My long, one-car garage studio, construction phase

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: 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: Then I ran the speakers separately-- first the left speaker: ...then the right: And here's a left and right overlay waterfall: 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

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. :oops: 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!

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)

:yahoo: :thu:

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 -

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 -

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 :oops: : 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

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: 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

There's still something wrong there: It is now showing that you conducted the test at a level of 160 dB :shock: :!: :ahh: 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 -

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 -

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. :D Thanks!

Hi-- Here's a link to a second try at baseline measurements. It's not the 160 db version :oops: , 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

I tried that download page, but it started feeding me a stream of spam ads, then wanted me to create an account or something, and I got a warning from my browser, so I just closed the page. So I can't download it from there. Sorry! I'd suggest you try hosting it in a more friendly environment! - Stuart -

Oops! Sorry about that! Let's see if this Dropbox link works: https://www.dropbox.com/s/9smhvke6nhiy9 ... %20II.mdat Thanks....

Yup! That works much better! Thanks. Downloading now.... I'll take a look at it a bit later, and let you know. Stuart

Sorry about the delay! OK, the data looks fine now, and all seems to be in order. This is still the untreated room, right? Nothing in there yet except bare walls? I sure hope so.... :) - Stuart -

Yes, still untreated; let's hope it gets a lot better!!

Right! :) Because what I'm seeing on the REW results is not very pretty right now! OK, first and foremost: the data is valid, and that's great, but you need to measure the location where you have the mic for that test very, very carefully, in all three directions, so you can always get the mic back there for each new test, after you add treatment. Keep careful note of that mic position; it must go back to the precise position every time, accurate to within a couple of mm, max. So, do you have a treatment plan? - Stuart -

Hi again-- Yes, Stuart, I have a treatment plan, at least for the absorption part of the plan. I was hoping to determine slat sizes and gaps for the side wall resonators a little further down the REW testing road. Does this look OK for starters? My thought was to complete the hangers and insulation inside the soffits, re-assemble them, and then test again. Does that sound like a good idea, or should I just do all the absorption in the room (except for the cloud) before testing again? Thank you!! Mark

It's always a god idea to test the room again after each round of treatment goes in, to see what it did and what still needs to be done. It just takes a few minutes to do each test. So I would suggest testing after you do the soffits (there will be some change, but not huge), the again after the superchunks go in (that should show big changes!), then again after the cloud is in (more big changes), etc. That record of how the room is progressing can really help you decide on the final treatment. - Stuart -

Hello All-- I've been away for a bit, but I'm now working on the treatment for my soffits. I have what I hope is a quick question. My soffits are quite small, and I'm wondering about my plan to have hangers beneath the speakers. My plan all along has been to do what most everyone on this site does when they built soffits, and have hangers in the cavity below the speakers with loose insulation all around the speaker boxes along with a channel of some kind (made of chicken wire or ducting, etc) in the upper area where the loose insulation is to ensure unobstructed airflow. I would probably do a duct something like this, an image I "stole" from Simone's beautiful build thread: However, when I look at my lower cavity.... It seems to me I could only fit three hangers in there, and small ones at that. My biggest hanger would probably be 7" x 30" with two smaller ones flanking it that would be 4" x 30." So my question is this: Would it be more effective treatment-wise to approach the cavity below the speakers in the same way as the cavity above? In other words, what if I installed an airflow duct below the speaker plane that would start in the open space near the floor, and then attach that to the bottom of the speaker shelf? I would then fill the lower cavity with loose insulation in the same way as the upper cavity. Or am I better off just going with the typical hanger approach, despite the fact that they would be so small? As a reminder, my monitors are Adam A7X's. As always, thank you!! Mark

