# Inductors not having Specs for Crossover



## roryps (Aug 24, 2015)

Hello,

I am new to the DIY speaker building craze and am working on my first set of main speakers. I have selected Zaph Audio 5.5tt due to its smaller size and have been working on the list of items I will need for the crossover, which brings me to the questions I have.

The crossovers call for inductors having 1.8 mH with DCR of 0.2 Ohm and 4.0 mH with DCR of 0.3 Ohm. I checked the usual sites and do not see any meeting these specs.

For the first inductor above I find a foil type 12 awg with 0.091 Ohm, one p-core 15 awg (seems to be on a reel) with 0.17 Ohm, and an air coil 14 awg with 0.3 Ohm resistance (they are all 1.8 mH). The foil type is very expensive and I would like to stay away from that even though it appears to be the most suitable one. Considering the other two, what would be the pros and cons of using either of them?

For the second inductor I found a laminated core 18 awg with 0.39 Ohm, and an air coil 14 awg with 0.5 Ohm, which costs 4x more than the laminated core. Again, what would be the pros and cons of using either of these in the crossover?

I would really appreciate any feedback I can get, and depending on pros and cons of each I will make a decision on what to buy. I may still end up buying the expensive ones if they will what would seem to me to be an advantage over the others.

Thanks in advance for your responses.

Roryps


----------



## fusseli (May 1, 2007)

Go with the p-core and laminated core, they are close enough in DCR. The DCR doesn't have to match exactly it just should be close. You can also wind your own air core inductors if you lookup online calculators.


----------



## roryps (Aug 24, 2015)

First of all, thanks for your response. I really appreciate it.

I made a slight error with parameters of my post.

For the first coil inductor of 1.8mH that I listed, the DCR is 0.19, not 0.091. You mention that I could use the p-core with DCR of 0.17. Cost aside, what would be the pros and cons of using either of these two inductors instead of one with DCR of 0.2?

Thanks again.


----------



## fbov (Aug 28, 2008)

Minimal.

Take a look at Madisound's kit
https://www.madisoundspeakerstore.com/2.5-way-speaker-kits/zaph|audio-za5.5-tall-tower-2.5-way-pair/

Both inductors are iron core. It's the only affordable way to get high inductance with really low DCR. When properly used, and I'd trust Zaph to use them properly, there's no difference from air core. 

HAve fun,
Frank


----------



## fusseli (May 1, 2007)

The different DCRs will very slightly change the response of the crossover, but usually to a small degree. It depends on where they are in the circuit. The worst place for high DCR is in series with a driver. Discriminating a few, or even a hundred, milliohms is a pointless process when the impact is much less than one dB and your component tolerances are already 5% anyways.


----------



## dgmartin (Oct 29, 2011)

From the kit picture, Zaph specifies Iron core for both. There is no harm using the p-core. If you have an LCR meter, you can probably get the 2mH and remove a few turns. The iron core are listed on this page: https://www.madisoundspeakerstore.com/compare-steel-laminate. Your DCR will be on the low side but insignificant as others mentioned. I would not bother adding a series resistance to match the DCR in the schematic. Any reason you want to build the crossover yourself instead of purchasing that from madisound?


----------



## roryps (Aug 24, 2015)

Thanks for the responses. I really appreciate it.

I may just end up purchasing the pre-built XO's but was just thinking that I would make it a true DIY job.


----------



## dgmartin (Oct 29, 2011)

roryps said:


> Thanks for the responses. I really appreciate it.
> 
> I may just end up purchasing the pre-built XO's but was just thinking that I would make it a true DIY job.


You could always ask Madisound which Iron core they used for 1.8mH in the kit. Maybe they used 2.0mH, maybe they can provide the 1.8mH if you want to DIY...


----------

