Splitting a pre-amp channel for sub - good or bad?

Thanks guys, very helpful.

Al- very nice explanation, sounds like you've had a physics class or two before :)

Consider a sub crossover. Discontinued NHT X2's and Paradigm X-30's are getting hard to find. Bryston 10B Sub's are expensive. There's a European company called Reckhorn that makes something rather unusual, if it's available for US voltage.

Splitting is commonly done and typically does not degrade sound quality
Alan

In addition to my prior post, if adding a subwoofer to a preamp that even has a subwoofer output, with no impedance changes to play games with the signal, still can degrade the sound.

The bass from a sub could mask the midrange and highs easily. Even more so, if you don't set it up right. So do some serious comparisons with, and without it (during and after setup), to see if hear anything that can sound like it is taken away. This can be due to the sub possibly masking, or overpowering, the good part that you are hearing, in comparison to not using it. Other distortions from the added sub, or bass vibration in the room, can exist too.

These companies that make subwoofers, should use amps that are more versatile. Not everyone has a receiver with a subwoofer output. I've seen cheap under $200 subwoofers, with left and right line level inputs, and left and right speaker level inputs in the past. They could have the company that makes their amps (if they don't) supply this type of inputs. I think the speaker level inputs have a high enough input impedance, that the system may not know it's hooked up.

I have an older HSU, beside getting good reviews, it performed as promised. It went down close to the frequency specified,when tested. I don't know about their (HSU) newer ones made nowadays to say anything on promised specs. A lot of other companies promised to go down to a certain frequency, but fell about a full octave short. One was a JBL (I believe) that fell short by about 10 decibels (at -3 db, or -6 db) when tested. That's about an octave less than promised. I only use mine on occasion, to see if I'm missing anything on some new recordings I buy.

There doesn't seem to be many tests done on subwoofers. This lower priced HSU subwoofer has the type of inputs, that makes it easier to hookup. No specs for impedance that I can find though. This variation of hookup options, is a good selling feature in my opinion. It would be nice if the companies read these type of forums, and give their customers a product they could work with, a lot easier. It sure wouldn't hurt for some of these companies, to get more informed. Also, it wouldn't cost them much at all, for them to give these types of inputs, in my opinion.