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Amplifiers
built in crossovers - why!
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<blockquote data-quote="geolemon" data-source="post: 318227" data-attributes="member: 547749"><p>Not at all, it depends on if you want to go passive, or active, or a combination of both.</p><p></p><p>I'd suggest possibly bridging the 300/4, using the HP filter on the amp to send everything but sub-bass to the comp set... and the passive set will take care of splitting the signal to the tweeter and mid.</p><p></p><p>If you decided to eschew the passive Xover to go all-active, you would send ALL low frequency energy to the mid, which it would choke on, and the end result would be that no matter how much power the set was getting, you couldn't turn it up far enough to realize that power, because the mid would be choking on it's own excursion well before it reached it's real, intended limits...</p><p></p><p>Remember, as frequencies decrease, the required excursion increases exponentially, to produce that frequency at the same output level.. therein lies a fundamental limitation of mids trying to produce bass. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif</p><p></p><p>The "quality" of the crossovers isn't the issue at all..It's more fundamental.</p><p></p><p>A High Pass filter is a simple, stand-alone filter, that attenuates off low frequency energy.</p><p></p><p>A Low Pass filter is likewise a simple stand-alone filter, that attenuates off high frequency energy.</p><p></p><p>By contrast...</p><p></p><p>A "Crossover" is a device that is a combination of a HP filter and a LP filter in such a way that they share a filter point, using curves that (depending on the combination of filter types chosen) will either yield a flat frequency response across that "crossover point", or will yield flat phase response across that crossover point, or some compromise of both, as designed.</p><p></p><p>Amps don't generally have "crossovers" built into them - that's generally a misnomer.</p><p></p><p>Amps have HP and LP filters built into them, typically.</p><p></p><p>Which means the coordination of those two separate sets of controls is an incredibly advanced thing to try to pull off...</p><p></p><p>Trying to manually coordinate a separate set of HP filters with another LP filter to actually establish a "crossover point", where the amplitude and phase response across the crossover point is actually flat would be a very difficult thing to do, indeed.</p><p></p><p>And that's one critical point to consider...</p><p></p><p>The very presence of - and delicate treatment of - a crossover point really IS the reason that you hear people make the argument that "ideally", you'd only use one speaker that could cover the whole frequency spectrum.</p><p></p><p>Another consideration is the additional amp channels required, to power a set actively, when there are no compromises on the amp, feeding a component set via a passive Xover. It simply only "sees" one driver or the other, at any given frequency... a 2 channel amp driving two speakers per channel via a passive crossover won't sweat or be compromised any more than a 4 channel amp driving those same 4 speakers on individual channels. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif</p><p></p><p>There are some true active <em>crossovers</em> on the market (allowing you to mitigate the risk of messing up phase or frequency response across the crossover point), but they are not inexpensive, and would still beg the question of what the goals for that return-on-investment actually were...</p><p></p><p>Good suggestion, you'll get more power to the set, and/or the ability to set the gains very conservatively low and still get full power to the comp set, with additional headroom actually gained rather than lost (as is typically the understanding when bridging an amp, loss of headroom, cleanliness, etc), AND the maintenance of the factory specified crossover relationship... maintaining proper response and impedance performance across the crossover point.</p><p></p><p>Some - if not all - of these things are often compromised in the decision to go all-active...</p><p></p><p>The concept of power is always one myth that's interesting to see tossed around...</p><p></p><p>If you use the passive set with the crossover, a little power will be burned up as heat in the crossover... but it shouldn't be as high as 25%!</p><p></p><p>Even if it was... compare running 'all active" to "all passive" in this scenario.</p><p></p><p>You have a 25x4 amp, with built in HP and LP filters on each channel.</p><p></p><p><strong>all active:</strong></p><p></p><p>the tweeter gets 25 watts, HP filter set "around" 4K, for example...</p><p></p><p>the mid gets 25 watts, LP filter set "around" 4K, trying to match them.</p><p></p><p><strong>all passive:</strong></p><p></p><p>You bridge the amp to 100x2, and use the passive crossover supplied.</p><p></p><p>Now, in addition to the crossover "points" (there's a reason they are called that //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif) being maintained...</p><p></p><p>the tweeter gets 75 watts (100w - 25%), HP filter is as intended by the engineers...</p><p></p><p>the mid likewise gets 75 watts, LP filter is as intended by the engineers.</p><p></p><p>Maybe if you actually purchased an external true active "crossover" (really fundamentally different in concept than active HP and LP filters), you could mitigate the phasing and response issues...</p><p></p><p>And if you purchased a <em>larger</em> 4 channel amp, 75x4, you could mitigate the power issues...</p><p></p><p>But by that point, you've literally spent orders of magnitude <em>more money</em>, just so you can end up at the same place that the person with the bone-stock passive setup is.</p><p></p><p>Hmm...</p></blockquote><p></p>
