50 sqm live room sounding bad - How to fix?

[gabrielaudio]

Hi there to everybody!

My name is Gabriel and I'm new here. Just came to this forum thanks to Stuart . I just read the rules and I'm ready to share some of my nightmares with all of you ...let's see where this ends

My partner and I have a studio that was designed by a famous acoustic engineer who probably did his best (or not, who knows...)...anyways...the result is not what we need. Actually, some of his ideas are the main problem. My partner built the studio using his design several years ago and he has been fighting with it since then. With fighting I mean: nothing sounds as expected

Main issues:
- The room sounds dull, lifeless and Cymbals don't sound as good as it should be in a room like this (200 cubic meters). The feeling is that there is a lot of mid frequencies masking and bass freqs overlapping, and harsh highs/treble too. Somehow everything we record sounds dull and harsh, and we have to spend a lot of time playing with the microphones, moving instruments and mixing the songs to try to "solve" these acoustic issues.
- There is some flutter echo, this could be part of our cymbals and harshness issues I guess...
- Room mics often don't sound good and are not really useable.
- The room looks very ugly "thanks" to the concrete (unpainted) and Celenit. We want to paint the concrete in case we don't cover it.

How it was built? It's a box in a box, floating floor and walls (room floor and walls are isolated from each other).
- 3 of 4 walls were built using 10" x 6" (approx) Slotted CMU. Something like this:

The center frequency would be something around 200Hz-250Hz, supposedly.
It's very similar to this https://www.soundseal.com/general.html, but the company was Soundbloc and not Soundblox. Anyways, it looks the same.

- 1 of 4 walls was built with normal concrete blocks (without slots).


- Ceiling: Celenit N 35 mm (1.4"): made with Celenit + 20cm airgap + Danosa M.A.D.2 (high density acoustic membrane) + plasterboard + M.A.D.4 + fiberglass . Based on this graph that I found:

I think the absorption coefficient would be something between D and F.
- Floor: real wood + floating floor.

The size of the room is 50 sqm approx:
Height: 410 cm
Length: 980 cm
Width: 528 cm

We would like to have a more "wet" or "live" sounding room, and more importantly, more balanced! More suited for recording drums and acoustic instruments. We want to have a live room where the drum sound is balanced, representing the drum kit correctly and with enough "room sound" to create more depth and character in our mixes (avoiding room reverb plugins). I think our room has good dimensions for it, but we'll need to treat it carefully.

Some measurements with REW (without GOBOs, carpets or any acoustic treatment in the room):
- Corner to corner: speaker in one corner and microphone in the opposite corner

- Speaker where we place the bass drum. Microphone where we place one of the room mics

- Another room mic position. Speaker where we place the Bass Drum. Microphone closer to one of the corners in front of the kit.

MEASUREMENTS:

RoomMicPosition2.mdat

(2 MiB) Downloaded 1127 times

RoomMicPosition2.mdat

(2 MiB) Downloaded 1127 times

RoomMicPosition1.mdat

(2 MiB) Downloaded 1162 times

RoomMicPosition1.mdat

(2 MiB) Downloaded 1162 times

CornerToCorner_NoGOBOS.mdat

(2 MiB) Downloaded 1165 times

CornerToCorner_NoGOBOS.mdat

(2 MiB) Downloaded 1165 times

After all of these measurements and after asking in other well known forum ( ) we installed some panels in the ceiling. Now the room sounds a bit brighter than in those measurements, but still unbalanced and actually I have the feeling that those big panels introduce some extra comb-filtering when we record in that area. So, we want to remove them and, thanks to Stuart suggestion, cut them in smaller pieces and place them differently.

---------

So, in conclusion, we need to improve it, but with this COVID crisis our financial situation got a bit worse and our budget is less than 2000 €. So, I know we should first focus on the main issues and the ones we can benefit more from.

