First, the SMS-1 is a great device for helping to optimize subwoofer placement in the room prior to any EQ or calibration. To use it for this, just turn off the speakers and play only the sub. Disable all EQ in the SMS-1 and set everything else to baseline. Then place the mic at the primary LP and move the subwoofer around room while watching the FR on the OSD. Place the sub in the spot that measures the flattest without any EQ. This will make it much easier to EQ the system later, as you will need less cuts or boost to get a perfectly flat response.
Second, when setting levels, there are 4 different level settings that need to be accounted for:
1. Master Volume Control
2. Subwoofer and Speaker Trims
3. SMS-1 Level
4. Subwoofer Level
These will all interact and they all need to be taken into account prior to doing any calibrations or EQ. To set the levels, and then EQ the system with the SMS-1, I suggest the following progression:
1. Start by setting all trims in the receiver to 0. (We'll come back later and re-set these for calibration purposes, but for now, set them to 0.)
2. Set ALL speakers to Small AND all crossover frequencies to 80 Hz.
The SMS-1 expects the use of Bass Management, which is what you engage when you set the speakers to Small. Therefore, to get proper results from the SMS-1, you need to set the speakers to "Small" and engage BM.
The SMS-1 can *only* EQ the subwoofer channel. It can NOT EQ the speakers. This is very important to realize. Any filters set above the crossover point will have little effect on the subwoofer output and minimal effect on the overall response. Limiting the range of the subwoofer channel by using a low crossover point, limits the range available for the SMS-1 to EQ. IOW, if you set a 60 Hz crossover, the SMS-1's EQ will only be effective to 60 Hz. Therefore, set the crossover as high as possible without localization of the subwoofer, which is almost always 80 Hz.
Page 42 of your manual, (see below), describes the Bass Management scenarios for your receiver. You can either use a "global" crossover for all "Small" speakers and the sub, or your receiver allows for different crossover frequency settings for the subwoofer and the speakers. The subwoofer crossover is really just an LPF, whereas the global crossover is an LPF and an HPF at the same frequency. IMO, you should use the same frequency for the HPF on the speakers and the LPF on the sub. Therefore, I recommend you use the global crossover setting of 80 Hz, for all speakers and the subwoofer. Also, set the "Stereo" mode to "Speakers = Small". This will engage Bass Management for 2-channel sources and make your subwoofer active for 2-channel content. This is *very* important for optimal EQ with the SMS-1, as described below.
The Phase Control on the SMS-1 is centered at 80 Hz. While it is better to use the receiver's distance setting to effect the response around the crossover point, if you do want to use the SMS-1's Phase Control, it will only be effective with an 80 Hz crossover.
3. Next, on the SMS-1, select Preset: Setup and set all EQ bands to 0. (A default reset is the easiest way to do this. See Page 41 of the SMS-1 User Manual, linked below.)
4. Set the SMS-1 Level to +15.
This is the setting for "Unity Gain" in the SMS-1. The SMS-1 is not an amplifier. You don't want to use the SMS-1 to add gain to the signal. You want it to add or reduce the gain of various frequencies *relative* to the average level, but you don't want it to increase the overall average level. "Unity Gain" means that there is no gain across the device, and the output signal is the same level as the input signal.)
5. Set the Subwoofer Gain Level at it's lowest setting. (We'll turn it up later.)
6. Turn on the left front speaker test tone. Adjust the receiver's MVC so the left front speaker reads 75 dB* at the primary LP. This MVC setting will be the "Reference Level" setting from this point forward.** Remember it.
7. Without changing the MVC setting, shut off the left front speaker and turn on the subwoofer test tone. Turn up the gain on the subwoofer until the SPL meter at the primary LP reads 75 dB. The SMS-1 should also read an "average" level of about 75 dB. (Once you've set this, you should never need to adjust the subwoofer's gain setting again, unless you move the sub.)
8. Now, go back and calibrate all of the speakers to 75 dB at the primary LP. Use the receiver's trim controls as described on Page 43 & 44 of the manual. Once you've done this, your system is fully calibrated for levels, and all of the settings are optimized in each device.
9. Proceed with manual EQ with the SMS-1. Put the receiver into "Stereo" mode. EQ the sub in isolation, (with the speakers off or disconnected), getting it as flat as possible up to the rolloff point of the speaker/subwoofer crossover you set in the receiver.
(Remember that in Step 2 above, we set the "Stereo" output to engage Bass Management. Even though the speakers are off here, the bass from the L/R channels will still be re-directed to the sub.)
(Remember also that any slider bands set above the crossover point will be wasted, so move them all over into the range below the crossover point.)
10. Once the subwoofer is EQ'd, turn the subwoofer test tone back on and reset the level to 75 dB. However, this time use the SMS-1's level control to adjust the volume to 75 dB. This will reset the SMS-1 for exact Unity Gain.
11. Finally, turn the speakers back on and evaluate the response around crossover point. Adjust the subwoofer distance setting in the receiver to optimize the response around the crossover point.
12. Re-check the full system calibration to ensure all speakers and the sub are at 75 dB.
Once you've done the entire process above, you'll have a fully calibrated system with optimized frequency response of the subwoofer. I suggest you try to live with that system for a few days or weeks. Some people are so used to a bloated or "hot" subwoofer level that they feel the bass is "missing" with a true "calibrated" and Eq'd level. Nonetheless, once they re-acclimate themselves to "flat" bass response, they begin to hear detail and articulation in the bass that was previously overwhelmed by bass bloat and boom.
Having said that, some people just don't "like" a flat FR of the subwoofer, and they prefer a rising LF response. There is nothing wrong with that, and everyone is allowed their own preference. If you're one of those people, you have a few options. The first option is to just raise the MVC. This will raise the overall system output, but you should also get closer to the bass response you are looking for. (This also assumes that the rest of your system is up to the task. If it's not, don't try to get bass response at the expense of your speakers! )
If that is still not enough, and you want to raise the subwoofer's output above the rest of the system, I suggest you initiate the Submersive's DSP Program 2. This adds a rise in the response below about 40 Hz, with 3 dB added at about 20 Hz. This should add the feel and kick you are looking for. You can view the effect of Program 2 by watching the response on the SMS-1. It should look like a rising response above about 40 Hz.
If that's *still* not enough, the third option is to raise the SMS-1's level. This will take you above "Unity Gain" on the SMS-1, but *judicious* use of the control should not be problematic. 3 to 6 dB of level increase should be taken in stride by the Submersive.
If the above suggestions don't get you were you want to be, then the only hope for you is another Submersive or 2 or 3.
Footnotes from #6 above:
*The Rotel uses -30 dBFS for it's test tones, so the test tones should read 75 dB on the SPL meter, ("Slow" setting and C-weighting.)
**The Rotel appears to be a "relative" MVC, (it goes from 0, (Off), to positive numbers), as opposed to an "absolute" MVC, which sets Reference Level at 0, and negative level settings indicate the dB below Reference Level.