Filter Settings

[Teddy Ray]

I've noticed some CDs that cause large subsonic woofer excursions. One clear example is Stevie Wonder "A Time to Love".a substantial amount of subsonic ringing throughout///

Looks by eye to be close to 1 Hz.


Anyone else notice it on this particular CD or any others?

Seems a good 10 Hz subsonic filter would help with this waste of power and excursion. Who'd have thought one would be needed with CDs?



With LP the low frequency content is cut in the mastering process in order to increase recording time by reducing the groove width The noise signal - warp is introduced in the playback process and there is obviously nothing in the production phase that can eliminate the warp noise signal.

It is also well know that there are very low frequency sources such as vocal pops, string plucks and pops that need to be filtered to provide a reasonably band limited signal for playback. Digital formats have no noise source such a warp in the playback path and therefore why not digitally high pass filter the final digital data at say 10 Hz? The cutoff could even be specified depending on the program content. I understand that a few sound tracks have 10 to 12 Hz real content, perhaps even one with 8 Hz.
This would eliminate the need for a subsonic filter in the playback path. Indeed, how many preamps have a subsonic filter in the line stage path, if they have one at all?

I'd still like to know where this noise came from:
http://baselaudiolabs.googlepages.co...FREQ-NOISE.png
Looks like the channel with the noise had some clipping on the negative going cycle right before the LF noise, perhaps a poorly designed DC servo thrown off by the overload?

Why not add a digital high pass filter to standard processing for commercial CDs?

[Ben B]

Originally Posted by Teddy Ray

I've noticed some CDs that cause large subsonic woofer excursions. One clear example is Stevie Wonder "A Time to Love".a substantial amount of subsonic ringing throughout///

Looks by eye to be close to 1 Hz.


Anyone else notice it on this particular CD or any others?

Seems a good 10 Hz subsonic filter would help with this waste of power and excursion. Who'd have thought one would be needed with CDs?



With LP the low frequency content is cut in the mastering process in order to increase recording time by reducing the groove width The noise signal - warp is introduced in the playback process and there is obviously nothing in the production phase that can eliminate the warp noise signal.

It is also well know that there are very low frequency sources such as vocal pops, string plucks and pops that need to be filtered to provide a reasonably band limited signal for playback. Digital formats have no noise source such a warp in the playback path and therefore why not digitally high pass filter the final digital data at say 10 Hz? The cutoff could even be specified depending on the program content. I understand that a few sound tracks have 10 to 12 Hz real content, perhaps even one with 8 Hz.
This would eliminate the need for a subsonic filter in the playback path. Indeed, how many preamps have a subsonic filter in the line stage path, if they have one at all?

I'd still like to know where this noise came from:
http://baselaudiolabs.googlepages.co...FREQ-NOISE.png
Looks like the channel with the noise had some clipping on the negative going cycle right before the LF noise, perhaps a poorly designed DC servo thrown off by the overload?

Why not add a digital high pass filter to standard processing for commercial CDs?

It is often done.

-Ben B

[dcollins]

Originally Posted by Teddy Ray

Seems a good 10 Hz subsonic filter would help with this waste of power and excursion. Who'd have thought one would be needed with CDs?

For LP's it should be part of the reproduction.

You obviously have different things in CD (like the response can actually extend to DC) but a HPF can always free up power for frequencies that you can hear.

There is also a FM effect of rumble modulations in the speaker, I guess.

I'd still like to know where this noise came from:
http://baselaudiolabs.googlepages.co...FREQ-NOISE.png
Looks like the channel with the noise had some clipping on the negative going cycle right before the LF noise, perhaps a poorly designed DC servo thrown off by the overload?

There could be many sources. Even an upset in the operating point bias in a poorly designed stage.

Why not add a digital high pass filter to standard processing for commercial CDs?

Well, not "standard" but the filter can definitely help if needed.


DC