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EVE Audio: Ten Years of Loudspeaker Design Innovation-eveaudio-kerstinmischke-rolandstenz.jpg
Roland Stenz and Kerstin Mischke with the EVE Audio product family.

Ten years ago, Roland Stenz embarked on a new venture: EVE Audio. Stenz had ambitious plans, launching the company with an entire line of studio monitors and subwoofers already in place, and with the aim to be the first professional loudspeaker company to integrate DSP into every product. To kick-start his business, Stenz tapped his experience as CEO and co-founder of ADAM Audio.

A decade later, EVE Audio products can be found in 60 countries; the line was expanded with the introduction of the SC3070 3-way monitor in 2020 and the 4-way SC4070 monitor this March.

EVE Audio’s products are based around an innovative air motion transformer transducer. It’s a development that was invented by Dr. Oskar Heil in the 1970s, reimagined for the EVE line. Speakers are designed and tested at the company’s headquarters in Berlin’s "Media City"; the historic complex, in the former home of East German state broadcaster Fernsehen der DDR, houses one of Germany’s largest anechoic chambers, as well as an echo chamber.

Gearspace sat down with Stenz and Kerstin Mischke, EVE Audio’s director of international sales and marketing, to learn how EVE Audio has evolved over the past decade, the challenges of loudspeaker design, and what makes their speakers unique.

Roland, tell me about your background. You came from broadcast?
Stenz: My experience wasn’t directly in broadcast, but I worked at a huge R&D company in the GDR that developed products for radio and television broadcast. It was nearly impossible to go into a shop in the GDR to buy things like a microphone or studio tape machine; we simply had to build gear on our own or we didn’t have it. With EVE Audio, we are here still in this same area in Berlin, in the original complex next to this R&D company and old East German TV facilities. Some of these studios are in use till today—of course, with new technology.

After the reunification, I moved to a company in West Berlin; I built loudspeakers and some electronics. I went to university and studied electronics, and later I founded ADAM Audio with my partner. As one of the owners, I was the general manager leading ADAM Audio for 11 years.

When you launched EVE Audio, how did your design philosophy evolve?
Stenz: I wanted to try something new, to implement DSP, for example, from the beginning. The construction was also a little different; we had a bass port on the back side and front-facing operation with our SMART knob. There's an LED ring around that, and this all is different from my past work.

Mischke: I also used to work at ADAM. For 11 years, we used the air motion transformer. It's the coolest thing on the planet. We continued to use the air motion transformer, but Roland made some changes. The inner construction is different, and we added a grid for protection. These changes were not obvious to the clients at first, but we believe strongly in that technology, and to use any other transducer technology would have been strange.

Was it always your plan to launch with a complete line of products?
Mischke: That was definitely the plan. When we launched, we came out with eight speakers and four subwoofers. We wanted to be taken seriously and made that clear from the beginning. All of a sudden, all the press people were writing about it.

You have pretty sophisticated R&D facilities, including an anechoic chamber.
Stenz: Yes. When we looked at this old complex, I asked the landlord whether this old anechoic chamber still existed, and it did. The room was built in 1957. This makes development much easier and more sophisticated. We can test in more detail and it's easier to make the right parts. We also have the opposite, a large echo chamber, where you can make total energy measurements.

If you only measure loudspeakers in an anechoic chamber, then you only get an idea about the loudspeaker from the microphone position. This generates flat curves. But if you go in the shop, then you'll hear that every speaker sounds different. Although the frequency response is always flat, in an echo chamber, you can see the total energy amount that a speaker delivers to the sides or to the backside, and how the cabinet behaves.

But in the end, it’s about listening to a lot of music in different rooms, and luckily I have so much experience with music that I know how a choir should sound, or in a big orchestra piece, what the first violins are doing or the second violins are doing.

