# Question about mixing room treatment



## trifidmaster

Dear Bryan, dear forum members,

Here is a sketch of my room/mixing room.
The measures are in cm.

The walls are plastered bricks (appr. 1 cm thick plaster), the floor is laminate, the ceiling is plastered concrete (appr. 1 cm plaster),
The window is double glass, the door is massive wood.

Q1: I would like to ask you how should I treat it for mixing purposes?

Q2: What decay times are OK for mixing purposes in a studio?
I believe it depends on the frequency.
Could you gens elaborate on this issue, too?










Cheers
Stefan.


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## bpape

Hi Stefan

Face the window for mixing.

Treat the front 2 corners floor to ceiling with chunk style absorbers or at a minimum, 4" thick panels straddling the corners.

2"-3" thick panels directly on the front wall behind the monitors for boundary bass issues (SBIR)

2" reflection panels on the side walls

4" panels on the rear wall centered behind the mix position

Depending on room height, either 3-4" panels overhead to deal with height modes or diffusion if the ceiling is higher.

Decay time does vary across the spectrum depending on room size, room usage, etc. Other things to consider are:

Room construction
Amount and type of furniture
Number of people

In this room for this usage, I'd shoot for about 1/4 second in the 125Hz range gradually tapering down to around 140ms or so by the time you get to 4kHz. What I've described above is general treatment for specific issues and will get you close to this though some additional broadband bass control may be required.

Bryan


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## trifidmaster

Hi Bryan,
Thank you very much.

Should I also consider the 38% sitting rule from the front wall?

Cheers
Stefan.


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## bpape

Generally that's a good place to start but it's not a hard and fast rule. Usually, seated ear position ends up being best somewhere between 33 and 38%

Bryan


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## trifidmaster

Thanks a lot!

What densities should I use for the panels?


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## bpape

If you use 4" straddling for the corners, then I'd use 3-6lb density. If doing the chunks, then 3lb is fine. 

Also, once we get this phase done, if you want to potentially do some soffits of some size, a lighter density can be used once you get to about 8" thick or more.

Bryan


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## trifidmaster

Bryan,

Thank you, . I will come back as soon works start.
Note: I have approximately 12-14 m long soffit as well - can be installed if needed.

Stefan.


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## trifidmaster

Bryan,

How far should I place the speakers from each other for the start?

Important note: I do not have the Dynaudio sub anymore, and I have changed the speakers/monitor: now I have Dynaudio BM 5A compacts.
The speakers are on stands.

About the software. What should I use? 

Stefan.


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## bpape

Use Room EQ Wizard for measurements. Free download here at The Shack.

For spacing, hard to say. You just need to play with it. In general, for nearfield monitoring, you'll want them to be as far or slightly farther apart as you are from them.

Bryan


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## trifidmaster

All the furniture/studio equipment is moved into the room.
Sitting position is 38 % from the front wall.
Spekaers are 1.35 m from ech other, seating is 1.35m from the speakers.


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## trifidmaster

untreated room 
and the waterfall


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## bpape

Just for a better look at what's really happening, set your bottom scale to be log, not linear. 

Bryan


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## trifidmaster

OK, here it is.


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## trifidmaster

Here is the corresponding waterfall in log scale


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## bpape

Looking at the waterfall, something is funky around 65-100 Hz. That big blob at the cutoff of 1000ms shouldn't be there with a good measurement. Are you sure you have no electrical noise, no ambient noise, etc. bleeding into the measurement?

Bryan


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## trifidmaster

Ambient noise = only my music DAW setup and the measurement PC is running. These are very quite.
Window and door are closed, and in fact there is no noise outside.
Here we have 50 Hz in electricity - I will re do the measurement, keeping on only the measurement PC + speakers.
The room is very much like a cave.
I have listened to very good records. It looks like the bass is "missing" from the records.

I will post the new measurements in my next post.

Stefan


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## trifidmaster

Bryan,
Here are the measurements.
Blue=both speakers ON
Red=left speaker only
green=right speaker only
I also post the corresponding waterfalls.

I also did averaging measurement (8x) + waterfall
Please note that in the averaged waterfall the ZOOM is different on the Y axes.


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## bpape

The response is actually pretty decent up to 85Hz where we have a hump. The big hump at approx 145 is the one that really concerns me. 

One thing I notice is that the distance between speakers is pretty close to 1/2 of the width of the room - which means that the distance to the side walls is approx 1/4. That may or may not be part of the issue but I have suspicions. How far from the face of the speakers to the wall behind the speakers?

Bryan


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## trifidmaster

Thanks.
Yep, your observation is very correct - I did not think about it. Indeed the distance between the speakers is pretty close to 1/2 of the width of the room (they are approx 1/4 from the side walls).

The face of the speaker(s) is 80 cm from the front wall (from the wall behind the speakers).

I can not put the speakers closer to each other, as I have a table between them. The speakers are on dedicated stands (sand filled stands).

Shall I install the soffit/panels, or...you want me to do more measurements?

Stefan.


