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Topic: Frequency response of cassette (Read 9965 times) previous topic - next topic
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Frequency response of cassette

I've been searching around on google and hydrogen audio but struggle to find a definate answer.

Basically what is the average frequency response of an original (not home recorded) cassette tape? I'm guessing its pretty good upto 15khz and then drops off very fast from that. But I'm not sure. Quoted frequency responses of good cassette decks go as high as 22khz and beyond. Surely thats overkill?

If it is as low as 15khz then would it be beneficial to record from cassette at 32khz sample rate? This would save a lot of HD disk space.

Thanks
John

Frequency response of cassette

Reply #1 –
This is what I know (correct me if I am wrong):

Normal: 14 KHz
Chrome Dioxide: 16.5 KHz
Metal: 19 KHz

CD: 22.05 KHz

Edit: There are some types between Normal and Chrome Dioxide as well, as far as I know.

Frequency response of cassette

Reply #2 –
If you plan to encode to a lossy format later on then you should consider recording at 44.1kHz since most encoders are most tuned at that sampling frequency. If ever you want to burn the stuff to CD, you'd have to upsample from 32kHz. Most restoration software also works best at 44.1kHz.

Frequency response of cassette

Reply #3 –
It wery much depends what deck you are using. Some go as high as 23khz(-3db) with metal and 20khz with chrome and about 17-18khz(-3db) with normal tapes. Using dolby nr reduces this somewhat.

Frequency response of cassette

Reply #4 –
Also, unless your deck heads are perfectly aligned to the ones used to record the tape (not very usual in case of pre-recorded tapes), you will lose a lot of HF.

Frequency response of cassette

Reply #5 –
Yes, record at 44.1 or even 96kHz/24bit - waste but what the heck (48/16 if your soundcard resamples and doesn't support 24bit). You can apply a lowpass later after you do noise reduction (& split the big file into pieces) into an audio editor. Do not forget to apply dithering to 16bit.

Specs for my ReVox B215 deck:
Type I : 30 Hz 18 kHz +2/-3 dB (Normal)
Type II : 30 Hz 20kHz +2/-3dB (Chrome)
Type IV : 30 Hz 20kHz +2/-3dB (Metal)

Frequency response of cassette

Reply #6 –
Quote
Basically what is the average frequency response of an original (not home recorded) cassette tape?

Not as good as something you could record at home on a good deck.

Why don't you record it and analyse it?


You said you would save HD space at 32kHz instead of 44.1kHz - but that's only true if you're storing .wavs. If you're using lossy (or lossless! e.g. FLAC) it won't make much difference.

What sound card do you have? How will you store the result? Will you do any audio restortion?

If you answer these questions, you'll probably get a definitive answer from someone here. I doubt it will be "use 32kHz", but you never know!


Cheers,
David.

Frequency response of cassette

Reply #7 –
If you are planning to do any post-processing, hiss removal etc, the syntrillium forums suggest an increase in sampling freq and bit depth ie 24/96 or whatever you can manage.

Last step is to dither it back to 16/44.

As far as frequency response,you get what you get from the deck that you have.If the azimuth of the heads on your playback machine are different from the recorder,your response will be stepped on accordingly. The quality of the original tapes I have played with so far also vary alot,and are in general inferior to vinyl.

Personally, when I do this I record to my box with the dolby nr off and re-adjust the tonal balance after sweeping out the noise(hiss and 60hz hum). It seems to retain more "air" and image depth that way.

There are many excellent discussions at the syntrillium cool edit forums on this topic.

Frequency response of cassette

Reply #8 –
Quote
There are many excellent discussions at the syntrillium cool edit forums on this topic.

There were.

Try visiting them.




Cheers,
David.

Frequency response of cassette

Reply #9 –
Thanks for your replys  B)

Ok to clarify a little, since I was a bit vague I think. I have basically loads of original cassette tapes which I would now like to encode losslessly (monkey's audio) on my PC.

I'm using a Yamaha K-300 (it was good for it's time!) cassette deck, with the output running into the line-in of a Soundblaster Audigy 2. To record the input to wav I'm using Polderbits 2 software. And cool edit for any editing of the resulting wav.

I feel the reply's have made me believe that 32khz probably isn't the way to go as tapes and good playback equipment can go over 16khz much easier than I originally thought. And I have confirmed this using a frequency analysis in cool edit.

