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Acoustic Treatment - Bigger Room
Old 21st August 2019
  #1
Acoustic Treatment - Bigger Room

Hi all,

I think I need a little bit support to improve my room acoustics.

Here's the room with the table and possible speaker position near the wall and on the table. The orange bubble is me. The width of the room (from top to bottom) is ~4.5 m while the wall at the bottom is not rectangular. The length from left to the wall at the right side (next wall behind the table) is 3.2 m.


The floor is tiled with a big carpet of 3x2.5 m under the table. Here's a measurement of the empty room with very little furniture:




The speakers where placed on the table for this. Problems here are the mode at 70 Hz, 135Hz and the dip at 100 Hz (Cancellation) .

Today I placed 4 Rockwool chunks in the two left corners (in every corner 2 chunks).




It improved a little bit, but much less I expected. Green is without chunks, brown with.



I also built 5 broadband absorbers (120x63x12 cm) filled with two layers of rockwool and put them to the wall (still standing on the floor for testing) in addition to the super chunks.

That made a bigger improvement:


Brown is only super chunks, purple is super chunks + broad band absorbers (standing still on the floor next to the wall).

You can see one here at the left wall:



For all these measurements the monitors where placed on the table.

Here's a comparison between monitors near the wall (red) and on the table (green). The distances of the speaker front to the front wall are ~30 cm and 80 cm. In my opinion green looks better, so I don't think I win anything when placing the speaker on stands behind the table (?). I'm not convinced yet what's the best position as I also observed some cancellation when not placing the speakers to the wall (SBIR), but somehow with all the Rockwool this seems to be better now. I also think a distance of 80 cm is still ok. Speakers are Eris 5.



The decay times look pretty good already imo:



The question is how I still can reduce the two modes at 70 and 130 Hz. Do I also need to treat the ceiling? I wanted to avoid this to be honest.

Any suggestions would be cool .
Old 22nd August 2019
  #2
Lives for gear
you have measured with the two speakers working together. You can redo everything with one measure by speaker.
Old 22nd August 2019
  #3
Thanks you, I forgot to mention that actually this is only the left monitor that was measured. The response of the two speakers is very symmetrical.
Old 23rd August 2019
  #4
Lives for gear
We are saved.

IMHO, Your measurements with speakers on the table and near the wall (the front wall) show than the table suppress the cancelation due to the floor.

On the table against the front wall with the speakers against the front wall, what happens?
Old 23rd August 2019
  #5
Lives for gear
Post your mdat, not only screenshots
Old 23rd August 2019
  #6
Quote:
Originally Posted by dinococcus View Post
We are saved.

IMHO, Your measurements with speakers on the table and near the wall (the front wall) show than the table suppress the cancelation due to the floor.

On the table against the front wall with the speakers against the front wall, what happens?
Thanks, you mean the 200 Hz hole is a null from a floor ceiling standing wave?
For the near wall measurment I put the speaker on an ironing board, maybe that's not effective enough to prevent the null.

Doing some measurements now I load them up here.
Old 23rd August 2019
  #7
Did some measurements again.

First I started with the speakers placed on the table with a speaker-speaker distance in 110 cm and a listening distance of 110 cm. Sidewall distance of the speaker is ~178 cm and front wall distance 84 cm.



Left speaker


Right speaker

Both speaker



Here I put the left speaker on the ironing table with a front wall distance of 55 cm



and here closer to the wall with a distance of 40 cm



I didn't move the right speaker and it's also not possible for me to move the whole table further to the wall.

There's a dip at around 170Hz for the left speaker when they are positioned on the table which is not there for the right speaker. Maybe this is cause by the asymmetric rear wall?

Here's is the link the REW file: http://s000.tinyupload.com/index.php...88915901630662
Old 23rd August 2019
  #8
Lives for gear
 

Why do all of your measurements stop at 800 Hz, and others stop at 4 kHz? And why do they all start at 40 Hz? IS there a reason why you don't want to run full spectrum sweeps, from 10 Hz to 22 kHz?

Quote:
There's a dip at around 170Hz for the left speaker when they are positioned on the table
Speakers should not be on the table for many reasons. They should be on stands behind the table, up against the front wall, with no more than about 10cm between the rear corner of the speaker and the wall itself, assuming you plan to put treatment on the front wall.

Quote:
The question is how I still can reduce the two modes at 70 and 130 Hz. Do I also need to treat the ceiling?
In a control room (mixing room), you pretty much always need to treat the ceiling.

The room is VERY live, with very long decays times, (between 650 and 750 ms), and there's a lot of modal stuff and other issues in the low end, so the room will need extensive bass trapping. I can't say anything much about the rest of the spectrum, because you didn't test it!

But I would suggest that you should get rid of that large desk, find a small, low-profile desk, get some good sturdy, solid, heavy speaker stands, with the speaker on those up against the front wall, set up the geometry of the speakers and the mix position in the usual way, remove everything else from the room, and do a set of REW tests like that. Then put some superchunk-style bass traps in the four vertical corners of the room, floor to ceiling, put thick absorption across the entire rear wall, put absorptive panels on your first reflection points, and hang a cloud. Test with REW at each stage, to confirm that each device is working properly, then proceed to the next one. Once you have done all that, the room should be a whole lot better than it is now, and you can think about what to do next if you still want to carry on tuning it.

