[Otto]

tomtuttle wrote:

I am a serial lurker

Well, Tom, welcome to the Shack!

1. My Denon has a fixed crossover at 80Hz. I am using the auxiliary input on the front, and processing as Stereo with bass/treble flat. OK so far?

Yep

2. I don't understand whether I should be using a 12db or 24db per octave slope.

The crossover slope in REW becomes the target, so it should be aligned with your receiver's crossover. This might be spec'd in the user's manual. Most likely, it's a 4th order slope, which corresponds to 24 dB/octave.

3. My understanding is that I should NOT consider doing any meaningful measurements or filtering "full range" (understood to mean above the crossover point?) without getting a better microphone. Is this correct?

Yeah, that, and the fact that the BFD might not be the best device to insert into your mains path. I haven't done it myself, but I understand that it can be grainy or noisy. Generally, higher frequency response problems are handled with room treatments.

4. My understanding is that - when calibrating the subwoofer - I should have the mains disengaged. Correct?

Yep.

5. If #3 and #4 are "yes", how do I analyze the integration of the sub with the mains? Prior to starting the REW/BFD process, I had found that I sounds better to me to run the mains as "large". It seems like I'd either have to run measurements WITH them or run them as small.

The frequencies at the integration point are still considered low. The mic on your SPL meter will be fine for that. Indeed, I think the RS SPL meter starts to get kinda flaky over a few kilohertz, so you're well under that. We're mostly interested in the 10 Hz to 200 Hz range.

If you decide that you like them "large" and with a sub, that's OK. I have been known to run things that way myself. In that case, I will measure the system as a whole, meaning mains on. This does fly in the face of my previous comment to turn off the mains, but this becomes a different situation. In this case, we know that the crossover is not going to be applied to the mains, and therefore the integration between mains and sub won't be as "neat." Also, since REW can't tell that the mains are on, it will not be accurate in its filter assignments when trying to control what it thinks is your sub only. Therefore, you have to start tweaking the BFD filters by hand. Run a sweep, see where your peaks are, assign filters that seem reasonable, repeat. Keep in mind that since your filters are not affecting your mains, they may not have as large an impact as REW might indicate. It is an iterative process, but one I enjoy and have done a few times. If you have the MIDI connection between PC and BFD set up, the downloading of filters becomes trivial. Of course, it's also possible to enter them by hand, and I've done that as well, especially for a tweak just here and there.

6. I did some preliminary measurements yesterday from 20-200Hz (which was Fascinating and Amazing!) using both the sub and the mains. I discovered some really cool stuff about my room and phase adjustments. I also noticed pretty giant suckouts at about 90Hz and 190Hz. Is it *possible* that those anomalies are a result of either my method or my equipment? i.e. is there a known problem with the RS meter approaching 200Hz?

I don't know of any issues with the RS meter in that area.

Can you adjust the phase of the sub, even if only to fully reverse it (a 180 degree change)? That may affect your issue around 90 Hz, since your crossover point is 80 Hz. Also, you will notice these things change as you move your sub around the room, so you might try that, if only for experimentation's sake.

7. When I powered up my BFD (while holding the magic button) the display read "1.0". I think this means I got lucky and the BIOS version - while old - will accept MIDI input without eprom modification. I got the unit used from a good seller on Ebay, so it seems possible that it's not the 1.3 load. Yes?

Right. I also have a non-1.3 version, and the MIDI works fine for me. I think mine is 1.1, but I'm not there at the moment.

I've tried hard to find my answers in the top-notch written materials already available, and I apologize if my research was substandard. At a certain point, it is not only efficient but also fun to engage other people in conversation about your passions rather than pursue them independently.

Thank you so much for your tutelage and counsel. I look forward to being a more involved member here as time allows.

No problem, man. It really looks like you've done a lot of your homework already. Getting REW up and running is a challenge sometimes, with all the cards, adapters and other stuff that goes with it.

Again, welcome and happy to have you here.