Hopkins' System

There is also a lot of discussions out there as to whether it is "better" to listen to mono with a single speaker or with two speakers.

One thing is certain, you will never get with two speakers the clarity offered by mono recordings on a single speaker, even with your speakers perfectly symmetrical to your listening position. Our ears move around when listening, and the room is never perfectly symmetrical, even if the speakers are with respect to the listening position.

Using a single speaker will obviously allow for much more freedom in speaker placement within your room. Chances are you will have better room interaction with one speaker than two. This is of interest if you plan on using a mono speaker in addition to your regular stereo speakers.

One downside of using a single speaker is that SPL is lower, and you will have to turn the volume up a little. I'll assume most of us have amps with sufficient headroom to do that.

Some may still prefer two speakers over a single speaker. We are so used to stereo, that listening on a single speaker may be unsettling at first. But once you get used to it, it is very satisfying, in my opinion.

Depending on your musical tastes, the share of mono recordings in your music collection will vary greatly. Given my tastes, I have a large number of mono recordings. When given the choice, I will always prefer a mono release to a stereo version of the same album. But that's just me...

A single Altec 755C speaker playing a mono recording provides a surprisingly spacious sound with excellent clarity.

What's not to like? Limited frequency extension? Well, chances are that these mono recordings are not going to exhibit thunderous bass and shimmering highs anyway. The silver lining is that you have less to stress out about and you can simply relax without wondering whether your speakers are accurately reproducing 20hz or 20khz signals :)
 
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So I wrote a script (javascript) to store the RMS ("Root Mean Square") level of the delta between channels for all tracks in my collection, as calculated by FFMPEG. It should run for about 24 hours...

Screenshot 2023-12-27 111650.jpg

So far, I have about 10.000 tracks analyzed, and there are some interesting results.

This CD, for example: https://www.discogs.com/release/13452589-Lester-Young-Quintet-Complete-Live-At-The-Argyle-1950
It is available on Qobuz: https://play.qobuz.com/album/c5ucvm8grfipb

Recording is from 1950, in a club, and we can assume a single microphone was used - so it should be mono. However, tracks 9-12 have double the RMS level (of the "delta" between the two channels) than the rest. When you look at the two channels in Audacity you can see that one is simply louder than the other - this can be confirmed by listening to the "delta" between the two tracks resulting from the inversion of one channel: it contains the same audio as either channel. So if one channel is significantly louder than the other, how can we expect to get good stereo sound?

The sound quality of the record in this example is not very good anyway, but there are many other examples. I will post a few more when the scan is complete.
 
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Here is an interesting article on channel imbalance of Mono releases of the Beatles: http://comprehensivebeatles.blogspot.com/2010/12/imbalances-on-beatles-mono-releases.html

The article give a comprehensive list of what "could go wrong" in the production chain. My concern is not so much the quality of the stereo reproduction - imbalance is not always perceptible - but deciding which albums I can listen to with one speaker - which is specifically challenging when you are dealing with a digital collection.

I have scanned already 23672 tracks (a little over half), and so far:

- 42% of the tracks have a "delta" of less than 50db, meaning they are "quasi mono" - one channel is probably slightly higher than the other, or some noise differences were introduced differently on each channel at some point, but you will (most probably) get all the musical information if you only listen to one channel

- of this 42%, only 20% are true Mono (left and right channel are strictly identical).

Not sure this is of interest to anyone else, as I believe most people who listen to mono on single speakers are probably using mono LPs, not digital!

I don't know of any music application that has build-in track analysis features (ex: loudness calculation) that provide these types of indicators.
 
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Here is a bizarre one, taken from this CD: https://www.discogs.com/release/11082389-Dodo-Marmarosa-Trio-Complete-Studio-Recordings
Available on Qobuz: https://play.qobuz.com/album/0884385437343

The first CD includes sessions from 1946-1950: https://paulstephane.github.io/album#1660231653739

All tracks on this CD - except for one session, tracks 5-15 - are perfect mono (left and right channel are identical).

Tracks 5-15 have large differences between the left and right channel, as can be seen in this example:

(1) Original two-channel track from the CD: https://storage.googleapis.com/cloudplayer/samples/Compadoo Stereo.wav

(2) Left channel only (playing on both channels): https://storage.googleapis.com/cloudplayer/samples/Compadoo Mono.wav

(3) Track produced by adding the inverted left channel to the right channel: https://storage.googleapis.com/cloudplayer/samples/Compadoo Left inverted & Right.wav

This is a radio transcription recording: https://en.wikipedia.org/wiki/Electrical_transcription. So the recording was never issued commercially and you can only listen to it today from a digital source...

