Question about crossover components

[dvjorge]

Hi everyone,

I have been looking for the needed components to build the crossovers for my speaker project. Since I haven't experience and enough knowledge, I would like to clarify some questions before buying anything. First, are 5W resistors ok for crossovers ??, Second, what is the minimum voltage required for the capacitors ?? 100 volts ?? I have selected polypropylene non-polarized capacitors but I am not sure what voltage is correct. (think about 100 watts) and third and last question, can I chose any inductor as long as it be the crossover designed value or I need to look at the AWG and the core too?? I have selected the components from Parts Express and some of them say ideal for crossover but others not. If this matters, my project is a two way sealed bookshelf using a 8" woofer plus a 1" metal dome tweeter.
Thank you so much for any help.

 

[Sonce]

5W resistor is marginally OK for a tweeter filter, but it depends on the actual value and role, so go for a 10W.
100 V capacitors are OK.
If the inductor is cored, it must be rated above 150 W. Do not look at AWG, low DC resistance is the goal - less than 0.8 ohms for a 8-ohm woofer and less than 0.4 ohms for a 4-ohm woofer. Inductor for tweeter filter may be (or not) with higher resistance.

 

[Tweet]

Just on a capacitor's voltage rating, even though one may get away with using a 100 v rating (that is likely it's maximum DC working voltage) it's AC working voltage will be lower, possibly 70v AC. If you are using the 2 way speaker limited to a moderately high power level the rated capacitor is likely to be okay, it would be more prudent to use a capacitor with a 250 volt rating though.

C.M

 

[dvjorge]

I only looked to Part Express and I can not find a huge selection to chose. Is there any other online place to buy the components offering more than what Part Express have ?? Please, advice.!

 

[dvjorge]

I need two 0.39mH coils but can not find any having a DC of 0.8 ohms or less.! These two are for the tweeter section, so I don't know if they have to be less than 0.8 ohms. What I find is 1.8 ohms.

 

[eriksquires]

Try Parts Express. You should easily find what you need for inductors:

Jantzen Audio 0.39mH 15 AWG Air Core Inductor Crossover Coil

 

[giralfino]

In Europe a 0.39mH coil is pretty easy to obtain as it is part of the standard 12 value chain, it seems that in the States it is not. Try a 0.4mH coil instead, you'll be hard pressed to notice the difference once you factor in the tolerance.

Ralf

 

[kimmosto]

First, are 5W resistors ok for crossovers ??

5W is usually enough, but there are some exceptions where 10W is safer as default value:
* Resistor for baffle step compensation circuit, no matter is it done with parallel (L||C||R) or series notch (R+L+C) or L||R.
* Series resistor for level dropping of lower midrange driver if attenuation is more than 3dB.
* Resistor of Zobel (Le compensation) for 4 Ohm woofers and subwoofers.

 

[gfiandy]

The tweeter inductors do jot need to be low resistance they are inseries with a Q modifying resistir of 3.9 R the total should be 3.9 so if the coil is 0.4 a 3.3R is probably about as close as you will get. If you go with these .4mH parts they will probably be fine they are 5% tolerance any way, I will check the change on the sim but I doubt it will be significant.

Dayton Audio 0.40mH 20 AWG Air Core Inductor Crossover Coil

 

[gfiandy]

The 0.8 R 0.39 inductors should be fine as well a 3R resistor with these would give you quite a close match.

 

[gfiandy]

I think you can set up a personal account with Newark these days for a larger choice of passives.

http://www.newark.com/c/passive-com...-purpose-dc-film-capacitors?capacitance=6.8uf

 

[Keruskerfuerst]

Do you have a crossover calculation program like LSPCAD ?