Hi,

I have a 1992 LS 400 with a Nakimichi cd player in the trunk. When I turn up the radio all I hear is a lot of bass and treble with no midrange. I don't know if my power amp is the problem. Plase advise

 

Sounds like the stock speakers have blown. The rears tend to go first due to the heat exposure aiding to the deterioration to the speakers. You have to conduct a test to see if the speakers are blown. Remove the lining in the trunk and locate the speakers connections +/- disconnect and connect a small/cheap working speaker. I had little to no sound in my rear speakers, on my Sc and it turned out to be my speakers were shot/disintegrated from the heat exposure.
DIY steps for front speakers not sure if your model Ls400 has speakers on the rear doors or rear window area? This was the process on my '95 Sc it should be similar to your Ls400 process getting to the rear speakers area. http://us.lexusownersclub.com/forums...-sound-system/
DIY Ls400 Front Speakers
https://www.clublexus.com/forums/lex...ics-ls400.html
Speaker upgrades
https://www.clublexus.com/forums/lex...the-ls400.html

amp removal, if your amp is bad causing the problem
http://www.carstereohelp.com/stereor...sLS400str1.htm

 

Thanks very much!