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Fountek FR88EX Fullrange

  • Wednesday, Jan 2, 2013
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Another popular choice for fullrange use, the Fountek FR88EX (PE Affiliate Link here) is tested and results provided below.

This is the slightly bigger brother of the FR89EX which I tested here.



Thiele-Small and Impedance Test Results

Electrical Parameters
Re 6.43 Ohm electrical voice coil resistance at DC
Le 0.042 mH frequency independent part of voice coil inductance
L2 0.299 mH para-inductance of voice coil
R2 2.53 Ohm electrical resistance due to eddy current losses
Cmes 170 µF electrical capacitance representing moving mass
Lces 12.96 mH electrical inductance representing driver compliance
Res 23.69 Ohm resistance due to mechanical losses
fs 107.2 Hz driver resonance frequency
Mechanical Parameters
(using test encl.)
Mms 2.979 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 2.898 g mechanical mass of voice coil and diaphragm without air load
Rms 0.739 kg/s mechanical resistance of total-driver losses
Cms 0.74 mm/N mechanical compliance of driver suspension
Kms 1.35 N/mm mechanical stiffness of driver suspension
Bl 4.185 N/A force factor (Bl product)
Loss factors
Qtp 0.581 total Q-factor considering all losses
Qms 2.714 mechanical Q-factor of driver in free air considering Rms only
Qes 0.737 electrical Q-factor of driver in free air considering Re only
Qts 0.579 total Q-factor considering Re and Rms only
Other Parameters
Vas 0.7827 l equivalent air volume of suspension
n0 0.126 % reference efficiency (2 pi-radiation using Re)
Lm 83.2 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 81.14 dB nominal sensitivity (SPL at 1m for 1W @ Zn)
Sd 27.34 cm² diaphragm area



Large Signal Analysis from Klippel LSI Module

Displacement Limits thresholds can be changed in Processing property page
X Bl @ Bl min=82% >3.5 mm Displacement limit due to force factor variation
X C @ C min=75% 2.4 mm Displacement limit due to compliance variation
X L @ Z max=10 % >3.5 mm Displacement limit due to inductance variation
X d @ d2=10% 9.6 mm Displacement limit due to IM distortion (Doppler)



Frequency Response

On-Axis merged at approximately 500hz, representing 2.83v/1m. 1/24 octave scaling.

Response comparison at 0, 30, and 60 degrees. 1/24 Octave resolution.



Harmonic Distortion

Note: This test was performed in the farfield, and subsequent to environmental issues such as reflections and noise. Therefore, fundamental response below 200hz is not provided here.

96dB/1m


Wrap-Up

Senstivity is rather low, in the low-to-mid 80’s. But that’s kind of expected out of a “fullrange” where sensitivity is sacrificed for linear excursion and high frequency extension. Increasing distortion levels at 96dB/1m equivalent below 300hz; use a proper crossover here to limit excursion and take some load off the voice coil so it doesn’t saturate and thusly become “compressed” (compressed = when the voice coil can’t expend heat and therefore as you increase the volume, the output level stops increasing and instead you lose volume). A few problematic distortion spikes but given their narrow band I can’t say how audible they would be without purposely listening to this speaker with test tones. IMD (intermodulated distortion) should be helped with the use of the inductance limiting shorting ring as evidenced by the symmetrical Le(x) plots. Frequenccy response is wrought with a lot of little things that concern me (e.g., multiple ups and downs from 100-1kHz, sharp dip at ~1600hz and the subsequent THD spike there, and the strong differences in on/off-axis response above 10khz (which kind of defeats the purpose of using a fullrange)).

Of course, one could simply use this as a dedicated midrange in a 3-way - maybe 300hz to 4khz - and for the price it might be worth that. But the low sensitivity still is a limiting factor.

Fundamentally, I’m not a proponent of fullrange or wideband drivers. I just prefer to use a 3-way than deal with the shortcomings of most fullranges; shortcomings being: low sensitivity, breakup issues outside of beaming that can’t be EQ’d or otherwise corrected via DSP. But if you have a need for one or want to experiment, this might be worth playing with since it’s pretty cheap, though, consider my comments above.



End

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