MEASUREMENTS: Room acoustic absorption panels... (GIK Acoustics Freestand)

"... of course you realize it won't sound exactly the same in your listening room, sir ..."

In the last few months, I've been doing more with REW measurements and examining the acoustics in my room, culminating in implementing digital room correction with my computer audio playback. It is because of this that I made the posts recently looking at speaker cables and the effect of speaker grill(e)s. Along the way, I also measured the effects of a couple of simple acoustic panels I have in the room to objectively examine the outcome.

MUSINGS: Digital Filters Test discussion, and a 192kHz down-sampling setting suggestion...

Well, I guess I am flattered that the results of my recent Digital Filters Test got attention on AudioStream (Stereophile affiliate). The other day, Michael Lavorgna posted an entry entitled "The Trouble With Audio Tests" including a few quotes originating from my INVITATION to the test as well as my ANALYSIS posts.

I'm going to start today's entry addressing some of his thoughts on the matter and how I view tests like this.

First, let's just start with the quote from Ernest Rutherford (1871-1937) brought up by Mr. Lavorgna: "If your experiment needs statistics, you ought to have done a better experiment."

The Linear vs. Minimum Phase Upsampling Filters Test [Part III]: SUBJECTIVE IMPRESSIONS

This is part 3 of the results from the test of digital filters which began with Part I (RESULTS) and follows Part II (ANALYSIS).

As usual with these tests, I provided the respondents with an opportunity to describe what they heard when comparing the two samples (linear phase vs. minimum phase upsampling). In this portion I will collate the responses into what people described as the sonic difference and try to classify the responses to the type of upsampling setting for each of the samples... By doing this, I think one can get a sense of whether there is any subjective consistency and also an idea of the variability of subjective opinion. I have put my editorial comments in brackets and italicized.

The Linear vs. Minimum Phase Upsampling Filters Test [Part II]: ANALYSIS & CONCLUSIONS

This post is a continuation of RESULTS: The Linear vs. Minimum Phase Upsampling Filters Test (Part I) where I had already summarized the rationale, procedure, and description of the 45 test respondents including basic demographics, equipment, and raw results.

IV. Analysis

In this segment, let's try to ask some questions to see if we can come up with answers on the significance of the findings themselves. I think the best way to interrogate the data might be to ask a few questions and see if an answer can be teased out...

The Linear vs. Minimum Phase Upsampling Filters Test [Part I]: RESULTS

I. Background

Well, the time has arrived to open up the covers and see what the data reveals!

As a recap, I direct you to the post "INTERNET BLIND TEST: Linear vs. Minimum Phase Upsampling Filters" where the test was introduced and invitations sent out for participants to be involved. In preparation for some of the discussions here, I invite you to read up on an excellent "primer" on digital signal processing done by Kieran Coghlan ("Up-sampling, Aliasing, Filtering, and Ringing: A Clarification of Terminology") published on Secrets of Home Theater and High Fidelity in May. Note that digital processing affects both audio and visual technology, hence the discussion applies to 4K video as much as it does to hi-fi sound. In it, he talks about the "Fourier pairs"; functions have both time and frequency domain effects. Simply put for us in audio as it relates to this test, the steeper the DSP function in the frequency domain (eg. a steep "brick wall" filter), the more the effect in the time domain (ie. ringing). Here's a chapter in the book The Scientist and Engineer's Guide to Digital Signal Processing for those who want to go into even more of the mathematics.

The reason I want to explore this in a blind test is simply because time domain plots of discontinuous signals as produced by DAC upsampling antialiasing filters (generally presented as an "impulse" / Dirac delta function plots) are often used to portray the reputed benefits of various digital filters in the audio world. Furthermore, there are those who write about and suggest that differences in upsampling digital filter parameters affect the sound in very substantial ways. The idea that if we decrease ringing, especially the pre-ringing prior to the main impulse signal, could lead to significant improvements in sonic quality and that it is desirable to aim for the use of minimum-phase filters (and by extension, perhaps it would be good for the audiophile to purchase a DAC that has this feature). Post-ringing is said to be less problematic as auditory masking reduces audibility.

MUSINGS: On Audiophile Debates and "Placebos do in fact work..."

From drugsdb.com.

Let's think for a moment what "audiophilia" is about...

'We' love music so the likelihood is that 'we' have lots of albums to listen to. That's one of the great things about computer audio - a unified, easily accessible library. (This is of course not necessarily the case for everyone.)

'We' enjoy talking about hardware that can make the sound better. 'We' in fact often spend a lot of time considering how to match the pieces of an audio system to extract the most out of the collection above.

'We' argue about what's "best" in terms of the hardware because 'we' are passionate about the pastime and it is fun to find ways of making things sound better. When passionate about something, natural human biases (especially among men!) will result in arguments, disagreements, and debates, does it not? Just ask the guys rooting for their favourite team or the "friendly" competition between nations in international sports... The way I see it, there's nothing wrong with this. Debate sparks thought, hopefully ideas which come to fruiting with advancement. Of course, sometimes things do turn ugly and we see unfortunate brawls or riots with alleged fouls or outright unsportsmen-like anger or hatred. Last I checked, nobody got murdered or trampled to death in audio-related debates thankfully.

ANALYSIS: DSD Conversion Impulse & Spectral Display... Another few images for completeness!

