all my old inductors use copper wires with diameters between 0.8 and 1.1mm.
i wanted to get a very long coil and try to make one myself. any advice on diameter?
i wanted to get a very long coil and try to make one myself. any advice on diameter?
Hi Allen,
certainly, I wanted to understand if there is a preference for the tweeter and the woofer, or if I take a diameter of 0.8mm is it good for both?
certainly, I wanted to understand if there is a preference for the tweeter and the woofer, or if I take a diameter of 0.8mm is it good for both?
Generally, a series inductor in the bass circuit should have less loss, hence less resistance, hence larger diameter. A smaller diameter wire in the parallel leg of a tweeter second order or higher circuit is usually just fine. In fact, to broaden the curve, a resistor is sometimes added.
The recommended current density (RMS) for a choke is 3 to 4 amperes per sq. mm. Pick a wire gauge whose "bare copper cross section" satisfies this criterion.
And, skin effect has negligible effect at 20kHz.
https://en.wikipedia.org/wiki/Skin_effect
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Use 24AWG wire air core inductor for tweeter (second order), 20AWG wire laminated core inductor or 16AWG wire air core inductor for woofer
thanks Rick, your clarifications make me understand that I have to use a program and a microphone to see these details. I have to take action in this sense, because listening is important, but you also need to see the curve.
so using an excessive section of wire on the tweeter alters the curve and at listening level can you hear the difference?
This kind of a decision you make when you have a x/o schematic close to being finished.
I read that inductor wire diameter in a high pass filter can make a difference to the sound, but it will usually be small.
However, the inductor resistance should always be included in a filter design simulation in order to note its effect.
Sometimes a complicated computer designed filter can specify a very precise value for the resistance of a high pass coil.
I read it here: https://www.diyaudio.com/community/...does-inductor-awg-matter-for-high-pass.48974/
Design the filter first, figure out the DCR required to achieve the inductor approximate Q you need for your filter, and select a wire gauge that gives <= to that value, you can always add a small series resistance if slightly more resistance is required to get the Q right.
You can play around with different diameters and lengths here: https://www.diyaudioandvideo.com/Calculator/AirCoreInductorDesigner/
I agree with using air core inductors, but disagree with the wire size recommendations. Those recommendations may work for some speakers, but may be sub-optimal for others.
To determine the proper wire size, the desired inductance and DCR for each inductor should first be determined (e.g., by modeling the crossover and drivers in VituixCAD), and then the appropriate wire diameter selected based on the desired inductance and DCR.
Also, I recommend against using laminated core inductors for a midrange. The core losses (both hysterises losses and eddy current losses) increase with frequency and sometimes can have an audibly negative affect on the upper midrange. Sometimes, they steal life and dynamics from a speaker.
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With a crossover inductor the main concern (apart from the inductance value) is the resistance. Every inductor has a different number of turns for example, so you can not choose the wire diameter before you learn these other things.
Rule of thumb is that the inductor should have a DC resistance less than 5% of the DC Resistance of the driver. It should be less than 0.25 ohms for most 8 ohm woofers and less than 0.13 ohms for most 4 ohm woofers. You choose inductor wire diameter based on that. You will find that air core becomes very impractical at low frequencies. Anything below 16 gauge probably only works for tweeters.
If you factor in the DCR in your crossover design, you can use whatever you want and dispense with rules of thumb.
If you factor in the DCR in your crossover design, you can use whatever you want and dispense with rules of thumb.
very interesting what you told me and in fact now that I think about it I understand how in some famous speakers there are complex crossovers and that they also have a resistance immediately after the coil, but perhaps even before. so if I can correct the Q, I can use one diameter for the woofer and one for the tweeter. so I don't buy 10kg of copper. 🙂
Don't overlook overall size of the coil. Some get pretty big. I find it much easier to simply buy a coil.
If you've never tried making one, you may find it is harder than it looks. Mine were sloppy, and it was awkward handling the wire. I might consider making a coil under .5mH, I have an old 4mH that is missing some turns that I could use for the wire. I have a friend with a meter to measure the inductance. I could use a few .4mH. I have lots of coils in my spare parts box, but could use a few in the .4mH range.
I have removed a few turns from a couple of 3.6mH coils to get closer to what I needed.
If you've never tried making one, you may find it is harder than it looks. Mine were sloppy, and it was awkward handling the wire. I might consider making a coil under .5mH, I have an old 4mH that is missing some turns that I could use for the wire. I have a friend with a meter to measure the inductance. I could use a few .4mH. I have lots of coils in my spare parts box, but could use a few in the .4mH range.
I have removed a few turns from a couple of 3.6mH coils to get closer to what I needed.
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I also did it with the ones I had in the can for several years. and for the experiments, rest assured that I will do it again 🙂
Any impedance, such as resistance, you add between the amplifier and the driver lowers the damping factor. The lower the damping factor, the less control the amplifier has over the woofer. The bass can sound a little sloppy, less impactful.
It is hard to do without a winding machine. Here is one on Amazon for $49, whiich currently is $45.08 with a coupon:
https://a.co/d/4L3jxwz
Before I decided to go all active crossovers on my latest project I was looking at buying it. You probably can find bobbins online, but I was going to 3D print a coil form instead. I had planned on tie wrapping the inductors and dipping them in polyurethane.