running engine and bass loss

I have Sony CDX-A250 with rear 6x9 speakers driven by 300Wamp. Every thing works fine unitl engine is turned off and system is running from battrey. Although battery is little weak but works well to drive audio system.

The problem arises whenever i start my car and drive, i can feel significant bass loss. I can't say it's completely gone but it doesn't feel solid bass as it feels when engine  was turned off.

there is no alternator whine or any other distortion. Tell me if it is really a problem ?

Is there an outboard amplifier on the system? 

If it was not a problem, would you have posted the question.  My bet is "it is a problem"  At least a problem to you.   If I help you fix your problem, will you tell us where he is?

it is a great problem for me,

Yes there is. It is a 3 way channel amplifier. it was working with no problems at all with previous headunit.

Are there any speakers connected to the radio's speaker wires?  Is it possible that the amp is not working when the engine is running? 

There are some amplifiers that will not work if they have too much voltage on the remote turn on wire.  Your other radio may have not had as much voltage going to the amp's remote terminal.  If the amp seems to not be working when the engine is running, using a volt meter, I need to know the voltage on the remote terminal, first with engine off and then with engine running.

Do You know where he is?

[QUOTE=i am an idiot]  If I help you fix your problem, will you tell us where he is?[/QUOTE]

I'm tryin my best to understand this..... with no luck.

AHHH Ha.... google is MY friend too!

idiot, you are a twisted individual..... I like that!

Have a GREAT day........

Thats cold..... funny but cold...

I noticed his location.  The military can't find him, I figured I would ask.

Was not meant to be cold at all.