John Sayers' Recording Studio Design Forum Archive

Hello everybody, name’s André and I’m new to the forum. I’m located in Germany and have a small recording studio inside and old abandoned military complex building. Currently, I am aiming to improve the quality of my drum recordings and therefor, improve the acoustic properties of my live room since I can’t help but feel that it’s not yet at its optimum in terms of benefitting the overall drum sound.

The room

First of all, some data about the room:
Height 3,10m
Length 5,50m
Width 6,10m

It has a suspended ceiling with acoustic tiles made from mineral fibre (it’s like compressed rockwool). The tiles are 2cm thick, and about 20cm into the room. So the perceived height of the room is 2,90m. I didn’t install that ceiling, it was already there when I moved in.

It has a laminate floor on top of the original brick floor.

South, east and west walls are painted concrete, very thick concrete. East wall features two windows (1,25 x 2,00m each), west wall the door into the hallway, south wall is blank. The north wall is a double leaf plasterboard and separates the control from the live room. Note that it was originally only one room and I had the plasterboard wall installed when I moved in.

Current treatment

There are thin but dense curtains (feels a bit like microfiber) covering both windows and the wall in between them from top to bottom. The ones covering the windows are movable and I would usually open them for drum recordings. The other three walls have a couple of auralex minifusors stuffed with rockwool spread over them. Also, there are a couple of Auralex T-Fusors spread around the center of the suspended ceiling, also stuffed with rockwool.
There are two Hofa baby bass traps in both south wall corners, on which each an EQ Acoustics Spectrum Trap 50 and 50L are positioned, resting against the corner (leftovers from my vocal booth treatment). In the north/east corner one baby and two full stacked Hofa bass traps are positioned, in the other north corner my vocal booth is usually positioned when recording drums or not being needed otherwise. (It’s an old 1x1m wooden indoor phone booth modified with lots of broadband absorbers)

The gap between the suspended ceiling and actual ceiling is completely stuffed with rockwool.

The sound

The linear RT is at about 0.35s. It’s quite persistent across the audible spectrum, only below 50 Hz there are still a few bumps (about 0.7s). Schroeder frequency thus is at about 100 Hz.

Now, from a measurement point of view the room actually is quite good already, so what am I looking for? When mixing my drum recordings, I feel like I still have to rely on the direct microphones too much since the overhead and room signals still feel a bit too muddy in the fundamental area, and a bit too washy in the higher frequencies, and though being a bit washy, could still be somewhat brighter. So, it is kinda hard to get an organic drum sound right out of the box. Also, that’s kind of what you perceive when you play drums in there. A bit muddy, a bit washy, and a bit too dark sounding.

As a comparison, my control room theoretically has an only slightly shorter RT (0.3s), but it still feels a lot drier and much more direct in there. (Of course there’s also a lot more stuff standing around, like a couch in one corner, a big cabinet in the other, etc…) Usually I would tune the drums in there since it’s easier to hear the details. Also, there the fundamentals would feel more like “into your guts”.

You could say, at the moment my live room sounds quite broad in the low frequencies and gets more narrow with increasing frequency, whereas I’d like it to sound tight/narrow/compact in the low frequency area, getting broader/wider/livelier as you go up in the frequency range.

Apart from that, I would generally like to improve the live room as much as possible in terms of perceived size, or make it sound as large as possible with what space I actually have available.

Solutions(?)

Now, with these perceived problems in mind, I came up with a few ideas:

1. Bass trapping / LF absorption.
Even though the RT for lower frequencies in my live room is (according to measures) far from being out of control, I suppose there is still some treatment necessary in order to get it sounding more tight and punchy in the fundamental area. However the question remains, when treating the LF area, will I have to focus on that RT bulge below 50 Hz or more generally anything below 100 or 200 Hz? And does it make any sense at all?

2. Diffusion.
It’s said to have the virtue of making rooms sound bigger than they are. Since that’s something I’m generally trying to accomplish, I’d suppose the more diffusion the better? However – given the already short RT of my live room – I’m unsure wether diffusion will actually be able to accomplish anything at all beyond a certain level, since I’m practically only dealing with a couple of early reflections here.

