Technical View - Subwoofer
The Z-5450 subwoofer is quite a large unit comprising of a 6.5" driver enclosed within a band pass design and also including the system's amplification stage mounted to the rear of the box along with a large heatsink to assist with heat dissipation.
The subwoofer receives 116-watts which again should be more than enough to produce solid power levels, however the decision to use a 6.5" driver leaves us scratching our heads a little. Although we can understand why a driver of this size may have been chosen and the reasoning behind such a "small" (comparatively - Logitech have used 10" in the past) unit is due to the speed at which the driver is able to move in response to signal being sent through it.
High frequencies have lots of very fast short cycles which are suited to a small fast driver i.e. a tweeter at the other end of the spectrum. Bass frequencies are inherently longer and fewer between so a small fast driver is not suited to this application at all. Somewhere in the middle we have a 6.5" driver which in most applications is considered a mid-range unit because it is small enough to produce quick punchy waveforms while being large enough to move enough air to create a longer and deeper bass note. That is, when it is paired with a band-pass enclosure in which the bass note is "exaggerated" by the box itself before exiting through a tuned port in the side.
In theory at least this should provide depth while giving the speed and response needed to crossover with the satellites at around the 150 Hz mark. The problem is that no-matter the box used coercing a 6.5" driver into moving enough air to duck below 35hz is not really feasible, just look at the fluffing around Bose do to coerce bass from their tiny sub drivers, it's not an easy problem to overcome, because bass depth is inherently going to come at the cost of mid-range response and size constraints and vice versa. Having said this we do think the box itself is competently designed. The rear of the unit features connection for the front and centre speakers along with the decoder.