Chapter I: Another Round of Room Measurements...Recently, I acquired some more LP's, got a few more IKEA Kallax storage units for said LP's and put up some art as well. Here are front and rear shots of the sound room the other day...
With the physical changes and reviewing my post from last year regarding the use of (((acourate))) along with suggestions made by Dr. Uli Brueggemann and Mitch Barnett (aka Mitchco), I decided that it was time to re-do the room measurements and see if I can incorporate the important suggestions - 48kHz sampling rate for the measurements, sweep range of 10-24kHz, and incorporation of the subsonic filtering at 15Hz. If you're wondering, the dimensions of the room are ~20' x 15' x 8' with a slight frontal tapering as shown; not a huge room by any means and not ideal dimensions but at least it's not squarish/cubish (here's a study on room dimensions and acoustics). It's in the basement of my house, built as a family media room with extra thick walls to reduce sound leakage when the kids are asleep at night (I pretty well can run the sub at reference levels with kids asleep upstairs at night so long as I close the door to the basement). The main speakers - Paradigm Signature S8v3's - are 7.5' apart up front, and the sweet spot is approximately 9' from the speakers arranged like an isosceles triangle. I make sure there is decent amount of space between the couch and the rear LP storage (>3'). [As you can see, I have the ~15-year old rear full-range Paradigm Studio 80v3's back there.]
Before getting to any measurements, remember we're playing the "long game" here :-) as in we want to protect hearing for a lifetime. Test tones are not euphonic and you'll likely be going through multiple trials with tones playing at reference levels of ~80dB. My set of ear protectors:
|Customized ear plugs... Tools of the audiophile "trade" :-).|
I agree with Mitch when he suggests clearing up the room and removing sonic obstructions (to make it more reflection-free) to get a better room measurement. Even though putting the couch back and having the coffee table might be necessities in the room when I'm listening, I suspect the brain has some ability to anticipate some of the sonic changes. Plus if I want "the best" sound from my room, I would be removing the coffee table anyways, so might as well measure the room acoustics optimally. Here's the measurement setup with furniture out of the way as best I could as a one-man job, speakers angled slightly toed-in with the approximate equilateral triangle shape and the measurement microphone at the apex over where I'd sit for the "sweet spot" at ear level. Notice the Paradigm-supplied USB calibrated microphone in place:
|Although I know some people measure with the microphone positioned vertically, I actually found the direct horizontal "on-axis" orientation produced more consistent results for me both with the Paradigm and Behringer ECM8000 mic used later on.|
|Paradigm Perfect Bass Kit setting for the subwoofer.|
After this, I now do the usual subwoofer integration step of finding good settings for amplitude, crossover, and phase of the sub. This is also when I typically will move the sub around and maybe try some placement changes to the listening position keeping in mind esthetics and practicality. I will refer you to this excellent write-up by Avanti1960 on the Steve Hoffman Music Forums using pink noise to find reasonable settings. I used the freely available WaveSpectra software to get the job done using my Behringer ECM8000 mic with the E-MU 0404USB interface as ADC. (I bought the ECM8000 with calibration file years ago, these days I'd probably just get the inexpensive Dayton EMM-6 with downloadable calibration file using the serial number off their website.)
The main difference of course is the added low end down to 20Hz here with the sub and tweaking allowed me to fill in the dip from 40-50Hz a little better while fine tuning the phase knob. Again, we see that unfortunate 60Hz null in the FFT which I wasn't able to flatten out fully with the current sub position and seating spot.
