The Puzzle of HHT versus HTH

Are you open minded?  A classroom experiment I witnessed some years ago suggests probably not.  In this blog I am discussing subjects that may not have widespread agreement, such as 3 speaker versus 2 speaker playback, or thoughts about analog and digital audio.  And I wonder whether people really read and think about what I write, or if they ignore new information or ideas that might disagree with their existing beliefs.

More than 20 years ago, I attended a class by Professor Ron Howard at Stanford on “Decision Analysis” – I just checked and he still has a web page at Stanford so I guess he’s still teaching: https://engineering.stanford.edu/profile/rhoward.

In one lecture, Professor Howard posed a problem which, if I recall correctly, was titled something like “HHT versus HTH.”  The problem Howard posed is interesting because, in the classroom setting, and without a few quiet moments to reflect and think it through, it is a difficult one for most students to solve, including the bright master’s degree level students at Stanford that were the bulk of the class.  Therefore, and this is what was so fascinating, what is actually a question with a definite right/wrong answer takes on the characteristics of a subjective issue where people can “agree to disagree.”

Here’s the problem: two students (A and B) are brought to the front of the class, and each one is given a medallion with 2 sides – one side is “H” (head) and the other “T” (tails), and assume that in tossing the medallion the probability of H or T is equal.

Student A is to keep tossing the medallion until the sequence H then H then
T is achieved. 

Student B is to keep tossing the medallion until the sequence H then T then H is achieved. 

Question: who do you expect to achieve their goal in the least number of tosses: Student A or Student B or is it equal?

Of course, the interesting thing here is NOT the question, but the classroom
activity.  What Prof. Howard did after posing the question was to poll the class – how
many think A? how many think B? how many equal? how many are undecided? The
votes were recorded.  Then he asked a student in the audience to explain why “A” and another student to explain why “B”, etc.  Then he polled the class again, and again recorded the votes.The above process of listening to student explanations, polling the class, and recording the votes was repeated several times.  During the process, a lot of absurd and wrong statements were made, but eventually, one student figured out the problem, and stated the correct answer with a clear, logical explanation.

You might think that after the student stated and explained the correct answer, all the votes would switch.  But that did not happen.  The interesting thing?  Nobody listened.  That’s right, the votes remained fairly stable – people made up their minds initially, and then paid basically no attention to anything that was said.

Listening to the lecture and classroom participation/response was a
fascinating experience for me. Oh, and for those who care, it’s student B
who would be expected to first achieve the goal sequence.  Quick explanation: the two sequences have different symmetry properties, so that if we suppose both A and B miss on the second toss, A (who tossed HT) needs the third toss to begin his sequence, but B (who tossed HH) can start his sequence with the second toss, so B needs fewer tosses on average to achieve his sequence.

Digital Audio Basics: Stair Steps and Sample Rates

I took a prior stab at discussing vinyl versus digital audio, and I want to do a better job, but it’s going to take a bit of background discussion first.  I feel that to have an understanding of digital audio, and to discuss comparisons between say Vinyl and CD, or CD and high resolution audio, the concepts of sample rate and sample bits in digital audio need to be explored first.

I’m both excited and embarrassed to be writing this post.  I’m not Joe on the street, many years ago I took classes in digital signal and image processing, I earned graduate degrees in engineering from a prestigious university (although it has been a few years….), and yet I realize I didn’t have an intuitive grasp of some basic concepts.

I find that for myself, and for many others, concepts around digital images are more intuitive than concepts around digital audio.  For digital images, most of us know that a digital image is composed of little squares or pixels, each pixel is a single color, and the more the pixels the better the picture.  The color accuracy of a pixel is determined by the number of binary digits (bits) – the more the bits, the finer the gradation of a color from light to dark. A digital audio file is a lot like a digital image file, except that a digital image file has color data for points in space (the pixels), and a digital audio file has signal data (corresponding to the sound level) for points in time.  With digital audio, we have sound samples (corresponding to pixels), and binary data (bits) that determine the gradation of sound from soft to loud.

Most of us expect that, in audio, we get closer to the original signal by having more samples and more bits.  There are two issues that make our intuition not fully correct.  The first issue is the limited range of human hearing, and the second issue is the presence of noise, both naturally in our environment, and in all recorded audio.

