New "home" Mastering Room

[Mark Fuller]

Hello folks,
Will do my best to post properly according to this great forum's rules.
I've been lurking for a couple months and have benefitted greatly.
Thanks to all for the knowledge and experience shared!
And to the admin's please let me know if I've screwed up or need to post this in a different area of the forum.

My new living space allows me to have a control room, messy/incomplete as it is, pictured in the attached photo.

Top Left-mix position
Top Right- right front corner
Bottom Left-left front corner
Bottom right-the (odd) ceiling

I do tons of mastering and a bit of mixing. I'm well aware that this is no "proper" room, nor do I have gear along the lines of the bigtime places. Done enough music production in my life to know very well what I don't have.
That said, I'm getting quite a bit of work, especially mastering, and have to get things as good as I can, all things considered.
I've attended numerous top-flight mastering sessions for clients as well as spending years tracking and mixing in excellent studios. For what it's worth I'm not approaching this stuff with complete naivete. But it is what it is.

I can throw a few hundred bucks into treatments every month. Serious construction can't happen. It's a rental.

The dimensions:
17'3" Wide
13'3" Length
8' high

It's within the Bolt area according to the amroc-room mode calculator.

The room has an outdoor type carpet over cement, no pad. Wood paneling on walls looks like the classic attorney's office. It covers everything. Inside the walls is R15 fiberglass. They're certainly not at all stiff, too dense or inflexible, so can absorb some low-freq's. And resonate (though I don't perceive it working as I commonly do, without subwoofers, around 80 DB).
None of the walls are identical.
From the mix position: there's a window to the left, a door on the front right, door to the right rear and bookshelf across the left 2/3rds of the rear wall.
Lower right pic you can see the rectangular areas on the ceiling. Max height is 8' but the edges of the rectangles come down to 7'7". There are 8 of those rectangle things arrayed equidistantly across the ceiling.

Presently the tweeters are 38" out from the wall, each are 70" from L/R walls and approx. 42" from the listening position.
I arrived at this position when the room was empty by rolling the speakers around on a cart at the height/width I'm used to.
For the life of me I did not like the sound when facing length-wise with the speakers. Perhaps that was because of the non-symmetry of the wall surfaces, I don't know, but I chose to setup this way purely because I thought it sounded better, theory be damned.
Didn't yet have the mic or REW ready to go, either.
Had tons of work upon moving in and had to setup and get going immediately. Did not have the luxury of time or money in which to linger and setup perfectly. Not ideal, clearly.
Chaotic to put it mildly. And messy.

I went with my ears, built R30 traps and absorbers ( 4-4" thick 2' by 4'. 2 behind the speakers, one in each front corner. 4-2" thick 2' by 4' that I've put in the 4 rectangular spaces in the ceiling above the mix position) from this excellent thread from member studio_drums:
http://www.johnlsayers.com/phpBB2/viewt ... =3&t=10297

There are heavy curtains on the window, a few foam absorbers, minimally, to cut parallel reflections mostly from left to right.
So far I'm really pleased with the room. Clients are pleased. The setting up is nearing completion. I hope.

With all that verbage about my weird little room out the way, I'm hoping to get some interpretative advice on the REW pics attached. (the .mdat is too big to attach but I could email it if someone wants to look)

I got the Behringer mic (ONLY piece of Behringer gear I've ever owned) and installed REW.

Calibrated my Lynx AES16 card. Ecm8000 upright where the center of my head would be, good SPL levels (about 78 db in the room), clean mic level.

The freq graph and waterfall, as best as I understand them at this early date, make pretty good sense with how I'm hearing the room. Again, I don't yet have subwoofers and typically work around 78-82 DB, consistantly.

The thing that freaks me out is the phase data. I do not understand it. Like, the whole radical dip around 2.1K - straight down and straight back up.

What the heck is that? I don't hear it though I'm assuming it means there's out-of-phase in those ranges?

With all this info. and the attached pics and file, can anyone hear help me to understand this REW data or assist me in refining how I use the app such that I can dial this room in a bit better?

There are excellent REW tutorials online for it that I've looked over, but still, that phase stuff freaks me out.

Might I appeal to ya'all for comments on all this, as time allows, assuming I've not totally blown it with my first ever post?


Many thanks in advance. This forum kicks ass and is helping me out a ton!

Best!
mark fuller

[Soundman2020]

Hi Mark, and welcome!

Might I appeal to ya'all for comments on all this, as time allows, assuming I've not totally blown it with my first ever post?

You're doing pretty good so far! Great first post, by the way!

