Active vs. passive loudspeakers – an attempt at evaluation – guest post
May 2021
by Norbert, administrator PIEGA forum
Ever since 1965, when Sennheiser first introduced active HiFi-speakers, there have been discussions on the advantages and disadvantages of this design. One thing all active loudspeakers have in common is that the amplifier is placed INSIDE the speaker. But what exactly are the pros and cons of that? That’s what I’m trying to dig into in this blog, focusing on high-quality music reproduction but disregarding battery-powered mini-systems.
Strangely enough, many of the pros and contras have changed again and again over the decades, even more so as better design tools for loudspeaker development have become available. At the same time the knowledge about the complex interaction between individual speakers and the physical laws of cabinet construction has grown continuously. Thus, the help of modern CAD systems has made it possible to develop passive loudspeakers with a linear amplitude response and impeccable readings
Conflicting goals: small cabinet but powerful bass
When it comes to bass, designers are often faced with a classic conflict of aims. While customers are looking for small cabinets with a powerful bass, the laws of physics speak against this. «Deep and loud» calls for moving a large volume of air. Thus, the smaller the membrane surface, the higher excursion is needed. At the same time the low frequency driver and the speaker cabinet have to be matched. Unfortunately, these deep and powerful bass tones can only be reproduced in a fairly large cabinet. However, active technology can help pushing these limits, so that even a fairly small cabinet can reproduce deep bass. You want to know how
How DSP makes compact active speakers sound big
The magic formula is called DSP (digital signal processor). This clever electronic component controls the interrelationship between the cabinet volume, woofer and monitoring level and manipulates it in a way that a deeper bass is possible at a relatively high level. And all this is done during operation. The DSP also features built-in protection to prevent the speaker from damage at high levels.
This kind of manipulation is not possible with passive speaker technology. Here the designer predefines the preferences in a passive cabinet, eg.: «deep bass over maximum level». Those are presets that can not be changed, let alone adjusted during operation.
«Deep and loud» is easier implemented in large speakers
In principle, this applies to large speakers too, without going into an elaborate definition of what is a large/small speaker right now. But large speakers have more favourable working conditions in the bass range than a small compact speaker. In large speakers, the objective «deep and loud» is much easier achieved. However, put into practice there is hardly any advantage whether a large loudspeaker works down to 25 Hz or down to 20 Hz. On the contrary, we may even face new problems in the interaction between loudspeaker and room. And therefore, a large loudspeaker can no longer benefit from active technology to the same extent than its smaller counterpart.
However, the many advantages of DSP should not lead to careless construction. Sloppy work and construction defects can not be overruled by clever electronics. A vibrating speaker cabinet for example is non-acceptable for active or passive speakers. The resulting deficiencies can simply not be compensated for.
Active technology becomes imperative, if speakers are to receive data signals via radio. The combination of smartphone and wireless signal transmission paired with modern amplifier electronics in a compact speaker allows for high-quality music reproduction.
CONCLUSION: Active speaker technology with digital signal processors is able to bypass physical dependencies to achieve certain desired effects.
Why many prejudices against active speakers are outdated
Doubts on the mechanical stress on the electronics and thus on shelf life and reliability used to be one key argument against active technology. Indeed, the electronics in active speakers used to be prone to failure because of the heavy vibrations inside the speaker cabinet. But this is no longer the case. Today, modern electronics can be designed to be so stable and insensitive that trouble-free operation is possible for years. Just think of modern control technology in vehicles, aircrafts and even space travel. In these fields of technology, the demands on mechanical stability are many times higher than in a speaker cabinet. Experience has also shown that the electronics of active speakers are no more liable to break down than those of «ordinary» amplifiers.
Is an active speaker right for you? Consider carefully!
Active speakers are more expensive than their passive counterparts of the same size. The explanation is simple: there is a lot of built-in technology making the development more costly in time and money. On the other hand, large amplifiers or additional playback devices such as CD players may no longer be required. Thus, it is almost impossible to compare the overall costs.
One big plus of an active speaker is its capability to bypass the speaker physics, particularly in the bass range. The ever increasing customer wish for deeper bass in smaller cabinets can only be achieved with this active technology.
In addition, in-built interfaces for modern media connection (network, digital inputs, radio transmission, etc.) are available. Meaning an active loudspeaker can transform into a complete «hi-fi all-in-one system» opening-up new perspectives for living room design.
Bottom line (with a bit of a wink): Yes, many an old-established Hi-Fi enthusiast might remember the old days when radio, record player, amplifier and speaker were all housed in one huge cabinet (in some cases even a TV!). Modern active loudspeakers are just the same. Just: the smartphone replaces the record player, the radio has become the network – and all this in a compact cabinet. It has simply become «smarter».
Musical greetings from Norbert,
who ONLY trusts his capable ears
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