First I’m going to talk about sampling rate, or how many audio samples are collected say every second.  The second issue, how much data (bits) is stored with each simple, will be considered in a separate post.  Let’s consider what happens when we sample a pure tone, say a sine wave.  Here I am not concerned with the precision of the sample, so we are not thinking about measurement error, round off error, or “quantization” that happens from using a finite amount of data to capture each sample.  Many readers will likely have seen a graph like below; suppose the smooth red curve is the original signal, the blue “stepped” curve shows the digitized version with say 10 samples, and the light green “stepped” curve shows the digitized version with say 20 samples.

Image

A graph like the one above is a source of a lot of wrong thinking about digital signals.  What the above implies is that 10 samples gives a crude approximation of the original signal, 20 samples gives a better but still crude approximation, and that if we continued to increase the number of samples we would eventually get to a pretty good approximation of the original signal.  But this is completely wrong!

There is a famous theorem, the Nyquist-Shannon sampling theorem, and I recently realized (courtesy of a video from Xiph.org), that I didn’t truly grasp it.  What the Nyquist-Shannon sample theorem says is that if the frequency content of the original signal is limited to some maximum, say M (e.g., say 20KHz for human hearing), and if we collect samples at frequency 2M, then we can perfectly reconstruct the original signal.  In the example above, then, going from 10 samples to 20 samples does nothing to improve the accuracy of the reconstructed signal, as the original signal was a pure sine wave  and with 10 samples we are already way over the minimum of twice the frequency of the original signal.

So why does it go against intuition to think that more digital samples means a closer approximation of the original signal?  Probably because (most of us) we tend to mentally think of a stair step reconstruction of the original signal from the samples! Where do the stair steps come from?  From the idea of sample and hold.  Remember, a sample is the signal value at a particular time, but we don’t know (or record) the signal value in between samples.  So the simple thing to do is just imagine that the signal does not change values between samples, which is how I drew the above graph.

The reconstruction of an analog audio signal from digital samples though, does not use sample and hold for the final result.  The conversion process is more like a kind of curve fitting, requiring there to be a smooth output that goes through the sampled values.  If there were sudden stair step jumps in the reproduced signal, those sudden jumps would have high frequency content beyond our maximum frequency M.

To demonstrate, and this is not any sort of rigorous proof, but a way to improve intuition, I used Microsoft Excel, and I created 3 data sets for a sine wave: the first data set (red) represents the original signal (actually with 100 points), then 20 sample points, then 10 sample points.  I displaced the curves vertically so it is easy to see, they all have the exact same shape, and that is what happens when a digital audio file is reconstructed to be an analog signal – one gets a smooth signal with no stair steps, and increasing the number of samples does not improve the smoothness of the final signal:

smoothedSamples

Again, for most of us, this result is highly counter intuitive – surely more samples must make for a smoother curve.  The point though is that we have taken samples of a bandwidth limited signal – a signal that has maximum frequency content M.  If there was something “unsmooth” or highly irregular looking going on between the samples, that would imply higher frequency content.  Since we are sampling at 2M or greater, we have captured enough information even with the “crude” 10 samples.

Said another way, if I had not displaced the three curves vertically, they would lie exactly atop each other, and THAT is what the Nyquist-Shannon sampling theorem states: we can exactly reconstruct the original signal from the sampled data provided we have sufficient samples, and sufficient for this example would be only 2 samples!

A brilliant demonstration of the above is given by Monty Montgomery in the following video:

http://xiph.org/video/vid2.shtml

or on youtube at

Now one question in my mind, and perhaps yours, is what about measurement error and measurement precision?  I recall taking a basic lab course many years ago, and one of the first things drilled in to me (not talking about digital audio here) is that all measurements have limited accuracy.  Suppose I want to use a ruler and measure the length of a piece of paper.  The ruler has tick marks say every millimeter, or every 1/16 of an inch, so that limits the precision of my measurements.  Not only does the ruler have limited accuracy, if I make multiple measurements, or if more than one person makes measurements, it is unlikely that we get the same value every time.

In a future post, I’ll touch on the issue of measurement error and use Microsoft Excel to create a simple spreadsheet and graph the effect of timing errors (recording a sample say at .1003 seconds instead of exactly at .1 seconds), and the effect of using varying measurement precision (more or less bits) for the samples.

Thanks for reading!

