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Post by kwarkgebak on Nov 19, 2018 20:58:33 GMT
I will have a new gear hole soon. There are 2 bedrooms to choose from to do this in. Bedroom (slaapkamer) 1 is bigger with 13m2 but not exactly rectangular. Bedroom 2 is smaller (10m2). Which room to choose from for the best acoustics? Because of the size I would prefer room 1. Is there already something so say where to place the speakers? I will definitely do measurements in both rooms when we moved in but I was just wondering whether something could be said about it already. Attachments:40782_2.pdf (106.29 KB)
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Post by Ethan Winer on Nov 19, 2018 21:22:31 GMT
The larger room is much better. It's better because it's bigger, and also because the window is on a short wall. So that will be the front of the room letting you look outside on a nice day. And the window isn't at a reflection point. It's also good that the room gets wider in the rear, though that's a smaller advantage. Then follow the advice in this short article: How To Set Up A Room
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Post by Hexspa on Nov 19, 2018 21:26:38 GMT
Larger rooms are generally better for a few reasons: longer dimensions mean a lower fundamental mode, further walls mean later and less intense reflections & also more space to put treatment and equipment. For awhile, I believed that the inherent volume mattered but I haven't found any evidence to support that; it's mostly to do with boundary distance and all its implications.
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Post by kwarkgebak on Nov 19, 2018 21:30:16 GMT
Thanks for the quick and useful replies!
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Post by kwarkgebak on Jan 28, 2019 19:47:08 GMT
Meanwhile, I am settled in the room and did a lot of measurements and experiments with placements. At the moment, I have placed 13 Hofa basstraps and 8 Hofa eco absorbers. Needless to say this gave already quite an improvement. www.dropbox.com/s/h08x4pcaa3yhlf8/SPL.PNGwww.dropbox.com/s/kinn4el05zu901e/Not%20treated-Waterfall.PNGwww.dropbox.com/s/uzon8tcnwpfq3m5/Current%20treatment-Waterfall.PNGStill there are some things I'd like to improve. Especially the dip around 56Hz as well as the 120Hz peak. I have aquired 20 pieces of 221 rockwool, 55kg/m3, 100x60x10cm. I want to create an acoustical ceiling with some of them. For this I am considering doubling the panels, this making them 20cm thick. Also I want to hang them with small chains so I can change the height/airgap. Though I understand that spreading absorbers give more overall absorption, I guess 20cm panels help better for lower frequencies. I'm not sure how dead my room will sound after I placed all rockwool panels. I am still reading and learning a lot, but please allow me to fire up some questions I have at the moment. -Will an acoustic cloud be useful to reduce the 56Hz dip and 120Hz peak? -Is it advisable to use 20cm thick absorption for the cloud? -Is it advisable to e.g. put plastic between the cloth and the rockwool to avoid making the room too dead? In theory, I guess this will make them basstraps rather than broadband absorbers. -When trying not to make the room too dull, is it advisable to use diffusion in a room as small as this?
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Post by Hexspa on Jan 28, 2019 20:16:13 GMT
Treatment helps SPL but not as much as you'd think. In my experience, placement seems to help that more. Try adjusting your listening position and speakers. If you don't have a subwoofer then get one. That should help improve your low end - you can even get two subs and balance their placement for an even better response.
As a side note, you're better off showing the SPL of both speakers combined. What's good here is that one of your speakers seems to fill in the null from the other. This is the kind of think to look out for when messing with your placements. I'd say get more treatment in the room and play around with its placement. You can do a number of different things in terms of the location of treatment, speakers, and listening position to improve your response. I can't really tell what your decay is doing because you have the graph going to too low of a dB level. Try to show just 30dB of decay from your measurement level. This is really where treatment comes into its own. I just did a video on why thinking about your sub range before the others is not good. Watch that, read or reread Ethan's articles, search for your questions around this forum, and then you should have a pretty clear idea of what next step to take. Thanks.
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Post by kwarkgebak on Jan 28, 2019 20:35:21 GMT
Thanks for the swift reply, appreciate it I'll try to experiment some more with the placement. As it is so small (and I have lots of stuff) I don't have a lot of options, but let's see what I can make of it. Thanks for the link to your video. Actually I already read the article you posted about this and found it very informative. To be sure, here's a link to the mdat file: www.dropbox.com/s/ee43vgvi5gvddzh/REW.mdat?dl=0 Hope that helps some more. Thanks again for thinking with me!
