Do You Hear What I Hear?

Do You Hear What I Hear?

(mking the Seas Curv loudspeaker)

WordPress gives me a bit of information: what blog pages are viewed, what search engine terms were used to get to the blog, and what countries people are from.

Not a big surprise, most visitors are searching for something related to Spendor or Troels Gravesen, and the posts that get the most views are my comparisons of Spendor SP2/3 to the CNO, and the Spendor S3/5 to the Seas Curv.

I thought it would be interesting to see if I could let you, the reader, hear what I hear. That is, I wondered if I could record my speakers and see if you can hear the differences I hear. The problem is that I don’t have a recording studio, and the only way I know to host a soundfile is to make a video slideshow with music on youtube.

So, here is my first experiment – a few minutes of music reproduced by the Seas Curv loudspeaker, and recorded with a Sure SM-57 microphone. I picked music that I thought would demonstrate a few things: naturalness of voice (both soprano range and lower male voices), some instrumental including brass, saxophone, piano, and drums. I used an E-MU 0204 to take the signal from the microphone, digitize it in 24 bit, and send it to my Apple laptop computer. I edited (cut) the sound samples with GarageBand, and maintained full resolution until the final export.

It is important to realize that the microphone itself has a frequency response curve that is not flat – the low notes are rolled off, and the high notes are accentuated. The middle range though appears to be very flat and accurate.

This is my first attempt, so I will get better at it. I plan to go back and repeat the recordings with the Spendor S3/5 so you can compare what is captured by the microphone and “hear what I hear.”

*** Update 9/11/2013 ***
Although I believe a short sound clip for educational purposes is “fair use”, someone or some system recognized the source of one of my clips and I had to remove for alleged copyright violation. Also, I have been having difficulties with the E-MU 0204, so I have not been able to make further recordings. Hope to try again soon.

Video: Not currently On youtube

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California Audio Show 4 (2013) – A Visit with my Camerman

This past Saturday, I sent my fierce Corgi out to hunt for the California Audio Show:

corgi_hunting

Ah – there it is – the lovely Westin Hotel:

the_westin

This time, I went with my trusty camera man in tow, so I have a few photos to share. My usual gripes about audio shows aside, I had a fun time and would recommend this show to locals.

OK, I just love the look of the Sonus Faber Olympica loudspeakers. This is a new line of speakers that made their debut a few months ago in Munich, and here is the Olympica 1 stand mount speaker, what a beauty!

olympica1_2

olympica1_1

This is just a gorgeous gorgeous speaker, with solid walnut wood for the top and bottom, stitched leather on top, and leather covered baffle and rear, and a swoopy, curvy lyre shape that is a Sonus Faber signature. You can read more about them on the Sonus Faber site: http://www.sonusfaber.com/en-us/products/olympica-i.

I was told the speakers will have a retail price (in the USA) of $6,500, and another $1,200 for the matching aluminum stands. Pretty pricey in my book, but oh, they are lovely. Now value in high end audio is something of an iffy proposition, and given the high quality materials, limited production, and relatively costly Italian craftsmanship, others may perhaps view these as reasonable. For me, I feel confident that, if given the components (drivers, crossovers) of the SF speakers, I could make an externally plain box (but with interior complications and lots of bracing) that would sound quite similar, but it wouldn’t look this good! Seriously, it is hard for me to imagine that a fairly small 2-way loudspeaker with stands could be worth nearly $8K sonically – each speaker has a single 6″ paper (“cellulose”) cone woofer, and a more or less conventional tweeter. In my opinion, and based on my recent experience with DIY loudspeakers, it’s hard for me to justify such stratospheric prices when I can build something like a monitor version of Troels Gravesen’s Seas CNO for under $2K /pair even factoring in high end Excel drivers from Seas, paying a cabinet maker, and using top quality plywood, damping, and crossover components.

How did the Olympica I sound? Not sure, to be honest. They were being demoed with some techno music “noise” – I wonder what Franco Serblin (RIP) would have thought of such a choice of music for his brand. How can one judge the naturalness of speakers playing loud synthesized techno music? The one impression I had was that, on the one hand, the speakers made a lot of sound and bass for their size and relatively small woofers, but it wasn’t my idea of good bass, it was “impressive for a little speaker” bass, if that makes sense. I wish the demo had been better.

What else was disappointing? I had my first listen to the Wilson Audio Duette 2s, and they are, to me, an even worse offender when it comes to value, approaching nearly $20K with their matching stands. How did they sound in the demo room to me? Well they played loud, they did sound “big”, but the bass was boomy, and the sound was not natural. Another disappointment in my view was a pair of A Capella horn speakers with a fancy plasma tweeter. The sound was overly bright/harsh, and I can’t imagine that having a large midrange horn in front of a tweeter doesn’t cause all sorts of diffraction problems.

BTW, if you disagree with my opinions, well, that’s fine. If something does sound good at a show, I take that as a positive sign. If it doesn’t sound good, well, could be the room, could be the demo recording, could be the pairing of the equipment, and so on, I can only give my impressions, and I think it’s useful perhaps to read a different point of view to the professional sites where critical comments are less common.

Ok, so what did sound good at the Show? One of the best sounding rooms was from Music First Audio, they have a “transformer passive preamplifier” and were playing an analog reel-to-reel tape with Audio Note loudspeakers, the volume was reasonable, the recording was excellent, a very good sounding room! And I heard a demo of Vivid Audio Giya speakers – they sorta look like huge Hershey’s kisses, the sound was excellent, clearly a few notches above my home system in terms of dynamics and clarity at higher volumes.

One room that impressed me with good sound for a more down to earth price was a demo of AudioPhysic Classic 20 loudspeakers powered by Nait XS2 integrated amplifier. The AudioPhysic speakers are slender 3 way towers with side-mounted woofers, I don’t recall exact pricing but somewhere between $4-$5k, and the Nait XS2 is around $2,500, downright reasonable compared with some rooms where the price of the components exceeds the cost of many houses in the USA.

I want to mention a few turn-offs. The show was not very friendly for young folks. My teenage son desperately wanted to hear “his” music instead of classical or older pop/rock. What is his music? Nothing too unusual for today’s teenagers – he’s a bit eclectic, but as a random sampling of things he’s played for me, he’ll listen to Jay-Z, Justin Timberlake, Lady Gaga, Rhianna, and so on. In the majority of rooms, nothing remotely like his music was being played. Finally, we arrived at a demo room, the host asked what we wanted to hear, my son, seeing his playlist, said “Coldplay” and then the host  proceeded to play something else – hello – he asked for Coldplay! Folks in the audio industry, if you are reading this, the teenagers don’t have the money to buy now, but if you want them to become interested in audio, make the show more accessible to them!

The best part of the show for him – the big room with all the headphones and headphone amplifiers. We visited our friends at Woo Audio, they again had the lovely fireflies amplifier:

fireflies

And here’s the trusty camerman enjoying the sound of Sennheiser HD800 headphones:

sennheiser

One more cool thing – I saw and heard Mr. Speakers headphones featuring a headcup that was made by a 3-D printer.

I prefer speakers to headphones, but no question, the biggest bang for the buck for good sound are headphones – get something like the Sennheiser HD800 and the Woo Audio fireflies amplifier, pair with your laptop computer, great sound!

Thanks for reading…

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!