Review: Capital Audiofest 2013 (revised)

Last week I had a few hours to attend the Capital Audiofest (CAF) 2013 in Silver Spring, MD.  The website for this audio show is: http://www.capitalaudiofest.com/.  My time was limited, and there is a lot I didn’t see/hear, but I thought I would share some impressions.

Just as a quick background, I did attend a mainstream audio show in 2012, the Munich High End Show, and what impressed me there were the Cabasse L’Océan loudspeakers (most realistic sounding reproduced piano I have heard), and TAD loudspeakers, I forget which ones, and a relatively modest pair of Lindemann “Birdland” floorstanding speakers.  I guess I’m trying to say not everything sounded great to me, but those systems made an impression.

CAF is not a mainstream audio show, a significant number of exhibitors were showing off things like high efficiency speakers, tube amplifiers, and so on.  Stereophile, and The Absolute Sound, as well as some other bloggers have some show reports, so check those out for photos and more “professional” reviews.

For the most part I find the sound at these audio shows disappointing.  And it’s not necessarily the fault of the exhibitors, but if the exhibit room is small, then the setup is sort of like using speakers as headphones – nearfield listening – the speakers are severely toed in, the seating is close to the speakers, and the sound is probably best only for a few seats right in the center.   I much prefer far-field listening, I don’t want to be forced to sit in some “sweet spot,” or worse, a few seats over from a “sweet spot.”

To continue griping a bit, the volume of demos is almost always too loud for my taste.Audiophiles supposedly prefer natural sounding music, yet the volume of replay at these shows is often way above natural.  In a few rooms at CAF, though, the exhibitors were happy to turn the sound up or down, that was appreciated by me.

I had been reading about Daedalus Audio speakers, I expected? hoped? to really like them.  The speakers themselves are beautiful, built from solid wood, and the compact Pan speakers would fit nicely into a lot of rooms and seem reasonably priced if you regard them as handcrafted solid wood furniture that makes music.  It is hard to judge fairly the sound at a show though, and while I might like them more in a different environment, I was disappointed at the show.  I first went to a room with a largish pair of floorstanding speakers from Daedalus, and a gentleman in the audience supplied a CD of a female jazz singer, the host played it, the gentleman was thrilled, and I thought it sounded bad.  The playback volume was way above the natural volume of the human voice, and the clarity/naturalness of the voice was not as superior as I would expect from a $10K plus pair of speakers powered by expensive equipment.  Frankly, my relatively modest home system with my old Spendor SP2/3 speakers sounds more natural to my ears.

I did hear the Daedalus Pan loudspeakers in another room demoed by Scott Dalzell, proprietor of Viva HiFi. He was super nice and I would have liked more time in his room, but something just wasn’t right about the sound to get me excited – maybe the music selections, maybe the room acoustics, maybe sitting too close?  I heard some percussion sounds that were especially clear, so I wouldn’t rule out my liking the Pan speakers more under other different circumstances.  Scott was using a ModWright modified Oppo player as a DAC and a ModWright integrated amp, hard to isolate what I was hearing, but it piqued my interest especially to hear the ModWright modified Oppo more.

I went to a room featuring GT Audio Works GTA 1, a “ribbon planar hybrid loudspeaker” for $2,700.  That room also featured some interesting sub-woofers that are meant to be installed in-wall.  I had a brief listen, but I thought the sound was clear and natural.  I haven’t read a lot about these speakers, but I believe they are kind of like electrostatic speakers (Martin Logan, Quads).  Something different anyway, and based on a quick listen, very pleasant.

I heard a pair of Salk floorstanding loudspeakers powered by a Van Alstine tube amplifier.  The Salks were playing a recording of a tenor saxophone, I didn’t think the lower midrange sounded natural, maybe it was the recording, dunno for sure, but trying to guess the amplifier versus the speakers I had a good impression of the Van Alstine Ultravalve amplifier.  This is a modestly priced tube amp, spec’d at 35 watts per channel, and it seemed like plenty of power for the not-super-efficient Salk speakers (88 db).  If I were looking for a tube amplifier, I would give the Van Alstine a more serious audition.

On the other hand, some things did impress me, so let me mention.  A huge pair of Tidal Sunray speakers, with an outrageous price of like $150K, were impressive, perhaps the best reproduced sound I have heard: http://www.tidal-audio.de/.  Tidal makes more modest speakers, I would be interested to hear them sometime.