3. Increasing the RT for higher frequencies.
In case that’s possible at all. Since my ceiling is completely covered in absorbent material (rockwool, acoustic tiles) I thought there might be some potential to re-add some more reflective properties to it, without losing any of the LF absorbent abilities. There are a couple of T-Fusors on it already, but they cover no more than 10-15% of the overall area of the ceiling. And to be honest, I’m a little skeptical about their overall reflective abilities.
So, the question here is, with the ceiling as it is, is it possible at all to make it more reflective to any frequency above, let’s say 500 Hz and still have it dampen everything below (as good as it possibly can)? For instance, like covering it with a thin layer of plywood or a thicker layer of painted Styrofoam?


I hope you guys can help me in sorting out those issues. I’ve done a lot of research in the past few days (and generally whenever I had some spare time in the past few years), still I’m absolutely no expert in room acoustics. So, before I go out wasting a shitload of money on futile measures, I’d really appreciate some qualified counsel in this matter. Either by elaborating on those ideas I came up with, or – in case they are nonsense or simply past the perceived problems – helping in finding other solutions and/or the real culprits. Maybe I'm even only chasing ghosts and am so worked up about it by now that I'm simply imagining things. In that case, feel free to knock me back to my senses...

In case any more data or information is needed, just let me know. I’ll gladly provide them asap.

In case this post is in any way not conforming the rules and guidelines, I’d also appreciate to know. It’s a really long post, so please bear with me if anything slipped past me. Also, I wasn’t sure wether this topic fits more into the “acoustic” or “studio design” board. Feel free to move it if necessary.

Last but not least, find attached some pictures of the room. For the audio measurements, this dropbox link will have to do, since it won't let me upload the mdat file:
https://www.dropbox.com/s/ueewh02v5eesc ... .mdat?dl=0


Let me already say thank you for the help I am hopefully going to receive from you people. I am truly grateful for anything that's gonna help me progress in any way!

Hey there "Mr.Harmony", and Welcome!

That's a nice sized room, so it should be possible to get it sounding good.

For the audio measurements, this dropbox link

I looked at your REW data, but frankly, it doesn't make any sense! Either there was a problem when you did the calibration, or your sound card is totally shot and you need to get a new one. But it's a Fireface, so that's unlikely....

The graph for your sound card is showing huge peaks and troughs, across a range of about 15 dB, is terribly non-linear, and rolls of enormously below about 100 Hz. It also has major ringing, and non-flat decay. It doesn't look like a sound card loop-back at all. It looks like something acoustic.

If your sound card calibration is no good, then none of the other data in the REW file is trustworthy.

The second data set in your file, "Sp E - Mic W - Aim W", is even more curious: Frequency response is reasonably flat, except for some minor variations of a few dB, sort of like you'd expect from a mic, but it also shows acoustic artifacts, such as decay times, ringing, etc. So it cannot possibly be a mic calibration file, and the description says that it was a test dome in the room, with the speaker to the east and the mic to the west, both about 1.5m above the floor, etc. But the frequency response most certainly isn't from a real room! No room is that flat. This is the flatest room I'm aware of: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 and that took a major effort!

The other graphs might show something, but it's impossible to say what they show, since my confidence that the data is valid, reliable, and accurate, is pretty close to zero.

So let's first try to figure out why you are not getting good data from REW, then we'll talk about the room.

First, what mic are you using for these tests? How did you have it set up?

Second, please explain how you did the calibration procedure. Did you follow exactly what the REW manual says, step by step?

Third, did you also calibrate REW using a good quality hand-held sound level meter? That's important too, even though the manual downplays it a bit. In reality, for those of us sitting around the other side of the world from your room, it is important to be certain that a data point in your file that appears to be at 81 dB, really is at 81 dB, rather than something entirely different.

Forth, what speaker did you use to do those tests? (Make and model). How did you set it up? You mention some basic info on that, but not enough to be useful.

OK, now for the room itself:

The linear RT is at about 0.35s. It’s quite persistent across the audible spectrum, only below 50 Hz there are still a few bumps (about 0.7s).

I wouldn't be too sure about that, since the validity of your REW data is highly questionable at present. Also, your IR data does not seem to be any good. There's a lot of sound BEFORE the impulse, which is really hard to explain if you had things set up right and calibrated right. The impulse would have to travel backwards in time to achieve that...

The linear RT is at about 0.35s. It’s quite persistent across the audible spectrum, only below 50 Hz there are still a few bumps (about 0.7s). Schroeder frequency thus is at about 100 Hz.

Schroeder frequency is a function of room dimensions. I'm not sure how you came to the conclusion that it would be 100 Hz for your room based on decay times.

