TLA
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Posts: 32
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Post by TLA on Aug 25, 2021 14:43:13 GMT
There's an acoustic guy with a youtube video claiming "You can't lessen a null by targeting it with absorption, you can only deepen it"
This goes against everything that I know about bass in rooms and I've built and measured a few rooms.. What am I missing?
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TLA
New Member
Posts: 32
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Post by TLA on Aug 25, 2021 15:09:32 GMT
Okay, I'm looking at some measurements I made where I stacked 10 large absorbers on the floor in front of a speaker to reduce floor cancellation notch, measuring the change one at at time. It appears that the notch got a little deeper with 3 absorbers and then notch reduced significantly when I got to ten absorbers..
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Post by rock on Aug 25, 2021 20:17:22 GMT
That's very interesting.
From what I understand, nulls or notches are caused by destructive interference and peaks, conversely, by constructive interference. This is done all the time with electronic circuits in one dimensional wires (or conductors). If we lived in a one dimensional world, it should work exactly the same way as with electronic circuits (or on paper)...but our spaces have 3 dims so my guess is, that's maybe what makes things more complicated and not behave in a simple additive or subtractive process.
Now this may be just semantics but you mention the video says "You can't lessen a null by targeting it with absorption, you can only deepen it". Absorbers are generally broadband and work over a wide range of frequencies...So how can you target anything with something that affects virtually everything?
Can you send the url to that video? I'd like to see it.
Thanks!
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TLA
New Member
Posts: 32
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Post by TLA on Aug 25, 2021 21:40:54 GMT
Good info rock, thanks. I'm very interested in sorting this out. I can maybe understand how a peak can cause a null but enough broadband absorption will absorb at the boundaries and prevent the out of phase reflection from meeting the direct sound and reduce the nulls and peaks.. Looking at pictures on his website, I don't see a large amount of absorption in the rooms, so maybe that is the issue.. In My old room a there was a huge amount of Rockboard 60 or 80. www.youtube.com/watch?v=EIQVv3JB97g&lc=UgzhfeLaPZdbThZBPb94AaABAg.9RQkD1KvKW-9RTWyNIImCUThe video below is showing a null reduction of the 120hz floor notch with treatment on the walls.. That appears incorrect as the notch is created from the floor between the speaker and microphone, or is a portion of the 120hz null from the wall.. www.youtube.com/watch?v=b9u6rvWSTDM&t=147s |
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Post by Hexspa on Aug 26, 2021 1:36:47 GMT
You can reduce nulls by treating the surface that contributes to them. I don't know how he 'targets' nulls but that's how I do it and it works just fine. Think about it: no delayed reflection, no null.
You can deepen nulls with just a few panels because, like rock said, rooms have a complex set of reflections. It probably so happened that you absorbed a reflection which counteracted the null which remains. Ethan has mentioned this.
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