# Speaker placement and DIY room treatment



## Fasttracker (Mar 7, 2012)

Hey ,
It's not really a home theater setup but acoustics are acoustics right 
So i'm trying to get the best placement for my speakers and my seating and i'm going to add some acoustic treatment.
After doing some reading i think the room type (my attic) , with the angled walls , might be the biggest problem for getting a flat response from my speakers.
I allready made some panels ( Wooden frame with rockwool ) and i'm planning on hanging up at least 10 more.
Especially to the sides of the listening position , above , behind and corners.
I might even build one of those diffusers with the different lengths of foam bars .
My speakers are nearfield monitors (build for close listening) and a subwoofer on the ground behind the desk.
I did some testing by playing a few octaves of sinewaves and i seem to be getting the flattest response when sitting in the couch beneath the window and to the sides of it .

Could you guys help me out with the placement and treatment .

Moving everything around the room is not a problem , i will even move the rockwool panels if necessary . 

I know i'm asking alot but i know very little about this kind of stuff .

Thanks


----------



## Tonto (Jun 30, 2007)

Welcome to the Shack, you'll be able to get plenty of help here cause "thats just what we do."

I noticed you called it a HT but I don't see your display (unless that is a laptop I see--pics are a bit small for these eyes). What I can say to begin with is while treatments are going to help, you may be better served measuring the room (before you place the treatments) from your preferred listening position. That way you will know what frequency's will need working on. Are you using REW?


----------



## Fasttracker (Mar 7, 2012)

Tonto said:


> Welcome to the Shack, you'll be able to get plenty of help here cause "thats just what we do."


  :T

Well i said it's not really a home theater but it's my music studio and yes that is a laptop .
Normally there's a 37 inch display on the wall behind the laptop but at the moment it's temporarily used elsewhere.

I have tried REW before and i chose one of those EQ's and i got a bunch of settings ( like 9 i think ) with the frequency's , bandwidth and the amount of dB to cut i presume.

But since then i totally slimmed down my studio and hung up the rockwool panels .
I used a measuring mic that came with my onkyo amplifier from my home theater and plugged it into my soundcard.

I will do another measurement this evening (belgium time  ) if i can just remember where i found those settings last time.
I think i just chose one of those hardware eq's .

Greetz...


----------



## Owen Bartley (Oct 18, 2006)

Looks like a pretty 'hard' reflective room. Wood floors? A nice thick rug might help to tame some reflections there, maybe a cloud overhead. Probably some thicker panels or corner traps to better-handle the low frequencies. Otherwise, do like Tonto says and measure the room, and that way you can pick the frequencies that need help, and build some treatments specifically to clean those areas up. Looks like a nice room overall, and once you get it dialed in some more it will be great.


----------



## Fasttracker (Mar 7, 2012)

The floors are wooden planks with laminate flooring on top.
The walls are plasterboard on top , then osb with insulation behind them.

Yeah , i figured a thick rug might help but i'm afraid of all the dust coming off it. 

I measured the room with REW , it's in the attachment.
I hope i did everything right.
I generated some eq filters with a target level of 84dB.

Now where do i go from here ?
Is it a trial and error kinda thing or are there general guidelines on where to put the treatment and what to use ?
I really don't want to spend a week building and putting up stuff and then find out i did it totally wrong.

Greetz...


----------



## Owen Bartley (Oct 18, 2006)

I don't know enough about REW yet to be able to help you with that, but I'm sure someone here can. In theory you should be able to design treatments specifically to deal with trouble areas, but again, there are people around with a lot more experience and skill than me who can get you started.


----------



## Fasttracker (Mar 7, 2012)

Ok ,thanks .


----------



## AudiocRaver (Jun 6, 2012)

The slanted attic walls are helping reduce "standing wave" resonances at low-mid frequencies. A free benefit of the shape of your room, might as well appreciate it.

It does look like a pretty reflective room. You'll probably need a combination of wall and floor treatments. A few medium-sized throws on the floor, that way they're washable/replaceable. Your wall treatment frames are the right idea, with broadband absorptive material - not sure what the good stuff costs these days. You will probably need a bunch of them, absent full carpeting.