A cool example of the "Spectral Frequency" display - from Adobe.

Okay guys, I actually wrote the text that follows 2 months ago before the Digital Filters Test. As happens sometimes, a post can get lost in the "draft" bin and later found. It refers back to the DSD-to-PCM analysis series from April:
ANALYSIS: DSD-to-PCM Conversion 2015 - Windows & Mac OS X
ANALYSIS: DSD-to-PCM 2015 - foobar SACD Plug-In, AuI ConverteR, noise & impulse response...

Consider this as part 3 of the 'trilogy' for this week as I continue to work on the results of the recently-closed Digital Filters Test.

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I was reminded recently by Wombat in his post here that we can have a look at the spectral frequency display as well when assessing sonic data in the audio editor. Also, Mnyb talked about the low-pass filtering in SACD players and what "standards" were used. Well, I don't know about the formal standards, but the first Sony SCD-1 SACD player back in 1999 had a defeatable analogue filter placed at 50kHz and according to the DSD Wiki, all SACD players were supposed to include this "optional" filter. I know a few people on audiophile forums suggest they subjectively preferred the filter be turned off.

Digital Filters Test CLOSED & What Do We Have Here? [Updated]

June 25th has arrived!

As planned, this is the close-off date of the Linear vs. Minimum Phase Digital Filters Test. I hope everyone who wanted to participate got a change to have a good listen and submit their results! Thank you to everyone who did this. As usual, I'm very appreciative of the time and effort to download, load up the files, and of course the careful listening!

So, I will take the next little while to process the numbers and see what I come up with. I can share with you though that in total, I received 45 responses. This is actually close to what I imagined (about 50) based on past experience. The procedure isn't as simple as something like the 24-bit or MP3 tests done in previous years so I certainly did not expect the same kind of response.

Looks like North Americans "win" in terms of number of entries by geography :-). 62% (28) of the respondents were from North America, followed by 29% Europeans, then Asians and Australians the same (4.4% each).

Okay... I will post up the data / analysis / and conclusions when I get the information processed!

Now, on a side note... What do we have here?

MUSINGS: Audio Cables Summary, Non-Utilitarian Functions & Scientific Falsifiability

At this point, I believe I have examined all the audio cable claims I need to for awhile (along with some related items):

Analogue:
RCA interconnects
Crystal Cable CrystalConnect Micro 1m RCA (added Nov. 2016)
Speaker cables (Canare 4S11, Kimber 8TC, zip cord, bi-wiring)

Digital:
Coaxial
TosLink
USB (generics, Belkin Gold)
USB 2 extension with ethernet adaptor
Corning optical USB 3 extension
USB Hubs and 8kHz packet noise

Local - Ethernet
Internet - Ethernet

HDMI (ION, Energy, adaptor)

Power:
Power cables (used with DAC)
Power cables (Synergistic Research with Oppo BDP-105)
Belkin PureAV PF60 power conditioner

MEASUREMENTS: Speaker Cables / Wires (Canare, Kimber, and the "Frankenstein" Zip Cord)

Awhile back - in October 2014 to be exact, I spoke a bit about speaker cables, posted some electrical data, and made myself a pair of 4' Canare 4S11 bi-wireable lengths with locking banana plugs to use at home. These are the black cables you see above to the right. I've been happy with them since and as I noted in that previous post, I heard no discernible difference compared to standard 12G copper zip cord nor did I feel bi-wiring made a difference so I reinserted the speaker jumpers to effectively make this a single 11G cable (no risk losing the jumpers!).

However, I presented no measurements at that time. As I mentioned last week, since I've been doing some room measurements lately (which I will talk more about in a future post), I figured it was time to put my impressions to the test and see if I can detect a difference objectively with speaker wires. Today, I present a few measurements in 2 parts - Part I is with a very "poor" zip cord (the above image, left cable), and Part II with a well known and "audiophile approved" commercial cable.

MUSINGS: On Music Streaming, now that Apple's in the game...

So, the big news this week is Apple and the streaming audio announcement; Apple Music. Of course music streaming services have been around for years: Spotify, Pandora, Rhapsody, Google Play Music, XBOX Music, Rdio, KKBOX (Asia), etc... Take your pick. Oh, let's not forget the mother of all media streaming - YouTube! Then there's also the FLAC lossless audiophile "darling", Tidal.

As usual with Apple announcements, it seem like the word "revolutionary" gets used rather liberally (along with describing objects as having "magical" properties). According to Apple, this announcement is "revolutionary", just like MQA from Meridian is "revolutionary" I guess. Lots of revolutions going on these days :-).

Supposedly this new Apple Music service will be streaming 256kbps AAC (not verified by Apple yet) and as expected from the fringe, some folks still are up in arms over the use of lossy compression with streaming services. It's as if lossy compression is morally evil and the mere mention automatically taints the product as deserving to be treated with disdain. Well, I guess I just don't see/hear it that way (the times I actually stream music off the Internet).

MEASUREMENTS: The Effect of Speaker Grills...

"Clothed" or "Naked"... What's the difference?

A quick measurement for this week...

I was curious the other day as I was doing some room measurements what effect speaker grills make. My Paradigm Signature S8 V3's have typical fabric and plastic grills up front. Simple question - How much difference does the grill make to the sound of the speaker?