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Acoustic Treatment - Bigger Room
Old 27th August 2019
  #31
I put the monitors now on the speaker stands close to the wall. The distance of the monitors is 130 cm an I'm also ca. 130 cm away from them.
The room is still treated provisional as shown on the photos above. As I'm a wheelchair driver it's not so easy to put the traps here and there or even move the table and I have to think about what to test next.

Hi attached the new measurements that now also go until 20 kHz. Do you think it's worse a try to face the upper wall (wall2)? I would be much closer to the side walls though.

Here's the comparison of the two measurements:

blue: Monitors on stands with 130 cm apart
brown: Monitors on the table with 110 apart

I think blue looks better, so placing them behind the table was a good decision, also the table resonates much less now. The 90 Hz whole is gone, instead I get a slight decrease at around 200Hz which get better when I move my head upwards, downwards or backwards. The tweeters are ~5 cm above ear level.

Would be great if someone can have a look at the data and give me some more hints.

Cheers
Marco




http://s000.tinyupload.com/index.php...41402273679957
Old 27th August 2019
  #32
Please make measuring L and R separately your default modus operandi. It's okay to do one measurement with both (and one with both + sub) at the end, I guess.

The amplitude response is still all over the place. The decay times are especially high in the 1 k and up range -- have you focussed on bass treatment alone for now?

The lack of symmetry is visible in the spectrogram. Could it be you have lot less treatment on the right wall? The spectrogram of the left speaker looks very different.

Your best guess is to establish as much symmetry with treatment as possible. Maybe a fake straight wall along the bottom?

Also think about buying monitors will built-in DSP (Genelec 83*, Adam S if you like ribbons). Not a cure for any problem but they might make the situation workable.
Old 27th August 2019
  #33
Quote:
Originally Posted by johannburkard View Post
Please make measuring L and R separately your default modus operandi. It's okay to do one measurement with both (and one with both + sub) at the end, I guess.

The amplitude response is still all over the place. The decay times are especially high in the 1 k and up range -- have you focussed on bass treatment alone for now?

The lack of symmetry is visible in the spectrogram. Could it be you have lot less treatment on the right wall? The spectrogram of the left speaker looks very different.

Your best guess is to establish as much symmetry with treatment as possible. Maybe a fake straight wall along the bottom?

Also think about buying monitors will built-in DSP (Genelec 83*, Adam S if you like ribbons). Not a cure for any problem but they might make the situation workable.
Thanks Johann

I have 3 bass traps on the left front corner and only 2 traps on the right front corner as shown here:



In addition there are 2 bass traps on the right rear corner, but none on the left rear side. I have to cover them with cotton before moving them as they are still only covered with thin foil. I also have leaning broadband absorbers against the wall, one at each side wall (not yet located at the first reflection points). So, the symmetry can be improved buy adjusting the positions of the traps and absorbers. Also note that the left wall is not parallel to the right wall. Beside of the table there is only little furniture in the room, no curtains, etc, no bookshelves. I guess when adding more stuff into the room the 1000 kHz range will become better, right?

The traps have a strong effect on the decay time over the whole frequency range, but the effect on the frequency response is not that good. I even have the feeling that it might became worse i.e. the peaks got broader. But how can this be the case? I moved into that room, cause the acoustics in my former room (my office) were much worse. And due to lack of space I couldn't place traps there. I can use a software EQ and lower the 70 and 130 Hz, but I originally wanted to avoid that.

Would it help to e.g. face the upper wall? I guess that will not help with the room modes or? It will just shift the problem maybe to different frequencies.

If it helps I can do more photos tomorrow that you get a better impression of the room.
Old 27th August 2019
  #34
Quote:
Originally Posted by Lilith View Post
So, the symmetry can be improved buy adjusting the positions of the traps and absorbers.
Exactly what you should do, in addition to adding more treatment.

Let REW be your guide and check the impulse response for symmetry, as well as the spectrogram.

Quote:
Originally Posted by Lilith View Post
Also note that the left wall is not parallel to the right wall.
I know. Again, with treatment, you may be able to mask some of that.

Quote:
Originally Posted by Lilith View Post
Beside of the table there is only little furniture in the room, no curtains, etc, no bookshelves. I guess when adding more stuff into the room the 1000 kHz range will become better, right?
Yes, if that stuff is acoustic treatment.

Quote:
Originally Posted by Lilith View Post
The traps have a strong effect on the decay time over the whole frequency range, but the effect on the frequency response is not that good. I even have the feeling that it might became worse i.e. the peaks got broader.
But you also experimented with different monitor placements...

Here are two very different measurements from my room. The speakers and positions are different (lots of experimentation) but maybe you can get something from it.

Acoustic Treatment - Bigger Room-untreated-vs-treated.jpg

Red is Genelec 8350s in the naked room, blue is Genelec 8340s in the room treated with 8 corner bass traps, 10 wall bass traps, 2 broadband absorbers and three GIK Monster Bass Traps. Little effect on the frequency response...

