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In Reply to: MMG Crossover Upgrade (yeah, another one) posted by wazoo on December 7, 2006 at 18:04:14:
Whether or not the cost is worth the improvemt is up to you to judge. While some may cringe at the cost, NOBODY dislikes the improvement. On my MMG's, I first went with the 1st gen crossover topology and it was definately better. Snowball's chance in hell of going back. Later I changed to the MG12 crossover setup. This basically gives you the mids of the MG12, which is to say fantastic. If you can return your parts and get what you need to do the MG12 version, do it. The only regret you'll have is not having done it sooner.
Follow Ups:
Thank you for the suggestion. The only drawing of the MG12 schematic I've found doesn't appear to be authored by Magnepan. In your second upgrade, did you use a 2.8mH inductor (and of what design)? The higher capacitance is easily obtainable by paralleling additional caps. Also, did you use a low value bypass cap in the high end section (and, if so, have you tried the speaker without it)? Let's just say that I'm curious how a cap that operates so far beyond audible frequencies can really "clean up" the sound (kind of reminds me of Monster Cable's "directional" wires - folks, we ain't listening to DC). Hey, as I mentioned in my initial post, I could be "all wet"!
On my crossovers I went with a lower budget solution. I use Erse Super Q inductors (2.7mH) along with two Dayton metallized polypropylene capacitors (25uF ea.) per speaker. For the high pass section I used Jantzen CrossCaps (33uF) for the tweeters, bypassed at first with a Dayton film and foil polypropylene capacitors (.1uF). Later I upgraded the Dayton film & foil cap with a Theta AudioCap and found out why the Dayton bypass caps only costs a dollar. The high frequencies really cleared up with a better quality bypass cap in there.
The later MMG tweeters (8 run version) is essentially a MG12 tweeter. Take it from someone with a big SS amp and no fuses, they just sound better and better.Interestingly enough, I tried one of those directional Mon$ter cables and modded MMG's are revealing enough to let you hear a difference when you swap directions.
Thanks again for the additional information. It appears that you followed the schematic for the MG12 crossover that I found somewhere in these pages. What's ordered is ordered and I'll go with the original MMG configuration for the moment, but I'll keep a further upgrade in mind. For about $120 I can add a few more components to get to the MG12 crossover specs (inductors add in series; capacitors add in parallel), including nice, small value bypass capacitors. I may do the bypass cap first (after a few months) just to see what difference it makes - I am curious.After my MMGs are modded, I'll try reversing a set of the M850s to see if I can hear a difference. I admit that I haven't tried that, and I abide by their arrows, but it just seemed weird to me - electrons flow both ways with AC.
Erse Super Q inductors supposedly solve the most vexing problem with magnetic cores but they aren't that much less expensive than the Alpha Core foil coils (a design which has its own set of issues). Chokes are just bad things, but one can't build a crossover without them. I also considered sourcing my crossover upgrade from Parts Express, but Sonic Craft has much better pricing - nice folks too!
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