The Fidelis AV room was playing Harbeth 30.1 speakers with battery powered amplifiers from Red Wine Audio, and that system sounded great to me.

I liked the Volti Audio speakers.  Yes, the demo was too loud.  Yes, I had to sit too close to the speakers.  But still, I had the feeling I would really like these speakers (I heard both the Vittora and the Alura briefly) in my great room – I won’t analyze the sound too much, but the music was “alive” and I just sat back and smiled as I listened, and that’s the whole idea, right?  I also liked the look of these speakers as well – gorgeous veneers, curvy cabinets, wow!  The price in the $14K+ range is too high for my serious consideration, but at least they sounded and looked good.

I was impressed with the sound from Woo Audio’s amplifiers, I listened to a couple of their headphone amplifiers with different headphones, and even used their Fireflies amplifier with sexy glass top with my modest Bowers and Wilkins C5 in-ear headphones, that was nice!  Yes I have a certain amount of American chauvinism, and with an Asian sounding name and a bunch of Asian men staffing the room, I thought at first, oh, another made-in China manufacturer.  But no, Woo Audio is an American company, with the amplifiers made in Queens NY, and I thought that was really cool.  If I were looking for a headphone amplifier, I would give Woo Audio serious consideration, the staff was very friendly, the amplifiers seemed reasonably priced, and the sound was great!

In summary, I came away impressed with Tidal Speakers, Volti Audio speakers, Harbeth speakers, and Woo Audio headphone amplifiers, and would like to hear more from Red Wine Audio, Van Alstine and ModWright electronics.

Thanks for reading!

David and Goliath: A Review of the Spendor S3/5 and the Seas Curv Loudspeakers

The BBC LS 3/5A is one of the most famous loudspeaker designs, and for many years Spendor was one of the licensees.  In the late 1990s, the parts (woofer) were no longer available and commercial production of the LS 3/5A ceased, and Spendor introduced their model S3/5 as a replacement.  I have a pair of Spendor S3/5 loudspeakers in my bedroom.  They are a relatively small, sealed loudspeaker (HWD = 305 mm X 165 mm X 180 mm, or about 12″ X 6.5″ X 7.1″) with a 5″ Spendor-made polypropylene cone woofer and a 3/4″ soft dome, I believe made by Vifa.  A very positive review of the Spendor S3/5 is: http://www.enjoythemusic.com/magazine/equipment/0601/spendor35.htm, and here’s the key point: “ The Spendor S3/5 is simply in the top ranks of what I have ever heard and (most probably) the best small speaker manufactured today.”  Now that review was written in 2001, and since then Spendor has come out with the S3/5 SE (special edition), followed by the R1 (revision 1) version, and now the R2.  Anyway, mine are the original version, about 14 years old I think.

I recently finished building the Seas Curv loudspeaker, designed by Troels Gravesen, see http://www.troelsgravesen.dk/SEAS-CURV.htm.  Troels’ design calls for a cabinet of 8.5 litre volume with dimensions of (HWD) 305 mm X 190 mm X 260 mm, pretty close in height and width to the Spendor S3/5, about 25 mm/1 inch wider and a bit deeper.

Here is my Seas Curv side by side with the Spendor S3/5:

seas_curv_spendor_s35The real difference is in the depth, you can see my “maxi”  Seas Curv is a lot deeper:

seas_curv_spendor_s35_sideHad I built the Seas Curv following Troels’ design, the cabinets would have been similarly sized.  The Seas Curv’s woofer is bigger than the Spendor, and I made the cabinet a plus-size version, about 50 mm / 2″ higher and quite a bit deeper to give an internal volume of about 12 litres.  Another difference between the two speakers is the port (hole) in the Seas Curv; the Spendor S3/5 is a sealed cabinet.

The Spendor S3/5 works well in my bedroom where it is positioned close to a rear wall.  Although the Spendor does not produce deep bass, it is a very satisfying speaker to listen to for most music and even movies – it has a rich, full-bodied sound.

To compare the Curv and the Spendor S3/5, I brought both to my “great room” where they were positioned on top of a low cabinet well in the middle of the large room.  I used one of each speaker, and used my iPad to airplay lossless files in mono, and the balance control on the iPad allowed me to switch the sound between the two.  I used my Rotel PreAmp/Processor with my old Luxman receiver acting as power amplifier.  If you want to know about my speaker cables and interconnects, well, I’m not the reviewer for you!

