Let's.
Garbage, utter garbage.
A sub that starts rolling off at ~60Hz just isn't good enough for a high-fidelity system. It's a boom box, that's all.
Note that the crossover setting was "120Hz" for those measurements. Which is just plain dishonest.
I don't know about garbage, but as with any crossover its nice to have drivers with a smooth response to around an octave above crossover. You can't always get it, but for optimal integration that is what is required.
That is why I'm always pushing for higher bandwidth drivers.
On another issue the least talked about parameter, and one of the most important issues is system Qt. For most subs it is far too high.
This does go to the issue of too much sub. High Qt subs are far from optimal, but a large room with a lot of bass leakage (openings) goes a long way to concealing the defect. However put a powerful high Qt sub in a small closed room and you have a disaster. This is where this refrain of "too much sub for the room" has originated. A low Qt sub won't care what sized room it is in.
I discussed this issue as part of a reply to some questions by Seth=L in another post and her is some of it especially concerning the Q of resonances.
Now speakers. These are mechanical devices and have both mechanical non linearity and resonant modes, both mechanical and electrical. However these ills manifest themselves they can only do via the generation of sine waves which we call harmonic distortion.
If a driver is pushed beyond it mechanical limits (xmax) then it won't produce a symmetrical sine wave, so if the output is different from the input there has to be added sines waves or harmonic distortion.
Now all speaker systems have resonance. For one every driver, because it is springy has resonance the Fs. There is also the box resonance in a sealed enclosure and the box tuning resonance in ported and ABR tupe enclosures like your Supercube I (Fb). Pipes like TLs have a pipe resonance (Fp).
Now every resonance has a spread. This spread is defined by Q, or quality of the resonances. Low Q resonances are narrow and high Q resonances wide. Resonances also have amplitude, which is their output contribution.
Now the worst resonances are high amplitude and high Q.
Now one fact to keep in mind about speakers. The Q of the total system can NEVER be lower than the Qts of the driver, which is derived from the driver mechanical and electrical resonances. Qt of the whole system will always be quite a bit higher than the Qts of the driver. That is why I personally avoid using high Qts drivers in designs.
The next issue is that Fs pretty much sets the lowest useful bass extension of the driver, and for most it will be a bit above Fs and for some quite a bit above. Some low Qts drivers can be driven below Fs, because the Q of the resonance is narrow and therefore not objectionable.
Now in a sealed enclosure the distortion is dependent on the drivers behavior, and in general distortion will rise quickly below Fs and in general it is a good idea to have a high pass filter engaged around Fs. All of the sound is produced by the movement of the driver cone or cones.
Now in ported or ABR enclosure, there is a deliberate intent to create a resonance to control cone motion and and augment the driver output with this tuning with optimal matching of Fb and Fs. In this region, the cone of the driver is pretty much stationary and almost all the output comes from the port or the ABR. The output is usually 180 degrees out of phase with the driver, so there is cancellation, but port or ABR output is so dominant it is not significant. This waveform has a huge harmonic content, but fortunately at these frequencies the ear is not very sensitive. There is because of this, significant time delay between driver and port or ABR.
Below the F3 of the system the driver decouples from the box and output falls fourth order for ports and nearer sixth order for ABRs. As output falls harmonic distortion rises off the clock.
In a TL only odd harmonics are generated and can be controlled by driver placement at the node of the dominant third harmonic and by damping. With driver Q in the 0.3 to 0.35 range and correct damping to suppress the impedance peak of tuning, the Qt of the system can be brought to the 0.5 range, and still have useful port output to reinforce the driver with comparatively very low distortion. Since the pressure in the pipe at the driver is very high, the driver excursion is very well controlled and mechanical distortion minimized. In low bass long lines however time delays are highly significant due to the time it takes the sound to traverse the line.
In my view the quality of the bass really comes down to system Qt more than anything. I find that the vast majority of systems have too high a Qt. This leads to bass blooming and excess excitation of room bass modes. The bloom and distortion from this poorly controlled resonance Qt is easily recognizable. It destroys the definition of double basses, cello strings, bass piano strings deep organ notes, bass drums and I could go on and on.
This problem is so prevalent that listeners have come to expect it, especially long time owners of audio systems. In fact a period of readjustment I find is almost always required when encountering a properly damped low Qt system. However almost always after a period of reorientation, they return to their systems for ever dissatisfied.
So low Q systems can only be built around sealed enclosures, TLs, open baffles, infinite baffles and with limitations coupled cavity systems. In the later two, Q is set by the drivers. However the driver is unconstrained and so linear driver design becomes of paramount importance. Multiple large drivers are required for infinite baffle and open baffle systems really can't achieve the dynamic range required for all sources.
So that leaves the sealed enclosure. Unfortunately when selecting a low Q driver cut off will be quite a bit higher than Fs. Therefore large amplifier power and robust drivers, with huge linear xmax numbers are required, to tolerate the huge bass boost Eq required.
Horns can get you there as well, but the enclosure are huge and distortion in horns is high.
If you have the space, that leaves the TL as my favored solution. I think they do sound better in room than sealed enclosures, because of the phenomenon of encirclement from pipes, where you have much more even distribution of sound throughout the space.
The coupled cavity has some attractions, as the designer usually was wide control over Q. However all output is from the port and relatively high and rises with the order of the design. As Q is lowered obviously the operating bandwidth narrows. If you don't believe this just go and listen to the boomy bass of the wide bandwidth of the Bose Acoustimass band pass bass modules! So I do use this, but just as augmentation to a speaker with already decent bass performance, where narrow bandwidth augmentation of an octave or less is required.
