Publisher Profile

An Interview with Jeff Hedback of HdAcoustics

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Jeff Hedback of HdAcoustics

Laurence A. Borden: Jeff, welcome to Dagogo. Please tell us a bit about your background as both a musician and a recording engineer.

Jeff Hedback: First, thank you Laurence and Dagogo for this opportunity. I’ve always been fascinated by music – especially rhythm, tone/timbre and the energy/emotion of music. I began playing electric bass guitar at the age of nine. After high school I went directly to Berklee College of Music where I majored in Music Production and Engineering, and (honestly) still keeping the bulk of my energies focused on the bass, playing jazz in school and out of school, progressive rock.

After graduation, I landed a second engineer job at a studio (designed by Russ Berger) in Indianapolis. It was actually through that studio job that the next phase of my life began as a fulltime musician. An artist who worked at that studio frequently – Jimmy Ryser – had label interest and needed a band. A back-up ensemble was forged and we worked day and night to capitalize on the opportunity. Arista Records, Clive Davis himself, signed Jimmy and eventually released one record in 1990. That journey brought me to top studios, top engineers, top producers and touring in various parts of North America with the likes of Moody Blues, REO Speedwagon and Nelson (a little humor yes…but true).

Things evolved and I transitioned to play for a guy who was on CBS Records, Henry Lee Summer, for most of the 90’s. Other recording credits include multiple records with a great contemporary folk artist, Carrie Newcomer (Rounder Records) and the first Lisa Germano record. Live gigs you ask…tons of gigs in most every style and setting. One of the styles I’m most fond of is “the blues.” I have been fortunate to learn from several first generation Delta Bluesman including one of my most cherished mentors, Leroy “Lefty” Bates (who was a sideman with Jimmy Reed in the 60’s as well as a session musician for Chess Records).

There’s always a bass nearby and although I’m not playing out live at this time and place, I have much more music to share ahead.

LB: It is no secret that the listening room (or studio) is as important as the gear. What events lead to your interest in room acoustics?

JH: As mentioned, I was always fascinated by tone. In terms of acoustics, the relation of the speaker and room – how it would change the amount of and quality of bass – just grabbed me. As I played more and more gigs, I obsessively strove for the equipment that could yield the most pure tone and representation of my hands on the instrument. Berklee’s program featured a solid offerings in acoustical physics and electro-acoustics. As much as anything, it would have been the experiences where things didn’t sound as expected (be that instruments, live gigs or especially recordings) that drove me nuts to figure out why…and room acoustics always ended up being a major part of the equation.

At the beginning of 2000, I happened upon the opportunity to work part-time at Auralex Acoustics (while still gigging several nights a week). That quickly led to a full time job and a Regional Manager’s Post (as well as artist endorsements and product development duties). Although it’s easy to poke at “Auralex the foam guys,” that company had a great deal of integrity and was very sincere in offering valid product support in a time when no one else thought to do the same. Acoustical Engineer Jeff D Szymanski (P.E.) anchored that company’s acoustical communications in what was essentially an acoustics think tank with some great minds. Standard fare included large room/architectural acoustics, sound isolation and noise control, project studio scenarios, dedicated home theater and certainly 2-channel listening rooms. Having a limited amount of tools within the Auralex product line forced a high understanding of what issues can be addressed by what methods.

Image 1: Recently completed project in Manhattan. Based on Remote Room Test data (see Image 4 below), challenges included excessive midrange decay, asymmetrical room and listening position butted up against rear wall. Panels are RPG Acoustics BAD & Absorption.

LB: What inspired you to form your consulting company, HdAcoustics?

JH: Nice question, it seemed (opening Hedback Designed Acoustics) was a logical step forward. I’ve always been entrepreneurial and desired to offer higher levels of services in regard to not just acoustics but all factors related to a dedicated audio/visual space. I had developed strong connections across a wide range of the A/V markets. I felt that one niche that was under-served was a hole between the very top acoustical firms and the support services offered by acoustical vendors (like Auralex). So that was the original business plan. Since opening in the Spring of 2007 I’ve streamlined the business name to HdAcoustics, been featured in Mix Magazine’s “Class of 2011” and “Class of 2009” for studio design, had multiple hit singles and records come out of my rooms, specifically focused on audiophile and 2-channel clients and had the great fortune to assist wonderful people throughout North America and much of the world (Germany, Australia, and Saudi Arabia for example).

LB: What services do you offer?

JH: Acoustical design and consulting with a focus on small room acoustics. Let me explain, I just love music in small rooms (less than 10,000 cu ft), and the challenges and opportunities for creativity and solving problems with physics. Anything that is relevant to the end function of the audio (or video) system is on my agenda: room size, sound isolation, electrical, HVAC (my family’s business for previous two generations), lighting, etc.

