Project studio/music room - construction phase

Gregwor wrote:

So your plan is to always have your screen(s) on the front wall between the speakers? Personally I think I'd like a desk where the screens are in a similar position to your rack gear (maybe sunk into the desk more) and have the rack gear vertical on the desk to my left and right simply because I am over outboard processing so my rack gear will mostly consist of preamps and converters.

Thank you for your kind words, Greg! I was thinking about the screens that would be sunk into the desk, but finally I liked the idea of one big 4k screen more - there should be enough real estate for both mix and edit windows and I hope, that such setup would keep me in a more "healthy" sitting position, to save me from back-ache. I don't know how much outboard gear I will use, but you are right - the preamps could be placed anywhere and it's probably waste of space to put them on the desk. On the other hand, 19" rack is pretty universal thing - for example I found out that I could put a DAW controller (Avid Artist Mix) in one of the 6U rack spaces that are unused yet. Time will tell I guess - I'm not very experienced in this, as you could probably tell :) Martin

I was thinking about the screens that would be sunk into the desk, but finally I liked the idea of one big 4k screen more - there should be enough real estate for both mix and edit windows and I hope, that such setup would keep me in a more "healthy" sitting position, to save me from back-ache.

Yeah, and 8k is around the corner too. I personally just hate looking up at my screens/televisions.

I don't know how much outboard gear I will use, but you are right - the preamps could be placed anywhere and it's probably waste of space to put them on the desk. On the other hand, 19" rack is pretty universal thing - for example I found out that I could put a DAW controller (Avid Artist Mix) in one of the 6U rack spaces that are unused yet. Time will tell I guess - I'm not very experienced in this, as you could probably tell :)

We are all trying to keep up with the technological advancements of the world. It's crazy how large consoles and outboard gear is getting replaced so quickly. Even DAW controllers seem to be a thing of the past. I remember when everyone had a Control 24 or actual console. Now, all of my friends who had them sold them for next to nothing. My buds who have small fader bank controllers all tell me they never use them short of pushing up faders in a fresh mix session (which takes <10 seconds on it and ~ 20 seconds with a mouse). I love the idea of a tiny desk like yours. I have a SketchUp model started for one but I doubt I'll open it until I have the rest of my design complete. Greg

My new job got in the way of my studio build, so not much to report, but here are the measurements after I placed the desk in the room and after I built one more big poly diffuser on the ceiling in the back of the room: Desk and diffuser measurements All first reflections points are covered - there's nothing above -25dB level, ever: As I measured frequency response of the right speaker, it looked quite good - the response is probably as good as I can expect in my room, short of digital tuning: But as the fog has lifted even more with additional treatment, it showed the ugly truth of the left speaker: There's a big, very narrow dip at 146Hz that doesn't make any sense to me. Could it have something to do with the asymmetry of the back of the room? The treatment even accentuated this: the right back corner has angled door, with no treatment whatsoever (the left speaker fires sound directly at the door). The left corner has thick bass trapping otoh... :?

We are all trying to keep up with the technological advancements of the world. It's crazy how large consoles and outboard gear is getting replaced so quickly. Even DAW controllers seem to be a thing of the past. I remember when everyone had a Control 24 or actual console. Now, all of my friends who had them sold them for next to nothing. My buds who have small fader bank controllers all tell me they never use them short of pushing up faders in a fresh mix session (which takes <10 seconds on it and ~ 20 seconds with a mouse). I love the idea of a tiny desk like yours. I have a SketchUp model started for one but I doubt I'll open it until I have the rest of my design complete.

