Cd frequency responce ?

[woody]

I know that some clasical music records have a lot of content
below 20hz. When cd's are produced are these subsonics also
included?

 

[Hi_Q]

I would be interested to know what orchestral instrument produces a fundamental tone lower than 20 Hz

 

[kevinkr]

Beyond the obvious large pipe organ (16Hz) here is a list - I will admit I was somewhat surprised. More instruments on this list than I would have ever expected.. (Ignoring the midi stuff.)

http://www.contrabass.com/pages/frequency.html

There is no inherent lower limit on the LF response of a cd, but practically speaking most players don't go too much below 10 - 20Hz, and the rest depends heavily on microphones and studio hardware. Usable 16Hz shouldn't be a problem with most players, but speakers that can reproduce those frequencies cleanly are relatively large and expensive. IMO most LFE HT subwoofers generate multiple harmonics of the fundamental which probably isn't a good thing. In the case of a 16Hz organ note I think you are hearing the 2nd harmonic, but you can feel the fundamental if present.

 

[AndrewT]

I seem to recall that the low frequency limit for CD is an octave or more above the DVD standard.

Can anyone refer us to the Philips' CD standard?

 

[Hi_Q]

http://en.wikipedia.org/wiki/Red_Book_(audio_CD_standard)

Red Book is the official CD specification as listed above.
Les

 

[AndrewT]

http://en.wikipedia.org/wiki/Red_Book_(audio_CD_standard)
says 20Hz lower limit, but can Wikipedia be relied on?

 

[Hi_Q]

In theory I suppose you can take a CD down to 0Hz, the sampling rate limits the top end to around 22kHz. I did find the following whilst surfing on sonicflare.com

"The CDs themselves are normally cut at 10Hz unless you master them not to. Though , I have never seen any mastering software that allows audio below this either, not that I have looked a lot be be honest. However, most pre-amps and other audio gear also cut at approx 10 Hz either due to that they are designed to do this to prevent damage to loudspeakers (DC kill speakers) or that they contain caps in the audio path that makes it impossible for frequencies below 4Hz to pass.
So, in essence, specially mastered CDs,CD players and amps are needed to feed this bass beast."

Other sites visited all give the response 20Hz - 20kHz.
The opening thread referred to classical records, I assume Vinyl medium, these are usually rolled off much sooner due to reproduction constraints, for example turntable rumble.

 

[kevinkr]

I missed the reference to LPs, but due to arm/cartridge resonances and tracking issues with large groove modulations I would doubt any LP is cut with significant signal content below 20Hz.

 

[Hi_Q]

Yep, those were the words I was looking for

 

[Speedskater]

The upper frequency is a limit because the Nyquist police won't let us go any higher. I think that the 20 Hz low frequency is a specification not a limit. We could put a sub 1 Hz signal (maybe an almost DC signal) on a CD or a WAV file. But then, what do we do with it?

 

[jcx]

play it in your 1st gen shuffle as a cheap isolated lab source - I've put 16/48 sq sine and triangle .wav on my shuffle down to 5 Hz

 

[Speedskater]

It's real hard for the average bear to measure low frequency AC (below 20Hz) the DC ranges of an oscilloscope or some PC sound cards maybe the easiest. Or you could build a AC to DC circuit and use the DC ranges on your meter.

 

[martin clark]

IIRC you can indeed code DC onto a CD, but the recommendation was for 5Hz cutoff. This is mostly to avoid problems with DC- offset sensing relays in cd players, amps and so on.

Besides which, I doubt there's a studio mic out there doing anything useful that low.

 

[Ron E]

I have a Denon test CD with a 5Hz-20k sweep.

My player played it fine and at full level - the analog meter I had bounced very quickly at first.

The same CD has a 22.05kHz test tone - I never played it, I think it is made to check out the filters.

 

[Cloth Ears]

The upper frequency is a limit because the Nyquist police won't let us go any higher. I think that the 20 Hz low frequency is a specification not a limit. We could put a sub 1 Hz signal (maybe an almost DC signal) on a CD or a WAV file. But then, what do we do with it?

I used to have an early test CD with a sweep from 1 to 20kHz. The woofers simply moved backwards and forwards (slowly at first) until the sound started coming in at around 20Hz. So there's no limit at the low-end, just what is actually put on the disc.

 

[dangus]

I've heard that a lot of that extreme low frequency stuff is just the rumble of trucks or subways near the studio, or from the air-conditioning system.

Doesn't the RIAA spec roll off below 20 Hz to minimize rumble?

 

[Iain McNeill]

It's very unlikely that any of the post-DAC electronic stages are DC coupled so there's probably several low pass stages between DAC and output. Everyone's experience will differ depending on equipment.

My experience supports the creation of CD-R's with DC but I couldn't say if they were red book compliant.

Trouble with DC is it uses up dynamic range without providing any benefit. Why would you want to?

BTW KevinK - that was a great chart on what instruments played what lowest note. A real education - thank you!