REW Update

[abbey road d enfer]

Defining it is easy.

I don't think so. Q is a mathematical abstraction, that correlates only distantly with the very object of equalization. I think BW is much more evident. But it can't use the historic definition of BW either.
The audio community has more or less settle on a definition of boost/cut for shelving EQ's; it is based on a number of assumptions, but it works. Why couldn't it settle on a imilar agreement for BW in peak EQ's. The only people I've seen using the academic definition of Q in peaking EQ's are DSP programmers, who generally end up with a total cock-up, that needs to be corrected by people who understand audio.

Justifying the definition is the hard part. Let's say 3dB.

Why choose the value that just doesn't work?

 

[ruffrecords]

I don't think so. Q is a mathematical abstraction, that correlates only distantly with the very object of equalization. I think BW is much more evident. But it can't use the historic definition of BW either.
The audio community has more or less settle on a definition of boost/cut for shelving EQ's; it is based on a number of assumptions, but it works. Why couldn't it settle on a imilar agreement for BW in peak EQ's. The only people I've seen using the academic definition of Q in peaking EQ's are DSP programmers, who generally end up with a total cock-up, that needs to be corrected by people who understand audio.

Why choose the value that just doesn't work?

I think we are talking at cross purposes. You asked me to define significant in the context of how far past the normal -3dB point that is used to define Q does the filter response need to go. I said define significant as 3dB - so the response would have to change by a total of 6dB from the peak. I also said justifying it would be the hard part. I agree it would be nice if there was a generally agreed definition of the parameters of a peaking EQ.

Cheers

Ian

 

[abbey road d enfer]

so the response would have to change by a total of 6dB from the peak.

OK, now I understand. Actually, it's close to the definition I have used for years, that is defining the BW from teh points situated at an arbitrary fraction of the boost or cut. For example, for a 1/3 octave graphic EQ with a boost of 12dB, I used to take the points at +3dB, because it made sense in terms of perception. Using the (inappropriate) academic definition would take the 9dB points resulting in a misleading figure suggesting the filters were much narrower.
This method does not solve all issues since the same EQ set at 6 dB boost would be perceived as narrower because the audibility of the skirts is lesser at 6db than at 12dB.

I also said justifying it would be the hard part.

That's correct. It has to be arbitrary, so it requires a will to reconcile different opinions. I believe that's why the AES tentative committee didn't achieve its task.

 

[trobbins]

Further to my post #200, I have prepared an article detailing the measurement setups and results I made from 3 contemporary Williamson amp output transformers. For those transformers I did have to go beyond the automated REW capabilities, but in general I found it a breeze to use REW to quickly make an impedance plot and a frequency spectrum plot of any output transformer that is on my bench, and then to interrogate those results for particular parameters like primary winding and leakage inductances, shunt capacitance, resonances, nominal bandwidth including gain/phase dips and bumps that would impact feedback stability margins, and core distortion.
https://www.dalmura.com.au/static/Williamson output transformer measurements.pdf

 

[rock soderstrom]

Further to my post #200, I have prepared an article detailing the measurement setups and results I made from 3 contemporary Williamson amp output transformers. For those transformers I did have to go beyond the automated REW capabilities, but in general I found it a breeze to use REW to quickly make an impedance plot and a frequency spectrum plot of any output transformer that is on my bench, and then to interrogate those results for particular parameters like primary winding and leakage inductances, shunt capacitance, resonances, nominal bandwidth including gain/phase dips and bumps that would impact feedback stability margins, and core distortion.
https://www.dalmura.com.au/static/Williamson output transformer measurements.pdf

I have only briefly skimmed your "thesis", but I will study it in more detail later. Many thanks for your detailed work.

 

[Tubetec]

That was an enjoyable read Tim ,thanks .

 

[warpie]

Is it possible to use dual input/output on REW? Can't see such option in the "preference" tab.

 

[trobbins]

What do you want to do? The impedance function uses 2 inputs and 1 output. There is a pro version that allows multiple input channels. The help section and some searches on the REW forum are a good idea.

With respect to equalisers and 'Q', there is a new update that includes that capability.

 

[warpie]

I would like to simultaneously test the frequency response of my stereo/ dual channel gear. Is this only available on the pro version?

