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Time Domain measurements?

KeithPhantom

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Granted, the phrase is often in the context of lowpass filters...
Well, true, just forgot to add that it was in terms of low-pass filters.
 

haraldo

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I always had the idea that
- a poor measuring speaker is guaranteed to sound like crap
- a perfectly well measuring speaker can sound like crap, but good measurements are requirements for that magic

Obviously the Audiovero and Trinnov guys bring so much to the table that the old toolsets are way obsolete...
(read: I'm saving for that 8 channel Trinnov Altitude-32)
 
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KaiserSoze

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What "might" happen when you send a 200Hz square to the speakers, if you have a sub and a two-way:

(repaired image)

View attachment 73150

Better. The overall periodicity in the midrange output is that of the fundamental 200 Hz, modulated by the 600 Hz 3rd and the 1 kHz 5th, both of which are shifted in phase relative to the fundamental and to each other, owing to the phase rotation that occurs within the midrange's pass band. Were it not for the phase rotation the midrange output would be symmetrical (ditto for the tweeter output). This asymmetry might be physically correct but it certainly does make it more difficult to have any sense of the correctness of the three individual outputs. I'm a bit bothered by the fact that the overall periodicity of the tweeter output is the same as it is with the other two, i.e., it is the 200 Hz fundamental. The fundamental should be fairly well attenuated in the tweeter output, and perhaps it is but just doesn't appear so to me, but those long gaps in the output of the tweeter are puzzling me. The tweeter's output should be the aggregate of all off harmonics of 200 Hz above 1 kHz, i.e., 1.4 kHz, 1.8 kHz, 2.2 kHz, 2.6 kHz .... Has this all been suppressed by the amount of 200 Hz and 600 Hz energy admitted by the tweeter's high-pass filter? Such that you end up with 0 for most of the tweeter's duty cycle? I haven't reached any conviction, but I'm leaning in the direction that this still might not be altogether kosher.
 

KaiserSoze

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Not quite, brickwall filters are known as linear-phase filters. They actually preserve the phase of the original signal or try to preserve the signal as much as possible.

After pondering this for about 5 seconds ... I expect this is because there is no attenuation until right up on the crossover point, and where there is no attenuation, there is no phase gradient. Correct?
 

KeithPhantom

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After pondering this for about 5 seconds ... I expect this is because there is no attenuation until right up on the crossover point, and where there is no attenuation, there is no phase gradient. Correct?
The perfect brickwall would be perfectly linear-phase, but we cannot implement this due to constraints in physics. The phase is kept because the relationship between the frequencies and their respective phases is linear and it is multiplied by a single slope number which represents the phase shift gradient. All-pass filters are filters that even though do not filter anything, change the phase of the frequencies where it is placed. A filter only changes the phase in its point of action, so what you said is correct.
 

KaiserSoze

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No, that filter you are describing is a notch filter or a high-pass filter. Brickwalls are low-pass filters, which if you place it around 20 Hz, anything above that frequency will be filtered. High-pass filters are the ones that filter frequencies below a cutoff.

I will ask you the same thing I ask anyone who begins a reply to another person's post with the word "No." I implore you to please make a reasonable effort to refrain from doing this.

What dc655321 wrote is correct and on target. The term "brick wall" alludes only to steepness of attenuation slope. What I was trying to say (and believe that I did say in an adequately clear manner) is that if the low-pass filter that is applied is sufficiently steep, that there will be no remnant of the original 15 Hz fundamental in the output waveform, and that the overall periodicity evident in the output waveform will be that of the 3rd harmonic (45 Hz). In retrospect this was probably too obvious, however in my prior post I had written something that was not entirely correct and I wanted to correct it. And if it was too obvious, it was not more so than your having written: "High-pass filters are the ones that filter frequencies below a cutoff."
 

RayDunzl

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The tweeter's output should be the aggregate of all off harmonics of 200 Hz above 1 kHz, i.e., 1.4 kHz, 1.8 kHz, 2.2 kHz, 2.6 kHz

Yes.

Analysis:

The odd harmonics combine to create the "flat" high/low of the square.

Removing the low frequency removes the offset from 0, leaving the flat part, approaching 0.

Here's the tweeter with dB - looks like, since it is bandwidth limited, it only gets down to about -80dB here...

1594672840884.png
 

KeithPhantom

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What dc655321 wrote is correct and on target. The term "brick wall" alludes only to steepness of attenuation slope. What I was trying to say (and believe that I did say in an adequately clear manner) is that if the low-pass filter that is applied is sufficiently steep, that there will be no remnant of the original 15 Hz fundamental in the output waveform, and that the overall periodicity evident in the output waveform will be that of the 3rd harmonic (45 Hz). In retrospect this was probably too obvious, however in my prior post I had written something that was not entirely correct and I wanted to correct it. And if it was too obvious, it was not more so than your having written: "High-pass filters are the ones that filter frequencies below a cutoff."
I understand that I made the mistake to forget that you can model a brickwall transition to work with high-pass filter (it is just a way to handle the transition band regardless of the type of filter used).
 

haraldo

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@Joachim Gerhard I can see that in ARA you use Beryllium tweeter while in the Portrait you employ ribbon with a waveguide, while the Beo EX has a ribbon without a waveguide. so there's quite different topologies and technologies....

Could you explain the reasoning behind using so different setups?

