John Sayers' Recording Studio Design Forum Archive

Here are the measurements I was able to do today. I wasn't able to clear out the room. Plus I want to work on my measurement technique, and make sure I can get it repeatable enough to be worthwhile. So all I did was swap out the JBLs for the Events. Measured and set everything up to the specs. With the exception of, these speaker stands aren't cutting it. The baseplate can "tilt", but not just front to back, but in any direction. So that could have been a bit of an issue with the JBL's, and it definitely made getting them matched very difficult with the much bigger and heavier Events. But I did my absolute best. But I will build/get better stands before I try and do any more serious measurements.

That said I did look at the results a bit closer this time. I noticed the R measurement had these were dips all the way through the spectrum. So remeasured and labeled it number 2. There is still some noticeable inconsistencies in the low end. Maybe not as bad as the JBL's but still there. I tried comparing my original test to the new ones and see if there was a correlation, but I'm just not sure. This house has a wood floor and is setting on cinder blocks. Could it be a matter of the cheap stands and a possible resonant floor fighting me? The room is in a corner of the house. Just trying to figure out what is going on. And maybe I'm still not being accurate enough with my measurements. Partly due to the stands.

I have some ideas on how to build the stands. But I'm tempted to just go get some cinder blocks and stack them up for now. We may have enough around here. Again I appreciate the time and effort you guys are graciously putting into helping me.

And on a sidenote. Being without a room I could dedicate to mixing for so long, I did some work with headphones. Obviously not ideal, but eventually got to where I could make it work. Sonarworks headphone calibration plug in helps. But I recently found out about Goodhertz Canopener plug in. I had read were people were using it with Sonarworks. Can't say exactly what it does, but I know it's some sort of crossfeed processor. I use the "lifelike" preset, which seems to be somewhat subtle, but eye opening at the same time. Using the Sonarworks to help with the frequency response, and CanOpener doing whatever it does,really is quite good. Make no mistake I'm going to get this room as good as I can. But I have found a fall back option until then.

Oh and I looked at those Eve monitors. I will have some. Someday. My long term plan is to build a house with a proper mixing room, and at least a nice live room that a 6+ person band can fit in. Ideally I would like that room to be able to double as a home theater room. Anyway point being, when I get to that point I am not going to skimp. I will take my time and make sure everything is as good as it can be. And if I need to wait and save up a bit to get those Eve monitors. That's exactly what I will do. Along with hiring someone, that knows what they're doing, to make sure it's all done right. but until then, back to this room.

Let me know your thoughts and what I should do next. Thanks.

I noticed the R measurement had these were dips all the way through the spectrum. So remeasured and labeled it number 2.

Yup! That first one was very strange: some type of weird comb-filtering going on there, as though you had a highly reflective surface close to the speaker. Or perhaps some type of feedback path through your sound system. But either way, it's no use, so I dropped that one, and use the "dirty-2" version instead.

OK, so, here's the issue: Your levels are still too low! That's the full spectrum graph, from 20 Hz to 20 kHz, with 1/3 octave smoothing. Red trace is left, right is green, both together is blue. As you can see, both the red and the green barely even touch 80 dB, yet 80 dB is supposed to be the AVERAGE level, with peaks and dips above and below. Ditto for the blue curve: it should be varying around the 96 dB level, but it hardly even touches that anywhere. As best as I can tell, all of your levels are about 4 or 5 dB too low. I can't say why: it could be any of several reasons, but they all relate to calibration. Are you absolutely certain that you "SPL Meter" button at the TOP of the REW main window, played pink noise at 80 dBC SHOWN ON YOUR HAND-HELD METER, then clicked on the "Calibrate" button on the REW SPL meter, selected "Use REW speaker cal signal" from the pop-up box, clicked "OK", then typed in the level "80.0" in the "SPL Reading Calibration" text box, and clicked "Finished"? 100 % certain? Those two levels MUST match! And you must have both meters set to "C" weighting and "Slow"? That's the only thing I can think of that went wrong.... you made a mistake at this point. Maybe you had one meter set to "A" and he other to "C", or you mistyped the number, or some such.

