When choosing a hi-fi system, it’s important to consider the specifications of the components you’re going to use not only to achieve optimal sound quality, but also to ensure the components will work well together. It should be noted, however, that choosing components based purely on their specifications is unwise – and that ultimately the sound of a given component should be the deciding factor in making a purchase. Many hi-fi components appear similar on paper – yet in practice can sound radically different.
Previously in the Hi-Fi 101 series, we’ve covered the components that come together to form a hi-fi system – including the amplifier, source components, speakers and cables. We’ve also covered a selection of key terms which you will frequently encounter on your hi-fi journey. Let’s take a look at the specifications you’re likely to encounter when choosing your hi-fi components, what they mean, and what to look out for.
Crosstalk is the measure of the amount of undesirable signal mixed between the left and right output. To maintain a good stereo image with a decent sound stage, it is necessary to have as little crosstalk between channels as possible. Crosstalk is measured in DB, where larger negative numbers are better.
Damping is the ability of an amplifier to control the motion of a loudspeaker. When a signal is applied to a loudspeaker, it causes the speaker diaphragm to move back and forth. Due to the diaphragm’s inertia, the speaker will continue to vibrate after the signal stops – producing sound waves that are not part of the original signal.
Damping factor is calculated by dividing the output impedance of an amplifier by the load impedance (or the impedance of the speaker). When a speaker cone moves, it acts like a microphone; and a signal is generated by its voice coil, known as back EMF (Electro Motive Force). This signal travels back through the speaker cable into the amplifier’s output circuitry; and because it is in opposite polarity with the motion of the speaker, the ringing (or excessive vibrating) or the speaker is impeded or ‘damped’. Essentially, the amplifier is working against the speaker as well as driving it; when the cone moves out, the back EMF pulls it back in, etc. A higher damping factor results in tighter, more controlled bass.
Power Output (W)
Power Output, measured in Watts, is the amount of electrical power an amplifier can provide. Usually the specifications of an amplifier quote a selection of different power output figures into varying impedances, indicating the amplifier’s ability to drive difficult loads. A common presumption is that you speakers must have a higher power handling figure (again measured in watts) than your amplifier’s output – but this is often not the case. At normal listening levels, playing a given piece of music, it is highly unlikely that you’re going to be utilising all of your amplifiers power.
In fact, depending on the sensitivity of your chosen speakers, very little power is actually required to reach a comfortable listening level – much of your amplifier’s power exists to allow it to handle dynamic swings int the music, and to prevent clipping should your speakers momentarily demand more current than your amplifier is providing. Usually, it’s now sheer power that causes damaged to speakers – it’s an overdriven, clipping amplifier. A high powered amplifier driving low powered speakers without entering clipping will produce far better sonic results and cause less component damage than an underpowered amplifier driving powerful speakers. To this end, power handling is one of the least important factors when choosing a pair of speakers.
Signal to Noise Ratio (SNR)
Signal to noise ratio is the level of a desired signal (I.E your music) compared to the amount of noise generated by a given component (for example background hiss or hum). It’s usually measured in DB (Decibels), and higher numbers are better. No electronic component is completely silent – indeed few rooms are completely silent. The SNR is simply a measure of how much of a components background noise is audible when compared to the level of your music – though, in truth, the SNR of any well-designed hi-fi component will be more than acceptable in most listening environments.
Speaker sensitivity is a measure of a speaker’s ability to effectively convert power into sound. Essentially, it is nothing more than measure of the amount of power required for a speaker to reach a certain volume when measured from a given distance. A high-sensitivity speaker will require less power to reach a given amount of volume than a speaker of low sensitivity. Traditionally, sensitivity (quoted in decibels) is calculated by measuring the level of sound produced by a speaker fed with 1 Watt of power from a distance of 1M. There is an excellent article written by PSB Speakers explaining speaker sensitivity in-depth which you can view Here.
THD +N (Total Harmonic Distortion plus Noise)
THD is a measure of the affect a given component will have on the sound. A high rTHD figure (quoted as a percentage) will result in more colouration, therefore lower numbers are better. As with SNR, the THD of a well-designed modern hi-fi component will be kept to a minimum. Components with low THD figures will often sound cleaner and crisper and offer a more accurate reproduction of the music.
Total Correlated Jitter (TCJ)
Jitter, a problem inherent in digital to analogue conversion (or the playback of digital audio) is the gaps caused by processing problems or the internal clock of the Digital to Analogue Converter (DAC). It’s measure din picoseconds, and despite being so small as to be unheard by the human ear, Jitter can result in decreased musicality and loss of audio detail.
Wow/Flutter (sometimes referred too as speed variance or pitch stability) is a measure typically quoted in the specifications of analogue playback equipment such as turntables or tape decks. It denotes the variations in pitch caused by irregular motion in the working mechanical components of a piece of equipment. The lower the W/F figure, the more accurate the speed stability is likely to be.
Electrical specifications aside, it’s also important to ensure that the components you choose are fit for purpose. And not just for the purpose of playing music – but also suitably equipped to work within your system. This may include offering the correct inputs and outputs, offering a remote control function, offering tone controls, or maybe even offering the ability to interface with a multi-room audio system.
Many high-end audiophile components are sparse where features are concerned, choosing to spend the materials budget on the components responsible for the sonics as opposed to the feature count. Some high-end integrated amplifiers, for example, provide only a few inputs – in fact, some only have a single input, requiring you either stick to a single source component or switch cables manually. If you don’t want the hassle of switching cables, and your system comprises multiple source components, you need to choose an amplifier (or preamplifier) with enough inputs to handle all of your components.
The type of inputs is also of crucial importance. There’s little point in purchasing an amplifier with 2 single-ended inputs and 2 balanced inputs, and attempting to connect 4 source components which only offer single-ended (unbalanced) outputs.
And don’t forget the outputs. Many amplifiers at the higher end of the market lack a built-in headphone amplifier, so if you wish to use headphones with your system you’ll require an external headphone amplifier – and that, in turn, will require that your amplifier be equips with a line-level output, or a preamp output at the very least.
The same goes for recording devices – if you wish to connect up a recording device, for example cassette deck, you’re going to need a line level output on your amplifier or preamplifier. Similarly, if you wish to have both a recording device and a headphone amplifier, your amplifier must be equipped with 2 line level outputs, or you’ll need a headphone amplifier with a passthrough output to send the signal on to your recording device. Alternatively you can use splitter cables and adapters, however depending on the design and quality these can lead to signal degradation. It’s important to note also that while it’s safe to use such adapters for output purposes, they should never be used to connect multiple components to a single input – as doing so can damage the circuitry of both your source components and your amplifier.
In part 6, we’ve introduced and deduced the important specifications you must consider when selecting your hi-fi components. You now have all the knowledge you need to begin assembling the perfect system. If you’d like to refresh your memory on any of the topics we’ve covered, you can view a list of the posts in the Hi-Fi for Beginners series Here