If a crossover design calls for an 8mH / 0.790 Ohms and the two closest options are 8.2@0.800 ohms (Solen) or 8.0 @ 1.75 ohms (Janzen), which would be better or does it even matter? Actually I've already purchased the 8.0/1.75 Janzen which I suppose I could return. Any issues with either of these? If it matters, this is for a first order XO on the woofer with only a single inductor. Thanks
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A loudspeaker crossover inductor would typically have a DC resistance in the order of ohms, not hundreds or thousands of ohms.
It would appear to me that you have read the crossover design requirements incorrectly.
Give us more details of the crossover design specifications for additional assistance.
EDIT: For an 8 mH inductor in series with a woofer you are probably looking at an iron core inductor.
A typical commercial value would be 8.2 mH inductance and 0.75 ohm resistance.
It would appear to me that you have read the crossover design requirements incorrectly.
Give us more details of the crossover design specifications for additional assistance.
EDIT: For an 8 mH inductor in series with a woofer you are probably looking at an iron core inductor.
A typical commercial value would be 8.2 mH inductance and 0.75 ohm resistance.
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My apologies. Meant to say 790 mOhms (0.790 ohms) vs 1.75 ohms. Original post has been corrected. The design is for a first order 600 Hz XO point on the SB Acoustics 15OB350. Basically, I have the correct 8.0mH Janzen coil, but it has twice the DCR of XO spec. The other available option (Solen) is 8.2mH with around 800 mOhms DCR....... Will I have any negative effect with higher DCR of the Janzen, vs lower DCR but slightly higher Henry's of the Solen....or am I overthinking this?
I would say so.
For a simple inductor in series with a woofer filter the small difference of 2.5% in inductor value is negligible.
A small value of inductor resistance gives the amplifier tight control over the woofer's resonance.
A larger value of resistance means less amplifier control, but that may be preferable with some woofers.
The series resonant tank across the amplifier is pointless, has no effect on the drivers, only serves to load your amplifier. Perhaps the inductor and resistor should be across the tweeter in order to give a 12dB/octave high-pass, instead of 6dB. 10% variation in inductor and capacitor values is to be expected and not an issue, ie 7.2 to 8.8mH. The dips and peaks of speakers make minor XO variation irrelevant. Some may suggest a 12dB filter on the woofer, but I think that would be a mistake. A cap across the woofer makes it ~bright because the driving impedance at high frequencies is lower.
Hi,
The best way to assess these 2 inductors is to simulate both options (Inductance + resistance) and observe the frequency response and impedance.
Then you can judge if the difference is relevant for you.
Considering just the resistance part of speaker impedance (8ohms), the loss if using 0.79ohm is around 0.4dB and if using 1.79ohm is 0.9dB.
Around the resonace region, where the speaker impedance varies a lot, the losses will be different and will vary according to the frequency.
Better simulate and see all the details.
It does matter. I would go with the Solen due to the lower DCR. You can get yourself a LCR meter and unwind it to the exact inductance value if you are so inclined. Nonetheless, 8.2mH is within a pretty good tolerance of 8.0mH.
The reason lower DCR is preferable is due to damping factor. The lower the impedance between the amplifier and the woofer, the greater control the amplifier has over the woofer.
Yes, it matters, the higher series impedance acts like an attenuator, as well as considerably reducing the damping factor.
At Fb, the woofer will be near it's DC resistance of 7.2 ohms:
As well as reducing the available amplifier power output due to the higher impedance, the 1.75 ohm inductor would drop nearly 2dB of available sound output to heat, the .8ohm inductor less than half that loss.
As Terry mentioned, you could drop a few windings to lower the inductance and get the DCR the same as the 8mH/0.790 Ohms design specification.
Art
2 cents >
Go for the lower DCR inductor.
[ you can even finely/subtly reduce the 'effective inductance' with a rather high value resistor in parallel rather than 'unwinding' ]
Go for the lower DCR inductor.
[ you can even finely/subtly reduce the 'effective inductance' with a rather high value resistor in parallel rather than 'unwinding' ]
You'll want the one with the 0.8 Ohm DCR then. If you don't like its 8.2 mH value, you can take of a few windings to get down to 8.0 mH (and slightly lower DCR even closer to the value shown on the diagram).
A suitable inductor for 600Hz is something like this:
https://www.parts-express.com/Jantzen-6085-2.2mH-14-AWG-C-Coil-Toroidal-Inductor-255-808?quantity=1
Note that he DC resistance is 0.06 Ohms. An inductor with 0.8 Ohms DCR is too small and also may saturate causing distortion.
https://www.parts-express.com/Jantzen-6085-2.2mH-14-AWG-C-Coil-Toroidal-Inductor-255-808?quantity=1
Note that he DC resistance is 0.06 Ohms. An inductor with 0.8 Ohms DCR is too small and also may saturate causing distortion.