Here's a strategy: Move away from the end wall and its reflections, use one good-sized throw rug at your main recording/mixing position, a couple more smaller ones elsewhere in the room, turn so the angled wall is in front of you, go for roughly 50% scattered wall coverage with your wall frames concentrated in that 1/3rd of the room, placed so there is symmetry relative to your mix position, leaving the room ends for late reflections. You can build up the amount of absorption until it feels dead enough - RT60 under 0.5 second will sound pretty good. You'll probably need some absorption on the end walls to kill the echoey reflections back & forth between them.

Here is a nice resource page, a little technical, but readable.

These are just some ideas. There are other ways to do it. Best of luck.

AudiocRaver

Edit. Looking at your photos again, it may be smaller than I was envisioning. Can you give us dimensions?


----------



## Fasttracker (Mar 7, 2012)

Hey , thanks .
Looks like a pretty good strategy.
If i understand correctly i have to face the angled wall (without window) , put up enough of those rockwool panels to cover 50% of the walls around the listening postition (( left , right , in front and above ) symmetrical ) and a few extra on the end walls and put a few rugs on the floor, right ?

What did you mean with " leaving the room ends for late reflections " ? 
Do you mean the room ends with the angled wall , or the straight wall ?
Cause first you say leave them and then you say put up some absorption.

The room dimensions are
- from straight wall to straight wall 418cm , 164,6 inch
- on the floor between the angled walls 712cm , 280 inch
- the ceiling between the angled walls 230cm , 90,6 inch
- the heigth 243 cm , 95,7 inch

Looks like i will have my hands full this weekend and the next 

Greetz...


----------



## robbo266317 (Sep 22, 2008)

I don't know how good the REW results are going to be using the Onkyo mic. (It's one thing I have been meaning to do, compare my calibrated mic with the Onkyo's.)

Also it is not recommended to use a laptops internal soundcard with REW.


----------



## AudiocRaver (Jun 6, 2012)

Fasttracker said:


> What did you mean with " leaving the room ends for late reflections " ?
> Do you mean the room ends with the angled wall , or the straight wall ?
> Cause first you say leave them and then you say put up some absorption.


Yes, those were conflicting suggestions. Pardon my rambling, and thanks for the dimensions, that helps.

Forget the "late reflections" comment, the room is not as long as I was imagining. I was remembering an attic room of my own from awhile back. Oops.

I still like the idea of the mix position facing the slanted wall with a throw rug under the flat part of the ceiling. The straight, parallel walls will need a fair amount of attention, especially around the mix position. I think I would go with about half of your wall panels on the parallel walls, primarily around the mix position, and the other half scattered on the other wall surfaces, a bit more concentrated around the mix position. As someone else mentioned, a cloud of some kind under the center ceiling might be needed, but a good throw rug under that part of the ceiling might be enough.

I don't know what kind of speakers you have. If they are rear-ported they will sound especially boomy if too close to the wall. The space at the and of the room in front of the mix position, that low bit of straight wall, might be a good place for some absorptive material, too, if you have something absorptive that you could just store there. A lower priority, unless you have the boomy bass problem from your speakers (worse with rear-ported speakers but potentially a problem with any speakers close to a wall) and then it becomes a higher priority. Start with the throw rug and wall treatments and that may be enough, hopefully.

Getting the reflections under control is your main goal, and the parallel walls are your worst enemy in that room, especially around the mix position. I hope that all makes a bit more sense.

On the other hand, if you really like your room set up the way it is, I would say that the same basic approach for treatment would apply, about half of the wall panels on the parallel walls and the other half on other wall surfaces with the emphasis around the mix position and arranged with symmetry relative to the mix position. And with the throw rug under the flat ceiling. And with the speakers a few feet away from wall.

I agree you should get a calibrated microphone.

Good luck with your acoustics project.


