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PostPosted: Tue Jul 10, 2018 10:17 am 
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Location: Southern Oklahoma USA
Hello. I have been a fan of this site for a long time. Just now finally getting around to trying to set this room up properly. This is a bedroom in my parents house. Unfortunately I have found myself single and have temporarily moved back in with the parents. I'm setting up this room to be a mixing room, but it will also be the bedroom for my boys on the weekends. So I can't go all out, but think I can do something reasonable. Many years ago, before I moved out, I had made some traps and hung some proper acoustical foam. I know it's not ideal, but I did use auralex foam and not just generic stuff. Anyway the room needed some TLC and paint. So I've taken everything down and am somewhat starting from scratch. Although I do have 2 traps that are 2'x6'x4" and one that is 4'x6'x4". I will post pics once I get the paint and cleaning/organizing a bit more done.

I did also create a rough sketchup of the room. I didn't realize it was so nearly square until I measured it. It's 11'7" x 12' 11". However it has a slanted ceiling. The shorter and taller walls fall on the 11'7" walls. The shorter one is 7'6" tall and the tall wall is 9'10" tall. The closet also extends into the room. But doesn't go all the way to the ceiling. I'm still quite the sketchup novice, so I apologize for how crude it is. There is a also a window in the middle of the smallest wall, but I have a trap over it and can't quite measure it at the moment. I will add it asap. Walls and ceiling are standard drywall with texture. The floor is a wood floor with carpeting over it. I think setting up the room to where I'm looking at the short wall with the window is the best way to go, but if not please let me know.

Right now the plan is to put the traps I have on the smallest wall. The biggest covering the window, but 2" out from the wall. With the smaller traps in the corners. I have a studio desk and it looks like doing so will leave the space on the wall behind the monitors "uncovered". So I'm considering putting the smaller traps beside the big one, and then building some tube traps for the corners. I can spend whatever is needed as I save up the money, but have around $500 I could spend right now. I will also be adding at least one if not two beds and possibly a dresser. I plan on putting these on the walls to my left and right, if this is the best way to set up the room. Aside from that, the room will be empty and can add what ever is needed.

So I guess my first question is am I setting things up in a way that makes the most sense? I realize this isn't a great room and I'm not expecting anything amazing, just usable.

Second is, where is the best spot to put the monitors? I've looked at some of the room mode calculators, but the ceiling gives me trouble.

Lastly, for now, where would you put my current panels, and what should be the next thing to look at adding? I like the idea of the tube traps, but let me know if something else would be better. And I figure I'll need to build a few smaller panels to replace the foam I was using for first reflections and such. But again I'm open to any suggestions.

Thanks again. And if I forgot to add anything please let me know.


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PostPosted: Wed Jul 11, 2018 2:29 am 
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Hi Matt. Welcome! :)

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So I've taken everything down and am somewhat starting from scratch.
Then this is an excellent time to do a "baseline" acoustic analysis of your room, to see how it is performing! Here's how: viewtopic.php?f=3&t=21122

But first set up your room correctly: Speakers hard up against the short wall, where the low ceiling is, each about 36" in from the side walls, acoustic axis about 48" above the floor, mix position about 54" from that front wall, centered side to side, speakers toed in to aim at a spot about 16" behind the mix position (ie, about 70" from front wall). Speakers must go on stands, of course. Not on your desk. NEVER put speakers on the desk. The stands go behind the desk, against the wall.

Do the tests like that, with nothing else in the room.

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I did also create a rough sketchup of the room.
Great, but don't use the cheap free online toy version of SketchUp. Instead, download SketchUp Make, which is also free, and is actually usable.

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The floor is a wood floor with carpeting over it.
First critical point: get rid of hte carpet. It does the exact opposite of what you need for a small room.

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I think setting up the room to where I'm looking at the short wall with the window is the best way to go,
Right! :thu:

Quote:
Right now the plan is to put the traps I have on the smallest wall.
Well, that's a start, but nowhere near enough. It is a small room, so it will need massive treatment. I would suggest building full size SuperChunk style traps in those front corners, as well as across the top rear corner (above the closet), and down both side wall/ceiling corners. Those are the corners you have easy access to, so start with those first.

