posted
I think we've covered this a few times before, but for anyone new to the forum or as forgetful as me (I still don't know how I got through some of those classes in college and grad school ).
But, benefits to running either or both active & passive X-overs. And, part 2, if running active X-overs, is the internal x-over in the amp enough or should you go with an external and the amp's as well? I guess one could look at it this way, can you have too many X-overs?
I know that a lot of you have stated that you either run or recommend running passives along with the active x-over (internal or external) to better protect the mids, mid-bass, and tweeters. And, that many feel that these passive x-overs (in-line, sorry) would help eleviate (spelling?) much of the eletrical and line noise that may originate between the RCA inputs and the speaker itself.
By using an external x-over (say that 10 times fast ) and an internal active x-over, does the external make the first rough cut of signals and the amp(s)'s internal makes the final sergical cut?
posted
Hey Ber! Good to see you back! I too was gone for about a week... no one seemed to have noticed!
I like to use both, but differently than you (of course!). I say if the internal is of high enough slope (above 18dB) it should be fine. Then, in line, I like to use a cap on tweets set at half the active x-over for DC protection. On amps that are running comp sets, use the passive networks that come with and the amps internal so you get a pass band for the mid, and virtually eliminate the possibility of the tweet frying from low hz....
Course, I do 'bout everything differently!
------------------ Ron Hawkins
Sometimes the majority only means that all the fools are on the same side.
Use your ears to judge components, NOT your wallet! K.I.S.S.
Yes- I prefer active crossovers myself, and I don't believe a quality passive will provide any noise filtration, as it is designed to pass the signal as pure as possible, correct? If it filters noise, that ain't cool a'tall :-)
As AudioPhyle said, protecting a speaker from power supply leakage is important, as an amp doesn't neccesarily have to blow to have such leakage, and will eat speakers very VERY fast.
With a tweet, simply running a cap and a small light bulb rated at ~3/4 the speakers' power should provide all the protection it'll need, except nothing can save it from the dreaded "clip-monster"
Its all about the actives, baybee!
Two actives, such as the one in an amp plus an external, should only be used if one desires a higher slope or one needs to do so to bandpass filter a speaker.. I honestly don't see any other advantage.
As for rough cut/ surgical cut, they both affect the signal the same, say the external cuts off 400 and below at 18db/o, then the signal the amp recieves will be thus attenuated. Then, if the amp does the same thing, 400 at 18db/o, then that will cut it off even more.
Bear in mind, the filter doesn't start EXACTLY where the point it.. It starts slope-ing off 1/8 of an octave or so, maybe more (not sure) before the filter. So, if you were using 3 to 4 filters in a row, you might end up filtering off half an octave that you didn't expect to!
(I think... few more tests )
ShadowStar
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HEY! I'm looking for a CHEAP used Clarion Thunderdome.. Hook me up!
Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
Kewl. Thanks for the input guys. I figured with the last couple posts I saw on Monday in regards to cross-overs I'd try to get a blanket question out there.
I love the lightbulb idea on tweets. Saw that on a set of Community stage speakers about 5 years ago for the first time. Nothing like seeing a bunch of "red-eyes" staring at you from the stage in the middle of an Act.
posted
Another thing to worry about when using more than one crossover in series is the passband ripple. Say you have 1 dB ripple from the first crossover, then have you have 1 dB ripple from the second. They could cancel out somewhat, or they could cause you to have 2dB ripple in the passband. It depends on the crossover type and component tolerances, but I think it would be much better to just use one active crossover at a time.
posted
The crossover frequency is typically the 3db down point of the filter. ie. If the filter is a 80hz lowpass, the signal is actually 3db down at that point. This is done so that you can have a highpass and lowpass at the same freq with little summation and it also alows a degree of common ground when dealing with different topologies of filters...
------------------ Blow your mind - PORT your box!
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