I feel like I still have to rely on the direct microphones too much since the overhead and room signals still feel a bit too muddy in the fundamental area,

Very useful information! How do you set up your overheads and room mics, typically? Maybe you could do a rough sketch of the room, showing where you normally set up the drum kit, which way it is oriented, where the treatment is that you mentioned, and where you set up the mics, normally.

a bit too muddy in the fundamental area, and a bit too washy in the higher frequencies, and though being a bit washy, could still be somewhat brighter. So, it is kinda hard to get an organic drum sound right out of the box. Also, that’s kind of what you perceive when you play drums in there. A bit muddy, a bit washy, and a bit too dark sounding.

Which makes me even more suspicious of the REW data! It's not showing what you are hearing. So either there's an equipment issue, or a setup issue, or a calibration issue.

As a comparison, my control room theoretically has an only slightly shorter RT (0.3s), but it still feels a lot drier and much more direct in there.

Please do a REW test for your control room too. Set up the mic in the mix position, on the room center line, angled upwards at 60°, with the tip 47.25" above the floor. Make sure your entire signal path has flat EQ and no dynamics applied anywhere. Totally clean path.

300ms is a bit long for a control room, unless it's quite large. How big is it?

(Of course there’s also a lot more stuff standing around, like a couch in one corner, a big cabinet in the other, etc…) So your control room is asymmetric?

Do three tests with REW: One with just the left speaker running (unplug the right speaker), one with just the right speaker running (unplug left) and one with both running: When you calibrate REW here, make sure that you are getting a real level of 80 dB from the left speaker alone, and also 80 dB from the right speaker alone. Do not change any settings between tests.

Solutions(?)

Now, with these perceived problems in mind, I came up with a few ideas:

I would leave of looking at solutions until we can first identify the problems! What you are hearing and what REW is showing don't see to jib very well...

I’d suppose the more diffusion the better? However – given the already short RT of my live room – I’m unsure wether diffusion will actually be able to accomplish anything at all

Diffusion can be good for delay times, for "liveliness", for "air", precisely because it does not remove energy from the room like absorption does. The energy is re-directed, perhaps shifted in time/phase, but still in the room, still moving around.

I’m unsure wether diffusion will actually be able to accomplish anything at all beyond a certain level, since I’m practically only dealing with a couple of early reflections here.

Early reflections with respect to what and what? "Early reflections" is a concept related more to control rooms than live rooms. It refers to acoustic energy that arrives at the mix position within the Haas time, not coming directly from the speakers, and not diffuse. In a live room, there's no concept of "mix position" and "speaker position", and no concept of Haas time either, since that's a psycho-acosutic effect. Please explain what it is that you are referring to, that you though was early reflections.

3. Increasing the RT for higher frequencies.
In case that’s possible at all

Yes it is possible, by reducing high frequency absorption in the room, hopefully without affecting low frequency absorption.

Here's three graphs from a very small drum booth that I'm in the process of tuning right now, for one of my customers:
The top one is the empty room, before treatment. You can see that the high end is dead. The second one is after a few pieces of treatment went in, where the high-end is a bit too live. The third one shows the next stage in treatment, where things are coming under control nicely. You can see that both the low end and the high end are coming together well. Next up is the mid range, which we are working on now, and is actually the hardest of all to control in a live room.

But anyway, there's the answer to your question: it very definitely is possible to increase top-end decay times considerably in a room that lacks high end.

So, the question here is, with the ceiling as it is, is it possible at all to make it more reflective to any frequency above, let’s say 500 Hz and still have it dampen everything below (as good as it possibly can)?

Yes. Not easy, but possible.

So the first order of business is to sort out the issues with REW, get it calibrated correctly and used correctly, so we can see what the real issues are in the room. Then we can start thinking about treatment.

- Stuart -

Hi Stuart!

First of all, thanks a lot for your time and effort.

As you mentioned, let's make sure the measurements are trustworthy first.

The graph for your sound card is showing huge peaks and troughs, across a range of about 15 dB, is terribly non-linear, and rolls of enormously below about 100 Hz. It also has major ringing, and non-flat decay. It doesn't look like a sound card loop-back at all. It looks like something acoustic.

In fact, it was something acoustic. I did follow all the steps in the calibration process, simply had it wired all wrong. Got confused with the loopback, timing reference and so on... Sorted it out, so know at least the soundcard calibration should be correct!

First, what mic are you using for these tests? How did you have it set up?