- Stuart -
Old 23rd August 2019
  #9
Thank you for the reply. I have 5 inch speakers from PRESONUS (Eris 5). They start at around 58 Hz (-10 dB), so below there's not really any signal. I didn't measure the higher frequencies yet as I'm mainly interested in the bass room modes at the moment. I can repeat this of course (although I fear to fry my tweeters :D ) .

The table is new, so it's impossible to exchange it and I also need the space. Thanks for the tip with the speaker stands. I already thought about buying those. Can you recommend a good brand? Maybe I go for these as I didn't hear good things (e.g. ringing) about metal stands: https://www.thomann.de/de/jaspers_80113sb.htm

I thought that for such small 5 inch speakers it's better to put them on the table as I'm closer (1 m). When I put them on the stands the distance is more like 1.3-1.5 m. Do you see any improvement in the data when putting them on the ironing table instead on the table?

I'm currently building 8 bass traps (42x42x100 cm) for the corners and I have 5 broadband absorbers. I would put 2 of the broadband absorbers on the side walls and one on the rear wall. I read that it's not necessary to treat the front wall. Is that correct? For a test a placed one behind the speakers and there was no difference in the frequency response. The ceiling will be treated when I know that I finally will stay in the room / flat.

The right side of the room is untreated and very empty. I will buy some book shelves next week, so I hope that this also helps to reduce the decay time. Actually I don't know how important that part of the room is for the acoustic of the left side. I don't think bass traps are needed for the right part, but I should put more regular stuff (chairs, etc....). With the bass traps the decay time will improve for sure. Without the broadband absorbers it was > 2s. Concerning the listening distance from the front wall (38% rule) I'm also completely unsure as there's the short wall behind me on the right side.

BTW the rockwool chunks that you see on the photo didn't do anything. I also put them on top of each other. Maybe they are not efficient because of the film.
Old 24th August 2019
  #10
Quote:
Originally Posted by Lilith View Post
I'm currently building 8 bass traps (42x42x100 cm) for the corners
100 cm or 10 cm? 10 cm isn't really a basstrap.
Old 24th August 2019
  #11
Lives for gear
Quote:
Originally Posted by johannburkard View Post
100 cm or 10 cm? 10 cm isn't really a basstrap.
For Gik acoustic is a bass trap
Old 24th August 2019
  #12
Quote:
Originally Posted by johannburkard View Post
100 cm or 10 cm? 10 cm isn't really a basstrap.
100 cm x 42 cm x 42 cm
Old 24th August 2019
  #13
Quote:
Originally Posted by Lilith View Post
100 cm x 42 cm x 42 cm
That sounds like a basstrap. Just make sure you're getting something for your 42 cm. Check the gas flow resistivity thread for the material you're using. Maybe 30 cm will be just as good and you can save some material?
Old 24th August 2019
  #14
Lives for gear
Treat the bass problems first, then fine-tune your listening positioning. Not the opposite.

Because of your speakers, I suspect some problems are not shown within your measurements as well...
Old 24th August 2019
  #15
Lives for gear
Before you're going crazy with superchunks, and other porous absorbers

Velocity based vs. pressure based absorbers
Old 24th August 2019
  #16
Quote:
Originally Posted by johannburkard View Post
That sounds like a basstrap. Just make sure you're getting something for your 42 cm. Check the gas flow resistivity thread for the material you're using. Maybe 30 cm will be just as good and you can save some material?
The traps are already bulit. I used Rockwool with 6 kPa ∙ s/m² . I just have to cover them with some swanboy.

Here's the ground view. Pink are the traps. 1 means 1 trap, 2 means 2 traps with a total height of 2 meters. In total I used 5 chunks of rockwool.



That's the view of the front wall:



The frequency response didn't improve much however,

Here's a measurement from the untreated room (1) green), (2) the room with just 4 packed rockwool chunks and (3) the room like it is on the photos with in total 8 bass traps (= 4.5 rockwool chunks). The green curve was measured with a lower loudness, so it might not be 100% comparable.



The decay time improved a little bit compared to (2):



Untreated they were on the order of 2 seconds!

I think I leave 2x2 chunks in the corners of the front wall. I don 't yet were to place the residual 4 chunks. Does it make sense to put them in rear wall (wall 5) of the room? It's quite a long distance from the listening position and I hardly here any room modes there. Them main issues are still the resonces at 130 and 70 Hz. Should I just put them where these modes a loudest?

Thanks for the help and cheers.
Old 24th August 2019
  #17
Quote:
Originally Posted by JayPee View Post
Treat the bass problems first, then fine-tune your listening positioning. Not the opposite.

Because of your speakers, I suspect some problems are not shown within your measurements as well...
That's what I do .. Thanks for the link. I know that a Helmholtz Resonator would help, but I wanted to treat it with bass traps first as they are more universal.
Old 24th August 2019
  #18
Quote:
Originally Posted by JayPee View Post
Treat the bass problems first, then fine-tune your listening positioning. Not the opposite.