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I have a studio desk
Which one? Make? Model? Photo?

Quote:
will leave the space on the wall behind the monitors "uncovered".
You will need 4" thick OC-703 behind each speaker (between the speaker and the front wall). So the 703 goes on the front wall, then the speaker goes tight up against that, with the rear corner of the speaker almost touching the face of the 703.

Quote:
So I guess my first question is am I setting things up in a way that makes the most sense?
In addition to the above, you will need thick, deep absorption on the rear wall, but that's where your closet is! If you can't remove the closet, then at least take off the doors and fill the back part of the closet with 6" thick OC-703 or OC-701. You will probably also need something on your ceiling, above the mix position, and panels on the side walls at the first reflection points.

Quote:
Second is, where is the best spot to put the monitors?
As above: Always on stands (never on the desk, meter bridge, dob box, etc:), Stands must b sized such that the ACOUSTIC AXIS of the speaker ends up at about 48" above the floor. Speakers tight up against the front wall (except for the 4" gap for the 703). Angled inwards so both are aimed at the same spot, about 16" behind the mix position.

Quote:
I've looked at some of the room mode calculators, but the ceiling gives me trouble.
Right. Your room is not rectangular, due to the steeply angled ceiling, so room mode calculators wont give you the correct results for many of the modes. However, they WILL give you the correct results for the front-back and left-right axial modes. Those will be good. So will the tangentials in the horizontal plane, but not the other tangentials, and none of the obliques.


Proceeding as above will get you reasonable response, but not fantastic. After you have that setup complete, run another REW test and compare that with the "baseline", to see how well that worked, and what still needs to be done.



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PostPosted: Wed Jul 11, 2018 5:03 am 
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Location: Southern Oklahoma USA
You sir are fantastic. I just read the post about how to measure the room. I will order some speaker stands. Also the room has some stuff in it at the moment. It was being used as a storage room before I came back. I will get it all moved out and do some baseline measurements with the speakers where you said and report back. I greatly appreciate it. I also downloaded sketchup make. I'll see what I can do with that. I will also take some pics and post them asap. As to the desk, I'm not sure what brand. I will try to find it. I bought it at a guitar center many years ago. I'm considering something smaller, as I mostly mix these days. Any tracking I can do elsewhere. So I really just need a place to hold the keyboard, mouse, monitor, pc, and interface.

And fwiw my long term plans are to build a house with a proper tracking room and control room. Maybe even a smaller iso room or two. I plan to do it with the goal of everything being the best it can be. :) I can't wait until I get there. But until then this will surely do. And once I do move out it will make a nice room for my dad to use. He's also a musician.


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PostPosted: Fri Jul 13, 2018 6:01 am 
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Hello again. I have the go ahead to redo the flooring. So it may be a bit before I post any major updates. However I do have one more question as I'm planning my next steps. What do you think of the tube trap monitor stands? Here's a link.

Monitor Stands

Like I mentioned before, I like the idea of tube traps, but haven't used them. And since I need stands anyway, and will be delaying the project to do the floor, I'm considering building some. I've seen several videos on how to build the normal traps, but not sure if there's anything special required for stands.

My plan, if these are advisable, is to get 4 3' pieces that are large enough the speaker won't overhang the edges. Or at least not much. Then build a base out of wood that gets the speakers to the correct height. Then cut down the top piece, if necessary, so that there's a foot or less between the top and the ceiling. I'm mostly not sure of what I will need to "cap" the top of the bottom part, where the speakers go. Do I want something as thin as possible to allow sound/air/vibrations to pass through, like maybe firmly and tautly attaching the fabric I use, or would something like 1/4" thick piece of wood be better?

And if I should just buy some basic stands, I can do that also.

Lastly, as this pertains to how I make/use the stands. You say to measure with the acoustic axis of the speaker about 48" above the floor. How do I determine that? is it the center line of the tweeter? Between the two drivers? Or maybe even the center of the woofer. I have 2 sets of monitors at the moment. Some older Event 20/20BAS and some JBL LSR305's that I bought for use in a smaller room I was using for a bit. I will probably upgrade at some point, but want to get the room as "right" as possible first.

Again many many thanks.


