car subwoofer filter 48 db/octave

[adytzu22]

Hi could anyone please comment on the following circuit. Its an car subwoofer LP filter... tkx



http://static.diyaudio.com/forums/ga...a/1785/sch.png

[djk]

Too small to read.

[adytzu22]

try this one... tkx

[adytzu22]

any feedback wold be great ... tkx

[Moon Track]

First: I’m unsure you are really need in doubled buffer for output.
Second. There will be strong crosstalk in input cable because of the link between input capacitors.
Third: There’s no necessity to duplicate op-amps for direct and reversed signals.
It would be better to use one amp for mixer and next amp as inverter.
To switch phase it is enough to connect the filter input before or after inverter.
Fourth:
It is good practice, to minimize THD and to get maximal noise rejection ,to have direct and inverted inputs loaded by symmetrical current.
So, some of grounded inputs should contain resistors and some of resistors should be corrected.
For example:U7. The equivalent resistance at inverting input is paralleled R17||R18 -5kOhm, then to provide doubled current for U7 and U8 the R15 and R16 must be 5 kOhm too.

[adytzu22]

R15 & R16 ar a simulation of a 100K potentiometer because I couldn't find it in LTSpice... as for the input could you give me ani suggestion

is this better?

[adytzu22]

better?

[adytzu22]

any feedback wold be greatly appreciated ... tkx

[d1030180]

May I ask what is the purpose of resistors R1 and R4?

[adytzu22]

its just for simulating in LTSpice ... R1 and R4 are dummy-loads