For example, I designed a Polydiffuser array with the idea of placing it in one of the long walls, but based on Stuart's recommendation it may not solve what I expect since I was expecting to solve
2) Flutter echo issues: it would add scattering and some diffusion and then reduce the flutter echo between parallel walls.
3) Covering the Slotted CMU Blocks, and therefore balancing the room a bit, that's why I wanted it to work down to 200hz.

BUT probably it won't do as much as we need to solve the 3). But it was going to be cheap: a carpenter sent us an estimate of 450 € for building and installing it on the wall.

So, the question is...what should we do? What would you recommend to start with and how? Should we cover the Slotted CMUs with plasterboard and then install acoustic treatment? Should we fill the Slotted CMUs with something to block their absorptive effect? Should we install tuned bass traps or Corner Chunks? And the ceiling?


Hope you could at least enjoy this nightmare I wanted to share...and if you have some advice, I would be pleased to listen and learn. I don't know what will be the future of the studio after this COVID crisis but at least I want to try to improve the sound of it, even if we have to close it right after!

Best!
Gabriel

[Soundman2020]

Hi Gabriel, and a very big WELCOME to you! It's really good to have you here. I'm so glad you found the new forum, and joined up.

Just adding a bit more background for others who will be following your thread: I think it was about a year and a half ago that I saw Gabriel first posting on another forum, with his sad tale of this studio, which should sound really good but in reality sounds awful. (Gabriel, maybe you could post some raw drum tracks here on the forum, in MP4 format, that you recorded in there, with no EQ or effects: just the original rough mix, as recorded, so other forum members can hear just how bad it sounds). When I first saw the photos back then, I was really surprised at how the room was designed and built, because it goes against a lot of basic acosutic theory, yet it was designed by a "big name" in the studio business. One of the key question marks I saw back then, was how the entire studio is done exactly the same on all four sides, with those slotted concrete CMU's (concrete blocks).

For those who don't know, those CMU blocks are actually very specifically designed and manufactured as acoustic elements: they are, in fact, Helmholtz resonators, tuned to a very specific frequency. They are not just ordinary concrete blocks (also known as "breeze blocks", "cinder blocks" or "Besser bricks" in various countries). Normally, the typical ones used for general construction look like this:

But the ones Gabriel's place is built with, look like this:

For those who know a bit about acoustics, you can see that this is a classic Helmholtz resonator: there is a sealed cavity inside, and a slot in the front. The air trapped inside the cavity acts like a spring, and the "slug" of air trapped in the slot, acts like a small mass that can "bounce" on that spring, moving in and out. So this is a resonant system, and works the exact same way as when you blow over the top of an empty beer bottle or small Coke bottle: the slug of air vibrates in and out of the slot, and the spring is what keeps it vibrating at a very specific frequency. Studio designers often use Helmholtz resonators in various forms as part of the acoustic treatment in a room, because the device can "suck out" resonances of various types. So if there is a modal problem at one specific frequency in a room, then you can tune a Helmholtz Resonator to that frequency, and that can help to "kill" that resonance in the room. Basically, a Helmholtz resonator will absorb one specific frequency range.

The trouble is, ALL of the bricks in Gabriel's room are tuned to the exact same frequency! And it just happens to be 250 Hz.... You can clearly see the effect that is having on the acoustic response of the room. There is almost no 250 Hz at all in that room! Because the entire room is "sucking that out", on all four side. In fact, the tuning of these blocks is not very tight (you can see that by the sort of wedge-shaped slot: the sides of the slot are angled, not parallel), so it is tuned a bit off: technically, the Q is not high and sharp, but lower and broader. In fact, they cover the entire frequency range from about 150 Hz to about 350 Hz... which you can also see on the graphs that he posted.

So that's the first issue with Gabriel's room: the entire bottom end of the mid range is gone, along with the top end of the bass range. That is dead, as you can see on the graphs, because the entire room is trying to kill it, on all four sides.