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PostPosted: Sun Jul 22, 2018 12:03 am 
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Here are the pics. I've been trying to upload the measurements but am having issues. So decided to try the photos and keep trying with the measurements. When I get that uploaded I'll post about the progress, what I've done, and what I think I plan on doing next.


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PostPosted: Sun Jul 22, 2018 12:44 pm 
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Okay so I can't get file to upload directly to the forum. It keeps timing out I guess. I do have fairly slow internet out here. So I uploaded the file to my Dropbox. Here's the link.

So I had the room as empty as possible as you can see in the pics. I did leave the desk as it wouldn't fit through the door and I didn't feel like disassembling it. I also bought some cheap stands for now. I plan on making some tube trap style stands, the supplies just haven't arrived yet. Also when I did the measurements the mic was in the more upright position as you can see in the later pic. I took the first pics before I actually reread the "how to use REW" thread.

There are 2 sets of measurements. The first again is empty room. Then I put the traps I already had along the front wall and took the second measurements. I did center the panels but they're just leaning against the wall. I will do something better, when I figure out what the best plan would be. I will need to leave a gap between the center panel and the wall though. I had previously attached that panel flat against the wall, and when I took it down it wasn't a good thing behind there.

So obviously I need corner treatment. I believe that should be priority 1. You had suggested super chunk style traps. And I've been looking at how to make them. So will definitely build some of those for the back corners. However I also got me to thinking. What if I built square traps that are approximately 16" square instead of a triangle for the front wall. I could run them up the corners and also build one to go along the floor, on which I could set my current treatment. I could also make them the correct lengths to leave a minimal gap and then be able to access the power outlets on the front wall.

If it's a plausible idea, would it have to be semi rigid insulation? I've been looking at some other locally available options and my local Lowe's has Johns Manville R-30 insulation here. I would build a "hollow" frame, cover 3 sides with burlap, install the insulation (with backing removed and not too tightly) and then cover the last side with burlap. I would probably make them in 2-4' lengths so I could move them later if/when needed. Just thinking out loud. And I can order 703/roxul if needed.

For the back corners I will probably build the triangle style trap. I'm thinking I can even build a set for the corner with the door. When I'm not mixing I can slide them next to the closet corner and turn them into a square trap.

Then I probably need treatment at the first reflection points. How thick should it be? I would make it out of 703, unless something else is recommended. Would I need an air gap?

I could also do a "cloud" at some point.

But the next project is the speaker stands. I have ordered some pipe/tube insulation. I didn't get a tracking number, but hopefully it gets here this week. Not totally sure of my plans, but have been thinking about it. I have some ideas.

So next up is
1. Speaker stands and corner traps for all the corners. I just need to figure out how exactly I should build the front wall traps. Speaker stand only because I've ordered the stuff already.
2. Treatment at first reflection points.
3. Possible cloud treatment.
4. After this I will probably have to wait until I get some of the other furniture I plan on adding. Like a bed or beds for the boys. Possibly a bunk bed on the "left" side of the room as I look at the computer. Is that going to severely affect things? Would the same single bed on each side wall be a better idea? So as to better "balance things? Just trying to plan ahead. As it will be their bedroom some nights also. So I can't just hope the beds fit. Haha.
5. Whatever needs to be done after it's filled with bedroom stuff to make it as good as can be.

Let me know if I should do any of that in a different order. Thanks.


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PostPosted: Sun Jul 22, 2018 4:47 pm 
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Quote:
What if I built square traps that are approximately 16" square instead of a triangle for the front wall. I could run them up the corners and also build one to go along the floor, on which I could set my current treatment. I could also make them the correct lengths to leave a minimal gap and then be able to access the power outlets on the front wall.

Sure, you can do that. Just consider the footprint in the room. Can you afford to lose that much space? It seems you have the battle of bedroom vs control room. As a dad, I understand that kids are #1, always.

Quote:
If it's a plausible idea, would it have to be semi rigid insulation? I've been looking at some other locally available options and my local Lowe's has Johns Manville R-30 insulation here.

Gas flow resistivity is everything. The link you provided did not mention the necessary specification. You'd have to call JM and ask them for: Gas flow resistivity, density, and absorption coefficients.
I called Owens Corning and the only pink fluffy they had that matched the required densities for low frequencies was their Eco Touch R-24. Safe N Sound has decent specs in terms of absorption coefficients in low frequencies and it's not super expensive. Where I live, 703 is SUPER SUPER SUPER expensive.

