Do any of you have any experience with replacing standard coils in speaker crossovers with this type of coil (copper foil).
What is the expected audible improvement?
http://www.audiocominternational.co...cat&strKeywords=&strSearchCriteria=&PT_ID=140
What is the expected audible improvement?
http://www.audiocominternational.co...cat&strKeywords=&strSearchCriteria=&PT_ID=140
Copper foil inductors generally have lower resistance than standard wire inductors which will result in higher Q - this isn't necessarily always a good thing as it results in changes in x-over behavior in the transition region of the filter. (Typically excessive peaking just below the x-over frequency)
I learned the hard way that the components chosen by the speaker designer often have characteristics such as ESR in the case of capacitors and DCR in the case of inductors which may deliberately be used to control the Q of the filter being implemented.
I rebuilt the xo in a pair of AR 58's years ago and got more resolution and badly overdamped bass response - overall I did not like the result, much less musical and I didn't realize at the time what the problem was.
If you are designing from scratch none of this is really an issue if you use a good design tool and have the specs for the parts you are planning to use.
Kevin
I learned the hard way that the components chosen by the speaker designer often have characteristics such as ESR in the case of capacitors and DCR in the case of inductors which may deliberately be used to control the Q of the filter being implemented.
I rebuilt the xo in a pair of AR 58's years ago and got more resolution and badly overdamped bass response - overall I did not like the result, much less musical and I didn't realize at the time what the problem was.
If you are designing from scratch none of this is really an issue if you use a good design tool and have the specs for the parts you are planning to use.
Kevin
Apart from measureable properties such as lower DCR (typically) there are things that are different to "normal" wire inductors, which probably can't be measured, but may be audible nevertheless. Such as the di-electric. Polyprop versus a varnish type of coating? And the thickness which is said to influence things like skin-effect (which many dismiss as irrelevant in AF) Also the taughtness with which the respective coils are wound might influence sound...for instance the foil might "ring" more...
O yes..and I suppose the capacitance will also be very different between the types. ( Which I notice is not mentioned in the datasheet)..I suppose it is the same as with psu chokes where you want as little hf to pass as possible...i.e. you want as low as possible capacitance as that will pass the hf ..in this case a musical signal ..but still) It seems to me ..purely from a theoretical point of view that the foils are almost how you would build a capacitor
(only it is one big foil not 2)
Feel free to disregard my pseudo scientific garble..either because it is not an answer to your question or because you think it is claptrap.
O yes..and I suppose the capacitance will also be very different between the types. ( Which I notice is not mentioned in the datasheet)..I suppose it is the same as with psu chokes where you want as little hf to pass as possible...i.e. you want as low as possible capacitance as that will pass the hf ..in this case a musical signal ..but still) It seems to me ..purely from a theoretical point of view that the foils are almost how you would build a capacitor
(only it is one big foil not 2) Feel free to disregard my pseudo scientific garble..either because it is not an answer to your question or because you think it is claptrap.
Hi Bas,
I have found copper foil/teflon-tape DIY inductors superior to wire wound in high current applications. I built 1' wide foil inductors for my Apogee Full Range speakers where the Krell amps push 70 amps into a 0.1 ohm load. Under high currents the foil inductors do not create audible vibration noise like wire wound. It is easier to uniformly wind 12 guage copper foil than 12 guage wires.
The best digital amps use foil inductors for their high current output filters.
I have found copper foil/teflon-tape DIY inductors superior to wire wound in high current applications. I built 1' wide foil inductors for my Apogee Full Range speakers where the Krell amps push 70 amps into a 0.1 ohm load. Under high currents the foil inductors do not create audible vibration noise like wire wound. It is easier to uniformly wind 12 guage copper foil than 12 guage wires.
The best digital amps use foil inductors for their high current output filters.
I think the foil tends to be preferable mainly because of the low DCR (in series with woofer). In 'character' of the sound, I think I like Solen Heptalitz better. I think this in line with general phenomenon: stray (probably silver) is soft or suitable for bass, solid (probably copper) is suitable for tweeter (detailed). I'm not sure if Solen Heptalitz is exactly better but I don't bother to use more expensive than a heptalitz.
Since low DCR is obviously desirable, as well as the signal not going through a kilometer of wire in a coil and eliminate dancing inductors from the magnetic field induced by a bunch of turns, for lower power apps ( <50W ), would it not also make sense a few turns of largish wire on an iron-bar core?
In many cases the designer will deliberately choose inductors with a specific dcr and capacitors with a specific esr in order to control the q of the filter without resorting to using external resistors.
Voicing of loudspeakers & cross-overs is generally finished with a lot of critical listening with drivers selected by measurement to represent the driver characteristic mean.
Higher quality speaker systems from high end designers would generally use better inductors and capacitors and real resistors to control the q.
