Thanks to the dilligent efforts of several AVSForum members, a workaround has been discovered for previously-reported low bass issues on Toshiba's HD-XA2 HD DVD Player.
Back in March, Joshua Zyber noted in his High-Def Digest review of the Toshiba HD-XA2 that the HD DVD player had very low bass output when using the 5.1 analog audio connections. Since that time, Toshiba has released a couple of firmware upgrades to the player, primarily to resolve specific disc compatibility problems. While these updates have not completely fixed the audio issues mentioned in our earlier review, a temporary workaround for the low bass has been discovered in the most recent Firmware V1.6.
It turns out that the low bass is a symptom of defective speaker and bass management controls inside the player's audio decoder. For viewers with small main speakers who rely on the decoder to redirect bass from other channels to the subwoofer, the player wasn't making any adjustments no matter what settings were entered. Likewise, if an owner had no center channel and needed the dialogue redirected to the left and right front channels, that wasn't working either. As a result, only viewers with a complete set of full-range large speakers were hearing movie soundtracks properly.
Thanks to the thorough testing of AVSForum members MauneyM and others, it has been discovered that changing the "Digital Out SPDIF" setting in the player from Bitstream to PCM re-enables bass and speaker management over the analog audio connections. No, this doesn't make logical sense, as that setting should have no effect on the analog output. Nevertheless, users with small main speakers will find bass restored to the subwoofer channel as desired, with the caveat that ideally a 15 dB bass boost should be applied at the receiver, rather than the expected 10 dB.
The downside to this workaround is that, if you were actually expecting to use the SPDIF output to transmit a digital bitstream for some applications, you'll need to manually adjust that setting each time. There's no clear explanation for why the SPDIF setting would affect the speaker management controls for the analog output, and hopefully Toshiba will continue to work on this problem in future firmware updates. In the meantime, Josh has updated his High-Def Digest review of the HD-XA2 to reflect this new information.