Saturday, 31 August 2019

MEASUREMENTS: Speaker Impedance - Part 2; sealed, ported, and a few of my speakers...


A couple weeks back, I started discussing speaker impedance curves and how one as an audiophile hobbyist might want to measure these ourselves. There are thousands of speaker models out there and while some in the audiophile press do a good job with providing objective results (like Stereophile), sadly, most magazines do not publish the information, and most manufacturers do not openly provide detailed specifications either. What else then can one do but measure it ourselves?!

Today, let's continue to explore the speaker impedance measurement graphs and see what else they can tell us using some of the speakers I use at home regularly...

Saturday, 17 August 2019

MUSINGS / DEMO: Why "Bits Are Bits". Let's not add unnecessary fear, uncertainty, and doubt.


Something I have noticed over the years commenting on the audiophile hobby has been how incessant and persistent various themes tend to be. Just like the apparently never-ending arguments of "digital vs. analogue/vinyl", or "CD vs. hi-res", or "subjective vs. objective", there has been this mostly friendly banter between those who feel that essentially "bits are bits" vs. those who think there is significantly more to digital transmission than bit-accuracy.

Seeing recently this article "Why the 'Bits is Bits' Argument Utterly Misses the Point" from Upscale Audio published compelled me to write this post to explore the topic further with a review of measurements and some demo tracks for readers to listen to themselves. I don't know how long the Upscale article has been on the site since there's no date or author listed, and was only made aware of it through the Darko.Audio Facebook page (it seems Mr. Darko felt the article was accurate, really?).

While the article claims that some people have "missed the point", let us examine their points and see if perhaps it might be the author(s) that are a bit too aggressive in making these arguments. After all, it is 2019 with decades of development in digital technology that impact our lives in more sophisticated ways than just audio reproduction. It's hard to imagine there are huge lacunae in our knowledge of digital communications and digital-to-analogue conversion of audio frequencies.

Sunday, 11 August 2019

MEASUREMENTS: Speaker Impedance - Part 1; measurement box, dummy loads and single speakers...

As you know, speaker impedance is not a "flat" resistance across the audio spectrum as one would find with a resistor. Rather when we measure the speaker load, we see fluctuations affected by the voice coils and crossover networks inside that speaker "box".

Remember that the electrical signal that represents "sound" are alternating waveforms. Thus we are in the domain of AC analysis when talking about the electrical properties of speakers which are typically "seen" by amplifiers as low impedance and complex "reactive" loads that will unevenly affect current and voltage due to capacitance and inductance. (For a good review with some math on the concept of impedance, check out the series of videos here.) As you've probably seen over the years, an important speaker measurement that can help us understand performance and the demand from amplifiers is the impedance curve (and the derived electrical phase angle).

As a hobbyist, measuring speaker impedance with excellent resolution is not difficult these days. We are blessed with free/user-supported software like Room EQ Wizard (REW) that can get the job done quickly and accurately. What we do need to do is to rig up a "sense resistor" to an ADC measurement device for the software to do its "magic". Here's a little black box I put together recently to get it done:


Saturday, 3 August 2019

MEASUREMENTS: AudioQuest Dragonflies Reviewed! Dragonfly Cobalt, Red, and v1.2.

Audiophiles following the news cycle know by now that the new AudioQuest Dragonfly Cobalt is out. About 3 weeks back, I noticed out of the blue (no pun intended), almost all mainstream audiophile websites had a post or promotional "give away" for one of these! Clearly this made a significant splash in the collective audiophile psyche.

Over the years, I've reviewed and measured these little USB DAC devices going back to the Dragonfly v1.2 in 2014. More recently, I wrote a series on the Dragonfly Black in 2017 with a good chunk of that looking at MQA "rendering". Note that I don't have the Black v1.5 here for direct comparison and will instead refer to those older results and articles as appropriate.

Here then are the 3 Dragonflies (Dragonflys?) I have in for a listen and on the "test bench" for direct comparison. From left to right - v1.2 (released 2014), Red (2016, ~US$200), Cobalt (2019, ~US$300):


As usual, I will start with building up the objective results and then later in the post, I'll talk about subjective listening impressions and broader ideas. I know this sequence appears backwards compared to how audiophile reviews usually are structured. Most reviews typically start with background on companies, personal anecdotes, people involved in the product, rationale, etc. If one is fortunate, maybe a sidebar or graphs at the bottom of the review for objective results.