I am using a Beyerdynamic MM1. The setup you can actually see on the pictures in my first post. About 1m away from the room center clipped to a boom mic stand facing straight upwards. Height is about 1.5m above ground

Forth, what speaker did you use to do those tests? (Make and model). How did you set it up? You mention some basic info on that, but not enough to be useful.

KS Digital ADM30. I own a pair of those, and for the tests I placed one of them on the speaker stand you can see on the pictures in my first post. (height a little less than 1.5m above ground) The only variable in those tests was the orientation of the speaker. (Facing each wall respectively) Position of mic and speaker itself would remain the same.

In case there is a more sophisticated way to get expressive data about the room, let me know. Like, if there are clearly defineable hotspots for speaker and mic. Since it's my first time working with REW I figured chances would be high I screwed up somewhere along the way, so I didn't worry too much about changing speaker and mic position, yet. Also, I wasn't able to find any significant information on how to properly measure a live room.

The second data set in your file, "Sp E - Mic W - Aim W", is even more curious: Frequency response is reasonably flat, except for some minor variations of a few dB, sort of like you'd expect from a mic, but it also shows acoustic artifacts, such as decay times, ringing, etc. So it cannot possibly be a mic calibration file,

Neither do I own a calibration file for my microphone (just a calibration chart), nor were any of the measurements supposed to be a mic calibration. Since my "soundcard" calibration was an actual acoustic signal with the exact same setup as the data set you mentioned, that might explain why it is so flat. But since I obviously screwed up, let's simply forget about the first round of data sets I'd suggest.

Aside from that, since I do not own a high end measurement microphone, will a calibration file for it be imperative for the kind of measurements we're performing? I think I read somewhere that I can reqest one directly from Beyerdynamic if necessary. I could also upload a picture of the calibration chart in case it helps you in any way.

Second, please explain how you did the calibration procedure. Did you follow exactly what the REW manual says, step by step?

Just to get sure I got it right this time, I can explain how I did it now:

I connected the time reference output to the loopback input as designated in the preferences.

For the soundcard calibration I connected the cable I would use to feed the test signal into the speaker and directly connected it to the cable connected to the microphone. So now, the signal that would go into the speaker goes straight into my interface's mic preamp as designated in the preferences.
When the test signal is played, I made sure all the levels (input and output) are pretty much the same level.

For level calibration, I reconnected the speaker and the mic to the signal chain. I had the speaker reference signal played and adjusted the mic preamp so that - again - all levels were the same as good as possible. After that, I used the SPL Meter tool, again had the test signal played (calibrate), went into the live room with my handheld SPL meter (same settings as the software tool, i.e. slow and C weighted) and adjusted the level of the software meter to what my analog meter showed (again, as good as possible)

Third, did you also calibrate REW using a good quality hand-held sound level meter?

As mentioned before, I own a hand-held SPL meter. It wasn't too expensive, though. (something about 100,- € if I remeber correctly) However, a local engineer at a venue I worked at once had a standardized reference signal generator at hand that we used to test it. Turned out it was less than 1 dB off target. Maybe even less than 0.5, my memory's a little blurry. But definately no more than 1 dB, so I'd say it's trustworthy enough for what we are doing here.


Now, hopefully this calibration process sets a proper foundation for more trustworthy measurements.

I've attached a picture so you can actually see the setup of the measurement. I've also run the entire test with my RME Babyface, in case there really might be something wrong with my main interface. I've also included two sound samples of me clapping inside the room, and hitting a kick drum so you can actually get an acoustic impression of what we are talking about here and better relate the measurement data to the room itself. Again, I won't completely rule out that I've just become over sensitive. I've used that room for drum recordings for about 4 years now and I rarely have to work with "foreign" drum recordings or record drums anywhere else myself. Maybe I just got stuck in a rut, so take the sound description of my first post with a grain of salt.

You'll find the new data sets here:
https://www.dropbox.com/s/o6e34zrc7oxh0 ... .mdat?dl=0

I'll answer all your other questions once we can be sure the measurement department works correctly and the data sets make sense. It'll be easier for me to focus on those questions once I can get this topic out of my head.

best regards,
André

Sorted it out, so know at least the soundcard calibration should be correct!

I am using a Beyerdynamic MM1.

KS Digital ADM30

In case there is a more sophisticated way to get expressive data about the room, let me know. Like, if there are clearly defineable hotspots for speaker and mic.

