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Post by ossanboy on Sept 2, 2020 18:34:20 GMT
Dear Ethan, Hello how are you? I emailed you before and you told me about this forum.
About 2 years ago when i built my home theater room, you were the one who helped me about basic traps, lay out etc. I wont forget that.
I was happy for a while now I have a new speaker, and focus more into the room.
I just remodeled my room with better Bass Traps ( I use green wool/ polystyrene 25kg/m2):
Side wall: 5cm wool + 5cm air + 20cm wool + 10 air + wall Back wall: wall+ 30cm wool + 30cm gap + 10cm wool ( 120x240cm) 6 of space coupler clouds ( 120x60cm with 20cm wool) (these gives me dip!) 6 pieces of 25hz limp mass absorber ( it works) 4 corner superchunk dacron 2 middle superchunks in the celling middle of room; 120cm long. I have a new woofer box and has been testing in the new room but it still give me some dips in certain frequency. Here is a measurement, from base room (see photo), speaker movement, all the way to the space coupler panel, and LMA . Some reading is with 4 subs in the corner. Some is woofer only, I put details information in the note. REW file can be downloaded at: www.dropbox.com/s/rmp5dhsre5td5is/new%20test%20%20based%20room.mdat?dl=0Sub is crossover at 40hz, measurement is up to woofer only to 1000hz. Sub has old EQ, but woofer has NO EQ at all. My calculated room mode is at 25hz, 35hz and 60hz, but during my measurement i can only found problem at 25hz, is this correct? Which freq should I build LMA? I will have more 25hz LMA to get rid of the ridge in the waterfall. I hope Ethan or someone kindly can tell me how to improve my room, especially the dip at 52hz that I cant seem to fix and 110-125hz region. The space coupler also introduces dip at 225hz, why this happens? is it too thick?
Thank you.
Best, Dan |
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Post by ossanboy on Sept 3, 2020 15:25:41 GMT
More photos around the speaker as it seems to have SBIR at 52hz.
Thanks
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Post by Ethan Winer on Sept 3, 2020 20:34:45 GMT
The link to your REW file is broken. If you fix that I'll be able to take a look.
You have a ton of bass trapping. I can't believe the response isn't at least pretty good!
The standard frequency for crossovers to a subwoofer is 80 Hz. That takes more of the load off the mains, letting you play louder and with less distortion.
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Post by ossanboy on Sept 4, 2020 4:48:50 GMT
Halo Ethan,
I fix the link.
Thanks
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Post by ossanboy on Sept 4, 2020 14:24:41 GMT
Halo Ethan, I did another measurement today, I play around with a lot of trap and put them around the speaker. I put above, right, left, in ceiling, etc and nothing change the dip at 52hz. When I put the wool in right side, the dip in 100hz-125 is better but the dip in 223hz is worse!! Moreover when I hold the trap near the cloud in ceiling, it gives me more dip in the 217hz. So in my testing, thicker cloud gives me dip!! New measurement is at www.dropbox.com/s/uv6eami2w56yo43/wool%20position%20test.mdat?dl=0Please take a look when you have time. Thanks |
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Post by Ethan Winer on Sept 4, 2020 16:04:30 GMT
To answer your original questions, an absorber can't be too thick. So that's not the problem. The real problem is this is just what happens in small rooms! I'm sure it must sound pretty good even with what looks like an imperfect response. The problem for me is there are too many graphs, and it's not clear what's different. One is labeled 5cm wool and another is 15cm wool. Another is 2 more cloud. I don't even now what that means. Did you replace 5cm with 15cm?
Here's what I suggest: take one measurement with the microphone where your head would be. Then move the microphone 20 cm to the right and measure again, then 20 cm to the left (of the original, 40 cm total) and measure there. And do this with all of your thickest treatment in place.
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Post by ossanboy on Sept 4, 2020 17:22:09 GMT
Hi Ethan, I put more details in the note section such as speaker placement, etc. Please check it.
2 more cloud means: add 2 more cloud wool in front ( see notes)
I will do what you want soon.
Btw side wall absorber is multi layer, it has gap in the middle i think i use 15cm wool +5cm gap + 5cm wool.
Back trap is also multilayer, wall+ 30cm wool+35 gap + 10cm wool.
I use 25kg/m2 green wool (polystyrene bat), it sounds much better than rockwool in my opinion. my previous rockwool traps sound more dead
Thanks |
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Post by Ethan Winer on Sept 5, 2020 15:51:27 GMT
I don't know what "green wool (polystyrene bat)" is, but if it sounds different than rock wool that may be your problem. You need material that absorbs well at bass frequencies.
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Post by ossanboy on Sept 5, 2020 16:55:50 GMT
Here is what I use, polyester.
What do you think?
Thanks
Attachments:
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Post by Hexspa on Sept 7, 2020 16:58:20 GMT
It doesn't look like the best material of all time but you can probably make it thicker than 50mm - which is less than 2". Try sandwiching four of those panels together to make one 200mm thick and you'll probably have something useful. Like most frictional absorbers, you can lightly adhere FRK or thick paper to the room-facing surface in order to improve low frequency efficacy while maintaining a balanced response above 1kHz. Just don't do this at RFZ points.
If any of this is unclear, please review the stickies.
Thanks.
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Post by rock on Sept 7, 2020 18:27:06 GMT
Here's a list of acoustic data for many products: www.bobgolds.com/AbsorptionCoefficients.htm (this list was posted by another member on a pervious post, I found it with a quick search) Off the top of my head, your numbers seemed quite a bit under par but looking at the data confirms you could do much better with almost anything else. Your product tops out at about .75 at any freq. and the low freqs. are pretty poor too. Compare your numbers to the list and you'll see. It's true you can work with what you have but sadly, it does measure up poorly. |
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Post by ossanboy on Sept 8, 2020 3:01:26 GMT
Halo, I know it is low density and less effective but im using 20cm wool+20 air for cloud, 45cm for back wall and 25cm for side wall. ( all with gap in the middle of traps and before wall}. I think I'm allergic to rockwool so i want to avoid it if i can. Also lowest density here is 40kg.m2 with 28.000 Pa.s/m2 which is still too much!
What do you think?
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