Greg - many thanks for sharing your real life experience, you probably saved me from buying unnecessary stuff and losing money in the process. I'm sure you know this feeling - all those faders look so tempting :)

As I measured frequency response of the right speaker, it looked quite good - the response is probably as good as I can expect in my room, short of digital tuning:

Your impulse response there looks like it has some early reflections within the desired 20ms ITGD. That could be tied in with your 146Hz issue. Do you have any insulation to place up against your door to see if that helps the issue? Can you check the distance to see if it coincides with 146Hz? Greg

but here are the measurements after I placed the desk in the room and after I built one more big poly diffuser on the ceiling in the back of the room:

Cool! More data to play with! :) :thu: OK, firstly, you need to smooth your data. You are looking at it unsmoothed, but that produces graphs that are way, way overboard in the mids and highs, with details that aren't really there, and which you would never hear even if they were. So, when you are looking at the very lowest end, yes, you can leave it unsmoothed, or maybe apply 1/48 octave smoothing. For the lowest part of the low mids, I normally use 1/48 or 1/24. For the mids, 1/24 or 1/12, and for the highs, 1/12 or 1/6. Those are realistic smoothing factors that fit how our ears and brains work with the PERCEPTION of sound: that's a field of acoustics called "psycho-acoustics": how we perceive sound, as humans, rather pure acoustics, which is about how sound really is. It's not the same. So apply smoothing as needed, depending on what you are looking at. In general, for rough overview, apply 1/24 octave smoothing. Right, next: More on psycho-acoustics: we are very good at perceiving narrow to broad peaks in both frequency and time, but not so good at perceiving narrow dips. Since dips are often phase related (reflections cancelling each other) they don't "ring" like modes or other forms or resonance do. We are good at hearing resonance, not so good at hearing cancellations, unless it is rather broad. And since musical notes played on instruments are almost never tight and narrow, it's unlikely that a tight, steep, high Q dip is going to be terribly audible. So, first question: can you actually HEAR that 146 Hz dip? As REW scans up the spectrum, do you really notice that dropout? If you do notice it, then it's worth doing something about it. If not, then it may not be worthwhile chasing. Now for the good news: your desk is effectively killing your floor bounce! You've had a reflection at around 4.6ms since the start, and your desk is stopping that. This is good! And the not-so-good news; you have a prominent reflection at around 10.5 ms that has also been there for a while, but is now stronger: perhaps because it was being masked by other stuff. It's a fairly strong reflection, although not huge. I would use the "string trick" to try to track it down. 10.5ms is about 361cm of sound wave travel, and since this is a reflection that comes AFTER the direct sound reaches your ear, it is 361cm PLUS the ear-to-speaker distance. So measure the exact distance from the tip of our mic capsule to the acoustic center of the speaker, add 361 cm, and cut a piece of string that is exactly that long, plus 10cm. The 10cm extra is so that you have 5cm on each end for attaching the string! Tape one end to the acoustic center of the speaker, and the other end to the tip of the mic. Or better still, to a mic stand that you set up right where the tip of the mic is, so you aren't messing with the mic. So now you have a very long piece of string laying on the floor, that represents the exact time that the sound wave is taking to get from the speaker to your ear. Now you need to gently stretch out that string into a triangular shape (the speaker at one end, the mic at the other, and your hand at some point in between) and try to find the places in the room where that string will just touch one of the surfaces while BOTH sides of the string are taught. There might be several places, but if you mark them on the wall/door/floor/ceiling and join the marks, you'll probably find that all of the marks are on an elliptical curve. That's good. It's the location of the place where the wave-front is hitting and bouncing back. Look for the spot where the string seems to be "bouncing symmetrically" to the surface, with the "incoming" string and the "outgoing" string making roughly the same angle with the surface. That's the center of the reflection. That's where you will need treatment. To test if that really is the correct spot, try putting a large piece of 703 that covers it, and test again with REW. There should be a reduction in that refection. If that works, then let me know, and based on where the problem is located, we'll figure out what to do about it. Considering the long distance, my guess is that it is something at the rear of the room, probably your door or maybe some of the HVAC duct work. You also have two other fairly large reflections that might be worth dealing with, of you really want to: 13.7ms (small) and 19.2ms (large). So if you are up to it, then do the same thing with a piece of string that is 662 cm longer than the speaker-mic distance (19.2ms), and 471 cm longer (13.7ms) Both of those are probably second order reflections: bouncing of two surfaces in succession. That's a LOT harder to find with the string, but if you are careful, you might get it. There's a couple of much earlier reflections (around 2ms) that we might also need to look for, but that can be later... I don't think these are related to the desk, or to the 146 Hz dip. They might be, but there isn't much connection. There's more in your REW that is worth looking at , but go for those issues first. And there's good news, too: your room can get better than it is, if you want! :) PM me... - Stuart -

