My long, one-car garage studio, construction phase

[Bigsby]

I've made a bit of progress since my last post; getting close to being able to start testing the room!

I built silencers for the control room: 2 layers of 5/8 OSB with Green Glue between:

cr silencers no liner.jpg

Control room silencer.jpg

And then installed them--below is a shot of the exhaust silencer which is installed in the space behind the left soffit which will also be stuffed with scraps of insulation:

cr silencer installed.jpg

...and how it looks from the outside:

CR Exhaust vent.jpg

I used the same method (suggested by Stuart) that I used earlier for the live room ducting between leaves to avoid flanking paths: 2x6 material rabbited out to accommodate 1/2 of neoprene "connector." This is a great solution for those of you who don't have room between your leaves to install a silencer:

Duct.jpg

duct with neoprene.jpg

I temporarily assembled the soffits for initial room testing. Once I've done my initial REW tests with no treatment in the room I will take them apart and install hangers, insulation, speaker venting, etc.

Left Soffit.jpg

soffit right.jpg

soffits center.jpg

....which brings me to where I am right now...ordering glass today and trying to get organized for REW testing. A couple questions:

1. In the instructions for the REW software, they mention using an SPL meter to take the room measurements (using the output on the side). If this will be adequate, I'll go this route (I have the digital Radio Shack meter that a lot of people have). However, I was also thinking of getting the Behringer ECM 8000 measurement mic if that would be a lot better. I want to do this right, and the mic retails for only $60 U.S., but every penny counts at this point. Any thoughts on that?

2. I've just got the first layer of the soffit bezel installed, which is 3/4" particle board. On top of that, I'm planning to have 1/2" birch plywood that will follow the angled contours of my new ( ) Adam A7X's. Is it OK to do my initial test without the finished bezel layer in place? I'd rather do that a little further down the road, after this initial test with no treatment in the room.

I've been working on a new Sketch Up file, with accurate, as-built dimensions. I am not very good at this program, but I will soon post the new file so that everyone can see the exact measurements as I begin REW testing.

Thank you in advance for your feedback!! I still have a long way to go, but I'm starting to see a light at the end of the tunnel, which I'm hoping is not an oncoming train

[Soundman2020]

they mention using an SPL meter to take the room measurements (using the output on the side). If this will be adequate, I'll go this route (I have the digital Radio Shack meter that a lot of people have). However, I was also thinking of getting the Behringer ECM 8000 measurement mic if that would be a lot better.

If your meter has a direct analog out from the mic, then that should work OK, but a good measurement mic is also a good option, plus it means you then have another mic to add to your arsenal! A measurement mic is a good omni mic anyway, with fairly flat response across most of the spectrum, so there are plenty of places you can use it for tracking! Personally, I would get one, but if money is tight, then the mic out from the SPL meter will work fine.

Is it OK to do my initial test without the finished bezel layer in place?

Yeah, that's fine. The initial test is just to get a general idea of how the room is behaving, mainly for modal issues but also for first reflections and RT60, and the final finish bevel is not going to make a huge difference to that. So go ahead without it, for the initial "baseline" test.

One other thing: you might want to consider taking the rear panels off your A7Xs, and mount them in a more accessible place, so you can do the adjustments without having to take the speakers in and out all the time. That gets tired, real quick! You'll have to extend the wiring a bit to do that, and it most likely cancels your warranty, but personally I think it is a good move. Worth thinking about!

- Stuart -

[Bigsby]

Wow--thanks for the quick reply, Stuart! I'll probably end up getting the mic...we'll see. At this point I just need to install my glass and start testing! Or more accurately, start trying to figure out how to start using the REW software

Good point about the rear panel of the Adams, although that makes me a bit nervous. I might decide to put up with the hassle. If I decide to, there's no harm in placing a removable "frame" around the speakers to facilitate that, right? I think others have done that here, Jester for one. What I have in mind is just a removable section that surrounds the speaker that is the same thickness as the rest of the bezel. That way, I don't have to remove the entire bezel if I need to remove the speaker.

[Soundman2020]

What I have in mind is just a removable section that surrounds the speaker that is the same thickness as the rest of the bezel. That way, I don't have to remove the entire bezel if I need to remove the speaker.

Right. Barefoot has a design somewhere here on the forum for doing that.

- Stuart -

[Bigsby]

Thanks, Stuart--I think I'll do that, then. It will make removing the speakers and making adjustments to them easier, without removing the back panel.

Mark

[Bigsby]

Hello again--
Well, I've downloaded REW, so I guess it's time to do some baseline testing, before any treatments go in. The soffits are built, but there's no insulation or hangers inside, and the final bezel that will follow the contours of the speaker fronts is not attached. After baseline testing, I will take them apart and install treatment before putting them back together.

