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Research Project: Infinity IL10 Speaker Review & Measurements

amirm

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#1
If you have been reading our speaker reviews, you have no doubt seen the "Preference Scores" for speakers. This was ground breaking research by Sean Olive published back in 2004 with the goal of predicting listener preference using anechoic chamber speaker measurements. Seemed like an impossible task but Sean pulled it off going beyond people's intuition that "everyone prefers a different sound." Clearly if we can predict preference based on measurements, then it is listener independent.

As we dug into the research, we quick ran into niggling problems with specificity of the standard/measurement computations, lack of clarity in some areas, etc. I don't think anyone had zoomed in and analyzed the research remotely as much as we have done across so many reviews. Still, replicating the research impossible due to the need for controlled double blind testing. One thing we can do however, is see if we can at least replicate the anechoic chamber results.

To be "polite" the research did not list actual speaker names/models. Fortunately they reference the Consumer Reports magazine test that triggered this research (Harman speakers did not do well in that despite winning listening tests). Member @napilopez beat me to the punch and got a copy of the old Consumer Reports magazine that had the list of speakers. See: https://www.audiosciencereview.com/...ce-ratings-for-loudspeakers.11091/post-412375

On top of that list as far as the bookshelf speaker that produced the highest preference score was a long discontinued Infinity Interlude IL10. There was a pair on ebay and I snatched that immediate. It arrived a couple of days ago and I thought I measure it quickly and have a discussion around it.

This is a rather stout speaker compared the lightweight bookshelves we see today:

Inifnity Interlude IL10 bookshelf speaker harman review.jpg


Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I used over 800 measurement point which was sufficient to compute the sound field of the speaker.

Spinorama Audio Measurements
Let's start with our measurements first:

Inifnity Interlude IL10 Spinorama CEA2034.png


This is nice! Response is more or less flat until about 10 kHz with a couple of resonances (peaks) here and there. This is what was reported in Sean Olive's paper: A Multiple Regression Model For Predicting Loudspeaker Preference Using Objective Measurements: Part I-Listening Test Results
Sean E. Olive, AES Fellow

Olive Infinity IL10 Excerpt.png


Note that they used a 70 dB scale for the vertical axis of the spinorama measurements which compresses things relative to 50 dB which we use (and complies with the standard). There is no question that our measurements match theirs proving that we are dealing with the same speaker as "L1."

Note the jagginess in the low frequency response from Harman. That indicates room modes interfering with the measurement in low frequencies. In contrast, my measurements are smooth as silk, not suffering from any reflections.

On the other hand, there is a bit of jagginess in the midfrequencies that is caused by the microphone "cage" that I am using which doesn't show up as much in Harman's measurements. So I think we can expect some numerical differences between their data and ours.

The mean for the listening score of the Harman panel was 6.16 (highest of any speaker). Other than lack of bass, it achieved almost perfect neutrality scores as shown in the bottom graphs for different frequency ranges.

Here is our early window measurements:

Inifnity Interlude IL10 speaker Spinorama CEA2034 early reflections frequency response.png


Quit close to direct axis resulting in a predicted response that is well, very predictable in a good way!

Inifnity Interlude IL10 speaker Spinorama CEA2034 Predicted In-room frequency response.png


Depending on where I draw the line, there is some excess energy but overall, very good showing and a sign of a speaker that is neutral.

The horizontal "beam width" shows the speaker to be on the narrow side than wide:

Inifnity Interlude IL10 speaker horizontal beamwidth measurements.png


But it is smooth otherwise as it falls off:

Inifnity Interlude IL10 speaker horizontal directivity measurements.png


Here is vertical:

Inifnity Interlude IL10 speaker Vertical directivity measurements.png


Not the focus of our study here but for completeness here is the impedance and phase:
Inifnity Interlude IL10 speaker impedance and phase measurements.png


And waterfall:

Inifnity Interlude IL10 speaker CSD waterfall measurements.png


The research found that level of distortion did not correlate with preference in the face of frequency response variations. But let's examine them anyway:

Inifnity Interlude IL10 speaker Relative Distortion vs frequency measurements.png


There is definitely an issue between 1 and 2 kHz even at lower volume of 86 dB.

