Interpreting the Dirac results. (Beginners)

[ansat]

So you ran the measurements and have all these fancy graphs for your speakers. So what basic information can we get from these. Well, some good information can be taken from them to determine if you need to use other tools such as REW or not to address some other issues. It will also show you where you need to set your crossover as well as if lack of treatments (high reflectivity) is really hurting your room.

So lets look at the charts.

NOTE: This is what I expect to see from this particular speaker - the weird hump at the end seems to be a trademark of Definitive's older silk dome tweeters.

The chart above shows the spectrum. The blue line is what Dirac saw from your speaker. The orange line is what Dirac want to do. And the green line shows what Dirac did. A note about the green line - This is not an actual measurement and if measured, this is not what you would see.

Lets start with the blue line. The bottom of the chart is your frequency response from 10hz to 20,000 hz in your room and the side is db from reference (which is not a specific number). In a perfect room (or better yet - outdoors) this response would be + or - 3 on this chart across its manufactured measured frequency response.

The Orange Line. This is the target that Dirac is going to make a filter to match to.

And last, the Green line. This line represents the filter that is being created.

So what information will this tell us?

The blue line shows that the natural roll off my back speaker in my room should is 50hz. Therefor, my Xover for this speaker needs to be 50hz or higher (regardless of what the manufacturer claims).

The blue line compared to the orange line shows me that dirac is adding 8db of gain at 12k, 3db of loss at 5k, 8db on one speaker at 250hz (3-4 on the other). 3db of loss at around 120, 12db of loss at 65hz and 10 db of gain from 30-45. Out of all these gains and losses in the filter, which ones are important? I would say that any gain over 6db should be looked into to see if it can be corrected by other means. Any loss that is being applied is usually caused by reflections in the room.

Now to the misunderstood green line. For the most part. It is not helpful or an accurate representation of much. The only major thing to look for which you can see between 30hz and 50hz on my graph is where the green line deviates from the orange. This indicates areas where dirac applied the full 10db gain and it was still not enough to fix the problem. In my case, its the passive radiator on my rears that gave the boost at 30hz and dirac is trying to correct for that. I will be crossing over at a higher point then that to be sure that I avoid that much gain.


From flak (Dirac) on the green line -

Jan 3, 2015 8:51:55 GMT -5 flak said:

The green line is often misunderstood because it is the average of the nine FR responses in the nine positions after correction, as such IT IS an accurate representation, even if a computed one, and it can be validated by averaging the same nine measurements with REW when using the same smoothing and mic position.
The blue line is an average of nine measurements before correction and it can be usefully and meaningfully compared to the green after correction line.

Those average graphs are useful in real life... the before and after correction graphs for the single individual positions are also accurate when present as in the standalone full Dirac Live version.

Flavio

To illustrate what Flavio is talking about. Here is a image that

I pulled from the MiniDSP manual.
As you can see, each measurement carries wild swings below 1k and this would be normal. The measurement that we are seeing in the Dirac LE is just the average line. I do not know if we will get this functionality in the full version.




This chart is your impulse response. Dirac uses this to set your delays and this is a representation of energy over time. This chart is a pretty good one. (but the worst one that I have) If you look at the blue impulse line for any speaker other then your subwoofer. You want to see only 1 point and a nice tight grouping into that point (like what you see on the green measurement). Looking at my blue measurement the peak is at 9.94ms and you can see another peak at 10.25ms. While Dirac did not capture this perfectly, it is cause for concern as this is a reflection in your room that is pretty close to your speaker and is almost as loud. The further your peaks are out the further the reflection is. If you are getting some really bad peaks then REW will be needed to identify what is going on further.


REW tutorials with the XMC (Beginner tutorials using REW)

Do I need a minidsp for multiple subs and how to use one for such
Subwoofer placement with REW
how to use the USB input to measure other speakers

Dirac / XMC-1 F.A.Q.

As always, your questions and comments are welcome.

Let me know if I missed anything important.

Tony

[dazza]

I have two interesting artifacts based upon my most recent Dirac run;

1) What could be causing the high frequency content on the sub Frequency response?
2) Any ideas as to the significant loss at 40Hz for the centre speaker?  I have the crossover set at 60Hz, should I care about this loss?

Any help most appreciated.

[ansat]

Jan 2, 2015 18:59:00 GMT -5 dazza said:

I have two interesting artifacts based upon my most recent Dirac run;

1) What could be causing the high frequency content on the sub Frequency response?
2) Any ideas as to the significant loss at 40Hz for the centre speaker?  I have the crossover set at 60Hz, should I care about this loss?

Any help most appreciated.
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At that much energy, I am not sure what is causing it. What kind of sub do you have?

Since your crossed over at 60, I would not worry about the dip. But that is a HUGE!! spike on the center. I am surprised that the center hasn't walked off your stand. Lets talk about that as well, Whats your placement on that center like?
Tony

[Lonnie]

Jan 2, 2015 18:59:00 GMT -5 dazza said:

I have two interesting artifacts based upon my most recent Dirac run;

1) What could be causing the high frequency content on the sub Frequency response?
2) Any ideas as to the significant loss at 40Hz for the centre speaker?  I have the crossover set at 60Hz, should I care about this loss?

Any help most appreciated.
Attachment DeletedAttachment Deleted

The high frequency artifacts on the sub could be just about anything from your HVAC to outside noise, but I wouldn't be concerned with it because the level is so low.

In regards to the center channel I have two words for you..Room Mode relative to the position of the center channel. Don't be concerned about this one either.

Lonnie

[ansat]

Jan 2, 2015 20:05:39 GMT -5 Lonnie said:

Jan 2, 2015 18:59:00 GMT -5 dazza said:

I have two interesting artifacts based upon my most recent Dirac run;

1) What could be causing the high frequency content on the sub Frequency response?
2) Any ideas as to the significant loss at 40Hz for the centre speaker?  I have the crossover set at 60Hz, should I care about this loss?

