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I read about a X-over mod for Maggie MMG's over at MUG that uses a resistor and an inductor, but no cap. It stated that this has a better sound than the x-over circuits using caps. Is this something that can be used on other speakers as well or is it applicable to just Maggie's?
I have some vintage Infinity Qa's and would like to use this type of crossover on the E.M.I.T. tweeters if it would work.
Follow Ups:
I posted this a while back on the MUG forum to explain the mod posted in the tweaks section regarding the lone shunt on the MMG tweeter. I would ONLY do this mod if the tweeter fuse was intact and Jon explained almost exactly what I was saying in more depth below. I'd take this one with caution.
This type of crossover has limited application, due to it's inherent problems with power handling and it's usage requirements.It is implemented via a series resistor, and then a shunt coil across the tweeter.
Here are the requirements t make it operate correctly:
1. The tweeter MUST have a higher sensitivity than the woofer, and as a minimum, by about approx. 4-6 dB.
2. The coil must have a VERY low DCR, in order to provide maximum protection to the tweeter.
3. The tweeter must be a wide bandwidth unit, with a low resonanht frequency, and decent excursion capability.
Reasons:
RE 1, the series resistor is all that provides a decent load for the amp, as the coil is a dead short to the amp in the low frequencies. Thus, this resistor should not be any lower than approx. 3-4 ohms, or the amp will see a difficult load all through the bass and midrange.
With an 8 ohm tweeter, this sets a minimum amount of attenuation that will occur, and so, the tweeter output needs to start out greater than the woofer's, just to stay even.RE 2, the DCR of the coil sets the platuea where the 6 dB/oct roll-off QUITS. In other words, if the coil has a DCR of 0.08 ohms, adn the series resistor is 8 ohms, and the tweeter is 8 ohms, then the platuea will occur at approx. -40 dB, and the tweeter roll-off WILL NOT CONTINUE BELOW THAT POINT.
Re 3, as can be seen from 1 and 2, the tweeter will be seeing a lot of LF energy, and the amount of padding is not that great, and the mild 6 dB/Oct LF roll-off WILL reach a platuea at some point, so the tweter must have the ability to handle the excursions it will be faced with.
Personally, I don't think this kind of crossover is a panacea, as there is still a resistor in series with the signal, and the shunt coil quality has a very large effect on the sound, and inductors ARE NOT perfect, even compared to caps.
I recommend that any one considering the use of such a circuit, also use a conjugate (series LCR hung across the tweeter) across the tweeter to help with it's resonance, this will help some with power handling, and with reducing IM, but not that much.
Jon Risch
Acoustic Reality has written about a Cap-less XO earlier.
I have tried, and it works. Great sound. But this was in "normal" dynamic speakers. ScanSpeak drivers.
It is true as John Risch says. The Ar-Sxo has it's issues, but If get it right, it sounds very good.
I tried it a couple of years ago using it with a 3 way setup. Using "normal" ar-sxo for the tweeter/mid, and a second order parallell for the woofer. It sounded in fact very good, but it wasn't an easy load for the amp. Reason: I tried it in a d'appolito setup. 1 tweeter, 2 mids (in parallell) and therefore the power resistor I used in series with the tweeter was in fact a bit low value.
sounds like the series xover that Kimber uses. It's proprietary but probably ok for personal use. It's hard to hide a design that simple.
It uses the parts you mention in a series configuration but you would have to figure out the values needed. It's a very dynamic design but it requires very wide bandwidth drivers(both frequency and power handling) because it is a very slow slope design.
nt
I don't remember who did it, maybe JohnK over at the mad board. This was one of the more interesting threads last year over there. It started with how series crossovers worked and then migrated into a minimum component experiment. I think he posted the results on his site. The bottom line was that he did get good signal measurements but the tweeter kept blowing up under normal conditions. So it was interesting but did not work in the practical world.Now if this relates to the MMG is different. I don't know those speakers, but if they are membrane then they probably have a transformer, if they have a transformer, then the XO science might be very different.
NO transformer.I did the mod on the MMGS, and it signifcantly improved the speakers.
I have had no problems with the tweeter or any thing at all since I did the mod. So at least in my system with my MMGs, it does work in the real world.
Here is the link:
Maybe I'll try it on something more "expendable" than my EMIT's. How do you calculate what value components to use?
I don't know. The values were already calculated from the link. You could possibly contact the inmate Tazzmon I think he is still around.Good luck..it will be worth the effort!!
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