room treatment suggestions

[mpw]

hi,

as we enter the new year i thought i would take a fresh look at my room and see what best can be done in a reasonable budget.

I invite suggestions in this regard from folks who have gone through all this.

a. see attached 2 pics
b. The room size is 20 ft long by 20 ft wide by 10 ft height. Of the 20 ft width.... about 7.5 feet is open area ( see the right side of the merlin speaker ).

I normally use an easy chair to listen to music at a listening distance from the speakers to be about 8 to 9 ft.

Presently the speakers are at :-

32 inches from the rear wall
Left front speaker is 36 inches from the side curtain
The speakers are 6.25 ft from each other


c. These are basically 2 flats joined together to make a larger flat and hence you will see what the speaker sees in pic 2 ( the wall column on the ceiling )

What i am aiming at :-

a. I know i need a carpet and i have one.

b. I am looking at if i could measure the room nodes and if so how ? I do not want to invest in room measurement stuff ? But i am open to getting the tools on a loaner and measure the room.

c. Even without measurement can i assume that i would need treatment at

tri corner of the front left speaker along the length of the wall ?

you will see a small tri corner bass trap in the pic 2 on the ceiling
tricorner and would it be safe to go for something like a bass trap
running the length of the tri-corner ceiling in pic 2 ?

d. For starters i was looking at getting a pair of

Aurica Corner Bass Trap, Pair: Amazon.in: Musical Instruments

and running it along both the tri corners i mentioned.

e. Ideally it would be nice to have something more colored atleast on the front left speaker tri corner

f. I am unwilling to do a DiY and aesthetics are important since this is a shared space.

thanks for looking.. and wish you a great new year 2015 !

regards
mpw

 

[koushik]

Hi mpw, a room that is 20 x 20 x 10 is as good (bad) as a cube because all of the same frequencies are emphasized by each dimensions. The room mode is 28.25 Hz. This means the first mode occurs at 28.25 Hz and multiples of that. So you will need serious bass trapping at all the corners.

I don't know whether you get serious ring at bass frequencies and boom? As far as the room dimension is concern, there should be boominess.

No bass trap is effective if it less than 4 inch across. And bass trap need significant surface area to trap bass frequencies.

I would use rockwool/glasswool and make 6" or more depth acoustic panel and hang them at the corners. Atleast 6-8 of them of a reasonal size.

A for the highs, I would start with the first reflection points on the each sides.

All the best!

 

[sud98]

Hi MPW,

Carpets should definitely help (as it looks like a vitrified tile surface).

The other big issue I see is the glass coffee table, see if it can change or move to a non-interfering place.

I suppose you can do something (a bookshelf/painting on the right side wall, assuming the curtain manages the other side. You probably know how to find the point (by using a mirror).

I have this cd(product details pages of OPPO Digital). if it helps, can get it along in my next mumbai trip

 

[koushik]

^^ These are effective but will only address high/very high frequencies.
This room needs good bass treatment to get things flatter.

 

[Hari Iyer]

@ mpw

What is the objective of this exercise. Are you looking at increasing low frequencies by room-treatment or reducing the highs to bring it in balance with the lows & mid? If the highs are over-powering the mid-bass and lows, then a simple BSC @ -3dB level can do the trick without any major investment on room-treatment.

I currently have borrowed a professional sound card (Scarlet-8i6 -Focusrite) and a balanced microphone (AKG with stands) for measuring my own speakers. If you are keen on measuring then i can check with my friend if he can loan you too for your task. Do let me know.

Cheers,

 

[mpw]

Hi mpw, a room that is 20 x 20 x 10 is as good (bad) as a cube because all of the same frequencies are emphasized by each dimensions. The room mode is 28.25 Hz. This means the first mode occurs at 28.25 Hz and multiples of that. So you will need serious bass trapping at all the corners.

I don't know whether you get serious ring at bass frequencies and boom? As far as the room dimension is concern, there should be boominess.

No bass trap is effective if it less than 4 inch across. And bass trap need significant surface area to trap bass frequencies.