Here is the absolute level at 96 dB:

Inifnity Interlude IL10 speaker Distortion vs frequency measurements.png


Closely measuring each individual component we get:

Inifnity Interlude IL10 speaker Woofer Port Tweeter Frequency Response.png


Seems like our peak around 600 Hz is a resonance inside the box escaping through the port as circled (someone should do the math).

Speaker Listening Tests
For me this was the heart of the project: how would I like the best preferred speaker in this test? I fired up the speaker and my "5 second impression" was good. This speaker sounded neutral. Female vocals were especially nice.

Try as I might though, i could not like this speaker. Again, tonality was right but there is this grunginess and lack of clarity to everything it played. I tried to take the resonances out to fix it but at the end, it was not conclusive, nor did it make much of a difference. I even pulled my wife over to listen and she said there was some small difference with EQ but not enough for her to care.

Frustrated, I pulled up the Revel M16 which I reviewed a while back. Wow, what a difference. Smooth ask silk. Clean as clean can be. Tonality was similar mind you but boy did it sound nice compared to IL10.

Now, there are two possibilities here:

1. Placebo effect and the M16 being similar to IL10.

2. My brain is forever transformed to listen to distortions in small notes. Right after tonality, this is what I listen for in speakers.

The research used such different speakers with some so broken that clearly the mid goes for tonality difference. Combine that with the fact that unless one is trained, hearing distortion is difficult and you or at least I arrive at the fact that distortion matters once you take care of tonality.

Conclusions
There are none as yet. I expect this to be a living research thread where we discuss what we have found here, and whether we can better rationalize speaker preference from measurements. The preference score for this speaker will be high (@MZKM will post shortly) putting me once again at odds with it. We have to figure out why before I lose all face. :)

For now, I don't recommend that you go and chase this speaker unless you are interested to research it as I did. Note that the speaker was cheap but shipping was a killer.

And oh, I also ordered a Bose 141 which got one of the worst ratings. It too was cheap with high shipping costs. Will be here next week.

------------
As always, questions, comments, recommendations, etc. are welcome.

Now here I go from just testing gear to conducting "research." Surely I deserve a raise for that. Please get out your paypal account infor and donate generously using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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amirm

amirm

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Thread Starter #4
Preference Rating
SCORE: 5.3
SCORE w/ sub: 7.4
Thanks. Do you want to also post the scores using digitized version of Harman's graph?
 

tuga

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#5
So we have a box that has excellent dispersion characteristics and a nearly flat on-axis response (albeit marred by port and mid-woofer resonances) which sounds bad.
What better way to illustrate how frequency response and directivity are manifestly insuficient to characterise the performance of a loudspeaker.
 

MZKM

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#7
We have no exact answer on what Sean Olive's formula rated this, which is unfortunate.

From his non-finalized formula, it looks like a ~5.9:
New Project.png


For his finalized formula, I could not 100% be certain if he even included this speaker, as none of the data point matches up perfectly (I reshaped them and overlaid the same horizontal line, but it didn't bisect any data point exactly in its center), there is one that s close and it looks like a ~6.25.
New Project (1).png
 
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edechamps

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#8
So we have a box that has excellent dispersion characteristics and a nearly flat on-axis response (albeit marred by port and mid-woofer resonances) which sounds bad. What better way to illustrate how frequency response and directivity are manifestly insuficient to characterise the performance of a loudspeaker.
This is a joke, right? Do you realize that you're commenting on the exact speaker model that was deemed to be superior to 12 others in a rigorous controlled double blind test, and is part of the initial set of speakers that was used as a starting point for the Olive preference model? This is actually one of the worst possible examples you could base this argument on!
 

tuga

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#9
This is a joke, right? Do you realize that you're commenting on the exact speaker model that was deemed to be superior to 12 others in a rigorous controlled double blind test, and is part of the initial set of speakers that was used as a starting point for the Olive preference model? This is actually one of the worst possible examples you could make this argument on!
What is a joke, the fact that the IL10 disapointed when compared with the M16 in spite of all the hype surrounding its extraordinary spinning abilities?
 

edechamps

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#10
What is a joke, the fact that the IL10 disapointed when compared with the M16 in spite of all the hype surrounding extraordinary spinning abilities?
It disappointed one listener (i.e. @amirm), in uncontrolled sighted listening. Arguing that this weak data point discredits a controlled, rigorous double-blind listening test is beyond ludicrous.
 

tuga

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#12
It disappointed one listener (i.e. @amirm), in uncontrolled sighted listening. Arguing that this data point discredits a controlled, rigorous double-blind listening test is beyond ludicrous.
It's been 16 years since that test. Is it ludicrous to conceived that the M16 could be a better speaker? Or do you expect loudspeakers with similar Spins to sound the same?
 
