# Rew and room treatments



## irombeach (Sep 7, 2010)

Hello everybody.
I'm alessandro and i need help from experts to improve my listening sessions.

i'm not looking for the moon but i'd like to optimize my room before spending money to
buy new "toys".

i like several kind of music so my chain has to be "honest" from rachmaninov to old Genesis'
cds.

my equipment is composed of musical fidelity pre-amp with four class-a monoblock amplifiers
and Triangle Celius speakers.
cd player is a mid-budget cd from musical fidelity (cd A3 24) and now i'm waiting marvellous
TRIVISTA 21 TUBE DAC.

My room is 6.30 * 5 meters and its height is of 2.30 meters :crying:
On the right side i have a big window that it's 5 meters wide .


MY GOAL IS TO USE REW to do the best i can with my room.
i've done my first mesurements but i'd like to know which graphs to read to know :

1) where i need to put my tube traps
2) where to put panel traps.

CAN SOMEONE HELP ME?:help:

thanks in advance
Alessandro


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## bpape (Sep 14, 2006)

Please post:

- A sketch of your room showing speaker and seating locations

- Frequency response

- Impulse response

- Waterfall chart.

Bryan


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## irombeach (Sep 7, 2010)

MANY THANKS BRYAN, this evening i'll prepare all needed!!!

but please, teach me what to do..... and don't do it for me, i'd like to learn how to do by myself.:innocent:

many many thanks
alessandro


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## bpape (Sep 14, 2006)

Learn to calculate modal problem locations for axial, tangential, and oblique modes.

Learn to calculate time vs distance for reflections

Understand that not all frequency response problems are modal in nature (cancellations off rear wall, SBIR, comb filtering, etc.)

Understand that frequency response is not the end-all desired solution. You also need to address reflections and decay time issues.

Keep symmetry left to right in front of you

Set the speakers in corner to maximally excite room modes and set up your seating accordingly to minimize the problems. Stay away from boundaries with your seating.

Set up the speakers for the best combination of imaging and frequency response. 

Repeat these 2 last steps (not the corner thing, just moving speakers and seating) until you find the proper balance. Seating location may change slightly after you place your speakers.

As you do this, pay specific attention to what each movement does, what ranges it impacts, which direction the movements are, etc. This will help you later on.

If you have a choice, do as much as possible to minimize the lowest frequency problems via placement, potentially at the expense of other ranges, as they're harder to deal with via treatment due to sheer wavelengths involved.

Look at what's left in terms of reflections and frequency response problems and be able to identify where they're coming from (see 1st 3 things to learn)

Treat those areas accordingly.

enjoy 

Bryan


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## irombeach (Sep 7, 2010)

:rubeyes:
ok from where do we start?

modes or reflections?

from my studies, i remember that modes are depending from room dimensions , correct?
does rew calculate modes starting from room dimensions?

with a list of room modes, if i have understood.... we can determine where (in the room) we can
find peaks of sound pressure.

cannot we put traps in these points?

:crying:


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## bpape (Sep 14, 2006)

go to www.bobgolds.com and go into the room calculator section. Input your dimensions and it will list all of the modes in the room.

Remember, modes are caused by reflections which either combine constructively or destructively to cause peaks or dips in response. Comb filtering is caused by reflections. SBIR is caused by reflections. 

Also, remember that what you're speaking of primarily are axial (one dimensional) modes. There are a lot more to consider. Also, remember that calculators predict based on a perfectly rectangular, perfectly rigid, perfectly empty room. It's theory that will get you close but others can arise, or not be there depending on a variety of factors.

You can use what you're trying to do to help better identify potential places for treatment but it's not a total solution. What about things like resonances of cabinets? Boundary interactions? Improper decay time balance?

Bryan


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## irombeach (Sep 7, 2010)

Dear Bryan,

i'm a real beginner in this field, so i am ready to follow you (if you want, obviously) in this adventure.
tomorrow i will post the sketch and the measurements as you initially told me.

but pls.... teach me!!! 
thanks ale


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## bpape (Sep 14, 2006)

Just trying to give you the method and the resources to learn yourself. This is a good exercise for anyone in any room to follow so YOU understand what is causing what in your room. This is even more important since there may be areas which you can't or don't want to treat. In this case you may change your setup to avoid problems caused by those areas (if possible).

