This blog post features a full test on the Seas FA22RCZ 8" fullrange driver. Information on this driver can be found here.
Why the Seas FA22RCZ?
- Affordable
- Made in Norway
- Reasonable QTS for traditional reflex alignment bass cabinet
- Deep drawn copper cap on pole piece for reduced intermodulation distortion
- Open basket design with acoustically transparent spider
Measurements
Frequency Response
Mounted in my 50 liter mini-onken produces the following response. The response has a gentle rising response until we see a peak centered around 3kHz. I attempted to remove this peak with an LCR filter which I will talk about later in this blog post. Overall the rising response can be tamed with a traditional baffle step circuit.
Eventually I settled on a baffle step circuit comprising a 1.25mH air core inductor (16 gage) and a 4.7ohm resistor. I found that one could easily over do the baffle step compensation which killed the life of the sound. For example I found that a 8.2ohm resistor brought down the highs too much. Below is a comparison for reference between an 8.2ohm (grey) and 4.7ohm(red). The grey response curve lacked liveliness and had a less 'open' sound. One should definitely experiment between the different value resistors to achieve the overall subjective sound they are looking for. The inductor can be in the range from 1mH - 1.25mH.
LCR notch filter at 3kHz.
Implementing a notch at 3kHz improved the overall sound noticeably. Below is a comparison showing the effect of the notch filter. 
Below is a schematic of the circuit I settled on.
Burst Decay
Below is the burst decay response of the driver once the BSC and LCR were in place.
Impedance Sweep
Harmonic Distortion
Below is the harmonic distortion sweep at various SPL levels. This driver rewards with low distortion if listening below 80dB SPL.
75dB SPL at 1 meter:
80dB SPL at 1 meter:
85dB SPL at 1 meter:
90dB SPL at 1 meter:
Intermodulation Distortion
Below is the intermodulation distortion results when tested at various SPL levels starting at 75dB and rising to 95dB. I found that the Seas FA22RCZ achieves very low numbers if the output SPL does not exceed 75dB SPL at 1 meter, particularly in upper midrange and treble. For example 6.4kHz has an astonishing low distortion of only 0.073% IMD! It is not understood why there is a sharp peak in distortion at 583Hz at +85dB SPL however this does correspond to a impedance blip.
Off-Axis Polar Response
Subjective Listening Impressions
My initial impressions on the driver is that the highs sounded like a good dome tweeter. Further listening I concluded that it rivals some planar and ribbon tweeters. It does not have any of the harshness commonly associated with whizzer cones. The highs are where this driver shines. This is a pleasant surprise. The midrange has a liveliness that I was uncertain if I found this to be good trait or not. I wouldn't call it dynamic range, but more like 'good presence' in the vocal region. It's not shouty like some Fostex drivers. It has a somewhat pleasantly smooth character in the vocal range. The bass is the second greatest strength which is light and tuneful, and very closely tied to the rest of the frequency spectrum. I was achieving acceptable bass in my 50 liter onken cabinets.
Conclusion
The Seas FA22RCZ would serve well in small listening environments where low to moderate listening levels are required. It achieves audiophile sound quality but has some limitations with it's overall output capability. The Seas would be a good choice for anybody wanting to experience the charm the single driver genre has to offer.