----------



## Fasttracker (Mar 7, 2012)

These are my speakers - http://www.genelec.com/pdf/DS1029a.pdf
This is my subwoofer - http://www.triangle-fr.com/en/esprit/meteor_0.1/

I actually like my setup the way it is now because i like some sunlight in the room and if i change my setup to face the angled wall i would have to put curtains up because the sun reflects on the laptop/tv-screen.
Facing the angled wall with the window isn't a good idea , right ?
I will cover at least 50% of the front wall with those panels and all around the listening position and some on the rear wall too .
Then i'll do another measurement to check the results .

The van broke down this weekend and had to be repaired so i could not go shopping for planks and rockwool , slight delay to next weekend.
But i did buy Two rugs .
Do they have to be thick ?
I bought them rather thin so i can still comfortably move around with my chair.


And robbo266317 :
If you get to compare the mic's could you please share the results ?
I'd like to know cause i don't want to be making unnecessary costs.

Greetz...


----------



## AudiocRaver (Jun 6, 2012)

Your speaker choices look like good ones. I certainly understand your wanting to preserve your room aesthetics, so by all means see what you can do with your current setup. Thick carpet would be better, but being able to move your chair matters, too. Plus you probably wanted to be able to remove the rugs for cleaning. There are always trade-offs.

Looking at the room EQ Wizard file that you attached previously, it looks like there is a resonance at 50 Hz. Are you in the US? Is your AC 50 Hz or 60 Hz? Where was the microphone positioned for that curve? Was this the left or right speaker being tested? Only one should be run at a time when doing a sine sweep measurement.

If it's not too much trouble, could you run us one more set of curves? With the microphone at the center of your head at the mixing position, and only one speaker at a time, one curve with the left speaker alone, one with the right alone, and one with the sub alone. For the rough view we're looking at right now, with 20 DB variations to be corrected, using an uncalibrated mic is probably not a huge deal. When you get into more refined work, especially if you start doing EQ work, then it will be important.

Hope getting your van running is not too expensive. It is frustrating to see money earmarked for a fun project having to go into something less fun like car repairs. Good luck.


----------



## Fasttracker (Mar 7, 2012)

I still have some rubbery matts used to put under laminate flooring to dampen the footsteps.
Maybe putting some under the rugs would help too ?
Then i can still move around with my chair.

The ac over here (belgium) is 50hz.
I attached the mic to the chair roughly at the place where my head normally is.
I didn't know you had to use only one speaker at a time.
I measured my room with everything turned on.
Left , right and sub .
I will redo the measurement , and hopefully the rest of the rockwool panels , this weekend.

And it's not my van so no problems there 

Greetz...


----------



## AudiocRaver (Jun 6, 2012)

That explains the 50 Hz "resonance." It is so sharp that it almost has to be hum getting into your measurement signal from somewhere. It will be good to determine the source at some point, a motor or compressor, perhaps from a source you haven't noticed because of the frequency, although it does appear prominent and loud on the curve, so, assuming it's not some annoyingly loud hum - no insult intended, really, but sometimes people do miss things like that - more probably, it is 50 Hz noise from your AC mains getting coupled into your computer, or into your mic, maybe from a ground loop or poorly grounded piece of equipment somewhere. So many fun possibilities.

Best wishes to the unfortunate van owner, glad it isn't you.

The pad under the rug, it is hard to say exactly what effect it will have, and at what frequencies. A springy material like that can be quite absorptive at some frequencies and not so much at others. Hopefully it won't be too difficult to try with and without to see what difference it makes. I fully realize how easy it is on this end to throw out suggestions that have you spending hours actually trying to implement them, and will sincerely attempt to be respectful of your time. Re-running the frequency response plots is a pretty important starting point. Will be watching for your post, others may have suggestions as well when we get a better measured view of your room. Have a great weekend.

Edit: You did say Belgium before, I had missed that. A microphone thought: if the microphone connection into your measurement interface is different than what the microphone was designed for, it might be that the microphone cable is not grounded properly, or the shield is not connected, or something that would explain all that 50 Hz pickup in the measurement signal. Something to look at.


----------



## Fasttracker (Mar 7, 2012)

My first guess for the 50hz peak would be the ac mains of my laptop like you suggested.
It 's not really a problem to test the pad under the rug so that will be on the to do list for next weekend.