Any help most appreciated.
Attachment DeletedAttachment Deleted

The high frequency artifacts on the sub could be just about anything from your HVAC to outside noise, but I wouldn't be concerned with it because the level is so low.

In regards to the center channel I have two words for you..Room Mode relative to the position of the center channel. Don't be concerned about this one either.

Lonnie

Lol, I was thinking resonating frequency of his entertainment center.

Tony

[dazza]

Lonnie/Ansat,

Thanks for the response.

The sub is a PSA XV15se. Based upon Lonnies response, it looks like I have loose floorboard that the it's sitting on. Could this be the reason?

Ansat: the centre is sitting on a homemade stand, 12" high. I guess this could be resonating.

I will move the sub and place the centre on the floor to rule out the stand.

Thanks for the responses.

[ansat]

Jan 2, 2015 20:21:35 GMT -5 dazza said:

Lonnie/Ansat,

Thanks for the response.

The sub is a PSA XV15se. Based upon Lonnies response, it looks like I have loose floorboard that the it's sitting on. Could this be the reason?

Ansat: the centre is sitting on a homemade stand, 12" high. I guess this could be resonating.

I will move the sub and place the centre on the floor to rule out the stand.

Thanks for the responses.

Just put a towel under the center to decouple it.

[ansat]

Had a little more time to look at the sub graph, don't worry about the extension. Looking at the psa charts the are flat to 200+.

But, I think you can do better with the placement. Try a different location and see if the charts are as wild.

Tony

[dazza]

Thank you. I will try both this weekend.

[ansat]

A little tip to speed things up if you don't wanna use rew. Take one measurement with dirac at the main listening position and hit continue. You can see the graph. you can go back to the measurements page and delete your main listening position and redo it the look at the graph again. Rinse. Lather. Repeat.

Tony

[hemster]

Stickied as this is helpful for Dirac noobs.

[autocrat]

Not 100% sure this is the best place to put this, but I'm not starting a new thread just for people to look at moi.

Anyway, here is my sub disaster:





Sub is a custom sealed unit with an 18" Maelstrom-X driver and a 1KW A/B amplifier. I think I'll try nailing a beanbag to the wall behind it and see what that does.

[ansat]

Jan 2, 2015 23:02:28 GMT -5 autocrat said:

Not 100% sure this is the best place to put this, but I'm not starting a new thread just for people to look at moi.

Anyway, here is my sub disaster:



Attachment Deleted

Sub is a custom sealed unit with an 18" Maelstrom-X driver and a 1KW A/B amplifier. I think I'll try nailing a beanbag to the wall behind it and see what that does.

Grab your impulse before / after. Lets see if a new position might help.

Tony

[autocrat]

I'm a bit reluctant to move it, sod weighs 60kg+ so I'll need to get the trolley out (I have a comical mental picture of the enormous sub perched on the collapsing leather lounge while I do a sub crawl).


Anyway, I'm not sure what the impulse graph means for the sub, so any insight you have will be a plus.

[ansat]

Jan 2, 2015 23:31:50 GMT -5 autocrat said:

Attachment Deleted

I'm a bit reluctant to move it, sod weighs 60kg+ so I'll need to get the trolley out (I have a comical mental picture of the enormous sub perched on the collapsing leather lounge while I do a sub crawl).


Anyway, I'm not sure what the impulse graph means for the sub, so any insight you have will be a plus.

was hoping the graph would scale better. I was looking to see the setup of the room. (corners and walls) (the impulse will show reflective issues.) How have you been EQ'ing the sub so far? Another thought would be to rotate the sub 45 - 90 degrees to see if that changes the cancellation at the MLP.

Tony

Tony

[autocrat]

Also, I suspect I'll get a better Dirac result if I tame Mt Everest that's sitting across 30-45Hz, I can probably get close with the single-band PEQ on the plate amp, but naturally fixing the room would be a better result.

[autocrat]

Jan 2, 2015 23:46:34 GMT -5 ansat said:

I was hoping the graph would scale better. I was looking to see the setup of the room. (corners and walls) (the impulse will show reflective issues.) How have you been EQ'ing the sub so far? Another thought would be to rotate the sub 45 - 90 degrees to see if that changes the cancellation at the MLP.

Tony

Yeah, the graph isn't too good, but getting some nice reflections out to 80ms Room is 12m x 6m, we sit about 5m back from the front wall. Sub is 1m in from a corner, about a foot out from the wall.

Thanks Tony, I'll give twisting it around a go and see what it does.

[ansat]

Added REW links. I designed these for those who have never successfully run REW. For those who know how to use REW, these are round about ways to use REW, but I wanted to keep things easy to understand and use as few REW tools as possible.

Tony

[flak]

Jan 2, 2015 15:39:12 GMT -5 ansat said:

Now to the misunderstood green line. For the most part. It is not helpful or an accurate representation of much.

Let me first thank Tony for the great and knowledgeable work he is doing in supporting the Emotiva forumers

The green line is often misunderstood because it is the average of the nine FR responses in the nine positions after correction, as such IT IS an accurate representation, even if a computed one, and it can be validated by averaging the same nine measurements with REW when using the same smoothing and mic position.
The blue line is an average of nine measurements before correction and it can be usefully and meaningfully compared to the green after correction line.

Those average graphs are useful in real life... the before and after correction graphs for the single individual positions are also accurate when present as in the standalone full Dirac Live version.

Flavio

[foggy1956]

Tony,
If you point me toward your REW tutorials I can play with them while waiting for my replacement emo mic. I already have the umik-1.
Thnx
Paul