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post #11 of 39 Old 07-10-16, 01:14 PM
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Re: Full range target curves

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Pio2001 wrote: View Post
By the way I've got a question. I read, and noticed, that it is better to equalize the lowest frequencies with both speakers active, because two independent correct equalizations don't sum up to give a correct one in stereo.
At what frequency should be the transition between common equalization (bass) and independent equalization (higher frequencies) ?
How far apart are the speakers? I would also use global EQ as you suggest, rather than independent CH.

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Thanks ajinfla,
About channel independence, I've run a small test : I turned my head to the left and the right while playing a sinewave with a software sine generator. It seems to me that the direction of the sound becomes perceptible between 70 and 100 Hz.
Try an impulsive signal instead, something with a sharp onset.

cheers,

AJ

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post #12 of 39 Old 07-10-16, 03:04 PM Thread Starter
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Re: Full range target curves

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How far apart are the speakers? I would also use global EQ as you suggest, rather than independent CH.
The speakers are 130 cm apart from each other.
I experimented with full stereo, partial stereo and full mono correction, but, except for the two peaks below 100 Hz, it seems that the result depends more on the way the corrections are made (they are manual above 100 hz) than on the stereo or mono choice.

Anyway there is not much difference in the left are right measurements above 100 Hz, as we can see looking at both curves, so it shouldn't matter.

Full range target curves-left_and_right.png

I'm currently satisfied with a set of filters that are identical below 100 Hz and different above. I'm currently tuning the general amount of bass with an extra low shelf filter of -2 dB starting at 200 Hz.

There was too much bass, but anything I do at and above 400 Hz to modifiy the target curve decreases the quality of the medium frequencies. I prefer not correcting anything above 300 Hz and deal with the bass level alone, which gives me a strange shaped house curve, with a small peak at 400 Hz.
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post #13 of 39 Old 07-10-16, 05:27 PM
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Re: Full range target curves


Quote:
By the way I've got a question. I read, and noticed, that it is better to equalize the lowest frequencies with both speakers active, because two independent correct equalizations don't sum up to give a correct one in stereo.
As far as I know that doesnít apply for main-channel speakers so much as people using multiple subwoofers in different locations. Iíve had good luck equalizing the lower frequencies of bookshelf-sized speakers.


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At what frequency should be the transition between common equalization (bass) and independent equalization (higher frequencies) ?
I would recommend matching EQ above ~400 Hz. Indepent EQ above that point does weird things to the imaging. If thatís what youíve been doing, it could account for your not being happy with your results in that range.

Regards,
Wayne




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post #14 of 39 Old 07-10-16, 06:15 PM Thread Starter
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Re: Full range target curves

Ah thanks,

Here are the filters I'm currently using. It should be ok as long as mono / stereo is concerned.

Filter #1 and #2 have been generated by the software from the measurements made with both speakers, then copied here.

Full range target curves-17-filters-left.png

Full range target curves-18-filters-right.png
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post #15 of 39 Old 07-10-16, 08:30 PM
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Re: Full range target curves

Pio,
I am curious to look at the phase relationship between L and R. Do you mind posting the .mdat?
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post #16 of 39 Old 07-11-16, 05:55 AM Thread Starter
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Re: Full range target curves

Oops ! I completely forgot about phase !

Here is the file. I've removed all individual measurements to make it smaller to upload.
The filters used are the ones that are active in the L and R measurements (Left and Right). The inactive filters are obsolete.
The St measurement (left + right speakers) is no more used.
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post #17 of 39 Old 07-11-16, 08:45 AM
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Re: Full range target curves

The attached file contains averages. They do not include the IR and thus no phase information. I was looking for 2 single sweep measurements at the LP; one each of the L and R mains. I just thought you may have that at hand.

From the discussion, I was just thinking of the common situation in the 200-800 Hz range where is difficult or inadvisable to EQ due to possibly creating more issues than resolving. I was just interested in seeing if you have as much trouble with strong reflections in this area as I do. I don't anticipate there is any helpful info to be found that would suggest a best EQ approach for in that range. I am on board with the general thoughts above regarding whether to / how to EQ in this area. It was just more for my continued learning.
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post #18 of 39 Old 07-11-16, 01:52 PM Thread Starter
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Re: Full range target curves

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jtalden wrote: View Post
The attached file contains averages. They do not include the IR and thus no phase information. I was looking for 2 single sweep measurements at the LP; one each of the L and R mains. I just thought you may have that at hand.
Sweep measurements or impulse measurements ?
I didn't do impulse measurements. How do you do this, in two words ?

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I was just interested in seeing if you have as much trouble with strong reflections in this area as I do.
I'm sure I do. Ceramic floor, concrete ceiling and a bare concrete wall 50 cm on the left of the left speaker ! These solid surfaces absorb no acoustic energy. The sound completely bounce back on them.
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post #19 of 39 Old 07-11-16, 02:49 PM
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Re: Full range target curves

I was just looking for 2 sweep measurements. Don't go to any trouble. It was just a thought.

To explain:
Given a normal sweep measurement, REW automatically calculates the IR and thus the phase trace is available. If several sweeps are taken in the listening area and the 'Average the Responses' button is selected then the IR/Phase data is lost in the average, i.e., the SPL alone is averaged without regard to the IR/phase of the original sweeps.

It is possible to manually average several sweep measurements in REW using 'Trace Arithmetic'. That process will retain the IR/phase data in the resulting average, but that is quite a bit more complicated to do. It is also considered unnecessary for the purposes of EQ. It does have other uses however.
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post #20 of 39 Old 07-11-16, 05:08 PM Thread Starter
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Re: Full range target curves

Aaah Ok.

Here are the individual measurement for the center front listening position (attached file at the bottom of the message). I don't know how to interpret the phase.

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Don't go to any trouble. It was just a thought.
I'm interested in any info. I've just received my MiniDSP, so I could easily perform a measurement with the correction loaded. Here is the result :

Full range target curves-19-final-ls-3.png

A huge bump at 300 Hz. I then went into new trials to see if I could get something more balanced, but if I try to remove the bump, it doesn't sound right. I just rose the low shelf from -3 dB to -2 dB to get a bit more bass below 200 Hz.

My hypothesis, for the time being, is that the excess at 300 Hz comes from reflections in the room, and if I try to equalize them, the direct sound becomes unnatural. I've read that we can, rather unconciously that conciously, distinguish the direct sound from the reflections (through directional clues, and precedence effect / masking). The microphone doesn't distinguish between them. It records the sum of everything.

It would mean that this bump would sort of "sounds right" as long as real audio sources would be expected to sound this way in my living room.

It could also mean that I did it all wrong from the beginning

Time will tell. I can't stand unbalanced sounds for a long time. If something is really wrong, I should get tired of it after some days.
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