 

[trobbins]

I think so, but perhaps search through the REW forum, or post on that forum.
https://www.avnirvana.com/forums/official-rew-room-eq-wizard-support-forum.10/

Is there really a need for simultaneous measurement for a frequency response? I can see that performance measurement of things like cross-talk may be interesting.

 

[warpie]

I think so, but perhaps search through the REW forum, or post on that forum.
https://www.avnirvana.com/forums/official-rew-room-eq-wizard-support-forum.10/

Is there really a need for simultaneous measurement for a frequency response? I can see that performance measurement of things like cross-talk may be interesting.

Well, frequency plots is only an example.

After searching a bit on the avnirvana I think it's not possible. At least on mac and without the pro version.

 

[abbey road d enfer]

I would like to simultaneously test the frequency response of my stereo/ dual channel gear. Is this only available on the pro version?

Is it something you need absolutely?

 

[warpie]

Is it something you need absolutely?

Well, it would be nice.

Not sure I understand the question

 

[trobbins]

It's worth noting that REW can be pretty processor intensive (or perhaps comms intensive if using USB2) even for one channel, especially for RTA with long FFT lengths or for measurements with long sweep times. It would almost be worth using 2 PC's if time or refresh rate was a key issue, and that could also side-step the need for running two channels on the one instance of REW.

 

[abbey road d enfer]

Not sure I understand the question

Streo/2-channel measurements save time, and that's about it. Not so important for DIY.

 

[warpie]

Streo/2-channel measurements save time, and that's about it. Not so important for DIY.

That's true but it's also nice to be able to see/ compare both channels on a single real-time FFT window.

 

[abbey road d enfer]

That's true but it's also nice to be able to see/ compare both channels on a single real-time FFT window.

It's just a minor convenience. Overlay does it, although it takes twice the time.

 

[Tubetec]

I just tried the latest test release of REW ,
Its had a major revamp ,
Theres some very nice new functions and tweaks to the UI ,
You can read up on all the details here ,
https://www.avnirvana.com/threads/v5-20-14-early-access-build.11154/The first post always contains the newest release , and its updated on an almost daily basis by John ,
Visually everything is better , buttons and controls have undergone changes to aid workflow ,
There all kinds of refinements just waiting to be discovered ,
Grab yourself a copy and start contributing ,

Hats off to John , the turn around time on sorting out glitches and errors the users find is astonishing , no one person can test every single function , every new feature , but by throwing the software out there any issues are very quickly addressed ,

I just loaded the Windows version up now , at first glance theres a comprehesive update to the generator section , all kinds of new standardised test tones have been added ,
How the sound cards are handled on start up has changed , but manual selection is always available in preferences . There seems to have been many improvements to the processes in the back round , allowance for multicore processing and better allocation of memory where a very large number of test results need to be compared side by side ,
I'll take an afternoon coffee and core drill into it a bit further ,
I can give the Mac OS version a look later too , maybe theres a few Linux people willing to dive in around here .

 

[Tubetec]

The new version installed seamlessly over the old on my MAC ,
The Apple USB C headset adapter settings were carried over from the previous install so the mic is active on the scope input as soon as you press the red button , the crispness of the visuals and lack of time delay is quite breathtaking , but Ive never had anywhere near this level of graphics card processing power on any computer before , its no sweat off the trashcans block and tackle .

Putting the scope window upto full screen the waveforms remain free of any aliasing or slowdowns , a 28 inch TV set allows me work at greater distance without having to squint at a laptop screen or a 8inch hardware DSO,

Theres refinements to the FFT , with new options for the math and windowing ,
In general the software seems to present a better picture of the particular levels your looking at , ie the auto zoom on the waveform is improved .
The EQ section has a new 3D view with perspective adjustment , it really is very easy on the eye ,
Many of the control buttons now have a pleasing new highlighted border making them easier to grab with the mouse ,
The main level meter window has many improvements , with every possible kind of measurement weighting standard available , voltages , dbv , measurements in known loads , and much more .
Sample rate capabillities of REW have been increased further to keep up with the RME brigade ,

In case anyone was wondering where the dark backround control is its at the very end of the View page under preferences ,

This thread hadnt seen the light of day in quite a while , weve had many new members since ,who may not know about this blinding bit of kit ,
Big cheers to John Mul ,

 

[ruffrecords]

Definitely my go to measurement tool.

Cheers

Ian