Just understand that real rooms have problems and some are very difficult to address. 

One other point, you need to know what you're trying to accomplish. What problems are you having specifically? How is the room in general? Is it lively with concrete walls and hard floors? Is it dead with carpet and lots of curtains and overstuffed furniture? What type of sound do you lean toward? Warm? Forward? What's more important - detail, tonal balance, imaging? Not that you can't get all of those but sometimes we sacrifice a bit of one to gain another - or shift gears to do things like diffusion instead of absorption at reflection points.

Bryan


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## irombeach (Sep 7, 2010)

problems obviusly begins increasing volume (increasing db)
at low pressure, image is wide an clear but with higher volume, amplifiers
seems to be very very slow.
noise never ends and detail decrease dramatically.

now i go home to prepare documents and images for you...

i thank you 10.000 times
see you tomorrow
ale


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## bpape (Sep 14, 2006)

Not at all atypical. Most likely decay times in the bottom end are way too long which suggests the need for broadband bass control. Also, the window is likely resonating as volume increases.

Make sure you post a sketch/pics of the room.

Bryan


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## irombeach (Sep 7, 2010)

Hi Bryan, 
first of all, here enclosed the sketch....


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## irombeach (Sep 7, 2010)

the ceiling is at 2.22 meters


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## irombeach (Sep 7, 2010)

*room pictures*

these are 3 pictures of my room.
as you can see, the sliding window is giant and ceiling is lower...


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## irombeach (Sep 7, 2010)

And finnaly, these are waterfall and impulse response.
Pls...don't say i've to kill me.....


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## bpape (Sep 14, 2006)

OK. Assuming you want the best solution for the room...

Move the setup so the large glass wall is behind the speakers. That will solve a ton of problems.

Also, the way you're currently set up, you're sitting WAY too close to the wall behind you. Think more like 1.5m or so from your ears to the wall behind you.

Until you address the room in one of those 2 ways, you're going to continue to have response and decay time problems.

After you make the move and we get dialed in, when you send the impulse response, try to window it down to say 40ms. Right now, it's too coarse to really see what's happening, but it doesn't matter since the existing setup is going to be changing.

Bryan


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## irombeach (Sep 7, 2010)

Hi Bryan, 
right now i cannot move the setup, 
cannot we optimize this configuration?
it's impossible now, for me, to change speakers position...

don't leave me......


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## bpape (Sep 14, 2006)

If you can't reorient the room, then at least get the couch away from the wall behind you. That's going to be very very difficult to address since you're sitting at the place where the bass has the most buildup and you'll hear (and see in your response), every single modal problem.

Why can't you move the setup? The screen is a drop down so that's not a huge issue.

Bryan


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## irombeach (Sep 7, 2010)

I CANNOT move because i've just finished to set it up!!
any other solution?
tons of absorbers?

i re-post impulse response, can you tell me where we can see that "i'm hearing all the modals problems?"

thank you, man


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## bpape (Sep 14, 2006)

Look at your impulse response. You have reflections everywhere - and some very strong ones pretty late in time. For rule of thumb, figure 1ms = 1 ft of distance. Not exactly correct but ballpark. You have large reflections then at approx 22 and 26 ft from the sound source (total path from speaker to reflection to you).

You can have absorbers behind you and they will help some but they won't fix all of the buildup. 

Where else can we treat in the room? Remember that we need to have symmetry left to right in front of you (which is effectively the entire room when you sit against the rear wall).

As for modal problems, look at the huge peaks and dips in the response and the very long decay times. You're varying close to 30db in places.

Can you also post the frequency response? I can get the gist from the waterfall but a pure FR is easier to read more accurately - though I'm pretty sure what it's going to tell me.

Just as a test, pull the measurement mic forward into the area I suggested and take a quick frequency response measurement and take a look at the difference.

Bryan


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## irombeach (Sep 7, 2010)

we can put absorber EVERYWHERE we need.:devil:
I was thinking about "self standing" absorbers to put in front of the glass and in front of the library.
we can do something for the ceiling too.
and for rear wal we can do the same, putting absorbers directly to the wall.
For the corners, if needed, i'm prepearing 4 tube traps, made of rockwool.
1.20mt high, 39 cm diameter. 4 cm thickness.

enclosed FR. ( i took this picture from the window showing "SPL and Phase" is this correct?


surely i'll take a mesurements, just one meter forward!!!!!


