Bass traps making no difference?

[Clonkified]

Hello - I got two GIK 244s recently and have been trying to figure out where to place them, but no matter where I try, I don't seem to be getting much benefit. The only real difference is being able to reduce the 32hz reverb time and even that is very temperamental (it shoots up if I move the trap 3 inches).

I'm attaching a few pics in case anybody has some advice. Would be much appreciated!

Room - photo of the room
Compare_L - comparison of the left speaker response with (blue) and without (orange) a trap behind the speaker. Putting the trap in the corner doesn't have any noticeable effect.
Rev_L - reverb response of the left speaker with the trap behind the speaker. Putting the trap in the corner actually is worse.
Compare_R - comparison of the right speaker response with (green) and without (blue) a trap behind the speaker.
Rev_R - reverb response of the right speaker with the trap behind the speaker

Thanks!
C

[Tom Higgins]

There's a thread that said how well bass traps behind the speaker affected stereo imaging.

Have you tried the bass traps in other places? i.e. Straddling corners at the back.

I think you might notice some small changes but you need more traps to make a real difference. It's easy and cheap to build your own.

[boggy]

Originally Posted by Clonkified

Hello - I got two GIK 244s recently and have been trying to figure out where to place them, but no matter where I try, I don't seem to be getting much benefit...........

It's normal. You cannot get much improvement with two relatively small bass traps... you need (much) more.

Cheers.

Boggy

[Glenn Kuras]

I have to agree, 2 really is not going to get you as far as maybe you would like. You can try straddling the front corners or use them for the early reflection points. If you would like to give us a call we can go over your room with you.
Here is a room case study we did on adding more treatment.
http://www.gikacoustics.com/news_030709.html

[Clonkified]

OK thanks guys. I'll e-mail you Glenn for more assistance - appreciate it. I'm surprised that no matter where I place them though, only the reverb time changed. I, like many of us on here, am on a budget and am limited in space / what I can do, so it is disappointing not to get at least some benefit. I have ARC and that did a lot more it seems. Hopefully I can get some noticeable difference with that and these traps.

[Gdupproductions]

Originally Posted by boggy

It's normal. You cannot get much improvement with two relatively small bass traps... you need (much) more.

Cheers.

Boggy

I realy wouldnt say that.....2 traps off that size in a small room will realy make a diffrence.

EDIT: Shouldn't treat behind the speakers.....nothing is oing on over there.

[psykostx]

Don't go too nuts... a small room is a small room ... just like a an Ibanez is an Ibanez and a Gibson is a Gibson. I would get something for the early reflection points like another poster said, and leave the bass traps in the back corners. Also move the speakers a little off center, and closer together, and sit closer. In a room that size you are better off with them right in front of your face and not too far apart... think boombox. I would do most of my work on headphones in your situation. Try a set of Ultrasone with a good DAC ... very nice ... highly unsung. What you hear is what you get with those 'phones.

From the looks of it, your speakers are too far apart, and too close to the walls for that room...and being behind a flat desk probably isn't helping much either. Try facing the tweeters inward or just standing the speakers up... sometimes that helps a lot. Experimentation is the only real way in my experience. Everyone hears differently (different angles). The 60 degree thing is just a baseline and a geometrically sound optimum... walls complicate things.

[SörenHjalmarsson]

Originally Posted by Gdupproductions

EDIT: Shouldn't treat behind the speakers.....nothing is oing on over there.

Yes, there is...


MVH
Sören

[psykostx]

Originally Posted by SörenHjalmarsson

Yes, there is...


MVH
Sören

Indeed. Speaker boxes radiate as well as the cones...

[boggy]

Originally Posted by psykostx

Indeed. Speaker boxes radiate as well as the cones...

Not boxes, really, cones in boxed speakers radiate omnidirectional at low frequencies. Boxes can vibrate too, but their influence may be only in some colorations.

Cheers,

Boggy

[psykostx]

Originally Posted by boggy

Not boxes, really, cones in boxed speakers radiate omnidirectional at low frequencies. Boxes can vibrate too, but their influence may be only in some colorations.