To put that in perspective, the fundamental tone of many snare drums is around 230 Hz, give or take maybe 50 Hz... which is why when I first saw that, I commented to Gabriel that I bet drums sound like cardboard boxes in that room: A bit of "snap", but no "body". More of a "thup" sound, rather than a nice clean "crack".

Then there's the low end: It is way TOO resonant! The delay time at that 250 Hz fiasco region, is roughly 200 ms... that is very low for such a large room! But as you go lower down the spectrum, below about 150 Hz there's a lot of resonance, and below about 40 Hz, the decay times are getting close to one second! Well over 700 ms, around 800 it seems. It is inherently hard to measure such low frequencies accurately, due to the nature of long wavelength sound in small rooms, but my guess would be that the bottom end is around one second. Kicks, floor toms, and some larger rack toms live in that region. Or rather, they have fundamentals down there. And of course, so do bass guitars, the low end of keyboards, the low end of electric guitars, and several other instruments.

So, playing drums in there means that the kick and floor tom are "boomy" and "muddy", and the snare is dull. No clarity.

But then there's the high end, when the hi-hat and other cymbals live: The room is rather dead up in that region too! Everything above about 1 kHz is very dry, for that size room: no "life" for the crash. No "air" for the ride. No "sizzle" for the splash, and even the plain old hi-hat is not very bright.

That's what I suspected when I first saw Gabriel's room, over a year ago, and subsequent REW tests we did at that time, confirmed it.

But there's more! He also has a flutter echo problem in the mid range (very predictable, with those large flat parallel surfaces on all sides of the room!), and a very strange ceiling.

Which leads to another very, very confusing design fault: As Gabriel mentioned, the entire room is floated (walls and floor floated separately), and the walls are very massive. Which is what you would normally do when you need high isolation. Fine. But the ceiling and roof are low mass! The top of the room is basically transparent to low frequency sound, so isolation isn't that good at all! I can't figure out why anyone would design a room for high isolation on only five sides... that's like designing an aquarium for your living room, with glass only on the front, sides, and bottom, but cardboard on the back... how well does that hold water? That makes no sense. But that's what Gabriel and his partner were given, in the design.

Not only that, but the ceiling is done with a strange and inexplicable series of different layers, whose purposes are not clear at all(!)m as you can see from the photos and text that Gabriel posted. There's nothing logical about that. Very surprising.

So, that's where Gabriel is right now: A nice large room, with a good high ceiling, plenty of air volume, plenty of floor area... and it sounds like garbage! Plus, his financials are not doing so well right now, probably for two reasons: 1) Covid-19, for sure: it affects all of us, financially! But also 2) The room is not nice to play in, for musicians. Not nice to record in, sure, but at least there are some tricks you can do in the mix to make things sound better, but the musicians have to play in the room, and suffer the lousy acoustics... which means they are not excited to play in there, not enthusiastic, and I'm guessing that shows in the tracks they produce too. It is important for the musicians to feel comfortable when they are playing: they NEED to have a pleasant sounding room in order to play well! It's not just an attitude thing: it is a real need. Musicians find it very hard to play well if they can't hear their instruments well. And for a band playing together, they cannot play "tight" and "clean" if they can't hear each other properly. So I'm guessing that part of the financial issues that Gabriel is seeing with his studio, is musicians not being so keen to play in there, and preferring other studios.... Once the room starts performing well, then the musicians will also perform well, sound better, be happier, and they will WANT to come to his place to record! Then the financials will start improving too.

