acoustic treatment an a little rectangular room [newbye question]

keng

Member
2010-09-16 11:38 am
First of all, Hi all forum members,

I need help to solve a problem with my dedicated mixing / control room.

I have a room that has:

5,12 meters width

2,92 meters lenght

3,14 meters hight

the celing is build with wood, every 96cm there is a wood beam (20wX25h) parallel to the 5,12 meter wall that hold up 20 cm wood slats.

My problem is that I can place the speakers (dynaudio bm12a) on the shorten (2,92 meters) wall 'cause there is a big hot-water-heater (radiator) that sits on the wall. on the opposite wall there is a 140 cm windows with heavy drapery, but I can't place on this wall the speakers because there is a strange angled architecture (I've attached an image that represent the room plant to show you the problem).

[IMGDEAD]http://www.kengprod.com/room_plant.jpg[/IMGDEAD]

Due to my limited budget and the fact that this is also my house, where I live, eat and sleep, I've bought some 9mm cork panels (50X50) that I would like to mount on front, back and side walls, as far from the wall as 9mm are as I should increase the Freq absorbed by them. I'll build some skyline diffuser to place on walls, and two tube traps to place in the angles, near the celing. I'll also hope to build two perfored helmholz resonator absorber as I can get rid of any of the rooms modes.

I've also bought one roll of 4mm cork for placing on the wood door, and somewere in the room...

...well, as one of the modes is 58,99 Hz, placing speakers 73cm far from the back wall I can gain some advantage from the frq cancellation if I'm not wrong.

...for now, without placing any absorber panel, I notice a ring/flager echo effect on the HF, and I was thinking to get rid of it by partially kill front and back walls, but as I've read on internet there could be problems on M-LF by placing HF absorber panels on the back wall...

I'm also reading Acoustic Absorbers and Diffusers - Theory, design and application, and Master Handbook Of Acoustics, but I'm a newbye in this field and I only want to gain some good results from my room, I don't want to build a super-high-quality studio, as my budget is limited...

can anyone give me some advice about "another speaker placement", some specifics cork panel placements for incrementing absorbing Freq, some other useful advice to take the best from my room without the need to sell one of my kidney? Tnks really so much in advance,

cheers from italy,

keng~ :)
 
Let's address the bad first.

Unfortunately that layout is pretty bad for acoustics. When ever possible you want to place the listening setup length wise rather than width.

I'm not sure if the red point in the center is a listening position, but if the couch is where you plan to listen from I would add being right against the wall is not ideal.

Tube traps don't offer any advantages over normal corner traps.

Cork is pretty ineffective.

A perforated Helmholtz resonator won't dent most nodes.

To kill a little of the flutter with out over deadening the space you can place diffusers behind the listening position. The problem is you want to sit about 4x the length of the target low away from the diffuser. I would highly suggest changing the orientation of the listening setup. If you do this rear diffusers actually become piratical. I wouldn't worry about over dampening with the materials you described tho, you won't be able to have any real impact on the LF problems in the room using that method. The tube traps will help, but on the whole you need a lot more treatment to correct your space. Some absorption panels and the first reflection points, on the walls behind the main speakers, a MPD or dampening panel at the first reflection point on the ceiling. You have the right idea but you're going about it in all the wrong ways, lol.

Just for a little background, I design sound rooms. This includes the construction, sound proofing, structural dampening, the acoustic treatments and digital calibration. I only work with home environments, I don't work at all with acoustical architecture, concert halls, auditoriums and the like.
 
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keng

Member
2010-09-16 11:38 am
sorry for the double an triple post, but CTRL + C seem to take posting action and not "copy" action, xcuse admins.

First of all, tnks a lot for reply kareface...

well.. unfortunately I've no other solution for the listening position, as in my first post I wrote on the right of the mixing desk there is a hot-water-heat (radiator) and I can't prevent its bad-alluminium reflection placing mixing desk and monitors there,

on the other side, on the left, there is a bad wall config, as showed in the image. there is an angled config that can create really big problems, and on the wall there is a big windows even if tapped with an heavy drapery.