The next strange thing I noticed is that both your JBL and also your Events have a serious roll-off in the high end, and it is very similar. You can see on the graph above that above about 10 kHz, everything takes a noise-dive, and drops about 10 dB over the top octave. It's not the speakers, because roughly the same thing happens with both sets. It's not your soundcard, because the calibration file shows typical almost flat response for that. I doubt that it is the room either, since I can't see how it could do that, to such an extent. I would suspect something else in your signal chain... maybe something in your computer operating system is applying filters to your sound path? Maybe a mic pre? Console? Settings on the speakers themselves? Faulty measurement mic?

OK, now on to the left vs. right issue: The problem is NOT your speakers, since both the JBL and Events show pretty similar results. Here's the two traces for just the right channel (I adjusted the levels manually, to get them in the same ballpark) The light green trace is your JBL right speaker, and the dark green trace is your Event right speaker. Both are smoothed to 1/24th octave. It's pretty clear that they both show the same general response curve, with that huge dip in roughly the same place and roughly the same level, between aprox. 100 Hz and 150 Hz.

And here's the same comparison for your left side: It's not quite so clear here, but you can still see that the general shape of the curves is about the same.

So your speakers are good. That means it is either a channel problem (something else in the signal chain is altering the signal: not likely), or the room. It seems to me that the only choice here is that the room is somehow very different acoustically when viewed from the left and right speakers.

I tried comparing my original test to the new ones and see if there was a correlation, but I'm just not sure.

There is. See above.

Could it be a matter of the cheap stands and a possible resonant floor fighting me?

Possible, but I'm not convinced. However, it is certainly worth trying different stands, just to see if anything changes. If you have the time and inclination, then by all means stack up some cinder blocks instead of those stands, and do a test. You don't need to be accurate down to the millimeter here! The problems are so large that even a rough approach will show if the stands are an issue or not.

And maybe I'm still not being accurate enough with my measurements.

I don't think your measurements are at fault! This is way too big to be due to you not setting the speakers or mic exactly. This is very substantial changes, so it's almost certainly not to do with your measurement or setting up skills.

Is there anything else that is noticeably different on the left and right sides of the room, as you stand there and look around? Something prominent that is off-balance, such that the left and right sides of the room are not mirror-images in some way?

One final graph: here are two curves showing the DIFFERENCE between the left and right speakers in both cases: The red curve is your JBL speakers, and the light blue curve is your Event 2020's. As you can see, here too the general shapes of he two curves is similar, thus implying that the Left/Right channel imbalance is NOT due to the speakers themselves, but something else.


- Stuart -

Okay. Not sure about the levels again. I went through the entire process with the page open while setting things up. I just reread it and I can't see a step I missed. I even remember getting the message about "the maximum spl with this calibration". It was something like 109 dB.

So I feel better about the speaker situation. Although it leads to more problems. The only big difference is the closet in the back left of the room. I will measure around and make sure everything else is relatively symmetrical. From what measuring I've done for building acoustic panels, and to make the sketch draft, everything seems to match up.

I'm not expert, so I could be way off base, but I think it may be a construction issue, like the resonant floor idea. But again just guessing and could be entirely wrong. My bedroom is a mirror of that room, with the closet in what would back the back right, if I set them up the same way. I may stick some speakers and a mic in there and see what happens. I could potentially do that tonight. But don't hold your breathe haha.

Other than that, I'm not sure. I will get some blocks and make some stands also. See if that changes anything.

As far as the one weird test, I'm really not sure what happened. I just looked at the results and saw how strange they were and retested. Without touching anything. So I'm guessing a glitch in the matrix.

Regarding other issues. Not sure about the 10k fall off. Possible a defective mic. I might try another mic I have and just see if the roll off is still there. Can't really see it being something in the digital side of the chain chain. I did the loopback for the soundcard calibration with a standard 1/4 trs cable. This interface has combo trs/xlr inputs. So I guess it could be the mic pre. But I would be more apt to guess the mic is faulty. But at this point who knows. Maybe this room just doesn't want to be used to mix in. Would be my luck. I do share a first name with Charlie Brown haha.

