Stereophonic Sound with ORTF

slow shutter photo of D.C. metro subway train

Location sound can present a variety of challenging obstacles to capturing hi-fidelity sound. The infrasound that a fast moving train creates can become a problem for directional mics positioned nearby. Using the techniques described in my previous microphone isolation post allowed me to maximize the available headroom in my recording. Below, listen to a stereo recording I made of the Washington D.C. Metro train. You will hear the subway train arriving from a far left tunnel, after it stops the doors open in the center, then the train rumbles as it fades away into the far right tunnel. The distinct panning or movement of sound in this stereo recording was captured using the ORTF stereo mic technique. Try a pair of headphones or stereo speakers for a fully immersed experience.

Higher quality versions of this recording are available, as well as custom sound designs/effects.

Channel Islands E•200S Stereo Amplifier

Channel Islands Audio E-200S Front Panel

The last time I tried out some of Dusty Vawter’s amps I was toting two hefty monoblock amplifiers down the Pacific Coast Hwy. On this journey, my payload was significantly lighter. The E-200S stereo amplifier box fit snugly into the back of my Subaru, and once home, this small unassuming amplifier took center stage powering my 2 way speakers- Green Mountain Audio Eos HX.

Getting it out of the box, was a snap (14.0”W x 2.75”H x 10.0”D). The size and weight of this amplifier made setup and handling a breeze. While the front panel grants access to an on/off button with blue LED surround, the host of usual connections can be found on the amp’s business end. Whether you choose RCA or XLR inputs, the custom differential input stage is used. Then an updated UcD Class D stage drives the output. Speaker binding posts are insulated and accept spades or bananas, and a trigger input is also made available. Power cable plugged in, and we are off.

200 watts per channel @ 8 ohms/ 400 watts per channel @ 4 ohms

For music, I used a Macbook Pro running iTunes/Pure Music 3. The DAC was my Crane Song Avocet, and the Antelope Audio Zodiac Platinum. With everything connected via balanced cables and several hours of warm up (this amp had already been burned-in) I was ready to start listening to some of my favorite tracks.

I cued up some acoustic music by Kings of Convenience. This Norwegian duo offers a great starting point to evaluate the naturalness of the male voice. Listening to “Rule My World” from “Declaration of Dependence” gave me some lovely acoustic guitars with harmonizing male vocals.

View from above, notice the small footprint

The two part acoustic picking of “Declaration of Dependence” maintained all the midrange richness while allowing the male vocals to almost float above the gentle picking style. The clarity of guitars and male voices were presented in an un-hyped and natural way.

Moving onto more complex works, I began listening to Herbie Hancock’s “Steppin’ in It.” This groove laden funk from Mr. Hancock’s “Man-Child” album features rich synth leads, a tight bass lines from Paul Jackson, and a stellar harmonica solo by Stevie Wonder. Allowing all that musical articulation to shine through requires some control over loudspeaker movement. The E200-S gripped My Eos HX and allowed each and every bass note to come through with precision and depth. While everyone in the band holds down the groove, Herbie takes the Rhodes for a stroll… and before you know it Stevie Wonder is syncopating a harmonica unlike I’ve ever heard. With each breath, a new note even funkier than the last is pumped out. All these counter rhythms and complex instruments can be demanding on an audio amplifier, and the CI Audio E-200S never slowed down. In fact, the intricate stereo soundstage was expansive. To top it off, the tonality of instruments (even the squeaky high harmonica) never sounded dull or harsh.

To verify the neutrality, I relied on several orchestral and vocal ensemble recordings I made for NPR, all at the same performance hall. While less capable amplifiers have shown some distortions or break-up, I’m happy to report that the CI Audio amp had none of those shortcomings. Localizing mic placement, hall width/depth, and reverb decay were all amplified without coloration. This provided a sonic portal to the original recorded events, an immersive experience indeed.

Spending time with the E-200S was revealing in so many ways. From black quiet backgrounds to fully erupting orchestral performances, this little beast was in control. Most of all, this CI Audio amplifier proves that green design and audiophile sound need not be mutually exclusive.