A friend of mine, that is a phonic advice me to buy cork panels for absorbing reflections, after bought that, now I see that the fiberglass is more efficient, the efficience index of the cork is 0.56 the ones of 703 fiberglass is 0.86 :eek:, but now I've bought this panels (f...ing friends!!!:mad:), and I would to not lose this money and use them for the freq. range from 1000 Hz to 6000 Hz as I know that in this range the index is not so bad.

Do you think that I can solve the problem by placing speakers on the left shorter wall withoud summing the angled wall problem to the others?

Now I'm building the skyline diffuser. if I change the listening position placing it long the shorter wall on the left of the actual mixing deck position, where you think is right to place the sofa?

How can I solve the angled wall problem? mind that the window is for an half far from the angled wall and for another half hided by it, as shown in the image.

tnks a lot for the time!
 
Wasp focuses on imaging and works in the frequencies that are more directive, but below 500hz the room interaction will be very influential. For the speakers you have I say it would be reasonably effective.

I'm not sure what you mean by the angled wall problem. The illustration doesn't indicate anything angled unless I'm missing something.

If you can position the couch away from the wall it will improve perceived reproduction. If you place diffusers behind you make sure they are designed with a higher frequency as the target low. Just figure out what wave length would correspond to 1/4 the distance from the wall and use that as the target low for the diffuser. Other than that, I would highly suggest fiberglass, you can find large batts of R-30 insulation for $15-$20 that'll work well with some cheap fabric over top. It isn't as effective as rigid fiberglass for most frequencies, but you can't really beat the price. You can just bundle them in a cheap fabric, just make sure it's thin enough you can easily breathe through the material. If you have any tools to take some measurements with, if you post some waterfall data I can give you an idea how many treatments you'll need.
 

keng

Member
2010-09-16 11:38 am
hi, I think i could affort some rock wool of 2" and 50Kg of density, the OC 703 rigid fiber glass is similar to this, I think I can get it for a cheaper price, I don't know if is cheapest to order around the world as I can buy it near my house. For the fabric, well, when I have rock wool panels I try to search on internet for some cheap...

I undestand the problem of the back wall, I'll try to figure out how I can set-up a different placement... At the moment I don't know I have to move all my fornitures and see if seet right in a new configuration, is also my house and I would to mix all the needs of a home studio and my only living, and for a hall configuration this seem to be great, but I will try tomorrow...

the problem of "the angled wall" (excuse my eng...) is the fact that on the shorter wall on the left of the picture, there is a wall configuration that builds a rectangular section of 61cmX47cm and I think that could create problems on the LF, I can't place traps there, because there is the window opening and I need it, if I place the desk and speakers there, well I can't freely manage the LF absorbtion.

unfortunately for now my only misurement are my hears, I have a zoom h4 recorder, some audiocards, some mics but I think are not good for purposes like misurement, I read about SPL meters, but the cheapest on the market is about 59$ without transport fees, I hadn't found yet an italia shop where I can buy one, I don't now people that have it...

for now, I would eliminate this nasty ringing echo, that I clearly hear, by eliminating it I'll get a good starting poin for fine tuning LF, because the overall room sound is not so bad, the wood and height of the ceiling do a good job, as I can hear... :)
 

keng

Member
2010-09-16 11:38 am
hi, I think i could affort some rock wool of 2" and 50Kg of density, the OC 703 rigid fiber glass is similar to this, I think I can get it for a cheaper price, I don't know if is cheapest to order around the world as I can buy it near my house. For the fabric, well, when I have rock wool panels I try to search on internet for some cheap...

I undestand the problem of the back wall, I'll try to figure out how I can set-up a different placement... At the moment I don't know I have to move all my fornitures and see if seet right in a new configuration, is also my house and I would to mix all the needs of a home studio and my only living, and for a hall configuration this seem to be great, but I will try tomorrow...

the problem of "the angled wall" (excuse my eng...) is the fact that on the shorter wall on the left of the picture, there is a wall configuration that builds a rectangular section of 61cmX47cm and I think that could create problems on the LF, I can't place traps there, because there is the window opening and I need it, if I place the desk and speakers there, well I can't freely manage the LF absorbtion.

unfortunately for now my only misurement are my hears, I have a zoom h4 recorder, some audiocards, some mics but I think are not good for purposes like misurement, I read about SPL meters, but the cheapest on the market is about 59$ without transport fees, I hadn't found yet an italia shop where I can buy one, I don't now people that have it...