So I guess the next step is to figure out what is going wrong. I'm going to try and eliminate the mic next. I have access to some SDC's I could use. But i do have some Cad M179's. From the looks of the specs in omni mode they have a bump from 10kz-20khz. So it won't be useful as a measurement, but at least if it falls off we know it's probably a room problem and not a mic problem. At least to me that makes sense.

Again many many thanks.

Okay so I finally got to set up some cinder blocks for stands. I didn't totally empty the room, but did remove the 703 panels. I went through the calibration process again. However it still shows my levels as just barely hitting 80dB and I'm not sure what to do about that? Beginning to wonder if a faulty mic might be at play? I'm going to load up some pics of the room as I measured it. Mic is centered in the room (69 3/8" from each wall), 54" back from the front wall. A marked a spot in the center along the top edge of each speaker for a horizontal axis that is 36" from the wall, with a 4" gap, putting that point 16 3/4" from the front wall. So as far as I can tell I have it all as centered and balanced as I can. But the blocks didn't seem to do much as far as the differing responses. Also I tested the output level with my meter with both speakers on. It is around 85dB. You mentioned that the level for the both speaker test should be around 96dB. So I'm definitely doing something wrong or have something broken. Or have misunderstood. Also if it's not a bad mic, could the difference in response be causing the meter to not have an accurate reading of the level? and that be the level issue?

Also just for kicks after I realized the sides were still pretty different, I measured each side 4 more times. Just to make sure the results were at least repeatable. And from what I can tell I got the same results everytime.

Measurements

And here are the pics as promised.

Okay so I may be getting somewhere. I don't know exactly how or why, but I remeasured the speakers. And somehow my right one was 37" and not 36" from the wall. I also realized, although I had recalibrated my dB meter, it had an old battery. So I replaced the battery, recalibrated the meter, double checked everything else, including going through all of the REW calibration steps, and took some measurements. To me they look much closer to what I think you're expecting. There's still some variation from side to side in the lows, but it's not near as drastic. At least to my untrained eyes. They're at least not going up where the other is going down. Admittedly the room isn't empty. I have the big panel leaned up against the corner of the closet right now, and the pieces of pipe insulation are set up in the corners. So maybe that's helping. I'm not touching anything else in here until I know these measurements are at least in the right range. If so I will clean everything else out of the room, without touching the speakers and mic, and remeasure with it empty for a baseline.

Let me know how these look. Thanks in advance.

Measurements

It’s been a while. I’m still working on the room. Today I bought some 4” Rockwool to put in the front corners. Superchunk style. I’ll post pics soon. Anyway I had planned on using 2 pieces for first reflection points. And I thought I had found a company that makes a “bag” that you could put the insulation in. If I remember it came with 4 plastic pieces for the corners to provide some support. I’ve been searching but can’t seem to find them. Does anybody else know what I’m talking about? Did I imagine these? If I made it up I’ll build some frames. Thanks.

Another quick update. I bought two packs of rockwool. 8# 4" thick panels. I've cut up 4 of the 6 sheets and put them in the corners. The other 2 are waiting on me to build some frames for first reflection point panels. I had already taken apart another trap I had built using 2" 703 and cut it up into triangles. With this new rockwool I'm not to the ceiling, but at least it's taller than the speakers now. I'm just now sitting down to listen and yes there is a definite improvement in the low mids and lows. Due to me placing the insulation I may have moved things a bit here or there. So hopefully Monday I can get out the tape measure and make sure everything is where it is suppose to be. Then I'll do some measurements. That is if I don't go buy some more of this stuff. Anyway enough

I'm just now sitting down to listen and yes there is a definite improvement in the low mids and lows.

Yup! Bass traps work! That's pie in the eye for those silly folks who still insist that porous absorption does not work at all below 200 Hz...

That is if I don't go buy some more of this stuff.