I worked for a large nameless speaker/electronics manufacturer in the Boston area for 9 years and participated extensively in new speaker design evaluation.
Kevin
Voicing of loudspeakers & cross-overs is generally finished with a lot of critical listening with drivers selected by measurement to represent the driver characteristic mean.
Higher quality speaker systems from high end designers would generally use better inductors and capacitors and real resistors to control the q.
I worked for a large nameless speaker/electronics manufacturer in the Boston area for 9 years and participated extensively in new speaker design evaluation.
Kevin
Series resistance does indeed modify the Q, as it modifies the Qe of the element in question. This can also be used to deliberately modify the Qt of an element, particularly in respect to bass response.
As for modelling or simulating a filter, the series resistance of the inductors should absolutely be included in the sim's, and the load resistance of each element should be represented by a network as close to real as possible,- at least including the inductance and series resistance of each element.
Anyone doing sim's with inductors without series r and using constant R loads instead of real netowrks , are in for a huge surprise. Try both versions if you don't beleive me............
Capacitor esr is generally of minute importance....unless you are using really bad cap's..........
As for using low R coils and "real"resistors instead of lower cost coils, it does not matter.....if you need the series resitance, it might just as well be included in the coil.....providede you have control of the parameters i question...... saves you a few bucks too, with the cheaper coils.
As for modelling or simulating a filter, the series resistance of the inductors should absolutely be included in the sim's, and the load resistance of each element should be represented by a network as close to real as possible,- at least including the inductance and series resistance of each element.
Anyone doing sim's with inductors without series r and using constant R loads instead of real netowrks , are in for a huge surprise. Try both versions if you don't beleive me............
Capacitor esr is generally of minute importance....unless you are using really bad cap's..........
As for using low R coils and "real"resistors instead of lower cost coils, it does not matter.....if you need the series resitance, it might just as well be included in the coil.....providede you have control of the parameters i question...... saves you a few bucks too, with the cheaper coils.
Jay said:
I tried 12ga Goertz foils and Solen Hepta-Litz. For comparison, I ran the woofers full-range (no inductor). Full range provided the best bass, followed closely by the Solen. The Goertz made the bass sound fatter and slower. I didn't like it, but I suppose it could work in some situation. The Goertz also caused a mild sibilance in the woofer's high frequencies (crossover was about 4.3K).
I've found the foil type inductors preferable to round wire because their conductors are much more constrained/damped against any type of vibration externally or internally produced. However, the insulation dielectric performance is much more critical. I once yanked all the mylar insulated Solo foil inductors out of a speaker xover to replace them all with polypropylene insulated Goertz due to this.
AuroraB said:
I guess this series R is not a variable to be solved, but rather an input constant?
AuroraB said:
It's not uncommon that we heard somebody notice that putting capacitors in parallel will make the sound "unfocused". But I have many experiences where I can hear "better" sound when I series 2 capacitors. Initially I thought that it was probably because that was just the correct capacitance to be used, but after more experiences I started to think that there may be something in putting 2 caps in series (even for parallelling another cap). Does this have something to do with esr?
AuroraB said:
Kevinkr explained about the approach to use high DCR inductor, and also the use of hi-end inductors in series with small value resistor. That is correct. But I have to disagree if anyone "start" to think that they are equivalent, or there is "saving" importance in using high DCR inductor. Hi-end inductors are not good because of their low DCR, and cheap inductors are not bad because of their high DCR. Try putting a resistor in series with a woofer, it won't hurt the sound the way high DCR cheap inductors do.
Jay said:
My point was that series resistance should be included in any calculations or simulations. Particularly for larger inductors in LP sections, R is a real factor to be counted in, not overlooked.
It's not uncommon that we heard somebody notice that putting capacitors in parallel will make the sound "unfocused". But I have many experiences where I can hear "better" sound when I series 2 capacitors. Initially I thought that it was probably because that was just the correct capacitance to be used, but after more experiences I started to think that there may be something in putting 2 caps in series (even for parallelling another cap). Does this have something to do with esr?
Maybe a bit hastily of me, - but I was referring to parallell cap's. Series caps should indeed be looked at.. I am not sure though that esr is such an important factor on its own, however esr is linked to cap loss factor, although esr is usually only referred to for electrolytics and high value bipolars in an e.g. bass filter, - usually not for polyprops and the likes used in high end mid and treble filters. If two polyprops of half value in parallell sounds better than one single....of equal make.... well, that's another discussion.....
Yes- and no..... any resistor in series with a bass unit, - value being significant, of course, - should be audible, at least in the lower end, as it does modify the Q value and thus the response. My point was that if you need a series R, to modify the low end response, it might just as well be included in the coil. I seriously doubt that a low R coil with a series resistor, giving the same value as a cheaper coil with the same total R included, will sound significantly different, if at all, in the bass end of things.
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