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olbonco

Forte II crossover

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Does anybody know the DCR or the wire gauge of the forte II, 0.16 Millihenry iron core. I would like to upgrade my crossovers.

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Welcome to the board,

The .16mH is an air core inductor for the HF and is such a small value (read not a lot of wire) that the DCR would be minimal .

 

The 2.75mH inductor is an iron core and the OEM schematic specifies that the DCR to be less than .4 ohms.

 

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Some typical DCR values would be

 

air core .16 mH

  • 18ga ~.15 ohm

  • 16ga ~.1 ohm

 

iron core 2.75mH

  • 18ga ~.34 ohm

  • 16ga ~.2

Naturally the resistance goes down as the wire size goes up.

 

On my first budget forte II crossovers I used 16ga for both coils and was happy with the results. I went with 14ga on the 2.75mH coil with the next pair built. But unless you push gobs of power through your forte IIs, or you are pk with the extra cost, the 16ga will be fine.

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Thanks Alexander,

 

Can the 2.75mH be a air core? Does the mH have to be exact? Can it be 2.7 mH or .15 mH. Seems hard to find exact measurements when looking for components.

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Sure you could use an air core coil for the 2.75mH. But because it would need so much more wire the max of .4 ohm DCR will force you to go way up in wire size (read more $$). Also, air core coils are a lot more sensitive to proximity of other coils.

 

As for .15 or 2.7mH, I am sure many people have done it that way. In my case I guess I'm just too anal when it comes to spec's. So I would buy the next higher value IE: .18 or 2.8mH - measure them and then unwrap the coil(s) to reach the .16mH or 2.75mH final remeasured value.

 

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9 hours ago, olbonco said:

Thanks Alexander,

 

Can the 2.75mH be a air core? Does the mH have to be exact? Can it be 2.7 mH or .15 mH. Seems hard to find exact measurements when looking for components.

Personally, I would have no issue deviating from spec as you mention.  There is always a a fair amount of variation in component specs. Sometimes they average out if you replace with a lower value, but not always. Capacitance  meters are not that expensive if you want to go that route. Remember, you will need to scrape off the wire varnish if you reduce coiled wire in a higher value piece. 

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On 2/15/2021 at 9:58 AM, olbonco said:

Does anybody know the DCR or the wire gauge of the forte II, 0.16 Millihenry iron core. I would like to upgrade my crossovers.

Truth is, DCR is less important than the impedance of the coil in its position in the crossover. When a crossover is designed, coils are measured in place and the measurement includes any mutual-induction of other coils/components nearby. Variations in DCR or impedance, and even mH and capacitance for that matter, will be impossible to differentiate audibly if values are within about 10% of original. If a coil is close to another coil  in the original design, consider that in your 10% range. Crosstalk is the real issue and coils have to practically be on top of one another for it to be an issue.

 

There is an article (the second link I posted) where the guy measures various coil positions, it can give you a fair idea of how coil proximity will raise or lower the overall value. In other words, if you are building a copy of an existing crossover or stuffing new parts on an existing crossover, you'll get real close with just a couple of careful considerations. 

 

Here are a couple of links:

https://www.youtube.com/watch?v=FrVobPkP6fk

http://www.troelsgravesen.dk/coils.htm

 

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You should measure a coil while it’s on the board, both inductance and DCR, and match it.

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