Maggie 3.7 Crossover Revealed?

sparky62 · « **on:** 5 Feb 2015, 03:18 am »

I just posted this elsewhere. I just found this today and thought maybe someone would want to take a crack at solving the Maggie 3.7 crossover mystery...

Original OEM Magnepan Magneplanar 3.7 Passive Crossover Network Pair
http://www.ebay.com/itm/221675927291?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Springy · « **Reply #1 on:** 10 Feb 2015, 04:15 pm »

I see they are now listed on CAM. I guess the $1.50 bids on eBay didn't cut it? The caps are easily worth his asking price alone. I'd love to have a look at the schematic in more detail since it looks eerily similar to the MG 3.6/R crossover.

http://www.canuckaudiomart.com/details/649177076-magnepan-37-oem-passive-crossover-network-pair-with-schematic-crossover-frequencies-amp-roll-off-rat/

*Scotty* · « **Reply #2 on:** 10 Feb 2015, 04:33 pm »

The schematic shows a 1st. order series network assuming that the person who drew the network understood the crossover parts arrangement they saw.
Scotty

a.wayne · « **Reply #3 on:** 10 Feb 2015, 04:34 pm »

Dynamic limiting laminate on the bass, Nooooice ................

*Scotty* · « **Reply #4 on:** 10 Feb 2015, 04:56 pm »

They are after all, smaller and cheaper than 10 or 12ga. air-cores.
Scotty

a.wayne · « **Reply #5 on:** 10 Feb 2015, 05:01 pm »

Yep , Have you seen the price of Beef lately , something has to give ......

Springy · « **Reply #6 on:** 13 Feb 2015, 08:45 pm »

Quote from: a.wayne on 10 Feb 2015, 04:34 pm

Dynamic limiting laminate on the bass, Nooooice ................

That's probably why he upgraded to new xovers.

Davey · « **Reply #7 on:** 14 Feb 2015, 03:54 am »

Even the larger one doesn't appear to have too many turns/layers on the core. I estimate these are probably fairly small value inductors, probably around 1-1.5mH, because of the series configuration.

These steel laminate inductors have pretty good characteristics and saturation/distortion issues are highly unlikely in this instance. Way more distortion and dynamic issues in the drivers themselves than the crossover components.

Dave.

SteveFord · « **Reply #8 on:** 14 Feb 2015, 11:41 am »

So the pics don't vanish

a.wayne · « **Reply #9 on:** 14 Feb 2015, 12:09 pm »

Quote from: Davey on 14 Feb 2015, 03:54 am

Even the larger one doesn't appear to have too many turns/layers on the core. I estimate these are probably fairly small value inductors, probably around 1-1.5mH, because of the series configuration.

These steel laminate inductors have pretty good characteristics and saturation/distortion issues are highly unlikely in this instance. Way more distortion and dynamic issues in the drivers themselves than the crossover components.

Dave.

There are pretty linear vs aircore , but saturation distortion will exist in the bass that i can assure you, especially because of the low sensitivity .....,

Davey · « **Reply #10 on:** 14 Feb 2015, 12:45 pm »

Ah, well if you can assure me, then I must be wrong.
An equivalent air-core inductor could be made to fit in that area and hardly much more $$ so it seems Magnepan made a poor trade-off decision in this case?

Dave.

a.wayne · « **Reply #11 on:** 14 Feb 2015, 01:08 pm »

Do you think its difficult to drive more than 150 watts of music power into a 3.7 , really not , that inductor will saturate and it's not as simply as replacing values, ribbons and planers are very sensitive to DCR , you may want to watch for that too ...

Davey · « **Reply #12 on:** 14 Feb 2015, 01:41 pm »

Ribbons and planars are no more sensitive to DCR than any other 4 ohm driver.
DCR difference for equivalent inductors of this value only about 0.1 ohms. SPL difference only about 0.2db. Negligible.

Dave.

*Scotty* · « **Reply #13 on:** 14 Feb 2015, 02:34 pm »

I find the iron cored inductors objectionable because of their hysteresis distortion which aircore inductors don't have. This is definitely an economic trade off due to the cost of copper.
Scotty

Davey · « **Reply #14 on:** 14 Feb 2015, 02:39 pm »

These inductors were chosen for the Magnepan models for one reason and one reason only.

Dave.

a.wayne · « **Reply #15 on:** 14 Feb 2015, 03:36 pm »

Quote from: Davey on 14 Feb 2015, 01:41 pm

Ribbons and planars are no more sensitive to DCR than any other 4 ohm driver.
DCR difference for equivalent inductors of this value only about 0.1 ohms. SPL difference only about 0.2db. Negligible.

Dave.

Really, you must have built a few , thanks for the tip .........

Davey · « **Reply #16 on:** 14 Feb 2015, 03:43 pm »

If you disagree with my calculation on relative db difference please speak up.

If you're speaking about subjective evaluation "sensitivity" then I can't argue with you on that.

Dave.

a.wayne · « **Reply #17 on:** 14 Feb 2015, 03:51 pm »

Quote from: Davey on 14 Feb 2015, 03:43 pm

If you disagree with my calculation on relative db difference please speak up.

If you're speaking about subjective evaluation "sensitivity" then I can't argue with you on that.

Dave.

Yes i do disagree ,about not being sensitive to DCR and inductance , my LMS mic disagree, my subjective sensitivity listening disagree and their low BL factor disagree ...

Experimenting is a good part of the hobby , so i strongly recommend to go ahead, you may subjectively like it ....

Davey · « **Reply #18 on:** 14 Feb 2015, 03:54 pm »

Since you disagree, please correct my arithmetic on the relative db calculation then.

Dave.

a.wayne · « **Reply #19 on:** 14 Feb 2015, 03:56 pm »

Quote from: Davey on 14 Feb 2015, 03:54 pm

Since you disagree, please correct my arithmetic on the relative db calculation then.

Dave.

How can i correct your assumption about them not being sensitive to DCR, i did not challenge the math, have you measured the dcr.... ? have you measured at all ..? did you look at the TF...?