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Announcement: ASR Will Be Measuring Speakers!

minus3dB

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This is pretty awesome news. I've become badly addicted to reading all of your component reviews and measurement data. This will only pour fuel onto the fire. :p

The most unique aspect of your reviews I think is the ranking of how equipment performs in various measurements. Taken with a grain of salt or two as you caution, this is precisely the kind of thing I've always wanted to see in the audio press, or media, if you will. As others have pointed out, the dilemma is how to carry forward that signature "single number" feature in the loudspeaker domain?

Could it be possible to derive a meaningful figure of merit for complex graphical data such as FR plots and spinoramas? Perhaps, but ultimately any single descriptor of an information-rich graph like those things will have an averaging effect. There are probably some mathematicians among us who could give that some thought.
 

Blumlein 88

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Just thought I'd throw this in though many of you know it already.

Probably helps if you have read Floyd Toole's book to have the basic vocabulary and ideas in regards to spin-o-rama testing the Klippel system can do. If you don't have the book here are a few short articles on the web explaining various ideas about spin-o-rama testing and what a desired result is.

I see already people asking, "hey Amir, can you show this or test this". That is good, but some of what the Klippel will show makes sense if you know about the Harman research and how it became a speaker testing standard in the ANSI official audio standards.

One thing to look for is Directivity Index or DI from the spin-o-rama data.

Here is a good slideshow presentation with some explanation. Probably the most thorough without reading Toole's book.
https://www.sausalitoaudio.com/wp-content/uploads/2018/07/Interpreting-Spinorama-Charts.pdf


Here is a 7 page article by Floyd Toole explaining DI and spinorama results.
https://www.edn.com/design/audio-de...ring-the-essential-properties-of-loudspeakers

It is explained here also.
https://www.audioholics.com/loudspeaker-design/understanding-loudspeaker-measurements
This link below is probably the best single page explanation.
https://www.audioholics.com/loudspeaker-design/measure-loudspeaker-performance

Sorry for the scattershot approach some explanations are easier for a given person than others.

Here is another explanation in terms of the ANSI standard.
https://speakerdata2034.blogspot.com/2019/02/spinorama-cea-2034-2015-ansi-data-format.html
 
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MZKM

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Could it be possible to derive a meaningful figure of merit for complex graphical data such as FR plots and spinoramas? Perhaps, but ultimately any single descriptor of an information-rich graph like those things will have an averaging effect. There are probably some mathematicians among us who could give that some thought.
Toole describes Sean Olive‘s predictive preference rating here (~50min mark):

SINAD is just one parameter (THD+N), and it encompasses a lot of the performance but doesn’t tell the whole story (especially for amps), for speakers there is no way to have a single value number without weighting a bunch of parameters like Olive did, similar to how Rtings comes up with their Sound score for headphones.
 
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amirm

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Toole describes Sean Olive‘s predictive preference rating here (~50min mark):
That is the number I hope to compute. I need to setup an analysis script but there is not enough info in Sean's AES paper. I plan to contact him soon once I have some measurements to analyze.
 

napilopez

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Just thought I'd throw this in though many of you know it already.

Probably helps if you have read Floyd Toole's book to have the basic vocabulary and ideas in regards to spin-o-rama testing the Klippel system can do. If you don't have the book here are a few short articles on the web explaining various ideas about spin-o-rama testing and what a desired result is.

I see already people asking, "hey Amir, can you show this or test this". That is good, but some of what the Klippel will show makes sense if you know about the Harman research and how it became a speaker testing standard in the ANSI official audio standards.

One thing to look for is Directivity Index or DI from the spin-o-rama data.

Here is a good slideshow presentation with some explanation.
https://www.sausalitoaudio.com/wp-content/uploads/2018/07/Interpreting-Spinorama-Charts.pdf

Here is a 7 page article by Floyd Toole explaining DI and spinorama results.
https://www.edn.com/design/audio-de...ring-the-essential-properties-of-loudspeakers

It is explained here also.
https://www.audioholics.com/loudspeaker-design/understanding-loudspeaker-measurements

Sorry for the scattershot approach some explanations are easier for a given person than others.

Here is another explanation in terms of the ANSI standard.
https://speakerdata2034.blogspot.com/2019/02/spinorama-cea-2034-2015-ansi-data-format.html
These are all great resources. I would just add two things:

This 1 hour lecture by Dr. Toole, which I think summarizes all the principles very well. He's a good presenter. If you have an hour to kill, I highly recommend it.


And then if you want more specifics about how measurements are typically made and how individual curves are derived, you can read the CTA-2034A document, which standardizes the spinorama.

Edit: I see @MZKM posted the video above too. Well, can't hurt to watch twice :)
 

MZKM

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That is the number I hope to compute. I need to setup an analysis script but there is not enough info in Sean's AES paper. I plan to contact him soon once I have some measurements to analyze.
This patent filing from Sean may have more info.