Well, I decided to go ahead and do hangers for my soffits below the speaker plane. The final dimensions of the hangers were 7" x 25" for the center hanger and 4" x 25" for the hangers that flank the center hanger. The hangers are roughly 3 1/2" thick, which was about as thick as I could make them while still being able to fit three in each soffit. Here's what the hangers looked like before installation: I used zip ties to fasten them to the cross members that they hang from. These worked great for adjusting the vertical placement precisely. Here's what they look like installed in the left soffit: ...and the right soffit: ....and here's a closeup of the left side: I hope this looks OK--they are obviously quite small, but I know there's a good reason everyone does it this way, and I'm not about to reinvent the wheel. I'm about to permanently install the speaker shelves and the speaker boxes. I will then pile loose insulation around the boxes with a channel for ventilation. FInally, I will glue and screw the lower layer (3/4" particle board) of my bezel. This is kind of the point of no return for the soffits, so if anyone has any criticisms about how things are looking, please tell me soon!!! Thanks, Mark

Sorry to do this, but I'm at a bit of a standstill so.....bump?......

Looks like they should work fine. Did you check that they do not touch the sides, back or bottom of the cavity? Can they swing freely? If you nudge one of them a little bit, and allow it to swing, do the other two start swinging a little bit as well, in sympathy? - Stuart -

Ok--time for a soffit update. I went ahead and closed up the soffits, so hopefully they look ok!! :shock:

Did you check that they do not touch the sides, back or bottom of the cavity? Can they swing freely? If you nudge one of them a little bit, and allow it to swing, do the other two start swinging a little bit as well, in sympathy?

I did make sure that all the hangers swing freely; they do not touch each other or any of the sides or bottom of the cavity. However, when I swing the center hanger, the movement on the hangers on either side is very slight, almost imperceptible. When I swing one of the smaller hangers on either side, I don't see any movement in the other hangers. I suspect this is because they are so small? If this is unacceptable, or if it means that the hangers won't do any good, I could at least stuff some fluffy insulation in there, and use the hangers to maintain an air channel of sorts for the speaker ventilation. Let me know what you think on that. Unfortunately, I'm past the point of being able to change the hangers, because the soffits are assembled, as follows: First, I finished the framing, gluing and screwing as I went: ...Then I built my ventilation channels out of chicken wire: ...then I wrapped those channels with plastic sheeting, with an opening where the vent hole will be in the bezel, to try to keep any insulation fibers from falling into my speaker boxes: I used zip ties to secure the chicken wire to the vent opening: Then I loosely stuffed rockwool scraps around the speaker boxes: Here's what they looked like before being covered up: Here's what it looks like with the "sub-bezel" installed (glued and screwed). There will be a finish layer of birch plywood over this that will follow the contours of the face of the Adam A7X. I ran tests with treatments in place, which you can get here: https://www.dropbox.com/s/j3e0egunnjb7a ... ments.mdat ...and I have to admit that I'm pretty ignorant about REW, but I'm assuming that things still don't look good. :cry: More to follow......

Just as a reminder, here is my treatment plan. I'm thinking of Roxul Soundstop in the stud bays, sandwiching the fluffy insulation which will be stacked in the triangular spaces in between. My super chunks aren't that "super"--the ones in the back of the room are 19" deep; the one on the left side of the room is about 13" deep, including the framing. I'm planning to do all of it with the exception of the cloud and then test again. Question: I remember seeing a very helpful table with different insulation products and their air flow resistivity. I should have bookmarked it, but I didn't. Does anyone have a link for that? I just want to be sure I do the best job possible with my remaining treatments. Anxiously awaiting feedback.....Thank you!! Mark

I did make sure that all the hangers swing freely; they do not touch each other or any of the sides or bottom of the cavity. However, when I swing the center hanger, the movement on the hangers on either side is very slight, almost imperceptible.

That's fine. They aren't very big, so the effect won't be very big, but as long as you see something then it shows that they are freely hanging, and somewhat in sympathetic movement.

...and I have to admit that I'm pretty ignorant about REW, but I'm assuming that things still don't look good

Well.... they ain't beautiful yet, but they sure are a lot less ugly than before! A couple of samples: The waterfall plot for your left speaker, the way it was originally (baseline): And the way it looks now: Then your baseline RT60 graph for both speakers: And the way that looks now: So yeah, I'd say that's a pretty promising improvement! :) :thu: How do you have the controls set on the rear of your speakers? - Stuart -