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In Reply to: I've got both.... posted by doodlebug on July 25, 2006 at 17:59:29:
In theory Active speakers are better because each drive unit has its own amplifier and is therefore driven over a limited bandwidthwith consequently reducing Intermodulation distortion. You've also removed the resistive losses of a passive crossover components and gained better control of the drive units which means even less distortion.Active crossovers operate into a resistive load and therefore conform to classic theory which means seamless integration, better clarity and accurate phase behaviour so a better stereo image.
In practice is it possible to mimic the action of an Active crossover and get very close with a passive design but it rarely happens because most speaker designers aren't electronic engineers and don't understand the implications of what they are doing. Many still use resonances in crossovers to correct drive unit anomolies and so on. Therefore it may well be possible to convert passive speakers to active and gain a massive improvement. Equally there are some pretty rotten actives around.
An enormous benefit can be had by going active if drive units with a very broad bandwidth are selected (to get really good phase behaviour) with a gentle roll off and steeper filters are chosen than is practical with passive designs. Much of the harsness that two way speakers have is caused by the tweeter being audible below the crossover and intermodding like hell. Using 4th order filters reduces this dramatically.
Definition is improved by removal of the passive components too, bass tightens and mid is much clearer.
Another advantage is that high voltage, low current and ultra low distortion, dedicated power amps can be designed that are far better and cheaper than the great monsters beloved of Hi Fi Journalists. These are necessary because speaker designers can't do a proper crossover and impedances are often far too low. 2-3 ohms is common where an 8 Ohm drive unit has a DCR of 5.4 ohms and is much kinder to its Amp.
Therefore Active speakers have the potential to be substantially better than passives and they must be the future. The problem at the moment is that there are good and lousy examples of both and it makes it difficult to tell.
Follow Ups:
The typical low end active speaker is no more than a speaker with amps and a crossover in the same box. For the most part the only advantage it has is an active crossover that may be better optimized for it than an outboard or passive, and here well integrated high quality separates for the most part will work just as well, if not better. Where things are markedly different is in the upper end, where an on-board DSP perfectly optimized to the speaker offers both frequency response and phase response characteristics that simply cannot be duplicated with separates. This level of technology is rapidly moving down the price point spectrum, and within the foreseeable future will dominate the market.
Bill you need to have speakers that work, you simply can't compensate for drive unit deficiences with a DSP any more than you can with an analogue electronic crossover. To talk about high end or low end is misleading, correct engineering is what counts.For instance, a typical High End 3" dome rolls out at 12dB at best and typically 24dB per Octave below 500Hz, resonance is usally around 400 Hz and this is before a crossover is applied. Please explain how a DSP can resolve this problem and produce seamless phase and amplitude integration of the bass drive (or the tweeter for that matter because they are just as bad at the top)with adjoining drive units.
We've found that drive unit anomolies cannot be corrected and that crossovers must conform to classic theory, hence my stating in my previous posting that only broad bandwidth ones will work properly.
While integrating DSPs into the design process hasn't yet become popular in the hi-fi end of the spectrum it's de riguer in pro-sound, where it's been a staple commodity since EAW introduced the KF850. True, a DSP can't correct basic design flaws. But for better or worse speakers that rely on analog hardware rather than digital software will eventually suffer the same fate as analog media.
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