After looking at the graph a bit more i find it very strange that there's such a steep roll-off of high frequency's starting at 10K.
Maybe a measurement mic problem ?
I'm going to search around a bit for prices and shops that sell measuring mics and if it's not too costly i will buy one.
What i also find a little strange is that after adding all those panels i can see little to no difference on the measurement graph.
I do seem to notice more detail in the music .
With my little knowledge about the subject i seem to think that the main problems are the peaks at 50 , 130 and around 1200 Hz plus the roll-off starting at 10K .
Any suggestions on what to do about them?

I added a few more panels and i also added a 2cm space between the panels and the wall.
I placed two panels on the ground behind the woofer , good idea or useless ?
Any suggestions on where to put the 5 panels i've got left?

Here are some pictures of the studio so far and also a picture of how i made the rockwool panels.
There's also a new REW measuring file with only the left speaker in the attachment.
Greetz...


----------



## Fasttracker (Mar 7, 2012)

Thinking about ordering that behringer ecm8000 mic to go with my " Motu ultralite mk3" Soundcard .


----------



## jim1961 (Apr 8, 2011)

When absorbing, you generally want to do it broadband. Thin panels nearly against the walls are not going to get you there. 



Above are 4 modeled panels

2" OC703 against wall
4" OC703 4" from wall
12" Pink Fluffy
24" Pink Fluffy


----------



## AudiocRaver (Jun 6, 2012)

Fasttracker said:


> After looking at the graph a bit more i find it very strange that there's such a steep roll-off of high frequency's starting at 10K.


Possibly, or the audio interface/sound card.



> I do seem to notice more detail in the music .


You have significantly improved your RT 60 and probably reduced the level of early reflections, which would have that effect.



> With my little knowledge about the subject i seem to think that the main problems are the peaks at 50 , 130 and around 1200 Hz plus the roll-off starting at 10K .


The rolloff at 10K is probably microphone/sound card related, no need to worry about it right now. A calibrated mic plus calibration of your sound card/audio interface will take care of that. You will want to address it before getting into equalization work. You might look for a source for Dayton Audio calibration mics, street price is about the same as the Behringer, and an individual factory calibration curve is available.

Here are some plots extracted from your last upload.



The above shows you have improved your RT 60 significantly (green), and it is at a good level, you need not do more to address it specifically.





The above spectrograms show differences between your first and second uploads. What I am curious about is the fluttery repeating light blue patterns beyond 200 ms. Looks like noise, some of it periodic, repeating. But it is better now than it was before, perhaps partly because of your treatments. You might be on the lookout for extraneous noise sources, especially low-frequency. They are easy to overlook. Resonances at 30 to 40 Hz and 120 to 150 Hz are easy to spot, the little green peaks above the red areas.



The above (green) shows your frequency response above 1 kHz with the IR window closed down to 2 ms so reflections from the room are eliminated in the analysis, and then there is minimal additional smoothing. For a pretty much unsmoothed curve of speakers without equalization applied, it is not half bad. Remember that the published curve for your monitors definitely has smoothing applied. In the frequency range shown, you probably won't do much better with room treatments, it is time for some speaker EQ.

The other (red) is the older curve with both speakers running, which explains the big notch and the other extreme variations.



Above shows the whole frequency range again, with minimal smoothing. Resonance points show up in the modal analysis at 40 Hz, 120 Hz, and at 150 Hz, and less-significant ones at 30 Hz, 70 Hz, 100 Hz.

Here is where you have to decide how much more you want to try to do with room treatment. The low frequency resonances can only be tamed with bass traps. They must contain the right material and be the right dimensions to be effective. That will be a bit of work, and will take up a bunch of your already precious space. It is the "right" way to fix those resonances, but might not be practical. The 40 Hz resonance is probably a lost cause for room treatment - wavelength is 7.5 m. (Wasn't that about the longest room dimension?) Applying equalization is your other option.