So, what I have suggested for Gabriel, is that we take a structured, methodical approach to treating his room, doing one thing at a time, starting with the biggest issues visible in the REW data, then working our way through to the smaller issues. The "problem" with that approach, is that the visibly big issues (250 Hz suck-out, 40 Hz build-up), are NOT the ones that are most obvious to someone standing in the room! What he hears in there mostly is the dullness: lack of high end, and the flutter echo. We could attempt to treat those first, but I strongly suspect that he would then need to treat them all over again once we iron out the "big" ones. Because I'm pretty sure that, as we treat the low end and the 250 Hz suck-out, when those areas get back to where they should be we will also start seeing some OTHER issues with the room. Its not that there will suddenly be new issues arriving: they are already there. But they are hidden behind the "big" problems rightnow, and will only reveal themselves more clearly once the big ones are subdued. In other words, there's a lot of modal "mush" in the bottom end, and as we clean that up, we will probably see other issues that will need treatment. The same with the 250 Hz suck-out: as we start putting some life back into that region, then other issues that are currently latent there, will show up. Maybe I'm wrong here (hopefully I am wrong! I would really like to be wrong on this point!), and there really are no more acoustic gremlins hiding in the shadows, but i do suspect there are.

Thus, my suggestion to Gabriel is to start by dealing with those two biggies: 250 Hz, and low bass. Even though he won't initially see the major changes that he wants in the flutter and high end, its the logical way to go about it. On the other hand, as we clean up the low end, at least the kick and toms will start sounding a little better! Ans as we clean up the 250 Hz region, the snare should improve a bit too. As will electric guitars and keyboards.

That's for the walls: The ceiling is different. As he mentioned, they already put up some large flat plywood panels hanging from the ceiling, and that helped a but (because the ceiling was rather dead too), but the panels are too large, too flat, and not arranged or angled optimally, so that is something that can be fixed fairly easily, and with not too much expense. Those panels can be re-worked to do a better job. And since Gabriel will need to rent scaffolding or a bunch of tall ladders to do that job, he can also start on the treatment that the tops of the walls will need at the same time, so he doesn't need to rent those twice. The idea of the design I'm going to do, is to save him money every way possible, because he is on a VERY tight budget.

So, that's the sad sage of Gabriel´s beautiful live room that doesn't work. But the happy news is that it can be fixed!


- Stuart -

[gabrielaudio]

Hi Gabriel, and a very big WELCOME to you! It's really good to have you here. I'm so glad you found the new forum, and joined up.

Thanks also for inviting me Stuart!

(Gabriel, maybe you could post some raw drum tracks here on the forum, in MP4 format, that you recorded in there, with no EQ or effects: just the original rough mix, as recorded, so other forum members can hear just how bad it sounds).

Done! I uploaded some tracks that I think represent more or less how the room actually sounds. It is only Overheads and Room microphones tracks, where you can hear more the acoustic environment (with snare, toms or kick microphones it's less obvious).
Please take into account that AEA R84 is a big ribbon microphone, so it will be always darker than a condenser. This is its frequency response:

This microphone sounds very natural and picks a looot of room sound. So if you are in a bad sounding room, it will show you what you have.

OH with AEA R84 - DRUMKIT1

[ Play Quicktime file ] OH AEA R84.m4a [ 2.11 MiB | Viewed 22674 times ]

Mono Room with a Neumann U67 Vintage, 4 meters away from the drum kit - DRUMKIT1

[ Play Quicktime file ] Mono Room Neumann U67.m4a [ 359.3 KiB | Viewed 22674 times ]

In Front of Drums BLUEMLEIN AEA R84 1 and 2 - Typical "front of kit" setting - DRUMKIT2

[ Play Quicktime file ] In Front of Drums BLUMLEIN 2 AEA R84.m4a [ 312.89 KiB | Viewed 22674 times ]

[ Play Quicktime file ] In Front of Drums BLUMLEIN 1 AEA R84.m4a [ 114.16 KiB | Viewed 22674 times ]

With these 4 audio files you should get an idea of whats happening. My opinion is
- It sounds too dead for being a 200 cubit meters room. I have recorded drums in studios with a similar size and the sound of it was completely different.
- When you are recording drums in a good room...the drum mics sound better than these ones. They were placed by ear, just where it sounded more balanced to me...and anyways it doesn't sound GREAT. In other studios this was easier and also more pleasing. You could compress that microphone and you would get a nice vibe and bite. But here is just muddiness and lack of clarity and lack of punch. To me it sounds like a practice room.
- The snare sounds always like if its energy was being sucked, as Stuart said.
- The cymbals and OH no matter which microphones I use (AEA R84, Beyer MC930, AKG 414, Neumann U67...) don't sound as they should.