Cheers,

Boggy

Yes, and diffraction occurs in the mids as well. My point was, any surface suspended on all sides is going to resonate, as the sides and back of a speaker box do. That's why expensive speakers have tons of bracing and damping, and why cheap speakers made of plastic sound like doo-doo.

[Tom Higgins]

The OP says not noticing much/any difference with 2 4" panels. I'm about to make some bass traps and this isn't encouraging!

Thus, I ask - should 6, well-placed, 6" panels make a noticeable difference in the LF response?

Hope so

EDIT: My room is approx. 13' X 10' X 8'.

[Aof]

I don't know what program are you using for measuring, but my first suggestion is you put the frequency limits on the graph below 300Hz. If you are installing bass traps, that is the area of the graph you should be looking at, not above that. The benefit of the traps can be lost in the graph if there is not much detail to see.
Then, what is your methodology for measuring? Do you use a flat omnidirectional mic? Where do you put it? At listening position? Do you make one measure or a lot an then you average?
Simply moving the mic a few inches can change the graph a lot. That's why it's generally recommended to average a series of measures.
Also, try moving your speakers and/or listening position. Use tape on the floor or something similar to mark positions.
Also, try putting your traps on the corners (ALL corners) like this:
http://forum.studiotips.com/viewtopic.php?f=8&t=534
You will find that you need a LOT of measures to be able to reach any conclusion with some validity.

[Aof]

BTW, forget about RT60, for small rooms it's meaningless.

[boggy]

Originally Posted by Aof

BTW, forget about RT60, for small rooms it's meaningless.

From my experience RT60 in small rooms isn't meaningless at all... if we get 0.2-0.4s from 250Hz to 8kHz in rooms that have volume below 100m3, this means that rooms aren't acoustically treated enough for control rooms.

We did new acoustical treatment in two small rooms, with wideband low frequency absorption and air transparent diffusers, with about 55-60% reflective (and diffuse) surfaces overall, and we get RT60 values that are very close to recommendations in this documents:

1. "Multichannel surround sound systems and operations", AES Technical Council, Document AESTD1001.1.01-10, New York.
2. “Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems”, ITU-R Recommendation BS.1116 (rev. 1), ITU, Geneva, 1997.
3. W. Hoeg, L. Christensen, R. Walker, “Subjective assessment of audio quality– the means and methods within the EBU”, EBU Technical Review Winter 1997, pp. 40-43.
4. "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic", EBU Tech. 3276 – 2nd edition May 1998, European Broadcasting Union, Geneva, Switzerland

Recommendations listed above are all that we have today, there aren't new or modified ones, which has different formulas for smaller rooms.

Rooms that we buiilt, perform very well, we get excellent mix translations, not comparable with mixes from untreated rooms with same volume, or rooms with non-optimal treatment (both of this cause too high RT60)

Our work is described in AES paper:

Davidovic Z., Petrovic B.: Acoustical Design of Control Room for Stereo and Multichannel Production and Reproduction - A Novel Approach, 129th AES Convention 2010, San Francisco, CA, USA

Part of informations you can find here:

Petrovic Bogic, Davidovic Zorica: A new acoustical design of control room for multichannel production and reproduction, 18th Telecommunications Forum TELFOR 2010, Belgrade, Serbia.

and in our white paper: here or here.




BTW, to be clear, only getting "right" RT60 in some room doesn't meant that contol room will perform well to someone... this is still one measurement and simple recommendation, and there are still a long way to good acoustics


Hope this helps

Cheers

Boggy

[Glenn Kuras]

Originally Posted by boggy

From my experience RT60 in small rooms isn't meaningless at all... if we get 0.2-0.4s from 250Hz to 8kHz in rooms that have volume below 100m3, this means that rooms aren't acoustically treated enough for control rooms.