Happy Listening

The HiFiQC Method For Stereo Microphone Isolation

ORTF with UMS 20 Stereo Bar mounted to Rycote Lyre suspension

Recording music and sound effects with carefully placed stereo microphones can present some challenges. Since directional microphones are more sensitive to infrasonic noise, special attention should be taken when placing them in various environments. Wind, machines, automobile traffic, and footsteps can all cause rumble or noise to build-up and eventually reach your microphones. The low-frequency nature of these sounds can take up precious headroom in your audio recordings. While wind (blowing on the capsules) can be tamed with various foam enclosures (the W5D is my favorite for Schoeps) don’t forget to isolate mechanical vibrations from reaching your mics too. After trying elastic shockmounts alone, I devised 3-part system to better isolate my ORTF stereo array (also works for MS, XY, and Blumlein) from infrasonic disturbances .

A 3/8 inch mic mount threading adapter allows me to eliminate the 20 mm Schoeps mounting adapter, saving 38 grams of weight

To start, Rycote has a non-elastic suspension made of a super-strong thermoplastic called Hytrel. And unlike elastic, it won’t sag and eventually wear-out (so far, so good). After being impressed with a Rycote Invision suspension for a single Schoeps mic, I decided to see if a solution existed for isolating 2 Schoeps mics arranged on the UMS 20 stereo bar.

After some digging, I came across the Rycote portable recorder suspension and wondered if it might work since the weight of the stereo bar and mics was nearly identical to most portable recorders. As you can see from the picture above, this model easily supports and isolates the Schoeps universal stereo bracket with mics attached.

Carbon Fiber Disc and Sorbothane Hemisphere

Using a microphone suspension is certainly one method to help prevent vibrations from reaching your mics, but what about infrasonic born vibration from foot traffic, cars nearby, or HVAC compressors. These disturbances can travel up your mic stand and into your microphone.

After experiencing issues from foot steps and traffic rumble, I worked on a solution to isolate the microphone tripod from the ground itself. Both Carbon Fiber and Sorbothane are materials known to dissipate mechanical energy. So, I settled on Sorbothane hemispheres attached to an equal diameter carbon fiber disc.  Sorbothane works best when compressed under a range of weight (depending on size and Duro rating of hemisphere). By choosing a durometer rating of 50 in the 1.5″x.75″ Sorbothane hemisphere, 7-14 pounds of weight on each tripod leg could be isolated.  And after adding some 8 lbs sand bags to my tripod, I was able to get the load heavy enough to make the Sorbothane hemishpere’s truly effective.

Sorbothane being compressed by the weight of microphone stand and sandbags

Lastly, but equally important is making sure your microphone cables do not transmit cable-borne noise to the microphone body. Carefully dressing your mic cables around the tripod is essential to preventing vibrations from reaching your mic. With the help of velcro cable wraps, you can neatly run your mic cables, but don’t forget to pay attention to where and how they are laid on the ground. In some cases you may need to isolate the cable on the ground too.

For those looking for an even smaller stereo mic setup with windjammer possibilities…Check out this ORTF setup with Schoeps CCM mics, Rycote Lyre suspension, and even a Rycote connobox to eliminate cable handling noise!

Happy Recording,

-HiFiQC

10 Audiophile Gifts That Will Bring Music To Their Ears!

Head over to Apartment Therapy for a round-up of audiophile gift ideas.

How To Clean Your Vinyl Record Collection Like a Pro

shiny clean vinyl record

Go over to Apartment Therapy Tech to check out this post on cleaning your vinyl LPs. Stylus cleaning, wet and dry brush techniques – all to keep you groovin’ to your favorite albums:  How To Clean Your Vinyl Record Collection Like a Pro 

The New Green Mountain Audio Eos HX

Green Mountain Audio Eos HX
photo by Vahan Baladouni

Associated Equipment:

Source: Macbook Pro running Pure Music with a large variety of recordings and resolutions.

Amplifier: Anthem MCA-2 class A/B

Computer interface: CI Audio Transient II USB to S/PDIF converter and VDC-5 MK II (power supply)

DAC: Crane Song Avocet DAC/Monitor controller (Discrete Class A)

Power: Shunyata Hydra 2 x 2 and power cables (various: copperhead, sidewinder VTX, Hydra VTX…)

Cables: Audio Magic Sorcerer speaker cable, Excalibur II interconnect, DH labs D-75 BNC to RCA, & Wireworld starlight USB

Eos HX

When you think of traditional speakers you often expect a wooden box of some type with drivers arranged inside. Not so with Green Mountain Audio’s Eos HX. In fact, no wooden cabinets here, except for the lovely Cocobolo wood that surrounds the tweeter. By taking a closer look it becomes evident that unique materials were used to build this speaker. The handcrafted Eos HX from Colorado Springs, CO combines artisanal workmanship with engineering refinement.

