John Sayers' Recording Studio Design Forum Archive

Hi Again,

We then placed the rockwool inside the frames, and screwed in some hooks so that we could thread some string to hold the rockwool in place :-
We also covered these in cotton fabric :-
The next thing to do was plug the window. Due to weight issues, we used some very thin MDF board :-
Unfortunately, when we attached one of the absorbers to the wood it was far to heavy for the wall. We needed a plan B. Much to my dismay, we had to use our lovely famous acoustic foam for this and for the slant also. We could not even use a large screw/nail for the slant as there seemed to be some sort of metal plate behind the slant (made of BA13). We managed to put one of the absorbers up (in the middle).

the next thing to do was to add some hooks to the ceiling for the clouds :-
We then hung 2 clouds above the mix area.

We finished by hanging the four main panels on the side walls along with 2 bass traps under the slanted wall and four on the back wall. As we had 2 of the shorter absorbers left over, we put one on the longer side wall and one will be a free standing panel leant against the door. We then put up the plug and the other foam panel, as well as covering the shelves at the back of the room with a curtain :-

Front View
Right Hand Wall (Facing Forward)
Left hand wall and window
Back wall (Left) and Door)
Back Wall (Right) with shelves
Now the moment of truth. I set up the equipment and listened back to some music. The first thing that stood out was the clarity of the sound. The stereo field seemed so wide, and there seemed to be a phantom centre speaker (the vocals seemed very prominent in the middle). It seemed though, that this phantom centre speaker was very loud and dominant on one of my old mixes. I played a commercial CD and it seemed better.

I loaded up an old track i worked on and was astounded at how badly some of it was recorded. I could hear all sorts of pops, cracks and differences in volume. I reloaded the stems of the track and had a play with it. With the stereo field seems so wide it felt like mixing in wide screen, and when adding plug ins i could really hear what they were doing (i tested with delay, reverb and compression), but the stereo field seemed unnaturally wide at the same time. Is this normal?

One thing that was still very apparent was the bass. When i moved my head forward over the desk it became very loud and muddy, and when i moved back on the chair a little (a very little) it seemed to disappear completely.

The flutter echo had completely gone. The only place which seemed to sound weird was in the corner by the door, where the kick drum seemed very boomy on the commercial cd.

Another thing to note though is that my ears really have that aeroplane feeling (like they are being squashed with no high end in the sound or air), like the room being closed and the walls coming in. Maybe this is because the room is acoustically dead and everything sounds dry?

I then set up REW again and ran the same tests as before. The results seemed to show big peaks still :-

Left Speaker
Right Speaker
I know that in a room that size with the horrible walls i have (there seems to be metal plates behind most of the walls) that i will never get the sound perfect, but i was wondering what else i could do to tweak the room and try to get it more balanced (although there is a marked improvement). I s it normal for the bass to change so dramatically with just a head movement, and is the sound from the middle meant to be dominant (although it wasn't that bad on the commercial CD, but still sounded a little weird).

Any further advice would be great, but in the meantime Stuart thanks very very much for your input so far, it has been very helpful.

TCT.

Glad to hear that you got a really good improvement from the advise you got here!

Looking at those REW graphs, I suspect that you maybe didn't roll off the bass on your speakers. When you put speakers up against a wall, you get a natural bass "boost" of 6 dB, since the entire wall acts somewhat like an infinite baffle for low frequencies. Most good quality studio speakers have controls on the back precisely for this purpose, so you can roll-off the bass response. So check on the back of your speakers, and set that control to -6dB, or if your speakers don't have that, then use an external cross-over or phase-linear equalizer to roll off the low end, starting at around 500 Hz (based on the REW graphs).

On the bass null at the mix position: I suspect that is simply due to the room geometry, and the position or your head in the room. Can you measure how far back your mix position is? In other words, measure the distance from the front wall to where your ears are, and also from the rear wall to where your ears are (measure those at ear height: that's important, since your front wall has a steep angle on it.) I suspect that your ears are probably very close to the 50% position, which is the worst place for them. If so, one option might be a smaller desk, so you can get your head a bit further forwards. That might not be practical, due to the angled front wall/ceiling. It would also mean toeing the speakers in a bit more, to a higher angle, which would broaden your sound stage and stereo image somewhat: (that's not a bad thing, but is something that you need to be aware of.)

The modal response of that room looks surprising good, considering the size! Almost nothing stands out badly. Your issues seem to be much more due to things like reflections and comb filtering. It would be good if you could do another set of graphs, but zooming in on the region below about 500 Hz., since that's where your modal problems will be.

One thing that might help a bit, is to put some really deep absorption on the rear wall. Maybe a full panel of 4" 703, spaced a few inches away from that wall, and across the entire width. You could even tilt it down a bit, so it is further away from the wall at the top than at the bottom.

One thing that is hard to explain, is that dip at around 1kHz on both speakers. I'm wondering if that might have something to do with the window "plug" acting as a panel trap of some kind, or perhaps even the walls themselves. Do you have any information on how the walls are built? (Materials, thickness, air gaps, fill, etc.). However, that same dip is very evident in the original readings you took, before you did anything to the room, so I'm suspecting the walls...

