passive x-over - does inductor awg matter for high-pass?

[sardonx]

Does a smaller or bigger guage of inductor sound better for high pass sections of passive crossovers? Should I spend the extra money on the larger inductors or will this not make a difference?

Thanks guys,

sardonx

[Jonathan Bright]

Fair question. The theory behind using the larger gauge wire for inductors in Xovers is to reduce the DC resistance of the inductor or coil. In low-pass sections this has two advantages; the lower resistance allows more power to reach the speaker and not be dissipated in heating the inductor and also the lower resistance will help maintain a lower DC resistance of the whole wiring system from the amp' to the voice coil. This will aid the damping of the bass speaker. Now, neither issue will really apply to the same extent with a hi-pass section so if you have a limited budget it makes sense to invest more in a low DC resistance inductor for the bass speaker. On the other hand some of the coils in low pass section can get pretty big and if you attempt really low DC resistance you ger a very big coil you are asking the signal to travel through a very long piece of wire and most of us are trying to move our signal through short wires.
Like most things a good listening test will help but by then you've wound at least ONE large inductor.

Just re-read your post. It's really about the Hi-pass isn't it? If you read the literature you can get some people specifiying very precise values for the R of hi-pass coils. At one stage KEF wanted a small inductor (0.3 mh) to have 0.55 ohms DC resistance when feeding its T27 through a complicted computer designed network. That would be after using more sophisticated facilities than most of us have. On another track VIFA went through a phase when they used larger coils and smaller caps so as to have a low impedance path across the voice coil of their tweeters and aid damping of the resonance. (The LC time constant was the same for the relevant xover point but they just scaled the inductors up and the caps down to some extent.) This only applies when the coil is the last component before the driver. IE 2nd and 4th order networks.
Like a lot of things on this forum you will probably end up being told to experiment and see what you enjoy. It would be interesting to hear the result of what you come up with. I can't recall seeing much published on this question.

So these comments probably haven't helped at all! Sorry.

Jonathan

[sardonx]

Hey.. thanks anyways! I think i will go for the large coils all around.... I'm trying to go all out for my next project!

Sardonx

[BillFitzmaurice]

I don't bother with large coils and/or solid cores for HP sections. They are necessary with LP sections to keep DCR, and thus insertion losses, low. Those also have to deal with large amounts of current, so a large gauge is required. But in a HP section all the coils are doing is shunting current to ground after it has already passed through at least one capacitor, which means there isn't a lot of current there and small gauge air core coils will do.

[Svante]

Originally posted by sardonx
Does a smaller or bigger guage of inductor sound better for high pass sections of passive crossovers? Should I spend the extra money on the larger inductors or will this not make a difference?

Yes there will be a difference, but it will be small. In the high-pass section, the coils are typically connected to ground. Take the second order filter as an example, with a capacitor in series and an inductor in parallel. The impedance of the inductor decreses toward lower frequencies, and the impedance of the capacitor increases. The net effect of this is a 12 dB/oct slope below cutoff. Now, if the inductor has a series resistance, its impedance will stop to decrease at a certain frequency and the slope will ultimately be only 6 dB/oct.

Also, the resistance can affect the behaviour around the cutoff frequency, and it is hard to tell how much without a simulation.

However, this happens to any coil, the question is only at which frequency. Usually it is not a big problem in the HP section, but any filter design should be simulated with the resistances included, and then it is easy to see the effects of the coil resistance.

So, the bottom line here is; yes it can matter, probably less in the HP section than in the LP section, and a simulation is always good to do.