Okay, it is now time to "get it going on" with AudioVero (((acourate)))! Here's the room with the calibrated Behringer ECM8000 microphone in place before starting my room measurements:
|Behringer mic upright... As I mentioned above, I actually found the on-axis positioning pointing straight ahead provided more consistent results. I did make measurements with both orientations.|
|48kHz sampling rate, 10-24kHz range, peak recording level -7dB, IACC10 ~74% (pretty good for home environment).|
|Target curve creation - flat to 1kHz then -6.4dB to 24kHz which equates to about -6dB at 20kHz.|
|Filter creation. Note subsonic filtering below 15Hz. A little trial and error was used to set the "Excessphase window" parameters.|
|Test convolution. Some improvement in IACC.|
|Uncorrected frequency response.|
|Corrected frequency response. Note that the Y-axis scale is the same 25dB range as the one above! And I'm not smoothing over the peaks and troughs too much either.|
But what's more remarkable with good DSP room correction are the improvements in the time domain:
|Speaker step response over 5ms: Blue/Brown = Uncorrected, Red/Green = Corrected with filter. Notice the 3 drive units are now in lock-step to create that corrected plot. Both right and left channels are well aligned in time and amplitude. Remember that such esteemed companies as Vandersteen and Quad place an emphasis on this time-domain alignment (see recent Vandersteen Model Seven Mk II measurements).|
|Speaker impulse response uncorrected. (Nice time alignment of speakers even before the correction.)|
|Speaker impulse response corrected - precise bilateral minimum phase response now!|
|All with minimal phase deviation throughout the audible frequency.|
|I have spoken of room reverb time in the past. Acourate has a very nice RT calculator screen to analyze this... Top right you see settings for tolerance levels using various standards like the DIN 18041 for live musical performances, and EBU 3276 for formal listening rooms like studios. As you can see from the tolerance levels (black), my room is a bit reverberant for studio purposes but would easily satisfy DIN 18041.|
As I described before, the music with JRiver convolution DSP using the Acourate filter sounds excellent. Clearly improved frequency response resulting in natural sounding tonality. And with the improved time domain speaker step response and precise impulse response, soundstage and imaging are superb... Lately I've been enjoying Johnny Frigo's well recorded albums Debut of a Legend (1994) and Live from Studio A in New York City (with Bucky and John Pizzarelli, 1989 Chesky - SACD version sounds fantastic) - great violin work and fantastic sound staging highlighted with the DSP activated. The clocks and chimes at the start of the audiophile favourite "Time" (Dark Side Of The Moon) should sound "surround" and simply palpable. Another clear effect to listen for is how the speakers just "disappear"; for example a modern pop recording like Ed Sheeran's "Photograph" from X (2014) has his vocals literally front-and-center sounding like he's sitting with his guitar right between the speakers (although the added reverb is obvious and points to the studio work). It's just one of those things you're going to have to listen for yourself; preferably having the option to turn the effect off and on quickly to experience the difference time and frequency domain corrections make. This is what more accurate sounds like, when the drivers of a speaker system are temporally aligned and consideration given for room effects.
Remember though that there is a price to pay for this level of accuracy. You need computing power for real-time processing (not a big deal these days), and there is some timing latency to be aware of - gapless playback is a problem currently when streaming through DLNA/UPnP from JRiver 21 like what I have been doing with the ODROID-C2/Volumio (direct JRiver playback seems to be fine as the program can compensate, JRiver is aware of this and hopefully can come out with a solution soon). Also, remember that the higher the quality of the speakers / hi-fi system / room, the better the ability to fix frequency and time-domain issues... You obviously cannot expect a DSP to make a boombox sound like a true hi-fi system! It could try getting a little closer though :-).
Before ending off this illustration of my activities, here's a "flatter" target frequency response curve for listening when I'm in the mood (slight roll off from 10kHz down to -3dB by 20kHz) and the resultant speaker frequency response overlaid:
Basically within seconds, just by changing the DSP setting in JRiver, I can change the sound of the speakers; like getting new boxes in the room with basically just as good time domain qualities but with different tonality depending on what I choose to listen to that day... Isn't technological progress wonderful?!
BTW, I really like well recorded, "natural" sounding albums reproduced with this "flat" setting. For example the Hugh Masekela album Hope (1994, recorded live at Blues Alley in Washington DC, look for the Analogue Productions SACD) has an enveloping soundstage around the listener, with a nice tight bass that's just great with a full range speaker system. And for lovers of classical Chinese music with the erhu, Yu Hong Mei's (于红梅) Erhu Chant (闲居吟) from Channel Classics sounds fantastic; tremendously expressive and emotional. Again if you can find the SACD, it's a great "true" high-resolution recording with a multi-channel layer as well. Of course, SACD/DSD material needs to be converted to PCM in order for complex DSP processing. I'm very happy with the result of DSD to PCM 24/88 conversions (tests last year here, and here).
Chapter II: Meditations on "Accuracy"Above, I spoke about creating a "more accurate" listening experience. Is the concept of "accuracy" meaningless (a mirage? a delusion?)? Is it ever possible to describe such a state?