The design process, which is very disciplined, is actually the real service. The outcome certainly melds the technical and artistic. If you’ll allow me to explain, there are five distinct phases of the process starting with Discovery (the gathering of all room data and goals), then Concept Development, Design Development and Documentation (build/install documents), Actualization (my term for the construction phase which always needs support) and finally- Verification (which can be on-site or remote). I purposely have remained nimble as a business so that I can offer full levels of service or just enough support, depending on the client’s needs. The key to every project is communication and understanding how events fit into the process.

LB: Some audiophiles eschew “dedicated” room treatments, opting instead for carpeting, curtains, books and the like. What are your thoughts on this approach?

JH: Simple, I’m for great sound, great tone and whatever approach leads to that. In some ways my thoughts are well stated in a white paper I co-authored last fall (http://www.hdacoustics.net/files/QuickSiteImages/AMS_for_Stereo_List._Rms.pdf). But I can add that my very own open-plan living room passes almost all metrics for great tone (using custom Rhythm Prism speakers from AudioKinesis) with no “acoustical” treatments. The speaker to room to listener equation is a system and there are no prefab solutions or “works in all cases” approaches. We’re in an exciting time in terms of advanced software for speaker design and digital room correction systems, but neither of these negate what happens at the room boundaries. Carpet will help tame the upper mid/hi decay time, curtains can do the same, books can help a great deal but none of these standard furnishings are going to deal with longer wavelengths.

LB: In broadest strokes, there are two categories of room treatments for mid- and high-frequencies: absorbers and diffusors. What are their respective plusses and minuses, and how do you approach their use?

JH: Sounds hits a surface and three things are going to happen. Part of the sound energy is going to transmit through the surface, part of the energy is going to be absorbed and part is going to reflect. The job is to gain control of each aspect of these occurrences toward the targeted response. I like to say there is nothing good or bad about absorption, reflection or diffusion…just how they are used together.

Absorption is generally handled by porous insulations that by tortuous friction convert the sound energy into heat. It’s always key for me to have plenty of lower midrange absorption (in the 150Hz to 800Hz range). This would mean a minimum of 3” thickness in typical fabric covered panels.

Diffusion http://www.gikacoustics.com/news_060109.html is a wonderful tool in my own words. Referring to the three parts of sound hitting a surface, diffusion is gaining control of the reflected energy by altering the path and/or time element of the reflection. Diffusion, from an overview perspective, doesn’t remove the sound energy in the space (which is good). As speaker designers continue to embrace a more spectrally balanced off-axis response, the ability to use diffusion increases.

The proper use of either absorption or diffusion is going to be based on A) the type of and location of speaker, B) the boundary surfaces both type and location again and C) the preferences of the client. These preferences are identified in the discovery portion of the design process.

LB: On your website you describe a variety of diffusors. How do these differ in their acoustic properties, and in their application(s)?

JH: That is true on the PRODUCTS page of my site (http://www.hdacoustics.net/Products.html), but I actually would prefer to first discuss commercially available diffusors. I am an equal opportunity user when it comes to acoustical widgets. I’ll pull from any supplier that meets the need (factoring performance, cost and aesthetics). I recently completed a dedicated audiophile room in which I used two different types of diffusors from RPG, a third type diffusor from Auralex, and LF absorption from GIK and RealTraps. That is not uncommon.

Image 2: HdAcoustics Circle Diffusors in-use, rear wall of dedicated listening room

At times, I tend to seek absorption and diffusion functions at the same location in a given room. This can be done with a “combo” product like the RPG BAD or BAD ARC panels. The combination of hard and soft surfaces is termed amplitude reflection grating. I have designed a few systems that offer results not found in commercial products. These are available only within a design contract and all materials are made to my exact CAD specification by my mill-shop partner.

Image 3: HdAcoustics HAR Slats in-use, ceiling cloud feature in dedicated listening room.

LB: Which products do you prefer for absorption?

JH: I have actually used them all: 705, 703, “attic” blanket, UltraTouch cotton (which I really like), mineral fiber, polyfibers, and of course acoustical foams. There are factors that relate to the way sound enters the porous nature of each material that may make one better in a given room than another. Availability, preferred finish/aesthetics and types of covering are additional factors that might lead to one being more appropriate than another. Having the knowledge of how to read acoustical test data and the experience with the various materials is more important than having a preferred absorption panel.

LB: When designing room treatments for an existing room, is it necessary to take acoustic measurements, or is it sufficient to know the room’s dimensions and construction? Once the acoustic treatments are in place, do you then use measurements to “tweak” the performance, or is that not usually necessary?