We did new acoustical treatment in two small rooms, with wideband low frequency absorption and air transparent diffusers, with about 55-60% reflective (and diffuse) surfaces overall, and we get RT60 values that are very close to recommendations in this documents:

1. "Multichannel surround sound systems and operations", AES Technical Council, Document AESTD1001.1.01-10, New York.
2. “Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems”, ITU-R Recommendation BS.1116 (rev. 1), ITU, Geneva, 1997.
3. W. Hoeg, L. Christensen, R. Walker, “Subjective assessment of audio quality– the means and methods within the EBU”, EBU Technical Review Winter 1997, pp. 40-43.
4. "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic", EBU Tech. 3276 – 2nd edition May 1998, European Broadcasting Union, Geneva, Switzerland

Recommendations listed above are all that we have today, there aren't new or modified ones, which has different formulas for smaller rooms.

Rooms that we buiilt, perform very well, we get excellent mix translations, not comparable with mixes from untreated rooms with same volume, or rooms with non-optimal treatment (both of this cause too high RT60)

Our work is described in AES paper:

Davidovic Z., Petrovic B.: Acoustical Design of Control Room for Stereo and Multichannel Production and Reproduction - A Novel Approach, 129th AES Convention 2010, San Francisco, CA, USA

Part of informations you can find here:

Petrovic Bogic, Davidovic Zorica: A new acoustical design of control room for multichannel production and reproduction, 18th Telecommunications Forum TELFOR 2010, Belgrade, Serbia.

and in our white paper: here or here.




BTW, to be clear, only getting "right" RT60 in some room doesn't meant that contol room will perform well to someone... this is still one measurement and simple recommendation, and there are still a long way to good acoustics


Hope this helps

Cheers

Boggy

+1

[localhost127]

Originally Posted by boggy

From my experience RT60 in small rooms isn't meaningless at all... if we get 0.2-0.4s from 250Hz to 8kHz in rooms that have volume below 100m3, this means that rooms aren't acoustically treated enough for control rooms.

We did new acoustical treatment in two small rooms, with wideband low frequency absorption and air transparent diffusers, with about 55-60% reflective (and diffuse) surfaces overall, and we get RT60 values that are very close to recommendations in this documents:

1. "Multichannel surround sound systems and operations", AES Technical Council, Document AESTD1001.1.01-10, New York.
2. “Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems”, ITU-R Recommendation BS.1116 (rev. 1), ITU, Geneva, 1997.
3. W. Hoeg, L. Christensen, R. Walker, “Subjective assessment of audio quality– the means and methods within the EBU”, EBU Technical Review Winter 1997, pp. 40-43.
4. "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic", EBU Tech. 3276 – 2nd edition May 1998, European Broadcasting Union, Geneva, Switzerland

Recommendations listed above are all that we have today, there aren't new or modified ones, which has different formulas for smaller rooms.

Rooms that we buiilt, perform very well, we get excellent mix translations, not comparable with mixes from untreated rooms with same volume, or rooms with non-optimal treatment (both of this cause too high RT60)

Our work is described in AES paper:

Davidovic Z., Petrovic B.: Acoustical Design of Control Room for Stereo and Multichannel Production and Reproduction - A Novel Approach, 129th AES Convention 2010, San Francisco, CA, USA

Part of informations you can find here:

Petrovic Bogic, Davidovic Zorica: A new acoustical design of control room for multichannel production and reproduction, 18th Telecommunications Forum TELFOR 2010, Belgrade, Serbia.

and in our white paper: here or here.




BTW, to be clear, only getting "right" RT60 in some room doesn't meant that contol room will perform well to someone... this is still one measurement and simple recommendation, and there are still a long way to good acoustics


Hope this helps

Cheers

Boggy

should one worry about first fixing or addressing any issues within the ETC (time-domain), to attain the room response one wishes, and then go back and take a look at individual freq decay times, or the other way around?

it would seem that if one focuses primarily on the ETC and resolving issues discovered within the ETC, that the RT60 times should be in line (with respect to specular energy).

your thoughts?

[boggy]

Originally Posted by localhost127

should one worry about first fixing or addressing any issues within the ETC (time-domain), to attain the room response one wishes, and then go back and take a look at individual freq decay times, or the other way around?

it would seem that if one focuses primarily on the ETC and resolving issues discovered within the ETC, that the RT60 times should be in line (with respect to specular energy).

your thoughts?

