Range and integration questions

[tomtuttle]

First, and most importantly, I want to sincerely thank JohnM, brucek, Sonnie, Wayne and all of the other stalwarts of this forum for so generously sharing their work and knowledge. I am a serial lurker, and had not until recently acquired both the required time and equipment to put all this wonderful information into practice.

The concept really is a miracle; gathering places like The Shack allow people from all over the world to learn things from each other in a rich and rewarding way. Even ten years ago, such collaboration would have been impossible. When I think of how much more learning I can do so much easier than our forefathers, I am humbled and amazed. A dear and wise friend once told me that in our lives, at any given point, we are always either the teacher or the student. Being mindful of that dynamic enables us to more thoughtfully care for each other.

I am not a technician. Oh sure, I'm the alpha geek in my family, but there are so many programmers and engineers around here that I wanted to reveal my predisposition towards the business process and user experience early on.

I'm still pretty early in my measurement and filtering process, but am very excited about what I've learned and experienced so far. I hope you will all bear with me as I continue the journey.

I am using a Soundblaster Live! 24 external card, a RS analog meter and a BFD. I have a big room adjacent to a big foyer and a SVS PB12-ISD. I have Axiom M60 mains and a very modest Denon 1804. There is a PC in my AV rack with vastly underutilized potential (I'll save that story for another thread!) but I am using it to process the REW measurements (i.e. not a laptop). It seems up to the task.

I learned a couple things that might be obvious, but cost me a bit of time.

1. The Soundblaster card is NOT a permanent installation for me at this time. My vision was to use it only for the measurement process and then employ it elsewhere and continue to use the AC97 coaxial output from the computer to the Denon. I learned that - even when specifying the Soundblaster specifically in the REW soundcard settings, I ALSO had to mute the line-in for the default sound device in the OS.

2. Not all cord, adapter and splitter manufacturers think that Red is Right or that White is Right. Even if you are absolutely certain you connected everything consistently and correctly throughout the signal path, it is possible that some problem you can't figure out is a "wires crossed" problem rather than a "buttons clicked" problem.

3. The meter "hears" much better than I do. Even though I had done a lot of listening and calibrating in this room previously, REW allowed me to discover a couple of really important and exciting things about positioning and phase.

Now, the questions (with no graphs at this time). I know they are dumb newbie questions, and will express my gratitude for your indulgence in advance. A certain amount of "hey, look at the new guy!" is expected

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?

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

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?

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

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.

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?

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?

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.

[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.

[tomtuttle]

Otto, thank you so much for the gracious welcome and especially for the helpful reply. You helped me clarify my thinking significantly regarding the sub+mains issue. I think that - sometimes - I get confused about the fact that you can MEASURE whatever you want, but you can only FILTER the sub. Duh.

It seems like it might be useful to measure just the mains so that I can quantify how low/flat they play. My suspicion is that they're probably pretty flat to about 50Hz and I might consider the notion of letting them play full range and tweaking the crossover on the sub accordingly. I suppose in this case, I'd want to set a corresponding new target in REW.

Ultimately, I'm sure I'll try it multiple ways (mains large with crossover on sub defeated, mains large with crossover on sub engaged, mains small with crossover on sub defeated).

Otto wrote:

This might be spec'd in the user's manual.

Wow, you've never tried to get useful information from a Denon manual before, have you? :raped:

It is an iterative process, but one I enjoy and have done a few times

I hear that. It's supposed to be fun, right? My wife doesn't understand why I would find it interesting; it would be a boring world if we were all fascinated by the same things.

Can you adjust the phase of the sub

Oh, absolutely. I really like that the SVS includes a variable phase and variable crossover. I already played with the phase and positioning quite a bit after getting REW up and running and was really amazed by the measurable differences that subtle changes can make.

Thank you again. Can't wait to get home and play with this some more.

[clubfoot]

Welcome tomtuttle, thought I'd add my experience so far as a fellow newbie. At first I was also very concerned with mains integration, but soon realised as you have that small changes in sub location can make big changes in response.
So, what I did first was find the sub location that gave the smoothest response that followed the "ideal" target curve, then adjusted my seating location to reduce dips/peaks. After completing all the sub measurements, I discovered that the mains by themselves, had a dip in the crossover region which I corrected by repositioning them for flatest bass response. A few tweaks of the phase control and the full frequency response looks as flat as ever.

My point is it may take allot of measurements but once you see how the location of your sub, your seat and your mains interact, you will be on your way to smooth listening

Have fun.