Air core coil for the wd25tex coil anyone.

[VantheMan]

Well, they´re on their way. Then I´ll have to wait for my EE mate. He insists that he´ll run me up me a new crossover PCB on his machine to admit their large flat spool instead of the stumpy ferrite one. No sweat cos I have my external crossovers in a box next to my amp. He says that after changing the caps and the resistors the original PCBs are looking a bit the worse for wear.
Dunno if I´ll hear anything new but for some reason Peter opted for an air coil on the tweeters so why not on the woofers, I say.
I still prefer listening through my Beyer DT531 cans to any speakers, anyway.

[Yellow]

Originally Posted by VantheMan

Hi,
Yes, according to the Jantzen page the power handling in 14awg is 500w. and the values I chose are 0.76 and 0.21 DCR. Whatever that means. ....

You should be fine. The 0.76 refers to the inductance measured in milli-henries - 0.76mH; and the DCR is the DC Resistance - 0.21ohms in this instance.
Swapping your ferrite cored inductors for air core types is generally a good thing, but if you don't listen at very high-levels, you probably won't notice any improvement. Generally, as the inductor(s) is in series with the LF drivers, they can start to saturate at high levels and air-core types give better results in that regard. The inductors that are in parallel with the tweeter and mid-range if they are 2nd-order or higher, should be air-core where possible.

Regards,

Neil.

[VantheMan]

What happens with 2 ways where the woofer is really a mid-woofer as in my case ?

[Yellow]

Hi,
So in the case of a 2-way, the LF unit is rolled-off at say 3kHz or so using an inductor. A 1st order filter will use just an inductor in series. If it is 2nd order, then you'll find a cap across the +ve & -ve terminals of the driver as well. My comments above still stand. An air-core will generally sound better than an iron-core inductor. The problem with air-cores, is that they can be very large physically, when compared to a ferrite-cored inductor of the same inductance.

Regards,

Neil.

[petercom]

I find the supposition that air core coils sound better than ferrite or iron core coils amusing.

The choice, for the speaker designer, is one of features and benefits:

1. An air core coil generally has a higher DCR given constraints of cost and size.

2. Distortion in well-designed ferrite core coils is relatively low except at very high power levels.

3. The radiated magnetic field of an air core coil is huge while that of a ferrite core coil is constrained and directive.

Point 3 should not be underestimated. Usually I disconnect the feed resistor to the treble crossover and play a 1kHz tone into the bass crossover (with drive unit replaced by a 6.8 Ohm resistor) and listen to what comes out of the treble unit. You can hear the correct orientation of the bass coil on the PCB quite clearly by looking for the null point as you rotate the coil. Air core coils need to be at 90 degrees axes to try and achieve this null point, but this is difficult to arrange with a large bass coil.

For the treble crossover the higher DCR of an air core coil is usually an advantage as it applies some electrical damping to the filter. These coils are typically quite small, so a small iron core would saturate sooner and the resulting distortion be subjectively obvious.

[VantheMan]

Just a thought. Are the XOVRI PCB boards available still ? Or could I get some made up for my externalcrossovers ? Mine are a bit scruffy after changing caps and resistors.