As a "more objective" audiophile, the typical sequence above is not how I would prefer to learn about a new product. There are often insights one can gain through disciplined objective evaluation one simply cannot get based on company literature or even just listening unless one were truly meticulous. Objective results apply to us all, while subjectivity is the domain of the individual. As such, technical adequacy and fidelity IMO are much more interesting and significant than a company's history, who the "guru" was behind it, or to be honest, what the reviewer "heard" or probably more often than admitted, thought they "heard"; I'd rather leave many of those items as sidebars.

Sunday, 28 July 2019

MEASUREMENTS: "Noisy" Switching Power Supplies vs. Lithium Battery Packs (12V battery with RME ADI-2 Pro FS & Topping D10 DAC results)

Perhaps we don't think about it much or give it enough credit. I believe one of the advances in the last few decades that has provided the foundation for technological progress we enjoy today is the lithium ion battery. Li batteries were commercially released in 1991 and since then, thanks to the energy density available, combined with increasingly efficient electronics, all kinds of things these days can run off battery power - cars being the poster-child of this advancement...

A few weeks ago, I showed the little Class-D amplifier system running off a battery. How about we try out my RME ADI-2 Pro FS on batteries:


What you see here is the device connected to the Talentcell 6000mAh 12V Li-Ion battery pack. Since the RME ADC has become my standard for measurements in the last year, I have wanted to make it "portable". Talentcell makes an even smaller 3000mAh 12V battery which would work fine. While a little larger in size and weight, the 6000mAh unit is still lightweight and will be able to power the ADC/DAC for >5 hours - enough for any recording and measurement I would want to do in a single sitting.

Tuesday, 23 July 2019

SUMMER MUSINGS 2: Multichannel and the audiophile. MCh streaming with a TV Box. And Thoughts on the Future...


Hope you're all having a great summer... I thought I should take the opportunity to respond to this comment from Steven on the blog post last time broadly and with more details:
Steven 8 July 2019 at 21:07 
What about surround sound? Some of us are into that stuff. ;>
It does change things slightly. USB and S/PDIF won't suffice for lossless 4.0/5.1/and beyond audio data. That leaves HDMI or analog, afaik.
Excellent points Steven.

Surround/multichannel playback is important and sadly rather neglected in the audiophile world. I saw recently that the TAS website posted this article on the "rebirth" of quadraphonic sound.

Hmmm, isn't this actually the "rebirth of the rebirth" of quadraphonic? As I recall, there was a rather significant thing among home theater enthusiasts and audiophiles called multichannel SACD and DVD-A around Y2K :-).

Saturday, 6 July 2019

SUMMER MUSINGS: "How Much Difference Does It Make?" - On Balance and Adequacy for audiophiles.


The other day, I was reading Jim Austin's "As We See It" post on Stereophile titled "How Does the Music Make You Feel?". A relatively sensible article putting forward his and the magazine's perspective around finding "balance" between the subjective and objective sides of the audiophile pursuit. I agree with the central thesis, ultimately it is a subjective decision how one wants to spend time engaged in this hobby based on the emotional effect of music (I hesitate a little to say "music" here because let's be honest, not all audiophiles are in it for the music - sometimes it's the "sound" that's being sought). Music is art and appreciation of art will always be subjective, perhaps even wildly idiosyncratically for each person. Nonetheless, it's not that simple is it if we "look at the forest instead of the trees"? Let's take a higher level perspective and consider the audiophile hobby as a whole, rather than the audiophile him/herself. Are there some principles we might want to keep in mind?

Remember that what I've called "hardware audiophiles" are actually the niche hobbyists Stereophile is speaking and advertising to. I don't think Stereophile is of much interest to the multitudes of "music lovers" who probably are quite happy already with decent bitrate MP3 streaming over cell phones. As discussed before, these two hobbies intertwine but IMO are not the same. In every Stereophile issue, while some pages are dedicated to albums, music reviews, or maybe interviews with artists, the contents mostly discuss hardware products used in reproduction of the music. Our emotional response to reproduced music is a combination of the artistry in the music and science of reproduction. The audio devices used have technical characteristics that are objective and can be measured. As an analogy, in the visual arts world, we might or might not subjectively like the Mona Lisa, but when we look at a reproduction (photograph or scan of it), we can certainly experience and measure the differences between high vs. low resolution copies, and we can comment on or measure other objective traits like color saturation, accuracy, brightness, contrast, etc. compared to the "real thing" under the lighting conditions at the Louvre.

