Post by Hexspa on Jul 22, 2019 18:57:14 GMT
So I have my velocity vs pressure video talking about the virtues of broadband velocity treatment and I got a comment that I can't decipher. Can anyone help me decrypt this?
Hey. In the meantime I have made some good experience in acoustics. Theoretically and practically.
There's nothing I should consider about tuned resonators. It's the only thing that makes sense. Pressure devices are for pressure problems which occor in low frequencies. A diaphragmatic absorber is narrow, but if you put in a perforated panel in front and behind the fill material you make it broadband
... so it's perfect for bass frequencies, because you can absorb 30-300 Hz with only 28 cm (11").
Rockwool or fibreglass sounds horrible as soon as you put in only one piece into the room, even if you mount wood in front of it, you still completely overdampen frequencies below 1000 Hz and that really doesn't sound good and right.
In the last month I've built my front wall with 80 cm (31,5") thick helmholtz resonators across the whole wall and they are not narrow. I simulated them with acousticmodeling.com.
They have two different tunings. One tuning is from 20-100 Hz. This resonator only has one slot and is dampened with only a towel in front of the slot.
The other tuning is from about 30-200 Hz. It has many slots with a slat width of 10 cm (3,93") and a slot width of 5 mm (0,2"). Inside there is 10cm thick rockwool directly behind the slats and slots. The cabinet walls are tripple layered (almost 8 cm thick (3,15")) mdf with 4 mm (0,16") cork in between for anti vibration. They are very powerful and my front wall is tamed now. It sounds amazing. One cabinet has 1500 liters volume and I have 6 of them.
For my sidewalls and ceiling I cannot build that thick and that's where the BDA's (broadband diaphragmatic absorber) come into place perfectly, because of there thinness. The only diss advantage of BDA's are, there are so expensive.
There's nothing I should consider about tuned resonators. It's the only thing that makes sense. Pressure devices are for pressure problems which occor in low frequencies. A diaphragmatic absorber is narrow, but if you put in a perforated panel in front and behind the fill material you make it broadband
... so it's perfect for bass frequencies, because you can absorb 30-300 Hz with only 28 cm (11").Rockwool or fibreglass sounds horrible as soon as you put in only one piece into the room, even if you mount wood in front of it, you still completely overdampen frequencies below 1000 Hz and that really doesn't sound good and right.
In the last month I've built my front wall with 80 cm (31,5") thick helmholtz resonators across the whole wall and they are not narrow. I simulated them with acousticmodeling.com.
They have two different tunings. One tuning is from 20-100 Hz. This resonator only has one slot and is dampened with only a towel in front of the slot.
The other tuning is from about 30-200 Hz. It has many slots with a slat width of 10 cm (3,93") and a slot width of 5 mm (0,2"). Inside there is 10cm thick rockwool directly behind the slats and slots. The cabinet walls are tripple layered (almost 8 cm thick (3,15")) mdf with 4 mm (0,16") cork in between for anti vibration. They are very powerful and my front wall is tamed now. It sounds amazing. One cabinet has 1500 liters volume and I have 6 of them.
For my sidewalls and ceiling I cannot build that thick and that's where the BDA's (broadband diaphragmatic absorber) come into place perfectly, because of there thinness. The only diss advantage of BDA's are, there are so expensive.
This first thing about "pressure devices are for pressure problems which occor [sic] in low frequencies." is kind of irrelevant given that all frequencies have velocity and pressure.
What about this second statement about making a pressure absorber broadband with a metasurface? He goes on to mention an 11" thickness but I don't know what he's referring to.
This thing about "one piece" of broadband sounding "horrible" and "completely overdampen(ing)" is more BS.
What I'm curious about is Helmholtz resonators being able to be tuned from 20-100Hz. This seems more broad than I thought was possible. Just wanted to see what someone experienced in this kind of treatment could say about that - I'm curious to understand these things too.
The first part seems misguided but I can't verify the second half. Please let me know whether you want to be cited when I reply to this person.
Thanks.