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## bpape (Sep 14, 2006)

That window is fine but turn off smoothing and set the scale from 20-300Hz on the bottom axis for now.

Bryan


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## irombeach (Sep 7, 2010)

better now?


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## bpape (Sep 14, 2006)

Better - one more thing - please set the bottom axis to be LOG vs LINEAR

Bryan


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## irombeach (Sep 7, 2010)

Here enclosed the logaritmic one.

one question....
why we take meausrements from 20Hz when most of speakers does not go under 40 hz?

i thank and re-thank you for your patient.

alessandro


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## irombeach (Sep 7, 2010)

*ooops the attachment was missing....*

...sorry


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## bpape (Sep 14, 2006)

20-300 is just a general window to look at when trying to place seating, speakers, and subs as it will show not only modal issues but also positional issues. MANY speakers go below 40hz. Yours for instance are showing information well below it - even though it may be down a few db due to response of the speaker itself.

Bryan


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## bpape (Sep 14, 2006)

While the response is still not good, it's better than what it appeared to be in the previous location. Some problems are the same, some changed. This tells you that not all are related to the seating position in the front to rear (length) dimension.

See a pattern? 35, 70, 140, 210?

Bryan


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## irombeach (Sep 7, 2010)

hi Bryan this is the same measurement, 
i have only changed to logarithmic...

now i am at work........
and i cannot take a measurement.

we meet tomorrow with a new measurement taken 1 meter forward?
i begin to understand what you have in mind :flex:


yes i've seen the pattern....what does it tell us?


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## bpape (Sep 14, 2006)

OK - that's why I asked to make sure. Some things were masked and it looks different. You had said it was at 1m out rather than against the wall.

Bryan


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## irombeach (Sep 7, 2010)

pls forgive me, it's due to my poor english.
i'll take new measurement this evening.

and i only want to say that i'm learning much from your posts and
i think to "understand what you have in mind"

i mean : you ask me another graph to see if moving forward, will give us some benefits.
if yes, it means that most problems are due to the rear wall.

sorry Bryan , i've two problems: the first is the complexity of the "science" and the second
is the language....


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## bpape (Sep 14, 2006)

No problem at all. I just want to make sure I understand where you are and what happens when you move. 

While there is a lot of science, there is also just experience. The room is effectively impossible to predict 100% accurately due to a variety of factors but we'll get through it.

Bryan


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## irombeach (Sep 7, 2010)

OK Bryan, 
thanks a lot for all.
this evening i'll take a new measurement and tomorrow i'll post it.

YES....we'll get through it:hsd:


SEE you tomorrow.
thanks
ale


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## irombeach (Sep 7, 2010)

*80 cm forward...*

Hi Bryan, here enclosed new measurement.
Old position and 80 cm forward.
Only few differences in IR.....:hissyfit:

FR graphs are identical,.... and waterfalls too.


and now?


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## bpape (Sep 14, 2006)

Wasn't looking for a lot of change in impulse. Was looking to identify problems in frequency response. Please make the changes again so it's LOG scale and 20-300 range

Bryan


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## irombeach (Sep 7, 2010)

hi Bryan, 
here it is......
:innocent:


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## irombeach (Sep 7, 2010)

*ooops attachment missing.....*

here it is


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## irombeach (Sep 7, 2010)

*logarithmic one*

Hi Bryan, the same graph, logarithmic scale


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## irombeach (Sep 7, 2010)

Hi Bryan, did you see new graphs?
thanks for your patience.
ale


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## irombeach (Sep 7, 2010)

are you angry?
did i say something wrong?
alessandro


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## bpape (Sep 14, 2006)

Sorry. Been buried with work and trying to get ready to go to Denver tomorrow for Rocky Mountain Audio Fest. We're treating 3 of the rooms at the show. If anyone is going, stop by and see me in the Iris room.

Doesn't look like the movement forward was enough to really change much and that most of the problems in the frequency domain are from other areas.

I suspect some of the issues are height and width related but the room is hard to predict with the oddities, stairwell, etc. You can try moving the mic (leave it were it is front to back) to one side a couple of feet and see what changes. 

