Saturday, 31 October 2020

qSpins: AudioEngine A2 & Edifier S2000 Mk III 2-Way Bookshelf Speakers

Hi everyone, thought I'd just publish a couple of "qSpins" today as I might be away for a little bit to attend to other duties in the next couple weeks.

In the last while, I've been looking at getting another pair of speakers on my computer workstation desktop. Here's basically what my desktop speaker system has looked like for years:

Saturday, 24 October 2020

MUSINGS/HOW-TO: Raspberry Pi 4 "Touch" Audio Streamer, and CRAAP settings! ;-) The decline of public feedback, virtual showrooms, value-added content and Darko Audio?

Left - Raspberry Pi 4B, Right - Raspberry Pi 3B. Heatsinks installed on both boards.

Back in August, I wrote an update on building and running the of Raspberry Pi "Touch" audio streamer with RoPieee software. The article was still written with the Raspberry Pi 3B(+) in mind.

Well, on Prime Day recently, I was able to get a Raspberry Pi 4, 4GB "Starter Kit" for a price I could not resist. It's nice to have all the parts including the appropriately sized heatsinks, ready-to-use microSD card, and 5V/3A USB-C power supply. For now, I have no need for the Pi 4 case and the micro-HDMI cables can go in my box of miscellaneous cables.

For audio streaming purposes, a basic 2GB Pi 4 kit (<US$55) would be even cheaper and works just as well. Given the minimal difference in cost, no point going with a 1GB model although that would still be fine - remember the Pi 3 was limited to 1GB. There is also an 8GB Pi 4 but that's a huge amount of memory for just an audio streaming "appliance"!

Saturday, 17 October 2020

Musings/Measurements: quasi-Spinorama "qSpin" & the KEF LS50 bookshelf loudspeaker...

Auditioning the KEF LS50 Black Edition, powered by SMSL SA300 Class D amp on computer workstation.

With autumn here, sunlight hours reduced and looking towards the rainy months ahead, I thought it would be good to start expanding measurements and be a bit more "serious" with evaluating loudspeakers.

As you know, speaker measurements have been done since the start of the audiophile hobby and there are all kinds of ways to get the job done to varying levels of precision and reliability. Stereophile has been doing this for years with John Atkinson's use of the MLSSA (DRA Labs) system as he summarized in this review which formed his 1997 AES paper. More recently, it's great to see Audio Science Review's use of the Klippel Near Field Scanner (NFS) for many speaker measurements already!

For many of us interested in speaker performance, probably introduced to the ideas with Floyd Toole's book Sound Reproduction - Loudspeakers and Rooms (first edition 2008, now in 3rd edition 2017), there has been a rise in loudspeaker measurements using the "Spinorama" technique. This measurement method plus its standard representation of data has since becoming codified in the ANSI/CTA-2034-A "Standard Method of Measurement for In-Home Loudspeakers" (you can get a copy of the current CTA-2034-A R-2020 here), first published in 2015.

Saturday, 10 October 2020

Further Explorations into "Intersample Overs" - Resampling/Downsampling & De-Clip by Charles King

Greetings everyone. It's great to interact with some of you over the years around contents I've posted in this blog. As you perhaps know, recently, I talked about resampling hi-res audio files in my article on "Post-Hi-Res" with the idea that the vast majority of albums we download as supposedly high-resolution content simply do not warrant the file size or bitrate. As such... I routinely just bring them back to 16/48 or 16/44.1.

Here's an interesting comment by Charles King on this and his explorations of the topic:


Hi Archimago,

I was a bit taken aback on reading your 25 July post in which you talked about a need to guard against intersample overs when downsampling hires files. I've collected quite a few albums in hires over the years, often to check if I could hear any difference (I can't, and have given up on that) or to see if they provided better mastering (occasionally true, though in some notable cases the mastering is audibly worse). Since I don't want to litter my long-term storage with gigabytes of useless data I end up downsampling these to 16/48 in Adobe Audition (which is rated as having one of the better resamplers) and then compressing to variable-rate AAC (which is transparent to me).

Saturday, 3 October 2020

HOW-TO: CD Pre-Emphasis & Using SoX De-Emphasis. (And the decline of physical media with vinyl revenue > CD now.)

Have you ever ripped or downloaded an old music CD that just sounds way too harsh? Sounding like the EQ is accentuated with too much treble?

Back in the day, a number of CDs were processed with pre-emphasis used and we can see at least a partial list of pre-emphasized albums here. Typically these would be early CDs from the mid-'80s although as per the list there are also a number from the late '80s and even early '90s.

In those early years, DACs were incapable of true 16-bit resolution and noisy analogue brick-wall filters added high-frequency distortions. As a means of improving signal-to-noise, they boosted the high frequency content and corrected the tone on playback (see this Hydrogen Audio FAQ on Pre-emphasis). As you're probably aware, a CD doesn't just contain the 16/44.1 audio data but have encoded within each "frame" 8 bytes of CIRC error correction and another byte of "subcode" data which can be thought of as "control data"; like a precursor to today's much more complete metadata. One of the subcodes is the "pre-emphasis flag". When activated, a CD player will engage its "de-emphasis" circuitry/filter. These days, DAC chips themselves can implement digital de-emphasis as part of basic functionality.