room acoustic

[sma]

Hi,

I am install Vifa P13WH10-04 woofer+ Vifa D26NC tweeter at my car audio.I am use RTA for make the crossover and already get good cutting point at 3500 hz .the response already linear between woofer and tweeter.

The problem is at 1.25khz frequency is peak 3 db.
I think this is because car cabin acoustic.because when the microphone put front of the speaker,the response is okay,but when the microphone put at driver ear position the 1.25khz is peak.

Is somebody people know how i can reduce this frequency peak?I don't want use active equalizer since will reduce the sound quality.

so please advice me with other method.is possible use passive crossover additional schematic for reduce this 1.25 khz frequency?
or use acoustic way like difffusor for break this frequency boost.

Please advice.