This blog deals with one of the most frequently asked questions the specialists at Bax Music receive: What exactly is the difference between active and passive speakers? And more importantly, what should I look for when I want to pick up either of them?
Speakers and Amplifiers, Oh My!
Active speakers are equipped with an internal amp module, while their passive counterparts require an external amplifier to reproduce sound. Both systems come with their own set of pros and cons, making it difficult to label one ‘better’ than the other, especially because this also depends what they’re going to be used for. If in doubt, it’s best to seek advice before proceeding to buy any number of either active or passive speakers. Fortunately, the price gap between the two is usually not that wide.
With an amplifier built-in, active speakers are pretty much plug-and-play systems. The power capacity of the internal amp module is optimally tuned to other internal components, so there’s no need to worry about the correct speaker-amplifier power ratio. It’s also rather simple to hook up a second active speaker. All that’s needed is a sufficiently long signal cable and access to a mains power socket.
Active Full-Range Speakers
Most beginner DJs go for a set of active full-range speakers, also known as top cabinets or satellite speakers. Full-range means the speaker is capable of reproducing the full frequency spectrum, from low bass tones to highs. Since an amplifier is built in, no processing is required. All components work together optimally and connecting a set of active full-range speakers is as easy as can be.
Expanding an Active System with a Subwoofer
An active speaker system can be effortlessly expanded with a subwoofer, especially if we’re talking about a set of 12” or 15” active full-range speakers in combination with a 15” or 18” sub. This way, the speakers take care of the mid-lows, mids and highs, while the subwoofer fully focuses on the lows and ‘grounds’ itself for a rich and full bass sound. Regular full-range speakers are not as capable, since they’re busy covering the other half of the frequency range and are usually stand-mounted to deliver the highs as efficiently as possible. Grab a set of speaker poles to set up your speakers at the right height, daisy-chain the signal, and you’re good to go. Most brands offer matching subwoofers for their speakers, making the expansion even simpler.
One of the advantages of active subs, is that they’re often equipped with a built-in crossover; an electronic filter which splits an incoming signal into high and low frequencies before the signal is amplified. The highs are then passed on to your full-range speakers while the lows are routed to the amp module inside the sub. This ensures your speaker set operates as efficiently as possible and no amplification power is lost.
Active satellite speaker with active subwoofer:
Passive speakers have no internal amplification whatsoever and require an appropriate amplifier to perform optimally. They’re often used in fixed installations and by DJs and sound technicians who prefer a fully customised set-up. The most important thing to consider when it comes to passive speaker systems is the balance between the speakers and the external amplifier. You always want to make sure your amplifier has a little more power than your speakers can theoretically handle, so it doesn’t have to struggle to push its power output through them. More expensive speakers generally run a lower risk because they’re better equipped to handle any peaks in the audio they’re reproducing.
If your amplifier doesn’t pack enough power, chances are you’ll have to push it to the limit in order to get a decent amount of sound pressure. This will undoubtedly result in a lit up or flashing red ‘Clip’ indicator, meaning your amp has reached its limit and is hopelessly trying to push a little further. The internal components haven’t been built to handle such loads and will proceed to send a distorted signal to your speakers. It’s much like someone capable of lifting 40 kgs trying to lift a 20 kg rock, compared to someone capable of lifting 20 kg attempting to do the same.
Better Safe Than Sorry
That’s why the product specialists at Bax Music will generally advise you to get an amplifier that delivers slightly more power than your speakers are capable of handling. Any peaks in the signal are registered without distortion and there’s always spare horsepower available. If you want to expand your passive set-up with a subwoofer, your best bet is an amp rack. An amp rack is usually a double-door flight case, in which you can easily install and link up multiple amps and peripheral devices.
Flightcase with 19 inch crossover and amplifiers:
Generally speaking, two amplifiers are used: one for the passive speakers and one for the subs. Just like an active system, the signal ought to be split via a 19” crossover before being amplified.
Crossover example set-up:
The result is a system comprised of separate passive speakers and an amp rack fitted with amplifiers and peripheral gear.