Cool! More data to play with! :) :thu:

It's so good to read a quote like this, Stuart - it shows you really love your work :D . Many thanks for pointing out those early reflection that both you and Greg wrote about. I did use your method and I found out that the problematic spots are on both of the vertical poly diffusers. This was confirmed by hanging a small piece of 703 on the poly where it faces the speaker like this: The reflections vanished(even the one at 19ms): I probably made them too deep (they are 47cm wide and 17cm deep). If they were shallower the angle of the reflections/diffusion would probably not include the listening position. Here's the measurement file (left speaker only): poly reflections About that 146Hz dip:

So, first question: can you actually HEAR that 146 Hz dip? As REW scans up the spectrum, do you really notice that dropout? If you do notice it, then it's worth doing something about it. If not, then it may not be worthwhile chasing.

Yes, the dip is very noticeable - if I run a slow 10s sweep from 100 to 200Hz, the sound between 140 and 150Hz is attenuated quite a bit. So I would definitely like to solve it somehow. I noticed some disruption in phase at the problematic frequency: Does it tell us something useful? Many thanks once again (will PM/email you on Monday)! Martin

I did use your method and I found out that the problematic spots are on both of the vertical poly diffusers.

Ahh, yes, well, ... but are they TRUE poly curves, like I showed before? :) viewtopic.php?f=10&t=21539&start=42 What you are experiencing are specular reflections, so you could try breaking up the surface of the poly with a series of large half-round "planks" running vertically up it. You don't want more absorption in the room: it's already a bit on the dry side. So let's try to solve it with partial non-numeric diffusion. But at least I was right about it not being relate to the 146 Hz dip. That is something else, unrelated to the 10ms reflection.

Yes, the dip is very noticeable - if I run a slow 10s sweep from 100 to 200Hz, the sound between 140 and 150Hz is attenuated quite a bit. So I would definitely like to solve it somehow.

OK, so you do need to chase it down, then. It's broader than it looks.

I noticed some disruption in phase at the problematic frequency: ... Does it tell us something useful?

Yup. It tells us that it is a phase cancellation issue! I noticed that in the data fro yesterday. It is most visible in the excess phase graph: And also in the group delay graph: Big-time phase shift. So it's some type of reflection, for sure, but there are many possibilities. It's not modal, or we would have seen it before. It could be a floor or ceiling bounce. It appeared at the same time as you installed your desk, so I'd start by checking the desk: Lay a blanket over it, then put a piece of insulation (thin) on top of the blanket, and see what that does. - Stuart -

It appeared at the same time as you installed your desk, so I'd start by checking the desk: Lay a blanket over it, then put a piece of insulation (thin) on top of the blanket, and see what that does.

With a bit of luck I found out where the problem was - some thin ray of sound found its way through the cutout in the left side of the desk, bounced of the floor, narrowly missed the upper board and hit the microphone. These speakers have a rather big mid range domed speaker, so it seems to me that it does not suffice only to take into account acoustic axis of the speaker, I have to control wider space around it. After I filled the cutout with insulation, the 146Hz dip was there no more:The smaller dip that's still there at 135Hz seems to be a modal thing, as it is present at the right speaker, too?It seems that perhaps this was the dip that I actually heard when doing the 100-200Hz sweep. Here are the measurements: Desk sides fixed I have a suspicion, that those 5dB hills at 50Hz and at 12kHz are a part of the crossover thing - that's why the manufacturer only states -dB rating for these speakers (Frequency Response -6dB: 32Hz–22kHz). But that could be probably solved by EQ? Regarding the polys:

Ahh, yes, well, ... but are they TRUE poly curves, like I showed before? :)

Well, I tried, but it was by no means CNC precision. It was definitely close to the catenary curve, but it's perfectly possible, that some parts were a little flatter than they should be... :oops:

What you are experiencing are specular reflections, so you could try breaking up the surface of the poly with a series of large half-round "planks" running vertically up it. You don't want more absorption in the room: it's already a bit on the dry side. So let's try to solve it with partial non-numeric diffusion.

