Small Basement Control / Mix Room

[Neil H]

Hi Everyone !

This is my first post here - Oh no ! I can hear the groans of the regulars from here Ha Ha
I'll try and adhere to the rules, I've read through the "read before you post guidelines" so hopefully I've got it covered.

I'm in the process of setting up a Mix Room / Control Room for our live room next door and need to address the acoustics.
The room is small which I'm sure is going to be my biggest problem (320cm Length x 300cm Wide x 220cm High)

Ive done a measurement in its current state using Room EQ Wizard and here is the result (i've also attached the file if anyone wants to open it up themselves in REW on their own computer.

full sweep.jpg

graph with smoothing.jpg

Also I have a panoramic photo people might be interested to see https://app.box.com/s/jz803pjdlbnz5pc7tk3h
Ive had to host it and the REW file https://app.box.com/s/ods2a07zco13zseatyzb elsewhere because of their size.

Here's some photos that will hopefully help you visualise the room, sorry about the mess it is a work in progress after all !
Main View

main.jpg

FishEye View of whole Room

Fisheye.jpg

Front Ceiling corner

front ceiling.jpg

Back Ceiling corner

back corner.jpg

Back Ceiling corner 2

back corner 2.jpg

Left Wall

Left Wall.jpg

Right Wall

Right Wall.jpg

From what ive heard you can never have enough bass trapping. so, what i thought to do was make full length bass traps out of mineral wool the full length of the compartment space along the right wall above the cupboard, Duplicate that with a full length triangle trap along the front ceiling above the console and then make full length corner traps floor to ceiling in each corner.
And then panel bass traps along the left wall where the alcove meets the ceiling. (the alcove will be filled with my equipment rack bays)
One rear corner cannot be treated because it incorporates the entrance corridor.

Room noise leaking out is not really a problem as I'm only here out of normal working hours, its a basement and there's nobody around in the evenings nearby.

Is that a good start? and does anyone have any more experienced thoughts ?
I looking at my sweep plot I also need to treat some key frequencies, any suggestions on the best method to go about that?
Budget is low so I'd like to DIY this as much as possible with DIY materials, I'm certainly geared up and skilled enough for making stuff so that's not an issue.
I also don't really want to do any heavy building work like chopping walls as the building is only rented.

Thanks in advance to anyone who feels like chipping in with some pointers !

All the best !

[Soundman2020]

Hi Neil, and Welcome!

Oh no ! I can hear the groans of the regulars from here Ha Ha

No problem! Everyone here on the forum started out as a newbie at some point! No shame in that. (You should see some of my early posts, .... )

I've read through the "read before you post guidelines" so hopefully I've got it covered.

Cool! So you qualify for special treatment!!!

The room is small which I'm sure is going to be my biggest problem (320cm Length x 300cm Wide x 220cm High)

It's not fantastic, but I've seen worse. The ratio is reasonable, so it can probably be made to work.

Ive done a measurement in its current state using Room EQ Wizard and here is the result (i've also attached the file if anyone wants to open it up themselves in REW on their own computer.

The full-spectrum graph isn't a lot of use, but the MDAT file has all the secrets!

OK, it looks like you didn't calibrate REW using a sound level meter, so that should be your first order of business: You need to tell REW how loud the actual level is inside the room, because there's no way it could know that unless you do. You also need to do the calibration procedure for your sound card, and load the calibration file for your measurement mic, if you have it.

Next, you didn't say which speaker you used to do that test, so I'm guessing that the answer is "both" Which again, isn't much use. You need to run one test with each of your speakers individually, then a third test for both of them.

So please fix all the above, then post the new REW file.

But first! .....

Here's some photos that will hopefully help you visualise the room,

There are several issues with the way the room is set up, that will all need fixing if you want to have great acoustics.

First is symmetry: from the point where your head is located while seated at the console, up to the front wall (where the speakers are) must be absolutely symmetrical, left to right. In other words, the left half of the room must be a mirror image of the right side. If you don't get that, then you'll never be able to do a stereo mix that translates accurately to other places. So you need to get rid of all the rack gear on the left wall, and put it some place that doesn't affect the acoustic symmetry of the front half of the room. Eg, put it in road cases that fit under your desk, or to the left and right of your desk, laid out symmetrically. There also seems to be some type of cupboard on the right wall, with a huge cavity in the front corner: get rid of that too, and just leave blank wall there: That cupboard is undoubtedly acting as some type of resonant cavity that is mangling both the symmetry and the acoustic response of the room. It has to go.

