Surround Sound Speaker Systems
- Written by Sumit Chawla
- Published on 17 July 2008
Interview with Keven Voecks
Developing the Revel Ultima2 Loudspeaker Series - A Q&A with Kevin Voecks, Director, Revel Products
Sumit: When did plans for the Ultima2 series take form?
Kevin: Work began as far back as 2004. The tweeters and the enclosures were the longest lead-time aspects.
Sumit: During a previous conversation you had mentioned that you approached the design of this series from the ground up.Â Even so, the Salon2, Studio2 and Voice2 ended up sharing some design characteristics of their predecessors.Â Can you please comment on this part of the design process?
Kevin: I didnâ€™t want to take anything for granted in the conceptualization and specification process. That even included the basic topology of the modelsâ€”as well as how many models there were. My conclusion was that the Salon2, Studio2 and Voice2 topologies were still the best approaches. The Salon2 and Studio2 were originally specified with rear tweeters, but we discovered during development that they were no longer required (see below). The original Ultima series included the Embrace bipole/dipole surrounds. Dipoles and bipoles time is past, because they were originally specified due to the limited bandwidth matrixed surrounds of days past. Not only are their (theoretically) less-directional properties not now required, but bipoles and dipoles are inherently much less timbre-accurate than monopoles. Since the advent of full-bandwidth discrete surround channels, music mixers have been putting a lot of music into the surrounds (in addition to the fronts). Quite simply, if you play an inferior speaker at the same time as the front speakers, it will result in degraded sound quality. These facts led to the inescapable conclusion that the surrounds should now be very high-quality monopole designs. Since most people demand an on-wall form factor for surrounds, we were challenged with making on-wall speakers of a far higher sonic caliber than ever existed on the market. That really defined the â€œGem2,â€ which is equally suitable as a front L/R loudspeaker. Switchable boundary compensation circuits allow for the use of the Gem2s either on-wall, on a bookshelf, or on stands away from boundaries.
Sumit: All the Ultima2 models use newly designed transducers.Â How have they evolved over the years leading up to these new designs?
Kevin: The Ultima2 woofers and midranges are far more sophisticated than the original Ultima transducers. In common with the original Ultima transducers, the Ultima2 woofers and midranges behave like theoretically-ideal pistons throughout their operating ranges. However, the motor systems are much more sophisticatedâ€”incorporating distortion-reduction mechanisms that even compensate for the tendency of the voice coils to â€œpullâ€ the magnetic flux fieldâ€”which would otherwise result in motion-dependent distortion. In fact, double-blind listening tests reveal that the Ultima2 series models sound dramatically â€œcleanerâ€ than the original Ultima series. It is interesting to note that we did not find this to be the case in comparing the original Ultima series to competitors that came along during the years! The Ultima2 series is capable of far greater dynamic range at the loud end of the range. Whatâ€™s more important to me personally is that itâ€™s as if the â€œnoise floorâ€ was greatly reduced, providing breathtaking detail at low volumes and an incredible sense of â€œblackâ€ between the notes.
The tweeter is the result of an extensive development effort between three companies. It simply sets new standards for low coloration and unparalleled transparency.
Sumit: The tweeter dome is made out of Beryllium.Â What advantage(s) does this material offer over the materials that Revel has used previously?
Kevin: The combination of characteristics of Beryllium in terms of velocity of sound, density and Poissonâ€™s ratio offer the best performance of any known material. Note that the density of Beryllium is approximately half that of diamond!
Sumit: Is the dome manufactured by Harman?
Kevin: The dome is manufactured for us by an American company. We consulted with them to provide critical know-how for the challenging task of forming the Be dome.
Sumit: The waveguide is in its 3rd generation now.Â What are the differences in design and performance compared to the waveguide which was used on the F52s?
Kevin: The Ultima2 high frequency waveguide benefited from our on-going R&D regarding modeling and optimizing waveguide performance. In practical terms, it allows us to better match the directivity of the midrange and especially to optimize the higher-frequency dispersion. Our in-house â€œstereo lithography apparatusâ€ which allows us to make tooled parts in only hours was critical to the development of the waveguides. Extraordinarily small dimensional changes result in significant performance impact, so the ability to create slightly altered â€œtooledâ€ waveguides at will is critical.
Sumit: The rear tweeter found on the Studio is absent on the Studio2.Â What was the reason behind this?
Kevin: I specified rear tweeters for the Salon2 and Studio2. However, during development we discovered that the combination of the dome profile, the waveguide (and their interaction) and the complex-radius baffle resulted in such good dispersion (and power response) that the rear tweeter was no longer required.
Sumit: The Gem2 can be wall-mounted.Â You also offer in-wall designs in the Performa series.Â How does a wall-mounted design compare to an in-wall design?
Kevin: They are both working into â€œhalf-spaceâ€ or 2-pi environment, which increases the predictability of the effect of the boundary. The Gem2 is Revelâ€™s best-sounding loudspeaker for 2-pi applications.
Sumit: Is the fact that they are at or near a boundary beneficial?
Kevin: It offers some advantages. First of all, the interaction with the wall is known in advance, unlike floorstanding speakers, in which case the speaker-boundary interference response (SBIR) is unknown. Secondly, the solid angle gain can be used to advantage to contribute to a higher system sensitivity.
Sumit: You don't know what room they will be in, so you can't predict their interaction with the room modes.Â How does this play into the loudspeaker design?
Kevin: It is true that we cannot predict the result of room mode/loudspeaker interaction. First of all, we make speakers that have extraordinarily flat response, with very little dynamic compression. In addition, the Ultima2 series speakers have adjustable low frequency cut controls that can facilitate placement when they cannot be placed optimally, or in environments with very energetic modes.
Sumit: Will there be a followup subwoofer for this series?
Kevin: There will be an Ultima2 subwoofer early next year. It has taken a long time to come out, as it will simply leapfrog the performance of existing subwoofers. I promise it will be worth the wait!
Sumit: Is there anything else under development that you can talk about?
Kevin: There will be new developments at CEDIA in September!
Sumit: I look forward to seeing the new introductions at CEDIA.Â Thank you.