Passive vs. active crossover

They're all passive except for a few customs over $2k.

Quote:

Originally Posted by belushka 

how does it work?

A passive crossover is what is generally used in BA phones or standard home speakers. An active crossover is an external component piece. Google Rane active crossover.

In short

passive crossovers  use resistors, capcitors, choke coils to create the frequency and attenuation level of the crossover be it high pass (from X number UP) or low pass (from X number below) at a slopew of -6 dB, -12dB, -18dB and -24dB per octave.

Active crossovers do all this in the digital realm. Instead of changing values for capacitors and choke coils, depending on crossover,  you press a button up or down to change crossover frequency and slope (changing values in the DSP code). The Rane Digital crossover has a fixed 24 dB slope but can adjust crossover frequency along with subsonic (below 20hz) and Ultrasonic (above 20Khz) filters. The active cross over has to do an A/D conversion than a D/A conversion unless fed a digital signal.

Active can used passive componenets in front of the amp stages as well. Active simply means that the amp is not driving a crossover and is directly connected to a driver. This alows a wider range of options for parts that aren't required to handle current and allowing direct control of an easier load (driver) by the amplifier.

Quote:

Originally Posted by goodvibes 

Active can used passive componenets in front of the amp stages as well. Active simply means that the amp is not driving a crossover and is directly connected to a driver. This alows a wider range of options for parts that aren't required to handle current and allowing direct control of an easier load (driver) by the amplifier.

An ACTIVE crossover (the operative word is Crossover) HAS NO (meaning, none, zero, zilch, nada, zip, donut) PASSIVE COMPONENTS. Regardless of what JH Audio says as that is what you are eluding to.

In short, JH-3a is a PASSIVE system with 3 independant amplifiers per crossover (lows, mids and highs). No different than any other system out there that has a crossover for low, mids and highs. that does not constitute an active setup.

I love Internet experts. You are absolutely wrong and my comment had nothing to do with JHA. For instance. http://www.head-fi.org/t/613417/unique-melody-platform-pure-6-6-driver-custom-iem-dac-active-crossover-and-amp  Active crossovers have been around forever, as in before DSP. You still split frequencies with passive components in the gain stage in front of the amplifier. Any splitting of frequencies before the amp stage constitutes active. Because active crossovers often have gain stages to adjust level, the analog ones use typical RC passive networks as the filter portions within or between stages. As long as the network is impervious to load in or out and the amp output is directly connected to the driver terminals, it's active. Don't know exactly what JHA is doing but I think I read that it's a bit of both including bits AFTER the amp so I didn't reference them for a reason. (It's a different discussion but are the semantics of what JHA doing that big a deal is it gets the desired result?) I was just pointing out that it would be prohibitively expensive for most.

Figgie you are being misleading as well, no, all active crossovers are not digital. Many these days are, but not all of them.

And GoodVibes, in order for it to be an active crossover, it has to use active components, typicaly opamps. I dont think there are any examples of someone putting a passive crossover before the amplifier, it wouldnt work, since the driver is almost always part of the crossover networkand couldnt be in a setup like that

If you look in an old active crossover it can have a passive network between 2 simple gain stages and sometimes just one if it's for a specific load (amp set). In theory, if you know both the source impedance is low enough and amp input parameters (impedances and gain which is what the variable gain stages are for) a purely passive setup can be used before the last amplifier stage though it's better to keep things tidier. There are active crossovers on the market today that don't use op amps or DSP. Transistors and passive components to set slope and frequency. Now you may induce the amp to help along buy building a slope via the feedback loop etc but it's done with passive components, almost always with some in the signal path. When I said within gain stages in my earlier post, that's what I was referring to.

FM acoustics uses passive networks between two linear gain stages in their active network for instance which goes to my original option. It counts and that's all I said. I didn't limit active crossovers to passive networks either as I never even hinted that DSP and EQ via a feedback loop wasn't fine as well. All I said is that it wasn't limited to DSP and can use passive networks, as long as they're before the amp stage. That is absolutely true and in no way misleading. There are always amps involved and there will be slopes either within their circuit or before them.

Of course a crossover in front of an amp works. You need more than one amp and put a high pass in front of the tweeter amp and a low pass in front of the woofer amp but you need to know the impedances and gain involved etc. Vandersteen woofers used to come with a small box and that has a couple caps in it to be used in front of the amp. The value is chosen by knowing the amplifier input impedance and works as a 1st order high pass for the main speaker pair. The input impedance of the power amp would take the place of the driver in the network so you'd be picking values for 20K or so instead of 20 ohms. It allows the value of the cap to be 1000 times smaller and the voltages to be 50 times smaller so that better parts can be used under less duress and if designed well, the amplifier still has the type of control, damping and dynamics that you can't get without a direct driver connection.

We can talk semantics but what I said is correct and "An ACTIVE crossover (the operative word is Crossover) HAS NO (meaning, none, zero, zilch, nada, zip, donut) PASSIVE COMPONENTS." is ridiculously strong to be so wrong as was the JHA fanboy assumption.