The original track (1) sounds like there is reverb. Perhaps some slight delay? But zooming in on the signal in Audacity, it is hard to discern any pattern between the left and right channel:

Compadoo.jpg

Zooming in further on one segment:

Compadoo2.jpg

So what's going on? I don't know... Why does adding the inverted left channel to the right channel result in basically the same sound as a single channel - are they out of phase? What I do know is that I prefer listening to a single channel (2), than to the weird version on the CD (1)...
 
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Now that I have tagged my entire music collection with that RMS indicator, I can easily select albums to listen to in mono with a single speaker. When adding a new album to my collection, the calculation is automated and stored in my database.

Here is an example of one of my album pages:

Screenshot_20231229-000611.png


The number in the brackets by each track indicates the RMS of the relative loudness of the delta between channels (so -62db in this example).

Roughly 50% of my albums are effectively mono. RMS less than 30 is stereo, greater than 40 mono. There is a grey zone between 30-40, but few albums fall in that category. By listening to the delta in Audacity you can easily figure out what the engineers were up to. It is often amusing.

For nearfield listening, the 755C in the Silbatone cabinets work very well. I have decided that I will only make a single open baffle for the 755C, using both sets of wood panels I purchased, in order to get a sturdier panel. They are quite large, and I won't really be able to fit both in my living room.

Listening to mono I realize now that stereo does not really add anything in terms of my appreciation of the musical content. Perhaps this is silly to say, as it is so obvious?

The sense of "envelopment" that you get with a good stereo mix is "cool", but does it really add anything? Not to my ears. With a single speaker the connection to the music feels like it is more "direct", there is less distraction.

The inventor of stereo (Alan Dower Blumlein) came up with the idea in the 1930s at the movies as he found it annoying that the fixed source of sound did not follow the actors' movements on the screen.


For us listeners, sitting comfortably in our chairs in our listening space, is stereo really of any value?

I assume that the same "cool" factor would be even greater with multi-channel audio.

With music that I really "dig", stereo is superfluous. It also brings a lot of headaches. Witness for example the efforts made by some to negate cross-talk...

As I am typing this I am lying comfortably on my couch with my speaker facing me at the end of the couch. KISS!

Obviously a lot of the music I love is only available in stereo, so I will live with two sets of speakers, and use them depending on my mood.

So 2023 has been a really interesting year for me - in terms of "audio". I have come to better understand my own preferences, and have found the gear that match my tastes. There is nothing universal about the choices I have made - understatement of the year when you read through this post :)

On a side note, I was given a small Christmas gift by a fellow jazz collector (a serious one, not an amateur like me): an unissued 7 minute 1941 recording in a NYC jazz club (Monroe's) of one of my favorite musicians. The sound has plenty of hiss, but the music is sensational - it bought tears to my eyes. Can someone please come up with a time machine?
 
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Non-audiophile friends are always curious to listen to my open baffle speakers. Busted them out last night and finished the evening at 2 AM listening to this timeless 1938 rocker:


A fun album of his, is "Pete's Blues" - hailed as the first "concept album", and dating 1946:

 
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Sarah Sings Soulfully - Round Midnight
Recorded in 1963


From this nice box set:


Original album:


The cast (from the Wikipedia page):
Sarah Vaughan - vocals
Teddy Edwards - tenor saxophone
Ernie Freeman - electronic organ, double bass, guitar
Carmell Jones - trumpet
Milt Turner - drums
Gerald Wilson - arranger

The Wikipedia credits are probably wrong as Ernie Freeman is not playing organ and bass simultaneously...

No opportunities for instrumental solos in this version, the spotlight is all on Sarah Vaughan, but who is going to complain?

It is really fascinating how she seamlessly changes registers and rhythm. Check out for example her delivery of the sentence "Just let our love take wing..." around 2:35. Wow!

LPs were issued both in stereo and mono versions. On CD, only stereo versions have been released, I believe. I don't know why, but this is often the case.

I would be curious to listen to a mono LP, but am happy with the stereo digital version.
 
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An audiophile test track. It even says so on her web site (https://www.anetteaskvik.com/):

"Liberty has frequently been used to demonstrate good sound on hi-fi equipment all over Europe and USA"

It's hard for me to get excited about "sound", but maybe some will find it interesting.

Happy new year!
 
