Crossover components, can i substitute?

[Neo__04]

Hey all,

 

In regards to crossover components, im having a hard time getting exactly the specs i need.
Capacitors - I cant get hold of 20uf caps, but i can get 18uf and 22uf.
Air core inductor - i cant get hold of a 2.50mh 18awg, but i can get a 2.5mh 20awg or a 2.2mh 18awg.

 

Can anyone advise as to how critical these figuires are? And what difference it might make.

 

Thanks heaps

 

 

 

 

[Zaphod Beeblebrox]

Hey all,

 

In regards to crossover components, im having a hard time getting exactly the specs i need.

Capacitors - I cant get hold of 20uf caps, but i can get 18uf and 22uf.

Air core inductor - i cant get hold of a 2.50mh 18awg, but i can get a 2.5mh 20awg or a 2.2mh 18awg.

 

Can anyone advise as to how critical these figuires are? And what difference it might make.

 

Thanks heaps

If the caps are bi-polar electrolytic types, then yes, no problems. Even film types would probably be OK. If you're worried, you could use an 18uF in parallel with a 2.2uF, which would then equal 20.2uF. This would be perfectly acceptable.

Inductors are a little trickier. You need to maintain the same DC resistance, so do not use a smaller CSA wire. You should try to ensure that the new inductors are very close to the originals WRT DCR. Are the originals air core types? If so, leave 'em be. If they're ferrite types, dump them. If they're laminated iron, it's a push.

[kelossus]

SCR make 20uf poly caps.

 

Speakerbits have them but it is cheaper to get them from the US. If you only need a few it wouldn't work out too bad.

Edited April 17, 2016 by kelossus

[Neo__04]

Thanks for the info, i should have been a little clearer with my questions, it may or may not change your answers.

 

Im not substituting parts on an existing crossover,

Im building one from scratch but following a parts list from a diy speaker kit.

 

Not sure whether that changes anything, but thought i had better check

[kelossus]

http://www.speakerbits.com/index.php?page=shop.product_details&flypage=vmj_estore.tpl&product_id=2865&category_id=1017&option=com_virtuemart

[kelossus]

If you have an LCR meter you can wind these down to 2.5mh

 

http://speakerbug.com.au/index.php?route=product/product&path=18_46&product_id=389

[Green Wagon]

If you post the actual schematic, or at the least tell us what it is your building, you will get better answers.

 

kinda like asking if a Champion 9201 spark plug will fit your car when you dont tell us your driving a diesel.........

[Zaphod Beeblebrox]

Thanks for the info, i should have been a little clearer with my questions, it may or may not change your answers.

 

Im not substituting parts on an existing crossover,

Im building one from scratch but following a parts list from a diy speaker kit.

 

Not sure whether that changes anything, but thought i had better check

Nope. Just stick to the values listed and you'll be sweet. Keep to the same DCR for coils and you should expect no problems.

[davewantsmoore]

Can anyone advise as to how critical these figuires are? And what difference it might make.

 

Impossible to say without knowing the circuit they will be placed in.     As a very rough rule, as the order or Q of the filter increases, the value tolerance becomes more critical.

 

 

You would really just have to re-simulate the circuit, with the different value in place, and see how much difference there was (and judge whether that was acceptable)

[Full Range]

If you have an LCR meter you can wind these down to 2.5mh

 

http://speakerbug.com.au/index.php?route=product/product&path=18_46&product_id=389

Adding to this info -

Speaker bug offer a free service for small orders to wind down inductors to the correct or exact value required

So you can't go wrong with that

Capacitors can be joined in series to achieve the correct value required as well

I have done that in my crossovers

[Zaphod Beeblebrox]

Adding to this info -

Speaker bug offer a free service for small orders to wind down inductors to the correct or exact value required

So you can't go wrong with that

Capacitors can be joined in series to achieve the correct value required as well

I have done that in my crossovers

For the values required, series connection of caps is wasteful. Parallel connection is the best approach (in this instance).

[Full Range]

For the values required, series connection of caps is wasteful. Parallel connection is the best approach (in this instance).

Sorry you are correct I meant to write parallel

[Neo__04]

Hey again,

 

Unsure what to do here.

 

I need a 0.4mh 20awg air core.

The one recommended was http://www.parts-express.com/jantzen-audio-040mh-20-awg-air-core-inductor-crossover-coil--255-032

It has 0.43 ohm dcr

 

speakerbug has 0.4mh 17awg (0.212ohm) or 22awg (0.64ohm)

 

I emailed them and they said to go with the 22awg as it would make little difference.

