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Planar Speaker Asylum Welcome! Need support, you got it. Or share your ideas and experiences. |
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In Reply to: RE: Are my ears really that sensitive? posted by JBen on September 12, 2014 at 00:03:48:
Cheers, yeah that's right. I'm not too technical with stuff like Davey and Satie are, but just like playing around, and you never know until you try is quite true with Maggies in my (reasonably limited) experience. Magnepan must do that to some degree too, - look at all the tension buttons in the 3.7 for example. I suspect some of that was done by trial and error.I find it useful and v interesting to have some solid technical input at times though, so many thanks for your sound input Davey, and thanks to Satie who in the past pretty much taught me all I know about crossovers etc. Didn't do that much physics at school (wish I had) but it's really great to learn a little bit to help with this hobby later in life!
The stock MGIII crossover was good (much better than the MGIIIa crossover IMO) but I had a bit of a suckout between 400-900 Hz, though the troublesome 1-2 Khz area was much improved. The bass was also a little too prominent. Will post the Anthem ARC FR graph of this setup I measured last night (average of 5 different microphone positions around the listening area).
To improve things Roger (who has experience and some simulation software) kindly suggested to increase the external HP caps to 60 uF, which decreases the midrange dip and the 1-2 KHz is still much better than the MGIIIa crossover (the latter had a considerably bigger peak). I used Neo's spreadsheet to run simulations too and saw the same thing.
I've increased the midrange caps from 35 uF to 45 uF and really like the result. Bass is less muddy and not as overbearing, and the suckout in the midrange is really improved. I tried 60 uF too and that was pretty good, but the bass was getting a little weak. I suppose that also adjusting the tweeter attenuation resistor would alter the balance as well so I need to try that too with these new different cap values.
I am not sure how Magnepan got the original MGIII to sound well balanced with 35uF of caps on the external HP (and it does sound excellent, from my memories of my Father's MGIII). With this exact same crossover setup put in the MGIIIas it clearly sounds too sucked out in the 400-900Hz region and that's very visible on both in room FR graphs, the electrical simulation, and what you hear (well, what I hear!). I have the original Magnepan Schematic for the MGIII which Karen kindly emailed me a few years ago. (I should probably submit it to the MUG page), and 35 uF caps is definitely what they used. Perhaps the bass or midrange drivers in the actual MGIII had different sensitivity?. Perhaps they used different gauge of aluminium wires altering the resistance of the drivers? Will check with Magnepan RE the wire gauge as I'd be interested to know.
So I think somewhere between 45-60 uF on the external HP will be optimal for my MGIIIa. No parallel inductor (as in MGIIIa spec) is needed so it now an all first order bandpass like the MGIII. If you look at the electrical simulation, introducing the parallel 3.5 mH HP inductor actually makes the FR more peaky!, - especially in the 1-2Khz region by around 2 dB! That makes the speaker sound way too forward and hard to listen to in my opinion.
Edits: 09/12/14
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- RE: Are my ears really that sensitive? - Davy 07:49:17 09/12/14 (0)
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