Does anyone have experience comparing heatsoak in a sealed enclosure vs. ported? I am using 4 Dayton Audio RSS390HF-4 each in a 3.5cu ft sealed box. I intend to use them in some high power applications, putting potentially 3-400 watts per subwoofer continuously for 3-4 hours on end. I was trying to determine if heatsoak would be of any issue since the heat will be fully trapped within the sealed box, and realized that while I prefer the sound of the sealed enclosure, a ported box would have the benefit of allowing hot air inside the box to escape.
If anyone has experience with high-power, long-term use of sealed encloures, did you notice heat soak as an issue? Thanks
If anyone has experience with high-power, long-term use of sealed encloures, did you notice heat soak as an issue? Thanks
I've never heard of build up of heat (what you call 'heat soak') being a problem with loudspeaker enclosures in a domestic situation.
For an enclosure to became warm enough to be noticeable then the drivers within would surely be on the point of burning out.
I wouldn't think a port allows much hot air to escape from an enclosure since the resonating mass of air in the port oscillates to & fro within the port.
For an enclosure to became warm enough to be noticeable then the drivers within would surely be on the point of burning out.
I wouldn't think a port allows much hot air to escape from an enclosure since the resonating mass of air in the port oscillates to & fro within the port.
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Sealed enclosures and long term high power can definitely result in voice coil heating far above that of a ported enclosure, resulting in an increased impedance, which can lower output by as much as 6 dB ("power compression") before the voice coil actually fails.
Using aluminum panels to help transfer the heat, or reversing the driver so the coil vents exhaust the hot air directly to the outside air are two common approaches to reducing voice coil heat.
Between using about half the power for the same output level, and heat transfer afforded through the air exchange in ports, especially if they are located bottom and top, voice coil heating and power compression can be reduced by 6 dB or more compared to a sealed enclosure.
That said, there is also a huge difference in dynamic range between different types of music, some EDM (electronic dance music) has as little as 3 dB dynamic range <100 Hz, while 10 to 20 dB dynamic range might be more typical for most. The EDM peaking at 400 watts could also be averaging 400 watts, while other music peaking at 400 watts might only average 40 or as little as 4 watts. Obviously, a 4 watt 3.5 cubic foot "oven" won't cook like 400 watt will ;^).
If you get into trouble of heating the whole cabinet with woofer voice coils, that means that they are working too hard and you need more woofers to achieve optimum performance but without catastrophic failure waiting to happen. In other words, you won't know untill you measure it. Get an ir camera and observe while doing the test.
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I can't recall the name of the paper but there is a paper that compares sealed and various ported systems voice coil heating. The sealed system was far hotter than any of the ported systems. In the paper the voice coil temp was found from its DC resistance change. So you could run the speakers with the program material you want and use the same method to see if there is danger of overheating.
Mr. Welter is indeed correct, the sealed system will suffer more than a ported system. Surprisingly the ported systems that had undersized vents, and thus higher velocity had improved cooling over systems with an optimum vent size.
I do not recall if this was a JBL tech note or an AES paper, though I have seen the test data mentioned by kipman725.
I do not recall if this was a JBL tech note or an AES paper, though I have seen the test data mentioned by kipman725.
'Maximizing Performance from Loudspeaker Ports' agrees that turbulence in undersized ports is a good thing for cooling. It also suggests using two ports (one on near the top of the enclose, one near the bottom) to act as a chimney. It contains an experiment in which comparing heat build up is compared for different vented boxes and a closed box.
https://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf
https://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf
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