Subsonic filter, stereo myth?

When I got my Yamaha integrated solid state amp/pre-amp in 1983, it didn't have a switch for subsonic filter, like my friend's Yamaha that he got a year later. I found out I could add an external one to the interconnect, so I did, a Nakamichi SF-10.

From the instructions:

"Inaudible subsonic noise below 10 Hz is produced by turntable rumble, tonearm resonances or when playing back warped records, etc. If such subsonic signals are recorded on a tape deck, they can cause modulation of the playback signal, which will be heard as sound fluctuations similar to flutter effects. The SF-10 is an add-on subsonic filter which cuts off any harmful noise elements and permits clear recording and playback."

"Connect the SF-10 between the line input terminals of the tape dec and the Rec output terminals of the amplifier...."

"Filter Characteristics: 10 Hz: - 10 dB"

I guess I was most impressed not by what I heard, but by attaching the plugs and getting rid of the incredible movement on the woofers I'd get when playing the first cut of a warped album, warped albums being the norm during this time. Those woofers would move more than an inch, with no music pumping them, and the filters cut this way down, to just a murmer.

Spring forward to this coming weekend, when these filters are now between my amp and CD-R recorder, and I'm going to replace my 1M Monster Cable M550i interconnects with my newly purchased .5M Grover interconnects. And it occurred to me that I ought to rethink keeping these filters on the line.

The original thought was filter out harmful subsonics created by warp, protect my speakers. Now I'm thinking, hey, this subsonic filter is affecting the signal I'm trying so hard to correctly reproduce, take it out of the line, the warp won't hurt anything, this was just sales myth.

What say you?

 

Don't most records -- with the exception of certain classical and contemporary dance releases -- have everything below 20Hz filtered out at the mastering stage? Correct me if I'm wrong, but I routinely filter out everything below 30Hz when I do a vinyl transfer. I first do the inverse (filter out everything above 30) to check if I'm missing anything, but there is seldom anything musical to be heard in this range.

 

I have done my own tests and found that there is indeed MUSICAL content below 20Hz on many non-classical vinyl recordings! The lowest I can get away filtering out is about 15Hz, although removing any DC offset with my software of choice could have the same effect in some situations.

Graham, I have found that 30Hz is way too high! I can hear the bass, or the fullness being removed bigtime!

 

Also if the arm and cartridge are not well matched (i.e. high mass arm and a high compliance cartridge), any slight warp can cause woofer pumping like you wouldn't believe - particularly at the beginning of an album.

 

Interesting that this can even translate to CD (although there should be nothing below 20 hz). Last night I listened to the Verve Master Edition of "Ella Fitzgerald & Billie Holiday At Newport". As noted in the booklet, Billie Holiday's part is taken from a disc transfer (strangely enough, this is the only information they give on this - they don't say if the tapes are lost or in bad condition or whatever). Now when you play these tracks, the woofers are wobbling in a way I've never before experienced with all but the worst LPs. Anyone else notice?

Arne

PS. Steve, do you know what happened to the original tapes?

 

Steve, thanks, I'll check it out this weekend before I change over to the Grover Interconnects.

 

Actually the CD can, theoretically, store information down to 1 Hz, 0.5 Hz or lower - what's to stop it - it's just a representation of a sound wave that has no real low end limit. It's the digital to analog converters in the player and the amplifier that just might cut off at some point below that 20 Hz line. That self filtering is why most CD player spec sheets state 20 Hz as the low end limit. There are some players that will go lower - I think I've seen some players' specs start at 2 Hz.

Joel