Then you need to fix the speaker setup. Right now you have them on flimsy stands, next to the desk, and titled down steeply, and practically in the corners! Then you have another set of speakers ON the desk, laying on their sides, not tilted, and too close together (as well as too close to you). All of that has to be fixed. The correct location for speakers is with the acoustic axis positioned 1.2m (47-1/4") above the floor, about 28% of the room width away from the side walls, right up against the front wall (with a thick acoustic absorber in between) , not tilted down, toed in at an angle of about 30°, sitting upright on massively heavy rigid stands, located behind the desk. The speakers should never be on the desk, never laying down, and never tilted down (unless they are properly soffited in a correctly designed soffit, and even then only a couple of degrees). So all of that needs to be fixed too. You'll have to move your desk back a bit to do that, and you'll also need to lower that huge video monitor down (once again, move the rack gear to better locations and get rid of the wooden box) as well as pushing it right up to the wall, or maybe replacing it with 2 smaller monitors. Hopefully after doing all that, your chair will be at the point where your ears are bout 35% to 40% of the room depth (measured from the front wall). With the speakers set up in that location, try tweaking their positions and angles just a bit, to see if you can improve on the sound, but that should give you a pretty good setup. If it is all done correctly, then the imaginary acoustic axis of the two speakers should meet several inches behind your head, at an angle of roughly 60°.

With that done, THEN do the second REW test, and post the results here so we can get a good idea of how the room is actually reacting, and what treatment it will need.

- Stuart -

[Neil H]

Ok thanks very much for your help, now i have a starting point

I'll be sure to calibrate REW properly for my next set of measurements and do the 3 speaker tests you mention.

With regards to the Symmetry, the closest thing i can get to total symmetry is to rotate everything by 90 degrees to the left and have the alcove/stepped area in front of the mix position.
The cupboard has to stay I'm afraid as its built in/attached to the wall and houses the electricity meter so if i rotated the setup by 90 degrees this would be behind me.
I could replace the doors with "acoustically transparent" mesh doors or somehow turn them into some kind of diffusor ? but that's all i can do.
The rack gear isn't anywhere near all of the stuff I have to fit in yet, there's lots more that will take up a great deal of that space, I already have racks under the desk, there isn't anywhere else to put things and i also have a 5 tier keyboard stand to put in too.
I understand your comments are all based on getting the absolute best out of the space I have which I really appreciate but I'm going to have to do the best I can with these restrictions in place too albeit it as a disadvantage to the ideal's you have detailed.
The speakers (Transmission line design PMC TB1's http://bit.ly/1rfXtk1 are on quite heavyweight stands (These http://bit.ly/1uLgU51 ) and are angled down with these pads http://bit.ly/1BQunuQ because i thought the tweeters should be point at my ears as much as possible.
Should these transmission line design be hard up against a wall ? I read that they perform best about a metre away from a wall.

I realise this info should have been contained in my original post but its only once the questions are posed or provoked by conversation that it has become clear.

I also realise I'm in some way asking for help and then arguing with the response but there is not an awful lot i can about the way the room is.

Thank you very much for you input so far I and very grateful and still welcome any other response or input yourself or anyone else can offer !

[Neil H]

The more I think about it the more it seems to make sense to rotate my setup by 90 degrees and have the cupboard behind me and make the cupboard doors into a bass trap, superchunk either side of the cupboard and the two front walls plus tri trap the entire ceiling to walls sections around all four walls of the room
Then at least I will be bass trapped to the max and have the best symmetry.

my only concern is the speakers being under the alcove cutout of the front wall, will this create problems and should this design of speaker still be right against that wall ?

Thanks !

[Neil H]

Ok I've moved the room round 90 degrees counter clockwise and done some new measurements with and without the cupboard doors open.

Heres a link to the mdat file :
https://app.box.com/s/0enk805fzftt5uajq7p4

[Neil H]

No thoughts on these measurements?

[Soundman2020]

There seems to be something wrong with the way you are taking those measurements. Firstly, they are at a very low level, below 60 dB, so there's way too much noise in there to make them usable. Try doing them at about 80 dB for each individual speaker. Did you calibrate REW using a hand-held sound level meter? If not, then do that as well.

Also, in addition to the "L" and "R" measurements, you should also do one with both speakers on.


- Stuart -

[Neil H]

Hi Stuart,

Thanks for your reply,

I calibrated REW using its internal generator and SPL meter as I don't have a handheld external meter.

I'll try and take a look at doing them again.

[Soundman2020]

If you don't have an external hand-held meter then you can't calibrate it! REW has no way of knowing what the REAL sound level is in the room, unless you measure the level with a calibrated meter and then tell REW what the level is.

- Stuart -

[Neil H]

Ok i'll borrow a meter and do it again.

Thanks

[Neil H]

ok here's my measurements when calibrated at 75db with a meter (REW said to do it at 75db).

https://app.box.com/s/kniz2y5zj5m4kbndu39g

[Soundman2020]

There's still something wrong. The levels are still too low! You said you did them at 75 dB, but the graphs are showing that you did them at 58 dB. See below:

neil-h-wrong-level-2.jpg

Are you SURE you calibrated REW correctly with your sound level meter? Are you SURE you had the meter set for "C" weighting and "Slow" response?

Also, if you measure correctly with the levels of each speaker individually at 80, then the combined level with both speakers must automatically be 6 dB higher. In your graphs, the level for both speakers is the SAME as the level for the individual speakers, which is impossible. It seems that you adjusted the level of both speakers before taking that reading?

I'm not quite sure why your readings are not working out, but there's something wrong still...


- Stuart -