July 2015

An Interview With YG Acoustics' Yoav Geva
Interview By Phil Gold

Phil Gold: From our earlier conversations, I understand one of your objectives is to reduce or eliminate friction in your speakers, so that they sound consistent through a wide range of volume levels. How do you reconcile that objective with the decision to go with a sealed box, which must increase the air pressure on the back of the speaker cones?

Yoav Geva: We use two simple methods to keep air-pressure on the back of a cone in check, while avoiding stuffing to eliminate friction: a slightly larger sealed enclosure than would be required if stuffing were used, and a very rigid cone. The former keeps the air-pressure fluctuations within the optimal range as the driver moves, while the latter makes sure that the driver retains its piston-like behavior along its entire range of motion.

Phil Gold: In the original Carmel, the tweeter dome was safe from knocks. Now the dome, although recessed, is exposed. While you have provided a slim protective bar for the woofer, there is none available for the tweeter, and no grills are available. Did you consider that any protective device would impair the sound? And what would happen in practice if a tweeter dome were damaged by a knock. Would the whole unit need to be returned to the factory?

Yoav Geva: The slim protective bar for the woofer acts as its grille, while the tweeter is recessed and therefore protected by the front baffle's geometry. An actual protective device in front of the tweeter would severely compromise sound, so we prefer this solution. In the unlikely event that someone punches the tweeter (so far it's never happened as far as I'm aware), the tweeter can be easily replaced in the customer's home, without having to ship the speaker anywhere.

Phil Gold: Despite the form factor for the Carmel 2 being close to the Carmel 1, it sounds an altogether larger speaker. What are the specific factors that enabled you to get a bigger sound out of the same sized box?

Yoav Geva: Carmel 2 uses a three-chamber sealed enclosure, which optimizes its performance in both the bass and the midrange. To the best of my knowledge, Carmel 2 is the first time that anyone has successfully developed the complex mathematical formulas necessary to design a truly effective three-chamber sealed enclosure. Carmel 1 used a two-chamber sealed enclosure, which can be fully optimized for either the bass or the midrange, but not for both at once. Therefore, the bass-quality in Carmel 2 is superior, while further improving upon the famous midrange-performance of Carmel 1.

Phil Gold: The nominal impedance has gone from 8 Ohms to 4 Ohms. Does this make it a tougher load for some amplifiers? What are the recommendations for amplifiers to get the best out of the Carmel 2?

Yoav Geva: Overall, the ease of drive is comparable. Carmel 2's impedance curve is smoother, which easily makes up for the difference. I recommend 60 good Watts, but with a current-capable amp 45 Watts should also suffice.

Phil Gold: It is easy to understand the BilletCore drivers form the information on your website. But the ForgeCore tweeter is harder for me to understand. Can you expand on the proprietary technology you have incorporated here, what problem it was designed to overcome, and how it does that?

Yoav Geva: Our ForgeCore tweeter has a magnet system that's been CNC-cut in-house to eliminate parallel walls inside it. A tweeter's magnet system acts as both its motor and its enclosure. ForgeCore optimizes the latter, in the same way that eliminating parallel walls in a regular speaker enclosure improves it by reducing standing waves. The end-result is a tweeter with ultra-low distortion.

Phil Gold: Some manufacturers are using beryllium or diamond tweeters, and making a great deal of noise about that. You have not chosen to use such exotic materials. I'm sure you have experimented, or could have bought such tweeters off the peg. What were the factors behind your decision?

Yoav Geva: A tweeter's moving diaphragm consists of two parts: the surround and the dome. In our ForgeCore tweeter, both parts are actually one piece, and therefore it doesn't suffer from a bell-resonance at the outer perimeter of the dome, which can be a severe issue with a hard dome. At the end of the day, the measurements of the ForgeCore tweeter are the best answer to your question: high bandwidth to 40 kHz coupled with ultra-low distortion leave little room for argument.

Phil Gold: Similarly, other manufacturers, notably Wilson Benesch, have pioneered the use of carbon fiber as a cone material for their woofers. While I understand that if you are going to use aluminum, your expensive BilletCore process is the best way to use aluminum, but how does aluminum compare to carbon fiber, paper, plastic, beryllium and other composite drivers?

Yoav Geva: Aircraft-grade aluminum offers an excellent stiffness-to-weight ratio. While some exotic materials offer even better specs as a solid unprocessed chunk, in a stamped or woven driver the weakest link lies within the micro-cracks where the material is bent or stretched respectively. This is apparent when looking at distortion measurements of the finished product – so far we have yet to find another material and/or production-method that can match BilletCore's freedom from distortion, bandwidth and tight tolerances.

Phil Gold: Can you tell us how you achieve internal damping of standing waves without the use of damping materials attached to or stuffed inside the cabinet, and what advantage does this give you?

Yoav Geva: Our proprietary FocusedElimination technology uses precise geometry to prevent standing waves from ever appearing in the first place, rather than trying to absorb them later using stuffing. There is still some damping involved in pinpoint locations, but not as stuffing. The advantage is freedom from friction: friction can't distinguish between an undesired standing wave and a desired sound wave, whereas FocusedElimination can be targeted against the former.

Phil Gold: Did you experiment with dual woofers in the Carmel 2? Besides price, what would have been the advantages and disadvantages of such a design?

Yoav Geva: This question must be answered for every design on a case-by-case basis. In the particular case of Carmel 2, a single mid-woofer offered a better soundstage. By using a long-throw driver, we were still able to offer lifelike dynamics that one would typically otherwise associate with larger designs and more drivers. However, I've worked on other projects in which the exact opposite was true, so this type of choice has to be examined separately for each and every design.

Phil Gold: The new design is certainly more elegant with its subtle curves and one piece panels. Was this just an aesthetic choice or was there another objective here?

Yoav Geva: The choice was made for sonic reasons, and the elegant shape was a very nice side-benefit. The advantage of a curved baffle is that while its physical width may vary from one end to the next, its effective dispersion can remain constant. Both drivers in Carmel 2 thus produce a similar dispersion pattern at the crossover frequency, which helps make the transition between them more seamless. Another new feature in Carmel 2 is that its front baffle is now 35 mm (1.375") thick, which offers very high rigidity.

Phil Gold: How did you make your choice of internal wiring and external binding posts?

Yoav Geva: For internal wiring, our good friends at Kimber Kable have designed for us an excellent solution. It's basically the Kimber Select copper conductor, with a heavier gauge, and without shielding since our enclosure is conductive and acts as its own shield (for techies only: Faraday cage). As for binding posts, we CNC-machine our own out of hyper-pure copper. I'm very proud of our posts' mechanical construction: in addition to offering excellent signal-transfer, they are also very reliable and robust.

Phil Gold: I assume you are busy working on future designs. What can we expect to see from YG Acoustics?

Yoav Geva: We just finished a huge three-year R&D project of revamping our entire speaker-line, which resulted in Sonja, Hailey and Carmel 2. It will be a long while until I'm ready to discuss the future, because all our current technologies have already been implemented in this new generation of speakers.

Phil Gold: Thank you, Yoav.

YG Acoustics
4941 Alison Street
Unit 10
Arvada, Colorado 80002

Voice: (801) 726-3887
E-mail: info@yg-acoustics.com
Website: www.YGAcoustics.com