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Like Gimicks?
#110910 09/16/05 10:38 PM
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BruceH Offline OP
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http://www.av123.com/products_product.php?section=speakers&product=74.1

Why? Is this for people with white van speakers?



Re: Like Gimicks?
#110911 09/17/05 12:05 AM
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In reply to:

Just because you can not hear 45KHz does not mean your brain does not process it.




And the information gets to my brain how, exactly?

Reminds me of the piezo-electric super-tweeters that were all the rage 20 years ago. Whatever floats your boat.


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Re: Like Gimicks?
#110912 09/17/05 01:23 AM
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Ok, so apparently nobody at AV123 is familiar with auditory physiology. It might help them to study up really quick.

The tiny bones in your ear may still vibrate, yes, but there's an organ behind these bones called the cochlea that is responsible for turning that mechanical vibration into signals that the brain understands. The cochlea is filled with fluid and is lined with thousand of tiny hairlike cilia, each of which is attached to a nerve that is connected to the part of the brain responsible for "decoding" sound.

When a sound wave hits the eadrum, it vibrates the three bones of the inner ear, which in turn cause pressure waves that travel down the spirals of the cochlea. The nature of the pressure wave, which is dependent upon the frequency of the initial sound, determines which cilia it excites. And it is an excited cilia that causes us to say "I hear something."

So guess what -- the reason a person with normal hearing cannot hear frequencies above about 20kHz isn't that the brain doesn't care to pass that information along in a recognizable fashion, it's that those frequencies don't excite any cilia and thus don't generate any brain signals whatoever.

Here's a description of the workings of the ear in more detail

So if listening to music that contains information well above the 20kHz threshhold does actually result in an "emotionally connected and involved feeling" -- it's got nothing to do with how the brain processes the sound and more to do with the psychological effect of "well, I know there's more sound playing, so it must sound better."

Now, I'm not saying these ERTs don't do a thing. You'll notice that the two selectable crossover points of 11kHz and 15kHz still fall within the range of ordinary hearing. So any perceived benefit they deliver to your audio experience may still be real. Meaning if you took a before and after frequency response of your speakers+ERT, they'd differ.

Re: Like Gimicks?
#110913 09/17/05 03:11 AM
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Ditto Peter's analysis. Shame on AV123 for trying to peddle what might well be a better tweeter for the regular 10KHZ-20KHZ top octave with pseudo-scientific nonsense about ultrasonics.


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Enjoy the music, not the equipment.


Re: Like Gimicks?
#110914 09/19/05 04:50 PM
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In addition - these speakers, it would seem, woudl really only work with recordings that are not band-width limited to 20Kh to start with. If I'm not mistaken, aren't many cd's given a 20Kh ceiling, where there is no information above that point - and thus, no sound being produced at that point?

I understand that for some analogue recordings (tape/record) this might vary, but who listens to these media anymore with any regularity? I know that there are vinyl enthusiasts out there (and in here) who tout the benefits of the uncompressed vinyl medium (and I'm not here to dispute that - I believe that vinyl probably contains more information than cds), but if you're listening to mostly cd's or other digital media, what benefit will these add, except in the 11 or 15Kh range?

Re: Like Gimicks?
#110915 09/20/05 06:04 AM
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In reply to:

If I'm not mistaken, aren't many cd's given a 20Kh ceiling, where there is no information above that point - and thus, no sound being produced at that point?


I don't think anyone uses a low pass filter to roll off frequencies above 20KHz, you're probably thinking of the Nyquist limit which requires at least two samples per oscillation of a frequency to "describe" it digitally.

ie: the highest sampleable frequency is half the sampling rate. (44,100 for CD / 2 = 22,050Hz)

Bren R.

Re: Like Gimicks?
#110916 09/20/05 10:21 PM
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You know that noise in TV soundtracks when someone grabs a tonearm and drags it across the record, then everything stops...

Hold on. I'm pretty sure that in the early days of CD production they weren't low-pass-filtering the tracks before digitizing, and the HF content above 22.1 KHz aliased back down below 22.1 and sounded awful. After about a year all the new CDs were digitized after LPF-ing around 20 KHz, everyone replaced their old CDs (all 6 of them) and lived happily ever after.

This was a while ago but I do remember this clearly.


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Re: Like Gimicks?
#110917 09/21/05 05:17 AM
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It could well be that producers roll off the ultra-sonic frequencies - anything above the Nyquist limit (and even approaching it to a lesser degree) shows up as distortion on the final master (not necessarily noise as in white noise, but as something incorrectly quantized)... but since we're talking about ultra-highs here, and sound pressure drops 3dB per octave as you go up, those sounds are already at and beyond the limits of human hearing, and are at 16dB or so below a reference level at middle C - so I'd say it's primarily academic.

Bren R.

Re: Like Gimicks?
#110918 09/21/05 07:28 AM
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Agreed... the problem was with the harmonics over 22 KHz which aliased back down, ie 25 KHz was reproduced as 19 KHz, 27 KHz as 17 KHz etc...


M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
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Re: Like Gimicks?
#110919 09/22/05 03:10 AM
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The first circuit in digital recording is the "anti-aliasing" low-pass filter which removes any incoming frequencies above half the sampling rate(22.05 KHz for a 44.1KHz CD sampling rate). The reason is that at least two digital samples of a frequency are necessary in order to reproduce it perfectly; above half the sampling rate only one sample could be taken. This one sample wouldn't define the specific frequency sampled, but would allow several different "alias" frequencies, as John described, to intrude lower down in the audible range.

Then, the last circuit in the process is the "anti-imaging" filter which removes frequencies above the audible range which were created as artifacts during the sampling process and which when removed leave the original perfect analog waveform which entered the system.


-----------------------------------

Enjoy the music, not the equipment.



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