Friends hi-fi system not very good, what do you do or say?

If I'm listening to the worst system I ever heard, and I'm asked about it, I'll reply:

"I've never heard anything like it in my life"

Hoping they don't want more detail.

The best thing you can do is to invite that friend to your house to listen to your system. Of course after you say something nice about his. Then play some music that he is familiar with and see his reaction. Offer advice only if asked for. Otherwise, don’t say anything. That same thing happened to me, except that I was the friend with the crappy system. 

If you’re friends and he doesn’t know you have the same hobby. Are you really friends? I hardly doubt it.

If I met someone and they try to hide the fact that they also have a dedicated system of their own, that would probably be my last invitation.

I also find your comment about the Lambo pretentious.

I own a relatively "nice system" myself, running electrostats but I also enjoy my $70 Moondrop aria earphone. If one loves audio, well... idk but not like this.

If you find my direct post offensive, I apologize in advance.

@hilroy48 

"I am an asshole that way, I don't mince words. I tell people what I think if they ask period. Not my fault if their feelings get hurt. Life's tough, wear a helmet."

Yes, I think you're right.

As they say. "Know thyself."

There is a number of good peer reviewed articles on giving constructive criticism from a human resource perspective on the internet.  The principles apply in all situations, not only the workplace.  Constructive criticism should not criticize but rather focus on some obtainable recommendations or suggestions on how to make improvements based on your experience.   Give constructive criticism between statements of praise.  For example, state it is obvious you put much work into equipment selection.  I have found room treatment can have a significant effect on SQ and you should consider this.  Use “I” phrases is suggestion (I… think, recommend, consider, etc.) rather than “you” commands (you…should do)..Provide examples from your experience.  Be empathetic.  Put yourself in their position and think about how you would want to hear the criticism and what specific words would be most helpful to you.  Express your passion and knowledge enthusiastically without being condescending.  Constructive criticism encourages someone to learn and grow.  Destructive criticism discourages someone and makes them feel inadequate.  Constructive criticism is specific and includes action plans. Destructive criticism is vague and confusing. Constructive criticism is delivered with empathy. Destructive criticism often includes harsh and confusing language.