I follow the scores sometimes just for fun, and then I can get an idea about the balance of the speaker. And sometimes it’s plus or minus a half-dB in a wide frequency range, which is not really easy to discover in a frequency chart. Plus or minus a half-degree, it's still a flat curve. But it is very audible, and you need to have a lot of experience to handle these small, wide-frequency-range issues.

What are the challenges of scaling technology across a range of products?
Stenz: Surprisingly, adjusting the frequency response is the most difficult part. Because if you have a speaker that doesn’t reach really low frequencies, then our brain immediately calculates that lower mids are more present. And if the lower mids are more present, then the mids disappear, and then the total balance of what you hear—or what your brain thinks that you hear—can be totally different.

Mischke: It's really a process. Roland listens to the speaker one day, then he leaves it until the next morning and starts with fresh ears. He’ll leave it aside for two, three, four days, maybe for a week. Then he comes back again, and it starts again. To me, it's like creating an instrument. It's not just putting parts together.

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The SC4070

How do you approach design and testing differently for drivers versus a system?
Stenz: I really don't like when some manufactures or engineers say, for example, “this speaker sounds amazing because of the tweeter.” This is meaningless. There's always a balance of components. To make the best compromises achieves very good results.

Take the driver—a woofer, for example. If you consider the material of the diaphragm, you can say that to have good bass reproduction, you want to have a very stiff diaphragm.

So, you start to develop various diaphragms. If you knock on a very stiff diaphragm material, typically, it sounds like a bell. So you hear a resonant tone. You could have the idea, “okay, I will put a damping layer on the diaphragm.” Then, when you knock on the diaphragm, it’s not resonating anymore, but unfortunately the diaphragm is suddenly three times heavier, and then you need more amplification to drive it, and the voice coil can overheat.

And you can say, "I have thousands of watts in this speaker," but the reason is that the diaphragm is so heavy. You have to find the right balance between stiffness, resonance, and weight. Every manufacturer has different ideas and philosophies about that.

You’re the first loudspeaker manufacturer to use DSP in every product. Why is that important?
Stenz: From the beginning, the idea was that the speaker should behave like a normal analog studio monitor, but I wanted to achieve this with built-in DSP. It's nearly impossible in the analog domain to control the filters; that’s why we created the SMART knob. But we never would say DSP-based speakers are better than others.

How do you decide how much DSP control to give the user?
Stenz: It is absolutely comparative to a normal analog studio-monitor design. You have shelving filters, volume, notching, but nothing extra. If you offer all these functions to customers, everything that is possible, then you open the doors to too many opportunities. But we still want to keep the sound control over our products.

When I started EVE Audio, I had to decide between analog and digital, and I did a lot of listening tests, double-blind tests with highly regarded sound engineers, and in the end nobody could really say what was different, better or not and so I decided to continue with onboard DSP.

Tell me about the evolution of your air motion transformer.
Stenz: This principle that we use now is not so old; the original development goes back to Mr. Oskar Heil, who developed that technology in the 1970s. Nowadays its used by a few manufacturers, but due to my experience using that air motion transformer technology, I felt confident to make some changes for the better, as far as the magnetic field and the diaphragm materials and thickness.

It is a quite complicated diaphragm. You have these aluminum structures on it, and you can play a lot with these different aluminum bars, so it changes the weight of the diaphragm. It changes the resistance of the diaphragm and the connection to the amp. The distance between the walls of the folds can be varied, and the height of the folds can be varied. I played a lot with variations and in the end I found a good working design.

I opened the surface plate with wider slots. With the air motion transformer, the air needs to pass through an area where the magnetic field is strongest. Normally you have the strongest magnetic field when you close the front plate. But then, no sound energy can go through. You have to open the slots to balance between sound reproduction and magnetic field. We did immersive tests with several versions to find a good working tweeter, but in the end we opened the front slots. Once we optimized the prototype, we implemented this design into our mass production.

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The air motion transformer.