In my opinion, the Spendor is not at its best in a large room away from walls – it is a small speaker and better suited for a bedroom and a bit of bass reinforcement from a rear wall.  Also, to my ears, smaller speakers do not sound as open or natural as larger speakers – I prefer (in the big room) my Spendor SP2/3 to the Spendor S3/5s.

It was an interesting comparison, but it became clear that the Seas Curv and the Spendor are quite different sounding speakers.  An immediate difference – the Spendor S3/5 is less sensitive, for a given volume setting it doesn’t sound as loud as the Curv.  The Curv sounds like the bigger speaker – it has more bass for sure, that is partly because I built a version with a larger cabinet.  The Spendor though has a smoother sound, but in the large great room I found it a bit boring – upper midrange notes from an alto saxophone or violin didn’t have much bite with the Spendor, the sound was distant.  The Seas Curv was a much livelier and more detailed / “exciting” sound.  I don’t mean the bass was boomy or the treble was bright. But in the mid-range, to my ears, the Curv brought out more of the real texture of the notes, the sound was more detailed and less smoothed over than the Spendor.

I don’t have measuring equipment, so I can only describe what I heard.  Both speakers did a good job on vocals and sounded natural/neutral.  When listening to most instruments, the Seas Curv had a more forward midrange, more of a “close up” perspective, and with more detail.  The Spendor was smooth, and more like listening from further away.

Which is the better speaker?  I judge the two to be in the same league so its more about preference.  The Spendor is highly regarded, and I found the Seas Curv very satisfying and in some ways superior.  Hard for me to know your preference, for me, I’ll keep the Spendors in my bedroom where its smooth sound and limited bass works well when placed close to a rear wall, and I’ll be using the Seas Curv in a more open room where the bigger/livelier/more close up sound is a better match.

Thanks for reading!

SOPWAMTOS and CNO Review Continued

In the previous post, I wrote that Troels’ CNO-T25 compares favorably to my Spendor SP2/3, but I didn’t give a whole lot of description of the sound.  I’ll give some more impressions here, but first some caveats.  I’m not trying to do a professional style review where I try the speakers with different amps and cables and different room placements and cite the recordings I listen to and so on.  So this is just what I hear with my system in my room, your mileage, as they say, may vary.

I truly admire the Spendor company in this day when many companies have changed owners and are a familiar brand name but with little connection to the original company.  Spendor also has had some ownership changes, however many of Spendor’s employees have been there for a long time, and the current owner knew the founder Spencer Hughes (Spendor = Spencer and his wife Dorothy).  Current Spendor management, in my view, has shown respect for the Classic line by making limited refinements.  So Spendor is a rather different from many companies whose name may imply some great European or other heritage but in fact they are now owned by a big conglomerate and their products are manufactured say in China.  Spendor is a true manufacturer in that they build their own cabinets, they build their own woofers, they assemble their speakers, including the crossovers, all in the factory in England (the tweeters are made by Seas, same company that makes drivers for a lot of great speakers, including the CNO).  Spendor could be a member of SOPWAMTOS, founded by Bruce Gordon the bicycle builder – that’s the Society Of People Who Actually Make Their Own Sh*t, as opposed to companies that outsource production and just stick their brand label on the finished product, see http://www.bicycletimesmag.com/content/whats-sopwamtos-and-why-should-i-care.

And this is kind of random, but speaking of sticking your brand label on another company’s product, have you read about the Aston Martin Cygnet? With a new Bond movie out, Aston Martin is getting some more publicity, but I don’t think James Bond would chose the Cygnet as his getaway car.  Yeah they (Aston Martin) paint it and make the interior with fancy leather and trimmings, but it’s still a Toyota Scion iQ: http://www.astonmartin.com/cars/cygnet.

Back to audio, I hesitate to go overboard with comparisons to my pair of Spendors for several reasons.  First of all, my speakers are not the same as a current model that blog readers could go hear.  Spendor does have a model SP2/3 (called R2, the second revision) in its current lineup, and it looks the same and has the same (or nearly the same) dimensions as the older model, it is actually a different speaker – slightly different cone material, different woofer, different tweeter, and so on, although designed by some of the same people (Terry Miles) and with some similar design goals; you can read about it here: http://www.spendoraudio.com/HTML/SP23R2_main.html.

