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Time Domain measurements?

haraldo

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I think the Virgo 2 was kind of better. Yes, I was the co designer of the Virgo 3 too but curiouslx it was not as successful in terms of sales.
I was completely shocked and stunned by Virgo III, driven by mono-coupled Burmester 956 and 4 Audio Physic Minos subs ..... I never got to listen to Virgo II
Maybe I found the Avanti III with 4 minos subs better, probably the best bass I ever heard ..... but things have changed since then

Guess what we have now is even way better :)
 

Joachim Gerhard

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I was completely shocked and stunned by Virgo III, driven by mono-coupled Burmester 956 and 4 Minos subs ..... I never got to listen to Virgo II
Maybe I found the Avanti III with 4 minos subs better, probably the best bass I ever heard ..... but things have changed since then
Sure, 4 subs of that caliber can change the world for you.
 

haraldo

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.....Another option is a full 3 way active, digital DSP version where we do the crossover, room and time EQ in the digital domain.....
Obviously with Dr. Brüggemanns UB Filters ... are you also employing Dr. Brüggemanns digital preamp with built-in crossovers?

I think late John Dunlavy once wrote that the ultimate single final test for a speaker is a square wave, in order for this to look really good, all aspects must be there, perfect frequency response and perfect behaviour of all aspects within the time domain. If any of these things are not there, Dunlavy wote that you will see a skewed square wave... much has happened since Dunlavy was active but isn't this a valid point?

So if you put any speaker with extremely well behaved behaviour in the time domain, the square wave must look close to perfect
Is it correct then, a quare wave sent through the active ARA should possibly look better than these ones? :)

The Dunlavy here looks worse than I expected, but maybe it's due to inadequate measuring facilities (no anechoic chamber)


Dunlavy sc-iv a, measured by Stereophile
Dunlavy SC-iva.jpg


Martin Logan Sequel II, measured by Stereophile
Martin Logan Sequel II.jpg


Quad ESL-2805, measured by Stereophile
Quad Reference ESL-2805.jpg
 
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Joachim Gerhard

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No, I use only Uli‘s Software. In my workshop I use Audirvana + on a Windows 10 workstation. We have one fully digital setup with Okto DAC and ROON on a barebone. Our programmer uses ROON too and his DAC is a Merging Technology.
 

RayDunzl

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isn’t there quite many things you can’t measure?

how do you measure the magic of a speaker?

how do you measure a speaker’s capability to bring tears in the eyes while listening to music?

Those would be measures of your response to the stimuli, not of the speaker itself.
 

RayDunzl

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I think late John Dunlavy once wrote that the ultimate single final test for a speaker is a square wave,
My experience observing square waves produced by a speaker (in room, which is where I listen) is that the squareness is very dependent on the frequency being reproduced.

Here, a rising frequency square wave is recorded in-room, and the recorded waveform cherry-picked for one of many frequencies where the speaker manages to present a passable square to the listener:

Lower frequency at left, higher at right:

1594562634259.png
 
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haraldo

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My experience observing square waves produced by a speaker (in room, which is where I listen) is that the squareness is very dependent on the frequency being reproduced.

Here, a rising frequency square wave is recorded in-room, and the recorded waveform cherry-picked for one of many frequencies where the speaker manages to present a passable square to the listener:

Lower frequency at left, higher at right:

View attachment 72961
is that with MiniDSP?
Can that be a reflection that MiniDSP does not do phase correction? (as far as I know)
 

RayDunzl

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Can that be a reflection that MiniDSP does not do phase correction? (as far as I know)
The FIR filter, generated by AcourateDRC in my case, in the miniDSP OpenDRC-DI can performsome phase correction.

It is more a broad than narrowly focused difference.

Black = "corrected", no windowing

1594567153428.png


This is at the listening position, using MartinLogan reQuest speakers.
 
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haraldo

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The FIR filter, generated by AcourateDRC in my case, in the miniDSP OpenDRC-DI can performsome phase correction.

It is more a broad than narrowly focused difference.

Black = "corrected", no windowing

View attachment 72969

This is at the listening position, using MartinLogan reQuest speakers.
I see, what's happening there at 450 Hz? Phase is way better but seems like still some challenges there...
According to spec's on reQuest, that I can see, x-over is at 180 Hz and it looks good there
 
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RayDunzl

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Measuring phase in-room is a slippery subject.

Left, Right and both speakers, with and without correction.

Nothing else changed:

1594573057752.png


The electrostatic dipoles (above) measure much differently than the little JBL LSR 308 - again, no windowing

1594573284477.png
 

haraldo

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Ahhhh yes... I reckon dipoles in-room is bears to measure .... do you not have a chance to do measurements with gating? or is that still a no-go?
yeah 4000 degrees phaseshift ... did you try to do the phase correction on the JBL’s ?
I can’t seem to see any phase corrected curves....
 

UliBru

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My experience observing square waves produced by a speaker (in room, which is where I listen) is that the squareness is very dependent on the frequency being reproduced.

Here, a rising frequency square wave is recorded in-room, and the recorded waveform cherry-picked for one of many frequencies where the speaker manages to present a passable square to the listener:

Lower frequency at left, higher at right:

View attachment 72961
1.
IMO it is misleading to create such squarewaves as they clearly hurt the Nyquist-Shannon sampling theorem.
A squarewave consists of its base sinewave plus odd sinewaves 3rd, 5th, 7th, 11th ... order, see also https://en.wikipedia.org/wiki/Square_wave
Now at e.g. 48 kHz samplewrate the top frequency is 24 kHz. So there is no squarewave above 8 kHz, only sinewaves, because the max. frequency is limiting the harmonics.
So the Audacity squarewave is not a true bandlimited squarewave, indeed it creates many aliasing frequencies.

2.
A squarewave can be considered as a step into positive direction followed by a step into negative direction. The steps are repeating and the step times define the frequency of the squarewave.
Now if the step response of a speaker is known the response on a squarewave excitation can already be estimated quite well.
Indeed you can also convolve the pulse measurement of the speaker with the squarewave.
With a typical passive speaker with step response tweeter first, then midrange driver and finally bass driver you will get a squarewave response as expected.

3.
Usually a speaker does not transfer very low frequencies, it has a high-pass behaviour. By this reason the resulting "squarewaves" show a falling top and a rising bottom.

Summary: it is quite 'dangerous' to stick with the ideal picture of a squarewave, taken from the analog world. The result in the "sampling" domain is heavily influenced by the Nyquist criteria. Furthermore the highpass behaviour of the speaker changes the shape of the squarewave. So with low frequency squarewaves the top/bottom show up tilted. At higher frequencies this gets hidden by zooming into picture. Here the limitation of the bandwidth creates the typical oscillations on top/bottom. Finally the resulting squarewave is deformed by the characteristics of the speaker pulse response which can already be seen by the step response display calculated from the pulse response.
 
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