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[billy merritt]

Hi, please help! I've been trying to track down a 2 way passive crossover for a speaker with a 15" woofer and 2" compression driver (rcf850). There are all sorts of options but nothing even close to the specs I'm looking for! Basically I need something fit for a 600 watt speaker where the crossover point is around 800-1000khz. Any guidance of where to find this crossover would be so very appreciated!!

[Ivan Beaver]

Hi, please help! I've been trying to track down a 2 way passive crossover for a speaker with a 15" woofer and 2" compression driver (rcf850). There are all sorts of options but nothing even close to the specs I'm looking for! Basically I need something fit for a 600 watt speaker where the crossover point is around 800-1000khz. Any guidance of where to find this crossover would be so very appreciated!!

The only proper crossover would be the one designed for the cabinet.

Any generic crossover make a lot of assumptions (flat amplitude-flat phase-flat impednace etc) NONE of which your cabinet actually has.

So the actual crossover points will not be what you are expecting and could give some odd freq responses.

If you look at most designed crossovers, they do not "follow the math" that the off the shelf units do.  That is because they are designed for a particular cabinet and components. 

Changing the crossover or the drivers will result in different (often worse) performance

[Dave Pluke]

As Ivan said, (proper) crossover design can get complicated.

If you're looking to build your own, this link could help identify the various values you'll need:

https://www.diyaudioandvideo.com/Calculator/SpeakerCrossover/

As to capacitors, this brand has a pretty good reputation (just picked 20uF as an example, your needs may be different):

https://www.parts-express.com/solen-20uf-400v-polypropylene-capacitor--027-582

Time alignment and output matching are beyond the scope of that calculator.

Dave

[Ivan Beaver]

As Ivan said, (proper) crossover design can get complicated.

If you're looking to build your own, this link could help identify the various values you'll need:

https://www.diyaudioandvideo.com/Calculator/SpeakerCrossover/

As to capacitors, this brand has a pretty good reputation (just picked 20uF as an example, your needs may be different):

https://www.parts-express.com/solen-20uf-400v-polypropylene-capacitor--027-582

Time alignment and output matching are beyond the scope of that calculator.

Dave

The calculators can give a "start", but ONLY if you enter in the ACTUAL impedance around crossover-NOT the rated impedance.

And NOT the DC resistance.

And the SPL of most horn/driver combinations is much greater at typical crossover freq, which must be dealt with in order to get a flat response.

This does not show up in the calculators

[Scott Holtzman]

The calculators can give a "start", but ONLY if you enter in the ACTUAL impedance around crossover-NOT the rated impedance.

And NOT the DC resistance.

And the SPL of most horn/driver combinations is much greater at typical crossover freq, which must be dealt with in order to get a flat response.

This does not show up in the calculators

This is so important.  Designing passive crossovers is an engineering task.  A proper crossover is a work of art as it uses analog components to take into account component and systemic non-linear response.

Ivan's comment about measured (or measured for you) impedance is so important.  The least expensive entry into this is the studio six digital impedance sweep software and the special interface.

You also have to test the driver in the cabinet it will be used.  The driver will exhibit different characteristics in the cabinet as the driver has to work harder to overcome the acoustic impedance of the crossover.

Once you figure all this out now you are ready to start designing a crossover.

This is a big task and to me it is much simpler to use an external electronic crossover.

[Ivan Beaver]

This is so important.  Designing passive crossovers is an engineering task.  A proper crossover is a work of art as it uses analog components to take into account component and systemic non-linear response.

Ivan's comment about measured (or measured for you) impedance is so important.  The least expensive entry into this is the studio six digital impedance sweep software and the special interface.

You also have to test the driver in the cabinet it will be used.  The driver will exhibit different characteristics in the cabinet as the driver has to work harder to overcome the acoustic impedance of the crossover.

Once you figure all this out now you are ready to start designing a crossover.

This is a big task and to me it is much simpler to use an external electronic crossover.

And when you start to consider the phase response (NOT POLARITY), it gets a lot harder.

Simply dividing freq is easy.

Getting a smooth amplitude and phase response is not so easy.

[Chris Grimshaw]

You also have to test the driver in the cabinet it will be used.  The driver will exhibit different characteristics in the cabinet as the driver has to work harder to overcome the acoustic impedance of the crossover.

Acoustic impedance of the crossover..?

What?

Measuring the driver in the cabinet is good to do - you'll get baffle-step, diffraction, standing waves etc all showing up in the frequency response.
I know all the words in your sentence, but AFAIK it makes no sense from a Physics point-of-view.

Chris

[Scott Holtzman]

Acoustic impedance of the crossover..?

What?

Measuring the driver in the cabinet is good to do - you'll get baffle-step, diffraction, standing waves etc all showing up in the frequency response.
I know all the words in your sentence, but AFAIK it makes no sense from a Physics point-of-view.

Chris

My apologies, should have read (and please let me know if this makes sense).

You also have to test the driver in the cabinet it will be used.  The driver will exhibit different characteristics in the cabinet as the driver has to work harder to overcome the acoustic impedance of the crossover.

[Stephen Kirby]

I think what Scott meant is that the cabinet will mechanically affect the driver such that it's electrical impedance would be different with frequency than in the free field.  And hopefully it's fairly linear though the chosen crossover region or you're going to have to put all kinds of frequency dependent impedance corrections in there, which will further mangle the phase response.  It gets really complicated really fast if you want to do it right.  Speaker design is juggling many tradeoffs.  The days of just putting drivers you like into a cabinet and hoping for the best are long gone.  Finding drivers that play together nice around a useful crossover point in a cabinet and with a horn that does what you want is an art that folks spend lifetimes working at.

[Rob Spence]

Is this cabinet a commercial product? If so, what is the brand & model?
If it is a home brew, perhaps the simplest thing, though obviously more expensive, would be to bi-amp and use a simple speaker processor with something like smart to get a good crossover?

Without lots of knowledge & tools, building a passive one that works right seems unlikely. You would at least need the same measuring tools as above.

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