EQ properties of tape

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PHILANDDON

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Hey,

I was just curious.........putting aside such things as tape compression/effect/harmonic distortion what are the EQ properties of tape when compared to say 24/44.1 digital. For example, I've heard that the lows roll-off at around 32hz? Is this right? What about the highs? I've heard there's a bump in the low-mids. Is this true? If so, at what frequency is it......approximately. Thanks.
 
PHILANDDON said:
Hey,

I was just curious.........putting aside such things as tape compression/effect/harmonic distortion what are the EQ properties of tape when compared to say 24/44.1 digital. For example, I've heard that the lows roll-off at around 32hz? Is this right? What about the highs? I've heard there's a bump in the low-mids. Is this true? If so, at what frequency is it......approximately. Thanks.
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One aspect that's always interested me is the amount of rolloff. For example, a typical tape deck spec sheet may show a frequency response of 40 Hz to 20 kHz, but that's only a plus or minus 3 dB deviation from 1 kHz.

The true frequency response of tape dips a bit lower and much higher -- often near 30 kHz or better. Depending on the machine the highs may rise or fall somewhat immediately beyond 20 kHz, but they don’t disappear until well beyond the range of human perception.

In contrast, digital systems hit an absolute brick wall at 20 kHz... no rolloff. A high-resolution digital system wouldn't have to be restricted to 20 kHz, but in practice 20 kHz is where it is due to filtering. The low frequency response is much lower, almost to DC, and flatter than tape. My Fostex CR-300 CD recorder goes down to 4 Hz and +/- 0.05 dB across the spectrum.

The frequency response of digital and tape also behave differently under various signal levels. As levels are reduced from 0 VU the high frequency response of tape increases. For digital formats the frequency response stays basically the same except at very low signal levels, where it is even less than 20 kHz.

For example the frequency response of my Akai GX-77 reel-to-reel is 25 Hz to 26 kHz +/- 3dB @ 0 VU (7-1/2 ips). But @ -20 VU it’s 25 Hz to 33 kHz.

I don't know what the ramifications of these differences are, and I don't think it's the only element that affects the sound. But, odds are it’s significant.

Tim
:)
 
The points made about the machine itself being the major factor to how flat or unflat the response of analog tape recording is can't be stressed enough.

Take 10 different machines with the same roll of tape and you'll get 10 different response curves. Why is that? Because unfiltered/eq'ed internal processing and head designs are what vary from model to model of machine and the natural unequalized response of magnetic tape is generally a very curvy response that must be equalized in order to get some semblance of a relatively flat response.

That's really the beauty of analog recording is that it's a similar wealth of variety that we all enjoy in picking different microphones, amps, speakers, musical instruments and processors that all have their own unique character and experimenting with them is what gives us, hopefully, the unique sound that we like to call our own.

Maybe that's why so many people like to incorporate analog devices in the recording chain because the alternative is clone-like behavior and then we all end up sounding like each other and that gets boring real quick.

Cheers! :)
 
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