Bryan


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## JohnM (Apr 11, 2006)

Alessandro, there is something wrong with the soundcard cal traces on your plots, it does not look like you have a proper soundcard calibration. 

For your impulse response plots, open the controls panel in the Impulse graph (click the button with a gear icon on it at the right above the graph) and select the "Plot Responses Normalised" checkbox, that will make sure the initial peak in the impulse is at 100% and it will then be much easier to see the relative levels of the reflections.


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## irombeach (Sep 7, 2010)

Hi john. Thanks for your interest and your help. Can you tell me something more about errors that you see on my plots? What should I do to check calibration? Do they invalidate all measurements? Best regards. Ale


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## JohnM (Apr 11, 2006)

There is more variation in the soundcard cal trace than a properly configured soundcard would have. To check it, you should go back through the soundcard calibration steps, carefully following the information in the help files and comparing your results to those shown in the help files. If the variation is due to a setup error such as line in not being muted in the windows output mixer then that would mean the measurements are not representative of the room.


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## irombeach (Sep 7, 2010)

:rolleyesno:
:hissyfit:

i don't know what to do.
soundcard calibration remains the same....

loopback is ok
line-in (output mixer) is muted.

but response goes to 950hz to 10xx .

i've read all the help files and all the post regarding thhis problem

no way out


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## irombeach (Sep 7, 2010)

*NEW homeworks*

Hi, here enclosed , one picture of my room response.

the cyan color represents room response AS IS.
the darker one, is the spl with :

1) 1.20 meters, 40cm diameter tube trap (thickness 4cm), density 100.
2) 60cm width, 100cm height 4cm thickness panel of rockwool.

looking at the picture, my eyes can see benefits at 60Hz, i'm correct?
ok this is an empirycal test, because i've tryed to position panels
not knowing how to read graphs.

Bryan, .........i'm waiting for you to teach me :help:


the second and third images represent impulse response.
i can see very little difference from one to another.
however, ho do i have to interpret the graphs?

thanks 
ale


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## irombeach (Sep 7, 2010)

this is the waterfall:dumbcrazy:


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## DanTheMan (Oct 12, 2009)

Can we have a different viewpoint of that waterfall? From on top? 

Maybe you want to try a different set of cables to do your calibration? You might be able to get good enough results w/o a good sound card calibration. Mine was off only a fraction of a dB from 20Hz to over 19kHz. To me, no more accuracy is really needed for room measurements. A number of decent sound cards perform similarly well.

I almost wonder of the majority of your issues are the fact that you are sitting close to a lot of class and right against the rear wall if I'm reading this correct.

Dan


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## Tufelhundin (Jan 25, 2010)

Very good thread! I am also in Italy "no Italiano Alessandro", currently stationed at Aviano AB, living in Fanna. This is my 2nd time here in 6 years and I feel your pain with room response. Concrete walls, ceilings and tile floors make things very difficult. In my basement I have my equipment set up but due to needing acoustical treatment I havent done a thing....I would hate to run REW right now.

I will follow this thread with great interest to see what you do. Bouna Fortuna!

Also...where do you get Acoustic Panels/Basstraps over here???


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## irombeach (Sep 7, 2010)

Tufelhundin said:


> Very good thread! I am also in Italy "no Italiano Alessandro", currently stationed at Aviano AB, living in Fanna.


Hi man, i am not so far from you.... i live in Padova!

first of all, are you here for job? are you in the us army?
in any case.....

i will post some pictures of my acoustic panels.
they are 'home made' , with 8 cm of rockwool (thickness) and 2 cm of 'air'.
the frame is made of wood and it's all covered by fabric.
the back side is of 'poor' fabric , only to retain rockwool while the front side is made of lycra .

in the corner i've made tube traps, made of high density cilinders of rocwool.
diameter is 40 cm, height is 120 cm.

regards 
alessandro


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## Tufelhundin (Jan 25, 2010)

irombeach said:


> Hi man, i am not so far from you.... i live in Padova!
> 
> first of all, are you here for job? are you in the us army?
> in any case.....
> ...


were you able to get the rockwool and everything else at a local hardware store? I just found out Im probably going to have to make my own....I cant put a car model together with instructions....so this should be good.


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