# REW and UMC-200



## neo_2009 (Nov 13, 2009)

I have an UMC200, and so far i've been using REW generic filters, but with B18 version, i've updated the filters to the exact umc200 frequencies.
I've tried a new approach, reducing the number of filters, using lower Q values (to wider the filter scope).

Filters Right:









Filters Center:









Filters Left:









I've taken new full measures, one with the FLAT setting, and another with EQ Manual 2, with REW filters applied to all channels, but the results aren't still what i'm trying to achieve: 









As you can see, there is still a large null in the 70Hz-140Hz, and a huge "dip" in the 400Hz-2kHz.
The first dip could be due to the crossover at 120Hz, so i will try lowering the crossover to 80-100H, to try to achieve a better output on the 70-100Hz region.
I will also try to lower the 400Hz-2KHz region, by at leat -5db.

Addressing this two point, i think i will be able to achieve a nice house curve.

Finally, i have a specific question regarding REW:
- as REW is only capable to generate a stereo signal, the center and surround channels are not used.
This complicates the analysis of the full frequency measures, because i cant see the effect this channels add to the final sound.

As the UMC200 has a All Stereo Mode, it would enable to generate a signal with all the speakers playing.
Would it be possible to use this mode to produce a full frequency measure, with all the 5.1 speakers?

The full mdat file is here, if anyone want to take a look 
- https://meocloud.pt/link/8e450317-ab7a-4763-a1eb-ab225d3c82a4/full_measures (1).zip/


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## JohnM (Apr 11, 2006)

Measuring with multiple speakers playing generates results with lots of comb filtering, not useful.

To measure individual channels connect one of the REW output channels to each of the 7.1 analog inputs on the UMC-200.


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## neo_2009 (Nov 13, 2009)

Thanks John, but i've already measure each speaker individually.

Nevertheless, i don't remember if i selected the correct options on the UMC200 to guarantee that the crossovers were not active and the speakers were indeed receiving a full frequency signal.

From your post can i assume that the correct procedure is measuring each speaker individually and correct it individually only?


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## JohnM (Apr 11, 2006)

For low frequencies best correcting each speaker individually. If you are considering adjustments higher up the range applying different corrections to left and right can have odd effects on stereo imaging, even if notionally the corrections seem to make the responses more similar then they were - at higher frequencies the ear readily discriminates the direct sound from the later contributions of the room so the measurement may be a poor representation of what is heard, applying a narrow window to the impulse response helps to isolate the direct sound but it is nonetheless best to apply the same EQ to left/right pairs above the bass range.


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## neo_2009 (Nov 13, 2009)

Thanks, i will adjust the filters based on the information you provided.


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## neo_2009 (Nov 13, 2009)

JohnM said:


> If you are considering adjustments higher up the range applying different corrections to left and right can have odd effects on stereo imaging ...


@JohnM, this advice also applies to the other channels (center, surr, back surr), or only to the L/R speakers?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Just the front L/R, as there is no stereo imaging associated with the rear and center speakers.

Regards, 
Wayne


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## neo_2009 (Nov 13, 2009)

According to that principle, in what frequencies would you advise to apply a filter to both Left and right Speaker?










Based on your observations, i would select only the points where left and right speaker intercept, namely : 

- 440Hz, -5db, 10 Q
- 1045Hz, -10db, 5 Q
- 16000Hz, -5db, 2 Q

What do you think?

Regards.


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## JohnM (Apr 11, 2006)

I wouldn't make any adjustment as high as 16k, measurements that high are affected by many factors beyond the speaker itself but what the ear mainly detects there is the direct sound from the speaker (if you are young enough to still hear 16 kHz )

The cut at 1k looks much too large, should probably be about 2 to 3 dB and a Q of about 4.

I probably wouldn't do any more than that, "less is more" when it comes to EQ.


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## neo_2009 (Nov 13, 2009)

Thank you very much.
Regards!


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## Wayne A. Pflughaupt (Apr 13, 2006)

neo_2009 said:


> Based on your observations, i would select only the points where left and right speaker intercept,


 Looks like you missed John’s point. It’s not a matter of EQing where the two traces cross. The issue is that using independent filters for the upper frequencies (_even if the measurements do not match_) can do strange things to your stereo imaging. Therefore above ~3-400 Hz or so you should always use matching (identical) filters for both speakers. (Again, this does not apply to the back or center channel speakers.)



neo_2009 said:


> According to that principle, in what frequencies would you advise to apply a filter to both Left and right Speaker?
> - 440Hz, -5db, 10 Q
> - 1045Hz, -10db, 5 Q
> - 16000Hz, -5db, 2 Q


I’ll start by saying that the idea for full range equalization is to only address problematic broad trends, as they are the easiest to fix and make the most audible improvement. After all, “audible improvement” is ultimately what we’re after, is it not? What you _don’t_ want to do is chase every little ripple in response with a whole slew of tight filters. As John said, “less is more when it comes to EQ.” When you have time you might want to peruse my article on the subject, which you can access from my signature.

I’ll comment on your filters and then make my own recommendations:

“- 440Hz, -5db, 10 Q”
There’s nothing at 440 Hz that needs attention. On top of that, “broad trends” are addressed with broad filters. As such 10 Q is not suitable because it is a notch filter.

“- 1045Hz, -10db, 5 Q” 
See my comments for a 1 kHz filter below.

“- 16000Hz, -5db, 2 Q”
As above – there’s nothing at 16 kHz that needs attention.