OK, about the room: from the very limited REW data you showed, clearly there are several issues in there that should be addressed as much as possible, in order to use it as mastering room. As you mentioned, you are aware that it isn't and won't be a world-class mastering room, unless you invest a lot of money in it, but it still can be better than where it is right now, undoubtedly.

But in order to figure out more accurately what is happeneing in there, I'd need the actual MDAT file: Maybe you could upload it to some place like DropBox, then post the link here?

Again, I don't yet have subwoofers and typically work around 78-82 DB, consistantly

You have a sound level meter, then? Just a quick question: did you use that to calibrate REW before you did the tests?

Also, how did you do the REW test? Which speaker are we seeing in those graphs? (Left or right?).

The thing that freaks me out is the phase data. I do not understand it. Like, the whole radical dip around 2.1K - straight down and straight back up.

The vertical lines on the phase graph are just the way that REW uses to show when it ran out of graph space, then "wrapped" the line back to the top again. That's all. There is no sudden jump there: it's just the way that REW shows it. Take a look at the "jump" at about 45 Hz, and you'll see that the line hits the "-180°" point at the bottom of the graph, then immediately starts again at the top, at "+180°". There is no jump there! It's just showing that the phase shift completed a full circle at that point and is starting again, going around one ore time. Each time it completes another full circle (360° phase shift), then the line "jumps up" again. If you use the "unwrap phase" button on the tools, it then re-graphs that on a much smaller scale, so you can see the overall phase change more clearly, but without much detail. So don't get worried: you are not seeing major phase jumps there: just phase shift passing the "end" of the circle and starting again.

That said, the "double jump" at 2.5 k is likley some issue with the speakers themselves, such as perhaps the crossover point for the tweeter, or something like that.

can anyone hear help me to understand this REW data or assist me in refining how I use the app such that I can dial this room in a bit better?

For a start, set your horizontal scale to just show the range from about 15 Hz up to 500 Hz only, since that is where the vast majority of your issues will be, to start with. We can look at the high end later, but you need to get the low end in order first, before going there. There's no point in fixing minor issues up at 15 kHz, until you solve the major, huge, bloated, sledgehammering issues in the low end.

Then, set the vertical axis usefully too, so you are just seeing the part of the scale that you can actually hear: There's no point at all in looking at -30 dB levels at the low end, when human hearing can't really distinguish much below about +20 dB, even under the best possible conditions! So you are showing 50 dB of useless stuff on those graphs: just concentrate on what you can hear, from about 30 dB up to about 90 dB.

And finally, since it is a small room and seems to be rather dead acoustically, shorten your time scale (Z axis) on the waterfalls to show the most pertinent part of the room decay. There's no point in showing 500ms of data that you can't hear, if it all decayed below the hearing floor after about 250 or 300 ms.

Looking at it like that will give you a much better view as to what is really happening in the low end, so you can figure out how to treat it.

If you post the MDAT file, then I'll try to take a look at it and see if I can figure out something.


- Stuart -

[Mark Fuller]

Soundman,
thanks a ton. Already clearing up some issues for me with the phase stuff.
I don't know where my A20's crossover. Re. 2.5K, they sound in this room like they've always sounded.
In fact, part of what I love about these speakers is their fantastic, to me, accuracy in the 1.5-4K regions.
The room is dead-ish in terms of decay but it's brighter, say above 1.5K, than my previous space. I'm liking that part of the room from the get-go.

Here's the mdat:
https://www.dropbox.com/s/tiav2j8us8wru ... 0hung.mdat

I don't yet have an SPL meter. The NHT amp shows DB levels. I realize seeing level at output doesn't reflect the room's characteristics, but that's what I used to calibrate the SPL settings in REW. It's also been very close to SPL readings I've done in the past, though not in this room.

Do you think an SPL app on an Iphone is sufficiently accurate?

Also, and maybe I screwed up, I centered the mic at listening position and REW's measurements were from both speakers at the same time.

Is this incorrect to do both at once?

I'm out of town from Th-Sun so if I'm slow to respond that's why.

And then I get back and get hammered with 4 or 5 albums in a couple weeks.

best,
mark

[Soundman2020]

Re. 2.5K, they sound in this room like they've always sounded.

Right: that's what I meant when I said it's a speaker issue, not a room issue. But in reality there's nothing there at all: unwrapping the phase just shows typical phase shift.

In fact, part of what I love about these speakers is their fantastic, to me, accuracy in the 1.5-4K regions.

I'm not seeing that on the REW graph. This is what it is showing for that range:

markfuller-1k-10k.jpg

Not terrible, but not that accurate either.