Acoustic Treatment - Bigger Room-untreated-vs-treated-2.jpg

...but a measurable effect on decay times.

So if your frequency response doesn't move much, this is why.
Attached Thumbnails
Acoustic Treatment - Bigger Room-untreated-vs-treated.jpg   Acoustic Treatment - Bigger Room-untreated-vs-treated-2.jpg  
Old 28th August 2019
  #35
Quote:
Originally Posted by johannburkard View Post
Exactly what you should do, in addition to adding more treatment.

Let REW be your guide and check the impulse response for symmetry, as well as the spectrogram.



I know. Again, with treatment, you may be able to mask some of that.



Yes, if that stuff is acoustic treatment.



But you also experimented with different monitor placements...

Here are two very different measurements from my room. The speakers and positions are different (lots of experimentation) but maybe you can get something from it.

Acoustic Treatment - Bigger Room-untreated-vs-treated.jpg

Red is Genelec 8350s in the naked room, blue is Genelec 8340s in the room treated with 8 corner bass traps, 10 wall bass traps, 2 broadband absorbers and three GIK Monster Bass Traps. Little effect on the frequency response...

Acoustic Treatment - Bigger Room-untreated-vs-treated-2.jpg

...but a measurable effect on decay times.

So if your frequency response doesn't move much, this is why.
That's crazy, but exactly what I did observe. You have more traps and a very little effect. Thanks for the hint. I found this thread where it is explained

Fixing FR vs. Decay Times

Will order a book too. How big is your room?

Cheers from Karlsruhe
Old 28th August 2019
  #36
Quote:
Originally Posted by Lilith View Post
How big is your room?
15 m².
Old 1st September 2019
  #37
Quote:
Originally Posted by Soundman2020 View Post
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?

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.

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 -
Hi Stuart,

do you think it's important also to treat the wall 5? The resonances have a much lower volume in this area, so I think I should focus on the left side of the room mainly?

Speakers are now on stands directly on the front wall with the same distance to the left and right wall, so my mixing position is fixed to 130 - 160 cm from the speakers. Within this area are don't hear a significant change of the 130 Hz mode, only when I move further into the room, but then I'm too far from the speakers and I would have to move them from the wall again, running again into cancellation issues.

Also ordered the Master Handbook of Acoustics, thanks for the tip.

Old 1st September 2019
  #38
Quote:
Originally Posted by johannburkard View Post
Exactly what you should do, in addition to adding more treatment.

Let REW be your guide and check the impulse response for symmetry, as well as the spectrogram.



I know. Again, with treatment, you may be able to mask some of that.



Yes, if that stuff is acoustic treatment.



But you also experimented with different monitor placements...

Here are two very different measurements from my room. The speakers and positions are different (lots of experimentation) but maybe you can get something from it.



Red is Genelec 8350s in the naked room, blue is Genelec 8340s in the room treated with 8 corner bass traps, 10 wall bass traps, 2 broadband absorbers and three GIK Monster Bass Traps. Little effect on the frequency response...



...but a measurable effect on decay times.

So if your frequency response doesn't move much, this is why.
These https://www.ikmultimedia.com/products/iloudmtm/ look also quite interesting. But maybe they are a bit too small for the room? Or I use a software EQ with the settings from REW and buy something like the Neumann KH 120.
Old 7th September 2019
  #39
Back again and a bit more knowing.

I used the sine wave generator in REW and looked at the volume measured by the mic (via the SPL meter menu). By this it's very easy to spot the room modes. Just set the freq to a problematic one and move the mic in the room. E.g. the 137.5 Hz mode is the 002 floor ceiling mode. It's loudest at the sitting position and gets lower in volume when I move up, down or to the left or right side. Especially when moving to the left it's gets lower in volume as the room is much more open on that side.

When I move next to the speakers it also gets a bit better, so maybe adding an absorber there would help? I also held a gym mat above the mic at the sitting position, but then it got even louder (?). Is the right antidote here to treat the ceiling?

The 71-73 Hz mode is the 020 mode between the left and right wall. The asymmetric rear wall is easy to handle: Just calculate the modes for the 320 cm part and the 780 cm part separately and you end up with:

44.2 Hz and 88.3 Hz for the 200 and 400 mode (7.8 m side), I have peaks at both frequencies. So the nasty little 45 Hz peak is really a standing wave in the big rear part of the room.

53.8 Hz for the 100 mode (3.2m side), also a peak here

Here is again the room with the dimensions.

