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Phase Tech PC 3.1 Speaker Measurements

amirm

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These are the measurements of a used/vintage Phase Tech PC 3.1 center speaker. I believe it originally cost US $600. I was kindly sent to me by a member:
Phase Tech PC 3.1 Center Speaker 3-way Review.jpg

As you can see, the sample is a crusty one! :) I must say, I had not seen foam over woofers before. You can rotate the midrange/tweeter assembly as to use the speaker vertically.

Owner told me that this was one of the companies paying attention to directivity as being an important thing. Seeing how it has a mid-range, gives me hope that it delivers on that.

These write-up is rather brief because I am not sure if I have a working sample. I cannot find any measurements of this unit. There is some for the version 2 which looks better.

Phase Tech PC 3.1 Speaker Measurements
Our anechoic frequency response shows clear problem where the mid-range is supposed to be delivering:
Anechoic CEA2034 Frequency Response.png

From memory, the midrange is crossed from 700 Hz. That would in theory fill that hole but maybe they wanted this kind of V shaped response. Besides that, we have a few wide resonances. Directivity is not great causing early window and predicted in-room responses leaving something to be desired:
Phase Tech PC 3.1 Center Speaker 3-way early window frequency response Measurements.png

Phase Tech PC 3.1 Center Speaker 3-way Predicted In-room frequency response Measurements.png


As noted, the mid-range should be solving the beaming issue with dual drivers but it clearly is not:
Phase Tech PC 3.1 Center Speaker 3-way horizontal directivity Measurements.png

Phase Tech PC 3.1 Center Speaker 3-way horizontal beam width Measurements.png


Vertically of course doesn't have that problem:
Phase Tech PC 3.1 Center Speaker 3-way vertical directivity Measurements.png


I was surprised and dismayed that I could clearly hear distortion at 94 dBSPL:
Phase Tech PC 3.1 Center Speaker 3-way distortion Measurements.png


Phase Tech PC 3.1 Center Speaker 3-way distortion THD Measurements.png


This is topped by very low impedance:
Phase Tech PC 3.1 Center Speaker 3-way impedance phase Measurements.png


Finally, waterfall shows resonances as we would expect:
Phase Tech PC 3.1 Center Speaker 3-way CSD Waterfall Measurements.png


Conclusions
It should be obvious that this is either a broken speaker or broken by design. I can't be sure which is which. Could have discarded the measurements but after all the work that went into it (including confirming that the midrange was working), I thought I post it anyway.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Attachments

  • Phase Tech PC 3.1.zip
    61.3 KB · Views: 39
Here is my take on the EQ.
Please report your findings, positive or negative!

For the score rational your journey starts here
Explanation for the sub score
The following EQs are “anechoic” EQs to get the speaker right before room integration.
If you able to implement these EQs you must add EQ at LF for room integration, that is usually not optional… see hints there.

The raw data with corrected ER and PIR:

Score no EQ: 3.0
With Sub: 4.9

Spinorama with no EQ:
  • not linear at all
  • some directivity errors
  • SOme do it much better

Phase Technology PC 3.1 No EQ Spinorama.png

Directivity:

Better stay at tweeter height
Horizontally, on axis.

Phase Tech P C3.1 2D surface Directivity Contour Only Data.png


EQ design:
I have generated two EQs. The APO config files are attached.
  • The first one, labelled, LW is targeted at making the LW flat
  • The second, labelled Score, starts with the first one and adds the score as an optimization variable.
  • The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose.
  • With some SPK/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
Score EQ LW: 5.9
with sub: 7.6

Score EQ Score: 6.5
with sub: 8.3


Code:
Phase Technology PC 3.1 APO EQ LW 96000Hz
March202025-142326

Preamp: -5.00 dB

Filter 1: ON HPQ Fc 43.3 Hz Gain 0.00 dB Q 1.89
Filter 2: ON PK Fc 132.8 Hz Gain -3.38 dB Q 0.78
Filter 3: ON PK Fc 482.3 Hz Gain -1.02 dB Q 1.25
Filter 4: ON PK Fc 1160.2 Hz Gain 5.32 dB Q 0.98
Filter 5: ON PK Fc 2359.2 Hz Gain -3.97 dB Q 2.13
Filter 6: ON PK Fc 2790.0 Hz Gain 3.25 dB Q 1.67
Filter 7: ON PK Fc 4415.7 Hz Gain -3.31 dB Q 2.10
Filter 8: ON PK Fc 9745.6 Hz Gain 2.94 dB Q 2.80
Filter 9: ON PK Fc 11001.6 Hz Gain -6.40 dB Q 3.76