One thought: the two spaces where the slanted ceilings come down to the small vertical wall spaces at each end of your room, if nothing else is in those low spots, might be candidates for places to build a couple of bass traps. Just a thought. If they can be the right design, materials, and dimensions. If that 40 Hz resonance is a standing wave between those two low walls, it might be helped _a little_ by this idea.

The 1200 Hz peak might call for thicker and possibly different materials in some of your absorptive panels. The RT 60 curve also is slightly higher in that range. Acoustical panels can be tuned to certain frequency ranges, doing it involves the right choice of materials, dimensions, and covering materials. Again, you might be approaching the point where you call it good enough with your room treatments and do the rest with equalization.



The above is the same thing with sixth-octave smoothing, more typical of what a published curve would look like.



This last plot shows early reflections at 1.7 ms, 5.6 ms, 7.0 ms, 12 ms. Here is an example of how you would find their cause. Sound travels at approximately 1 ft./ms. Say your speakers are 5 feet from your listening position, that's 5 ms. The 5.6 ms early reflection shown above is sound that is getting there 5.6 ms later than the direct sound, has traveled 5 ms + 5.6 ms or about 11 feet to get from the speaker to a reflective point and back to the listening position. Take an 11 foot piece of string, one end anchored at the speaker, the other end at your seated head position, and you can stretch out the string, moving that "sliding midpoint" around the room to see what it touches or comes close to - which is probably the reflective surface at fault. Ideally you want zero reflections in the first 10 ms, 20 ms is even better - they can be disruptive to imaging, definition, clarity, detail. But the room size makes that pretty much impossible. Every surface within roughly 10 feet of your mix position is a possible early reflection contributor, depending on material, roughness, angle. Pardon the lack of metric dimensions. Also please pardon if you already know all this, I would rather be overly thorough than leave something out that might be useful.

Best of luck moving forward.

Edit: Calculating the wavelength for your longest room dimension, 712 cm, it equates to a 42 Hz frequency, that big resonance point. The right treatment along those low walls might help some, it is hard to say how much.


----------



## Fasttracker (Mar 7, 2012)

Hey ,
Thanks a lot for the detailled review of my REW graphs.
I'll be reading it a couple of times to understand it fully cause it's really technical 
I'm glad to hear that there are at least some points of improvement.

I did a search on the net and found a "dayton audio emm6" mic for 38 dollars at parts-express.
Have you ever ordered something from them ?
I find it a bit strange that there's a special deal on the mic but it states that the deal ends on 12/03/12.
Could it be that there's a different order of numbers in date's in the us ?
Over here it's " day/month/year" .
Also the dayton audio site seems to be down.
I'll be holding off ordering a bit till that's cleared up.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=390-801#

The noize you mentioned , could it be coming from the radiator (central heating) , the fan from the laptop , a car driving by ?
I recorded a small sample of the onkyo mic into cubase and when playing back there seems to be a very high noise level from the mic alone.

I read a trick on the internet for finding the best spot to put the subwoofer.
You have to put the woofer at the seating position and then you get behind the desk and listen around to where you get the best sound and that would be the best place to put the woofer.
Good trick?


----------



## Fasttracker (Mar 7, 2012)

The site seems to be up again.
I'll have a look around where i can order the mic.


----------



## Fasttracker (Mar 7, 2012)

, that mic is taking forever to get here .
I ordered a dayton audio emm-6 from cross spectrum labs.
I'm curious how different the measurement will be.
The project's on hold until i get the new results .
Greetz...


----------



## Fasttracker (Mar 7, 2012)

I think it's allmost here 
----
Customs clearance processing complete
January 11, 2013, 3:20 pm
BELGIUM
International Parcels
----	
Customs Clearance
January 08, 2013, 2:33 pm
BELGIUM
----	
Customs Clearance
January 06, 2013, 3:34 pm
BELGIUM
----	
Processed Through Sort Facility
January 06, 2013, 3:34 pm
BELGIUM
----	
Processed Through Sort Facility
December 20, 2012, 5:47 am
ISC NEW YORK NY(USPS) 
----	
Arrived at Sort Facility
December 20, 2012, 5:46 am
ISC NEW YORK NY(USPS) 
----	
Electronic Shipping Info Received
December 17, 2012


----------



## AudiocRaver (Jun 6, 2012)

Looking forward to seeing what you come up with...