I would use rockwool/glasswool and make 6" or more depth acoustic panel and hang them at the corners. Atleast 6-8 of them of a reasonal size.

A for the highs, I would start with the first reflection points on the each sides.

All the best!

koushik, hari iyer & sud98

thanks for chipping in.

there is little evidence of boominess.

Does it help that these are sealed speakers with a response at 55 Hz +/- 3dB ?

But i would not want to get into the speaker aspect and prefer to focus only on the room aspect.

If you see the 2 pics i have put up ( the carpet point is made and taken ).. i have this sneaky mind thing ( its a mind thing ) that i can by trapping / absorbing the first reflection points in both the tri corners, i could get even better sound.

Hari - IMO there is no case of highs overpowering the mids or mids overpowering the lows but this is an exercise to see what more i could do in my room apart from a carpet.

I do hope folks who have heard my setup come into this thread.

Apart from the mind thingy i hope to measure and validate the sound sent from the speakers reach the listener with minimum detrimental effects.

Maybe you can call it a touch up of the room - acoustically.

But i am clear i do not want to use equalizers and such active ways to control the sound.

sud98 - thanks for the offer i am hoping to get the measuring done with the help of a few Mumbai FM's or maybe start with Aurica bass traps and see weather i discern any improvement.

santy - you were mentioning my room is too big to be treated and i would like to have your elaboration on that given your recent DiY experience with room treatment etc..

I am contemplating an LP rack to hose my ever growing collection of records and CD's ( wall mountable type ) behind the left front speaker ( big empty space about 36 inch wide by 60 inch height ) and maybe that would do as well.

But i am put off by the dust in my home sometimes and the fact that i do not want to make the wall mounted unit with doors ( again for sound reflection sake )

correct me if i am wrong somewhere and if you have prior experience on room acoustics.

If i do use canvas paintings on the wall behind the left front speaker then i lose the space to house my LP rack

I also know the TV should not be there but i am hoping to shift it out with the consent of my folks in due course.

In my auditions and travels i have come up across many good looking acoustic panels etc.. but either no body in india distributes them or only a professional studio can afford it.

regards
mpw

 

[sdurani]

The room size is 20 ft long by 20 ft wide by 10 ft height.

Just considering the four walls and ceiling, that's a lot of reflecting surface: 1200 sq ft.

I am looking at if i could measure the room nodes and if so how ? I do not want to invest in room measurement stuff ? But i am open to getting the tools on a loaner and measure the room.

Room modes can be calculated, as kouskik already did, but that will only give you an approximation. The flexibility of your walls and any openings/archways will cause the actual room modes to be different from the approximation. The only way to know is to measure. And you can't measure without measurement gear. There is no way around it.

Even without measurement can i assume that i would need treatment at tri corner of the front left speaker along the length of the wall ? you will see a small tri corner bass trap in the pic 2 on the ceiling tricorner and would it be safe to go for something like a bass trap running the length of the tri-corner ceiling in pic 2 ?

That's not a bass trap. Your first order mode is at 28.25Hz, which has a wavelength of 40 feet. Since your speakers don't go that low, the lowest mode they're exciting is the second order mode at 56.5 Hz, which has a wavelength of 20 feet. You would need several feet thick of absorption covering at least 25% of room surface (about 300 sq ft) to have a noticeable effect at that frequency. Those tiny triangles are not going to absorb any bass.

For starters i was looking at getting a pair of

Aurica Corner Bass Trap, Pair: Amazon.in: Musical Instruments

and running it along both the tri corners i mentioned.

Of the 1200 sq ft of reflective surface in your room, those two "bass traps" combined will present an absorptive face of only 4 sq ft. That's only 0.003% of surface of your room. You can't leave 99.997% of the walls in your room unchanged and expect there to be a change in the bass response.

i am clear i do not want to use equalizers and such active ways to control the sound.

That's too bad, because at low frequencies EQ would be much more effective, allowing you to target problems much more precisely, than room treatments ever could be.

