JBL 550p external amplification modification

[Depoxy]

The plate amplifiers on both my JBL sub 550p subwoofers died, so I am converting them to external amplification with a speakon. I will be powering them using an nc502mp fed by a Minidsp SHD.

The 5110g drivers have a capacitor across the terminals, I’m assuming to function as a low pass filter. Does it make sense to remove the capacitor given that a filter could just be implemented in the dsp, or don’t bother?

I’m still learning about active speaker implementation and I am unsure if the capacitor will cause any issues with the amplifier, so I am curious to hear your thoughts on this. It seems most DIY subwoofers don’t have capacitors on the drivers.

 

[voodooless]

Do you have an idea about the value? This is indeed unusual. It might be something the amp needs to remain stable?

I would assume you don’t need this with a different amp. In fact, class d amps don’t generally like driving capacitive loads.

 

[Depoxy]

I don’t have the value, but I’ll remove it from the second sub and take a look at the value before gluing on the new back panel. I'll have to pull the driver from the first subwoofer as I already glued the back panel on. I'm not sure why it would be there as it had a class D plate amplifier to begin with, maybe a cheap way of taming a peak near the top of it's range that would probably be handled by a dsp amplifier if it were built now.

 

[bmc0]

Whatever its original purpose, it is more likely to cause problems than do anything useful with an external amp. Self-oscillating class D amps like the NCORE series don't tend to like heavy capacitive loads.

 

[Depoxy]

Thanks guys, I appreciate the feedback. I'll pull the drivers, remove the capacitors, and check for any other hidden resistors or inductors.

 

[Depoxy]

Well just in case someone comes across this in the future, I took the drivers out to investigate and it was just a 110uF 100V capacitor across the terminals. I removed them based on the feedback here regarding class D amplification.