Im not sure what to do now as the general consensus is that i should try and match the dcr so there is no problems.

 

The other one i need is a 2mh 22awg air core, the recommended was

http://www.parts-express.com/20mh-22-gauge-ferrite-bobbin-core-inductor--269-2128

It has 0.34ohm dcr.

 

The one listed on speakerbug has 1.61ohm, that seems like a huge difference. Now im just confused.

 

Can anyone give some guidance here please?

 

Thanks heaps

Edited April 18, 2016 by Neo__04

[Full Range]

Speaker bug will take a larger size inductor and unwind it to the exact value you require FREE of charge

[Neo__04]

yeah i read that earlier.

 

I mentioned that in my email to them and he just suggested to use the 22awg instead.

Id much prefer them matched, as its my first passive crossover and im only running with what someone else has designed up for me.

[Guest Muon]

Deleted...

 

Edit: where in the circuit is this inductor?

 

Don't need to answer this, I am only curious.

Edited April 19, 2016 by Muon

[Neo__04]

Ill attach the crossover diagram.

 

It was designed up for me by a well respected guy on another forum.

He designed it up but rushed through a quick hand drawn diagram to get me going.

So excuse the diagram.

 

Hope this helps

 

[Guest Muon]

It's on the tweeter side, cool thanks

 

Umm, is that a mistake, there is no 20uf cap, only a 10uf, 0,33uf  and 6uf.

[Neo__04]

No sorry it wasnt a mistake. Im looking at making a set of speakers from a kit also.

Some of those parts i mentioned were from the other speakers crossover.

 

I was just asking in the rules in general when I cannot find exact components.

 

I think i read somewhere the the values matter a little less if its on the tweeter side?

Edited April 19, 2016 by Neo__04

[Guest Muon]

As a couple have said with caps, just parallel ones of the same type for the value needed.

 

With inductors do as Paul suggested and get speakerbug to unwind to the required value

Edited April 19, 2016 by Muon

[Neo__04]

Awesome, ill put in my order now and let them know i need that done.

 

Thanks heaps

[davewantsmoore]

I was just asking in the rules in general when I cannot find exact components.

 

I think i read somewhere the the values matter a little less if its on the tweeter side?

 

It's very hard to make general rules.    The actual circuit the inductor is in will determine how critical it's value is.    In a very very general sense, the more complex the filter is, the more critical the values can become.

 

 

Use the 22awg ....  being 0.2ohms off the required value won't make a huge difference.....  obviously, try and get the value of in inductance as correct as possible..

[Guest Muon]

Wouldn't the 0.4mh inductance be more critical than the DCR?

 

I haven't played with inductors used on the tweeter side so I'm not sure on how critical the DCR is here.

Edited April 19, 2016 by Muon

[Green Wagon]

Jantzen list 1,283 different air core inductors.

And then will also custom wind to order....

From looking through the list, and my own experience with making inductors from 10 years ago.

I can tell you that any given inductor can be altered by size design..

 

Let me clarify that.

If we take - for example - a 1mH inductor, then we say it has to be 18awg.

by changing the core size and height of the finished winding, you will end up with very different dcr's.

You will also change the dcr by the sheer method of winding.

 

So, a 1mh 18awg from one maker, will not always be the same as a 1mh 18awg from another. Unless they are wound the same way, to same finished size.

 

gimme a sec and dig up some real examples.

 

Oh, and I didnt reply further here, cause, well, without knowing what and where the inductor is.

It's pointless even beginning to contemplate speculating as to whether .01 Ohms is even relevant in this universe

 

EDIT, here ya go, ive sorted by awg and dcr.

 

Look at a given awg. lets say 18awg, now what dcr did you want ? or is the physical size more important ? Does the 0.04 of an ohm really matter ?

 

 

What I'm trying to get at, is, I have people email me daily, asking for a certain inductance, in a certain gauge. Not the dcr, the awg.

As you see, given mh and awg, the dcr will change.

If my crystal ball is foggy and I can't see if it's feeding a bass driver or doing a tweeter notch filter, then I can only suggest the best of what I have on hand. (last tally $65k in stock)

 

 

EDIT TWO..

And now we have the diagram, the 0.4mH is a parallel inductor for the actual crossover point, so personally i dont see the minor difference in dcr being an issue.

Edited April 19, 2016 by Green Wagon

[Green Wagon]

Sorry if that sounds rude, isn't meant to be.

 

Just had 4 time consuming repairs/build ups come in and trying to get trades people to fix stuff, HA, tuesday he says, yeah two tuesdays have gone past now dude...

 

Sigh. end rant.