Originally Posted by Eskimo1
A few things though:
How can you be sure that "flat" is truly flat? It's been shown that the non-nav radios have loudness and a vehicle (sedan/hatch) specific EQ applied when their 3 tone controls are "flat" Why would the NAV be any different? It's also quite obvious in listening to tones at various volumes that there is a "loudness" applied to some frequencies.
A sound-altering EQ (like a cleansweep or similar) is my LAST resort, but the idea in this build was to keep it SIMPLE. Adding that plus another amp, while keeping all that completely hidden is going to be a royal PITA, and unfortunately, changing the HU is absolutely NOT an option.
My point is - the Non-NAV guys can defeat the loudness setting and the factory EQ in a menu - why can't we?
It's as flat as that HU can get lol. There is a hidden menu for this head unit can be access by pressing the "Audio", "Voice" and "Map" at the same time. However there is not a single option for loudness nor any sort of eq option. I'm pretty sure it's just the crappy sound processor that unit has. Honestly there isn't much you can do without adding a DSP. Amplifier might have but it might still give you weird bass frequencies as well. But then I'm not a professional at this so someone else might be able to chime in.
Well you do have another option. Pay a subscription fee on Subaru Techical website so you'll have access to the Service manual for the new Fujitsu Ten Navigation HU and read through it to see if they have anything about any other hidden menu.
Me personally I will be adding a JBL MS-A1004 amplifer which has pretty good built in DSP. Average size amplifers should be easily hiddent under your seats or trunk. Honestly it's hard to expect "good" audio quality from factory. You'll have to add something to enhance them. Good luck whichever way you decide to go.