Variable Acoustics

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Soundman2020
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Variable Acoustics

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Postby Soundman2020 » Wed, 2019-Sep-25, 14:36

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- Variable Acoustics -
Treatment devices that can be changed "on the fly" to modify the acoustic response of a room any time you need it.


Sometimes it is useful to have an acoustic device that can produce variable response, as you change some physical aspect of it, such as opening, closing, sliding, flipping, rotating, etc.

Here is an example of such a device that I designed for a client's iso room, that he uses for tracking a variety of instruments and vocals.

In this case, there is a central "slot wedge" that absorbs certain frequencies while reflecting others and slightly diffusing yet others. There are also two hinged "wing" modules that are normally tucked up tight against their respective "backer" modules, but they can be swung open to cover the wedges, thus exposing an entirely different set of treatment to the room. There are two devices like this in the room, and each has two wings, so there's a fairly wide range of acosutic response variability as each of the wings is opened or closed, or even left in an intermediate position.

So here's the device under construction, with the wedge already completed (sorry! I can't release the details of that, or what's inside it... it's a proprietary design... ) and the frames for the wings half open:
Variable-acoustic-01--panels--construction--half-open-SML.jpg



And another view, with the wings completely open to cover the wedge:
Variable-acoustic-02--panels--construction--fully-open--SML-ENH.JPG
Variable-acoustic-02--panels--construction--fully-open--SML-ENH.JPG (67.02 KiB) Viewed 608 times
Variable-acoustic-02--panels--construction--fully-open--SML-ENH.JPG
Variable-acoustic-02--panels--construction--fully-open--SML-ENH.JPG (67.02 KiB) Viewed 608 times


A later stage in the build, with the wings partly completed and closed over the wedge (the thing in the far corner is not part of this device: that's something else).
Variable-acoustic-03--partly-completed--SML-ENH.jpg


The final completed room, set up for recording an instrument:
Variable-acoustic-04--room--completed--SML-ENH.jpg


And the actual acoustic response tests graphs, to show what it does:
variable-acoustic-05--acoustic-rt60-plots-all-positions-t20.jpg
variable-acoustic-05--acoustic-rt60-plots-all-positions-t20.jpg (64.54 KiB) Viewed 608 times
variable-acoustic-05--acoustic-rt60-plots-all-positions-t20.jpg
variable-acoustic-05--acoustic-rt60-plots-all-positions-t20.jpg (64.54 KiB) Viewed 608 times


That shows how the decay rates change with the wings open at various angles. You can clearly see that as the wings are swung from one position to another, the room can be made "drier" and "more bassy", as the device absorbs mostly highs while not affecting lows, or it can be made "brighter" by heavily absorbing the lows while reflecting and diffusing the highs. There's a range of about 100ms for the highs and lows, and much less, about 50ms, for the mids. With all the panels open about half way, the response is fairly neutral.

One interesting thing about this design is that it does not change the frequency response of the room much: only the time-domain response.

So "variable acoustics" is a real thing, and not too hard to do. If you have a room that needs to serve several purposes, then it might be worthwhile to consider having variable devices in your room.


- Stuart -



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