If we talk about small rooms, my thought is that you must firstly resolve room modes as best as you can, using all available space, in all directions. After that, you will have room that is too dead, of course, and you must bring reflections back to the room. This can be resolved easily with slats positioned using MLS sequence, or using air transparent diffusers. In general, bringing back reflections is easy (above 250Hz)... add some reflective surfaces on top of the absorbers... et voilà!

In this point it is better to make diffusers, and this is a reason why I recommend building scattering/diffusion surfaces over absorbers, not only flat surfaces, or ordinary slat absorber construction... but even flat wooden surfaces (OSB), random positioned, can give some life in that dead room in very pleasing way.

Here are one recently finished amateur (DIY) CR that using my recommendation for slats positioned following MLS sequence.


Slats are from used wooden paletts (sanded and coated)...



With this technique you can trim your RT60 and ETC response after finished bass treatment. And you may be sure that bass response is best as you can have in your room.

In short... resolve firstly LF response in room, and this is a fundamental, all other you can do in regards of your taste and your budget, later, changing surfaces.

Hope this helps

Boggy

[fitZ]

You cannot get much improvement with two relatively small bass traps... you need (much) more.


I realy wouldnt say that.

Shouldn't treat behind the speakers.....nothing is oing on over there. ;

Yes, there is..

BTW, forget about RT60, for small rooms it's meaningless.


From my experience RT60 in small rooms isn't meaningless at all.

Isn't CR acoustic "science" wonderful. Never ceases to amaze me...even after 20 years.




Splayed walls vs rectangular
Soffits vs freestanding
Polys vs QRD's
Compression ceilings fail
Multi leaf vs 2 leaf
Hemholtz formula fail
Hangers
Slot/slats
How the Pros' do it.....er....don't ask what's behind the curtain..it's proprietary


on and on and on...........

[ciro]

Originally Posted by boggy

With this technique you can trim your RT60 and ETC response after finished bass treatment. And you may be sure that bass response is best as you can have in your room.

Boggy

Boggy, some questions, hope I´m not messing the thread, but since you started to talk about:

MLS sequence using slats is always "50/50 %"?
There´s a noticiable difference (energy arriving at mix position)comparing with 543 sequence?
Is possible to control RT 60 around 500/1000hz this way? ("where" would be the next question if you don´t mind ... )

Thank you

Ciro

[boggy]

Originally Posted by ciro

Boggy, some questions, hope I´m not messing the thread, but since you started to talk about:

We can start a new one, of course, and I will repeat what I already wrote. This one may be deleted

Originally Posted by ciro

MLS sequence using slats is always "50/50 %"?

Yes, if you don't have a gap between slats... then with gap, reflective surface can be smaller than 50%

Originally Posted by ciro

There´s a noticiable difference (energy arriving at mix position)comparing with 543 sequence?

Shame. I never tried this sequence.

Originally Posted by ciro

Is possible to control RT 60 around 500/1000hz this way? ("where" would be the next question if you don´t mind ... )

Yes.
EDIT1: ... and with using other reflective surfaces too, not at position of first reflections only.
EDIT2: You may also combine air transparent diffusers at first reflections with MLS or 543 sequence at other surfaces... because saving some costs.

Originally Posted by ciro

Thank you

NP.
Also, all other surfaces that isn't a floor but they are well below ear height, may be absorptive OR reflective, then with this you may add little more liveness or deadness in already finished room.
This isn't displayed on picture, but ceiling is also included in scattering/diffuse "plan".


Hope this helps

Cheers

Boggy

EDIT3: here is changing of RT60 from empty room (red) to fully equipped room (blue). Sorry, I don't have measurements without slats.

[ciro]

Originally Posted by boggy

EDIT2: You may also combine air transparent diffusers at first reflections with MLS or 543 sequence at other surfaces... because saving some costs.


Hope this helps

Cheers

Boggy

I have a 543 3" panel - but it was in the middle of room. I put it in my left wall RFZ point , measured the ETC , and it behaves basically the same way the broadband (at 7ms). Same to the center or rear wall. Wow...

