Active vs Passive Loudspeakers
Its becoming increasingly clear that the highest fidelity playback is achieved with active loudspeaker design.
The largest limitation in passive loudspeakers is the passive crossover. It's large, expensive (especially in a 3-way) and is quite limiting in it's function of combining the output of separate drivers in a multi-driver system. Testing by renowned speaker maker ATC have unveiled that active implementation of a loudspeaker far outweighs any advantage gained from a very high performance outboard amp (of comparable power).
its fully understood that an active system restricts some of the 'adjustability' of a system powered by separate outboard amps but, there are advantages based on solid engineering that apply to all multi-driver loudspeakers. Here's the run down:
1) More accurate crossovers
- Active filters allow independent control of level and phase(time). This is not possible with passive crossovers. With a passive crossover any changes you make to the circuit affect both level and phase. The benefit this allows is that we can adjust for the crossover to have a perfect magnitude response and phase response. The result is that the stereo imaging is much more stable and the tonal balance of instruments is improved.
- An active filters performance is not changed by the temperature of the drive unit voice coil as they are not directly connected to them. A passive crossovers performance (filter shape and crossover frequency) will change with voice coil temperature which, increases with SPL (input power). This leads to passive loudspeaker systems having a slightly different sound when driven at low SPL compared to high SPL. The performance of active ATC systems changes very little with drive level.
- More efficient crossovers. Active crossovers do not need to use series inductors to achieve their filter shapes. Series inductors have resistance that reduces bass driver efficiency and also increases the Q of the low frequency tuning.
- More cost effective crossovers. Passive crossover networks use large, bulky and expensive components in order to deal with the high voltages from a power amplifier. Active crossovers offer better performance for lower cost.
2) Lower Intermodulation-Distortion
- As the separate amplifiers in an active system are located after the crossover, they only operate over a limited bandwidth. This reduces inter-modulation distortion and, in comparison to a passive system, even with a bi-amped or tri-amped passive system, an active system will show 15dB – 20dB lower inter-modulation distortion.
3) Improved Frequency Response and Stereo Matching
- An active system can very simply feature individual gain trims for the two, three or four amplifiers involved. This allows very simple fine tuning of the frequency response and the stereo matching. Similar matching in a passive system would involve the replacement of large, soldered passive components which, in practice, is difficult and time consuming for the manufacturer.
4) Lower Cost for Higher Performance
- Because an active system is designed, engineered and implemented by a single manufacturer into as compact a package as the design allows, cost is saved on electronics case work and packaging and the manufacturer can invest in real performance enhancing changes or pass the saving on to the customer.
For more information, please contact: AudioWise Canada