Quote:
Then I probably need treatment at the first reflection points. How thick should it be? I would make it out of 703, unless something else is recommended. Would I need an air gap?

It needs to be at least 4" thick. An easy and cheap way to frame them up would be out of dimensional 1x6 lumber. A 4" batt of insulation would then leave your batt 1.5" off the wall. This is the perfect dimension to put a few 1x2 lengths of lumber on edge acting like ribs to prevent the insulation from getting pushed in against the wall if anyone leans against it. Also, the 1.5" lip works for hanging the panel off of screws in the wall studs.

Quote:
I could also do a "cloud" at some point.

Did I mention that kids are #1? That's awesome that your parents are letting you go as far as ruining their stippled (presumably) ceiling. If you can believe it, my in laws let me take over half their basement for my temporary studio. I built a booth and everything hahaha.

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4. After this I will probably have to wait until I get some of the other furniture I plan on adding. Like a bed or beds for the boys. Possibly a bunk bed on the "left" side of the room as I look at the computer. Is that going to severely affect things? Would the same single bed on each side wall be a better idea? So as to better "balance things? Just trying to plan ahead. As it will be their bedroom some nights also. So I can't just hope the beds fit. Haha.

In front of your ears, your room needs to be perfectly symmetrical. After that, it's less important, but a good idea to try and keep things even if possible.

Greg

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PostPosted: Tue Jul 24, 2018 11:36 pm 
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Thanks for the tip on safe n sound. Looks like it’s available in 16” wide pieces pretty sure I can source it locally.. That’ll work perfect. And as far as losing space, it’ll mostly move my desk back. But also give me a place to set my speaker stands. Plus I’m considering a smaller desk as it is. Anyway it might take me a week or two but when I get them done I’ll remeasure and post results. :)


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PostPosted: Wed Jul 25, 2018 12:09 pm 
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Okay. So the tubes for the speaker stands showed up today. :). However the Safe n Sound isn't being as easy to track down, but upon further searching I have found Owens Corning Thermafiber Fire and Sound Guard Mineral wool available within driving distance. From What I can tell it's very similar to 703. They even publish the specs here. It's 15"x47"x3". So I'm thinking of stacking 5 sheets per box. With a minimal wooden frame around them so they're close to 16"x16"x48". Well from my rough drawings there will be 3 boxes this size. Two slightly shorter at 42" and 44". But then I'll also need a 24" and 26" box.

However this leads my next question. I have two outlets on the wall I'm facing. One is 16" from the outside wall the other is 24". So I'm thinking of just doing the corner with the 16" spacing with two boxes vertically, one would be 48" and the other 42" tall. But on the side with the 24" spacing, I'm thinking of doing a 24" box horizontally and then stacking a 48" box and then the 26" box on top of it. Would that lack of symmetry be problematic? I still plan on putting two boxes between the outlets. A 48" and 44".

If that will work I will pick it up in the next day or two, and start building frames. Then I'll still need to figure out the back corner super chunk traps. I could do something similar back there, or drive a little further and pick up some 703 or similar. Still thinking on those.

For kicks I did stack the pipe insulation in the corners and did some listening. The room is getting better and better. Thanks for the help. :)


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PostPosted: Thu Jul 26, 2018 1:57 am 
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A little late on replying, but rather busy on other stuff. Anyway...

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What do you think of the tube trap monitor stands? Here's a link.
I looked at the link, but did not see any actual acoustic measurement data showing laboratory tests of that device, so it's impossible to know how it actually works in real life. I have a hard time believing that it will do much for floor-bounce, as claimed in that link, although I can see it having a mild effect on some modal issues.

Quote:
I've seen several videos on how to build the normal traps, but not sure if there's anything special required for stands.
For normal stands, the key is mass. Lots of it. They need to be very heavy. But the ones you linked to seem to be based on a different principle, so as long as there is no mechanical connection through the stand to the floor (only through the insulation), then that might work. But once again, you'd need actual measurements of the device in a laboratory to make sure it is not transferring sound and vibration to the floor, and also not allowing the speaker to move excessively through vibration while in use.

