Martin Poulin
Feb 2022,
I just bought a pair of BMS 4596C, the predecessor of the current model, the 4596ND. They are exactly the same part as for the new model number, BMS only changed the last letter to reflect the fact that they feature a Neodymium magnet.
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The reason I bought them is because people online claim they can play lower and can be crossed as low as 300 Hz compared to my Radian 950PB that can only reach around 480 Hz on my 340 Hz JMLC horn. The datasheet BMS provide claim 200 Hz to 9000 Hz useable frequency range, not even close to be the case I found out. As usual, manufacturers are stretching the truth.
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I was extremely surprised to find that when I measured the BMS 4596ND, at 1 meter distance in my system, they performed about 96% IDENTICAL to my Radian 950PB on the frequency response graph!!! And I must add that the 950PB is measuring better on about every other parameter but the efficiency. The BMS does have about 2.5 Decibels more output than the 950PB for the same input power. (Both drivers are 8 Ohms).
Closely matched at 100 dB at 1 kHz at 1meter. Of course, no EQ was used for the measurement and I've only measured on axis.
-BMS 4596 in red green
-Radian 950PB in red
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IDENTICAL frequency response from 300-1500 Hz...
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-950PB breakup can be seen at about 14.3 kHz.
-4596 real issues can be seen at low as 8.7 kHz
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It is worth mentioning that I use those big compression driver only up to ~2 kHz as smaller 1 inch CD effortlesly outperform any of them above ~2 kHz. Or maybe about 2.4 kHz depending on the driver and horn combo used.
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-BMS 4596 in green
-Radian 950PB in red
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-Similar step response.
-you can see that the 950PB has less overshoot and hense stop moving a tad faster than the BMS 4596ND.
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I highly doubt that such difference is audible.
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-BMS 4596 in green
-Radian 950PB in red
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-Much lower distortion on the Radian 950PB than the 4596ND across the useable range.
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-BMS 4596ND distortion profile
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-Radian 950PB distortion profile
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-Much lower 2nd harmonic content across all of the useable range.
-Lower 3rd harmonic content except for the small peak at 600 Hz.
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-BMS 4596ND spectrogram
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-some stored energy can be seen at 2 kHz.
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-Radian 950PB spectrogram
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-small breakup seen at 14 kHz.
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-BMS 4596ND waterfall
Measurement setup
Subjectively, I had a HEAVY bias against the BMS as I didn't cared much for the other 2 ring radiators I previously evaluated in my system. The only point I was looking for was for a lower useable frequency of maybe 400 Hz. The driver low frequency being limited by the cutoff of my 340 Hz horn.
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On this aspect, the BMS disapointed me big time. The BMS lack of high frequency extension mandate a 3 or a 4 way design too, not easy if you intend to use it with a traditional passive crossover.
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I quickly listened to the 4596ND in mono and did a quick comparison against my Radian 950PB.
I used 440 Hz to 2.8 kHz crossover point for both. After some rough DSP adjustment, they sound vastly similar yet slightly different. The BMS seem to have a tad less resolution or as some people say it, it sound more relaxed. I mean relaxed only if you can compare it directly against the 950PB, the BMS is still an excellent product.
The difference is small, much smaller than I anticipated despite very different construction.
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Since I have three Radian 950PB on my front 3 channels, I've decided to keep the 950PB for the front duty.
The 4596ND will be used in my 7.1 system as rear channel.
My side channel will end up being the Radian 760NEOPB.
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-BMS 4596ND already mounted on my 350 Hz tractrix horn.
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- I can cross the rear channel horn much lower with the BMS than the 760NEOPB was capable of.
-All is not lost, I keep the BMS in my system, just not in the main spotlight.