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## bpape

Try moving the speakers closer to the front wall and farther apart and take a new measurement.

I'd much prefer to get the things addressed with position that we can.

Bryan


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## trifidmaster

OK - I see your point.
What do you suggest? How much farther apart, and how much closer to the front wall?

The speakers are Dynaudio 5A Compact.

Stefan


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## bpape

That's just experimental. Try 6" back and 6" farther apart for now. We're just testing at this point. 

Bryan


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## trifidmaster

So, 150 cm from each other instead of 135 cm.
and 65 cm from the fron wall isnated of 80 cm.

ohh, just listening to a good record - I think the overall balance is better,
but the measurement will tell = next post.

Stefan.


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## bpape

Better is good. Might still not be exactly right but let's take a look and see what we've impacted. We may still move the seating a bit. 38% is just a theoretical starting point. In reality, the smoothest bottom end generally ends up somewhere between 33 and 38%

Bryan


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## trifidmaster

Bryan,
Speakers are plced as requested;
Here is the response curve.


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## trifidmaster

and here is the corresponding waterfall.
Stefan


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## trifidmaster

On this measurement the green curve is corresponding when seating is 33 % from the front wall.
Waterfall fro 33% seating is also attached
Stefan.


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## bpape

I think the speaker position is better - not great but better. Moving the seating didn't do anything terribly good. Again, please set the scale to be log, not linear.

Bryan


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## trifidmaster

Bryan,
Sorry for the scale;
Here is the 38% response + waterfall;


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## bpape

Are you running a sub and monitors or just monitors? Seems to be a broad dip where the xover would be with a sub setup.

Your 3 peaks appear to be multiples of each other. Try the mic 1/2 between the 33 and 38% but leave the speakers in the new position.

Bryan


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## trifidmaster

Bryan,
No sub - I do not have it.
The Dynaudio monitors are rated only from 55 Hz up to 21 kHz.

So, I am running just the monitors.

The SPL meter is 1/2 between 33% and 38%, here are the curves.


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## bpape

OK. That's worse again so we'll leave the seating at where you had it before. Monitors in the new position. I strongly suspect that the peaks are SBIR related. Panels behind them will help to address that, though it won't deal with the 40hz which I'm not sure why you have it anyway given the response of the speaker - unless you have a resonance at the desk itself.

Bryan


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## trifidmaster

OK. What should I do?


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## bpape

If you have a couple of 2'x4'x3-4" panels, I'd start with those behind the monitors to deal with the boundary issues.

Bryan


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## trifidmaster

Panels are with me. Size: 1m x 0.5 m x 0.1 m, rockwool - density I will check.

Question: How should I place the panels?


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## bpape

1 directly behind each monitor for now.

Bryan


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## trifidmaster

purple curve = without panels
red curve = with panels, 1-1 behind each monitor


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## trifidmaster

and the curves


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## trifidmaster

and the waterfalls, do I see correctly, that with panels the decay times are improved a bit?


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## trifidmaster

Hi Bryan,

Please find below the room layout. The monitors/speakers are placed as agreed.
The seating is at 38% from the front wall.

As suggested, 1-1 panel behind the speakers are placed and are also indicated on this layout.

Please note that the table is rather big (130 cm x 90 cm). The computer screen is also big (relatively).

The center point between the woofer and tweeter is 113 cm from the floor (137 cm from the celining).

Stefan.


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## trifidmaster

No panels are placed. SPL at 2 different distances from floor.


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## trifidmaster

2-2 panels are placed at the back wall-side walls, stradling, so, infact 2 m x 0.5 m panel is in each back corner. One panel is placed on the top of other.
Note: At the back right corner, there is a door, see my room layout.

The 129 Hz peak does not change, but the response is becoming becoming smoother from 143 Hz.


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## trifidmaster

next:
as before (2+2) at the back corners
+ 1-1 behind each speaker.


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## trifidmaster

Next step:
2-2 panels are placed at the back corners
1-1 at the front wall-wall corners, the bottom part of these panels are 1m from the floor.
Picture is uploaded in to the image gallery.


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## bpape

Well, let's see, we've addressed width, height, wall behind, SBIR, etc. and nothing is impacting the hump down low. That leaves either a combination of 2nd and 3rd order modes (which isn't likely due to the various positions). - or - some kind of interaction with the desk itself - or - something in the room itself resonating strongly at that frequency.

For ease of following along, you might want to embed the images in the posts rather than having attachments.


Bryan


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## bpape

He had a problem getting this last one up. This is the current measurement with some treatments in place.

Bryan


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## bpape

OK. - so we've reduced the peak in the low 40's about 2db, the peak around 85 by about 6db, addressed the problem at 144Hz. But, the 130ish is still a problem. See my post above.

The broad dip still concerns me also. That's not a modal problem at all nor an SBIR issue. Something else is amiss...

Bryan


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## trifidmaster

I have an intersting observation. I have placed 2-2 panels on the side wall, NEXT to the speakers. One panel is on top of the other. I have got a very interesting result.


