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Explain crossovers to me..different designs.

Phototone

Phototone

Super Member
Some of the simplest multi-speaker systems just have a capacitor in series with the tweeter..and I understand that, to limit the low frequencies from getting to the tweeter, some slightly more sophisticated networks have resistors AND capacitors, and I think I understand that, to "balance" the output between the mid-range and tweeter to the woofer. Now here is the part I am hazy on...what do inductors (air core or iron core) do that is an improvement over the simpler set-ups? Some of the simple crossover speakers I have sound real good, as do some of the much more sophisticated crossovers that have capacitors, resistors and inductors. Really like some insight here.
 
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In adio terms, a capacitor will block bass and let treble pass. The frequency where this happens is governed by the capacitor value and the resistance of the load. An inductor basically does just the opposite. It will block treble and pass the bass.

A 2nd order filter will have both elements. For instance a 2nd order high pass filter for a tweeter would have a cap in line to block bass and an inductor in parallel so that bass that does get through the cap gets routed to ground instead of through the tweeter. The higher order will give a higher slope on the filter.

That help?
 
RayW said:
In adio terms, a capacitor will block bass and let treble pass. The frequency where this happens is governed by the capacitor value and the resistance of the load. An inductor basically does just the opposite. It will block treble and pass the bass.

A 2nd order filter will have both elements. For instance a 2nd order high pass filter for a tweeter would have a cap in line to block bass and an inductor in parallel so that bass that does get through the cap gets routed to ground instead of through the tweeter. The higher order will give a higher slope on the filter.

That help?
Click to expand...

Yes, a bit.
 
Maybe what we're missing here is the reason for wanting filters with higher performance (steep cutoff slopes). Usually the dominant reason is to reduce overlap in driver frequency response, which can cause destructive interference in the final acoustic output, and interfere with the designer's preferred 'voicing.' Another reason is to improve power-handling capability by keeping low-frequency energy out of the higher-frequency drivers.
 
RayW said:
In adio terms, a capacitor will block bass and let treble pass. The frequency where this happens is governed by the capacitor value and the resistance of the load. An inductor basically does just the opposite. It will block treble and pass the bass.

A 2nd order filter will have both elements. For instance a 2nd order high pass filter for a tweeter would have a cap in line to block bass and an inductor in parallel so that bass that does get through the cap gets routed to ground instead of through the tweeter. The higher order will give a higher slope on the filter.

That help?
Click to expand...
Thats a good explanation, may I add the resistors are used as "slope" contours.
They decide the amount of db per ocatve the filter drops off.

Good thanks
 
So, lets see, in looking at a crossover design, if I see an inductor in parallel across the tweeter connections, it is used to shunt the low frequencies to ground? If I see an inductor in series with a Woofer, it is used to "pass" the low frequencies only to the woofer?
 
DaWoofer said:
If caps block "bass" then why are there such big caps in series with woofers?
Click to expand...
Could be a high pass at 30hz or something like that. If you can check the specs of the speaker and see what bandwidth the woofer covers, it might only go down to like 30 or 40hz in which case it will need a filter to achieve this.

Good thanks
 
Yeah, that's one reason. Especially in ported enclosures where the system will "unload" the woofer below the tuning frequency. If you've got a signal with bass below that cutoff you can do some damage to your woofer.

Another reason for a big cap in series with a woofer is to get a bass boost. It sounds counterintuitive but it works. If you put a cap on a woofer as a high pass and you set values so that the Q of the filter is > .707 then you'll get some boost just above the filter. As an example you could take a woofer that starts to roll off at 30Hz and with the right filter at 25Hz you could get a boost between 25 and 30Hz of a dB or two.
 
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