OK. I'll get to that below...

since I do not own a high end measurement microphone,

Yes you do! The MM1 is a pretty fine mic.

will a calibration file for it be imperative for the kind of measurements we're performing?

For this type of thing,not really necessary. We are not going for high precision here, since it's a live room. The MM1 is pretty flat anyway, so the slight variations between mics isn't going to be a big issue here.

I could also upload a picture of the calibration chart in case it helps you in any way.

Sure, that would be good.

I think I read somewhere that I can reqest one directly from Beyerdynamic if necessary.

It's worth asking them at least. If there's any cost involved, then forget it, but if they can just e-mail you the file at no cost, that would be perfect.

Again, I won't completely rule out that I've just become over sensitive. I've used that room for drum recordings for about 4 years now and I rarely have to work with "foreign" drum recordings or record drums anywhere else myself. Maybe I just got stuck in a rut, so take the sound description of my first post with a grain of salt.

On the contrary, if you aren't happy with it, then it's not good! It's that simple. Your live room is supposed to sound the way YOU want it to sound, and if you aren't getting that sound, then it should be fixed, if possible. Control rooms are different! The MUST be neutral, and meet exact specifications, but live rooms should have the tone and character that the owner wants.

OK, speaker/mic placement:

Testing a live room is rather different from testing a control room. With a control room, the positions for the speakers and mic are rather obvious. Not much choice! But for a live room, there's no obvious "correct" location at first glance, since there's no "correct" speaker position and no "correct" mic position.

However, there are two "hot spot" measurements that you can do that will reveal something about the room.

First, set up the speaker on the floor pretty much right in one of the corners (it doesn't matter which corner), then set up the mic in the diagonally opposite corner: in other words, right up near the ceiling in the corner that is furthest away from the speaker. Don't put the mic tip pressed into the actual corner: keep it a few of inches away. You'll need a tall mic stand!

With that setup, you are looking at the modal response of the room. All modes terminate in room corners, so having the speaker in one "down low" corner will trigger as many modes as possible, and having the mic in the opposite "up high" corner means that it is "seeing" as much modal activity as possible. The FR graph will be wildly bassy, with major rise in the low end... This is pretty much the "worst case" situation, which is exactly what you want.

Second, set up the speaker roughly in the middle of the space that the drum kit would normally occupy, sort of roughly in the middle between where the snare and rack toms would be, and facing forwar (pointing the same way the kick would point).

Do two tests here: First set up the mic in the location where you'd normally have your distant room mic when you are recording drums, and second set up the mic roughly where the drummer's head would be.

All of the above tests together will provide a useful acoustic "picture" of the room.

I'll take a look at your REW data tomorrow: it's nearly 3:00 AM here, and I'm too tired to be able to do anything intelligent with it!


- Stuart -

Ok, so here are the new room measurements done following your instructions:

https://www.dropbox.com/s/99j107zt8mgac ... .mdat?dl=0

Just a few notes here. On the pictures I uploaded you can see a drum carpet. That is where I usually set up the drumkit (pretty close to the south wall), facing towards the north wall (i.e. the control room). I also added measurements with the mic in my usual overhead position and had the speaker also face in the exact opposite direction (i.e. the south wall) for the overhead and drummer position, since I was also curious about the reflections of the wall behind the drumkit.

Furthermore, I chose two different locations for the room position of the mic, since I changed that position not too long ago. The old position was rather close to the north wall, pretty high and directed in the drumkit's direction, whereas the new position is pretty close to the drumkit, near the center of the room, but facing away from the drumkit so I could better blind out the direct transients of the drums. (I am using cardioid mics for the room signal)
Of course, the directional effect of my room mics is pretty much eliminated by the omni pattern of the measurement mic. Not sure if that is of any importance, but I thought I'd mention it.

All measurements were done with the speaker on a stand (about 0.8m above ground) and on the floor, so we could get an impression of how much the actual height of the shells might influence the room response.

I'll try to gather the data of my control room you asked for later this evening and answer a few more question of your first response. I hope the current data set is of any use.

So until then,
best regards,
André

Hey Stuart,
finally came down to answer your remaining questions...

Schroeder frequency is a function of room dimensions. I'm not sure how you came to the conclusion that it would be 100 Hz for your room based on decay times.