I'm always skeptical of product where there are claims of spectacular performance but no actual data to back it up. You'd think that if the product really did work as advertised, they would be proud to show the results of acoustical testing in a laboratory setting, as part of the marketing. . .


Quote:
You say to measure with the acoustic axis of the speaker about 48" above the floor. How do I determine that? is it the center line of the tweeter?
The manufacturer of your speaker should show this, either in the manual or on their website, r should provide that info if you ask for it. For example, here's how Genelec presents that information, for all of their speakers: https://www.genelec.com/documents/other ... xis_US.pdf Other manufacturers do something similar. If you cannot find this info for your speakers, that would not be a good sign about the manufacturer... Either they don't know because they never bothered measuring, or they do know but don't want to publish it... either way, not a good sign.

However, if you can't find that info for your speakers, and you can't afford to upgrade them just yet, then you can estimate: for a typical two-way studio monitor, the acoustic axis will be on an imaginary line joining the center of the woofer to the center of the tweeter, and much closer to the tweeter. In some cases it might be right on the tweeter, but in most cases it is away from the tweeter. If you pick a spot about two-thirds to three-quarters of the distance from the woofer center to the tweeter center, you should be close. For three-way speakers, it's a bit more complex, but you can usually use a line between the center of the mid-range driver and the center of the tweeter, and once again about two-thirds to three-quarters of the distance along that line.

Quote:
Or maybe even the center of the woofer.
For studio monitors, it wont ever be at the woofer. Only for subs, and even then, "acoustic axis" is not really applicable to subs, as they are pretty much omnidirectional sources. There isn't really one single point on a sub where all the sound seems to come from: it's more like sound is emanating from the entire box at once.

Quote:
I've been trying to upload the measurements but am having issues.
Upload them to a file-sharing service such as DropBox, then post the link here.
Quote:
So I uploaded the file to my Dropbox.
:thu: I'll take a look at this when I have a chance, and get back to you.

Quote:
So I had the room as empty as possible as you can see in the pics. I did leave the desk as it wouldn't fit through the door and I didn't feel like disassembling it
That's fine.

Quote:
I will need to leave a gap between the center panel and the wall though. I had previously attached that panel flat against the wall, and when I took it down it wasn't a good thing behind there.
You might not need that panel there at all, actually. It might be put to better use elsewhere.

Quote:
So obviously I need corner treatment. I believe that should be priority 1.
:thu:

Quote:
However I also got me to thinking. What if I built square traps that are approximately 16" square instead of a triangle for the front wall.
You could, but they will stick out a lot into the room, taking up useful space, and 16" is rather small for superchunks anyway. 24" is better, and 36" is better still. Making the triangular means that they don't stick out too far into the room, and uses less material. They are very effective down to low frequencies.

Quote:
If it's a plausible idea, would it have to be semi rigid insulation?
If you try to stack triangles of "pink fluffy" insulation 8 feet high, you'll find that firstly it is very hard to cut that accurately, and secondly it won't want to stack very well at all! OC-703 and similar semi-rigid products can be cut easily with a bread-knife, and also stacks quite well:

Attachment:
superchunks-01 -ENH.SML.jpg


Even for very tall traps with high ceilings, you only need minimal framing to keep it in place.

Attachment:
BUILD-17th-construction-superchunks-vert-an-horiz--2013-10-11-photo 2-ENH-SML.JPG


If you use something other than 703, then do make sure that it has the same or similar characteristics.

Quote:
Then I probably need treatment at the first reflection points. How thick should it be?
At least 4". 6" is better, if you can afford the space.

Quote:
Would I need an air gap?
4" with a 4" air gap works very well, but it does mean that it sticks out a long way into the room. If you wanted to, you could angle the edges, so it is thinner at the left and right sides of the panel, then full thickness in the middle. A little more aesthetic like that, and acoustically valid as well. Just not so easy to build...

Quote:
I could also do a "cloud" at some point.
Very likely that would be needed.

