The Black Hole......

31697B

Disabled Account
2012-05-19 12:53 am
I know this is not even close to what’s being discussed, but the lower level of room reflection comment made me think of this exact opposite which seemingly also has a figure 8 polar pattern that can be placed one in front and one behind listener? These were popular in your heyday, any experience with them?

HUMAN Speakers: EPI 1000 information

No, I have no experience with them.


-RNM
 

Hans Polak

Member
Paid Member
2005-03-17 4:25 pm
Blaricum
It's not "seeming", it is frequency shift. Overlay the before and after filter and examine the zero crossings.

As I said, the FFT does not see the resultant frequency of the output. You have demonstrated exactly what I said.

I give up.

The main lobe that you thought to vanish in a continuous signal did not vanish
My question why filtering the cymbal file at 44 was the wrong decision remained unanswered and a Gibbs envelope is still a mystery to me.

I don’t even know if we disagree, we simply use different languages causing that I still haven’t got a clue what exactly you are trying to tell.

Hans
 
The initial discussion was if cd rate was sufficient.

I think part of the discussion is about what we mean with sufficient.

My take would be audible, but I guess JN means measurable?

Unfortunately, an exponential does not have one frequency, nor is it time invariant.

I thought time invariant was a property of a system or an operator? How is it defined for a signal?

/örjan
 

Hans Polak

Member
Paid Member
2005-03-17 4:25 pm
Blaricum
Still further to the "seemingly frequency shift" that I mentioned above: the time domain signal that we see is the sum of all signals, but what we hear are individual frequencies.
So when two or more added frequencies suggest a frequency shift, we still hear the individual frequencies.

That's the case when subtracting Gibbs frequencies and the "above Brick Wall frequencies" from an Audio signal.
Seemingly the remaining signal may be shifted in frequency, but the FFT shows that every frequency is still correctly where it should be, just like what we hear.

Hans
 
I give up.

The mainlobe that you thought to vanish in a continuous signal did not vanish

Where did I say that I thought the main lobe would vanish???


My question why filtering the cymbal file at 44 was the wrong decision remained unanswered and a Gibbs envelope is still a mystery to me.
A cymbal file has far to much complexity to be useful as a diagnostic other than "something is different".

A Gibbs envelope is the shape and form of the difference between input and output, as Scott pointed out it was at Gibbs frequency.

I don’t even know if we disagree, we simply use different languages causing that I still haven’t got a clue what exactly you are trying to tell.
Hans
We certainly agree on that.

It is very very simple. Overlay your input signal on your output single on a single plot. The frequency will be different, the envelope will be different.

Yet you seen to be claiming they are the same.

jn
 
I think part of the discussion is about what we mean with sufficient.

My take would be audible, but I guess JN means measurable?
The initial claim by others was that cymbals at 44 rate are audibly different from that taken at higher rates.

I detail the issue of signals near Fs that are amplitude modulated such that the resultant filtered output excludes one of the sidebands caused by amplitude modulation.

I thought time invariant was a property of a system or an operator? How is it defined for a signal?
/örjan
what I meant was, during the actual exponential, the frequency is changing. That is why an FFT of an exponential waveform has a broad fuzzy spectra on an FFT. Using that signal as a modulator puts that broad fuzzy spectra on the primary signal's fft as well. An FFT cannot easily show that the spectra is changing over time, it just shows total energy over a specfic span.

jn
 
Still further to the "seemingly frequency shift" that I mentioned above: the time domain signal that we see is the sum of all signals, but what we hear are individual frequencies.
So when two or more added frequencies suggest a frequency shift, we still hear the individual frequencies.

That's the case when subtracting Gibbs frequencies and the "above Brick Wall frequencies" from an Audio signal.
Seemingly the remaining signal may be shifted in frequency, but the FFT shows that every frequency is still correctly where it should be, just like what we hear.

Hans
No, it doesn't. Your FFT plots show that very clearly. to wit, the second is missing the upper sideband, the first has it all.

The FFT's are showing very different signals. And your time domain plots before and after VERY clearly show that.

Edit...in fact, you put in a 20K modulated by a 4k, but the filter output is an 18K modulated by 2k.

The next question should be...did I just guess that, or was math involved?;)

jn
 
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These are significant differences, and are caused by having frequency content so close to Fs.

From the days when i took entry level grad school sampling frequency i came up with a more graphic description. It is like a big Monty Python foot coming down out of the sky and squashing the music with stuff splattering everywhere.

dave
 
Basically four 2-ways per speaker (one on each side) so four baffles per speaker. Not sure about different heights and Idk if it was a gimmick or it actually worked.

Four EPI 100s mounted on the 4 sides of a 6 foot tall, slim tower with black full height grills, and solid wood corners with )golden) aluminum accents.

dave