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some in the audiophile press do a good job with providing objective results (like Stereophile), sadly, most magazines do not publish the information, and most manufacturers do not openly provide detailed specifications either.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...

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

[Available as audio podcast summary.]

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.

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:

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.