Here's what the room looks like currently:

testing left.jpg

testing right.jpg

testing back.jpg

I picked up a Behringer ECM 8000 for testing, and I'm using my Apollo Quad for the interface. The speakers are Adam a7X's (which I love, by the way, Stuart). The mic is set up where my head will be in the listening position, pointing up, at ear-height.

Once set up, I started testing. I will post some results, although I have to admit I don't really know enough to interpret them yet. I'm guessing the verdict will be that "things are pretty bad," given how small the room is.

I did an initial test with both speakers on:

left and right spl.jpg

left and right waterfall.jpg

Then I ran the speakers separately-- first the left speaker:

left spl.jpg

left waterfall.jpg

...then the right:

right spl.jpg

right waterfall.jpg

And here's a left and right overlay waterfall:

left and right overlay waterfall.jpg

So that's where I'm at. Like I said, I'm pretty ignorant about how to interpret REW; I will begin studying to increase my knowledge. In the meantime, if anyone has any input on these initial tests, it would be much appreciated. Does it appear that I've captured enough data so that I can begin the first phase of treatment in the room (rock wool, insulation, hangers)? Are there other graphs that I should post? Different parameters?

Next, I will post a SketchUp file so that you will be able to see the way the room lays out more accurately.

Thank you in advance for any advice you can give!

Mark

[Bigsby]

Ok--
I've attached a simplistic, but very accurate model of what the CR looks like. I'm embarrassed to be posting such a crude model on a forum with so many talented SketchUp artists, but I think it will give a clear idea of the room I'm working with. I realize that I could have set it up to be more user-friendly (using layers and things that I still haven't mastered), but please bear with me and just "hide" things that you need to get out of your way.

I should add that this model only depicts the inner-leaf framing; the outer leaf is not in this model. Also, in reality, the ceiling framing on the right side of the room does not extend beyond the right wall; I just couldn't figure out how to "cut" it in the model. So, not to worry: The control room is completely decoupled from the outer leaf and from the live room.

The walls of the room are all framed inside-out. The ceiling is framed in the traditional way, with the drywall to the inside of the room. Drywall everywhere is two layers of 5/8, with Green Glue in between. I've also drawn a basic idea for a cloud that would be hard-backed and hanging at 12 degrees front-to-back (except for the rear section of the cloud).

Thanks again!

new cr.skp

[Soundman2020]

Great!

I picked up a Behringer ECM 8000 for testing, and I'm using my Apollo Quad for the interface.

Did you calibrate the system correctly? Not just the sound card (interface), but also the SPL levels. The REW manual has some guidelines for that. Or I can PM you with the way I do it. You need a sound level meter for the calibration process...

If you did calibrate it correctly, then don't forget to check that the sound card calibration file is included in all measurements. You should also use the generic ECM-8000 mic calibration file (on the REW forum). It won't match your mic exactly, but it will be better than nothing!

The speakers are Adam a7X's (which I love, by the way, Stuart)

The mic is set up where my head will be in the listening position, pointing up, at ear-height.

It's an omni, and this is not intuitive in the least, but the recommendation is to point it straight forwards (between the speakers), or at angled upwards at about 45°. Still trying to figure this out myself, but some experts say that pointing it up is not the best idea, while others say that's the best place to point it...

I did an initial test with both speakers on

. It looks pretty decent for an untreated room in the pure frequency domain, but there's obviously a lot of ugly modal stuff and reflection stuff going on in the time domain! Also, your SPL graphs are showing the entire spectrum, but you really should be concentrating on just the low end for now. So zoom in (both axes) so you are looking at around 15 to 400 Hz, and maybe 50 to 110 dB.

But it would be better to post the actual MDAT file here, so we can download it and analyze it in more detail. There's a lot more useful stuff that can be gleaned from REW then just SPL levels and waterfall plots...

Thank you in advance for any advice you can give!

I would suggest repeating the tests with the mic angled only 30° (or so!) up, and double check that the tip of the mic is at the distance where your EARS will be, not where your NOSE will be! In other words, set it up so that the tip of the mic is exactly where the middle of your brain will be, as you sit at the desk, mixing.

Take a new reading like that, then post the MDAT file here, and then do the following: Measure the exact location of the tip of that mic in the room, in all three directions, very accurately! This is very important. Since this is your baseline test, you will want to compare all future tests to it, every time you add some treatment to the room. You MUST get the mic back to the exact same position every single time, accurate to within about a quarter of an inch or so. If not, then you can't compare the graphs. They will still be valid, just for a different point in the room, and therefore not comparable. So measure the position very carefully, using fixed reference points that won't move or get covered up with treatment, equipment or anything else. And not down those measurements carefully. It really is important to get the mic back to the same point, every time.