for now, I would eliminate this nasty ringing echo, that I clearly hear, by eliminating it I'll get a good starting poin for fine tuning LF, because the overall room sound is not so bad, the wood and height of the ceiling do a good job, as I can hear... :)
 

keng

Member
2010-09-16 11:38 am
Ps. about the diffuser, if the distance from the front of the speaker to the wall behind the listener is of 219 CM and I want to place a diffuser (Skyline???) on the behind wall, what is the right freq for design diffuser, starting with a freq of 500 Hz is good enoght, or I've to build a diffusser starting with a lower freq? tnks a lot in advance. :)
 
You shouldn't use diffusers on the wall behind your main speakers. That position is ideal for absorption.

the problem of "the angled wall" (excuse my eng...) is the fact that on the shorter wall on the left of the picture, there is a wall configuration that builds a rectangular section of 61cmX47cm and I think that could create problems on the LF, I can't place traps there, because there is the window opening and I need it, if I place the desk and speakers there, well I can't freely manage the LF absorbtion.
You should test it out just to make sure. I've found spaces like that can sometime be very reverberant in the space, but not dramatically impact the listening position.

for now, I would eliminate this nasty ringing echo, that I clearly hear, by eliminating it I'll get a good starting poin for fine tuning LF, because the overall room sound is not so bad, the wood and height of the ceiling do a good job, as I can hear...
Is it on high pitched sounds? Or when you clap? If you have no treatment it's likely a flutter echo. Absorption or diffusion will help correct that. Don't worry about treating the higher pitched reflections, they'll get taken care of long before the bass is.
 

keng

Member
2010-09-16 11:38 am
It is more audible on the high pitched sounds, but is also present when I clap.

I placed the monitors long the shorter wall, and the space is really reverberant, the wall is build with plaster blocks of 7 cm, and it is really reflective, from my point of view, the overall sound in the new listening position is less clear than in the previous position. Today I'll go to buy roockwool panels and starting placing it as they are, for the new listening position, and I'll hear.

I'll buy also a behringer ECM8000, so I can post some etf waterfall. tnks for the tips, I'll update when I've news. :)
 

keng

Member
2010-09-16 11:38 am
Hi all, ok I'm building rockwool panels, the rockwool chosen is 2" tick dimensions 2'X2' of 50kg/m3 density, but I think I've choosen the wrong fabric for wrapping them. I've used a wood frame, and I would like to know if anyone can suggest me what type of fabric I've to buy for wrapping panels, here are some photos of the building process,

I've made a wood frame of 4" depth for leaving an air gap between rockwool and wall...

The fabric choosen do not let all the air pass throught it and so I've to buy some other fabric,

anyone can advice me about the right fabric to choose, many tnks in advace:

ImageShack Album - 14 images
 

keng

Member
2010-09-16 11:38 am
yes, I've a store near me, tomorrow I go and buy it, tnks really so much. do you think is good the rest of the job kareface?
have I build the right frame? rockwool panels are 2" tick I've made a frame of 4" tick, is it the right dimension?

next step will be the builds of a skyline diffuser, but first I've to take some misurements... :)
 

keng

Member
2010-09-16 11:38 am
Hi all guys,

I finally finished to build all the panels for my room, I've bought R plu D (new version of ETF) and took an ECM8000 mic for mesurements from a friend of mine. I've read a few pages of the r+d manual and started taking some mesurements. Well I'm not familiar with mesurement process but it seem to be not so hard...

a) the placement suggested by calculation SW (500 Internal Server Error) and kareface seem to be not So desirable, I've large and deep calcellations from about 100 to 500 Hz, much more than if I place speakers along the wider wall, but I hope to post some waterfall later in the evening, to show U this phenomena

b) My only-but-big problem is that I don't know how to take mesurements for frequencies below 100 Hz, I've calibrate my audio card (NI guitar rig mobile I/O - 24 bit and up to 192khz) as the manual procedure suggests...

the waterfall for a gate time of 10MS shows up frequencies from above 100 Hz up to 22 khz, but not below 100...

Is there an option to tick or modify to take mesurements for these frequencies, Have I to rise up the gate time or so on?

really many tnks in advance,

cheers from italy,

keng~