Anyway, I fed a mono signal to the CNO and to the Spendors, and switched back and forth, and here are the impressions.  They don’t sound the same, but the difference is somewhat subtle – they are both neutral enough that nothing jumps out at you when you switch.  The SP2/3s are definitely warmer, they have a little more closed in sound, they are smooth and a little more laid back in the upper midrange.  The CNO’s are both leaner in the lower midrange and have more bass – they have a clearer, more detailed sound.  Does that sound contradictory – leaner but more bass?  That’s how I hear it.  High frequencies to me are not noticeably different – it’s not like one speaker is “brighter.”

I am speculating here, but the Spendor has a relatively wide baffle, and the CNO has a narrow front baffle, and I think that the wider baffle may contribute a bit to the more diffuse and warm sound of the Spendors.  As I wrote before, the CNO has a more spatious sound, I imagine a pair of them would create a different and perhaps more precise stereo image than the Spendors.

I have a secondary audio system for watching movies/television with a pair of Bowers and Wilkins 601s (the original ones) fed by an older NAD receiver and an Adcom DAC, pretty good, but not real high end stuff.  As a test, I created a mismatched stereo pair with the left speaker being the CNO and the right speaker the B&W 601.  Wow.  The CNO is a much better speaker.  The B&W has an attractive tonality, and movies sound good.  But listening to music with the 601s didn’t excite me, but just adding one CNO made a huge difference – the music was much clearer, more dynamic and exciting.

A few more brief comparisons.  I had a listen to Bowers and Wilkins PM1, and also their 805 Diamond speakers.  Of course, different amp, different room, so it’s not apples to apples, but here are my impressions.  The PM1 at first impressed me, but then I listened to a male pop singer (Michael Buble) and started hearing an emphasis on sibilants and a certain nasality, I felt disappointed.  The 805 Diamonds were very clear – my son listened with me and felt their clarity was better than the CNO, but I found the sound sterile and uninvolving.  Take that with a grain of salt.  What I think is so great about the CNO is the balance between clarity and making music enjoyable to listen to.  Although I listen mostly to jazz and smaller chamber or solo classical music, my teenage sons like their pop and compressed mp3s, and they sound good on the CNO.

One more thought about the CNO.  Although it is presented on Troel’s site as a floorstanding speaker, I had good results making it as a monitor style speaker.  Here is a particularly interesting monitor mplementation using vertically stacked slices:  http://www.troelsgravesen.dk/CNO_Christoffer.htm, and you can imagine that if the port was in the rear the speaker could be fairly compact.  Because of the narrow front baffle, and depending on how tall you make the cabinet (if the port is in the rear, it could probably be a fairly compact 14″ or so in height), it doesn’t take up a whole lot more space than many so called “mini-monitors,” but it’s a much more full bodied sounding speaker than the ones I’ve heard with smaller 5″ or 6″ woofers.  So it’s a versatile design and I think competitive with loudspeakers that sell for quite a bit more (these days, the Spendor SP2/3s cost about $4,300) than the cost of DIY CNOs.

So that’s a wrap for comparisons.

Speaker Review: Comparing Troels Gravesen’s CNO and Spendor SP2/3 Loudspeakers

This is one of my most popular posts, so I want to make sure to point out that this is the first of two posts comparing the CNO and Spendor SP2/3, the second post is: https://onetwothreeaudio.wordpress.com/2012/11/14/sopwamtos-and-cno-review-continued//

Originally I titled this “Zen and the Sound of One Speaker Pulsing” as a takeoff on the famous Zen question, “What is the sound of one hand clapping?” as I only have a single CNO speaker.  I built the CNO-T25 loudspeaker, designed by Troels Gravesen and using Seas Excel drivers (see http://www.troelsgravesen.dk/CNO.htm and CNO-T25.htm), as a center channel for music and matched up with a pair of Spendor SP2/3 loudspeakers.  The Spendor SP2/3 speakers are semi-famous, they are a simpler version in a lineage (the BC1, then the Spendor SP1, etc.) based on BBC designed loudspeakers for broadcast monitoring.  One online review of the Spendor SP2/3 is http://www.enjoythemusic.com/magazine/equipment/0601/spendorsp23e.htm; a few quotes, “It’s that damn good.  Get the picture?” and “one of the most musical sounding speakers that I’ve ever had the chance to hear. They surprised me by their levels of transparency and detail…”

My Spendors are 18 years old, are they past their prime?  Hard for me to know, but they sound good to me, perhaps the bass is less than when they were newer, perhaps some of the clarity has declined over time.  The new Spendor SP2/3s look the same but are completely different speakers (new woofer, new crossover, new tweeter, new cabinet, etc.), and I haven’t heard them to compare.

