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JBL 305P mkII equalization

QMuse

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For equalization in room

Right indeed. But here we were speaking about checking the speaker's correction filter which has to be done with pseudo-anechoic measurement and that can be done only with gated sweep measurement as you can't gate MMM.
 

akarma

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which has to be done with pseudo-anechoic measurement and that can be done only with gated sweep measurement as you can't gate MMM.

MMM is accurate enough to 600-700hz. I can't see significant sense in gated sweep in EQ real sweetspot
 
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Pio2001

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I agree, you probably moved the hand at the end of the measurement. Try repeating it several times and apply averaging.

The pink curve is not a measurement. It is the cyan curve applied to the purple one directly in the software.
It looks like a bug in the software.
 

QMuse

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MMM is accurate enough to 600-700hz. I can't see significant sense in gated sweep in EQ real sweetspot

I think you're missing the point what he was doing - he wasn't trying to do room EQ but to check the efficieny of the speaker's correction filter he built based on Klippel's measurement. For that he needs to do pseudoanechoic sweep measurement with gating to eliminate reflections.

Regarding RTA measurement with pink noise - it is as accurate as sweep through the entire audio range. Whoever thinks different should mount mic on a stand, do both measurements and compare them.

MMM is only a method of averaging RTA pink noise measurements, same can be done with sweeps but it takes much more time.
 

QMuse

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The pink curve is not a measurement. It is the cyan curve applied to the purple one directly in the software.
It looks like a bug in the software.

Ahh, ok, I see now what you mean. Yes, it looks like a bug. Can you please show a snapshot of the filter screen?
 

Jon AA

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It's better to use MMM technique
Yeah, I'm a little worried about people getting carried away with that technique and misapplying it.... I saw a guy on youtube using it to measure a speaker from about a foot away, making about a 1 foot circle with his hand...naturally, only picking up off-axis sound.
 
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Pio2001

Pio2001

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Ahh, ok, I see now what you mean. Yes, it looks like a bug. Can you please show a snapshot of the filter screen?

I found what's the problem, and how to work around it. People using more recent versions of REW should test the following (I'm using this old version because more recent version can't display waterfalls on my system).

Open a measurement that includes a microphone calibration, but no equalization.

01.png

Open the EQ panel. Load some EQ settings previously saved on the hard drive.

02.png

In the EQ panel, the predicted frequency response is wrong. It is displayed without the mic calibration.

03.png

In the main window, open the Change calibration dialog for this measurement, and click Clear cal

04.png

The calibration is removed from the frequency response. The EQ panel now shows consistent data.

05.png

Go back in the Change calibration dialog. Reload the calibration.

06.png

Now, in the EQ panel, both curves are displayed properly.

07.png
 

QMuse

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I found what's the problem, and how to work around it. People using more recent versions of REW should test the following (I'm using this old version because more recent version can't display waterfalls on my system).

Open a measurement that includes a microphone calibration, but no equalization.

View attachment 53684

Open the EQ panel. Load some EQ settings previously saved on the hard drive.

View attachment 53685

In the EQ panel, the predicted frequency response is wrong. It is displayed without the mic calibration.

View attachment 53686

In the main window, open the Change calibration dialog for this measurement, and click Clear cal

View attachment 53687

The calibration is removed from the frequency response. The EQ panel now shows consistent data.

View attachment 53688

Go back in the Change calibration dialog. Reload the calibration.

View attachment 53689

Now, in the EQ panel, both curves are displayed properly.

View attachment 53690

When you export IR from REW it will also be without mic cal data although it is shown with it. That means when you export IR and import it back it will look different. Look here for the offical explanation.
 

Jungstar

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Noob here. Having 2 x 308p MK II + sub JBL LSR 310s running unbalanced through the Sub and into the speakers. There is a fixed 80 Hz crossover.
I'm far from room adjustments. But I like the "upper mids" much better in my $300 usd Headphones and I feel like there is something off in settings. Soft songs and deep sounds, bass etc are great, but too much bells, high hat etc sounds aweful.

Can someone give a simple rule of thumb about setting the "correct" settings on the Sub and Speakers.
Speakers has: Boundary EQ (-3, -1.5, 0) and HF Trim (-2, 0,+2). There is also the Input Sensivity of +4 or -10.

Mine are 20 cm from a wall.
 

daftcombo

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Hi,
After reading the review of the JBL 305P mkII speaker (that I own), I decided to try and equalize them according to the measurements that were published.

The two conditions for the equalization to succeed were that the directivity indices are smooth, and that my own pair sounds exactly the same as the one measured by Amir.

We can see in the review that the first condition is met, and that these speakers are good candidates for equalization.
The second condition seems to be fulfilled according to my own measurements (see my post here with the curves : https://www.audiosciencereview.com/...pro-monitors-review.10811/page-19#post-302946 )

I thus generated a set of eq filters in the REW software that should compensate for the JBL's frequency response, as measured by Amir (on-axis and listening window curves).
Here is the equalization curve that I managed to generate. It is displayed upside down, and I have overlaid it on Amir's graph. It is the light blue curve. I am very happy with the accuracy that I got while playing manually with all the PK coefficients, just looking at Amir's picture.
I didn't set any correction above 14 kHz for the time being, as I am completely deaf above 13.5 kHz anyway.

View attachment 45745

Once applied to the speakers, it sounds... a bit weird.