Another truckload should do it!


- Stuart -

Soundman2020 wrote:

I'm just now sitting down to listen and yes there is a definite improvement in the low mids and lows.

Yup! Bass traps work! That's pie in the eye for those silly folks who still insist that porous absorption does not work at all below 200 Hz...

That is if I don't go buy some more of this stuff.

Another truckload should do it!


- Stuart -

There is no doubt the bass is tighter and more defined. It's got me excited and wanting to do more.

So I've been playing around with getting everything setup to take more measurements, and so I know exactly where I need the first reflection side panels. Which I still need to build. But in doing so I realize I should upgrade my speaker stand situation first. Seems as all the other things pretty much revolve around that. I've been using cinder blocks stacked up. Heavy for sure, but a little too high, not exactly stable (they're just sitting on each other), and I think maybe tend to lean a bit. I know the objective is heavy and decoupled.

So I've ordered some IsolateIT bumpers for the speakers. They have a page that tells you what bumpers depending on what your speakers weigh. https://www.isolateit.com/speaker-decoupling I ordered a set for my speakers. So I have that going for decoupling. As long as these will work? I know I've read about people using sorbothane, and the recommendation always is to make sure you're using the right amount to get the correct compression.

So now I need to figure out a stand design. I'm leaning towards a PVC filled with sand design. I'm even thinking about getting some weight plates, liked used for weightlifting, to use as bases. I'm thinking of using 25lb (approx 10kg) plates. Then bolting a piece of plywood to the top of that. 1/2" or 3/4". Then a 4" PVC pipe flange attached to the plywood. The length of PVC necessary to get my speakers to the correct height, filled with sand. Another flange and another piece of plywood for the top. I'm just thinking the weight will make it more bottom heavy and stable. Am I overthinking it? They're going to be roughly 36"-38" inches tall. I just want to make sure the CG of them is low, before putting my 30 lb speakers on top.

Let me know what you guys think.

I've been using cinder blocks stacked up. Heavy for sure, but a little too high, not exactly stable (they're just sitting on each other)

You could build a base out of wood and fill it with sand or if you have the tools, make a solid wood base and then glue the blocks together and also glue them to the base. That would get you exact height, weight and it'll be sturdy. Seems easier than your PVC design.

Greg

Gregwor wrote:

I've been using cinder blocks stacked up. Heavy for sure, but a little too high, not exactly stable (they're just sitting on each other)

You could build a base out of wood and fill it with sand or if you have the tools, make a solid wood base and then glue the blocks together and also glue them to the base. That would get you exact height, weight and it'll be sturdy. Seems easier than your PVC design.

Greg

That’s a pretty cool idea. I’ll think on it. And I guess “ease” is relative to your comfort of working with said materials. I’m fairly comfortable with anything. Part of my reasoning for the weight was it being round. So I can turn the top to the correct angle and still be close to the wall. But I went by my local home improvement store to get some ideas. And found they have flanges with steel rings that can be rotated. So I can use these on top to allow the bottoms to be flush with the wall and the top still rotate to the correct angle. I plan on finding the balance point of the speaker and centering it directly over the center of the stand. And making the top plate the same size as the speaker. If I change speakers it will simply be a matter of making a new top plate that matches those speakers.

And I still may do the weight thing. It’s not an issue for me to drill and tap 4 holes. In fact upon more thinking I could actually skip the wood between the flange and weight, as I found flanges that we’re sealed off in the end. So I could attach those directly to the weight. That said your box idea is still very valid. And I could buy the parts locally any time I wish. I’d have to order the weight. Unless some pop up on a local market place. Decisions decisions. Again thanks for the ideas.

Okay so I still haven't decided on a stand design. Heck I've made frames, but haven't finished my first reflection traps for the side walls. Hopefully I'll knock those out later today. I did how ever get the sorbothane hemispheres. So I took my time and got my speakers as close to perfectly positioned as I can. I even got a laser level to help make sure they are pointed exactly at the spot recommended. Such little things again added a noticeable improvement. No doubt repositioning the speakers probably helped. But transparency, depth, and width of sound stage are definitely improving. I'm excited to get the side panels up. Then I'm going to sit down and see how much more insualtion I need for the back corner(s). Then hopefully soon take some measurements. See what my ears are telling me.

