Full range active speakers
The definition of a full range speaker is actually two different things. The technical reference for the term refers to the actual speaker driver cone itself, how its constructed, and its ability to reproduce as much of the audible frequency range as possible.
For PA speakers, or ‘tops’ as they are also known, the term full range is used as a description of the unit as a whole, not the individual parts, so you will have either a 2 way, or 3 way full range speaker unit.
So for example in a 3 way speaker, you will have the main driver or woofer for all the low frequencies, a mid-range driver for all the low-mid and voicing frequencies, and a dedicated tweeter driver for all the high signals. These are fed through the units crossover, which is an electronic signal separator that takes the incoming audio and divides it into parts suitable for the individual drivers, ensuring they receive only the frequencies they were designed for. A 2 way system works the same, but will usually have a wider frequency woofer, and a horn type tweeter which will cover the midrange between them.
Professional active units, sometimes called ‘fully active’, go one further than this and will have separate internal amplifiers for each driver rather than feeding off a single unit. This allows for much better dynamic range and frequency response, especially in higher powered systems, as the amplifiers run far more efficiently and are far less stressed due to only needing to produce current for that particular driver.
Obviously a speaker's ability to produce certain frequencies, especially bass, or sub-bass, is greatly affected by the woofers design and physical dimensions, and also the cabinet material and its design. A speaker unit with a ten inch diameter woofer will fairly obviously not have the bass reproduction capabilities of a similar unit that has a 12 inch or 15 inch driver. This is simple physics, as the larger diameter cones can produce more mechanical energy and shift more air. Some speaker cabinet designs will incorporate ports to allow the air pressure built up inside to equalise and aid bass reproduction, though this depends on the cabinet design and component quality. Ports are generally found on units with a main driver of 10 inch or less, as larger driver units tend to behave better with a sealed enclosure design.
When choosing a speaker set that is correct for you, it's important to look at your desired outcome and expected performance. It's no good buying a set of 10 inch speakers because they are cheap, than expecting the output level of a much larger system, as this will just lead to major disappointment, or you will just destroy them. It is far better to look at a system that exceeds your needs, as it means you will be running it unstressed, which will give quality and longevity. A 100w speaker being used with all its levels full up to achieve the volume you need is not going to sound nice or last long, compared to a 300w speaker in the same position, which would only be running at around 50% its output and be quite happy doing so all night.
That being said, even at their largest size of 15inch, most PA speaker systems will struggle to reproduce very low sub-bass frequencies, certainly at high volume, as to do this requires a level of movement in the driver that would than restrict its function for producing the normal lower frequencies of the source audio. Once again, the simple physics involved means that the drivers cone cannot be in two places at once. Often to combat this, the system crossover network won't actually allow these ultra low frequencies to be passed. This causes issues as many users try to artificially compensate this cutoff by massively increasing the bass frequency gain via their mixer. This just causes the amplifier to go into distortion as you are manually overloading the input with a signal that the speaker simply cannot deal with properly. Its this action that is the main cause of driver failure in speakers.
The other problem with reproducing subsonic frequencies is the huge amounts of current being pulled from the amplifier to push and pull the driver in such large swings. The heat build up is immense, and will often lead to the system tripping its own thermal protection and shutting down. Ever been to a party or event where the system is pounding then suddenly shuts off ? Guaranteed that's the culprit.
This is where a dedicated Subwoofer comes into play.