Here's a similar graph for a room I'm working on right now with Genelc speakers:

rmo-1l-10k.jpg

You can see the difference. In your case, there's a sudden large jump in SPL from around 65 dB to around 55 dB, centered around 4kHz. In the other case, the response varies fairly smoothly around 75 dB across the entire region, with no sudden jumps.

It's hard to say if that is a speaker issue or a room issue, but I'd suspect it is speaker related at such a high frequency.

However, it might also be related to the way you are conducting the tests: You are doing them at a level that is far too low (assuming your SPL calibration is valid, which is also doubtful). You did mention that "the NHT amp shows DB levels", but from what little I can find on-line about that amp, it actually doesn't show the real levels in the room: it calculates what it thinks the levels should be, based on what it is feeding to the speakers. It's not even clear if it is calculating for "A" weighting, "C" weighting, flat, or something else. But what is clear, is that REW is not calibrated correctly, so you are going to need a proper hand-held SPL meter to do that. They aren't too expensive: around US$ 100 for a decent one on Amazon or eBay.

An iPhone app will not do the job either: the mic on the phone itself isn't omni, does not have flat response, and was never designed to be used as an acoustic measurement mic. It can give you a very rough idea, at best.

There's also an issue with the way you did the soundcard calibration procedure for REW: It's pretty hard to believe that your soundcard has absolutely flat response from 2 Hz to 21 kHz! So you should re-do that calibration as well, following the procedure in the REW manual.

Once you have the calibration issues sorted out, then do the tests again, but this time at a level of at least 80 dB SPL, "C" weighting, measured at the same place where you have the measurement mic. The tests you did here seem to have been done at a level about 100 times lower (around 60 dB). It's important to do the testing at the right level.

Also, please do three separate tests: one with just the left speaker on, one with just the right speaker on, and one with both speakers on. That is also important. Some of the stuff in the graphs right npw might be due to interference between the two.

It also seems that the room is very noisy just before you ran the test, as the impulse response is showing a lot of garbage just before the peak: Please make sure that the room is as silent as possible for several seconds, just before you click on the "Start measuring" button. Even better: Set the "Start delay" time to 30 seconds, click the "Start measuring" button, then leave the room as fast as you can, and close the door: then wait for the test to run and fully complete, before going back in again.

Having said all that, there's still enough data in there to see that the room has modal issues on the width and height axial modes, as well as a few others, and it also looks like you have the mix position set up poorly in the room, or the speakers set up poorly (or both), as there seem to be some SBIR issues. What do you have in the room right now for bass trapping? I don't see any significant bass trapping in the photos you posted earlier...

Also, and maybe I screwed up, I centered the mic at listening position and REW's measurements were from both speakers at the same time. Is this incorrect to do both at once?

You do need the "both" test as well, but it's important to see how each individual speaker is doing as well, since they can mask each other if they are on together, or the interference patterns in the room can produce misleading results. So test the individually first, then both at once.

Overall, there are some pretty big low-end issues in the room that need treating urgently: I doubt you'd be able to master accurately like it is right now: there's a major dip at 112 Hz, a smaller one at 90, then large peaks on either side of that, at 62 Hz and 137 Hz.

Fortunately, it looks like a lot of that can be cleaned up with good treatment, and your room can be made much more accurate than it is right now.

- Stuart -

[Mark Fuller]

Hi Stuart,

Thank you. Good stuff.
I'll work to get a proper SPL meter after this weekend away.

As for bass trapping, Just the 4, 4" 2' by 4' 703 panels, 2 on the wall behind the speakers and one in each front corner.

I should say it's all OC 703 fiberglass panels, not R30 as I put in the original post.

There's also a couch along the left wall for what it's worth.

Looks like I gots to get the SPL meter, run more test as you suggest and repost.
Might take a week or so but I'm on the case.

Thank you!

[Mark Fuller]

Re-did my REW tests now with a proper SPL meter (Galaxy130) and card cal.
Mdat file here:
https://www.dropbox.com/s/08v8mxu1wcofa ... tests.mdat

Somewhat alarming to see the diff. between hi-mid/highs between the individual channels vs. both speakers.

Stuart?

Thoughts anyone?

Back to work but it's clear there's much to be done to get this room in acceptable shape.

Thanks in advance,
mark

[Soundman2020]

Sorry about the delay in replay, Mark: I'm a bit snowed under right now.

Is that MDAT file still the latest version?

I'm a little confused about what I'm seeing there, as all the SPL curves are at the same level! The Left and Right curves should be at the same level, but the "Both" curve should obviously be 6 dB louder. Did you adjust the levels between tests? If so, that's a mistake. Run the tests without touching ANYTHING at all in the signal chain, except to turn off the left speaker for one test, and the right speaker for the other test, then leave them both on for the final test. Apart from the power switches, do not touch anything on the console, interface, or in REW itself.

