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CSS FR125SR Fullrange Speaker Driver

CSS FR125SR Fullrange Speaker Driver

Note - this driver has been discontinued and is no longer being produced. This pair of CSS FR125SR drivers (by Creative Sound Solutions) was won from a giveaway at Audio Junkies. The first thing that catches your eye with these drivers is their looks. These are sexy drivers! The next thing that caught my eye was the label on the driver that reads CSS FR125S? But I knew this was the FR125SR driver as it has four legs (the previous FR125S had six legs).

The CSS FR125SR is a 125 mm (5") fullrange driver that is listed by the manufacturer as having an Xmax of 6 mm. The FR125SR is constructed on a fairly open cast aluminum basket. The driver is shielded and consists of a curvilinear paper cone, rubber surround and a copper phase plug. My drivers did not come with a gasket or mounting screws. From the photos I have seen, I don't think that a gasket or mounting harware is supplied.

CSS FR125SR Fullrange Speaker Driver
CSS FR125SR Fullrange Speaker Driver

CSS FR125SR Fullrange Loudspeaker Driver
CSS FR125SR Fullrange Loudspeaker Driver

T/S Measurements - CSS FR125SR Driver

The first thing I check with all new drivers is the DCR of the voice coil. The best way to do this is by using a low resistance measurement jig as a typical handheld multimeter is not accurate when measuring low resistance. There was a difference of over 0.3 ohms between the two drivers. I measured the Thiele / Small Parameters of the CSS FR125SR drivers using the Dayton Audio Woofer Tester 3 (WT3). The measured parameters do not match with those published by the manufacturer nor with each other!

 Parameter   Manufacturer  Driver 1 Driver 2
Fs 70.0 Hz 78.7 Hz 67.3 Hz
Vas 5.98 L 3.10 L 4.72 L
Qts 0.59 1.02 0.82
Qes 0.72 1.31 1.05
Qms 3.37 4.53 3.75
Re 7.0 Ohms  7.53 Ohms   7.23 Ohms 
Le 0.35 mH 0.51 mH 0.47 mH
SPL 85.5 dB 82.6 dB 83.4 dB

T/S Parameters - CSS FR125SR Speaker Driver

Notes: measurements by using Dayton Audio Woofer Tester 3 at 22 Celsius.

Review - CSS FR125SR Speaker

On test baffles the difference in bass and SPL between the two was clearly audible. For that reason I did not figure there was any value in measuring the frequency response. Hopefully the problem is limited to this one pair of drivers, but we would love to hear from others who have measured this driver. Quality control issues with drivers from China are actually quite common on inexpensive speaker drivers, but this driver in not inexpensive. So how many of you are actually checking driver parameters before starting a project? Quite often just checking the DCR or inductance of a voice coil is enough to tell you something could be wrong.

Another issue noted with these drivers was the relative ease at which they bottom out. It seems that the strength of the XBL motor is easily able to surpass the excursion capacity of the suspension. This problem was present in both drivers and has also been observed by others, so the problem is not only limited to this set of drivers.

These are higher Q drivers and will work best on an open baffle with low frequency help. Sealed or aperiodic speaker enclosures with a simple baffle step correction circuit should also work.

The cost for the CSS FR125SR driver is $70US which seems high when you consider the build quality, limitations and performance. Lower cost and better performing fullrange drivers are the 4.5" Fostex FE127E ($45US, 0.7 mm excursion) and the 4" Dayton Audio RS100S-8 ($27US, 3.5 mm excursion). The price comparison is based on December 2008 pricing.

Datasheet - CSS FR125SR Speaker