JH: Well Laurence, “No” it is not necessary to take “as-is” or “pre” acoustical measurements. But, it is very helpful to do so. The truth is that no measurement will tell you what a room/system sounds like. It takes knowledge of the room (construction through finishes) and knowledge of the speakers/components to put context on any acoustical data. With the right knowledge of the space and proper acoustical data, there is a huge benefit to having such data. I created a specific Remote Room Test Service that utilizes a series of client-captured acoustical files. I script the locations of the mic/speakers for every situation. The test files include several ways of exciting the room and even a Tracy Chapman reference track to hear music I know well in the client’s room. The report generated from that data along with room factors and my experiences has been a very successful path forward.

Progress measurements can certainly be part of various types of projects. This can often include speaker/listener location changes. Typically the acoustical design is so specific that there are not a lot of “moving parts” to be determined later. That said, I do my very best to retain an open mind so that the analysis is rooted in things that matter. With acoustics, it’s extremely easy to change a room but that is not the same as making it “right”!

Lately I’ve been excited by remote room correction in the LF range. Using my combined experiences as an audio engineer, acoustician and bass player, I’ve been remotely writing parametric EQ’s settings that are in fact corrections and do not distort the time domain (i.e., skew the original waveform reproduction).

Image 4: Remote Room data from Image 1 above. This project included Pre studies, post treatment studies and remote LF room correction.

LB: I think most would agree that in the small to medium-sized rooms typically used by audiophiles, bass is more difficult to deal with than high- and mid-frequencies. A well-known manufacturer of acoustic treatment products has opined that one cannot have too many bass traps, though many feel that this can result in overdamped highs and mids. What are your thoughts on this? Based on these and other considerations, how do you incorporate bass trapping into your designs?

JH: One reality is that where you place your speakers and ears is either going to “excite all modes some” or “some modes all.” In most cases, exciting “all modes some” leads to the smoothest, most flat bass response. Modes create “noise” in relation to the original signal. Damping the resonance of modal peaks and narrowing the valleys between is in fact improving the signal to noise ratio. There is a difference between listening rooms and studios. In listening rooms, the goal is to enjoy the experience while a studio requires accuracy. Every room that is enclosed will be better with appropriate bass trapping. A room that may have openings to secondary spaces may or may not. In my own living room, the LF response is smooth and non-resonant at the expense of slightly excessive lower mid decay (from return energy from the secondary spaces). There is no acoustical fix for this, so I enjoy the benefits available in the space (the controlled directivity of the speaker certainly helps overall balance). Much of my work in listening rooms follows that type of “making the right compromise.” People live in spaces and even a singularly dedicated space has to relate in design to its house…these are rooms not labs.

LB: What are your views on Helmholtz resonators for bass trapping? Do you incorporate them into your designs?

JH: Tuned devices are absolutely options I’ll use. The first thought one may have of a Helmholtz resonator is bass trapping. I also use them for lower mid control. However, I rarely ever just use tuned devices preferring to combine passive trapping with tuned devices. The “Q” of the device should not be too narrow and you do have to place the tuned device where the problem is. I also use diaphragmatic and membrane systems which can have advantages in function and finish.

Image 5: Custom designed multi-chambered membrane trap “floating wall”. There is much that the “eye” cannot see that the ear hears in this room.

LB: Let’s return to your years at Auralax, at which you were part of the team that designed the “Gramma” isolation riser (which is protected by a U.S. Patent No. 6,845,841). Considerable confusion exists in the audiophile community regarding coupling/decoupling. Please begin by explaining these terms to us, then tell us how the Gramma works.

JH: Sound travels multiple times faster through materials than through air. Very few materials are acoustically inert across the spectrum and can be very non-linear below 200Hz in resonance. When a speaker actively mates with the floor, the transfer of energy between the two becomes part of the experienced response. Playing bass on all types of stages and especially dealing with the differences between hollow platforms, rigged outdoor stages and fixed outdoor concrete venues drove me crazy. While working at Auralex I began creating prototypes, bringing them to gigs, tweaking, getting input from others at Auralex and eventually I created enough interest from management to fully develop the product. The result is now embraced in settings from live performance amps/monitors, subwoofers, full-range reference speakers. (I’ve seen a great post from a gentleman using the Dunlavy’s, very cool.)

I have no financial tie to the product (just to be clear), but absolutely endorse it and utilize it whenever it seems right. At roughly $60, it’s one of the few immediate change elements a person could try with little risk.

LB: Will the Gramma work with any type of speaker, or is just for subwoofers?

JH: It would be best used with anything floor standing. Would it work for any and all speakers? Simply no. Some speakers designed response is tied to the coupling with the floor.

LB: Jeff, thank you for taking the time to speak with us. We wish you continued success.

JH: Laurence, thank you. This is a true honor and real pleasure. The applied craft of acoustical design for dedicated high performance audio is extremely passionate. The relationships I build with my clients is the true reward as these last far beyond the project’s boundaries. To know that music is being enjoyed (or created) in spaces that I’ve designed is powerful. And to continue to develop the types of remote services that take advantage of today’s technology and the current economy is exciting. I just never know who the next phone call may be!

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