JTR RS1s (18” sealed subs) vs JL Audio E112s, (JBL 4367)

Good for you using a full 2 way crossover. I would go a little higher if you can. 80 Hz would be perfect. It will lower distortion in the JBLs. Larger or multiple drivers of similar quality are always going to have less distortion because they do not have to move as far to produce the same volume. As drivers move farther the suspension becomes non linear and distortion increases. Another source of distortion is enclosure resonance and shaking. Turn the volume up and put your hand on the enclosure. Any vibration or shaking you feel is distortion. If you can feel it, it is clearly audible. This is a very difficult problem to solve and the only commercially available subs that do are the Magico Q series at ridiculous prices. I would never go larger than 18" drivers. As the cone gets larger it becomes harder to control and motion can become non pistonic, the cone starts flapping at volume. I use a total of eight 12" drivers. The main reason I use 12s is to keep the enclosure size reasonable. The enclosures are a custom balanced force design. They have a decagon cross section with 1.5" plywood walls. Plywood is stiffer than MDF, but much more expensive. There is no vibration or shaking. No enclosure resonance at all. You can see them on my system page. A photo diary of their construction will be available on Imgur. 

Digital crossovers are always better as long as the DACs are of good quality. The ones in the SHD are not, but the SHD Studio is the same unit without DACs. Benchmark Media Systems uses the SHD Studio with two of their own DACs with great success. I use a DEQX Pre 8. I cross at 100 Hz. A slope of 48 dB/oct keeps the subs out of the midrange. The key test is listening to the subs only with a male vocalist. If you can hear any vocal coming through the sub a higher slope is mandated. Always use the lowest slope you can get away with.   

m-db

The only built in frequency adjustment on the sub is a manual low effect control adjusted by a knob. It adjust the slope from 40hz-10hz by about 8dB and has a surprising large effect on the sound. Audioholics discusses it in their review linked below (has a graph of full cut and full boost). I believe the sub they reviewed is the older driver and the current RS1 come with a new driver from the RTJ (not a typo) 18Sub which Audioholics also reviewed. 
 

when JTR talk about DSP I assume they have a non adjustable filter in the amp that forces the sub to play lower/flatter but I don’t know. They are very short on information. The measured group delay is 10ms at 20hz and only 5ms above 40hz.  Where something like SVS SB16 with built in user adjustable filters has a group delay is 90ms at 20hz and about 10ms above 40hz. Some say this delay does not matter in the bass as the waves are so long but I would disagree. If you are time aligning then digitally no issue regardless but I am using simple analogue slopes.  
 

Mijostyn,

I have followed your system over the years and it has always looked impressive, I am sure it sounds amazing. 
 

SHD studio is an interesting idea. It would also allow for Dirac on the source side. 
 

I ordered a few more cards for the K235 and will try some higher crossover points soon. 

@james633 --

Finding the right way to implement your subs will be a trial and error process. Your JTR subs have a DSP section built in already, and your JBL 4367’s are passively configured. Have you tried running your mains full-range and then just blend in the JTR’s via their DSP with a bit of overlap to where JBL’s start rolling off? Yes, I know you won’t take advantage of high-passing the JBL’s, but introducing a less-than-stellar DSP on top of your passive JBL’s isn’t ideal either, as you’ve found out, and so I would simply start out by leaving your mains alone and concentrate on moving those JTR’s around to where they integrate the best with the smoothest response, and top it off with delay and volume adjustments. I’d be inclined to position the JTR’s as close to the JBL’s as possible, but it mayn’t be the best way to go about it all things considered.

If you want to consider high-passing the JBL’s you need a quality DSP. I use a Xilica DSP/digital crossover (now re-branded ACX, but other than that they’re the same product and built the same place) which is an excellent pro line product and fairly priced. Yes, it involves A/D to D/A conversion steps as there’s not digital input, but don’t worry about that. Trust me, it’s a great DSP and sonically transparent. The Xilica/ACX DSP’s offer a vast array of filter settings far beyond those found in most all-in-one subs, that only have the most rudimentary dittos.

If you want to go a substantial step further I’d replace your 4367’s with their pro oriented siblings, the JBL M2’s in active configuration via the recommend Crown iTech amps with built-in DSP. I’m assuming the Crown DSP will be able to high-pass the M2’s, and then add a pair of JBL SUB18’s with an additional external iTech amp and be done with it. I’m not familiar with the DSP section of those Crown amps, but I take it they offer fairly elaborate settings that will eclipse those offered by the JTR DSP.

With the combo of the M2’s, SUB18’s and a trio of Crown iTech’s you’d have yourself a fully active setup (i.e.: sans interfering passive crossovers) with quality outboard amps and DSP’s that would take the sound of your setup to the next level. You’d be able to juggle with crossover frequencies, delay etc. to best accommodate your needs in ways you couldn’t now, and not least looking at each speaker channel of main + sub as an integral part and not a pre-existing main speaker with passive crossovers where the sub of a different brand and driver type needs to be "latched" on with a different, built-in amp and so-so DSP. Don’t underestimate the importance of using the same amps from top to bottom - including the subs, which most never get to experience since most subs house built-in amps.

Yes, the latter option will be the most expensive route, but hey, sell your existing McIntosh amp, 4367’s, K235 crossover and other gear and have it part-finance your new endeavor :)

Lastly: if I'm not incorrect the DSP filter topology applied with the M2's through the iTech's is with 36dB/octave slopes, which is what I use myself in my fully active setup. Moreover, some M2 users EQ them down low to extend to close to 20Hz, but that design natively is tuned to not much lower than 35Hz and so this is asking quite a lot more of its 2216Nd woofer. By high-passing them instead at, say, 80Hz or more you're doing the exact opposite by adding substantial headroom and making for a cleaner, more effortless reproduction. Win-win. 

Phusis,

Thanks for the detailed thoughts.

yes I have tried rolling in subs under my mains at 37hz with my JL but not the JTR (internally their low pass stops at 60hz) and ran it that way for a month or so. It sounded fine but lack the impact on kick drums that highpassing brings. I am very happy with the current solution. I am sure it could be better by having the same exact driver/amp but I personally have not heard a better sub system as of now. I will try some higher crossovers not that I feel I need them but a few people who I respect have recommend them. Most of the time after messing around I end up back at 60hz.

Sadly crown amps are not the last word in fidelity and I think they hold the M2 back as I find them a little harsh. More or less Harman gives you a file to load into the crown amps with the needed PEQs and then you can adjust from there. The stock M2 filters are much different (much brighter) than the tuning of the 4367s. Erin’s audio corner has measurements of both if you’re interested. I would just end up filtering the M2 to match the 4367 as I like the built in “Harman curve”. The M2 replacement; the SCL-1 looks interesting. It has a passive network that can be 100% bypass to use active filters by the jumpers in the front. There is a silly deal on a pair “local” to me but I am pretty happy with the current setup.