So here's my next questions. Obviously getting some measurements will no doubt help going forward. But of the 3 corners I have left, There's really only one in which I can put a full super chunk. It's the corner by the door into the room, between the back wall and closet. I could put one in the other corner between the side wall and closet, but I'll have to cut it down. The door is too close to get a full triangle in there. I want to say I have 14"-16" between the door and wall. There is no way to use any kind of stationary chunk style treatment by the entrance door. It is right up against the wall.

So here's my thoughts. It's obvious the round insulation tubes I have weren't doing anywhere near enough for bass. But what if I filled them with some other insulation. I know in my research I found one recommendation for some of the "fluffy" insulation that had actually been measured to actually be effective. Admittedly I don't remember how low it went. But I'm thinking of filling these tubes with that to give it more "depth". Then I could also easily move them out of the way when needed. I have 4 tubes. So I could put two in each of these corners. Obviously the best thing to do is to try and then measure. Just wondering if anyone thinks I'm simply wasting my time and money, and has a better idea.

Also being a small room, I figure treating the first reflection points on the rear wall will also help. I used the laser level and marked where on the back wall they're directly aimed. One is behind said entrance door, the other is on the closet door. So my thoughts, if measurements say they're needed, is to build as thick of a panel as I can and hang behind the entrance door. Then make another and hang it on the closet door. I would probably make it 4" if possible.

Then maybe a cloud. Although with the ceiling slanted like it is, I'm wondering how necessary it is.

Also I plan on stuffing at least 2' x 2' of insulation in the corner about the closet. And maybe all the way across.But again that's later, after measurements. I'm just excited how things are panning out.

A very simple but very effective one we did for a client a few years back, was a simply large diameter steel pipe (think_ sewer pipe: maybe 4" OD), welded to a much larger diameter round steel plate that sits on the floor (with sorbothane pads under it), a small steel plate the same diameter as the pipe welded over the top with a hole drilled in the middle, and a nut welded in the hole. The nut takes a long piece of threaded bar that is welded to a second large steel plate (large enough for the speaker to sit on), so you can then rotate the top plate to raise and lower the speaker to precise heights, and also rotate it with high precision to get the aiming perfect, then lock it down with a lock nut that is also on the threaded bar. The "sewer" pipe is filled with dry sand. The thing weighs a ton, but is very effective, and makes it dead easy to adjust the height and aim of the speakers, as well as being re-usable for different speakers in the future, if you decide to change. So make the sewer pipe shorter than the height you would need for the largest speaker you can imagine every using, then make the threaded bar long enough for the smallest speaker you can every imagine using.

It took a couple of hours of welding and cutting and fiddling to do each one, but a good metal worker can knock out a pair of them in a day. Word to the wise: don't put the sand in until the stands are in place! You'd need a crane to move then after the sand is in....

So I took my time and got my speakers as close to perfectly positioned as I can. I even got a laser level to help make sure they are pointed exactly at the spot recommended. Such little things again added a noticeable improvement.

Absolutely! Too many first-time studio builders just do not realize how important that is: they think that if one speaker is off by an inch or so, it's no big deal... In fact, if it is off by 1/8" inch, I'd be in there, fixing it!

But transparency, depth, and width of sound stage are definitely improving.

Yup! Ain't it wonderful when reality matches theory?

Then hopefully soon take some measurements. See what my ears are telling me.

Take REW tests ALL THE TIME! Any time you do something to the room, do a full REW test immediately, so you have a full record. Then you can see what is working, what isn't what cause produced what effect, etc.

But of the 3 corners I have left, There's really only one in which I can put a full super chunk.

Then put a superchunk in it! There are TWELVE corners in a rectangular room, and ALL of them are really good candidates for bass trapping. It's a small room, so trap the hell out of it!