Picking the Right Amplifier for Your Speakers
Say you’ve got your eyes on an 8 Ohm, 300W RMS speaker. As a rule of thumb, you’re going to roughly need one-and-a-half to twice as much power when picking your amp. This means you’ll need one that’s capable of delivering 450-600W RMS at 8 Ohms, per side. It’s slightly different for subs, since a decent amount of power is required to reproduce lows and the round speaker inside, the woofer, must be able to move back and forth. To make sure you’re on the safe side, get an amplifier that offers twice the capacity in Watts RMS compared to the sub.
What Does RMS Actually Mean?
RMS stands for Root Mean Square and is measured in Watts. This means that the power capacity of an amp, or the load capacity of a speaker, is calculated by using a sine. A sine is a static tone, much like a hum caused by your speakers. Sine frequency is almost always used and measured at 1000 Hz (which explains the “at 1 kHz” often found in the technical specifications section). The sound of music reproduced by amps and speakers, however, differs greatly from a static sine. Music is dynamic and (usually) consists of highs and lows, which are easily picked up and reproduced by speaker components and makes it possible to use a more powerful amplifier.
Do Ohms Matter? And What is the Difference Between 4 and 8 Ohm Versions?
Ohms are used to measure the resistance of a speaker, which usually come in 4-Ohm or 8-Ohm models. So before you go and buy an amp for your passive speakers, it’d be wise to check whether they have an impedance of 4 or 8 Ohms. You can find this information listed in the specifications section of every passive speaker featured on the Bax Music website.
Power Capacity versus Resistance
An amplifier can deliver more power at lower resistances but there’s certainly a point of no return involved here. Most entry-level amps can easily handle a 4 or 8 Ohm impedance but, turn this down to 2, and it becomes a different story. If a given sub can provide 2x 500W at 8 Ohms, it can usually do 2x 750-1,000W at 4 Ohms. There can be some give and take depending on whether it’s a budget or high-end model.
8 Ohms or 4 Ohms?
Most speakers you come across will be 8-Ohm versions, despite the fact that 4-Ohm models seem better on paper. How does this work? Simple. Many passive speakers are fitted with an additional output for the second speaker. This can come in handy if you’re using two speakers per side or if you want to provide a seated audience with background music. Two speakers are placed at the front and another two are placed halfway down the room so the volume of the first two doesn’t have to be turned up to eleven. This way, no additional amplifier required and every member of the audience will be able to enjoy the show.
Example set-up in parallel:
What to Watch for When Daisy-Chaining
Well, for starters, you certainly can’t infinitely daisy-chain speakers together. That’s because when you connect two 300-Watt, 8-Ohm speakers, the resistance is halved, while the load capacity is doubled. In other words, you’ll need to amplify 600 Watts at 4 Ohms in this particular case.
When daisy-chaining three or more 8-Ohm speakers, the electrical resistance will get reduced to 2 Ohms or less and your amplifier will very quickly get overloaded and likely damaged. Besides daisy-chaining, there’s the option to use wire terminals to connect your speakers to each other in series. Wire terminals are wire clamps found on the back of speakers and are used to clamp in stripped cable cores. You can also often find these round the back of Hi-Fi stereo systems.
What they basically do, is form a circle with the positive (+) and negative (-) outputs of your amplifier. Route the positive (+) wire core from your amp to the first speaker and proceed to connect the positive (+) output of the first speaker to the positive (+) output of the second. Then, take the negative (-) output of your second speaker and route it back to the amplifier. Surprisingly, both the resistance and the load capacity gets doubled now. Let’s take two 300W, 8-Ohm speakers and connect them in series. Instead of 1x 300W at 8 Ohms, we’re now looking at 1x 600W at 16 Ohms. Serial connections aren’t often used but can certainly serve as a back-up plan in case of an emergency.
Can amplifiers handle 16 Ohms? They can, but as described above, higher resistance leads to reduced power. The amplifier in the example above would only still pump out 2x 250 Watts at 16 Ohms, and is therefore unable to provide the speakers with the power they need to operate at a 100%. The result is a lowered maximum volume.
Are Filters and Crossovers One and the Same?
No, they’re not. They do have some things in common but it’s more complex than you might think.
Using a Crossover Filter with Passive Speakers and Subwoofers
A crossover is a filter that splits a single audio signal into two separate signals. Regular passive speakers with a woofer and a tweeter usually have a crossover built in to ensure the mid and low tones are sent to the woofer and the highs go to the tweeter.