Quote:
Possibly a bunk bed on the "left" side of the room as I look at the computer. Is that going to severely affect things?
Keep the room as symmetrical as you possibly can. You want to ensure that your left ear "sees" the same acoustic signature as your right ear, so you don't end up inadvertently skewing things in the mix, trying to compensate subconsciously for the imbalance. Maybe consider having "fold-down" beds that lift up to be flat against the wall when not in use, then fold down flat when needed? One on each side.

- Stuart -


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PostPosted: Thu Jul 26, 2018 2:11 am 
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I just took a quick look at the REW data, but it seems like you didn't follow the instructions, here: viewtopic.php?f=3&t=21122 You did all the measurements about 12 dB too low, and there's no "LR" data, so there's not much I can do with that. Sorry. The only thing I did notice is a huge difference between the left and right speakers. In the low end, there's a difference of over 35 dB between them! Even in the mid range they vary by as much as 10 to 15 dB. Are you sure they are matched too each other, adjusted identically, and positioned at exact mirror-image locations in the room? And that the front half of the room is symmetrical?


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PostPosted: Thu Jul 26, 2018 5:42 am 
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Thanks for taking the time to look at my measurements. Not sure what step I might have missed, or didn't do properly, but that was the page I had open, going step by step. I will reread and remeasure. I used a Presonus PRM-1 mic, and had the pink noise right at 80 db c-weighted slow response out of each speaker. I used my Sper Scientific Sound Meter.

I measured the placement of the speakers and adjusted multiple times. The front center of the speaker was within an 1/16" of an inch from 36" from the outside walls. There was a 4" gap behind the speakers for the treatment to be placed later. I wasn't sure about the acoustic center so I used the center of the tweeter, and had them both 48" above the floor. I would measure, adjust, measure, adjust, etc until I got them as perfectly placed as possible. That said they weren't the most robust stands, and I had to do that a lot until I felt confident they were as close as possible.

Just to recap from my memory, I measured each speaker separately. I used the monitor level on my interface (a Focusrite 6i6) to set the quietest speaker to as close to 80 dB as possible. Which for me the right side. Then I adjusted the input trim on the back of the left speaker so that both were reading within .1-.2 dB of each other. I went back and forth several times. Always holding the tip of the meter directly above the tip of the measurement mic. I made sure and had the mic equidistant from the monitors. Also the difference in volume was .5-.6 dB. So it didn't take much trimming to get it in line. And it sounds relatively balanced to me. Not that I'm any expert. But I would think 10-15 dB would be quite apparent.

Maybe my meter is off. I have the calibrator for it also. I've had it for years, but rarely use it. I also volunteer with the sound at my church and bought it to be able to measure how loud the services were. From the reviews I thought it was a decent one, and cost around $125 when I bought it. I can get another if that is possibly part of the problem.

In retrospect I think I see what I did wrong. When I checked levels right before the test I got the "levels too loud message". I adjusted the mic gain down, but I don't think I went back to step 3 and redid everything.

So I'm sure it was somehow user error on my part. And I had noticed some difference in the measurements, but am not familiar enough to realize they were that far off. I had assumed it might have something to do with the closet in the back corner of the room messing with things.

When I get a chance I'll remeasure. I'll also hold off on buying the stuff for the super chunk traps. I had come up with the 16" dimension from several of the DIY's where they had take a 24"x48" piece of 703, cut in half to 24"x24", and then cut those in an x pattern with a 24" front face. Which gives them a depth of around 17". Then when I measured the 16"+ gap between my current treatment and the wall I figured a 16" cube would maybe be even a bit better. But looking at the pics you linked, I'm guessing they cut the 24" square piece diagonally, giving a front width of about 34" if my math is correct. So obviously much larger than my plan. But if I could eliminate that large middle piece, that would be helpful.

Okay back to the measuring an drawing boards. Thanks again.


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PostPosted: Thu Jul 26, 2018 7:17 am 
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Quote:
I used a Presonus PRM-1 mic,
:thu: That's what I use most of the time. Good choice!

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and had the pink noise right at 80 db c-weighted slow response out of each speaker. I used my Sper Scientific Sound Meter.
And you calibrated REW to that level, using the "SPL Meter" and "Calibrate" button?

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I wasn't sure about the acoustic center so I used the center of the tweeter, and had them both 48" above the floor.
That's fine. It won't affect the levels or the readings much.

