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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: 3-way floorstander for smaller rooms? posted by olpot on July 23, 2002 at 07:27:37:
I agree that there are some definite advantages to choosing a larger design, like an octave (or two) more bass extension, increased sensitivity and increased power handling. I think the laws of physics are more difficult to circumvent than was once assumed. Big systems do give a sense of ease and flow and "power under control," that small systems often struggle to match. I think I know why.The importance of sensitivity should not be overlooked. A sensitive system requires less power to create a given SPL than a non-sensitive system. Large speakers are almost always more sensitive than small ones. Don't become obsessed with sensitivity though. 90 dB/W/1m is sensitive. To achieve even more sensitivity requires giving up bass extension in all but the most gigantic speakers. Furthermore, don't overlook the importance of power-handling. All speaker drivers are not created equal. Those that can handle more power can work harder (and go louder). Small speakers utilize drivers that are matched to their enclosure size. Speaker designers (with 1 or 2 rare exceptions) use smaller drivers (with less powerful magnet structures) for their bookshelf 2-ways. As a function of the physics of bass reproduction, big size also imparts deeper bass extension, so a physically large system can play lower and louder with less distortion than a small speaker system.
The sense of ease and "power under control" that a 3-way system can create does not come about accidentally. The drivers don't have to work as hard individually in such systems. They are not worked past the point of pistonic motion, which is crucial. Furthermore, the crossover points between the drivers can be arranged so that the drivers always produce wide-dispersion. This is the key to producing an even room power response. Small systems, in contrast, produce an uneven power response. A small system will often have to be toed in to achieve a high sound pressure level (sound power will drop off steeply as you move away from the speaker's reference axis - the speaker beams), but the wide dispersion of a 3-way system insures that this sound pressure level can be heard from multiple angles (toe-in is not necessary).
The disadvantages of large systems must be played against the strengths. Passive crossovers produce distortion. They interfere with the sound coherence of the system. Going to a 3-way design requires inserting yet another crossover into the audioband, but using an extra crossover this way can be an advantage if the designer considers the non-linearity of human hearing. Our hearing is most sensitive at 4 kHz and hearing acuity tapers off the farther you go (frequency-wise) away from this point. So, where you place the crossover is just as important as using it in the first place. A 3-way system does allow more flexibility to avoid placing the crossover between 2-4 kHz. Yet, more often than not, this is still unavoidable.
Furthermore, a large structure is inherently less rigid than a small one and large speaker systems have more of a tendency to resonate than small ones. Resonating boxes obscure and interfere with the output of the drivers. For this reason, large systems require much more elaborate (and expensive) bracing than small ones to prevent excessive box colorations. Moving to a large speaker greatly increases the expense of the speaker (when you factor in the additional cost of the larger box, the extra bracing, the extra crossover components and the extra-driver).
Moreover, large systems can easily overload small rooms. To get away with a large system in a small room you'll need to choose a system with a very dry (over-damped) bass alignment (ruler flat or very gently declining bass response - electrically these designs do not show wild impedance swings or tough phase angles in the bass). Such systems sound tight and fast as opposed to loose and boomy.
A large system then is not inherently stronger than a smaller one, when the advantages and disadvantages (of going large) are weighed. The greatly increased material(s) cost of a large system often prompts manufacturers to skimp on parts quality (sadly). Quality large 3-way systems are significantly more expensive than their 2-way bookshelf counterparts, so two models of the same price of each type are not necessarily equal. It's difficult to compare apples with oranges in this scenario.
From a consumer perspective, choosing a quality 3-way system is more complicated than choosing a quality small system and requires much more listening time and effort (in addition to more money). Don't be fooled by the size of the box or the number of drive units. Bigger is not inherently better. I would examine each individual driver in the 3-way system. Are they the best? or 2nd or 3rd rate? Compare the drivers to those available in OEM catalogs. Look at power handling. Driver weight indicates a larger magnet structure. In fact, overall system density (not just weight) is a good clue that quality parts are used. Examine the box carefully using music and your knuckles. Bigger boxes tend to have more problems with resonances. It's difficult to see inside the box (unless you remove the drivers), but the knuckle wrap does give a good clue as to how well the box is damped. For a large system, you want very thick MDF (around an inch). Finally, it's so important to LISTEN to the system. Spend a lot of time listening to many different types of music from different angles (not just the sweet-spot). This is the only way to test the quality of the speakers crossovers and assess the system's coherence. A quality system will sound good from many different listening angles (crucially the tonal balance in such a system will not change dramatically as you walk about the room or change position). Don't overlook the additional expense of the extra amp power that larger systems often require. Good luck.
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Follow Ups
- Advantages vs. Disadvantages - layman 11:53:05 07/23/02 (1)
- Check these out - layman 12:45:54 07/23/02 (0)
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