Originally Posted by artsci2
That's easy to explain. Looking at 50-100Hz range:
Four 88.6dB sensitivity drivers in series-paralell gives 94.6dB/watt.
The JBL 4642 is rated at 100dB
You need more than 3x the power to get the same SPL out of Quad Ultimax.
However down below the box tune frequency of the JBL the cone area and xMax of the um18 allows the quad's output to beat the JBL.
So you have a sweet "horses for courses" set up. Have you tried running the um18 lowpass ~40Hz and the JBL highpassed ~40?
Yep...I have sort of the best of both worlds right now when it comes to subs. But even level matched the sound quality difference between them is still noticeable on music especially with the JBL besting the UM's. Sealed, the UM's are no slouch in sound quality mind you but JBL knew what they were doing when they designed the venerable 2242 woofers all those years ago. One reason I'm so high on the JBL is that I actually use my theater a little more for music than movies...if it were the other way round I would be perfectly happy with just the UM's.
Originally Posted by RoboAVS
JBL is no doubt a top choice for a pro type sub. Many here are now pairing their UM18s with Dayton PA460s, which are a very cheap version of your JBLs...for exactly the same purpose.
The discussion goes exactly as you described....a high sensitivity lower mass lower excursion driver designed for pro use provides better tactile and pressure, while the high excursion high xmax higher mass drivers handle the low end and any tactle and pressure related to say under 40hz.
in my situation, i have tried separating the subwoofer ranges with a crossover, but i personally find that i prefer to blend them using them full ranges as i get more cones moving through the full range and have the benefits of all the subs spread out in different positions.
how did you choose to integrate yours?
Never tried cascading them...both subs are low-passed at 80hz with no other filters other than the 20hz hi-pass on the JBL. I used to run a BFD to eq my subs but pulled it awhile back and just let the pre/pro's room correction handle it for now.
My theater room is roughly 24'x22'x8.5'h with a small additional "L" shaped lobby/equipment rack space in one back corner so one side wall is closer to 30'. The 24' wall is my front/screen wall.
As to locating these two in the theater so they play nice together...I've tried corner loading, co-locating in corners and along the same walls etc. ,etc. I've found the "sweet spot" is having each sub located roughly mid-way down opposing side walls. Though not the best locals for ultimate spl(co-located corner placement), this mid-wall placement best smooths out the room response and improves the tactile "feel" at the main seat which trumps chasing maximum spl. Having these two in the same room is a luxury as worrying about adequate spl is really not an issue.
I also have at times run two additional JBL 4645(single 18's) for a total of 8-18's all at the same time. It was fun but really overkill so I have since moved the 4645's to a dedicated 2ch. setup.
If you can't tell, I really love the big JBL pro cinema gear. In addition to their subs, I also run the speakers in my avatar across the front. The center is semi custom to fit under my screen and I also use them as the side surrounds. I recently switched over to JBL 9300 on-walls for rear surrounds and I have a pair CT-321's waiting to go in the ceiling when I move to Atmos. I was fortunate to be able to buy most of my JBL gear used and at great prices from a nearby commercial theater supply dealer in Memphis. They thought i was a bit "nuts" putting all this stuff in my home.
Back years ago when i first started with the JBL pro cinema gear, I think only one or two other guys here on AVS were using similar pro gear. Now it's kinda caught on and is not quite as radical as it was when I started.
It's hard to argue with having the effortless full-range sound that these big speakers have...if you have the room and no waf to deal with that is.