How large do you think? Something like 5cm wide and 1cm deep, length same as that of the poly? Thank you for staying with me on this adventure :)

After I filled the cutout with insulation, the 146Hz dip was there no more:

Great! Glad you found it. It had to be the desk.

so it seems to me that it does not suffice only to take into account acoustic axis of the speaker, I have to control wider space around it.

Absolutely! Always! With all speakers! There's a parameter called "directivity" or "dispersion" to consider: Speakers radiate sound in ALL directions, all around, front and back. At the low end of the spectrum, it's pretty much spherical, the same in all directions, and as you go up the scale it concentrates more towards the front, less towards the back. At the very top end, it is nearly all going directly forwards in a cone shape. But for most of the range, there's still considerable sound radiated far off the acoustic axis. How far off axis depends on the speaker, but with decent studio reference monitors you can count on that being at least 30° off axis, and probably more. Especially in the mid range. It's tighter in the vertical axis, usually, and wider in horizontal. Controlling the off-axis sound dispersion is a big part of treating the room.

Here are the measurements

There's a large improvement, yes, but there's still something going on there. It seems to be a similar issue on the right side. Here's the combined L and R frequency and phase response, BEFORE and AFTER you did the fix: You fixed the left side, it seems, but the right still seems to be doing something, at a slightly lower frequency, around 135 instead of 146.

Well, I tried, but it was by no means CNC precision. It was definitely close to the catenary curve, but it's perfectly possible, that some parts were a little flatter than they should be..

Are you SURE you took a close look at the shape I linked you too? :) 8) Yours are based on a "squashed cylindrical" shape, not the shape I showed. Here are several possible "poly" curve shapes. Yours is the one on the left, Curve "A". Mine is the one on the right Curve "E"... (the corner control room is the next one over, Curve "d") Check the link back to the photos I posted at that time...

How large do you think? Something like 5cm wide and 1cm deep, length same as that of the poly

Yes, length same as the poly. I think you'll need to go deeper than just 1cm. Try with whatever scrap pieces you have laying around right now,. Anything will do, even if not rounded. Just stick them on with bits of duct tape temporarily, to see if they have the desired effect. One other thing: your left speaker is about 1 dB louder than your right: Please turn it down by exactly 1 dB (or turn UP your right speaker by 1 dB! Same result).

Thank you for staying with me on this adventure

:thu: - Stuart -

There's a large improvement, yes, but there's still something going on there. It seems to be a similar issue on the right side.

Today I was trying to catch the reflection that is causing this behavior and I thought I was going to get crazy for a moment. I made like 20 measurements, tried different angles, multiple angles, I was hanging insulation on different places at once, but nothing helped :x Then I looked at the older measurements and I noticed, that this phase shift was there from the beginning - every measurement of the right speaker has it. The only one that mysteriously doesn't is the one right after I installed the side walls treatment. And I'm inclined to believe that I accidentally renamed those measurements: left for right and right for left. So this one definitely has nothing to do with the desk. Is it possible, that this phase shift is caused by something else than a reflection?

Are you SURE you took a close look at the shape I linked you too? :) 8) Yours are based on a "squashed cylindrical" shape, not the shape I showed. Here are several possible "poly" curve shapes. Yours is the one on the left, Curve "A". Mine is the one on the right Curve "E"... (the corner control room is the next one over, Curve "d")

Oh, I see - of course I didn't :oops: My polys were already done at the moment you posted the picture and since it seemed that they were doing their magic just fine I thought they were OK. I'll try to solve the issue with the round planks and if this won't help I'll redo the polys - I too want this studio to amaze people ;) Many thanks! Martin

Yes, length same as the poly. I think you'll need to go deeper than just 1cm. Try with whatever scrap pieces you have laying around right now,. Anything will do, even if not rounded. Just stick them on with bits of duct tape temporarily, to see if they have the desired effect.

I tried this with some quarter-round planks, that I glued together to form half rounds (4.5cm wide, 2.2cm deep). Here's the result: BEFORE: AFTER: The reflections are still there, they are just much smaller. Would rebuilding the polys to "d" or "e" curve help me to achieve significantly better results? Martin

Let's see the actual MDAT... :)

The reflections are still there, they are just much smaller.