My experience in other studios with better acoustics was way different than this, and that's why I know something is bad about this room that we should fix.

To put that in perspective, the fundamental tone of many snare drums is around 230 Hz, give or take maybe 50 Hz... which is why when I first saw that, I commented to Gabriel that I bet drums sound like cardboard boxes in that room: A bit of "snap", but no "body". More of a "thup" sound, rather than a nice clean "crack".

Exactly, no "crack".

So, that's the sad sage of Gabriel´s beautiful live room that doesn't work. But the happy news is that it can be fixed!

Thanks for sharing all your ideas Stuart! Really appreciate it.

It is crystal clear now that we should first address the bass and low-mid area first. My doubt about the Slotted CMU is...how can we reduce or block their absorptive effect? You mentioned last year that we could just put some wood in the slots but...it sounds like a tedious work and I'm not sure if it will look good. What about covering the entire wall with plasterboard or some thin wood panels? Would you like to share some thoughts about it? And bass...I guess just placing some corner chunks is not going to improve a lot since bellow 100 Hz what works best is pressure-based bass traps and not velocity based traps (porous absorber). That's what I know so far

And about the economical situation, yes...everything matters, always. Usually our clients leave happy but I'm convinced they could leave happier. And when you have several years of experience and you start feeling frustrated because you can't accomplish what you have in mind or what you accomplished before in other studios....well...And sadly our issues will continue also with our control room, but that's another chapter...

Best,
Gabriel

[Soundman2020]

Done! I uploaded some tracks that I think represent more or less how the room actually sounds. It is only Overheads and Room microphones tracks,

Oh wow. That's sad. The drums are just lifeless... There's nothing there at all, really. The kick sounds the way I expected: like someone thumping a cardboard box with a shoe, but the snare is worse than I expected: the snare sounds more like a rack tom! I was actually expecting more "snap" from the snare, but it's not there at all: just dull, dull, dull. And the cymbals / hi-hat... well.... No comment.

I have no idea how you manage to do anything with tracks like that, to make them sound like real drums: hats off to your mixing skills!

- It sounds too dead for being a 200 cubit meters room.

Definitely! I think you'd have better success tracking in my living room, which is far smaller and full of furniture.

But here is just muddiness and lack of clarity and lack of punch. To me it sounds like a practice room.

Agreed. And a poor practice room, at that. With a room the size of yours, there should be a lot more life in it.

It is crystal clear now that we should first address the bass and low-mid area first. My doubt about the Slotted CMU is...how can we reduce or block their absorptive effect? You mentioned last year that we could just put some wood in the slots but...it sounds like a tedious work and I'm not sure if it will look good.

Right. Just putting wood panels in front of them is not going to do a lot, as there would still be some resonance going on in there: as long as air can move in and out of the slots, there can be Helmholtz effect going on. Stuffing each slot would work, to kill the resonance, but I'm thinking there might be a better way...

If you could spray-glue some fairly thin low-density insulation (about 1" thick) across the back of a full 120cm x 240cm (4' x 8') panel of plywood, MDF, OSB or something similar, and press that up against the wall, then the insulation should do the job of damping the resonance enough that it won't be a problem. It would probably also drive down the resonant frequency, which would be a good thing! I would suggest doing a REW test with a couple of sheets of plywood like that, and just holding them in place by hand for the "proof of concept" test. In fact, for the test you could skip the spray-glue as well: just press the insulation between the panel and the wall. That way, you won't waste the plywood or the insulation! You'll still be able to use the for something else, even if this experiment doesn't work. You'll need a bit of pressure on those panles, to make sure that you are getting 100% coverage, so get a couple of people on each one. Or maybe push some heavy furniture up against them. If you could do maybe four or five full sheets of plywood like that, all of them up against the same wall, and test with REW before and after, that should provide enough data to get a noticeable result in the graphs. As a secondary test, take half of them over to push up against the opposite wall, and test again, then for a third test, put that second bunch against an adjacent wall.

