JBL electronic crossover mod

[Pellets]

Hi all, I recently acquired a JBL M553 electronic crossover which can be configured for stereo with three passbands. I then looked at the specs and found that the crossover frequency for the treble band is limited to 5 kHz. Now I have a pair of old Olympus S8R with triamplification but 5 kHz seems to be a bit too low a crossover point for the 075. Any of you out there attempted to modify the crossover points in the M553 lately? Or any other thoughts?Best regards

[Ian Mackenzie]

Hi all, I recently acquired a JBL M553 electronic crossover which can be configured for stereo with three passbands. I then looked at the specs and found that the crossover frequency for the treble band is limited to 5 kHz. Now I have a pair of old Olympus S8R with triamplification but 5 kHz seems to be a bit too low a crossover point for the 075. Any of you out there attempted to modify the crossover points in the M553 lately? Or any other thoughts?Best regards

Robert H may that know.

With the schematic is probably a change in parts values.

[Robh3606]

Robert H may that know.

With the schematic is probably a change in parts values.

No can't help with that. An alternative is make a change. My M553 bit the dust a year ago, intermittent loud hum.

I replaced it with DBX 234XS It can be configured with crossover points at 45-960 and 450-9.6k.

That will cover you. The only difference I noticed was a slight increase in noise at the speakers. Can't hear it at the listening position.

Purchase with a return option to try out. It is relatively inexpensive and you could sell the M553 to recoup some of the purchase price.

Rob


https://dbxpro.com/en-US/products/234xs#specifications

[grumpy]

looks like one could swap out .0032uF caps (8 of them) for .0018uF (1800pF) ... or put 4100pF in series with the 3200pF.
but that also wipes out the utility of the mono 4-way function, and hence potential resale value.
If none of that makes sense, needs further explanation, or not handy with a schematic and soldering iron (no shame in that)... just stop and get something that works as-is, per Rob's suggestion.
...maybe just do that anyway

[Pellets]

Thanks for your input! I managed to find the schematic for the M553 and indeed it seems that you can replace a number of caps with a lower value - it's already done in the mono leg. Maybe I´ll attempt to do it - this crossover wasn't expensive and it's a just a matter of dismantling the pc card from the box and desolder, not something for the faint hearted. The pc board is double sided. First I´ll check the availability of DBX units on the market here though...Best regards