I then measured the frequency response before and after the correction from the listening position. I use the moving microphone method for this purpose, drawing the cumulated RTA of a Pink periodic noise.
Unfortunately, I can't measure the windowed response of the speaker alone, as I can't apply the correction to the REW signal. I can only apply it to music played by the Foobar2000 software player, with its convolver plugin. What we see here is the room curve in addition to the speaker curve :

View attachment 45738

The left part of the curve, up to 500 Hz, can be ignored. It represents the room's response rather than the speaker's response, with a correction setup for the Neumann KH-120 monitors, that are front vented, while the JBL are rear-vented.
The right part, from 1000 Hz to 20000 Hz, is supposed to decrease gently as the frequency goes up, as expected in any room.

View attachment 45739

Oops ! My correction obviously created some problems that were not there to begin with. Let's compare this curve with the correction itself :

View attachment 45740

The part around 500 Hz is difficult to interpret. On one hand, it looks like the correction is too strong, but on the other hand, this frequency range is supposed to by higher than the treble frequencies, measured from the listening position. Let's put it aside. The real problem is obvious : from 4000 Hz and up, the correction is useless. The original curve was neutral and didn't need any correction.

Let's drop this part from the eq and keep only the useful corrections, up to 4000 Hz.

Making a "half correction" is something very difficult, because there is no reference level for the part that is not corrected. In my first try, I just naively drew a straight line from 4000 Hz upwards. But the result didn't sound good. The treble were muffled. I realized that I had not calculated any target level for the part that is above 4000 Hz.
So I went back to Amir's graph, and tried to evaluate the average level measured above 4000 Hz. I restricted my reading to the 5000 to 15000 Hz range, ignoring what's happening above. I tried to draw a straight line so that half of the curve is above, and half is below. Then I noticed that this level was exactly the same as the 150 Hz peak. That would be my reference point.
Reading now my REW correction overlaid on Amir's graph, I noticed that it was accurately following it at 150 Hz. I therefore set the shelf level of my correction above 4000 Hz exactly identical to my 150 Hz peak (I mean 150 dip, since the curve is displayed upside down).

View attachment 45741

I generated the impulse response of the new correction and loaded it in Foobar's convolver and... wow ! Now, that sounds really great !!!

Here is how it measures from the listening position :

View attachment 45742

When I say it sounds great, I'm talking about medium and high frequencies. The low frequencies need re-equalization, as the bass reflex of the JBL is on the back of the speaker, and the MiniDSP room correction (still active from 35 to 600 Hz) was setup for the Neumann.

The measurement shows yet a little problem around 1000 Hz that was not there before correction. Here is the response without eq, the final correction, and REW's prediction of the result.
View attachment 45743

We can see that the level is unduly decreasing from 1000 to 1400 Hz, while it was not the case before correction.
Comparing with the first picture with Amir's graph, we can see that the correction is supposed to be ok. Since I'm not sure what's happening here, I didn't try any other adjustment.

The forum doesn't allow audio nor binary attachments, so here are links to my correction :

44100 Hz impulse response for convolvers : JBL 305P mk2 equalization.wav
Eq filters for REW : JBL 305P mkII eq filters.req

Important :
The correction is valid for JBL 305P mkII speakers, not for regular LSR 305 speakers.
The impulse response works at 44100 Hz only. The convolver must be preceded by a 44100 Hz resampler, or have a built-in resampler. Otherwise, if a file with a sampling frequency different from 44100 Hz is played, the correction will be wrong.
Could you just copy/paste the EQ settings in the form of a picture please?
 

treasury

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Equalizer APO configuration file for the JBL 305P MkII

How to install:
1. Add an include block in the Configuration Editor by +/Control/Include
2. Click on the blue folder with a document button in the include block and select this configuration file
3. Open the configuration with the green up arrow
4. Click on the "Change" button at Selected devices at the top and select the output device which drives your JBL 305P MkII.

The content of the attached .txt file:
Device: Speakers AudioQuest DragonFly Red v1.0 {75177ed7-ffad-4972-8509-2d0a6c926ab0}
Filter: ON PK Fc 152.5 Hz Gain -3.4 dB Q 0.65
Filter: ON PK Fc 245 Hz Gain 0.7 dB Q 3
Filter: ON PK Fc 794 Hz Gain -1.2 dB Q 4
Filter: ON PK Fc 970 Hz Gain -0.6 dB Q 4
Filter: ON HS Fc 1000 Hz Gain -3.3 dB
Filter: ON PK Fc 1199 Hz Gain 0.5 dB Q 6
Filter: ON PK Fc 1438 Hz Gain -1.2 dB Q 6
Filter: ON PK Fc 1767 Hz Gain -3.2 dB Q 6
Filter: ON PK Fc 3208 Hz Gain -1.8 dB Q 5
Filter: ON PK Fc 14578 Hz Gain -1.9 dB Q 2
 

Attachments

  • JBL305pMk2.txt
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Pio2001

Pio2001

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Hi,
The topic was not discussed in this thread, but JBL 305P mkII are very inconsistent from one copy to the next.

I have measured separately my left and right speakers, and there are some differences up to 4 dB in their frequency response above 1000 Hz, with several peaks.

In order to equalize these speakers, it is necessary to measure them one by one.
 

akarma

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Yep it is true. No one selects speakers in pair when selling
 
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