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#13
If you have been reading our speaker reviews, you have no doubt seen the "Preference Scores" for speakers. This was ground breaking research by Sean Olive published back in 2004 with the goal of predicting listener preference using anechoic chamber speaker measurements. Seemed like an impossible task but Sean pulled it off going beyond people's intuition that "everyone prefers a different sound." Clearly if we can predict preference based on measurements, then it is listener independent.
That was not my impression. Their goal was to determine whether a "neutral" speaker could be mass marketed, not whether everyone prefers the same sound. In context of comparing model prediction vs actual preference rating, the actual preference rating is an average.

Looks like they are not interested in speakers anymore, but Sean Olive gave presentation at last Head-Fi about segmenting headphone users based on their 3 band EQ preferences. I think there is a paper for it. They have also found differences based on age, gender, etc.

There are none as yet. I expect this to be a living research thread where we discuss what we have found here, and whether we can better rationalize speaker preference from measurements. The preference score for this speaker will be high (@MZKM will post shortly) putting me once again at odds with it. We have to figure out why before I lose all face.
Nothing to be embarrassed about. Personally I enjoy reading owner impressions and speculation even though they are not broadly useful from "audio science" point of view. If all we did here was audio science, it would be a dead forum for sure.
 
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amirm

amirm

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Thread Starter #15
A factor remains that my hearing acuity for distortion/small detail is well above average due to extensive training. Harman listeners did not have such skills. So it is entirely possible that what bothers me doesn't bother hardly anyone else.
 
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amirm

amirm

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Thread Starter #16
That was not my impression. Their goal was to determine whether a "neutral" speaker could be mass marketed, not whether everyone prefers the same sound.
Computation based on anechoic chamber measurements -- within degree of error -- guarantees that.

Many follow up studies have shown the same.
 
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#17
It disappointed one listener (i.e. @amirm), in uncontrolled sighted listening. Arguing that this weak data point discredits a controlled, rigorous double-blind listening test is beyond ludicrous.
That model is like 20 years old. It's missing a lot of sample data. In fact, Floyd Toole or Sean Olive has said that earlier experiments were not successful due to too much variance between speakers. So what does that say about another 20 years of performance improvements...
 
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#18
Computation based on anechoic chamber measurements -- within degree of error -- guarantees that.

Many follow up studies have shown the same.
I agree. My point was that it did not test "everyone prefers a different sound".
 

Laserjock

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#19
Too funny, I still have these as side surrounds.
They are way too high and mounted on the wall with “pivot” ball mounts so I am able to point them somewhat.
I couldn’t tell you what year I bought them but I can tell you it was from Circuit City since I got them at a deep discount.
(One wouldn’t play and I went and grabbed a screwdriver from the car and the sales rep and I opened it up and I reattached a spade lug that had came off.)

Chris
 
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#20
This is a joke, right? Do you realize that you're commenting on the exact speaker model that was deemed to be superior to 12 others in a rigorous controlled double blind test, and is part of the initial set of speakers that was used as a starting point for the Olive preference model? This is actually one of the worst possible examples you could base this argument on!
Tuga is correct, strictly speaking: because it is possible to create a mediocre sounding speaker with excellent spinorama measurements, the spinorama is inadequate to characterize speaker quality.

But it is a weak way of being right. Few would disaree, least of all Olive and Toole. Tuga makes no argument that Spinorama is not the best available estimator of preference, an important guide to engineering speakers, or an important consideration in purchasing speakers. (And far better than "X sounded better than Y to me or others" in a non-blind test, doubly so if position and room are not strictly controlled.)

All models of reality are wrong; some are useful. We should aspire to more useful models.
 
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