No delusion... And of course it is possible! Because of one simple fact... Music production studios aspire to "achieve optimum acoustic properties (acoustic isolation or diffusion or absorption of reflected sound that could otherwise interfere with the sound heard by the listener)" (as per Wiki). Whether it's a top notch commercial studio like Abbey Road, or Columbia Studio, or smaller audiophile labels like 2L, or AIX, or the home recording guy who still wants to up his game in the home studio; there is a certain standard of acoustic control and music production that needs to be understood and verified in making sure that the best recording can be made to the intent of the artist. I'm sure audiophiles appreciate that doing this costs money and professionals who do this work need specialized training and must appreciate the science behind the whole endeavor. Just look at the Studio Creations website for some of the factors from architectural design to statutory regulations to air conditioning that must be accounted for to create a desired, "accurate" recording studio. I also expect that an audiophile would accept that measurement devices would be utilized professionally in setting up the optimal acoustic space and in choosing and tuning the best speakers, microphones, control console, ADC/DAC, etc. for the job! It would be preposterous for studios to be only subjectively "tuned by ear".
When I speak of "accuracy", I am referring to an appreciation of the above. I am not talking about some kind of idealistic reproduction of "live music" though it would of course be nice if recordings were made to sound like this when reproduced accurately. Or some vague subjective notion of "sounding good" and "making the listener happy" though of course again, I hope artists and sound engineers are successful in creating such a product. As "music lovers", we all wish for a powerful emotional response as a higher-level goal of the art form in general. Appreciating subjectively "good sound" and feeling "happy" with the music isn't difficult and doesn't require fancy expensive gear; I'm sure we've all been doing it since childhood through AM radios, audio consoles, cheap boomboxes, poor quality earbuds, scratchy damaged vinyl... The "music lover hobby" is massive, inclusive, consists of all races and creeds, men and women. I will pick up the occasional Rolling Stone, browse the newest MOJO or read Pitchfork still for the "music lover hobby" which includes broad appreciation of the artists and exploration of the artistry of the lyrics, music and rhythm.
But when I write this blog or make the rounds to see what's new in the audiophile press, the goal of accurate music reproduction through the hardware is inextricably linked with the "hardware audiophile hobby" in my mind. Any one of us can take out the credit card and pay big money to buy expensive DACs and speakers if the desire and credit is available. But to me that's neither exciting nor educational in the service of a hobby that hopefully has an enduring trajectory. As a hobby, my perspective and hope is that "hardware audiophilia" satisfies an internal curiosity not only of what to buy or what to do, but also why there is value in the technology or equipment. In doing so, hopefully this promotes growth in understanding what makes a good sound system, anticipates the path of good sound reproduction as technology evolves, and with understanding and wisdom, reaching out to others to provide useful advice having understood the principles and experienced what makes a difference. In sum, I believe there are two separate hobbies that become intertwined for any one of us. You broadly see subgroups out there - those who mainly love the music but care less about having the best gear, those who mainly love the hardware but spend relatively little on the music collection, and of course those who try for a balance between the music collection plus the best hardware and room set-up with the hope for well mastered albums and accurate gear that allows for extraction of as much detail as possible for the listener. I would of course like to see myself in that last group.
Consider MQA as a real-life contemporary example of how "accuracy" is part of the evolution of the audiophile world. Whether one is skeptical about the claims of MQA, realize that a core claim by Meridian is that it incorporates a "de-blurring" algorithm to improve time domain accuracy of the recording from the studio to the home DAC (and "authenticated" as such). In my opinion, if the audiophile world embraces MQA as an exciting new technology that makes audio "better", then it must embrace the concept of "accuracy" as a desirable goal! No matter whether MQA achieves its "de-blur" effect as intended, the excitement is over the potential for a higher fidelity, more "accurate" rendering of the musical signal (with the touted ability to compressed file size for streaming as well). In my opinion, DSP filters like Acourate (and other similar software like MathAudio, Dirac, DRC/Designer, Audiolens...) likely will have significantly more impact because it actually will analyze and customize the sound with your speakers and in your room. Again, if we actually accept MQA's claims of time-domain accuracy, the promise of MQA would only truly be realized on a system with time-domain correction on the analogue side - the part where the sound actually hits the ears at the listening sweet spot! What's the point of the MQA technology aligning microscopic digital details like pre-ringing and minimizing "temporal blur" when multiple millisecond time-domain anomalies are not corrected due to speaker and room limitations? This reminds us that maintenance of accuracy through the whole playback chain is an essential component of what the "hardware audiophile hobby" strives for. It is also what truly beneficial new technology seeks to improve on.
[Needless to say, I noted that the "music lover hobby" attracts broadly including men and women in large numbers. Notice the "hardware audiophile hobby" is primarily the domain of men. This is an important distinction to recognize and I think accept; probably due to inherent differences between the sexes which is unlikely to change.]
