and this wasn't an exception. It just so happens that I had some thin pieces of the actual 5/8" drywall that will soon be installed, so I just stacked up two of them and extended the box to be flush with them:



Insulation!

After the outlets were all prepared, I could start on the insulation. Well... technically I did all of the insulation except for the outlet bays, but conceptually the putty pads did need to happen before insulation. I had three left-over batts from a previous insulation task and so those went up first:



Those are paper faced, which isn't at all needed in AZ. In fact, you really shouldn't have a vapor barrier at all in block homes in AZ, so I was considering removing the paper again. The remainder of the insulation was some new batts I bought at the same time as the lumber and drywall. The supplier only had insulation intended for steel stud walls in stock. It is fiberglass, but it's a full 24" wide rather than the nominal 23" found in batts intended for wood framed walls, and was the full 8' high, rather than the 7-9" found in typical batts. It also looked quite a bit different:



It installed similarly to normal batts, but that extra inch did cause it to bunch up a bit more on the edges. I was tempted to shave an inch off of each one... but honestly, it wasn't too bad, so I just left it.

Sharp eyes may notice a hole and what looks like water on the paper faced insulation in the background of the photo of the package of new insulation. Yep, that is water. It turns out that some water had gotten under the paper and had pooled there. When I installed it upright, quite a bit of it poured out of that hole. That convinced me that yes, I did need to remove the paper from the batts, if for no other reason than to dry them. Better believe that those dry in a hurry in 115 degree rooms.

I carved out the space for the outlet boxes, after the putty pad was installed. The putty was still sticky, so it actually stuck to the insulation a bit. You can see how much the extra-wide batts bunched up in some cases, in this picture:



Notably, working around the cable in the walls was a lot easier than expected. Since I put the cable so far back in the wall, I found that I didn't need to really split the batts like I typically did. There was enough slack in the cables to essentially be pushed back by the batt, too. All in all, it worked very well.

It took me a couple of days, since I had to break for installing the putty pads, but in the end, all of my walls were insulated!





Lesson's Learned

If I had to take away some lessons from this bit of the construction, they would be:
  1. Run cable as far back and as low in the wall as you can
  2. Use insulation batts designed for wood framed walls, if possible

I used the steel frame batts because I got a good deal on them and they could deliver it along with the rest of my load. Otherwise, though, it was notable to me how much easier it was to install batts made for wood frame walls. That extra width and height weren't terminal, but they did make it harder. Also, the steel frame stuff was substantially itchier than the white stuff.

Next Step

The next logical step is drywall! Man, so much of me wants to just do that, since it's such a big milestone. However, my practical side has won out in this case. Why? Well, there's still a decent amount of stuff that will need to be done in the attic after the drywall is up and, frankly speaking, my formal attic access hatches are pretty terrible. I've really been loving the extremely easy access I've had to the attic from having no ceiling. I decided that I'm going to make a decent attic hatch in the bathroom that adjoins the theater, which will allow me to haul stuff up there after the fact. And since it'll be a lot easier building the hatch from the attic, it makes the most sense to do that while I still have easy access.

So next week will be all about preparing the attic for the time when my open ceiling is gone. THEN it'll be time for drywall. Sooooo close!
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post #124 of 127 Old 08-17-2014, 02:36 PM - Thread Starter
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Pre-Drywall Soundproofing Baseline

The primary part of my soundproofing solution hasn't yet been implemented, since it's cornerstone is the drywall. That'll give me the majority of my Mass, Decoupling, and Damping. I do have my Absorption layer up, though, as well as the massive door. So I was curious how well the current setup worked, to give me a baseline when the drywall was up.

Alas, I don't have any portable way of producing any decent bass, so my (very quick and informal) tests were using an iPad hooked up to my Bose Wave Radio (circa 1999). I ran the Audio Tools suite on both the iPad and on my iPhone. The iPad was generating pink noise while the iPhone was used to run an RTA between 0 and 20kHz and the SPL calculation was flat, with no weighting.

Ambient

To start, I took measurements to establish my baseline of ambient sound. With everything off, I took measurements in the theater; just outside the theater door; in our living room opposite the theater; and down the hall in my son's bedroom. The ambient sound is surprisingly noisy in a few places. In particular, we have a ton of cicadas outside that are quite audible inside which meant that the noisiest place was in our living room. The two that matter, though, are just outside the theater and in my son's room:




If I re-ran the test in my son's room with A-weighting, then it might well be a lot lower than 35dB. It's subjectively very quiet in there.

Open Door Policy

The first test was to turn on the pink noise in the theater, which registered at 81.7dB. Noisy but not deafening by any means. I then ran the series of measurements with the theater door wide open. The results for outside the theater and in my son's room are:




Note that the graph for frequencies under 250Hz are scarcely changed. Yeah, my Bose Wave Radio doesn't have a lot of lower end grunt. The SPL for my son's room is roughly the same as ambient, but that's deceptive, since it sounded quite a bit different. That is, the pink noise, while not loud, was clearly audible. That's likely those frequencies that dip above 20dB in the graph.

Closed Door

I then closed the door, which shows the state of my theater so far.




That's a 22dB drop just by closing the door. Not bad. The pink noise is very clearly audible outside of theater, but it doesn't sound loud anymore. The graph for my son's room actually shows it to be quieter than ambient, but it's not really. The pink noise is just barely audible in there -- to the point that if the ceiling fan was running (which it does every night), then you wouldn't be able to hear the noise from the theater at all.

Conclusions

Since I can't get any decent bass nor can I get the source sound to be closer to 90 or 100dB, I can't say for certain how a movie would sound in the theater now. Still, it's not bad.

I will say this -- it gives me hope that my practical goal will be achieved while starting to dash my hopes that my fantasy goal will be achieved.

My practical goal is to be able to play a movie at full tilt with NONE of the sound getting down to the bedroom wing of the house; no outside sound coming in; and very little escaping from the outside. Considering how close I'm getting with no real soundproofing in place, I'm pretty hopeful that I'm going to hit that target.

My fantasy goal is to be able to play a movie at full tilt without you being able to hear it at all when standing just outside the door. That is, I want to be able to take a guest up to the door without them having any clue that something is actually running and when I open it, a massive rush of sound would pour out. It's pointless, but cool. I... don't think I'll hit that goal anymore. The door is just too much of a weak point, here, I think. We'll see.
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post #125 of 127 Old 08-18-2014, 01:14 PM
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did you see my comment in the sound proffing thread ref putty pads?
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post #126 of 127 Old 08-18-2014, 06:26 PM - Thread Starter
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Quote:
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did you see my comment in the sound proffing thread ref putty pads?
Yep. I check the Soundproofing Master thread every time I check my subscribed threads
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post #127 of 127 Old Yesterday, 05:38 AM
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The elictrican who wired my house does a lot of comercial work i.e. hotels and the like an when they do wiring for a sound proof conferance room this is how it is installed. Putty on the back side of the drywall.
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