The Eos HX Tweeter surrounded by Cocobolo wood
photo from Green Mountain Audio

This HiFi meets steam punk design is the brain child of designer Roy Johnson. Mr. Johnson has spent years researching and developing a full range of speakers, and the Eos HX sits at the top of his 2-way designs. Never quite satisfied, the Eos has seen three iterations: the Eos, the Eos HD, and the latest being the HX. 

These speakers are  full of innovation. Starting with the Q-stone cabinet material, these monitors have a unique ability to be shaped in acoustically appropriate ways while also maintaining a low self resonance. The curved shape around mid/woofer allows for the fullest dispersion of sound, and the adjustable tweeter employs wool felt discs to eliminate early cabinet reflections. Without metallic resonances, the lightweight soft dome tweeter from Seas extends beyond 30Khz. The twin ports for the woofer have  been specially designed to more efficiently handle bass pressure. What you end up with is a truly tuneful bass response with an excellent percussive attack.

The heart of the Eos HX is found in its crossover circuit. Through much refinement, Roy Johnson has arrived on a crossover design (1st order) that works at achieving time-coherence  across the audible frequency range. Further sonic enhancements include Marigo internal wiring and Audio Magic nano stream process for the entire crossover circuit (including internal wire and binding posts). All these combined refinements further the speaker’s ability to reproduce nuances in the music.

The Eos HX rear with Vampire Wire binding posts
photo by Vahan Baladouni

Spending some quality time with the Eos HX proved to be very enlightening. While the bass extension rolls off around 50 hz, these 2 way compact speakers (6 inch mid/woofer and fabric dome tweeter) produce an even and smooth marriage between tweeter and woofer. The dual ported Eos HX maintain an accurate and satisfying extension of low-end, especially in smaller listening rooms. Recordings like Count Basie to more modern pop styles of Beach House were reproduced with greater resolution than I had previously heard. Even micro details were more readily heard, but never in an overhyped way. With such a natural sound reproduction of voice and instruments, I found myself hearing much deeper into recordings. The stereo image is quite amazing for a monitor of this size.

I cannot emphasize enough the emotional quality these speakers reproduce. All the attitude and inflection of singers were heard with an obvious transparency.  listening to multiple voices proved to be very revealing, localization and distinctions from singer to singer became more obvious. When I turned my attention to percussion instruments like cymbals, the articulation of attack was easy to hear and subtle differences between strikes were apparent. Cymbals have never sounded so real and fully textured. Whatever the instrument, The Eos HX have an uncanny ability to reproduce it without adding to or smearing the sound. Most importantly, these speakers produced a highly musical and involving listening experience. Without reservation, I highly recommend auditioning the Eos HX.

Pure oxygen free copper directly gold-plated binding posts
Photo from Green Mountain Audio

Further information on Green Mountain Audio can be found here.

Happy Listening!

Devialet D-Premier

Devialet D-Premier

Pleasing modern aesthetics isn’t always associated with audiophile gear. In fact, finding Hi-Fi equipment that blends sonic delight with great design is something to be applauded. French audio firms Focal and Devialet are no slouches in this department. Devialet, in particular, produces an integrated amplifier that incorporates unique and compact audio circuits with a clean industrial design to match.

The D-Premier ($15,995USD) is an integrated amplifier with onboard digital-to-analog conversion for various digital music sources (digital coax, optical, & AES/it also has analog inputs) as well as a hybrid power amplifier section capable of driving a variety of speakers. Devialet seems to favor short signal paths while harnessing the strengths of class A and class D amplifier topologies. It is my understanding that the D-Premier incorporates a class A input section with a digital switching amp for power output. I am certainly oversimplifying this design, but proof is in the listening. Technically speaking, the D-Premier achieves very low distortion (THD+N (harmonic distortion) at full power: 0.001%) while providing 240 watts of power into 8 ohms. This power can be increased (2×400 watts and THD+N lowered to 0.00025%!) by using two separate D-Premier’s in a mono block configuration. That’s lots of power in a relatively small/thin footprint! – eloquent dual mono setup.