With the ribbon and waveguide, is that to enable even lover x-over points to tweeter?
when I discovered that Portrait Extended Edition, I got excited again, I always had this thing with these extremely narrow baffles speakers, like the Virgo III :) (but I am afraid it does not have enough grunt to play Gary Numan or Röyksopp at volume levels that makes neighbors call for police)

Is there an ultimate preference you have with tweeters, you are using Beryllium in your absolute top of the line product, so is that Beryllium tweeter the best you have found?
 
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Joachim Gerhard

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There is nothing best, sorry. Everybody searches for the holy grail but the problem is that there is no holy grail. And HEY, in my age I can do what I want and I am no rap. Other people do that for me in my company. Actually I can give you only one hint : If it sounds bad it is bad, if it sounds excellent it is excellent. Too many parameters involved to get a grasp on it. Mostly it is a poor setup that makes the poor sound. Especially speaker placement is little understood and mostly is limited by pseudo aesthetics.
 

Joachim Gerhard

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I do not want to bash my competition but the tweeter in the Graham LS5/5 costs me 15€. That is the bitter reality. The merchants win, big time, trust me. It is very easy to manipulate opinions. Trust your own senses, it is as easy as that.
 

Joachim Gerhard

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Golden cut, zones of neutrality, you name it. Pseudo Science is a too good name for it. It is just a way to shove big components into hostile environments.
 

KaiserSoze

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A 15 Hz square wave consists of sine waves 15 Hz, 45 Hz (3*15), 75 Hz (5*15), 105 Hz (7*15) ...
Now you take away 15 Hz and get a lowest frequency 45 Hz. So far ok.
But 75 Hz is not 3*45, 105 Hz is not 5*45 ... Thus the filtered result is no longer a square wave.

Okay, but how is it not obvious that if you remove any major harmonic component from a square wave that what you're left with isn't a square wave?

In retrospect the point I was making was probably too obvious. The point was that in order for there to be any realistic expectation for a piece of audio equipment to preserve a square wave, the fundamental frequency of the square wave must be within the normal passband for audio equipment. This is a very basic observation, but the question of square waves and audio came up as it often does, and since this implicit requirement with respect to the fundamental frequency of the square wave is rarely mentioned, I thought it appropriate on this occasion to include it among the reasons why it is not generally realistic to expect audio equipment to preserve square waves.

I had thought that the fundamental frequency of periodicity of the modified waveform should be 45 Hz, the lowest odd-numbered harmonic of the suppressed 15 Hz. But now you've got me wondering whether this is correct. Is this what you are implying? If it isn't 45 Hz, what will it be?

(I'm hoping that you won't reply by saying that since it isn't a square wave or a sine wave that periodicity isn't meaningful, or something along these lines. On a typical day and on a typical web forum, a reply of this sort is what I would most likely get.)
 

haraldo

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There is nothing best, sorry. Everybody searches for the holy grail but the problem is that there is no holy grail. And HEY, in my age I can do what I want and I am no rap. Other people do that for me in my company. Actually I can give you only one hint : If it sounds bad it is bad, if it sounds excellent it is excellent. Too many parameters involved to get a grasp on it. Mostly it is a poor setup that makes the poor sound. Especially speaker placement is little understood and mostly is limited by pseudo aesthetics.

Thx a lot, I really follow you on that one .... I never seen the holy grail ....
haha, yes ..... it's simple
- if I like the music and get tears in my eyes it's good
- If I can´t listen to a song until the end it's bad

Long time ago I realised there is no one speaker that can do everything, which is why I do have several different ones that I can use depending on mood, I think that setup calls for a lot of great fun :)
 

KaiserSoze

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Yes.

Analysis:

The odd harmonics combine to create the "flat" high/low of the square.

Removing the low frequency removes the offset from 0, leaving the flat part, approaching 0.

Here's the tweeter with dB - looks like, since it is bandwidth limited, it only gets down to about -80dB here...

View attachment 73178

Interesting. I don't have access to this kind of tool and my math skills are much too rusty. But, the mere fact that the overall periodicity of the tweeter output that you show is 200 Hz, it seems like the tweeter must be carrying a lot of energy at that low frequency. But I'm probably not thinking about this correctly. And I haven't figured out how to interpret the second graph.
 

KaiserSoze

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I understand that I made the mistake to forget that you can model a brickwall transition to work with high-pass filter (it is just a way to handle the transition band regardless of the type of filter used).

No problemo. I wanted to ask you another question or two about the phase preservation in a brick wall crossover. But I couldn't figure out the right way to ask it. But let me ask this: If phase change is a function of attenuation (and of frequency when attenuation is directly related to frequency), how is it possible that an all-pass filter of the type used in some crossovers are able to introduce phase shift without attenuation?

What is the simplest yet still meaningful way you can think of to explain how this is possible?
 

haraldo

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The perfect speaker will go unnoticed, Peter Walker.

It happened to me first time when I got the small Duntech PCL-15 minimonitors long long time ago, they don´t have any signature, and they dont´t sound like anything ... because they are extremely neutral and just transport you into the musical event... They are bears to drive and can drive my Krell into severe breathing problems but they can give you that magic that makes grown up people cry .....

You never see these on the second hand market :)
(my ex-wife damaged the drivers on purpose, so there is some fixing to do :()
 

Joachim Gerhard

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Then you are more sensitive to timing then other parameters. Yes, a 3 dimensional image matters a lot to me too. I am not a flal earther at all.
 

haraldo

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Then you are more sensitive to timing then other parameters. Yes, a 3 dimensional image matters a lot to me too. I am not a flal earther at all.

Somehow I only seem to really love speakers that are getting the timing things right :)
 
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