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Discussion Starter #1 (Edited)
Hey All,

Thanks in advance for reading through this and giving your input!

Intro
See my signature for associated equipment. Also, FYI, the UMC-200 only allows for 3 bands of PEQ settings for the subwoofer channel.

Finding the best spot, and 1st measurement
In my non-dedicated home theater room, there are three places that my subwoofer can be placed. Inside of each of the main L/R speakers and behind the couch. I used my UMIK-1 with REW to measure the subwoofer in all three locations and the "best" location was inside my left tower. I say "best" because it's still no where near flat!

sub with no eq.jpg

Generating Filters
So, I asked REW to generate some EQs for me, and it gave me these six filters.

rew eq guess.jpg

(I chose these ones because according to the "predicted" resulting curve in REW, these ones made the changes that got me closest to flat)
Frequency____Gain______ Q
27.70 _______-6.9 ____4.52
47.60 _______-11.2____9.01
51.4 _______-7.3 ____21.34

(I couldn't use these ones because I have only 3 PEQ bands to use)
37.35 _______1.9____2.00
57.3 _______ 1.2____2.00
76.40 _______-9.6____19.78

The Result
The picture below shows my measured response after applying the first 3 filters in the list of six above. It is much better than the original graph, but still very far from flat. It also does somewhat resemble REW's predicted effects of applying those three PEQ filters.

sub with 1st eq.jpg

Questions:
1) Is there a way to tell REW that I only have 3 bands in my PEQ? This way it might be able to prioritize or limit the filters that it puts out?
2) I've thought about taking the 47.6hz band and raising the gain up a few dB to try to eliminate the trough around that frequency, even just a little bit. Good idea or bad idea?
3) When I am setting up REW to generate filters for a given measurement, part of that process is "setting the target level". What is the best/right way to determine the best/right target level?
 

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Hi here is a link to posting graphs http://www.hometheatershack.com/forums/rew-forum/934-please-read-posting-graph.html

Sorry tried to look at Drop box but i get no graphs

1. In EQ tab change to manual the ones you don't want to use with the your EQ that is listed in the EQ tab? Another way is to use the RTA if your EQ is not listed.

2. Sometimes yes it's ok but can't see your file. If you have headroom can come into your decision.

3. Generally just clicking on the "Target Level" does the trick.

Hope this helps a little
 

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Discussion Starter #3
Phillips, thanks for that link and for your answers to my questions.

I'm having a hard time figuring out what your meaning is with the answer to my first question though, could you please clarify?
 

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Phillips, thanks for that link and for your answers to my questions.
No problems

I'm having a hard time figuring out what your meaning is with the answer to my first question though, could you please clarify?
1. In the "EQ" tab > "EQ Filters" tab (above the frequency graph) with the filters that have been suggested there is "Auto" or "Manual", "Auto" is default so use the drop down for selection of Manual e.g if using the MiniDsp EQ there are x 6 filter slots so if you only wanted to use x 3 change the bottom three to "Manual" and when you do the "Auto" detection of filters REW will ignore the three "Manual" slots.

2. Before doing any EQ find the best position for the sub (you say this is the best, i suggest keep on trying and move the mic around as well for optimum combination). You can use the RTA for this for real time measuring. When measuring subs i always measure with the crossover either turned off or turn the subs crossover up to the highest it will go to.

3. Which REW EQ filter selection are you using for the UMC 200, they aren't all set equal e.g. SMS -1 Q factor 4.3 will be Q factor 8.6 in the MiniDsp and then some have Bandwidth giving a different shape filter. Either use the RTA for Eqing or try to find the closest to EQ to use with REW. I have a DSpeaker Anti Mode Dual Core 2.0 EQ etc and i use either MiniDsp or Generic.
 

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Discussion Starter #5
I say it's "best" because the other two possible locations that I measured had much worse problems (I think) to try to correct. For example, this graph shows the measurements when the sub is placed next to the left tower speaker:

sub on the left.jpg

Trying to fix that dip between 50 and 70hz doesn't seem like a good idea to me. It would not be a "subtractive" EQ!

Also, I'm using the "generic" EQ setting in REW. Should I consider using something else?
 

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I say it's "best" because the other two possible locations that I measured had much worse problems (I think) to try to correct. For example, this graph shows the measurements when the sub is placed next to the left tower speaker:

View attachment 44171

Trying to fix that dip between 50 and 70hz doesn't seem like a good idea to me. It would not be a "subtractive" EQ!

Also, I'm using the "generic" EQ setting in REW. Should I consider using something else?
Yes if it isn't lining up with the Prediction.

Does your EQ use Q or Bandwidth (BW)?

I would change to 12th smoothing don't forget this is with no smoothing, then make up your mind where the sub goes.

Have you tried moving the mic (listening position) you might be sitting in a null?

1. Your EQ isn't in the list of EQ so basically measure place 3 eq filters and see if it lines up with the Prediction, if not click on another EQ listing and enter those filters, some are the same.

2. Another way if this doesn't work is to either half the Q or half the Gain.
 

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Discussion Starter #7
My processor allows me to adjust the Q, not the bandwidth. My listening position is quite fixed, I might be able to get a few inches of movement, but no more than that.

Between the two graphs below, which do you think would be the best position for the sub? Both graphs have 12th octave smoothing applied.

Next to my right tower:
right with 12th octave smoothing.jpg

Next to the left tower:
left with 12th octave smoothing.jpg
 

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Discussion Starter #8
While I was tweaking things this morning, I was able to produce this frequency sweep. The sub is located next to the right tower speaker, which is the blue graph (no EQ) above.

flattest to 52hz.jpg

I've found that it's not too hard to manually adjust the frequency, gain, and Q to achieve better results than REW's predicted filters. I didn't have enough time to get it better, but this graph is a definite improvement over what I had with no EQ!
 

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The first graph (Post 7) is the better one because the dip @ 60hz is more prominent and with three filters fine tuning you should get a respective response. Also look at the waterfall graph which is very important for decay, could give you a clue to where the filters should be placed.
The fine tuning depends on your EQ capabilities.
 

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Discussion Starter #10
I generated the waterfall graph for the last graph that I posted. What kinds of things can I learn from this graph? What are the important bits of info that it gives me?

waterfall.jpg
 

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Move the scroll bar up so it shows more of the top about half way

To give you a idea (only) i have attached a graph, of my mains only but you should be able to measure your sub up to about 120hz.

Also you should be measuring to the subs full range, with either crossover turned off or turned right up.

no eq.jpg

antimode calibration.jpg
 

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Discussion Starter #12
When you say to measure the sub "full range" what does that mean? A crossover of 200hz or something? I usually cross my sub over somewhere between 50hz and 75hz, whichever sounds best in my room. Because of that, I've been measuring it to 80hz, because I will most likely never cross my mains over at anything above 75hz.

Is this waterfall graph any better?

better waterfall.jpg
 

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When you say to measure the sub "full range" what does that mean?
Full range means measuring to its lowest and highest limits generally from 0 - 150hz depending on your sub. Turn off or turn the subs crossover up as far as it will go.

I usually cross my sub over somewhere between 50hz and 75hz, whichever sounds best in my room. Because of that, I've been measuring it to 80hz, because I will most likely never cross my mains over at anything above 75hz.
You have to remember that crossovers aren't brick walls they have slopes.
I was told to measure subs this way.

Is this waterfall graph any better?

View attachment 44218
The scale is wrong you have extended the ms out to 1000, should be at the most 500.

Move the graph down.

If you look at the 35 and 70hz decay that is noise from somewhere (they don't actually decay), the frequencies are harmonics.
 
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