I heard this amplifier powering Focal Stella Utopia speakers while playing source material from a Sooloos digital music server. Music was reproduced with precision, clarity and control. When over limited recordings were played (Adele’s 21), all the vocal distortions came through with obvious detail. This amplifier is very accurate, and provides the listener with all the sonic layers while providing precision and control to speaker drivers.

The Stella Utopia incorporate an active Electro-magnetic speaker technology which of course requires power and some serious floor space! I would have really liked to see how the Devialet-D and the Focal speakers sounded with vinyl playback, but with the demo provided I could be easily persuaded to do further listening.

For blending with room decor, the Devialet -D integrated amplifier may be hung on the wall. This allows all wiring to be done through the wall, thus eliminating unsightly audiophile cables. A video demonstrating the chrome finish, and how it reflects the rooms colors can be seen at the Devialet website homepage. Ergonomically, the D-Premier’s wireless remote provides a luxurious dial for adjusting volume level,audio inputs, and even a phase invert button. Right now, it is only available in chrome, black, and white finishes. I am told (by the US distributor) that other colors will eventually become available.

Devialet’s modern industrial design comes complete with Apple style packaging. Firmware upgrades provide improved features such as wireless high-definition audio (up to 96khz).

This integrated amplification system combines powerful fidelity, flexibility, ease of control and graceful design. Getting to the heart of music seems to be a priority with the D-Premier, and I for one welcome this approach.

Computer Hi-Fi

Achieving bit perfect playback with zero interference is the goal, right? I will use this post to explore my findings with computer based stereo systems. Here’s some of the equipment I tested out.

For this test I used an Apple Macbook Pro for my audio playback system. The Macbook Pro supposedly has better RFI (radio frequency interference) rejection than the Mac Mini. PC’s are also possible playback computers, but this article will relay my Macbook pro experiences.

Building a Hi Fidelity computer based audio server/player can often present some challenges. While iTunes organizes music well, it doesn’t play it back with the highest fidelity. Enter the software developer. In recent years we have seen a variety of playback software come onto the audiophile market. This software, such as Pure Music** and Amarra allows iTunes to open and be used as a GUI while pure music handles all the audio processing. Features like RAM memory playback, upsampling, and turning off handshaking allows digital music to be reproduced with less artifacts/jitter.

Computers are notorious for producing noise. Not only do the fans make acoustic noise, but also the graphics card, processors, and other components produce power line noise. This hash is transmitted down USB, Firewire, and other ports that transmit DC power. The sensitive clocks that produce the sample rate in these USB/Firewire DACs are affected by the noise transmitted down the busses DC leg.

The German-made Yellowtec Puc 2* USB audio interface converts USB to AES for the Crane Song Avocet DAC. Providing clean power to the USB powered AES interface is of utmost importance. In order to tackle this issue I first start by separating the digital and analog audio gear. Shunyata hydra 2 units are used for this purpose. The DAC/Monitor controller gets AC power from one hydra 2, while the stereo amp is plugged into the other Hydra 2. If I had the ability, I would place each of the Hydras on their own dedicated AC circuit. Furthermore, I have the computer on a separate circuit with a surge protector.

Other products exist from companies like AQVOX that allow you to lift the DC power from the computer and insert a separate power supply for your USB device.

I will continue to relay my findings as I explore this topic more. Stay tuned…

The Yellowtec sounds best when operating on internal clock, as do many converters. The Puc 2 also benefits from clean power via the previously mentioned methods.

*The Yellowtec Puc2 is asyncronous and can be locked to an external word clock via AES-3 connection. The Benchmark ADC-1 was tested and provided rock solid clock to the Yellowtec Puc 2. Rock solid when locked to 44.1 and 88.2 via AES-3 signal from ADC-1. At higher sample rates, the Puc2 seems to prefer its internal clock.

**Pure Music sounded best when used in 64 bit mode and power of two upsampling enabled. For redbook CDs that were 44.1 SR, upsampling to 88.2 via Pure Music provided the best sound. The 88.2Khz Clock was provided via the Yellowtec Puc2. DSP functions on Pure Music “off” except for upsampling/meters off and in “Less is More” mode.

*** All USB ports on the macbook and mac mini are not created equal. Some of the ports share other busses such as isight, IR, and bluetooth. You can also disable the IR receiver in system preferences.

A usb cable that separates the DC power leg from the data wires with spacing and shielding is recommended. I use a Wireworld usb cable with this key design feature.