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Magnepan 1.7 dspNexus 2x8 DSP Crossover project

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HAL:
My nephew wants the Magnepan MG10/QR speakers system with the dspNexus and two 2x12 servo subs, so was looking for another pair of planars to replace them.

Found a pair of original Magnepan 1.7 speakers on FB Marketplace in the area for $100 for repair.  This was the first Magnepan speaker to use all quasi-ribbons for planar drivers when it came out.  One speaker has an open super tweeter quasi-ribbon.  Magnepan sells a repair kit for the aluminum foil quasi-ribbon speakers, so ordered a kit.  You purchase Acetone separately to remove the old glue to detach the quasi-ribbon material to install the new material for repair.
Will pick it up in MN since I am here to visit Danville Signal this week. 

Measured the correctly working speaker setup for measurement with the original passive crossover and here is the frequency response plot on center of the vertical tweeter axis. Once I have the second speaker repaired, will do a comparison frequency response plot.

This is a 3-way design with a woofer/mid planar, a tweeter planar and super tweeter planar.  The tweeter and super tweeter crossovers are connected in series.  My understanding is that the super tweeter is a 1 Ohm load.  This is perfect to try a current output power amp for that planar, instead of a voltage output amp. 
Amps like the Acoustat TNT200 and modern Hafler Transnova amps both designed by Jim Strickland are transconductance amps designed to drive electrostatic speakers.  These are highly capacitive loads that go to very low impedance at high frequencies.  Sounds like a good fit for this planar super tweeter.

This will add the Magenpan 1.7 to the dspNexus 2x8 upgrade library.

Nick B:
Rich,

Rebuilding those sounds like a fun project and a great deal too for your nephew 👍

Nick

S Clark:
????  Measured on the tweeter axis, and output from 250 to 1000 was significantly higher than higher ranges.  Just looks odd to me.   Also, was that 1 watt at 1 meter?  If so, that's going to take a lot of watts to drive it well.   

P.I.:

--- Quote from: S Clark on January 16, 2024, 11:29:38 AM ---????  Measured on the tweeter axis, and output from 250 to 1000 was significantly higher than higher ranges.  Just looks odd to me.   Also, was that 1 watt at 1 meter?  If so, that's going to take a lot of watts to drive it well.

--- End quote ---
There you have the reasons I've never been a fan.

HAL:
This is why Hi Rez DSP is a great way to correct the response of the Magnepan planars as the low end needs less power once correctly filtered than the high end due to the higher sensitivity and easy to correct when multi-amped.  You cannot do that passively as you loose to much sensitivity.  The mids and tweeter need much less power than the woofer with music content, so easier demands on the amp, so higher level drive is fine.

The MG10/QR's sounded much better with the DSP crossover than the passive original.  Lots of EQ in the crossover like the Magnetar planar speaker setup I had at Lone Star in Dallas in June.  Just wished I had built a switching box to swap between passive and DSP crossovers.  The differences were not subtle at all and much flatter on axis with DSP.

My '80s Maggie MGIIB's always needed help and now I could do it.  I know, as I just measured a pair of restored MGII's.

 



 

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