Marantz HD770 4 way Crossovers

Hi, if no-one near you volunteers, go to the nearest tv/radio repair shop with that pdf. It has all the component values and layout plan, piece of cake for a pro to make them!

Speaker layout is old-fashioned and far from optimal by today's standards, but xo looks pretty good, there is lots of knowhow behind it.
diyAudio Moderator
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Peterma, you don't say what your problem building them is. Is it finding parts, reading the schematic, soldering?

Some assume expensive. The coils beside the drivers are high resistance. This can mean cheap, even a spool of cheap thin hookup wire might do the job :p . The caps don't have to be polys, electrolytics can sound very good. The L-pads can be replaced with resistors.

What parts d you have lying around that might be useful.
Peter, where in Sydney are you?
I have some L pads you can have, but as Allen says, it's better to replace them with fixed resistors.
there's a couple of hundred dollars worth of parts in that crossover, even using cheap ones for the high resistance inductors. Good parts can be sourced from Speakerbug
Wind your own coils?

Perhaps we can assist in doing your own coils. I am positive that with help of a coil calculator, we can predict diameter and inductance within a couple of percent from the original value. If there were any issues finding right magnet wire for the higher dcr inductors, adding a resistor in series would solve it.

How much does awg 18 and awg 27 magnet wire cost in Australia?
diyAudio Moderator
Joined 2008
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Retail, that's 25ga and 19ga on the right, 57m and 14m in length.

I get quality double enameled unused magnet wire from a motor rewinder who sells me the ends of the spools for next to nothing because he doesn't like to use them.


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There is also the option of purchasing ready made cheap Chinese crossovers employing iron core inductors. Modifying these to meet the original marantz values would not be hard, some caps might fit also. The excess wire from one could be used to increase the inductance of another.
I have been sitting this 3 way thinking that I could modify the board for the 3 then just add one more for the last tweeter, do you think it would work?

Crossover 3 Way 12dB 500/4KHz
Z4/8ΩX24000HzWoofer4Ω / 8ΩX1500HzCrossover500Hz / 4.5KHzTweeter8Ω


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it could work assuming the necessary changes to the inductance/capacitance values were done. Before that, you need to get a hold of an LCR meter, either a dedicated one or a sound card based one. You could even rewire the board to suit the original schematic.