I haven't been to Joe's site. I've Googled his name but came up with nothing, so if you have the address, much appreciate it if you can forward it.

I don't have any knowledge of the system where you experienced boredom with SS bass and PP highs. But most typical speakers are crossed at about 2.5KHz, therefore, virtually all midrange is coming from the woofer. In essence, most of the content you're listening to is produced by an SS system, which, for a tube guy like you, might explain the boredom. Using different amp types for different frequencies is actually more common than you think. Every time you connect a powered sub to a pair of main speakers, you're essentially bi-amping with different amp types.

In terms of the "limited-range" amps that I brought up, I not suggesting building an amp and purposely rolling off unwanted frequency. Rather, I'm questioning if it’s worth the extra effort and money to ensure fullrange performance if it's not used in that manner. For example, there are many "classic" tube amp designs that can be built very inexpensively. They give a wonderful lush midrange, but however, also have flabby bass and rolled off highs. If all you need is an amp to drive the midrange, intuitively, it makes sense to use one of these instead of doubling or tripling component costs for an amp that gives perfect square waves from 5Hz to 100KHz. Likewise, if an amp is only required to power a sub below 100Hz, a class D plate amp is acceptable. No need for a $5000 300w fullrange amp in that situation. But in the end, I don’t really know. This is just an approach that feels right and any feedback is welcomed.

Lastly, you’ve asked about the line-level passive crossover. It does look like a very simple and cost effective approach, doesn’t it? There are a bunch of guys on the net that swears, between active line-level, passive speaker level, and passive line-level, that the passive line-level is by far the best option. Never tried it myself though. I like to take advantage of the warm season by cramming in all the speaker projects I can. Electronic projects are reserved for the winter, and this PLLXO approach is definitely something I want to try out. I’m also taking two university level photography courses this semester, so time is tight. If you know the basics of SPICE and the input impedance of your amps, a PLLXO is not hard to design. The only drawback I hear is that you’re limited to 1st and 2nd orders, but it was never explained to me why?

Sorry if I wasn’t able to add much to your research, JR. However, from my side, I’m glad to hear there’s someone else out there asking the same questions. We’ll have to keep in touch to share progress.

Gar.