So here's my thoughts. It's obvious the round insulation tubes I have weren't doing anywhere near enough for bass. But what if I filled them with some other insulation. I know in my research I found one recommendation for some of the "fluffy" insulation that had actually been measured to actually be effective.

You are not going to get a huge change in isolation by changing the type of insulation. Maybe some, yes, but the REAL change comes from the DEPTH of the insulation. The deeper it is, the lower it goes. Of course, you still need to check the specs for the insulation to make sure it IS the right type, but what will get you the REAL difference, is making it THICK. Any place in the room where two boundary surface meet at a 90 angle, is a good spot for deep, thick, large bass trapping.

Also being a small room, I figure treating the first reflection points on the rear wall will also help.

In every control room on the planet, the rear wall is a HUGE problem. It does not just need a few little pads if insulation: The ENTIRE WALL needs treatment. Thick. At least 6" thick, across the entire wall.

That wall is not really a first reflection point, but it is a major problem: SBIR, flutter echo, "slap-back" possibly, for example...

Then make another and hang it on the closet door.

If that were my room, I would take off the closet door completely, empty it out, and fill it entirely with insulation, then put fabric on a thin frame over it, to hide it form sight.

Then maybe a cloud. Although with the ceiling slanted like it is, I'm wondering how necessary it is.

Very necessary. Take a look at that other thread to see how the room acoustics improved when he put the cloud in.

- Stuart -

Alright so I did some rough measurements of how the room is right now. I'm not seeing that much difference from my earlier tests, but also not an expert at reading these things, because my ears definitely say things are better. And for the life of me, the levels still seem a bit low. I'm really at a loss as to why. I'll keep trying. Partial Superchunk and F Reflection point Measurements

My plan as of now is to buy about 5 more bundles of insulation. Once I get that I'll fill up the front corners the rest of the way and take out the first reflection point traps I have up. Measure. Before I post any more measurements I'll keep trying until the levels are where they're suppose to be.

After that I'm not sure what the best order would be as far as treatment placement. Obviously I have the two panels I built for first reflection points, but if doing the rear corners first would be better I can start there. And with that amount of insulation I should be able to fill up both back corners by the closet, move a full 2'x2' of insulation to the top of the closet and fill it all the way to the ceiling, and still have enough for 2 - 2'x4'x4" panels. I was planning on putting them where the speakers are aimed at on the back wall. But I can wait on that if some where else would be more useful. After that I'll buy what I need to make a cloud. Somewhere around that point is where treating this room will have to be as good as it gets. I could do some more panels on the side/back walls if needed, but the closet unfortunately can not go. And it can't be filled with insulation. It's being used as a closet and I don't have anywhere else to put the stuff that is currently in there. And this is sort of a "temporary" room anyway.

I've always planned on building a house that will have a control room and at least a live room big enough for a band that can also double as a home theater room. Very possibly a couple of smaller rooms if I have the space. And after reading through the other thread, I'm even more determined. Dimensions will be different but the idea is very similar. Although it will be a while before I can start properly moving forward with the planning. After going through a divorce, I'm still getting my finances in order. But once I get there, I will be hiring someone to design the space to be a serious studio space. I want to wow people. And I do have visions of making it a business. Even if it is only my side gig/ retirement job. If you have any recommendations I'm all ears.

So anyway I'm thankful for all the help so far, and any more I get on the way forward. Let me know what you think the order should be for adding treatment. Like I said I plan on buying enough to do almost everything besides the cloud. And that's only because I have no idea what it will take, and if that can even be determined now. Or if I need to get more treatment up and measure first. If there's some way I can figure that out, I'll happily get what's needed for that while buying the rest. My biggest issue is it's almost a 2 hour drive, one way, to pick it up. So I'd like to get as much as I can on the next trip. Then I'll start building and adding insulation where ever you recommend. And as usual no rush. It might be a month or two before I get a chance to go get the next round of insulation. Anyway I'm excited to see what can be done in here, and even more excited to build a proper studio from scratch.