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Post by Hexspa on Jan 29, 2019 18:18:28 GMT
Glad we can help. If you don't mind, I'll wait until you put in more treatment and make further refinements before busting out my eye loop and examining your measurements. Good luck.
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Post by kwarkgebak on May 26, 2020 15:07:40 GMT
So, I am slowly picking this up again. 2 things I want to improve: a big peak around 110/160Hz and a dip around 55Hz. I read a lot and have some basic knowledge about acoustics. For the peak I purchased more rockwool. Type 221, gfr is 22kPa.s/m2. I modeled this design which seems to be pretty effective around the target frequency: www.acousticmodelling.com/mlink.php?n=4&im=1&s11=2&d11=50&v11=22000&s12=1&d12=250&s13=2&d13=50&v13=22000&s14=1&d14=50 I've played a sine at the target frequency and with an SPL meter I found that near the back wall the frequency is emphasized. I've understood that this would be a good place to put the absorber. However, all changes in frequency response and decay times are negligible. Maybe I misunderstood something? I don't have a cloud yet, but since this peak changes when I move the smartphone (with SPL meter) from front to back I've understood I should put absorbers on the front and back walls especially. To resolve the dip around 55Hz I think I need a subwoofer. I could freely place it anywhere in the room where SBIE has the least negative impact. I think that porous material is not effective enough for such a low frequency. Hence the subwoofer idea. But of course I'm open for suggestions. Btw: on www.acousticmodelling.com/ there's also an option to calculate a helmholtz absorber. Is it correct that despite porous material is used behind the perforated panel, it now functions as a pressure absorber at 1/2 waveform and should be placed straight on the wall rather than with airgap to be more effective on 1/4 waveform? What would be the pros and cons of using this to improve the dip at 55Hz instead of a subwoofer?
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Post by Ethan Winer on May 27, 2020 16:09:21 GMT
I would not use a tuned bass trap. Porous absorbers can target 55 Hz, but you need a lot of surface covered. Same for your rock wool on the back wall. How much of that wall is covered, and how thick is the rock wool?
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Post by kwarkgebak on May 28, 2020 16:50:34 GMT
Thanks for thinking with me, Ethan! The backwall has: -3 Hofa basstraps (material unknown but they are measurably effective), -5 x 221 rockwool, 10 cm with transparent foil (4 are visible, the 5th is under that red table on the floor), -6 Hofa absorbers (Basotect, 12.4kPa. The 6th is on the very left behind the 221 panel), -2 diffusers that are probably not doing much. I'll use them in my livingroom later. Also some leftover foam "basstraps". I included a picture. Please note that the cosmetic part is of later concern Attachments:
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Post by kwarkgebak on Jun 3, 2020 13:24:56 GMT
What do you guys think would be the best cost effective strategy to reduce the 110/160Hz peak?
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Post by Ethan Winer on Jun 3, 2020 13:51:23 GMT
The solution is always more bass traps. I see a lot of bare wall surface, and the wall-ceiling corner at the top is also bare. So that's next.
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Post by Hexspa on Jun 4, 2020 1:40:01 GMT
Convert the frequencies to wavelength then multiply by 1, 0.5, and 2 to find surfaces which may contribute to those peaks. Same thing goes for your 73Hz null except you multiply by 0.25, 0.75, and 1.25. Either those are speaker boundary interference or they're where you're sitting in relation to your axial modes. More absorption might help but I encourage you to experiment with positioning if you haven't.
To me, the thing that makes Ethan's suggestion of adding more panels great is that you have so many deep and narrow nulls. That's from reflections - especially above 300Hz - so you probably have too many bare surfaces or your RFZ isn't working for some reason.
Your decay is good except between about C2 and D#2 - a minor third's worth of ringing up 10dB from your target at the bottom of your bass. Ethan's suggestion will probably help but you can also try thickening whatever panels that you use if that doesn't sufficiently hasten the decay in that range.
Also, a pic of your listening position and speakers would be great.
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