Sound Wave Renderings

I recently found a Java script that does sound wave renderings and decided to put together a page of screen prints. The Java applet can be found here if you want to play with it yourself. Note that the rooms are modeled without walls except where noted. This is because I am addressing the source here and once walls come into play the thing gets incredibly complicated. Sorry the colors are so intense, I cannot control that.

This image represents a simple speaker driver radiating sound in an open space. The waves loose intensity as they move out as a real sound would get softer. No walls

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Here we introduce a large baffle behind the driver much like the front of a speaker. In this case the waves generated are small enough (higher frequency) that the edge of the baffle has little effect on the wave. Note you can already see the "V" where the pressure is greater on the outside of the semi-circle than the middle. This will be a common theme throughout the page.

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This is the same rendering with a smaller baffle. Note the waves are reaching around the baffle, ala baffle step. The larger baffle would have done the same thing with larger waves. This, in theory, will take some energy from the center part of the wave that reaches the listener.

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With the driver offset on the baffle, the waves reach edge at different times and the edge distortion is spread over different frequencies. With the previous centered baffle, the distortion is at the same frequency on both sides of the baffle. So with an offset there should be less distortion over a broader range of frequencies.

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This is an MTM style rendering without the tweeter. You can really see the lobing effect. Also consider if this were a center channel MTM. Where you sit becomes very important.

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Another MTM, this time with the drivers farther apart. There is a lot of math on how far to space drivers but I just say get them as close as possible.

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This is an MMT with no tweeter. You can see the image is a lot bigger. Note I am not saying better, just bigger. Sound is weird and sometimes things sound better with a system that does not make intuitive sense. As a beginner, I see MMT as a lot easier but have not tried either yet.

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This is the MTM setup with one driver just a tiny bid off spec. The likelihood of drivers being exact are slim, so this scenario has pretty good odds. Notice there is a big blank right at the listener position.

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Here is the MMT with one driver just a tiny bit off spec. At least the listener position is safe. But who knows what the variance really might be.

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Now we start adding walls. This is back wall only.

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Everyone says to watch out putting speakers next to a TV. I don't see much happening here. But remember we only have a back wall. It may also be worse if they are a little farther apart.

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This is four walls. It really gives some idea of how hard walls make system setup. Also, in this rendering, there was a LOT of interaction between the two speakers and between the side walls right at the speakers. In this case it did not matter where I put the speakers, they were all bad. I tried a number of shapes and variations on this and every time I ended up with a mess. Removing the back wall (behind the listener) helped a lot but the real problem is also with side walls. I also tried a number of horn type elements and that helped a little, but only if there was no back wall. Add the back wall and I still had a mess.

Please e-mail me with corrections or comments.

Copyright Peter Jay Smith 2005 Return to helarc.com

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