 

[vijwilso]

I recently purchased a polymax based one inch thickness panel from acoustic surfaces . This is equuvalent to compressed glasswool based panel with nrc of .9 starting from 200 hz. It does not do much to the lows. Good looking due to thin size and no risk of glass wool. I mresults are amazing with couple of testing

Sent from mobile

 

[mpw]

Just considering the four walls and ceiling, that's a lot of reflecting surface: 1200 sq ft. Room modes can be calculated, as kouskik already did, but that will only give you an approximation. The flexibility of your walls and any openings/archways will cause the actual room modes to be different from the approximation. The only way to know is to measure. And you can't measure without measurement gear. There is no way around it. That's not a bass trap. Your first order mode is at 28.25Hz, which has a wavelength of 40 feet. Since your speakers don't go that low, the lowest mode they're exciting is the second order mode at 56.5 Hz, which has a wavelength of 20 feet. You would need several feet thick of absorption covering at least 25% of room surface (about 300 sq ft) to have a noticeable effect at that frequency. Those tiny triangles are not going to absorb any bass. Of the 1200 sq ft of reflective surface in your room, those two "bass traps" combined will present an absorptive face of only 4 sq ft. That's only 0.003% of surface of your room. You can't leave 99.997% of the walls in your room unchanged and expect there to be a change in the bass response. That's too bad, because at low frequencies EQ would be much more effective, allowing you to target problems much more precisely, than room treatments ever could be.

sdurani,

many thanks for your response and wish all of you a merry christmas !

i agree to your point on measurement. I sure would like to see my room measured ( what action i take after that depends on many extraneous factors apart from audio ). For mow i want to start small.

In my experience sound is a trade off.... you attack it at one level and at another level something is robbed. Thats my experience and i am ready to be corrected with experience.

I agree with the math but what i am looking for is to treat the 2 tri corners.

Given the percentages you mentioned it will be psychological ( more likely ) but i cannot afford a dedicated room at the moment.

regards
mpw

 

[Hari Iyer]

I recently purchased a polymax based one inch thickness panel from acoustic surfaces . This is equuvalent to compressed glasswool based panel with nrc of .9 starting from 200 hz. It does not do much to the lows. Good looking due to thin size and no risk of glass wool. I mresults are amazing with couple of testing

Sent from mobile

I have also read somewhere that coir like the one used in bed mattress can also work as good sound absorbing material due to their density, honeycomb like structure where the sound can be actually trapped. Also you get them in various size, thickness and can be easily cut to fit. Also they are very light weight, water and moisture proof. They are not fire proof though. Cost is also very affordable compared to many commercial product and is easily available everywhere.

@ mpw - you can also consider as the beginning point to test as these mattress can also be brought from gaddiwala as scrap material.

 

[hydrovac]

@mpw

Its good to see the growing interest in acoustic treatment the acoustics of a listening room is arguably more important than almost anything else! I've read that larger rooms usually have more desirable acoustics than smaller rooms. I think it depends on the size of the speakers as well you would want your speakers to compliment the size of your room and vice versa.

Its not wise to underestimate the effect of acoustic treatment... but, in a typical stand mount pair of mid-field home hi-fi listening environment, in most living rooms this is not an option.

*You mentioned curtains, are they are good sound absorbing? because glass reflects sound more than anything that said, what do you mean by boominess? Is it coming from one part of the room (the source) only, the manufacturer suggests not to de-couple the speakers from stands? You don't want bass bouncing off the walls, causing phase cancellation and produce standing waves that lead to "one note bass." The bass should really be filling the room.

*Assuming there is carpet in there and thick drapes to cover up the windows, hang a heavy blanket to the back wall and experiment... the key is to create a good balance of things that absorb, diffuse and bounce off sound (broad band). That is what creates great acoustics.

I know this is kind of a generic answer but it's a good starting point at least. bass traps later

Here's the link to an interesting paper that proposes measurement standards for two-channel listening rooms.
AMS | Acoustic Frontiers

 

[mpw]

i thought this is a nice video on placement of room treatment stuff..

https://www.youtube.com/watch?v=I3q5kQjMAbc

regards

 

[sdurani]

many thanks for your response and wish all of you a merry christmas !