If we go back to the foundations of the hardware side of our hobby (for example, reading "The History of High End Audio"), it's clear that from the beginning, the goal was "high fidelity". Whether this meant a low-distortion McIntosh amplifier that drove difficult speaker loads, noise suppression of clicks, pops, rumble of early turntables and vinyl, achieving low noise in a preamplifier, or speakers capable of full frequency response. There were legions of music lovers throughout time but those that really cared about high quality artificial reproduction of recorded music began with engineers and hobbyists who wanted fidelity. They were the pioneers...
Chapter III: "Accuracy" and the Media
I take issue with Steve Guttenberg's recent Stereophile editorial "The Fallacy of Accuracy". It seems like he provocatively titled the article to raise a few eyebrows doesn't it? And then there's his pithy conclusion of:
"My take: Park your faith in accuracy and measurements on the back burner, and go for speakers that make a big chunk of your collection of recordings - the good, the bad, and the ugly sounding - shine."
"The lab facility is very much Paul's home away from home. He has spent far longer in the chamber and lab than any other speaker designer, and in the 25-year process since he began going to the NRC has gained enormous sophistication about acoustics and the sound of speakers."
Ultimately, although most of us are no longer engineers trying out new designs or putting together DIY kits, we can still learn to understand for ourselves and find satisfaction in so doing. Not just what we like on the software consumption side (the "music lover hobby"), but as educated consumers with insight into worthwhile hardware (the "hardware audiophile hobby"). Sure, we can keep an open mind, but let's face it, in the audiophile world of 2016, it's obvious that not everything is worthwhile. As the old saying goes, keep an open mind, "but not so open that your brains fall out" (Walter Kotschnig, 1940).
Chapter IV: ConclusionAs I close off today, I want to suggest something which I feel strongly about having explored and thought about audiophilia over the decades. The concept of "accuracy" isn't a peripheral consideration. It is in fact one of the pillars of this hobby from my perspective. Without some internal definition of what "accuracy" means, the "hardware audiophile hobby" is without a compass unifying hobbyists. It becomes a consumeristic affair where the goal becomes that of moving product whether there are technological merits or not (eg. expensive cables, unproven USB doohickeys...). There does not appear to be a willingness or ability for many mainstream audiophile pundits to weed out bizarre claims and call out functionally anomalous measurements for what they are. So often, the subjective-only reviewer will wax poetic about some piece of equipment, yet the performance suggested by objective analysis are clearly such that no reputable studio or acoustician would likely endorse such products. It's in fact rather bizarre the dissociation between the ideas and values held by professional music engineers and the audiophile world around sound quality and what is "good" equipment. Even more embarrassing are the times when writers accept claims for products that obviously cannot work as advertised simply based on common-sense and basic education (just consider $$$ cables!).
Finally, I hope that in these blog pages and in articles like this, the audiophile reader finds it empowering to consider that we are not simply consumers. Knowledge, curiosity, and ultimately experience allows us to grow beyond the ubiquitous hype and hyperbole of manufacturers, or what some magazine writer, forum poster, or blogs might claim. Of course I do not exclude myself from this potential as well; to err and have subjective biases is human... But what is important is to have tried to verify impressions and understood truths where they may be found. Exploring ways of optimizing what you have whether it's $200 worth of gear or $200+K is a great start.
Further Reading: Over the last couple of months, I have had the great pleasure of reviewing and providing suggestions to Mitch Barnett (aka Mitchco) towards an eBook he has been writing about the use of (((Acourate))). As you probably know, Mitch's blog posts on Computer Audiophile including the ones on the use of Acourate have raised the "standard" when it comes to introducing many of us to DSP-based speaker/room optimization (and was the inspiration for my own post last year). In this book, Mitch goes into much greater detail drawing from his experiences in professional sound recording, discusses technical aspects of sound quality (and "accuracy" of course!), explores advanced techniques in multiway crossover digital filter design (including driver linearization and time alignment) as well as measurement techniques like beamforming to achieve quasi-anechoic results. Topics beyond the already excellent free articles. He also has a detailed chapter on acoustic measurements and ways to validate the filter performance. All written in a practical and no-nonsense step-by-step presentation aimed at getting results. I don't think it's hyperbole to say that this is the essential reference/manual for an extremely powerful piece of software which can be overwhelming for the uninitiated. At the cost of less than 3 caffè lattes at Starbucks ($9.99), I think this is a very reasonable price for the amount of work involved. You can check out his eBook on Amazon.