The soundblaster audigy 2 confuses me a little. In the specs it quotes:

"
24-bit Analog-to-Digital conversion of analog inputs at 96khz sample rate
"

I assume this means that whatever comes into the line-in gets sampled at 96khz/24bit. Which makes me wonder whether I should be recording through polderbits at 44.1/16. What is doing the downsampling? Polderbits or the Audigy drivers.

In short given this setup, what sample rate/bits should I record the audio in. And what sample rate/bits should I convert to before compression in Monkeys.

Thanks for all the help
John

Frequency response of cassette

Reply #10 –
Quote
Quote
There are many excellent discussions at the syntrillium cool edit forums on this topic.

There were.

Try visiting them.

 


Heh-heh, there still there, you just gotta know where they're hiding!   

AudioMasters

Dex

Frequency response of cassette

Reply #11 –
Quote
Quote
Quote
There are many excellent discussions at the syntrillium cool edit forums on this topic.

There were.

Try visiting them.

 


Heh-heh, there still there, you just gotta know where they're hiding!   

AudioMasters

I know about Audio Masters. It doesn't contain the previous 5(?) years of useful posts from the old synt community. Apparently the Adobe board does, but it's a bit mangled. Supposedly I'm registered, but I can't make it work.

(Yes, I am grumpy that it's gone - that was a good board!)


Yaztromo,

You have a lot of options, and most of them will sound just fine, whichever you choose!


Sample Rate:

You could sample at 96kHz, but the benefit would be almost nothing. The cost in processing time and disc space (if you keep it at 96kHz) shouldn't be under estimated. If you are sure you will never want to burn this stuff to audio CD, then use 48kHz. If some of it might find its way onto audio CD, use 44.1kHz.

You might be able to get a "better" 44.1kHz version by recording at 96kHz or 48kHz, and then downsampling to 44.1kHz - because a good resampling algorithm (e.g. Cool Edit, SSRC, foobar2k) will do a better job than the actual sampling in your sound card. Whether you (or I, or anyone else!) can hear a difference, I don't know. It can't hurt.

There is no benefit to processing at a higher sample rate than the destination. So, if you do record at a higher sample rate, the first thing you should do is resample to 44.1kHz.


Bit Depth:

You can use 24-bits for recording and processing if you want. Though be aware that, with a cassette source, it's probably overkill. 16-bits give you 96dB dynamic range. 24-bits give you 144dB dynamic range. A Dolby B cassette gives you less than 60dB. So, unless you're going to do serious, drastic nosie reduction, EQ, processing etc (which I suggest you don't!), you might as well stick with 16-bits.


Software:

Polderbits?! I admit that I've never heard of it, but if it works, that's great. There are 100 different programs for recording, editing, and audio restortion out there. Some are free (like Polderbits), some are expensive. Some are simple, some are complex. The reason I'm not giving a suggestion is because my favourite (Cool Edit) isn't sold anymore, and Cool Edit Pro / Audacity is rather expensive.


Finally, have you seen this thread, from the FAQ:

http://www.hydrogenaudio.org/forums/index....t=ST&f=1&t=8990

The most important things are a clean cassette deck, with the head azimuth adjusted to match the tape (record a reference cassette of white noise first), setting the recording level correctly, and not trying to do too much to the recording afterwards.

Hope this helps.

Cheers,
David.

Frequency response of cassette

Reply #12 –
Quote
The reason I'm not giving a suggestion is because my favourite (Cool Edit) isn't sold anymore, and Cool Edit Pro / Audacity is rather expensive.

Huh? Audacity is free.   
http://audacity.sourceforge.net/

Frequency response of cassette

Reply #13 –
He probably meant Adobe Audition.

Frequency response of cassette

Reply #14 –
I did - thanks sld. As you can see, I'm obviously subconsciously trying to block the Ad*be thing from my mind! 

Though I'm sure it'll all work out OK in the end. I'll be happy with Audition when I upgrade to it, but it's a shame there's no replacement for CE2k.

Maybe it's up and coming free software like Audacity (and even Goldwave) that made Adobe decide to dump CE2k. Which may be a mistake - once you've tried CE2k, it's easy to migrate to CEP/Audition. But if you find something nearly as good (or better?) for free elsewhere, you might just stick with it.

Cheers,
David.