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JBL Stage 125C Review (Center Speaker)

Rate this speaker:

  • 1. Poor (headless panther)

    Votes: 100 57.8%
  • 2. Not terrible (postman panther)

    Votes: 63 36.4%
  • 3. Fine (happy panther)

    Votes: 10 5.8%
  • 4. Great (golfing panther)

    Votes: 0 0.0%

  • Total voters
    173

amirm

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This is a review and detailed measurements of the JBL 125C home theater center speaker. It is on kind loan from a member and costs US $120 on Amazon currently.

The 125C really looks nice with the symmetrical what woofers:

JBL 125C Review Center Home Theater Speaker.jpg


Typical of some center speakers, it doesn't have a port (i.e. they think people will put them in cabinets):
JBL Stage 125C Review Center Home Theater Speaker.jpg


NOTE: our company, Madrona Digital is a dealer for Harman which includes JBL line. So feel free to read whatever level of bias you like in my subjective remarks.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the center of the tweeter (aligned by eye). It is getting colder with the measurement room temp at 16 degrees C. Accuracy is better than 1% for most of the range but drops to 2% for part of the spectrum.

JBL 125C Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

JBL 125C Measurements Frequency Response Center Home Theater Speaker.png


On axis response looks flat and good other than the sloping down woofer response. Lot of resonances are visible as is the directivity error. The latter messes up the early reflection measurements:

JBL 125C Measurements Early Window Frequency Response Center Home Theater Speaker.png


Combining the two we get our predicted in-room response which shows fair amount of coloration:

JBL 125C Measurements Predicted in-room Frequency Response Center Home Theater Speaker.png


Near-field response is not directly revealing of the design problem:

JBL 125C Measurements Near field frequency response center Home Theater Speaker.png


But the horizontal beam width is:

JBL 125C Measurements Horizontal Beamwidth  Center Home Theater Speaker.png


The two woofers fight with each other causing sharp narrowing of the response between 500 Hz and 3 kHz until tweeter takes over. For a center speaker, this is really bad as the coverage angle is as low as just 20 degrees.

Contour plot shows the same thing:
JBL 125C Measurements Horizontal Directivity Center Home Theater Speaker.png


These "MTM" designs are optimized for vertical usage and we see that in that orientation:

JBL 125C Measurements Vertical Directivity Center Home Theater Speaker.png


On the other hand, the two woofers provide ton of dynamics and power handling as seen in our distortion graphs:
JBL 125C Measurements THD Distortion center Home Theater Speaker.png


JBL 125C Measurements Distortion center Home Theater Speaker.png


Worst case impedance is 4.4 ohm which is not too bad:


JBL 125C Measurements Impedance and phase Center Home Theater Speaker.png


For the fans of timing analysis, here are the waterfall and impulse responses:

JBL 125C Measurements CSD Waterfall center Home Theater Speaker.png


JBL 125C Measurements Impulse Response center Home Theater Speaker.png


JBL 125C Listening Tests and Equalization
This section intentionally left blank.

Not feeling that great and can't make noises right now. So no listening results.

Conclusions
As if we needed to drill this message into our head strong and deep, we see that you can't easily build a proper 2-way speaker with symmetrical woofers on each side of the tweeter. Beam width narrows significantly causing issues for a center speaker in home theater which needs to cover a wide seating area. Response is not bad if you use this vertically. It is also better than JBL Stage 135C I reviewed recently.

I can't recommend the JBL Stage 125C based on these measurements. It is the wrong design for the job.
 

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pseudoid

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S.O.S.A.D. after day!
I think I saw an Instagram photo of the Headless PinkPanther and the last 3 tested Center speakers hanging out at the homeless shelter.
I can't imagine how much worse those "soundbars" must test and sound.
I don't know what all of these results might possibly indicate about those rear-firing 'noise-generators' inside all current TVs...
As if I needed more reasons to stick with a quality pair of floor-standing stereo speakers .
 

pierre

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Score is 2.3 and would go to 4.1 with the following EQ:

Code:
EQ for JBL Stage A125C computed from ASR data
Preference Score 2.3 with EQ 4.1
Generated from http://github.com/pierreaubert/spinorama/generate_peqs.py v0.14
Dated: 2021-12-01-07:37:44

Preamp: -4.2 dB

Filter  1: ON PK Fc   667 Hz Gain +3.99 dB Q 1.44
Filter  2: ON PK Fc  6372 Hz Gain -2.06 dB Q 0.72
Filter  3: ON PK Fc   171 Hz Gain -2.03 dB Q 2.41
Filter  4: ON PK Fc  1778 Hz Gain +1.98 dB Q 3.00
Filter  5: ON PK Fc  4473 Hz Gain -0.75 dB Q 3.00
Filter  6: ON PK Fc  7091 Hz Gain +0.64 dB Q 3.00
Filter  7: ON PK Fc   432 Hz Gain +0.53 dB Q 3.00

Graphically the EQ looks like:

filters_eq.png


and change the spin and PIR:

filters_spin.png
filters_pir.png


Hope it helps.
 
Last edited:

GD Fan

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Wow, interesting horizontal for a center speaker.
 

phoenixdogfan

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It even has that waveguide for all the good it's doing. The MTM configuration seems to be a prescription for this sick center channel response. Just what the Doctor didn't order for us or Amir.
 

bunkbail

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Does a pair of these make a good stereo speakers, if EQ'd that is?
 

Bjorn

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This is exactly why one is generally better off buying one front speaker and use it as a center rather then buying the "center speaker" from the brand. Obviously that would require using a sound transparent screen with the speaker behind it. With a TV it's often better to drop the center speaker, use broadband constant directivity speakers and just treat the early specular energy since the fronts are often close to side walls.
 

abdo123

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I mean broadband constant directivity speakers. ;) That can be achieved in several ways. A big horn design is just one way.
The only thing else i can think off is a Geddes speaker but with a much more bigger baffle. that sort of design would always need a crossover though.
 

Bjorn

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The only thing else i can think off is a Geddes speaker but with a much more bigger baffle. that sort of design would always need a crossover though.
That's not really a broadband directivity speaker. Besides it is type of horn speaker (waveguide=short horn profile). Anyway, that's a different topic and doesn't belong here.

My point is that using a center speaker with a directivity as poor as this, and which is the case with many center speakers, generally isn't necessarily better than dropping the center speaker all together. But in order for the image to be stable with only two front speakers, it's important with a uniform beamwidth and avoid early arriving reflections.
 
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