Magnepan MG 3.5 R crossover upgrade
Maggies are great to listen to however can perform a lot better with an upgraded crossover network.
The upgrade that we describe here is expensive but will really be worth it and upgrades your MG3.5/R to the ultimate dream speaker you always wished for and which performs at it’s absolute peak.
The kit available in our shop comes in two variations and in this build we use the best and least expensive one.
Read carefully and make excellent solder joints for good connections.
On the right you find the original two part crossover installed by the manufacturer. The high and mid parts are build into the panel and the low and mid section comes in a separate external box.
As always it is unbelievable that an expensive unit is equipped with a crossover like this. Parts with 10% tolerance, electrolytic capacitors, iron core coils and rubbish speaker terminals.
Very inexpensive parts are used that you would expect in a cheap loudspeaker system but not in a Magnepan, so we need to upgrade this to a level that should have been there in the first place.
To complete this project we will have to open the speaker panel to get to the internal crossover, remove or cut lose all the parts, rewire the connections to the panel, build the replacing (fully external) crossover and connect everything again.
In the original schematic we can find the components and values used in the crossover so we now can start selecting the parts that we like to have in our new crossover.
Our all tine favorites are Jantzen audio capacitors and coils and we will go for that.
12 AWG WAX coils, Crosscaps for the large values and Superior Z caps for the high panel.
Getting the exact values for the parts is not very important because Magnepan uses components with 10% tolerance and we will use 5% and in some cases even 2% tolerance parts in our new crossover.
First we will draw a new crossover schematic for the external panel, that will hold all crossover components, with the updates we have calculated and add the correct values and select the part numbers from Jantzen audio.
Note in the new schematic that we will leave the fuses in place. This will give some protection in case of unfortunate wrong connections between the crossover and the panel and will make the new wiring more easy.
Placing components is always a bit of a compromise. Preferably coils should be placed with opposing magnetic fields however short connections are more important in my opinion so priority is given to this in planning the components layout. Also we like to get the output connections in the best location.
The panel size we chosen is 36 x 32 cm and 12 mm thick plywood. To mount the coils we have used brass M5 threaded inserts with steel 40mm bolts and rings on top of and under the coils wooden core. The steal bolts will have a minute influence on the value of the coils and you could replace them with brass types if you like however the increase of the value is minute and will not have a any impact on the crossover points of the filter. Anyway it is the same on all coils so whatever makes you happy.
The finished crossover panel is shown on the right. Connection between components are made from two twisted 2.5 mm copper wires, you can simply use a battery powered drill to twist the cores together.