And one other thing: each time you do a REW test, be invisible, acoustically! In other words, get out the way: don't stand between the speakers and mic, or between the mic and a major surface, and don't stand in different places every time! Just crouch down behind the chair, or something, so that your body is not blocking anything important.

Does it appear that I've captured enough data so that I can begin the first phase of treatment in the room (rock wool, insulation, hangers)

Yup! I would start with hangers, then measure again with REW and post that.

- Stuart -

[Soundman2020]

I've attached a simplistic, but very accurate model of what the CR looks like ...

Looks pretty good to me!

One thing I noticed: I see your silencer box for the exhaust air, but I don't see the one for the supply air... ?

Also, I don't think your cloud needs to go that far back. You could probably lose the last section, angle the middle section more, and raise the whole thing closer to the ceiling, so the room doesn't look so low, visually.

- Stuart -

[Bigsby]

Wow--Stuart--you are the best! Thanks for the quick replies!!

A couple responses....

Did you calibrate the system correctly? Not just the sound card (interface), but also the SPL levels. The REW manual has some guidelines for that. Or I can PM you with the way I do it. You need a sound level meter for the calibration process...

I had trouble with this. I set up the loopback connection according to the instructions (at least as I understood them) going from channel one line out to channel one line in. I could not get a signal on the input once I started the calibration process. I used "Room EQ Wizard: REW Room Measurement Tutorial," which is a youtube video by Glenn Kuras that the REW forum links to. Long story short, Stuart, if you have any ideas, I'd love to hear them. I finally gave up on this step, given that the video claimed it "wasn't that important" since I will be A/B'ing--trying to improve upon my baseline measurements with room treatment. So....Help(?)

I did calibrate the SPL levels with my Radio Shack meter, Although it's very possible that I didn't do that right, either.

Secondly:

One thing I noticed: I see your silencer box for the exhaust air, but I don't see the one for the supply air... ?

Yes, the silencer for the supply air is outside the room. The only visible thing is the hole in the wall (on the left side of the photo below), so I guess I shouldn't brag about how accurate my model is :

testing back.jpg

Finally:

Also, I don't think your cloud needs to go that far back. You could probably lose the last section, angle the middle section more, and raise the whole thing closer to the ceiling, so the room doesn't look so low, visually.

Great to hear--this is just a "first draft" of the cloud--it would be nice to be able to raise it a bit!

Thanks so much for your help, Stuart.

Mark

[Bigsby]

Back again. I figured out what I was doing wrong when I was trying to calibrate my interface, so I ran tests again, this time with the calibrated interface as well as the calibrated ECM 8000. When I calibrated the SPL meter, I had it set to 79 db. Maybe this is too loud? Is there a better range to set it to? Not sure, but the waterfall graphs look quite a bit different than yesterday. For right now, I'll just post the SPL graph of both speakers:

both speakers calibrated.jpg

Also, I'm trying to upload my mdat file, but I'm being told that "the extension mdat is not allowed." Any suggestions for successfully uploading mdat files?

Thank you!

Mark

[Soundman2020]

There's still something wrong there: It is now showing that you conducted the test at a level of 160 dB If that were the case, your house would be in little pieces all over the neighborhood, and you would be a red puddle on the floor.... Well, not quite that bad, but that's waaaay beyond any possible level attainable in reality. It's about a thousand times louder than the loudest rock concert on record...

Also, the very low end is rather unlikely: It shows that your system is still producing sound at 15 Hz that is only 40 dB down from what it does at 200 Hz: You'd need some pretty amazing sub-woofers to do that!

So I think there's something wrong here. I'll PM you the procedure that I use.

- Stuart -

[Soundman2020]

I'm trying to upload my mdat file, but I'm being told that "the extension mdat is not allowed." Any suggestions for successfully uploading mdat files?

Use a file-sharing service such as Dropbox, and just post the link here.

- Stuart -

[Bigsby]

Hi Stuart--

So I think there's something wrong here. I'll PM you the procedure that I use.

Yeah, I thought so. I'll look forward to your message.

Thanks!

[Bigsby]

Hi--
Here's a link to a second try at baseline measurements. It's not the 160 db version , but still not sure if it's correct. Seems like maybe the low end is still an issue.

http://www.4shared.com/file/WNZ7ShPd/ba ... ed_II.html?

Thanks in advance for any ideas!

Mark