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In Reply to: RE: sorry to hear that posted by Davey on March 09, 2008 at 08:23:47
Correct me if I'm wrong, but aren't the roles of the components reversed in a series XO? The cap limits the range for the mid/woofer and the coil limits what's sent to the tweeter. Thus, in relation to the highs, the series crossover is capless. Please enlighten me if I've mispoken here.
"Jazz is not dead - it just smells funny" FZ♬
Follow Ups:
It is a somewhat confusing design, but no, it's not correct to think of the passive component roles being reversed. The whole shunt-ing versus series-ing thing confuses the issue. Here's a pretty good explanation that popped up when I googled:
http://en.wikipedia.org/wiki/Audio_crossover#Series_crossovers
I've said this before and I'll reiterate here again. The reason the series-connected crossover advocated by PG works or doesn't work well (that's not really the point) is not because it's a series-connected network, it's because it creates a completely different set of curves than either the 1st or 2nd generation MMG stock crossovers.
Those same curves can be created by a parallel network, or an active network, or a DSP unit, or whatever. Also of note is that those sets of curves (series or parallel) create a much flatter system impedance than the stock MMG crossover would. This would interact with amplifiers which have a highish amplifier output impedance to further alter the relative differences between stock.
The baffle widening, the large crossover change, the hardwood frame for "dissipation", all factor together to form large change to the MMG design. I don't think it should be unexpected to note a large change in the sound of the system.
Regarding the Taz crossover: That truly is a "capacitor-less" crossover design. However, it comes at the expense of an insertion loss within the low-pass network. This crossover also alters the original MMG crossover curves significantly and accounts for the large difference in sound.
Cheers,
Dave.
"The HPF and LPF sections for the series crossover are interchanged with respect to the parallel crossover since they appear in shunt with the low & high frequency drivers." If that doesn't imply role revesal, what does?
The frequency balance of the stock XO frankly sucks, IMO. It's that 'in your face' high frequency blare that kept me from cranking my system. After the change (and yes, it's a dramatic change), I find myself turning up the volume and leaving it there. When properly underpinned by a pair of good subs, these heavily modified MMGs do everything better (to my ears).
There's no question that a parallel XO with the same values would create the same frequency balance. Since Maggies present a fairly flat impedance curve, the self-correcting benefit of a series design becomes a moot point. Likewise, one could easily duplicate the curves with either an active or passive line level XO. Those facts aren't in question. I'm only saying what everyone else who has listened to PG's modded speakers (as well as others who have done it themselves) has said - I love them!
As I stated, I've never heard the Taz XO so I cannot comment. I suppose it could easily be modeled, but that isn't listening, and you know very well that I'm one of those stupid listeners!
BTW, the baffles aren't significantly wider. PG can still get them in the Magnepan shipping boxes.
"Jazz is not dead - it just smells funny" FZ ♬
It's just a question of semantics I guess. It's not worth arguing about. Look closely at the diagram again and you will see that the capacitor is indeed in series with the tweeter.
The stock MMG crossover does not, in fact, present a fairly flat impedance curve. There's a bit of a hump created that doesn't exist with other alignments. The flatter impedance is created by the filter alignments themselves and not the configuration. It's really not a moot point.
"Self-correcting" is not a benefit of the series design. It can still be "un-corrected" pretty easily by a non-experienced designer. :) However, the interaction between filter slopes is "built-in" whereas all other configurations allow exclusive adjustments.
Whether or not everyone loves the sound of the PG modded speakers is beside the point. I don't know how many times I need to reiterate that. :)
Good fun.
Dave.
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