@seb_audio Sealed subwoofers rule, but the concept of speed is a fallacy when it comes to subwoofers. Smaller drivers have to move farther to displace the same volume as a larger sub driver. As the excursion distance increases the tension on the suspension increases. The suspension becomes non-linear until it can not move any farther. As the nonlinearity increases distortion increases. Suspensions in general are only linear in the first 25% of X Max best case. Larger drivers produce less distortion. You can compensate for small drivers by using them in multiples.
@bdp24 I hate to tell you this but all those designs have to compensate for serious flaws which can be avoided by design. They are ....unique. As an example, a large subwoofer driver that is operating within 25% of it's X max does not need a servo mechanism. It's distortion is already very low. Servos are a crutch for small drivers operating outside of their parameters. Also this does nothing to compensate for room issues. A sealed subwoofer does not need any dipole correction circuit. 95% of the problems encountered with subwoofers come from the enclosure and inappropriate integration schemes. What subwoofers need are large and multiple drivers, unflappable sealed enclosures, a lot of power and digital equalization to get the proper balance in a residential situation.
The best teacher is experience. I started using subwoofers in 1978 when I purchased two RH Labs units, a Dahlquist LP 1 crossover and two Kenwood LO 7M amplifiers. Selling that system was a big mistake. After that I had a set of early Velodyne subs which where pretty weak and eventually self destructed. By then I had a workshop and started making them myself. I also listened to every subwoofer I could find on display. Ported subs are for theater use only. Good subs can be used for both theater and HiFi. I tried open baffle subs given I always use Dipole ESLs or Ribbons. The response in room was impossibly lumpy. This misstep was followed by three sealed designs, the last being the most accurate I have ever heard up to about 100 dB. Going louder without distortion would require more or bigger drivers and I have not got room for either. The sad problem is that making enclosures like this are not economically feasible for manufacturers. The price would severely limit the market. I published the design so that anyone interested can make their own or perhaps have them made. Any good cabinet/furnisher maker could do it. The drivers cost $600 per enclosure and the enclosures somewhere between $10 and $20K each! Can the same performance be accomplished with much less expensive construction? I'll leave that for someone else to figure out.
@bgross You bet. It is that feeling that counts.