Louspeakers - Part TWO

Important Loudspeaker Specifications NOT to ignore.  – Mervyn Augustine 

In Part ONE of our Bite-Sized Article, we stated that the loudspeaker is the most important component in your audio system.

In this article we briefly explain some terms, jargons used and specifications that should not be ignored when evaluating a loudspeaker :

1. Frequency Response : The response of the drivers and the speaker, from the lowest sound it will play, up till the highest point, in relative terms. Typically, this tells you the range of sounds it will play. An effective range would be +/-3dB. If it is not stated, it is typically understood that it is -10dB. Better speaker manufacturers will indicate at least +/-3dB, and even better, +/-2dB, with the smaller the variant, the more technically accurate the speaker is. More will be explained in a dedicated post.
   
   A full-range speaker will do 20Hz deep, and 20kHz and above high. This covers the full hearing range, that covers virtually all playback devices available.
2. Sensitivity : The higher the sensitivity, the less power your amplifier needs to produce to achieve the intended loudness. You will see specifications such as 1Watt of power/1Meter (M) which means 1 Watt at 1M distance, or 2.83V at 1M distance. At the same distance, every 3dB difference is doubling of power. For example, the ideal headroom for a speaker to play is 120dB (rock-concert levels) for dynamics, at fixed distance of 1M (for the sake of simplicity). A speaker of 84dB sensitivity @1M will require 4,096 Watts while a speaker of 93dB will require 512Watts to achieve that loudness. That’s 1/4 the power needed!The lower the demand of the amplifier, the lower the distortion, and the less tonal “flavour” the power amplifier introduces to the sound.
3. Power Handling : In conjunction with sensitivity, every speaker has a limit of power it can handle. Citing a 84dB speaker, it is most unlikely it will handle any more than 1,000 Watts of power, which will suggest the 84dB speaker will never play the 120dB before giving way, versus a 93dB sensitivity speaker.
4. Nominal Impedance : The average resistance of the loudspeaker will suggest the need for amplifier power. The common loudspeaker nominal impedances are 4, 6, and 8 Ohms these days. The lower the number, the more power it demands from the amplifier. 8 Ohms nominal would be the easiest load on amplifiers (out of the common loads). But there’s more than meets the eye – it is common that the lower the frequency response point of the speaker, the lower the impedance it is, while only showing an 8 Ohms average, a consumer would hardly know this, and may over-drive a smaller powered amplifier attached to a larger loudspeaker.
5. X-Over Points : Crossover points are frequency points where one driver function hands-over to the other driver function. For example, 3-way loudspeaker with a bass-woofer function speaker will crossover at 220Hz to the mid-range of the speaker, then, 2kHz to the top. The X-Over can be a gradual design, or a steep cut-off design, suggesting that the fundamental tones of instruments may be played primarily from the woofer, while the mid-range drivers may be engaged with vocals and string instruments. In a steep design, you may hear a bassoon come from the woofer’s height, while the alto saxophone’s positioning coming from where the mid-range drivers are placed. X-Over points help to indicate how good the driver’s capabilities are, and how well the loudspeaker will image and place a sound stage. Ideally, the staging height should be relatively compact, while presenting a large scale, instead of a piece meal where bass localizes from the floor, and the highs localizing towards the ceiling, especially with poorer room acoustics.

These 5 points require a deeper look into, to further appreciate loudspeaker designs, but will provide a general understanding comparing a loudspeaker from the other. There’s so much physics involved in a loudspeaker design, there’s always a combination of variables that makes a speaker sound great.

What is the ideal speaker, and if there is, by whose definition, by what standards?

Certainly is food for thought, and something all enthusiasts should think about. Perhaps on Loudspeaker Part THREE?