Your mileage may vary
Yesterday's post on subwoofer placementcertainly got some disagreement from folks. So, let me start off by saying if something you're doing works, then that's great! Secondly, let me suggest that while my manner of speaking and writing is one of absolutes (sorry, others are driven crazy by this as well) there aren't any real absolutes, it's just my way of making a point. Having written all that I would still stand by my convictions that adding a subwoofer is necessary is 99% (see, I didn't write 100%) of cases and in the same number of cases it's best NOT to rolloff the bottom of the main speaker to compensate for the sub. So, let's understand and agree on a few things first. There's no doubt that the less a speaker driver has to do the happier it is and the better the sound. From the driver's perspective a 5-way loudspeaker system is preferable to a 1-way speaker (full range single driver). Why? Because as a mechanical device the less it has to do the better. Imagine for a moment the single driver's challenge if it's to handle the full range of frequencies: moving 60 times a second to make bass and, at the same time, moving 20 thousand times a second to make high frequencies. Something's not right in this situation and it's pretty obvious what. So, we add a tweeter to handle the upper frequencies and a woofer to handle the lowers - to make sure neither trespasses on the other's territory, we add a crossover - a high pass filter on the tweeter and both a high pass and a low pass filter on the woofer. We feed this arrangement with a full range power amplifier. But if that helps, then why not add a midrange driver and make it a 3-way? Many loudspeaker designers do, adding yet another driver and another high pass and low pass filter to make this work. And if that helps, why not add an active subwoofer and make it a 4-way? Some designers do and with good results. If we ignore the challenges of the multiple crossover networks and all the trouble they cause the sound, there's perhaps no question that dividing the full sound into multiple frequency bands handled by different drivers makes for a better performing, lower distortion loudspeaker. And if we confine this discussion to the question at hand of adding a subwoofer, then I would agree that it's better to rolloff the bottom woofer and add a sub. But there are a lot of ifs in those thoughts and one of the main "ifs" is who's doing the design? The speaker designer of the whole system? Great, if he's any good we'll wind up with a nice system. But if it's you, taking a loudspeaker from one manufacturer and adding a subwoofer from another, placing the two physically apart and trying to blend them together by adding yet another crossover to the main speaker - and in the process reducing the performance of the main amplifier - then I would suggest you be very good at what you're doing and make sure you understand all the problems. If, on the other hand, you take my advice and trust the main loudspeaker manufacturer's design chops enough to let that speaker run full range as it was designed to do - keep the main power amplifier signal path as short as possible and pick the best components - and then, and only then, add a subwoofer to extend the range of your main speakers, my guess is you'll wind up with an overall better sounding system than the first possibility. But that's not an absolute and your mileage may vary.
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