How would you describe the difference between this and a dome driver in terms of in performance?
Stenz: One benefit is that the unfolded diaphragm area is four times larger than a normal dome driver. This unfolded diaphragm is covered with traces where the signal current goes through. In a dome driver, you have a diaphragm, and the diaphragm is only driven by the voice coil. The voice coil goes one to one with the electric signal, and then the diaphragm starts to resonate.

In an air motion transformer, the folds work against each other. There is a speed transformation between the folds and the air at a 1:4 ratio. It’s like the way you breathe: Your chest moves very slowly but has the potential for much higher airspeed, and when you blow harder, you can blow out a candle more easily. But, it’s not so easy to blow out a candle with your breath. And in comparison to a dome driver where only the voice coil is the motor, you can state: in an air motion transformer, the complete diaphragm is the motor.

How does that inform what we hear?
The most important thing is a balanced speaker, meaning all frequency ranges should be reproduced in a very balanced manner. A speaker, in my opinion, needs to work for all music. And as a sound engineer, you should be able to distinguish bad recordings or bad mixes from good recordings and good mixes.

Of course different speaker sizes provide different “working feeling.” A speaker that goes down to 20 Hz is useful for cinema productions; smaller speakers, like our SC203, are useful for mobile applications.

Mischke: In the end, it's a matter of taste. Sometimes air motion transformers are known for being a bit aggressive, a bit harsh, a bit upfront, but it's not the air motion transformer, it's the overall balance of the speaker. If you highlight the highs, it’s no wonder that they appear to be more obvious. We can talk about the size and we can talk about what may fit or not, but in the end, the ears decide.

Stenz: Another advantage is resolution of the tweeters. Some people are a little bit surprised by the sound reproduction of an air motion transformer, and they think it's a level issue. But it's not a level issue, it's a resolution issue.

Let’s dig into the cabinet design.
Stenz: The cabinet size is mainly defined by the need for the woofer and the dynamic behavior of the complete speaker system. As a designer, you have to decide whether you want to have a vented or sealed cabinet, or a cabinet with a passive radiator.

A sealed cabinet is just an airtight box with a woofer built in. This design is known to be precise in bass. But the frequency range is limited to lower frequencies. But when you have electronics in an active speaker, you can use a lot of filtering in the low-frequency area. You have to be very careful tuning the bass because the effect of the filters is a group delay time that gets longer.

If you do too much tuning with electronic filters to have an extended bass range, you can have a lot of bass in the speakers, but it's not dynamic anymore. So you get this kind of slow pumping. We have to balance the ability of the production of low frequencies and punchiness.

An often-used design is a vented cabinet construction. The capability to reproduce lower frequencies is higher but you have to deal with possible port noise. Besides our SC203 and subwoofers, all speakers use a vented cabinet construction.

What are some of the considerations when it comes to the driver/cabinet relationship?
The drivers have to meet certain parameters in order to fit into to the cabinet. This means volume and inner damping of the cabinet. You also have to pay attention to the manufacturing side: It makes no sense to create the most complicated cabinet construction and then have the manufacturer say, "Good idea, but I don't have a five-axis molding machine," or whatever. Then things become unrealistic to make, or require very high price points.

You have the cabinet and a driver, and then decide what to do with the filtering of the drivers to balance low-frequency areas with the dynamics over the entire frequency range of the speaker. Then you come closer to a good result. The rest is fine-tuning with listening tests in studios, different rooms. Normally I do measurements, adjustments, and listening sessions several times, because all of these affect each other.

What’s next for EVE Audio?
We have a very ambitious and talented team with lots of ideas, we have an amazing infrastructure here on hand, and are ready for the next ten years or more! Our knowledge is not only about acoustic design. We are deeply experienced in analog electronic, DSP, and software design. This opens a lot of opportunities to think about products. Audio networking starts to be more and more interesting. New products are in the design process, but it is too early to talk about them. But, stay tuned and keep watching us.

Learn more about EVE Audio at www.eve-audio.de.