Quote:
Originally Posted by AleksanderSuave
Mike, curious about this subject, resurrecting the dead so to speak.
when you reference the OEM amp, is there a difference here between the Hifi AMP and the H/K amp? My reading in another thread was that the two were quite similar, so I assume no (minus the increased wattage to drive the larger # of speakers in HK), or does the OEM hifi amp not have built in cross-over function since the HIFI system doesnt run tweeters?
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Nearly all OEM systems in modern car audio have some sort of DSP - Digital Signal Processing - as part of its setup. A key element of that processing is pass filtering, so that certain speakers receive only certain frequencies. In these cases, such filtering is digital and cannot be removed except by two methods:
Option 1: The DSP unit itself is taken out of the audio system
Option 2: The DSP is overridden by so-called 'correcting' DSP units that are installed somewhere downstream from the OEM DSP.
Where the OEM DSP chip lives, and how it functions, is a key difference between the HiFi and HK systems.
- In the HiFi system it lives inside the amplifier unit, which can be bypassed because HiFi only uses a (barely) line-level analog signal from the head unit. So Option 1 above works.
- In the HK system, it also lives in the amp housing -- but that housing is also a MOST control box, part of the function of which is to convert the digital-only signals it receives from the head unit to multiple speaker-level analog signals, which are
only then subjected to DSP. But the MOST control box cannot be removed because it's intertwined with several other Infotainment systems. Only Option 2 is possible.
The problem with Option 2 in fiber-optic MOST systems is that the amplifier cannot be separated from the audio stream, so adding a 'corrective' DSP means it must take a speaker-level analog input -- which has already been converted from digital at least once -- correct the DSP, convert it to digital again, then re-convert it back to analog. We're talking at least four AD/DA conversions, which is a really, really bad idea for audio quality. The only solution is to override the MOST interface with another MOST device, which will endemically have its own user-adjustable DSP.
What does that mean regarding physical pass filtering for speakers? It makes them totally unnecessary in all cases except one: when the OEM amp is still being used but different speakers (with different frequency requirements / capabilities) are installed.
Hope this helps.