Phase Technology PC 3.1 APO EQ Score 96000Hz
March202025-142326

Preamp: -5.10 dB

Filter 1: ON HPQ Fc 43.3 Hz Gain 0.00 dB Q 1.89
Filter 2: ON PK Fc 130.8 Hz Gain -3.38 dB Q 0.90
Filter 3: ON PK Fc 488.0 Hz Gain -1.37 dB Q 1.87
Filter 4: ON PK Fc 1209.5 Hz Gain 6.00 dB Q 0.93
Filter 5: ON PK Fc 1772.6 Hz Gain -2.34 dB Q 2.09
Filter 6: ON PK Fc 2423.9 Hz Gain -3.32 dB Q 2.24
Filter 7: ON PK Fc 2997.2 Hz Gain 3.59 dB Q 2.06
Filter 8: ON PK Fc 4391.2 Hz Gain -3.53 dB Q 1.47
Filter 9: ON PK Fc 9243.8 Hz Gain 2.03 dB Q 3.70
Filter 10: ON PK Fc 10972.5 Hz Gain -5.98 dB Q 2.69

Phase Technology PC 3.1 EQ Design.png

Spinorama EQ LW
Phase Technology PC 3.1 LW EQ Spinorama.png


Spinorama EQ Score
Phase Technology PC 3.1 Score EQ Spinorama.png


Zoom PIR-LW-ON
Phase Technology PC 3.1 Zoom.png


Regression - Tonal
Phase Technology PC 3.1 Regression.png


Radar no EQ vs EQ score
Large improvements?
Phase Technology PC 3.1 Radar.png

The rest of the plots is attached.
 

Attachments

  • Phase Technology PC 3.1 APO EQ Score 96000Hz.txt
    578 bytes · Views: 24
  • Phase Technology PC 3.1 APO EQ LW 96000Hz.txt
    524 bytes · Views: 20
  • Phase Tech P C3.1 2D surface Directivity Contour Data.png
    Phase Tech P C3.1 2D surface Directivity Contour Data.png
    439.3 KB · Views: 24
  • Phase Tech P C3.1 3D surface Vertical Directivity Data.png
    Phase Tech P C3.1 3D surface Vertical Directivity Data.png
    411.1 KB · Views: 23
  • Phase Tech P C3.1 3D surface Horizontal Directivity Data.png
    Phase Tech P C3.1 3D surface Horizontal Directivity Data.png
    436 KB · Views: 22
  • Phase Tech P C3.1 Normalized Directivity data.png
    Phase Tech P C3.1 Normalized Directivity data.png
    435.6 KB · Views: 25
  • Phase Tech P C3.1 Raw Directivity data.png
    Phase Tech P C3.1 Raw Directivity data.png
    621 KB · Views: 23
  • Phase Tech P C3.1 Reflexion data.png
    Phase Tech P C3.1 Reflexion data.png
    215.9 KB · Views: 28
  • Phase Tech P C3.1 LW data.png
    Phase Tech P C3.1 LW data.png
    235.4 KB · Views: 24
Last edited:
Using a 1.5" mid with a 1" tweeter is honestly a bit weird. A 2" mid + .75" tweeter could achieve a lower woofer crossover point and better high frequency extension.

The foam in the woofers I believe is intended to mitigate high order distortion products. It does technically work but is a bit pointless when the rest of the speaker is a distortion/resonance factory.
 
Using a 1.5" mid with a 1" tweeter is honestly a bit weird.
That was my thought as well as I was typing the review. Likely they crossed the midrange too high due to it being so small.
 
It should be obvious that this is either a broken speaker or broken by design. I can't be sure which is which. Could have discarded the measurements but after all the work that went into it (including confirming that the midrange was working), I thought I post it anyway.
What motivated you to measure the speaker, Amir?
 
This is surprising to me how badly these performed. I had their PC80/90 Sub/Sat system (Bought some 30+ years ago) and as I recall, were a wonderful performer.
999phasetech80.jpg
 
This is surprising to me how badly these performed. I had their PC80/90 Sub/Sat system (Bought some 30+ years ago) and as I recall, were a wonderful performer.
View attachment 437679
Life was more beautiful 30 years ago. We were young, believing in cables, tubes, high end brands. Amir destroyed our dreams and now we buy Fosi equipment.
 
Avrei potuto scartare le misurazioni, ma dopo tutto il lavoro che ci è stato fatto (incluso il confermare che la fascia media stava funzionando), ho pensato di pubblicarlo comunque.
You did well to keep the work and publish it. Add a piece to the knowledge of this world, Even if the "happy panther" does not appear. Thanks Amirm for the test, always interesting.
 
Does the very low impedance dips suggest the speaker might not be working properly?

Why design a centre speaker that tortures AVRs?
 
Likely they crossed the midrange too high due to it being so small.
And, going by the distortion graphs, the midrange still is decidedly unhappy. It would have needed a substantially larger waveguide at the very least.

The foam in the woofers I believe is intended to mitigate high order distortion products.
Should help address breakup modes as well. It's basically an additional 1st-order lowpass.
 
IIRC, Bill Hecht the founder of Phase Tech is credited with the invention of the soft dome tweeter. Was patented in ‘67.
I guess he was tired of the hard dome tweeters getting pushed in bu people in the showroom, so he did a mockup of the tweeter using fabric. To his amazement, it sounded great and here we are now!
 
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