Bohlender Graebenar Neo10 Planar Transducer

A fellow on tech-talk sent me four of these drivers to test and check for consistency.  I normally don’t see the need but figured it’d be interesting so I obliged.

I tested each driver’s impedance, frequency response and relative harmonic distortion. I added each driver’s respective result to the same graph for comparison purpose.  I then chose one of the drivers to do further testing on.  So what we have is the typical suite of data plus unit-to-unit comparison data.  I hope you enjoy!


IMG_5354 IMG_5359


Driver Comparison Testing

Let’s first start with the comparison data. All four drivers were tested in the exact same fashion.  One was tested, then removed from the baffle and the next was added.  The mic never moved and all the impulse responses were windowed to the exact same time(s).  Therefore, the only variant in each test is the driver itself.

Impedance Comparison

As stated above, I received (4) of these drivers to test.  However, I didn’t sweep the first driver sample for impedance so there are only (3) samples in the impedance data.

BG Neo10 - Impedance Comparison


Frequency Response Comparison

The comparison testing for FR & HD was done at one-half meter, with 2.83v input signal.  The results on the FR below were each attenuated 6dB in order to provide a normalized 2.83v/1meter response SPL.

This response is in the horizontal plane only.  I did not test repeatability in the vertical plane.

Neo10 Frequency Response Comparison

Harmonic Distortion Comparison

Neo10 - Total Harmonic distortion Comparison

End of Comparison Testing….


Single Driver Testing:  Sample 3

After completing the comparison testing above, I chose Sample 3 to test further as it seemed to have the better response in FR and HD.  Yes, this is cherry picking but you’ve seen the variance above.

Thiele-Small Parameters

Electrical Parameters
Re 6.28 Ohm electrical voice coil resistance at DC
Le 0.006 mH frequency independent part of voice coil inductance
L2 0.01 mH para-inductance of voice coil
R2 0.29 Ohm electrical resistance due to eddy current losses
Cmes 1264 µF electrical capacitance representing moving mass
Lces 0.77 mH electrical inductance representing driver compliance
Res 1.1 Ohm resistance due to mechanical losses
fs 161.2 Hz driver resonance frequency
Loss factors
Qtp 1.194 total Q-factor considering all losses
Qms 1.403 mechanical Q-factor of driver in free air considering Rms only
Qes 8.032 electrical Q-factor of driver in free air considering Re only
Qts 1.194 total Q-factor considering Re and Rms only

Frequency Response: Horizontal Axis

Neo10 Horizontal Frequency Response 0 30 60

Frequency Response: Vertical Axis

Neo10 Vertical Frequency Response 0 30 60

Harmonic Distortion (Horizontal Axis)

Note the response rises throughout.  Therefore, the SPL level used to determine 96dB/1m was based on the fundamental mean SPL from 300hz to 5khz.  This is the same as I do on all my tests, albeit with some more wiggle room here by a couple dB.  Overall, this is comparable to my other test results.

Fundamental + Harmonic distortion components (96dB1m)

Cumulative Spectral Decay

Neo10 Cumulative spectral decay 2


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