At any rate, here are some thoughts about the sound of the CNO-T25.  The CNO-T25 compares favorably to the Spendors, and I consider that high praise. While the CNO-T25 does not sound exactly like the Spendors, the combination works well together for music, especially since for many recordings the position of voices/instruments is fixed for a recording (I suppose a live recording of say a musical or opera might be an exception), so slight differences between the center and left/right speaker are less critical.   In my opinion, the CNO, with a 24 litre cabinet, has better bass, more clarity, and seems more dynamic.  Spendor loudspeakers are famous for their magical, seductive midrange quality.  I would say that for pure tonality, the Spendor SP2/3s are hard to beat. But the clarity of the CNO was quite noticeable to me, the aural equivalent of suddenly looking out a freshly cleaned window and realizing how dirty the window actually had been.

Since I only built one CNO speaker, I don’t really know what a stereo pair would sound like, but if it’s not a complete oxymoron to state, it seems that the CNO has a spatious sound, even in mono. The sound doesn’t change much as I stand up or sit down, or as I move around the room, an important quality for me. To contrast, I briefly auditioned some Dynaudio speakers and they sounded great when I was in the sweet spot sitting down, but if I got up and walked around the room, the sound changed a lot.  So not all speakers have the property of an “even power response” – sounding about the same in different listening positions.

While the CNO-T25 isn’t meant for killer volumes, it easily fills my large listening room at what I would call reasonable listening levels.  Perhaps because of the clarity, it is tempting to play it louder than the Spendors, and while the CNO sounds fine at low volume levels, it comes alive with a bit more volume than the Spendors.  And, something very important to me, both the CNO-T25 and the Spendors are enjoyable with less than ideal recordings.  I remember when I was auditioning the Spendors, the dealer also had a pair of Spendor SP7/1 speakers, and it made most of my recordings sound bad, so I said no thank you.

Could you tell Color from Black and White?

Before I wrap up the posts about the science experiment listening to stereo and mono versions of the same audio clip, let’s discuss an analogous science experiment with vision.  And I recognize that the most obvious visual analogy would be 3D versus non-3D, but for the sake of argument suppose we conducted an experiment to see if people with normal vision (no known diseases or color deficiencies) could tell the difference between a color and a black and white version of the same video clip.  So, here’s the protocol: a subject is told that they will watch the same video clip three times, and that two of the times will be the same, and one time will be different. And in fact, in randomized fashion, two of the three playings are identical, and one version is color (say the original), and one version is black and white which is created by converting the original color video.  The subject is not told what the difference between playings is, the subject watches the three playings of the video clip, is asked to identify the video clip that is different, and is asked to identify which playing he/she preferred.

Now, what would you expect?  I would expect that the difference between the color clip and the black and white clip would be so obvious that the subject would definitely identify correctly the video clip that is different.  And, while I suppose there can be artistic reasons sometimes to prefer black and white (Woodie Allen, for example, sometimes shoots portions of his movies in black and white), for most video clips that are originally filmed in color, I would expect the subject would prefer the color version.  As I revealed in the previous post, listeners were only correctly aware of a difference in stereo versus mono playback about 50% of the time.  Yet we would expect viewers to be correctly aware of a difference in color versus black and white about 100% of the time.  To me this means that for most listeners, the “stereophonic” aspect of music playback is relatively unimportant especially compared with the importance of color to vision.

Now a different version of the audio experiment would be to tell the subject the purpose of the experiment and to train them to hear the differences.  Similarly here, a different version of this visual experiment would be to tell the subject, “we are investigating whether you can tell the difference between color and black and white.”  However, I don’t think that would change the results for the color/b&w experiment.  It might change the results of the audio experiment though.