Are REL the most Musical Subs?

@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. 

@jheppe815 Exactly. Which is why the manufacturers continue making second rate subwoofers, they are less expensive and less complicated. My point is that many great systems are better off without subwoofers then employing them in this way which is why subs have such a poor reputation in some circles. You should do it right or not do it at all. Theater is a different subject. One issue you are not quite there on. To get realistic bass at levels that will not hurt your ears you have to apply EQ to boost bass such that from 50 down to 20Hz are boosted 10 dB. This is not due to any woofer defect, it is due to the sensitivity of your ears and cutaneous sensation to low bass. Making subwoofers that are +0, -3 dB from 100 down to 20 Hz is not difficult. Getting them +10 dB 50 down to 20Hz requires digital EQ. Without EQ capability there is one other way to do it, turn the gain up on the subwoofer amplifiers or down on the main speakers while rolling out of the subs 10 Hz earlier, as in sub crossover point 90Hz, main speakers 100Hz. 

@ditusa I sort of think fast is sillier than musical, but who am I to say:-)     https://imgur.com/gallery/building-resonance-free-subwoofers-dOTF3cS

Good for you @phusis. Subwoofers should not be musical. They are to be felt more than heard. 

Rel, SVS, Rhythmik and even JL Audio are MidFi subwoofers. Aside from inexpensive enclosure construction they are expected to operate with a low pass filter only which prevents the system they are attached to from performing at its best. You need a complete 2 way crossover and steep filters available only in the digital domain for the best performance. 

The best subwoofers are passive, crossovers and amplifiers are outboard. They have balanced force design and enclosures that are made in shapes that are inherently rigid, out of materials that are self damping. A good subwoofer should be able to pound the crap out of you without any resonance. You should be able to turn the volume up to 105 dB, put your hand on the enclosure and feel absolutely no vibration or shaking as if it were disconnected.