Passive speaker with audio filter:
It’s almost the same with passive subwoofers. A built-in filter separates the lows for the sub to process, while the mids and highs get sent to the passive speakers. You’ll occasionally find daisy-chained subwoofers and speakers, but it’s definitely not the most efficient system seeing as a lot of power is lost due to heat-production and filters. Such a set-up also doesn’t allow for high-low balance adjustments nor will it let you change the default cut-off frequency. The sub will process anything below 120 Hz, the woofer of your full-range speaker takes cares of the 120 – 2,500 Hz range and the tweeter handles everything over 2,500 Hz.
Passive subwoofer with audio filter:
Using an Active Crossover with Passive Speakers and Subwoofers
Let’s see if we can solve this one. Somewhere at the start of this blog, we mentioned an example that includes two amplifiers and a crossover. The 19” crossover we’ve used, however, isn’t just any filter. It’s an active crossover, which means it allows you to adjust the cut-off frequency of the highs and lows. Sometimes this is done via fixed-value switches and sometimes it can be set to any value. Either way, an active crossover determines at which point the low frequencies end and the high frequencies begin. It’s a smooth and steady transition, where the frequencies slowly diminish and ultimately ‘cross over’. The desired cut-off point is usually determined by ear but, to fully optimise a sound system, the frequencies can also be measured.
The Efficiency of an Active Crossover
An active crossover also optimises your system in terms of efficiency. Since the crossover is connected directly to the source signal device, possibly a mixer, it receives nothing but an unamplified signal. The crossover proceeds to split the signal at the default, or any custom cut-off point, resulting in one signal transferring the highs (in stereo) and one signal transferring the lows (in stereo). The highs are passed on to the amplifier connected to your normal speakers, while the lows are sent to the amp connected to your subwoofer. This way, each amplifier only receives the signal it needs to amplify and is able to fully focus fully on its task. An added benefit is the fact that the volume balance between the highs and lows can now be more accurately set.
Crossovers and Active Speakers
Active full-range speakers often come with a built-in crossover filter in one of two forms: pre-amplification or post-amplification. If the filtering takes place before amplification, you’re going to need two amps; one for the highs, the other for the lows. Certain speakers are specifically equipped for this and tend to include ‘bi-amped’ or ‘bi-amplified’ in their names. Much like our previous example, no power gets lost to heat production and each module only receives the signal it’s actually supposed to amplify. A bi-amped speaker can also be recognised by taking a look at its technical specifications, as the stated power capacity of its amp module should include two numbers (e.g. 340+60 Watts).
Active satellite speaker after the audio filter:
If frequencies are filtered after amplification, a ‘regular’ amp is used followed by a passive filter. You’ll often find this design in lower-end speakers.
Active satellite speaker before the audio filter:
Active Crossovers and Subwoofers
Active subs already have an active crossover built in, which basically operates like a passive filter at signal level. Setups like these always allow you to adjust the cut-off frequency. The active crossover in an active sub first splits the signal into high and low frequencies, then sends the lows to the amp module of the sub and the highs to the tweeter.
Active speakers generally don’t come with an active crossover on board, since the manufacturer has already optimised the tweeter-woofer balance during production. Active subs do generally come equipped with an active crossover because it’s impossible for the manufacturer to know which type of active speakers you’re planning on using.
Active subwoofer with variable cut-off frequency (crossover):
Subsonic Filters, High-Pass, Low-Cut
Passive speakers and amplifiers, as well as some active speakers, are fitted with a low-cut filter, usually in the form of a subsonic filter. A low-cut filter ensures all tones below a certain frequency are completely cut off and gives the amplifier a little breathing space, seeing as bass frequencies are the hardest to amplify. Low-cut filters laso aid any speaker that struggles to reproduce bass and it might be good to know that they’re sometimes called ‘high pass’ filters instead.
Lastly, there’s the subsonic filter. A subsonic filter is comparable to a low-cut/high-pass filter but is more extreme, since it elimates all of the low frequencies a regular speaker isn’t able to reproduce. After all, it’d be a literal waste of energy because you’re never going to hear those, anyway. Subsonic filters are often featured in amplifiers and amplifier modules and take out any frequencies below 40 or 50 Hz.
Feel free to leave a comment below if you have any questions!