Merry Christmas to you and yours.

In my experience sound is a trade off.... you attack it at one level and at another level something is robbed.

That hasn't been my experience. An improvement is an improvement. It doesn't have to be more complicated than that.

Given the percentages you mentioned it will be psychological ( more likely ) but i cannot afford a dedicated room at the moment.

What do you mean by "psychological"? Are you saying you would be OK with doing something that makes you believe the sound has improved even when it hasn't actually (measurably) improved?

 

[mpw]

Are you saying you would be OK with doing something that makes you believe the sound has improved even when it hasn't actually (measurably) improved?

hi sanjay,

nope.

I used the word psychological in reference to the fact that i would not be able to do a full job of room treatment but a part one only.

I dont want to get into semantics here but in simple terms i am looking for covering up 2 exposed tri corners and using the mirror method to determine the first reflection points.

I was reading about the Auralex Lernd bass traps and found it interesting ( shape and ease of use ) or maybe this http://www.acousticalsurfaces.in/uploads/catalogue_August192014706am.pdf

regards
mpw

 

[vijwilso]

Thanks Hari .

This is the spec for 1 inch thickness panel
==============================================
Product | 125Hz | 250Hz | 500Hz | 1KHz | 2KHz | 4KHz
1" Type E400 | .44 | .80 | .73 | .99 | 1.00 | .97
==============================================

Compressed glass wool comes close to this absorption for one inch panel , but it has other issues .

I am not aware of any other DIY material that comes close to this for thin panel .

Regards

I have also read somewhere that coir like the one used in bed mattress can also work as good sound absorbing material due to their density, honeycomb like structure where the sound can be actually trapped. Also you get them in various size, thickness and can be easily cut to fit. Also they are very light weight, water and moisture proof. They are not fire proof though. Cost is also very affordable compared to many commercial product and is easily available everywhere.

@ mpw - you can also consider as the beginning point to test as these mattress can also be brought from gaddiwala as scrap material.

 

[vijwilso]

Here is one sample picture of how the panels looks like . Does not look bulky like the 2inch panels

 

[vijwilso]

NRC for the Compressed Glass wool for 1 and 2 inch

7 PCF Glass Fiber | 125Hz | 250Hz | 500Hz | 1KHz | 2KHz | 4KHz
1" |.14 | .27 | .80 | 1.11 | 1.14 | 1.14
2" |.22 | .81 | 1.24 | 1.30 | 1.21 | 1.16

 

[koushik]

Thanks Hari .

This is the spec for 1 inch thickness panel
==============================================
Product | 125Hz | 250Hz | 500Hz | 1KHz | 2KHz | 4KHz
1" Type E400 | .44 | .80 | .73 | .99 | 1.00 | .97
==============================================

Which material are you referring to over here? Mattress' coir?

 

[hydra]

Season's greetings to you, mpw!

First of all let me put in a disclaimer about my absolute lack of expertise on the technical aspects of room acoustics. What I know about room acoustics is limited to what I've read about, and tried out in my own room to resolve the issues I faced.

Since your intention is to make music sound better in a shared environment, without making it look like a studio, perhaps you should limit things to cutting echoes if any (pass a clap test in your listening area) and managing reflections to get better imaging and staging.

Perhaps you could start out with minimum acoustic material and concentrate on making your listening area virtually symmetric, as far as the speakers are concerned. And treating the reflection points, the area behind the speakers, and the wall behind you. You've got the carpet covered, and I guess the ceiling would be off limits

From the photos, I think you sit to one side/corner of the room. To the front left? At the very minimum, perhaps you could use some absorption on the first and second reflection points to your left (when you're facing the speakers), as that area is far closer to the left speaker than the right extreme wall is, to the right speaker.

