I'll for sure be going down the path of a new sub, but need time to sort it all out. For now, I've repaired the RCA's on the NHT amp, which worked splendidly. Problem is, it still has some mild crackling coming in from somewhere on the board, so when things are quiet, they are definitely noticeable.
If anyone is interested, I ran my test disk, which has a frequency sweep from 5Hz to 20kHz and also in interments among other things like bass tracks, drum tracks, vocal tracks, etc. I'm sure you all have them. This is an oldie from my first audiophile days. Anyway, The NHT does play the 5Hz, on up sweeps with things becoming very audible at 18 and super powerful at 20 on up. I guess no surprise there, so far as the audible part is concerned. Couldn't really feel the lower sweeps much, but they were there. The sweeps between sub and all other NHTs were super smooth and balanced. The Polk 505 definitely has low frequency blockers built in and there was no cone movement till about 18 with things becoming audible, but not with the power of the NHT at around 21. My test disc doesn't increment above 21, so couldn't quite nail down where the Polk really comes to life.
So the interesting point...to me anyway was how smooth the frequency sweep was across the NHT and how many drop outs there were on the 505. There are definitely missing frequencies. Now, I mentioned earlier that the 505 hit harder at the lower frequencies when watching movies. Now I'm not so sure! The wife and I were watching a movie on the NHT sub originally and things were fine. Not earth shattering, but we really weren't thinking of the sub much at all. Then the crackling started up with the NHT again and all of the quiet scenes were being impacted by the noise, so I switched to the 505. Here's the interesting part, I had volume matched the two when I was testing, so nothing changed, but vocals and general scenes just had something missing. Even my non-audiophile wife said, it's back to sounding like it was before, where things weren't balanced and tougher to hear!
We've had this issue for a while with the old Polks as well as the Klipsch Quinted. Having done the frequency incremental and sweep test with the 505, I now know there are missing frequencies in the sub toward the higher mid bass range, but wow what a difference. All these years I've thought it was something with the room and moved things around as much as I could. There was some improvement with some positions, but never quite right. I was suspecting my Onkyo receiver as the culprit, but now know it was the sub! I don't know, I wouldn't have thought it. Maybe there's some phase cancelation with the 505? I've tried the phase switch on the 505, but it never did much for the vocals.
Forgot how much fun it was to play around with audio, but never had sets of speakers or subs to experiment with. It was recommended I keep the 505 over the other two sub options, if I were to keep one, but that seems less of a choice now, given the few test I've ran. I'e already got a buyer for the Definitive, so that's on its way out. The 505 is now not an option either given the discoveries, so I'll likely put it up for sale as well. The NHT isn't worth anything at its current state, unless I can sort out the crackling, but between the first two at least, I should be close to getting a sub upgrade. For me, it's kind of a bummer about the NHT sub though. I'd really like to get it working. Something kinda cool about the old dinosaur. Seems to be begging to be brought back to life at least. NHT really did make a great sub for its time back then and the cabinet is really cool looking in it's gloss finish. Seems a shame not to at least get it working.
On a side note: I'm yet to notice a difference in power between the old 10" 80 watt relic and the 12" 300 watt 505. The NHT played down lower and never ran out of power on the tests, so...preaching to the choir here, but someone is fudging their numbers and power isn't everything! Looking at the 505 and knowing it has ripple the power of the NHT though, one would expect a lot more from the Polk.
I didn't have to prove this to myself again though. Back in the day when I was building custom sub boxes for cars, I would try my best to build the smallest and lowest powered sub, just for the extra wow factor of going against someone with twice or three times as much and getting better results. All things you all have heard before...but I'm new here! LOL!