In reading that article by Mr. Austin however, between the personal stories and opinions, I noticed that like in most editorials covering this topic over the years in magazines, it's side-stepping a very important dimension. Achieving "balance" is not just about the way it is done (subjective listening +/- objective measurements), but also about the depth of exploration from which we derive adequacy. In other words, it's not just about whether we subjectively look at a car/woman/man and be captivated by its/her/his beauty, or whether the thing/person is objectively faster/taller/shorter/skinnier, but rather, are these qualities "good enough" for our intentions?

Let's expand on this...

Saturday, 29 June 2019

LISTENING: Fully battery-powered wireless streamer & amplifier system (Yeeco - TI TPA3116D2, TalentCell 12V battery)


A few weeks ago, I read this review on an independent audiophile site about an inexpensive Nobsound Class D amplifier based on the TI TPA3116 chip. I was curious so I ordered an equivalent one off Amazon - the little Yeeco Bluetooth-capable amplifier shown above with box contents including the 12V power supply for <$US32 (for an even cheaper package, here's one without the switching power supply, <US$25).

As you can see, the reviewer linked above gave the product some positive comments on the sound. I was curious to listen and since we know that Class D amps like these are very efficient, how about we run the playback system - music streamer to amp to speakers - completely wirelessly and battery powered for a listen also?

Saturday, 22 June 2019

MUSINGS and LISTENING: On Absolute Polarity / Phase... (And on the joy of the modern audiophile.)

Hey guys and gals, I thought for this post we'll spend a bit more time on the topic of "absolute polarity". As you can see from the post last week in the comments, our man in Japan Yamamoto2002 posted a link to his page where he has an interesting test signal for all to listen to.

If we look at the test signal he used, it's an asymmetrical waveform where half of it appears to be a standard sine wave, the other half has been "flattened" off which results in numerous harmonics if we are to display it on an FFT. One of the files is simply the inverted version of the other to test whether this polarity change is audible. Notice that the waveform is bandwidth limited, and there is no "ringing" after going through a digital filter.

Saturday, 15 June 2019

MEASUREMENTS: Topping D10 DAC. (And a few words on "absolute polarity / phase".)

Hey guys, getting busy around here as I'm preparing for summer holidays coming up in a couple of weeks :-).

I did want to post a "quick" report however on the Topping D10 DAC (<US$90) I got last week... It's for an upcoming project of sorts which I'll post on over the months ahead. What I wanted was a DAC that could be powered off USB, reliable with Window and Linux compatibility, that's reasonably portable, and of course of high signal accuracy.

Notice the DAC manual shows some AP measurement graphs... I guess Topping believes in showing objective accuracy :-). Nice.

Saturday, 8 June 2019

GUEST POST: Why We Should Use Software Volume Control / Management by Bennet Ng. (Plus discussions on resampling options, true peaks, etc...)


I received an invitation from Archimago to write something about volume control. While I am of the opinion that digital and analog volume controls can coexist to achieve an ideal gain stage, this article is mainly about PCM digital volume control.

The basic conclusion we can say regarding digital volume control is that as long as the playback device has higher bit-depth than the file source, it is possible to losslessly reduce the volume of a file until the playback device's bit-depth limit is reached. For example, with an ideal 24-bit device, it is possible to playback a 16-bit file 48dB lower without losing quality, because one bit has about 6dB of dynamic range (the exact formula of bitdepth and dynamic range is 6.02*n-bits + 1.76).

Saturday, 1 June 2019

POLL RESULTS: Music streaming service adoption among audiophiles in 2019...

Click on image to zoom.
Yeah, I know. Music streaming as a subscription model is the latest "revolution" for music lovers. This is why I decided to put up the recent poll in mid-March while we were concurrently also running the blind test as reported on in the last few weeks. Above, you see the overall results based on the visitors to this blog.

Remember that for the poll, I allowed voters to select up to 3 options. As a result, even though there were 616 respondents, a total of 809 selections were made. This means that up to ~30% of people selected more than 1 option and these are represented in the percentages above.