Thanks " II "

Ciro

Edit: ops, I read too quick + my english is terrible -I think I understood wrong (slats at first reflection point) - anyway, it´s measured here, I can post...

Edit2: hey, just "listening" music , It also improves the image. I see you´re using at reflection points (pic) . It´s a "win / win" here compared to my broadband trap)

[boggy]

ciro,

here are some discussion about liveness in dead room..

Can bamboo wall treatment help dead room?

cheers

Boggy.

[ciro]

Originally Posted by boggy

ciro,

here are some discussion about liveness in dead room..

Can bamboo wall treatment help dead room?

cheers

Boggy.

Of course, and I´ll probably post some graphics there or a new thread . Thank s again Boggy!

[Aof]

Originally Posted by boggy

From my experience RT60 in small rooms isn't meaningless at all... if we get 0.2-0.4s from 250Hz to 8kHz in rooms that have volume below 100m3, this means that rooms aren't acoustically treated enough for control rooms.

We did new acoustical treatment in two small rooms, with wideband low frequency absorption and air transparent diffusers, with about 55-60% reflective (and diffuse) surfaces overall, and we get RT60 values that are very close to recommendations in this documents:

1. "Multichannel surround sound systems and operations", AES Technical Council, Document AESTD1001.1.01-10, New York.
2. “Methods for the subjective assessment of small impairments in audio systems including multichannel sound systems”, ITU-R Recommendation BS.1116 (rev. 1), ITU, Geneva, 1997.
3. W. Hoeg, L. Christensen, R. Walker, “Subjective assessment of audio quality– the means and methods within the EBU”, EBU Technical Review Winter 1997, pp. 40-43.
4. "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic", EBU Tech. 3276 – 2nd edition May 1998, European Broadcasting Union, Geneva, Switzerland

Recommendations listed above are all that we have today, there aren't new or modified ones, which has different formulas for smaller rooms.

Rooms that we buiilt, perform very well, we get excellent mix translations, not comparable with mixes from untreated rooms with same volume, or rooms with non-optimal treatment (both of this cause too high RT60)

Our work is described in AES paper:

Davidovic Z., Petrovic B.: Acoustical Design of Control Room for Stereo and Multichannel Production and Reproduction - A Novel Approach, 129th AES Convention 2010, San Francisco, CA, USA

Part of informations you can find here:

Petrovic Bogic, Davidovic Zorica: A new acoustical design of control room for multichannel production and reproduction, 18th Telecommunications Forum TELFOR 2010, Belgrade, Serbia.

and in our white paper: here or here.




BTW, to be clear, only getting "right" RT60 in some room doesn't meant that contol room will perform well to someone... this is still one measurement and simple recommendation, and there are still a long way to good acoustics


Hope this helps

Cheers

Boggy

Thanks for the info.
But I am actually referring to decay and reverberation times on the low frequencies. As far as I know, Decay times are not as diffuse and random as Reverb in larger rooms, which makes measurements in this range uncertain.

[DanDan]

This is a nitty pedantic point I know. RT60 is a defined term.
It can only exist in a diffuse space. It is appropriate and useful when referring to diffuse or mostly diffuse spaces, e.g concert halls, perhaps large swimming pools and such. Many of our working spaces are acoustically small these days. The sound field is not diffuse. I would love to see another term to describe the decay of sound in such rooms. e.g. Room Decay.
Whatever one calls it, it is far from meaningless.
Whatever word is used to describe to refer to it, when viewed in third octaves Room Decay graphs are very meaningful IMHO.
DD

[boggy]

Originally Posted by Aof

.....As far as I know, Decay times are not as diffuse and random as Reverb in larger rooms, which makes measurements in this range uncertain.

Uncertain... yes, but I don't believe that RT60 measurements are really meaningless. At least we don't have other ways to describe and measure "liveliness" in room versus frequency, and that may be very important for CR acoustics design (IMHO).
Also, at low frequencies, you may get horrible results before treatment, but I always get much better measurements when serious LF absorption is in place... and that is pretty predictable/expectable to me.

I don't like to throw away something if I didn't get anything better instead.

Cheers

Boggy