----------



## Fasttracker (Mar 7, 2012)

New measurement.
Entirely different result.


----------



## jim1961 (Apr 8, 2011)

Could you post the actual graphs?

Cant open those files.


----------



## AudiocRaver (Jun 6, 2012)

Looks like you finally got your microphone, great, and you are getting some meaningful measurements with it.

Your RT 60 looks good. You were doing some work with absorptive panels, and the liveness of your room is pretty well under control.

There is something that looks like a comb filtering effect going on in both measurements, is there some surface close to each speaker (1 to 2 feet) causing a very early reflection?

There was some discussion about working on your main room modes, any plans there? Looks like the one at 45 Hz is worth figuring out.


----------



## AudiocRaver (Jun 6, 2012)

AudiocRaver said:


> There is something that looks like a comb filtering effect going on in both measurements, is there some surface close to each speaker (1 to 2 feet) causing a very early reflection?


To go into more detail, there are two early reflections which can be seen in each of the impulse responses. The first reflection, looking at the left side, is at 0.61 ms and is very sharp. It is causing the comb filtering affect at 820 Hz, 2500 Hz (820x3), 4100 Hz (820x5), 5700 Hz (820x7), etc. all the way up through the high frequencies. This will definitely have a negative impact on imaging and clarity.

The second reflection, at 0.77 ms, is not as high and not as sharp. It is causing the notch at 650 Hz, but its effects are almost invisible at higher frequencies because it is more dissipated.

Pardon the non-metric units, and beg pardon if you already know all this, just trying to be thorough.

((.00061 sec delay) x (1126 ft/sec)) = 0.7 ft signal delay for the reflected path

So the early reflection is getting to the listening position following a path that is 0.7 foot longer than the direct path from speaker to listening position. Say, for example, distance from speaker to LP is 6 feet, and the total distance traveled by the early reflection signal, from speaker to reflection point to LP, is 6.7 feet. An 820 Hz waveform has a wavelength of 1.4 foot, so if it is delayed by traveling an extra 0.7 foot, it will arrive out of phase with the direct signal, causing phase cancellation. The next place on the plot were you will see the effect is the frequency that is delayed 1.5 cycles by that reflected path, or 3x the first frequency, then 5x then 7x etc.

Is there a desktop or mixing board that could be causing those reflections, especially the first one? Something to look at.


----------



## Fasttracker (Mar 7, 2012)

Hey , thanks again.
Well , my desk is 1.5 feet from the speakers.
I could try removing the equipment and putting a thick blanket to see if the problem goes away.
The idea of putting bass traps at the small vertical walls will be something i'll be looking for too.
That 45hz spike could be due to the room mode like you suggested earlier.
There's a lot of empty cardboard boxes at those small vertical walls in the corner , could that be a problem?
And i'm also going to do another test on a weekend at night because i live at a traffic heavy road and i can't for the love of god do a test without a car , a bus or whatever passing by and i'm pretty sure that will show up on the measurement too.

And Jim1961 , can you not open those files in the "REW" program?


----------



## AudiocRaver (Jun 6, 2012)

Haven't heard from you for a while. Curious about how your room setup and treatment work is going. Love to hear an update.

Hoping all is well.


----------



## Fasttracker (Mar 7, 2012)

Hey , yeah well i've been cleaning and organizing my sample-library for my music.
I'm going to buy a new instrument at the end of this month so i wanna be prepared so i just have to plug it in and i can get going.
The shop also sells accoustic panels so i'm thinking of buying some when i go buy the instrument.
Do you have any suggestions on the selection on the site?
http://www.keymusic.com/en/Soundproofing

I'm also going to ask their oppinion , the site says you can " Call, chat or email with our experienced specialists for honest and personal advice "

Thanks for the interest Audiocraver


----------



## jim1961 (Apr 8, 2011)

Fasttracker said:


> And Jim1961 , can you not open those files in the "REW" program?


Yes. They opened fine.


----------