Old 8th September 2019
  #40
Did we talk about moving the listening position to the top instead of the left already?
Old 8th September 2019
  #41
Quote:
Originally Posted by johannburkard View Post
Did we talk about moving the listening position to the top instead of the left already?
I thought about it, but the space is not enough for me (wheelchair). I need to reach the speakers from both sides to move them, etc ... I also question if this will have any influence on the 002 mode.
Old 8th September 2019
  #42
Okay, if it's not possible, we'll skip it. Looks like you'll have to have some (moveable?) treatment at the rear of the room.
Old 8th September 2019
  #43
Quote:
Originally Posted by johannburkard View Post
Okay, if it's not possible, we'll skip it. Looks like you'll have to have some (moveable?) treatment at the rear of the room.
I tought about a room divider / book shelve to separate the larger part, but not closing it completely. Mabye adding 150 cm more to the short rear wall with a heightbof 150cm. I can do some tests if it would help.
Old 10th September 2019
  #44
Treating 130 Hz floor ceiling mode with basotect

I have a rather strong (+10 dB) axial 002 mode between floor and ceiling (height 250cm) at 137.5 Hz. I put a 12cm Sonorock panel (125x65x12) on the floor at the listening position and it reduced the peak by ca. 5 dB. Now I thought about installing a basotect panel (twice 100x50×10 or 100x50x12) ca. 30 cm below the ceiling. Do you think this will decrease the enhancement at 137Hz? Putting the panel directly to the ceiling should have a little effect, but with a gap of 30cm absorption should be on the order of 70%.

Or is there any commercial lightweight solution which is better suited?
Old 11th September 2019
  #45
Lives for gear
 

Have you considered doing a proper hard-backed ceiling cloud? That can have a good effect on modal issues, as well as other issues.

- Stuart -
Old 11th September 2019
  #46
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Synthpark's Avatar
Quote:
Originally Posted by Lilith View Post
I have a rather strong (+10 dB) axial 002 mode between floor and ceiling (height 250cm) at 137.5 Hz. I put a 12cm Sonorock panel (125x65x12) on the floor at the listening position and it reduced the peak by ca. 5 dB. Now I thought about installing a basotect panel (twice 100x50×10 or 100x50x12) ca. 30 cm below the ceiling. Do you think this will decrease the enhancement at 137Hz? Putting the panel directly to the ceiling should have a little effect, but with a gap of 30cm absorption should be on the order of 70%.

Or is there any commercial lightweight solution which is better suited?
You may experience some diffraction around the absorber reducing its effect, because of it limited size.

Last edited by Synthpark; 11th September 2019 at 11:58 AM..
Old 11th September 2019
  #47
Lives for gear
Why did you create another thread?

Acoustic Treatment - Bigger Room
Old 11th September 2019
  #48
I can put it in the old thread, thought there´s already to much confusing information.

Can a moderator move it to the old one? I will then reply there.
Old 12th September 2019
  #49
Quote:
Originally Posted by Soundman2020 View Post
Have you considered doing a proper hard-backed ceiling cloud? That can have a good effect on modal issues, as well as other issues.

- Stuart -
Seems to be pretty heavy and bulky such a cloud. What's the advantage of the closed back compared to just a basotect panel?
Old 12th September 2019
  #50
Quote:
Originally Posted by Synthpark View Post
You may experience some diffraction around the absorber reducing its effect, because of it limited size.

Thanks, that's a good point I have to keep in mind.
Old 13th September 2019
  #51
Lives for gear
 

Quote:
Originally Posted by Lilith View Post
Seems to be pretty heavy and bulky such a cloud. What's the advantage of the closed back compared to just a basotect panel?
There are several advantages, actually, but the two biggest ones are that it can be part of a true RFZ-style design (which cannot be achieved with just absorption on first reflection points), and it can also have an effect "smearing" modal response a bit (lowering the Q basically) on the vertical modes. There's other things that can be accomplished with hard-backed clouds too, but I'm not going to reveal all of my secrets on-line!


- Stuart -
Old 4 weeks ago
  #52
Quote:
Originally Posted by Soundman2020 View Post
There are several advantages, actually, but the two biggest ones are that it can be part of a true RFZ-style design (which cannot be achieved with just absorption on first reflection points), and it can also have an effect "smearing" modal response a bit (lowering the Q basically) on the vertical modes. There's other things that can be accomplished with hard-backed clouds too, but I'm not going to reveal all of my secrets on-line!


- Stuart -
Thanks! Problem is that I need somebody for the installation as such a thing will be heavy. That's why my idea with the basotect panels. I also don't want this stuff falling on my head

" smearing" modal response a bit (lowering the Q basically) "

This agrees with my observation that the modal peaks in the frequency spectrum became broader and lower after treatment.
Old 3 weeks ago
  #53
Before I move the table, etc. I want to know if my idea makes any sense.

I thought to place the speaker ~62 cm from the front wall to get a SBIR hole at 137 Hz in order to compensate the floor ceiling mode at the same frequency.

Does that make any sense or isn't it a good solution?
Old 3 weeks ago
  #54
Gear Addict
 

Quote:
Originally Posted by Lilith View Post
Before I move the table, etc. I want to know if my idea makes any sense.

I thought to place the speaker ~62 cm from the front wall to get a SBIR hole at 137 Hz in order to compensate the floor ceiling mode at the same frequency.

Does that make any sense or isn't it a good solution?
Just do it! You might be inventing a new control room design method and you have the chance to make up your own cool abbreviation!

I'm not cynical, just try it, nothing is more educational than trying this kind of stuff.
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