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Magnepan 1.6 active 24db slop better than stock?

I'm bi- amping my magnepan 1.6's with Rane 22b,s.I have gobs of class A and triode power so that no problem.Do I go from my 22b's(to use gain control for each amps plus crossover for my subs) to my passive crossovers or bypass them and go 100% active Linkworth Riley 24db.If I do go active with 24db slope do I have to change polarity on my quasi tweeters.Can changing polarity(low to quasi)(and if I make a mistake)at any time one way or another hurt the speakers?Any opinions or expertize which way will sound better will be appreciated.
128x128swordshield
grege
47 posts
 
Sounds like a good plan Swordshield. Please report back your findings. That QR tweeter can go WAY lower than the standard passive xover, I think I went as low as 900 Hz with interesting results.
swordshield's avatar
swordshield OP
8 posts
 
I sure hope your wrong about freq.Manuel says 600Hz.Just got them going tonight,got the active set around 750Hz ,I thought for good measure to start out at.I want to retube my amps(just got amps- old tubes) before I make any conclusions.My mag .5's crossed over at 1000 Hz.I just set my 1.6 (active side) at 1000Hz [you freaked me out],were did you come up with this 900Hz.Manuel says exactly--- CROSSOVER SYSTEM Acoustical 600Hz, am I misinterpreting something here, is the word acoustical saying something I don't know.Don't want to fry them.Again (please) were did you get 900Hz?
eldartford
4,262 posts
 
The electrical crossover is 1600 (maybe 1500).

The accoustical crossover is where the woofer and tweeter SPLs are equal. If you have a spectrum analyser, connect the tweeter with inverted polarity and look for a deep notch in the frequency response.

The inverted polarity of the tweeter is correct for the stock tweeter crossover (12 dB). For a L/R 24 dB crossover normal polarity is correct. (Otherwise you get that deep notch).
magfan
1,583 posts
 
Stereophile test shows x-over freq to be 600hz.
Knee frequencies are +- about 100hz from that.
Hi pass is 6db oct consisting of caps ONLY
Lo pass? 12db per octave and includes an inductor.

http://www.stereophile.com/content/magnepan-magneplanar-mg16qr-loudspeaker-measurements

As kind of an aside, I think this accounts for the tweeter sounding better on the inside, being 90degrees out of phase with the bass part of the driver. The tweeter being a couple inches closer to the listener, straightens that out.
Also, please note that this is NOT a difficult load. Very flat impedance with only a peak at crossover while phase angles remain moderate. Low sensitivity? Sure, but this is a line source / dipole and will react to a room somewhat differently than a box with forward facing drivers of similar electrical measure.

Best of luck with your experiment. Please post some results when available.
eldartford
4,262 posts
 
Magfan... Yeah. I got ir backwards. It is the woofer that is 12 dB slope, and the tweeter 6 dB.

As to the crossover frequency, 1600 is what you get from calculations using the values of components in the crossover. The accoustic crossover includes mechanical characteristics of the drivers. No doubt that the accoustic frequency is what matters when listening to the stock speaker, but for designing a new crossover the electrical crossover is important.

By the way, I am a bit leary of driving any tweeter directly from a power amp. Power amps are apt to output nasty thumps.
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