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Speaking of Nat King Cole and unreleased recordings, 2024 starts strong with this latest article by Lewis Porter, in which he includes recently unearthed recordings with Cole and Tatum:


The first track is a 2 minute solo of Cole on "Tea for Two", and the recording quality is quite good. Set it on repeat - it does not get tiring!


Quoting Lewis: "If you’ve heard him play before, sit back and enjoy. If you haven’t, prepare to have your mind blown!"

The article is interesting, and will be followed up by more...

The man with golden hands (and golden voice):

Folder.jpg
 
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Joe Thomas Orchestra - Black Butterfly - 1946


This is played from the vinyl Keynote Collection:


It has been released on digital as well - minus the alternate takes.

Here is the track on Qobuz: https://open.qobuz.com/track/94882964

In the liner notes, Dan Morgenstern explains: "Ellington knew and approved of this interpretation of his beautiful melody, as well he should have."

Let's compare it to various Ellington versions.

Original recording by Ellington in 1936:


He recorded it in a small group setting in 1940 with Cootie Williams on trumpet:


He resurrected it in the late 60s. This 1971 arrangement is nice, with Hodges on saxophone and Norris Turney on clarinet.


Joe Thomas' version is simpler as the focus is really on the soloists with background support from the rest of the band, but it has a very seductive quality, and his trumpet playing is superb.


The saxophone solo is Hilton Jefferson.


Piano solo by Bernie Leighton:

 
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PXL_20240103_114022257.jpg

Spending some time listening to the Dan Clark Stealth headphones, hooked up to the powerDAC-SX with a custom cable.

The level of detail, air, and dynamics are very impressive. They seem "neutral". They don't extend in the bass quite like my budget Sennheiser HD400 Pro, but are otherwise superior in every aspect, as one would expect from the price! They are also much better than the Dan Clark Aeon Black, which I own (and were a bit disappointing, to be honest). This is the best headphone I've heard - and I've heard quite a few...

Pairing with the powerDAC-SX is excellent. I don't have a conventional headphone amp to compare, but given what I am hearing, and what I recently heard from these same headphones in another (pricey) system, I trust that this is a pretty unique combination.

I took the opportunity to compare again different sources, and they all sound superb (including Qobuz, provided you compare exactly the same tracks). Nothing to worry about on that front.

Comparison with speakers is always interesting. There are limitations to both (headphones and speakers). These do remind me, once again, how difficult it is to achieve the same level of sonic "purity" with speakers - in any listening room.

The tonal balance and detail of the Altec 755C is really quite good, provided you don't play too demanding tracks (low and high frequency limitations). On some aspects, the venerable Altec are better! But headphones and speakers will always have their pros and cons. The open baffle do a good job as well. I think the open baffle would probably get a serious boost in quality with an extremely rigid baffle structure and driver bracing, but that's just a hunch, and not something I could ever verify.

It is also fun to listen to YouTube system videos with these, as it reveals so easily some of the limitations of the systems demoed (regardless of cost!)...
 
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Some quiet music to wrap up the evening:


Vince Guaraldi Trio - Recorded in 1956
This is a "drumerless" trio, composed of:
Vince Guaraldi – piano
Eddie Duran – guitar
Dean Reilly – bass

This was recorded with a Tascam DR-100MKIII recorder using its build-in microphones.
Playback chain, as usual is: album on my desktop PC with Logitech Media Server, streaming to the WiiM Pro, connected to ECDesigns' powerDAC-SX through a toslink optical cable. Single Altec 755C speaker.

The track is not "true mono", but close enough to play nicely through a single speaker - one of those mono recordings that got a slight imbalance between the two channels at one stage of the process.

The album is on Qobuz: https://play.qobuz.com/album/0002521861492


I recorded the same track with two speakers, if anyone is curious to compare:

Single speaker: https://storage.googleapis.com/cloudplayer/samples/Django Single Speaker.wav
Two speakers: https://storage.googleapis.com/cloudplayer/samples/Django Two Speakers.wav

The differences are more subtle on a recording than when listening "live".
 
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My cat has a pretty loud purr, but he's not going to top this one:


54,6 dB @1m !

Knowing cat purring has a frequency range of 25 to 150hz, we can wonder why our systems struggle to produce bass frequencies like these little fellows can!
 
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A 1958 10" LP passed on from one generation to the next:


Miles Davis - trumpet
Barney Wilen - tenor saxophone
René Utreger - piano
Pierre Michelot - bass
Kenny Clarke - drums

Vintage meets modern: Turntable - M2Tech Joplin Phono/ADC - Toslink cable to powerDAC-SX - Altec 755C
 
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