Yup! So the concept is correct... maybe just not the dimensions... However, you did get a pretty good reduction there. - Stuart -

Let's see the actual MDAT... :)

Of course - here you go... There are 4 measurements: 2 for L and 2 for R speaker, both with and without planks.

I see the total count of the views is closing on 10.000 and I haven’t updated the status in a while. The progress slowed down a little as I had to go back to work after 4 months, but this is how the studio looked like at the end of the year: I re-did the vertical poly diffusers to be of ‘D’-type curve: This helped with the reflections I was dealing with in the previous posts.

In the meantime I started to work with Stuart on the digital tuning, as he agreed the room was treated well enough / was ready for this next step. I wanted to process with the tuning before finishing the room with the fabric in case there would still be some additional treatment needed. In the process Stuart noticed there’s still some flutter echo in the room. After analyzing the room (read: clapping and jumping around ) I noticed these were the problem areas(red): The green ones are OK, because these parts of the walls are angled. Because the room is very small and the space is at premium, I decided to try dealing with the flutter and effectively using the space at the same time. Two horizontal diffusers, guitar cases, a bookshelf and a small combo amp strategically placed in the problem areas: It worked quite well and there’s no flutter noticeable anywhere in the room now. At the same time it’s now furnished like I’d like it to be and I have everything I need close at hand. Hopefully the end of digital tuning process is near and I'll be able to share the results.

Even with just exposed insulation, it looks gorgeous! Great work dude! Greg

Thank you, Greg! My daughter's friend (9yo) commented: what a cozy little room! I'm tempted to leave it as it is :)

This has been one fast ride! For the last one and half month Stuart and I worked on the digital tuning of this small room. We exchanged emails almost daily, sometimes several times a day and now the room is finally ready. I'll leave it to Stuart to present and explain the graphs, I just want to comment on some small acoustic treatment bits that were added in the process of digital tuning. There was a big dip (>20dB) in the frequency response at around 130Hz. It was not noticeable when listening to the speakers, but still the measurement showed there was some problem and with Stuart's assistance we found out it was a floor bounce. That's why there are those small towers of mineral wool on both sides of the mixing desk and also the angled plywood/mineral wool panel under the desk (kind of inverted ceiling cloud): These solved the issue, now I only need to find a way to make them less ugly :) (and to cover the mineral wool with fabric panels to make the room more presentable...) This whole process showed me that digital tuning is an amazing tool in the hands of an expert. And if it goes hand in hand with acoustic treatment of the room, of course. The results are much better than I dared to believe given how small the room and how unlucky the dimension ratio is (2:1:1)... Big thanks to this amazing forum (and John and Stuart)! Martin

The tuning process is finished, so I'd like to share some graphs to show how this whole adventure ended (this is excerpt from Stuart's mail, he might want to chime in with some more comments): Frequency response is now flat to within +/- 2.4 dB across the entire spectrum, 28 Hz to 21 kHz (1/24 octave smoothing): And even better when smoothed to 1/3 octave, as required for international specs: At that scale, we are getting +/-1.2 dB. For example, ITU BS.1116-3 requires +/-3 dB, and even then it's only from 250 Hz to 2 kHz... we get +/- 1.2 dB across the entire spectrum. The Left and Right channels are within +/- 0.9 dB across the spectrum (1/3 octave smoothing). The same specification as above requires +/- 2 dB: The waterfall below 500 Hz is very smooth and flat: And the spectrogram shows the same: smooth and flat across the entire low end: After this the "house curve" was applied to make the speakers/room system sound more natural (more like our ears are used to hear things): The blue curve is the "flat" response, and the purple curve is with Stuart's House Curve applied You can see the slight bass boost and treble cut... It took me some time to get used to it, but now I wouldn't get back to flat response. Big thanks to Stuart for helping me making this a reality! Martin

Great work! Crazy good results! What processor are you using for eq? Greg

FBQ-2496, but it's crazy finicky to get right, and the manual is next to useless. There's also MIDI communications problems with REW that cause the data to not upload correctly sometimes... at random.... It does the EQ job fine, but I don' recommend it unless you are prepared to sit through the pain of trying to make it play nicely.... - Stuart -