Anyway, apart from that the L and R curves are reasonably close: not too much difference between them, except in the low end which is to be expected anyway, until the room is treated.

Somewhat alarming to see the diff. between hi-mid/highs between the individual channels vs. both speakers.

Not a problem: That's probably due to cancellation at the exact mid point of the room where your mic is, but your ears won't be there: Try turning the mic slightly left, until it is in the location where your left ear will be, and is also pointing directly at the left speaker, then run a test like that with both speakers on. Then turn the mic again to point at the right speaker in the right ear location, and do another test with both speakers on. The traces should be a bit better like that.

I'm also a bit confused about the IR graphs: That room seems to be rather noisy, as there's an increase in background noise just before the start of each test: Are you running these tests from outside the room, with REW in the automatic delay mode? If not, then try doing that.

Also, you don't have any subs in there right now, do you? Your speakers do not seem to be triggering the low end very much right now, so try increasing the level by about 6 dB for the next test. Right now you seem to be doing the test with a level of around 80 dB for each speaker, which is normally OK, but since your speakers don't seem to go down very low, it might be an idea to boost that a bit, to get a better idea of what the low end is doing.


- Stuart -

[Mark Fuller]

Hi Stuart,
Thanks for looking and yes, I'll redo the test asap. Buried in work, a good thing, but not time to rig the rig and test again. Soon.
Gee. Don't know what would cause the level drop with both speakers. Definitely didn't touch anything save a mute on one side or another, or neither.
Anyways.. will do again.

[Mark Fuller]

mdat here:
https://www.dropbox.com/s/2ntueyo52ztmy ... .mdat?dl=0

[Soundman2020]

There's something seriously not right with that one, Marc!

First, it only goes up to 320 Hz, but we need the full spectrum (20 Hz up to 20000 Hz).

Second, it only has one single measurement, but we need all three tests: Just left speaker, just right speaker, and both speakers together.

And third, there seems to be some type of noise signal superimposed on top of the actual SPL signal: maybe some type of hum or buzz?

So that test isn't much use, fortunately.

- Stuart -

[Mark Fuller]

https://www.dropbox.com/s/65u8n6uhhsm1u ... .mdat?dl=0

For god's sake one would think I could get this right.

Let's try the above.

[Soundman2020]

Hey Mark, I'm not sure how I missed your reply for so long (!) but I finally found it again, and I downloaded your data. It's valid! It all looks good... except that it's about 15 dB too high... (Did you calibrate REW with a sound level meter, and do your tests at 80 dB?) But it's good enough to see what's going on with your room: tests from both speakers separately, plus both together about 6 dB higher.

The graphs are showing the type of curve that is typical of small rooms without enough bass trapping, so I'd concentrate on that. I'd do a few really large bass traps in the corners where you have the small ones right now: make them floor to ceiling, "superchunk" style, and about 24" to 36" across the front. I'd also try to get some more absorption up against the ceiling, in addition to the clouds you have there already.

Try that, do another REW test, and we'll see how its going.

- Stuart -

[Mark Fuller]

Thanks, Stuart,

I've been planning pretty much what you suggested although I also want to concentrate bass trapping in the left, rear corner as well.
Waiting for funds to be available plus get a minor shoulder surgery done for a bone spur so I can do stuff above my head.

In any case the room is working well. I got subs at long last but am typically working with the entire system in the range of 80 db, 82 tops. The low-end doesn't go nuts at lower levels, which as you suggest I test again 6 db down, would probably offer an improved response in that low area.

Anyways, I'll post and message you when I'm able to get more materials installed and do another round of testing.
Thanks for keeping tabs on this project!

mark

[deckbuilder]

hey Mark. great job mate. i Really appreciate this effort. it really helps me a lot. m also planing to have the same thing

[Mark Fuller]

All good, deckbuilder,

I've just done simple things I've found posted by users here at the Sayers forum. Stuart's advice has helped dial me in, as well.
I'm finding that between being busy and, the amount of money/time I can throw at the room, I'm having to go slower than I initially would have liked.
It's turning out to be a good thing. I learn the room more and more, move furniture around, listen to tons of different material.
My next round, basically as Stuart suggested previously with more clouds, most substantial traps in the front corners, will really help a lot and will be more effective now that I've spent so much time working and listening in here.

I'll definitely post pics and updates when the next batch of work happens. Hopefully by mid-January.

Cheers!