One of my sources you can find here:
http://trikustik.at/raummoden-rechner/

For the given dimensions and a RT of 0.37s, according to to this calculator, the Schroeder frequency is 119Hz. The other sources I found concerning Schroeder frequency also stated that is was a combined function of room volume and RT, not just room dimensions. (The formula being 2000 * SQUAREROOT{reverb time / room volume} )
I will admit, intuitively I also would have suggested that the schroeder frequency depends on room dimensions alone, so if I'm getting anything wrong here, please correct me!

How do you set up your overheads and room mics, typically? Maybe you could do a rough sketch of the room, showing where you normally set up the drum kit, which way it is oriented, where the treatment is that you mentioned, and where you set up the mics, normally.

Find a sktech of my usual room setup, and some files picturing my overhead mic setup below. When I began recording, I used a AB style technique for setting up the OH mics. (As described in John Sayer's recording handbook) For a few years now, I've been setting them up in this ORTF-similar pattern, partly facing away from from the south wall, not straight downwards. Ever since, the sound of my overhead tracks slightly improved (less washy), which I assume is because the mics (cardioid pattern) are now experiencing less coloration from the reflections coming from the south wall (being directed slightly away from it)

Early reflections with respect to what and what?

In respect to how reverb is "composed" in reverb software (or plugins), or how behaviour of sound in a room is usually described in many sources. For a sound event inside a room, the first couple of reflections are usually refered to as "early reflections". In reverb software the "early reflections" part of the algorithm will define the "character" of the space you are modeling to a great deal, and its duration can take up to a few hundred milliseconds.
That's how I came to describe the reverb of my room as only consisting of a couple of early reflections, since the reverb duration of the live room is pretty short and it doesn't sound like your "typical" reverb tail that most people would most likely associate with the term "reverb".

Please do a REW test for your control room too.

Finally done. You can find the data here:
https://www.dropbox.com/s/wre3liqbhssp3 ... .mdat?dl=0

300ms is a bit long for a control room, unless it's quite large. How big is it?

It's the same size as my live room:
Height 3,10m
Length 5,40m
Width 6,10m
Also, the same kind of ceiling construction, with rockwool stuffed in the gap between real ceiling and suspended ceiling.

So your control room is asymmetric?

Well, my work desk is set up symmetrically, right at the plasterboard wall around the center axis of them room. (As you can see in the data, this is actually causing some issues in the bass response of my listening setup, but I've found a temporary solution to that. Also, I'd consider this a matter for a seperate topic) Apart from that, my control room is furnished asymmetrically, yes. This is simply a compromise since I have only those two rooms available and my control room needs to serve not only as mixing environment, but also as a general lounge area for clients if necessary. So, there's a living room suite in one corner, a kitchen unit in the other, a big cabinet at the wall behind my work desk, my electric piano left of my work desk and a dining room table (for up to 6 people) right of my work desk.

I'm well aware that all this is far from being optimal is regards to control room design. Nontheless, it's a very comfortable working environment for both me and my clients (which I consider at least equally important to the sound). And since - with that temporary solution I mentioned - I'm able to deliver absolutely satisfying results in my current listening environment, this is simply not a top priority to me at the moment.
Can my control room still be optimized? Absolutely!
Does the quality of my productions gravely depend on it? At least I don't feel that way.
I am more unhappy with my live room at the moment than with my control room, that's how I came to inquire you folks about my live room first.

Now, as a short update, I've had a drum recording session two weeks ago and I used that chance to experiment with a few ideas I had in the back of my mind. The one with the most significant result was, leaving the door to my live room open and placing a mic at each end of the hallway (overall length about 50m). For one, it sounds awesome, and two, I now know that the kind of sound I would personally like to achieve in my drum recordings cannot be achieved with my live room alone. It is most likely too small to be able to create such a long reverb tail on its own.

Nontheless, that doesn't mean I want to leave things as they are inside the room. Maybe it doesn't get me where I want to be all by itself, but I'm sure there's still potential for it to further enhance the drum sound.

I know it's not wise to talk about potential measures before analysis of the REW data, regardless I'm quite sure that my live room can benefit from some additional diffusion for sure. You see, when it's almost empty, there's still a rather short, but clearly audible flutter echo. It usually won't occur once the drums and all the mic stands are set up, though. But I'd interpret that as an indication, that middle and high frequencies can still be "distributed" somewhat better inside the room.

Awaiting your opinion on that...

P.S. About my measurement mic, the calibration chart is attached as a picture. Still waiting for response on the manufacturer's calibration data.