If it’s the same as for headphones, I don’t think Harman discriminates deviation/peaks/dips in regards to frequency, a 5dB dip at 10kHz has the same effect on the rating as a 5dB dip at 100Hz.

Even though how they rate and how they weight is debatable, I feel an approach of scoring similar to Rtings would be worthwhile in considering.
• FR flatness (+/-3dB; weighting bass more than treble; weighted smoothing likely also needs to be applies, but REW’s psychoacoustic smoothing may be too extreme)
• Bass extension (-3dB or -6dB relative to sensitivity SPL)
• THD, again with weighting.
• Imaging; Keeping with making this possible with a script, some thinking needs to be done. As it’s easy to see via analyzing measurements.
 
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maxxevv

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How much time I have to do this, I don't know. But my goal was to test blind and use my youngest son who has excellent high frequency hearing (and overall sensitivity). I pursued help to get an automated turntable to switch speakers quickly but got too much for me to handle. If someone can help build this, it would be great. It is just a simple table that you put 3 speakers on, and it rotates them into position using external control. My thought is to limit it to smaller speakers right now. Once there, I can put an acoustically transparent curtain in front of it and perform ABC tests while someone else listens. I can use my dedicated theater which is extremely quiet and has the space to hold such contraption. :)

Failing this, I just plan to turn on the speaker and give it a quick listen in my main system area/lab. This would be a casual test but sufficient for people who say, "did you listen?"
Designing one from scratch is not difficult at all. As long as the functional requirements and space envelope is clear.

Would need someone to sort out the electronic controls though.
 
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amirm

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Even though how they rate and how they weight is debatable, I feel an approach of scoring similar to Rtings would be worthwhile in considering.
Problem is that Rting has not correlated their ratings to listening tests as Sean did. So who knows what they show is representative of listener preference.
 
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Thread Starter #231
Designing one from scratch is not difficult at all. As long as the functional requirements and space envelope is clear.

Would need someone to sort out the electronic controls though.
The controls are easy and I can do that. I also wrote up the requirements. It needs to handle 3 speakers, each with say 20 to 30 pounds, and spin them around in 2 to 4 seconds without them being thrown to the walls. :) If someone can build the turntable with servo motor/controller, I can do the rest.
 
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FYI I have had two offers of speakers being sent and I am collecting others. So we are getting a decent start. :)
 

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dukanvadet

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That is the number I hope to compute. I need to setup an analysis script but there is not enough info in Sean's AES paper. I plan to contact him soon once I have some measurements to analyze.
One slight problem is that i think that would give an advantage to speakers that can be used fullrange. A smaller speaker that are meant or likely to be crossed over to subwoofer may get a bad score that would turn out really good once you use it with a sub?
 

Thomas_A

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This is all good, but I have one question. Is there a way to adjust scoring according to the intended placement of the speaker and its use (near-wall, on-wall, "free field", toe-in degree, room size/dimensions)? A speaker can sound quite different depending on placement of speaker, listener position and room dimensions.

Perhaps it is mentioned elsewhere, but there may be a possibility to charge som money for measuring speakers for the DIY community. It could help financing the whole thing as well.
 
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amirm

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Perhaps it is mentioned elsewhere, but there may be a possibility to charge som money for measuring speakers for the DIY community. It could help financing the whole thing as well.
For what they can afford to pay, it won't make sense to use my time for that instead of testing commercial products with broad appeal. Exceptions can be made of course. FYI service using the same instrumentation as this one cost about $1,000 for one set of measurements. You think any DIY would want to pay anything close to that?
 
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Thread Starter #237
This is all good, but I have one question. Is there a way to adjust scoring according to the intended placement of the speaker and its use (near-wall, on-wall, "free field", toe-in degree, room size/dimensions)? A speaker can sound quite different depending on placement of speaker, listener position and room dimensions.
Above a few hundred hertz, a speaker sets the overall tonality of what you hear, not the room. Below that, it is another ball game and requires optimization that is completely room dependent, not speaker.

A speaker that measures well will behave well in a room. Those with odd off-axis response are the ones that requires a lot of messing around to get them to sound good.
 

Thomas_A

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For what they can afford to pay, it won't make sense to use my time for that instead of testing commercial products with broad appeal. Exceptions can be made of course. FYI service using the same instrumentation as this one cost about $1,000 for one set of measurements. You think any DIY would want to pay anything close to that?
I have not read the whole thread, so I don't know how the financial solution looks like except for donations/contributions.
 

Thomas_A

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Above a few hundred hertz, a speaker sets the overall tonality of what you hear, not the room. Below that, it is another ball game and requires optimization that is completely room dependent, not speaker.

A speaker that measures well will behave well in a room. Those with odd off-axis response are the ones that requires a lot of messing around to get them to sound good.
Bass region yes, a speaker can be designed to use wall support for instance. Also I was more thinking of wide vs narrow dispersion even if the dispersion is smooth.
 

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