My understanding of the SSW is that the test would not be valid if you
failed to use a properly calibrated system and failed to separate the
channels. I suppose you could use a stereo tape player with good channel
separation that was some how calibrated in HL in order control for
intensity. Hence, you need not use an audiometer but would need some type
of stereo system with known and controlled output levels.
The only central test I know of that doesn't require an audiometer is Dr.
R. Keith's SCAN (haven't seen the SCAN-A yet). This was constructed with
the idea that it could be administered in schools using a good quality
stereo tape player.
Central testing, while not hard, has a degree of variability that the
addition of more, avoidable, error is unwise and possibily unethical.
This might apply to adapting the SSW without first getting normative data
or taking other actions which are contrary to the basic premise or proper
administration of the test.