Upgrade from Pass Labs XA30.8 to X250.8. Worth it?

I thought I would follow up to give some closure to anyone reading this down the line. I always like to hear how people’s decisions turned out. Hopefully you do too. 

I purchased the Tekton Double Impacts, largely due to the advice I got from members here. While I am not ruling out an amplifier upgrade at some point in the future, I think the Double Impacts have had a more significant impact on my system, than an amp upgrade would have. 

The Tekton Double Impacts: 

The DI’s need some time to break-in. When I actually got my pair, I was surprised to hear they sounded “OK.” And by “OK,” I mean thoroughly OK, middle of the road, mediocre, and most of all: disappointing. But, it didn’t take long for the midrange to start opening up. The mid and upper range only took about 3-4 days to open up and sound wonderful. The bass, was a little different. 

I’ve been using an SVS SB16 subwoofer for a little over a year. When I started using the Tekton’s, it seemed apparent to me that the sound was improved with the SVS. A little over 30 days after getting my Tektons set-up, the bass seemed to change. All of a sudden, there was too much bass. I turned my sub down. A couple of days later, it seemed like too much again. This time I turned the subwoofer off. I eventually achieved the best integration with the SVS by crossing over at around 35-40 Hz. My RTA app on my phone says I had a relatively flat response down to 20 Hz. 

I remembered an email conversation I had with Victor Khomenko a while back. The VK-51se has two sets of balanced outputs on the back. I had asked VK if they could both be used at the same time. He said they could, but I had to be aware of the combined impedance of all the amplifiers attached to the VK-51se. 

My Pass Labs XA30.8 is relatively easy for my preamp to drive. The balanced input impedance is 100K Ohm. The SVS SB-16 on the other hand, is not as friendly; its balanced input impedance is 22K Ohm. I believe the combined impedance is found through the calculation (100 X 22)/(100 + 22) = 18K Ohm (I would appreciate if someone with some actual EE knowhow would fact-check me here).

As an experiment, I removed my SVS SB16 subwoofer from the system entirely. In my system, the DI’s start rolling off at about 40 Hz, so I lost some bass extension from the removal of the SVS. But what I gained was more drive and authority from the DI’s, and more color and clarity through the entire range. 

I don’t believe that I noticed this with my old speakers because they simply lacked the clarity of the DI’s, and did not have the same bass extension. With the old-speakers, the SVS simply improved the overall quality of the system. With the DI’s, there is a clear trade-off. Bass extension for overall sound quality (especially bass quality).

I have had my SVS completely unhooked from the system for about 2 weeks now. After about 1 week, I added it back to the system and found I disliked how simply hooking it up to the preamp affected the system. I quickly removed it from the system again. This has been an unanticipated side effect of adding the DI’s to the system, and has all but de-railed my plans for a second SVS-SB16 subwoofer. 

If anyone has some clever tricks for getting around this problem, I am all ears! 

@bobheinatz I think you were right ;-)