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So it didn't take much trimming to get it in line. And it sounds relatively balanced to me. Not that I'm any expert. But I would think 10-15 dB would be quite apparent.
Here's the actual graph of the DIFFERENCE between the two speakers. The "0" line shows the level where they exactly the same. Wherever the curve is above that 0-line, the left speaker is louder, and wherever the curve is below the line, the right speaker is louder:
Attachment:
MattE--Baseline--LR--Difference--18-22k.png


As you can see, there are wild swings in the low end: at 94Hz the curve drops to -16dB, then at 115 HZ it shoots up to +23dB That's a huge difference, so something is definitely out of whack there. You can see similar issues in the lower mid range, from about 200Hz up to about 1k. It's a little better above that, but still not good.

Something similar happens with phase, but I didn't put it on this graph, for clarity.

What speakers are those? Make and model.
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Maybe my meter is off. I have the calibrator for it also.
Perhaps, but it would only be by 1 or 2 dB, if that. It certainly won't be 15 dB! But it's woeth calibrating, especially if you haven't' done so in years. I try to calibrate mine every few months. They are rarely off by more than a small fraction, but it's always good to know that your gear is in spec.

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From the reviews I thought it was a decent one, and cost around $125 when I bought it. I can get another if that is possibly part of the problem.
It's probably fine. But calibrate it again, just to be sure.

That said, I doubt that your meter is the problem. I'd suspect that you made a mistake some place in the procedure, and maybe adjusted something after you had already calibrated.

After you have the system calibrated, NEVER TOUCH IT AGAIN! All of the controls must stay at exactly those positions until you are completely finished tuning the room. Mark those positions, make notes, take photos, etc. If you accidentally bump something, you need to be able to get back to that exact same identical setup, every single time.

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And I had noticed some difference in the measurements, but am not familiar enough to realize they were that far off.
You should see most of the curve running at around 80 dB average, with ups and downs, of course, but there should be peaks and valleys on either side of that, across the board. Usually the swings are far more noticeable in the low end. Another way to check is to select 1/3rd octave smoothing for the curve, and look at it like that.

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I had assumed it might have something to do with the closet in the back corner of the room messing with things.
Possibly, but I doubt it. That should affect both speakers more or less equally, but in your case there are large differences between the speakers.

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But looking at the pics you linked, I'm guessing they cut the 24" square piece diagonally,
Right! If you have enough space to do that, then go as big as you can. It's also not necessary to have the triangle as a right-angled isosceles: the two sides do not have ot be the same length. So one could be 28" and the other only 20", for example, if that would help to fit it next to a doorway or window.

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But if I could eliminate that large middle piece, that would be helpful.
Once you get your REW issues sorted out, then do one set of tests WITH that panel in place, and one WITHOUT it in place, to see what type of difference it is making.


- Stuart -


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PostPosted: Thu Jul 26, 2018 9:21 am 
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I can't explain how much I appreciate your help. Like I said I'm pretty sure a big part was me adjusting the mic gain. However I think it should be the same for all the measurements I took. I will look closer at the results next time.

And the speakers I'm using right now are JBL LSR305X. The x was a special edition run for massdrop. They are suppose to be calibrated at the factory to within 1 dB of each other. I also have an older set of Event 20/20bas I could use. I haven't used them in ages. Mostly because I went for years without a room to mix in. Then when I finally had a small space the 20/20's were overkill. So I saw the 305's, heard some good things (for the price), and went with them. I've always wanted something like the Adam's A7's with the ribbon tweeter. They've sounded quite nice the few times I've had a chance to hear them. And I do plan on eventually getting something better. Just wanted to get the room as close as possible first. So that I can really appreciate what the new ones have to offer. Whatever it is I choose. And feel free to make suggestions. Obviously budget matters, but I'm at the point where I'm willing to take the time to save up for the "good stuff".

FWIW I just upgraded my Metric Halo ULN2 to 3D specs. I've waited a while for this upgrade to become available. Mostly because it adds Windows support. I didn't use it for the first measurements, because I can't access any of the internal settings. That said I will try to use it next time. Because it has indents on the gain knob, and then a second trim knob that is defeatable. I will use it so that I can guarantee the gain is at the exact setting for every measurement going forward. Hopefully it will help provide consistent repeatable measurements. Because this project could take a couple of months to get totally sorted. Especially since I'll now be trying to find a source for treatment material. Again. Haha.

