Originally Posted by JonasHansen
No more inputs?
It's a bad idea. There is no other input necessary. If you prefer to attempt it any way, have at it.
The troubling part here is the "how it sounds at 60 Hz" thing. Bass is bass. There is no 'sounds better' or 'sounds bad' at 60 Hz.
What we hear is frequency response. If the response is non-linear (not flat), then your perception will be influenced accordingly. In the case of the PB Ultra vs the JBL, unless you're using a much larger power plant to drive the JBL and pushing the Ultra past what it can give, there is no audible difference at 60 Hz. The Ultra gives less than 5% THD at 60 Hz at maximum long sine sweep, which is as good as it gets.
Personally, IMO, JBL gets the biggest pass of any product ever discussed on these boards. I don't buy any of their published specs and would love for someone to send one of these particle board boxes to Josh for the skinny on the "extremely low distortion" blurb.
If you want to claim a difference in SQ at 60 Hz between the JBL and the PB Ultra, you're gonna hafta attach some data to that claim. If you match the FR (filter the low end out of the Ultra with equivalent order filter) and match the level, there will be no difference in SQ at 60 Hz. If there is, one of them is adding something that doesn't belong, and we know from test results from Ilkka, Slarti and Josh that it isn't the PB Ultra.
On to the question posed, which is that of a 2-way subwoofer system. Any time you use a crossover, you have phase issues (GD) that affect FR. Can you post a FR before EQ smoothing, focussed on the crossover region of the 2 subs? What exactly is the crossover scheme (point, orders, method)?
It's really pretty basic: The LMS Ultra is a perfect example. In order to get more displacement (throw) from a driver, you need a longer voice coil. The longer voice coil means heavier moving mass, which lowers Fs. Perfect, just make the VC longer, right? When you do that the sensitivity drops and the top end rolls off from high inductance. No problem, just add more motor and sleeve the pole with copper. When you add motor, Qes drops. When you sleeve the pole with enough copper to flatten the top end, you need even more motor.
There you go; the LMS Ultra. Huuuuuge motor, low Fs, low Qes and 90dB sensitive. Oh, and a $1k price tag. The JBL evades the need for a massive copper sleeve by offering no displacement. Instead they have a little copper ring centered in the gap. The JBL keeps its sensitivity up by requiring far less motor, it has a high Fs and low Qes. So, why does the JBL cost as much as the LMS? You got me. Why is your JBL said to be tuned to 25 Hz when its drivers Fs is 35 Hz and its box volume is 8 cubes? Because it really isn't tuned to 25 Hz. What is its THD at 60 Hz with maximum slow sine sweep? I would love to know, but I bet a beer it ain't <5%.
So, if you'd care to post the complete picture, I'd be glad to check back into this thread and add my 2 cents, FWIW. From the LP, post the JBL alone, then the PB Ultra alone, then the combination of the 2, all of the above with no smoothing and no post smoothing EQ. Then list the details of the crossover you used for the experiment.