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## trifidmaster

Next step:
2-2 panels are placed at the back corners
+ 1-1 at the front wall-wall corners stradling. The bottom of the front panels is at 1 m height.


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## trifidmaster

I have changed the computer screen position, it has no visible effect.

The walls are plastered brick walls.
The ceiling is plastered concrete.
The floor is floating laminate floor on a damping 3-4 mm foam, on concrete.
What can resonate? The floor?


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## trifidmaster

I have placed 1-1 10 cm thick panels paralel to the ceiling in the 2 front top corners.


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## trifidmaster

I have increased the thicknes of the 2 paralel panels to 20 cm;

Violet color is the non-treated room, i.e. no panels are placed.


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## bpape

Nicely done. Response is looking better. Decay times are looking much better. Good that you can reuse what you had in the old room.

The big dip is less intense but is still there. It's pretty broad. Your response is +/-4 from 40 to 85 and then again above about 130. 

What do you have left in terms of treatment and where have you not yet treated? Next step might be the wall/ceiling junction to your sides.

Bryan


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## trifidmaster

I am also very pleased with this nice progress.
At this moment only the 2 front corners are treated as shown (photo) in my previous post.

At this moment 10 panels are placed.
I have no more 1m x 0.5 m panels.

I have:
1: Approximately 3 m long 1 m high 5 cm thick "big" panel (rock-wool).
2: +-13 m long 30 cm x 30 cm SOFFIT (rock-wool).
Shall we call them into the game?


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## bpape

The next step would be to play a tone in the middle of the dip and walk around the room and see where you notice it getting louder and softer.

Bryan


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## trifidmaster

Around 100 Hz?


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## bpape

Yes. That's where the dip is.


Bryan


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## trifidmaster

Funny. +- 80 cm from the back wall (standing centered), it "disappears.
It seams that it gets louder at the center of the Left wall,
But it disappears at the center of the Right wall
at the seating position (38 %) from the front wall it disappears at 80 cm from the floor


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## bpape

OK. So, it IS partially height related regardless of what you tried before with the mic - but before treatments. 

Also, if 38% isn't working, then try moving forward a bit. Real answers usually end up between 33 and 38%. Try the seating first and see how it impacts the others now that you have treatments up. 

Bryan


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## trifidmaster

Here it is: 
blue curve = seating position at 120 cm from the front wall
red curve = seating position at 155 cm from the front wall


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## trifidmaster

I have changed the panel's configuration.
Here it is how they are organized. This is the front LEFT corner.









I have moved the seating between 33% and 38%, and the best position is at 33%

See below the corresponding response and the waterfall:


















Bryan, what do you think?

What should be the next step?


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## trifidmaster

This room is for mixing/composing.

I have some fine records, I am listening to them.

Here are my observations.
The bass is not anymore everywhere as it was, now it is defined.
Not too much bass, this is very good - according to me.
One should never forget that these Dynaudio BM5A Compact monitors are not very big.
They will not produce a very deep bass. (The sub is needed for that, but I am not going for the sub).

Anyhow, now I can hear the Dynaudio's typical sound, what I like, 
and I see/hear the magnifying effect of these speakers - what is so good. They show if something is wrong in the mix.

In some records the bass is not yet even. Some bass tones are a bit "boomy", this disturbs me.
Maybe it is the 80Hz peak? Or the dip between 80Hz and 130 Hz?
But in some records the bass is rather OK. 

The sound stage is a bit wide, like it would fall apart - it seems.
I need a bit too much volume to have a solid sound stage - but again, only time will tell if this is OK. 

Mono seems to be OK.

Classical music - ahh, nice! Again not too much bass, but the concert hall is in front of me. I have a feeling like I am sitting little bit higher, on the balcony.
But maybe this is because I often sit there in the concert halls. Again, the sound stage seems to be a bit wide - for me.

I am listening to Gustav Mahler: Symphonie No2. c-moll Chicago orchestra and Chorus
FLute is OK, Flute with harp and string section in a dreamy passages very nice, oboe is OK, harp is clear, violins/violas sitting nice on the sound stage, maybe too deep for me.
Bass is weak, but see above my idea about it. 

Horns are impressive - maybe too loud, as are the trumpets - can be record/concert hall related.

Andante moderato - I like to have more strings.

Intermezzo note: it is so important to go often to a GOOD concert hall - to learn and enjoy the PERFECT sound.

Today I will do a mix of my own music, and see what it gives.

Stefan.


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## bpape

That's probably the best thing to do Stefan. Listen to something you did in your old room that you know very well to see where the differences are.

I think you're getting there and now have a better feel for what in the room is causing what. There is still more to do but this is a definite improvement.

Bryan


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## trifidmaster

Well, I have checked my own work, and I am rather satisfied.
In general it just turns out that some CDs are well done, some are not - unfortunately many are not, but that is another story.

So, Bryan, what do you propose for a further improvement?
I think without extra panels, we can not do more, or???
As the panels are now - visually not ideal - but the sound is acceptable.
Should we start with some soffit work?

BTW: Now after a pause, listening to some records I am even happy with the amount of the bass...


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