I share the opinion of Vajk Bizsók about the importance of exhaustive technical design and implementation, "According to our experience and measurements, the key to good sound quality is the excellent technical design and implementation. The hi-fi equipment are fully technical devices. Their operation is defined by known physical and technical laws, therefore the equipment made using scientific elaborateness, accurate measurements and implementation are the ones that perform outstandingly in subjective terms as well."
As a precursory remark, we'd better be aware that the assessment of loudspeakers by means of listening to music through them is limited by the following factors:
- the brain gets accustomed to the acoustic character in a short time (it "corrects" the imperfections of sonics, though the experienced can distinguish the bigger issues at once)
- we were not present when the recording was made, so we don't know what should sound and how
- our auditive memory is very weak
- we don't know to what extent the recording was modified by the sound engineer (echo, treble and bass boost/cut)
- we can't sit at the same place (room acoustics depend on listening position)
- we can't always be in the same mood
- we are tied to the appearance of the technology, we have prejudices
In spite of all that, it's fit to follow certain pieces of advice when choosing a loudspeaker.
What to look out for when buying a loudspeaker?
Everybody would like to choose a loudspeaker that they can listen to with satisfaction on the long run. What should be heeded when you visit a vendor's showroom to listen to and to buy a loudspeaker?
Many people expect - rightfully - that a more expensive loudspeaker should yield better sound quality than a cheaper one. It is true that cheaper loudspeakers usually have much room for improvement. But unfortunately, there are expensive loudspeakers that can't boast of the quality expected from their price tag. The chief loudspeaker designer of Harman/ Kardon measured and listened to several loudspeakers that were around and above the 1,000 USD price-range, yet produced atrocious sound quality. So better be careful! On the other hand, it's possible to find decently designed and built loudspeakers below 700 USD/ pair.
Since the listening room has walls as boundaries, sound don't just depend on the loudspeaker, but also depend on room size, loudspeaker to wall distance, listener position and the sound absorbing materials in the room. Moreover, in the usual listening positions the sound components reflected from walls "outvoice" the direct sound from the loudspeaker, that is what we hear is more the room acoustics than the loudspeaker itself.
Therefore it is adviced to listen to the loudspeakers in two positions. (1) Place the loudspeaker far from walls and sit close to them (50...60 cm), use bass boost if need be. (2) Place the loudspeaker as close to the walls in the showroom as it would be in your home, and sit at a distance you would do at home.
The frequency response of an excellent loudspeaker is flat in an anechoic chamber, where there are no reflecting surfaces. When loudspeakers are placed close to walls, their frequency response gets uneven, because secondary sound waves reflected from walls interfere with the direct sound from the speakers. In listening and setup position (1), we try to approximate the ideal, anechoic frequency response. This necessitates our ears be close to "on-axis," that is near the line of the midperpendicular of the section connecting the centers of the tweeter and midrange speaker. In an average room with 60 m3 air volume and 0.5 s reverberation time, the reverberation radius, that is the distance where the reflected sound components get louder than the direct sound from the acoustic source, is about 60 cm, therefore it's necessary to sit closer to the loudspeaker than this, if we are to hear the sound of the loudspeaker rather than the "sound" of the room. Many loudspeakers have a frequency response in which the so called baffle step (or in other words: diffraction loss) is only partially compensated. This calls for a bass boost when such loudspeakers are in far from walls position. This is not necessarily a shortcoming of the loudspeaker, one simply needs an amplifier or preamplifier with tone control.
In listening and setup position (2), we try to approximate the way the loudspeakers will sound in your home, when you listened to them from the required position. This is only possible with some limitations. In reality, the farther from the reverberation radius we listen to the loudspeaker, the more we hear the acoustics of the room rather than the own sound of the speaker, especially in the bass and low mids range. Unfortunately the sizes of the vendor's showroom are unlikely to match the sizes of your living room, we can't change that. If your room is smaller than the listening room, then due to the greater room gain, the loudspeaker will sound more deep-toned in your room. Let's be prepared: if your living room contains more sound absorbing material (carpets, drapes, appointments) than the vendor's showroom, then high-pitched sound reproduction will be weaker in your home.
To assess the quality of a loudspeaker objectively, it's necessary to use the listening and setup position (1), strange it may seem. This eliminates the influence of both the room size and the sound absorbing materials to the sound. When listening from such a close distance with your ear not on-axis, the sound waves propagating from the tweeter and midrange speaker don't sum up in phase, but partially cancel each other. This problem is not manifested in dual-concentric speakers, but these speakers have weaknesses of their own, such as a more uneven high frequency reproduction with poorer directional characteristics of the tweeter. Placing the loudspeaker far from the walls necessitates bass boost on the preamplifier for many loudspeakers. Placing a quality loudspeaker close to walls and/or listening to it from afar will degrade its sound quality significantly, especially the clarity of the bass and midrange will suffer. The more walls are close to the loudspeaker the more the bass will sound louder. At the same time, a loudspeaker placed close to the walls will excite the standing waves (so called room modes) of the room, therefore it's advisable to avoid placing the loudspeaker in the corner (meeting of 3 walls). 3 walls may lift the bass to unnatural levels.
This is especially true for the amplifier, since the loudspeaker is directly connected to it. Although the usual measured data of amplifiers, like the flatness of the frequency response, are much better than that of loudspeakers, yet according to my experience, there are audible differences between certain low quality amplifiers. This might be my subjective judgement, because I didn't verify what I heard with a blind test. Anyway, it's better to be cautious, the quality of the chain driving the loudspeaker may be important, so I recommend the use of quality components, especially amplifier for the listening test.
Many refrain from boosting or cutting the bass and treble. Many don't even use amplifiers or preamplifiers with tone control. Since bass reproduction is enormously dependent on loudspeaker and listening position, I conclude that tone control is just necessary in many cases. For those who choose not to use tone control, their loudspeakers will be balanced at a single distance from the walls only, and will not sound well at other places. Furthermore, the lower the volume is set, the more insensitive our hearing becomes to low frequencies, therefore at low volume settings, it becomes imperative to step up the bass for a more natural sound.
The sensitivity of the loudspeakers (the sound pressure produced at the same amplifier voltage) may be significantly different. Our hearing may fool us, because we usually assess a louder loudspeaker as being better independently of its quality. If you listen to various loudspeakers one after another and you want to compare them, readjust the volume on the amplifier preferably by using an SPL meter, so that you will hear all tested loudspeakers equally loud.
Very low tones can only be radiated with large boxes with a high enough efficiency. Therefore small sized loudspeakers call for active subwoofers set to the appropriate cutoff frequency. The cutoff frequency should be set to the point where the main speakers start to cut the bass. At home you will have time to experiment the optimal placement of the subwoofer relative to the main loudspeakers and walls, at the vendor's facility there is no point in doing this.
Don't let the vendor make you listen to their recordings. They will choose recordings which sound good on the loudspeaker they want to sell us. Don't let them have this opportunity, bring your own sound files and/or CD's, your own favourite music and listen to various recordings.