My recommendations:
7 kHz, ~1.9 Q, +2-3 dB. This will lift the broad sag in response between 5-16 kHz.
1 kHz, ~2.9 Q, -~3 dB. This will bring down the peak.

I’d also address a couple of independent lower-frequency filters to the speaker that belongs to the blue trace:
350 Hz, 5.8 Q, -2 dB
250 Hz, 4.5 Q, +3 dB

Regards, 
Wayne


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## neo_2009 (Nov 13, 2009)

Wayne, thank you very much, your explanation was very clear, and i will look at your article in order to have a better understanding of the all EQ process.
Regarding the filters for center and surround channels, i will try to apply the principles you described, addressing only the problematic broad trends.

Regards


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## neo_2009 (Nov 13, 2009)

Hello Wayne.

I've read the articles in your signature, namely the On minimal EQ Target Levels / Hard Knee House Curve.
Based on that article, i've redefined my filter for the subwoofer.
There's some assumptions, related to my particular room:

- The room is in the attic, and the roof is made of plasterboard material, with an inverted V shape. When listening to some movie tracks, the roof rumbles and vibrates. Using REW sweeps and the RTA window, i've discovered that the problematic frequencies are in the 32-38Hz.
- As such, i could maintain the 20-28Hz peak, and applied a house curve after 30Hz (curiously, in line with what you suggest in the article), to be able to reduce the 32-38Hz output, reducing the roof vibration.
- I wanted to lower the 32-38Hz output, without interfering in the 20-28Hz region, so i applied a wide filter (-8) on the 46Hz frequency;
- I've a large dip in the 50-70Hz region, so i applied a very wide filter (+3) in 62Hz;
- I needed to lower the peak at 85Hz, so i applied a narrow  filter (-10) in 87Hz.

Based on those assumptions, i've selected the following filters:

46,80 | -8 | 3
62,97 | +3 | 1
87,04 | -10 | 12

That produced the following result:










Could you please give me your opinion?
Regards!


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## Roger Dressler (Aug 1, 2009)

neo_2009 said:


> Based on those assumptions, i've selected the following filters:
> 
> 46,80 | -8 | 3
> 62,97 | +3 | 1
> 87,04 | -10 | 12


Do not apply filters with higher Q than the displayed response smoothing. It should be the opposite. If you look at the unsmoothed, or 1/24th octave responses after EQ, I suspect you will see that you drilled a hole at 87 Hz. Let's see the less smoothed responses before deciding the filters.


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## neo_2009 (Nov 13, 2009)

Hello Roger.
Thank you for responding 

I've used the 1/6 smoothing based on the recommendations of Wayne's article.
Here is the un-smoothed graph:


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## Roger Dressler (Aug 1, 2009)

neo_2009 said:


> I've used the 1/6 smoothing based on the recommendations of Wayne's article.


Just saying that with 1/6th smoothing, you cannot really see what's happening with a Q of 12. The unsmoothed plot shows the extra ripple in the response. With a lower Q it might look something like the red line.

Now, where a higher Q is justifiable would be if you are killing a ringing resonance in the time domain. Is that what led to the Q=12?


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## neo_2009 (Nov 13, 2009)

Here is the graph when using a 10Q in the 3rd filter:










I'm still learning, so the 12Q was a sort of random choice


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## Roger Dressler (Aug 1, 2009)

neo_2009 said:


> Here is the graph when using a 10Q in the 3rd filter:
> I'm still learning, so the 12Q was a sort of random choice


Your random choice? 

Anyway, looking better. Keep going. See if the extra ripple at 87 Hz goes away. The Harman SDEC procedure is a good one. Start with the broadest corrections possible, then touch up with narrower ones as needed.


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## neo_2009 (Nov 13, 2009)

^^^
I tried to select a Q value that would lower the 87Hz peak, that would maintain the house curve, without lowering too much the 40-42Hz region.


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## Roger Dressler (Aug 1, 2009)

neo_2009 said:


> ^^^
> I tried to select a Q value that would lower the 87Hz peak, that would maintain the house curve, without lowering too much the 40-42Hz region.


If reducing the Q of the 87 Hz band attenuates the 70-100 Hz region too much, reduce the attenuation.


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## neo_2009 (Nov 13, 2009)

I've used the UMC-200 optical input, selected STEREO mode so the PEQ settings were activated if needed, and measured the FLAT response versus PEQ response: 










Looking to this image, i've noted a big null in the 7K region, and a big bump in the 10K reagion.
The 7K null was presented in the individual L/R measures, and Wayne had already suggested a "7 kHz, ~1.9 Q, +2-3 dB" filter, but i hadn't applied yet.

Regarding the 10K bump, the individual L/R measures didn't show it, but a comparison between L/R and L+R (without sub), shows that the summed response generates a big bump in that region:










Looking at this graphs, i would be tempted to apply two new filters, to both L/R:

- 7,07 kHz, 1.875 Q, +2-3 dB
- 10,05 kHz, 5 Q, -5 dB

What do you think?
Regards.


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## JohnM (Apr 11, 2006)

To be honest, you have a shallow dip at 7k rather than a 'big null' (strictly speaking 'null' should be reserved for very narrow and very deep drops in the response). You shouldn't attempt any correction for the small bump at 10 k as it is only present with both speakers playing, if you applied a correction you would be creating a dip for any content that was on the left or right of the soundstage. The response at such high frequencies is also very variable with position. It's easy to get carried away with EQ, best not to overdo it.


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## neo_2009 (Nov 13, 2009)

Ok, it makes sense, thank you for the corrections.


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