Stock HPF on mach systems? How to disable it?

I have a 99' with the mach stereo system, and I believe there is some kind of built in high pass filter so no low frequencies go to the door speakers? I have an aftermarket headunit, amp and subwoofer. I left the RCA for the stock subwoofer/amp unplugged but there still seems to be no bass coming through the door speakers. How does the HPF work and how is it disabled? I am installing some pioneer speakers this weekend and I would like some sort of bass or midbass coming through them so there isn't such a big gap between the high frequencies and low frequencies of my sub. Or do the stock speakers in the mach system just not have the ability to have low frequencies play? Sorry for my ignorance on how it all works.

Thanks for any input

Just an fyi if anyones wondering, AFAIK, the HPF on my headunit isn't turned on unless it came with stock settings ON which I doubt.

The stock headunits are permanently designed like that. Especially the ones that had a factory subwoofer.
They don't send bass to the door speakers, only to the subwoofer.
At this point, an aftermarket deck is the solution..

DjDom said:

The stock headunits are permanently designed like that. Especially the ones that had a factory subwoofer.
They don't send bass to the door speakers, only to the subwoofer.
At this point, an aftermarket deck is the solution..

Click to expand...

I have a kenwood excelon kdc-x998, aftermarket subwoofer and amp. I left the stock subwoofer harness unplugged as well because I thought for some reason that may have been the reason no bass was coming through the door speakers. There's still no bass coming through the door speakers even with the aftermarket headunit, and to my knowledge a HPF isn't turned on but then again this headunit is way too complicated and non-user friendly so I guess I should look deeper into the settings.

I'm installing these pioneer ts-g6844r's this weekend (per your guys' recommendation ) and I'm just hoping some bass will come through them because there is a definite empty gap in certain frequencies right now and it doesn't sound good. Then again like I said I need to mess with the headunit settings more but there isn't an obvious HPF and LPF like my past headunits. Most of my past headunits would just have very easy options like setting the HPF at 60-80-100-120 HZ and LPF the same and below, this kenwood is confusing as #####