There can be gaps between the panels for this test: no problem. They do not need to be butting up against each other.

This is not the final treatment! Just a proof of concept. If the works to damp some of the resonance and get back some of your low mids, then I would use the plywood as the backing for a different type of treatment.

Also, please post some photos of how the ceiling is right now, with those big panels you did last year. I'll start thinking about how to cut those into smaller panels, and re-arrange them...

I guess just placing some corner chunks is not going to improve a lot

Right. They would have to be really big to have the effect you want.

bellow 100 Hz what works best is pressure-based bass traps

Right... and I'm thinking of a really weird hybrid that might be worth trying... never done it before, but in theory it should work.... I just need to think it though a bit...


- Stuart -

[gabrielaudio]

Source of the post Oh wow. That's sad. The drums are just lifeless... There's nothing there at all, really. The kick sounds the way I expected: like someone thumping a cardboard box with a shoe, but the snare is worse than I expected: the snare sounds more like a rack tom! I was actually expecting more "snap" from the snare, but it's not there at all: just dull, dull, dull. And the cymbals / hi-hat... well.... No comment.

Exactly!! It sounds like when I started recording bands in a practice room, 10 years ago. And trust me, what you hear is after trying different placements in the room, different microphone techniques, different microphones, etc...We are always working/fighting AGAINST the room and not with it, that's why it's so difficult to get good results. The room is not our ally.

Source of the post I have no idea how you manage to do anything with tracks like that, to make them sound like real drums: hats off to your mixing skills!

thanks!! Well...the before and after is very very different as you can imagine. Proper post-processing, using OH and ROOM samples that I recorded in other studios in the past to create a natural ambiance for the snare, toms and kick that our room lacks...and many other tricks to make the drums sound alive and more real. But anyway...it's just fixing issues, so even if the band is happy I'm not because I know the results would be way better if it sounded good from the get go.

Source of the post Definitely! I think you'd have better success tracking in my living room, which is far smaller and full of furniture.

I'm pretty sure about it!

Source of the post If you could spray-glue some fairly thin low-density insulation (about 1" thick) across the back of a full 120cm x 240cm (4' x 8') panel of plywood, MDF, OSB or something similar, and press that up against the wall, then the insulation should do the job of damping the resonance enough that it won't be a problem. It would probably also drive down the resonant frequency, which would be a good thing! I would suggest doing a REW test with a couple of sheets of plywood like that, and just holding them in place by hand for the "proof of concept" test. In fact, for the test you could skip the spray-glue as well: just press the insulation between the panel and the wall. That way, you won't waste the plywood or the insulation! You'll still be able to use the for something else, even if this experiment doesn't work. You'll need a bit of pressure on those panles, to make sure that you are getting 100% coverage, so get a couple of people on each one. Or maybe push some heavy furniture up against them. If you could do maybe four or five full sheets of plywood like that, all of them up against the same wall, and test with REW before and after, that should provide enough data to get a noticeable result in the graphs. As a secondary test, take half of them over to push up against the opposite wall, and test again, then for a third test, put that second bunch against an adjacent wall.

Sounds like a plan! We already have 240x120 cm plywood panels (the ones in the ceiling that we are going to take down). I'll make these tests next week then. Thanks!!

Question and idea: what about covering the walls with a dense layer of concrete? Just everything, top to bottom, left to right...like if we never had those Slotted CMUs and only the standard concrete blocks. Could that work with what you have in mind?

https://www.youtube.com/watch?v=ZTpvuCLfrpk&feature=youtu.be

Source of the post This is not the final treatment! Just a proof of concept. If the works to damp some of the resonance and get back some of your low mids, then I would use the plywood as the backing for a different type of treatment.

