How to select cross-over components ? - Help

[ukjeyaraj]

This is about selecting the cross-over parts. Every cross-over is made with some capacitors, inductors and resistors (if there is anything more, please mention)

Capacitors

There are various types like, electrolytic, metal film, polypropylene and then radial, axial (based on leads) and then polarized, non-polarized, bi-polarized. Also there is some voltage rating in capacitors (from 15V to 450V and may be beyond too)

Almost all websites advise to use the polypropylene capactiors only.

1) In case of non availability is it ok to use other capacitors.
2) How to choose the voltage?
3) Is there some capacitors which are strict no for cross-over

Inductors

Here again, there are various types like air-core, ferrite-core, etc and then some inductors looking similar to resistors

What are those inductors that look like resistors, whether this can be used in the cross-over

Resistors

Again there are different types with some watts rating. How to choose the watts rating in the resistor

 

[yugaaa]

Selecting crossover components is not very difficult in India .The reason is you do not have much choice of components . You will have to use what is avaliable . Implementation is the key rather than the choice of components . The most important thing you will have to look at are the inductors and not the other components as inductors are not avaliable off the shelf . You will have to either wind them or get them wound for the values which is very difficult .

Regarding resistors and electrolytic capacitors ,it again depends on the circuit rather than individual components . 5-10 w resistors are the norm usually .

 

[GeorgeO]

I agree.Caps and resistors arent a problem, inductors generally are. I use 14 ga wire wound inductors.

 

[ukjeyaraj]

Does it mean any type of capacitors will do? Like electrolytic with plus and minus or small 16V capacitor also

 

[t.antony]

Capacitors

There are various types like, electrolytic, metal film, polypropylene and then radial, axial (based on leads) and then polarized, non-polarized, bi-polarized. Also there is some voltage rating in capacitors (from 15V to 450V and may be beyond too)

Almost all websites advise to use the polypropylene capacitors only.

1) In case of non availability is it ok to use other capacitors.
2) How to choose the voltage?
3) Is there some capacitors which are strict no for cross-over

Metalized poly-propylene caps(MPP) are available in India and available up to 10 mfd range. If the circuit requires a higher value, use a parallel combination to arrive at the required figure. Polyester caps can also be used for small value adjustments.

It's better to avoid non-polarized electrolytic caps if you could get the required value with a combination of MPP and Polyester caps.

The MPP caps will be normally rated at 250V - which would be more than sufficient for most solid state amps. If you are using a tube amp, need to choose voltage rating based on the working voltage of the amp.

Polarized electrolytic caps are not suitable for crossover duty.

Inductors

Here again, there are various types like air-core, ferrite-core, etc and then some inductors looking similar to resistors

What are those inductors that look like resistors, whether this can be used in the cross-over

Use air core inductors where ever possible. As earlier mentioned in this thread, you might need to get these custom made as they not readily available in India. Use thicker wire to reduce the DC resistance (I use 19 SWG wire, but lower gauge is better). Off the shelf inductors similar to one shown are normally made for using in other signal applications and should never be used in a loudspeaker crossover.

Resistors

Again there are different types with some watts rating. How to choose the watts rating in the resistor

You can use non-inductive wire wound resistors in the low pass section. Normally these comes in 10w packages, the power can be doubled by using them in parallel. 20w should be sufficient for normal applications. For mid and high pass section, metal oxide resistors are considered good. Power requirements are less compared to the low pass and 10w rating should be sufficient in most cases.

 

[ukjeyaraj]

The MPP caps will be normally rated at 250V - which would be more than sufficient for most solid state amps. If you are using a tube amp, need to choose voltage rating based on the working voltage of the amp.

Polarized electrolytic caps are not suitable for crossover duty.



Off the shelf inductors similar to one shown are normally made for using in other signal applications and should never be used in a loudspeaker crossover.


You can use non-inductive wire wound resistors in the low pass section. Normally these comes in 10w packages, the power can be doubled by using them in parallel. 20w should be sufficient for normal applications. For mid and high pass section, metal oxide resistors are considered good. Power requirements are less compared to the low pass and 10w rating should be sufficient in most cases.

Thanks for the detailed explanation. Above points answered almost all the queries.

One more doubt, for higher value of capacitors (when not available), you have mentioned to use them in parallel. Does it mean that if I want 50 mfd capacitors, we can use 5 piece of 10 mfd capacitors in parallel.

 

[yugaaa]

One more doubt, for higher value of capacitors (when not available), you have mentioned to use them in parallel. Does it mean that if I want 50 mfd capacitors, we can use 5 piece of 10 mfd capacitors in parallel.

Yes , you will have to use 5*10mfd or you can use a non -polar electrolytic cap as well .

 

[yugaaa]

Another point with inductors is our wire gauges are SWG . most of the DIY projects come with AWG specs . So the first investment in winding your own crossover or getting it done would be a LCR meter .

Also using thicker wire for reducing resistance has its side effects as well . Thicker wire needs more turns for the same amount of inductance a thinner wire needs .
So as a general rule ..
1. tweeter do not require a lot of power , so use thinner wires for them .
2. woofers need a lot of power use thicker wires for the inductors .

 

[ukjeyaraj]

@yugaa. Thanks for the tips.

Do you mean LCR like this ::::: Kusam-Meco :::::

Can it read and measure value less than 1mH also.

 

[yugaaa]

6030

that one seems a better model .

 

[yugaaa]

@yugaa. Thanks for the tips.

Do you mean LCR like this ::::: Kusam-Meco :::::

Can it read and measure value less than 1mH also.

yes it can read because the resolution says it has .1mh