I prefer a closed IF the enclosure is sized to the characteristics of the driver. I have a book from thirty years ago with the simple calculations for determining the volume of the enclosure based on the values of the driver and the frequency range desired. If you’re wanting volume, with an enclosed speaker you will need more power. Been a long time since I built one, so I don’t remember the parameters. I expect that today, a google search would turn up an app that will do the calculation for you requiring only that you plug in the values.

When I built my last subwoofer even the best factory sound systems were seriously lacking and I was driving a LOT. I listen to mostly classical music and a good subwoofer helps reproduce the depth of the performance hall. I used a passive crossover to build it on the cheap, but an active crossover and dedicated woofer amp is much more tunable and an all around superior solution although it costs more. I had it in the rear of my 123 car at the time. I pulled out the first aid box and built a grill. It sounded really well with only a 35 Watt RMS amplifier.

Hope this somehow helps.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

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