My boat came with a Lowrance graph with the Active Imaging 3-in-1 Transducer and I used that for a couple weeks, but my Buddy had an extra Active Imaging HD transducer with the higher frequencies which is supposed to have better images, right? Well I have been using the HD and when I set it to use the higher frequencies I don’t get a better image, in fact I get a much darker image. I guess there is less “clutter” in the water column, but the images of the bottom seem much worse. Am I misunderstanding this? I thought the higher frequencies give better detail? When I turn the AIHD x-ducer to the lower frequencies it looks better, but still worse than the standard AI 3-in-1. Is it a bad transducer? 
 

For clarity I am running HDS Pro graphs and I have leveled the x-ducer to the angle while idling at appx 3mph. Nothing else changed, just the x-ducer. 
 

What am I missing? 

Yes, the higher frequency is supposed to give you a better image. I’m not familiar with Lowrance so maybe someone with your transducer could help you get started with some settings they use to help dial it in, or check YouTube. It’s possible the transducer is bad too (pictures would help) but I’d try adjusting your settings first.

Generally lower frequency uses a narrower beam for deeper water use. Anything under 60’ the standard frequency should be all you need.

Use manual settings to optimize your signal return.

Tom