This thread started as a PM converstation between myself and Jevansoh, who has been kind enough to assist me in understanding REQ waterfall and ETC graphs to analyze reflections and resonances in my listening room. It has been moved to an open thread so we can share our progress with others, and perhaps receive other useful input.
Waterfall--doesn't look right
Oct 1, 2012 at 3:10 pm
Oct 1, 2012 at 3:33 pm
Please click "Limits" in REW and change the bottom limit from 0 to 30db. I can see 90db at the top (looking at the left hand side) and if that's what it is set to, then by setting to 30, we'll be mostly out of your noise floor and have a 60db spread. That will make the mountains in the foreground disappear (or closer to it) showing the floor and giving us more detail.
After setting a 60db spread using the limits function in REW (top right hand corner) by changing the top and bottom parameters to just show the top of the graph without cutting any off and the bottom 60db less than that, then also change the "right" parameter in the limits section from 200hz to 300hz.
Next, click "Controls" and set the time range to around 500ms. When you do that, if any parts of the waterfall are still outside the graph limits (the part at the bottom of the screen) then you'll have to raise it. Do this in 100ms increments. If, when you set the top/bottom numbers back at the Limits window to a 60db difference and that alone shows the entire waterfall, then you needn't perform this step.
I hope this helps. Feel free to ask any further questions and I'll be happy to guide you in any way I can.
Thanks so much for sharing this information with us. This is the most fun aspect of AVS for me!
Oct 1, 2012 at 3:47 pm
Oct 1, 2012 at 4:04 pm
In fact it does look "right", the problem is the underlying data. The problems starts with capturing LF data: the noise floor in our living rooms is way too high to capture the actual decay over 60dB. Then there's always a tradeoff between time and frequency resolution, i.e. if frequency resolution is good, time resolution suffers and vice versa. I didn't ask for waterfalls and now you know why
Oct 1, 2012 at 4:07 pm
Actually, this is looking much better.
Unfortunately, it appears you have some major resonances here.
The time range is at 500ms. That was a start. This is now the only thing that needs changed to get a proper Waterfall.
I'd set it to 1000ms. If that makes the bottom disappear into the noise floor, then back it down to 900ms, etc, etc, until you can "just" see the floor like you can now at what appears to be around 175hz.
Also, it appears you may have some noisy conditions. Is this a dedicated room with any isolation or a family room/no isolation? I'd guess that latter. After seeing the full picture, depending on what time range you end up with, we may go tweak the bottom (back at the limits window) to 40db-45db instead as that is the noise floor in most residential common space homes without any proper isolation. It is very common, so don't feel bad. Very few people have noise floors less than 40db.
It's hard to get it right the first time or two. Just keep playing with it and you'll get a nice looking graph that gives us plenty of detail and then the real fun begins. I can't wait to see the difference with Audyssey off vs. on vs. 4520. In my case, the resonances are worse with Audyssey on, even though the frequency response is better. That suggests some phase issues to me, but I'm not quite clear/sure what's happening and am curious if Markus has any input/ideas??
Send me another draft and I think we'll have it ready to post to the forum next time.
Oct 1, 2012 at 4:19 pm
I don't have a dedicated listening room. The back of the room opens up to the rest of the ground floor (hallway, kitchen, dining room, etc.). The room has LF room treatments (four RealTraps mini-traps, two in each front corner), and otherwise the room is carpeted, with soft furniture. I am single, so taking measurements with the listening room in dead silence is not an issue. If I recall, REW shows my noise floor right around 35-40dB.
Oct 1, 2012 at 4:51 pm
Go to the limits screen and set the bottom to 45db for now. Set the top to 100db.
Then go to controls and set the time range to 1000ms.
Send me what you get after doing that and let me take a look.
What type of mic setup are you using to do your measurements and have you done a soundcard and mic cal within REW?
What you sent before really did appear to be coming together nicely and was pretty much what I was expecting for the circumstances in which you described above, so I think we're on the right track.
Let me see this latest graph with these settings and we'll go from there.
Hang in there, we'll get it. Then you can always use these settings in the future and it won't be any hassle for further graphs. (Unless you add more bass traps, which I HIGHLY recommend. Even cheap fluffy insulation does wonders, believe it or not. There's no reason to spend mega $$$ on brand name acoustical products as you've done, but they do look nice and if you have the money, it will save you some time and a bit of itching.)
PS For extra credit, could you give me the full dimensions of your room(s)? L/W/H? Does your theater room just open up into the other rooms with a standard doorway opening of around 36" or less, in one area, or is it very open and basically one big room, acoustically speaking? If the latter, I need the full dimensions so I can calculate your estimated modes/resonances and see if they line up with the graph you're about to send. If they don't... We need to look into taking the measurements again and verify everything is set up correctly as your previous FR measurements may also be incorrect. If they do.... Then we're all good and you'll even have a plan for future treatment if you wish to make things better. Do you have any boominess now? Are you dissatisfied with anything in the lower frequency/bass range? Have you heard good tight bass in an accurate room before, for comparison, and how does your room compare?
Oct 1, 2012 at 5:49 pm
OK, here is the latest iteration:
Rough room layout:
Ceiling height is 10'. With REW, I am using a SoundBlaster X-Fi soundcard with a EMM-6 individually-calibrated mic. The soundcard has been calibrated in REW properly, and I have loaded the appropriate calibration file for the mic.
I have worked continuously over the last several years to fine-tune my room and its equipment to achieve what I think is pretty good sound. To me, my bass quality is very good, both in smoothness and extension. The bass has been a primary focus, and I have experimented with room placement, the RealTraps treatments, upgrading to MultEQ XT32 (I also had an AS-EQ1 until I upgraded to the 4311), and adding a third sub (the one right behind the MLP.
The listening room:
This is the Pro calibration that I am using right now. Doesn't it look reasonably good?
Oct 1, 2012 at 7:23 pm
I will respond in detail this evening.
For now, by golly, I think you've got it re the Waterfall!
I'd probably set it to show 15-300hz and now set the bottom to 40db which seems to be your noise floor, as you previously stated. (That's what I do here to make certain that lowest mode shows)
Although I haven't looked in detail at everything, I did take a good but quick look at the waterfall, and once you set the above, it's ready to post to the forum and share.
I'd like to make my comments, at least the ones on the waterfall, in the forum so everyone can benefit if it's okay with you. I just figure if I'm going to do the analysis everyone might enjoy in seeing the results and we may get more people to participate.
Now I want to see this same waterfall with these same settings, both with Audyssey on and off and then again when you get the 4520.
Thanks, and again, I'll submit a detailed reply on the forum later this evening if that's okay with you.
Edited by AustinJerry - 10/6/12 at 4:53pm