[QUOTE="geolemon, post: 318227, member: 547749"] Not at all, it depends on if you want to go passive, or active, or a combination of both. I'd suggest possibly bridging the 300/4, using the HP filter on the amp to send everything but sub-bass to the comp set... and the passive set will take care of splitting the signal to the tweeter and mid. If you decided to eschew the passive Xover to go all-active, you would send ALL low frequency energy to the mid, which it would choke on, and the end result would be that no matter how much power the set was getting, you couldn't turn it up far enough to realize that power, because the mid would be choking on it's own excursion well before it reached it's real, intended limits... Remember, as frequencies decrease, the required excursion increases exponentially, to produce that frequency at the same output level.. therein lies a fundamental limitation of mids trying to produce bass. [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG] The "quality" of the crossovers isn't the issue at all..It's more fundamental. A High Pass filter is a simple, stand-alone filter, that attenuates off low frequency energy. A Low Pass filter is likewise a simple stand-alone filter, that attenuates off high frequency energy. By contrast... A "Crossover" is a device that is a combination of a HP filter and a LP filter in such a way that they share a filter point, using curves that (depending on the combination of filter types chosen) will either yield a flat frequency response across that "crossover point", or will yield flat phase response across that crossover point, or some compromise of both, as designed. Amps don't generally have "crossovers" built into them - that's generally a misnomer. Amps have HP and LP filters built into them, typically. Which means the coordination of those two separate sets of controls is an incredibly advanced thing to try to pull off... Trying to manually coordinate a separate set of HP filters with another LP filter to actually establish a "crossover point", where the amplitude and phase response across the crossover point is actually flat would be a very difficult thing to do, indeed. And that's one critical point to consider... The very presence of - and delicate treatment of - a crossover point really IS the reason that you hear people make the argument that "ideally", you'd only use one speaker that could cover the whole frequency spectrum. Another consideration is the additional amp channels required, to power a set actively, when there are no compromises on the amp, feeding a component set via a passive Xover. It simply only "sees" one driver or the other, at any given frequency... a 2 channel amp driving two speakers per channel via a passive crossover won't sweat or be compromised any more than a 4 channel amp driving those same 4 speakers on individual channels. [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG] There are some true active [I]crossovers[/I] on the market (allowing you to mitigate the risk of messing up phase or frequency response across the crossover point), but they are not inexpensive, and would still beg the question of what the goals for that return-on-investment actually were... Good suggestion, you'll get more power to the set, and/or the ability to set the gains very conservatively low and still get full power to the comp set, with additional headroom actually gained rather than lost (as is typically the understanding when bridging an amp, loss of headroom, cleanliness, etc), AND the maintenance of the factory specified crossover relationship... maintaining proper response and impedance performance across the crossover point. Some - if not all - of these things are often compromised in the decision to go all-active... The concept of power is always one myth that's interesting to see tossed around... If you use the passive set with the crossover, a little power will be burned up as heat in the crossover... but it shouldn't be as high as 25%! Even if it was... compare running 'all active" to "all passive" in this scenario. You have a 25x4 amp, with built in HP and LP filters on each channel. [B]all active:[/B] the tweeter gets 25 watts, HP filter set "around" 4K, for example... the mid gets 25 watts, LP filter set "around" 4K, trying to match them. [B]all passive:[/B] You bridge the amp to 100x2, and use the passive crossover supplied. Now, in addition to the crossover "points" (there's a reason they are called that [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG]) being maintained... the tweeter gets 75 watts (100w - 25%), HP filter is as intended by the engineers... the mid likewise gets 75 watts, LP filter is as intended by the engineers. Maybe if you actually purchased an external true active "crossover" (really fundamentally different in concept than active HP and LP filters), you could mitigate the phasing and response issues... And if you purchased a [I]larger[/I] 4 channel amp, 75x4, you could mitigate the power issues... But by that point, you've literally spent orders of magnitude [I]more money[/I], just so you can end up at the same place that the person with the bone-stock passive setup is. Hmm... [/QUOTE]
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