The issue with the "dead" sound might well be due to having too MUCH absorption in the room, affecting high end! Dead rooms do indeed sound unpleasant and claustrophobic. Of course, you do need lots of absorption in there (in fact, even more than you have already) to deal with the lows, so the trick is to "tune" your treatment a bit, such that it affects the lows more than the highs.

What you can do there to see if that is the issue, is to cover your acoustic panels and bass traps with plastic. The concept is that the plastic acts to reflect the highs back into the room, while still allowing the lows through to be treated by the absorption. To test, just wrap a piece of thick plastic sheeting around them as the are right now, and see if that improves the issue. If so, then you can take off the cloth and attach the plastic properly to the frames, then put the cloth back on. It needs to be fairly thick plastic (not garbage-bag style!), or maybe even try with very thin wood. If that works for you, then you can experiment with different amounts of coverage (you might only need to cover half of each panel, or 2/3, or all of some and not others, or whatever works), and with different materials, to see what gives you the best result.

The final "tweaking" of the room can take a while, but you should be able to get some improvement.

By the way, please try to keep all your posts together in one thread, so it is easier to follow what you are doing, instead of having several threads going at once!

- Stuart -

Hi again Stuart (and to all).

I have finally got a break in my work and will set about tweaking my room.

To summarise so far. I have had massive problems mixing in the room. They are these :-

1. Every mix i have done has come out far too bright, and although they sound fine in the studio, on headphones or elsewhere they almost rip my ears out. They also have little or no low mids, and the ones that do this area sounds very muddy.

2. I get ear fatigue very quickly when working in there. This i think is due to the (on aeroplane) feeling i get when i am working in there, where my ears feel like they are being squashed and i lose sensitivity to certain frequencies. I am working at quite a low level and i rarely turn the monitors up very loud.

3. It seems to be hard to work out loudness of tracks when monitoring. Something that sounds balanced in the room will sound out of balance else where, especially with drums. It's as though when i turn something up i am not hearing the volume change correctly. I also have trouble to hear how compressors are working when i add them to a sound/track due to the same issue.

4. There also seems to be a lot of phasing at certain frequencies. If i do a frequency sweep using a sine wave, at times it is as though it is bouncing from side to side.

From reading your previous post and from what others have told me, this is my first plan of action :-

1. I have one panel left over from the original build as i had to use foam on the slant due to weight restrictions. I will put that on the rear wall behind the shelves.

2. I will replace the desk with a small table. Unfortunately due to the size of my display monitors, i cannot move the speaker monitors closer together otherwise they will end up behind the display monitors (And i do really need 2 due to my video work). One option i will try is to use some higher speaker stands and put the speaker monitors on their sides, if this is a viable option.

3. I have some very thin wood left over from the panels i made for my foam. I will try placing them over some of the absorbers. For this though i don't know where i should start, as i am worried about introducing flutter echo into the room. Can you advise me the best place to start? Should they be on the side walls? Should they be in places where they are not directly in line with the speaker monitors?

4. As for eq'ing the speaker monitors, hopefully in not to long i will be able to afford a nicer pair. As mine have no crossover switch and i don't own a hardware eq, is it possible to put an instance of the Waves LinEq plug in on my DAW's main output?.

Once i have done all of this, i will retest my room and send you over the zoomed below 500Hz graph from REW, and maybe we can work out the best way forward for this if all is ok.

If there is anything else that you feel you can add to this i would, as always, be eternally grateful and if there is any more specific information that you would require, please don't hesitate to ask.

Kind Regards,

TCT

Hi Stuart

OK

I have installed a smaller table, placed an absorber on the rear wall behind the shelves, Measured the seating position at 38% of the way across the room (from the headhight position of the slant to the shelves), made an equilateral triangle between each monitor and ear position, made sure the desk is exactly halfway across the width of the room and the monitor speakers are the same distance from each wall. I have also swapped my Alesis M1 Active MKII's temporarily for my Alesis M1 Active 520's (As they have a proximity switch on the back to set the distance between the walls, this is set to 2 (close to walls)). I have also put a couple of pieces of foam on the table to help with the reflections from the desk.

Here are my results :-

Full left speaker waterfall (40 Hz - 20 KHz)
Full Right Speaker Waterfall (40 Hz - 20 KHz)
Left Speaker 60 Hz - 600 Hz
Right Speaker 60 Hz - 600 Hz
Left Speaker 500 Hz - 900 Hz
Right Speaker 500 - 900 Hz
Left Speaker 900 Hz - 10 KHz
Right Speaker 900 Hz - 10 KHz
Left Speaker Reverb Time
Right Speaker Reverb Time
Room Front View
I can see there are major problems around 80 - 100 Hz (almost a 30 db Dip), 300 - 400 Hz, and smaller around 600 and 800 Hz. The reverb time graphs i am afraid i do not really understand so apoplogies there.

I have been advised to build some home made diffusers for the side and back walls. Would installing these mean that i could introduce some hard surfaces and due to the nature of the surfaces of them being uneven that i would not get any flutter echo if i placed them opposite each other?

If there is anything else you think i could do to sort these out, that would, as always, be most welcome.

Thanks in advance.

TCT.