Got it!

Source of the post Also, please post some photos of how the ceiling is right now, with those big panels you did last year. I'll start thinking about how to cut those into smaller panels, and re-arrange them...

Here it is I can upload more photos tomorrow.

Source of the post Right... and I'm thinking of a really weird hybrid that might be worth trying... never done it before, but in theory it should work.... I just need to think it though a bit...

Sounds good even if I still don't know what it is!

Thanks Stuart. All those ideas and tests are extremely useful!!


Best,
Gabriel

[Soundman2020]

Question and idea: what about covering the walls with a dense layer of concrete? Just everything, top to bottom, left to right...like if we never had those Slotted CMUs and only the standard concrete blocks. Could that work with what you have in mind?

That would be a very last resort, if we can't kill the over-damping any other way, but it would make your room sound bad in other ways: more like a concrete pipe! That would need different treatment. I'm hoping that won't be necessary.

But I am seriously thinking of sealing those surfaces: CMU's are very porous (they are made with fly ash, or cinders, or something similar, as aggregate), and that's part of what is messing with your high end. Believe it or not, that type of concrete has a coefficient of absorption similar to a light-to-medium weight curtain! I'm not kidding you here. Even though it is solid and rigid, the porous nature of the surface does, in fact, absorb a lot of sound in the high mids and highs, at rates a little similar to fabric curtains. For example, the absorption of light-medium curtains is around 0.5 at 2 kHz, and 0.4 at 4 kHz. The absorption of CMU concrete is around 0.45 at 2 kHz, and 0.4 at 4 kHz. I kid you not....

So, your walls are acting rather like curtains in that sense: sucking dry the high end. Sealing the surface with a good masonry sealant, or even just painting them, would change that drastically. It would bring down both of those coefficients to something like 0.1, or even lower.

But before you run off and buy several cans of masonry sealant!!!!.... my concern is that it might take things too far the other way: make the room too bright, too "zingy". It might give your room a tinny, nasal sound... which would be very different from what it is now, but unpleasant in another way. The other thing with painting or sealing your walls, is that once it is done, you cannot undo it! If you don't like the results then you can't "unpaint" the walls. With every other type of treatment, it will be hung on the walls or the ceiling, and if it doesn't do what you expect then you can take it off and do something else. But paint is permanent.

If you did want to try sealing the blocks, I'd suggest doing it in small areas at a time, and testing carefully: Maybe do a 5m2 strip vertically up the middle of one wall and see how that works, both with REW and also with your ears. If it sounds good (or if there is no audible change), then do another few m2. If it sounds worse (unlikely!), then stop doing it, and we'll just put other treatment over that area that you sealed.

Also, please post some photos of how the ceiling is right now, with those big panels you did last year. I'll start thinking about how to cut those into smaller panels, and re-arrange them...

Here it is I can upload more photos tomorrow.

Oh yeah! Comb-filter city! And lobing... and strong speculars... and other stuff. We HAVE to fix that. They are in a regular pattern, at the same angle, same direction... and they are LARGE. They need to be done very differently.

Here's a photo of some panels that I did a few years ago for a room intended for a concert grand piano:

Look up at the ceiling, and you'll see a series of small curved panels, hung at different angles and orientations. Your room will need something along those lines, but a bit larger (your room is for drums, not concert grand), a bit less curved (your ceiling is higher), and interspersed with a few flat panels of similar size (you do want some speculars for drums), as well as being hung at different angles. However! don't rush out to do that just yet! There's other things to consider here... those panels work in conjunction with the wall treatment. Because whatever is reflected from those flat ones, will mostly hit walls, so you need to make sure that you have the right treatment in the area where the reflection will hit the wall... So..: the ceiling panels and wall panels need to be designed together. You can't just hang things at random! All of the parts of the room should work together.

Anyway, there's some thoughts for you to consider....


- Stuart -