Because of your speakers, I suspect some problems are not shown within your measurements as well...

What do you mean with the speakers?
Old 24th August 2019
  #19
Lives for gear
Quote:
Originally Posted by Lilith View Post
What do you mean with the speakers?
Do you see that lil' 45hz?


Once you add a sub, or buy a better speakers, and re-do a measurement, that lil boy will be a MAN!
Attached Thumbnails
Acoustic Treatment - Bigger Room-lil.png  

Last edited by JayPee; 25th August 2019 at 09:20 AM.. Reason: English
Old 24th August 2019
  #20
Quote:
Originally Posted by JayPee View Post
Do you see that lil' 45hz bump?
Acoustic Treatment - Bigger Room-lil.png

Once you add a sub, or buy a better speakers, and re-do a measurement, that lil boy would be a MAN!
Yup, I also realized it and really wondered as I don't hear anything at all at this frequency. Putting more bass traps is not possible at the moment. I have to find the best place for the traps I have. But under the line I'm glad I didn't buy anything, because 2 traps for ~500 € would do almost nothing. I better invest the money in better speakers ... oh wait ...
Old 24th August 2019
  #21
Lives for gear
DIY treatment...and lot of reading before doing it.
Old 24th August 2019
  #22
Quote:
Originally Posted by JayPee View Post
DIY treatment...and lot of reading before doing it.
Can you recommend a book? You think I need more traps to threat the 45Hz or a resonator? Is every room like that or is the room especially bad?
Old 24th August 2019
  #23
Quote:
Originally Posted by Lilith View Post
The frequency response didn't improve much however,
That's because the amount of treatment is still too low but if you're seeing an effect on the decay times, your treatment works.
Old 24th August 2019
  #24
The sound is much better than before and much better than in the previous room I have been. But the resonance at 130 Hz is still annoying.

May I should put all 8 traps on the front wall? That's where the bass is loudest. I try this too. Or maybe behind the table?
Old 25th August 2019
  #25
Lives for gear
 

Quote:
The traps are already bulit. I used Rockwool with 6 kPa ∙ s/m²
Which Rockwool is that?

Quote:
Yup, I also realized it and really wondered as I don't hear anything at all at this frequency. Putting more Bass Traps is not possible at the moment.
I think what JayPee was saying is that you have a mode down there, or perhaps a structural resonance, that your small speakers are not quite capable of fully triggering, but when you eventually but a sub in your room, or even just swap out your speakers for ones that go down lower, that mode is going to "wake up" and cause you big problems. So you should be taking an interest it, even though it seems small on the graph, and you don't notice it now, at some point in the future you WILL notice it... big time...


- Stuart -
Old 25th August 2019
  #26
Lives for gear
 

Quote:
Originally Posted by Lilith View Post
Can you recommend a book? You think I need more traps to threat the 45Hz or a resonator? Is every room like that or is the room especially bad?
I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. The first one will give you the background in acoustics that you need to be able to design a studio and the treatment for it, and the second one will give you the basics for actually designing and building the studio and/or treatment.

- Stuart -
Old 25th August 2019
  #27
Quote:
Originally Posted by Soundman2020 View Post
Which Rockwool is that?

I think what JayPee was saying is that you have a mode down there, or perhaps a structural resonance, that your small speakers are not quite capable of fully triggering, but when you eventually but a sub in your room, or even just swap out your speakers for ones that go down lower, that mode is going to "wake up" and cause you big problems. So you should be taking an interest it, even though it seems small on the graph, and you don't notice it now, at some point in the future you WILL notice it... big time...


- Stuart -
It's called

Rockwool Sonorock 60 mm WLG 040 here in germany. It's not the Termarock stuff which is better for broad band absorbers.
Old 25th August 2019
  #28
Lives for gear
Quote:
Originally Posted by Soundman2020 View Post
Which Rockwool is that?

I think what JayPee was saying is that you have a mode down there, or perhaps a structural resonance, that your small speakers are not quite capable of fully triggering, but when you eventually but a sub in your room, or even just swap out your speakers for ones that go down lower, that mode is going to "wake up" and cause you big problems. So you should be taking an interest it, even though it seems small on the graph, and you don't notice it now, at some point in the future you WILL notice it... big time...


- Stuart -
Old 25th August 2019
  #29
I measured with a smartphone app the loudness of the 134 Hz room mode and wrote the number into this plot. Does anyone can figure out what kind of mode that is? I think a good place for the traps is also behind the table as the loudness is quite large at this position. It also gets weaker when I go downward at the listening position (X) or when I move backwards. The right side of the room seems to be uncritical.


Height / cm dB
100 74
90 73
80 71
70 64
60 45


Before I placed the traps the maximum was at the corners. This is now a lot better. I'll order stands now.

Thanks for all the help and comments.



Old 26th August 2019
  #30
Tomorrow the stands will arrive, then I make more measurements.
In this plot it looks like the room mode peaks got broader with the absorbers, does that make sense? Or maybe it's an artifact, because the volume was not the same?



I also thought about buying a room divider to make the short wall behind the listening position longer. Would this help for the acoustics?
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