Another thought: It would have been nice if you could isolate your listening area somewhat (sort of divide the room) with a virtual wall to your right on the first reflection point of the RHS speaker, symmetrically distant from the RHS speaker, by building a 5 or 6ft tall book rack/LP record rack to cover part of the area between your seating position and the speaker. I'm not completely sure if this would help (it certainly wouldn't help with any bass issues), but I think demarcating an area within a square room is what some people recommend to manage the non-standing-wave-related issues.

I saw that somebody had pointed out the glass table. I'd suggest removing that too.

Primacoustic Acoustic Solutions has fairly good looking living-room worthy panels. There's a D&D in India, based in Chennai: Primacoustic - Brands - Recording (They have put up prices for room kits on this webpage).

I do realize there are very few specific actionable things here. I'll be watching this thread with interest!

Hari Iyer, there are some people in Kerala trying to develop coir-based acoustic panels. There was an exhibition of raw prototypes in a recent exhibition of coir-based products, backed by the Coir Board. They will indeed be very low cost solutions once (uh, if) they reach final stage.

 

[mpw]

hi hydra,

seasons greetings !

i sit on an easy chair just ahead of the glass table ( pic 1 ) and sometimes i sit on a divan more on the right side of the speaker... sometimes i walk around a bit..

i think you are getting to one of the reasons i started this thread. I too am no expert on room acoustics but i do understand much of the material available on the same whatever i have read up.

In my place there is no scope for full room treatment.

Let me out things point wise so we focus better :-

a. I think i have reached a point w r t my hardware and i now need to maximise what i have.

b. Even i if were to go for better hardware ( on paper ) i would come up with the room again.

c. Given the above i am looking at a minimum amount of room treatment to allow my speakers to shine even better. At present there is little to complain about as far as the Naims and Merlins go. I am a happy camper and my music sessions can last for about 3 hours at a stretch.

d. I reckon the minimum amount of room treatment for me would involve

carpet - between the speakers - this is addressed though not in the pic. I do use the carpet when i am in the mood for a serious listen. Unfortunately the carpet cannot be a permanent affair in my home due to it being many other stake holders. I have to respect their presence and their POV.

behind left speaker - top tricorner - something like the LERND about 4 feet tall to be fixed by glue or tack from the top of the tricorner.

the second tricorner which both speakers see - pic 2 - again the LERND but about 8 feet - running horizontally.

Pic 2 - apart from the 8 ft LENRD maybe a sound absorbing panel would be nice

the wall behind my sofa - there is space for a 3 ft by 5 ft canvas painting ( very costly ) or acoustic panels - but here it is hard to get good looking ones at a reasonable price

www.acousticalsurfaces.in is a lead i got from vijwilso and i am pursuing what best i can get done.

e. I prefer an underdamped room to an overdamped room... in short given that i have sealed speakers which have better bass quality ( not quality ) i dont want to be doing too much.

Many folks mentioned to me given my room i was better off with floorstanders but i think not. I think i need to mention this as one of the approaches would be to go for a speaker commensurate with my room size and then treat the room so we are able to remove more of the unwanted stuff.

I understand well my speakers may not fill the whole room as they are standmounts and so i have to play with my seating position.

This is a conscious choice i made.

The 2 tri corners are a given IMO and thats why i am not too keen on measurements because i dont have a right side wall at all !! The left side walls are closed off by moderately thick curtains.

f. I remember sidvee has ( many moons ago ) mentioned to me to use a wooden partition 9 collapsible 0 akin to the LP rack you suggest.

g. I am contemplating an LP rack on the wall behind the left speaker and i think that would help too. The issue is that my home gets dusty and besides i sometimes want to use the wall behind my left speaker for audio memorabilia.... small stuff hung up and looking good ... so i am dithering a bit on this.
Ahh need to use the mirror test to see where the first reflection points are I hope to do this tomorrow and maybe a panel there would help.
avidyarthy mentioned to me - when would i ever get satisfied ? but this is just about the little things that one needs to have ( notwithstanding whatever hifi stuff one owns )

This year i do hope to get these minimum things done.

Lets see..

regards
mpw