And once I get some good measurements. And am able to repeat them. I will test with and without the center panel. See what it's doing. I might even try to test the stands I'm planning on making. See if they make any measurable difference. They should at the least be a bit more stable than the ones I have now. Not that they're horrible, but they do have more movement than I would like.

It will probably be Monday before I can do any more tests. Since I'll need to empty the room again. Thanks again.


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PostPosted: Thu Jul 26, 2018 11:02 am 
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Quote:
I can't explain how much I appreciate your help.
:thu:

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Like I said I'm pretty sure a big part was me adjusting the mic gain.
That could explain the overall level being off, but it doesn't explain the differences between the two channels.

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And the speakers I'm using right now are JBL LSR305X.
Those should be fine. There's no way that they could be that far different from each other, unless one of them is damaged in some way. So the L-R difference is even more of a mystery!

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I also have an older set of Event 20/20bas I could use.
Here's an idea: Get those out, blow the dust off, and do a REW test with them, instead of the JBLs, just to see if we are still getting a huge L-R difference. If there's a similar difference with those speakers, then clearly the problem is some other place, not the speakers, and you can carry on with either the Events or the JBLs for the rest of the testing. But if the problem changes substantially in some way, then that would prove that one of your JBLs is damaged. This is a fairly easy test to do, and will tell you a lot about the speakers and the room, s when you have a chance, it's definitely worthwhile doing!

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I've always wanted something like the Adam's A7's with the ribbon tweeter.
I have a pair of those, and I do like them. They are a little light on the low end, so I added an Adam Sub-8, and that helps to fill in. I probably should have gone for the Sub-10, as the Sub-8 doesn't seem to pack enough punch sometimes. But yeah, Adam speakers are pretty nice. There's another option that you should look at too, when you are ready: Eve Audio. Some of the original engineers from Adam left the company to start their own, and called it "Eve". (Adam and Eve? Get it? :roll: ). They use similar ribbon tweeters in their designs, and they are great. I used a pair of their Eve SC-407's when we re-did this room a while back: viewtopic.php?f=2&t=20471 I originally designed that room for the older speakers they had in there (Genelecs), but soon after we finished, one of the old speakers went flaky, so Rod decided to upgrade his speakers and re-tune the room to match them. We looked around, and settled on the SC-407's, even though I wanted them mounted in a way that they were not supposed to be. But I spoke to the head engineer at Eve, explained the issue, and got his blessing. Great folks there at Eve. Easy to work with. You can see the results in that thread, and also on Rod's website. So take a look at the Eve Audio product lineup when the time comes for you to make a decision. They are similar to Adam's in many ways, but the Eve's have advantages that I really like. Such as all the controls are on the front panel, not the rear panel, so you can tune them even when soffit mounted! And the sound spectacular.

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Because this project could take a couple of months to get totally sorted.
You are a real optimist, aren't you! :) I'd bet good money that you won't be finished until well after "a couple of months" . . . Once you get started on the treatment, and begin to hear the difference, you'll probably want to carry on a bit more... and a bit more still... and then another bit more...

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I will test with and without the center panel. See what it's doing.
Also test with it on the back wall of the closet, and again with it spaced away from that wall quite a bit, maybe a foot or so away form the wall. You might be surprised...

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I might even try to test the stands I'm planning on making. See if they make any measurable difference. They should at the least be a bit more stable than the ones I have now.
One of the keys to good stands (and good speaker mounting in general) is mass. Another is rigidity. You want your speakers to be set very firmly, on something very massive that cannot move. Some people just stack up bricks or concrete blocks, then wrap that in insulation and fabric. Others use hollow steel stands, filled with sand or concrete. If you wanted to do the tube-trap thing, you could start with a large diameter hollow steel tube of some sort, make a very sturdy base for it, and some type of adjustable height platform on the top, then fill it with concrete, and wrap the pipe with your layers of wire mesh, insulation and fabric (depending on which design you are following).

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It will probably be Monday before I can do any more tests. Since I'll need to empty the room again. Thanks again.
:thu:



- Stuart -

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