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Revel F36 Speaker Engineering Advancements

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To label Revel’s new Concerta2 line as an "update" is really a misnomer. Revel, which is part of Harman’s Luxury Audio Group, isn’t in the business of cranking out speaker updates for the sake of announcing a new model.  On the contrary, part of Revel’s mantra has been that a new speaker has to have a “distinct sonic improvement” over the previous generation.  While we can all say that’s just marketing speak, Revel’s real-world practice has shown that they’ve been pretty faithful to that mantra.

The Revel team felt that the new Concerta2 line had to have measurable sonic improvement but, as Mark Glazer, Revel’s principal engineer, told me there were three more goals they had in mind:

  1. Be visually stunning with a more modern design
  2. Be easier to drive
  3. Hit Revel’s target price-point for the line

Even if you didn’t know this aspect of Revel’s DNA or those goals, you’d certainly sense it by placing the new Concerta2 line against its predecessor.  In fact, at first glance you’d doubt that they harkened from the same family tree.

Gone is the boxy look of the original Concertas.  The Concerta2s sport a beautifully rounded and tapered enclosure that calls to mind some of the same traits of the Ultima2 and Performa3 line.  The Ultima2 uses nine 4mm layers of MDF that are glued together and bent as one piece.  The Performa3 line uses curved, multilayer MDF but the side and back are routed. In contrast, the Concerta2 line uses MDF sheets with Kerf cutting. Kerf cutting slices a series of slots into the MDF, allowing it to be bent to the desired curve.  The Kerf-cut MDF is then reinforced with an additional layer of MDF with multiple  “picture frame’ braces added. 

Kerf-cut enclosure of the Revel F36.

Kerf-cut enclosure of the Revel F36. Photo credit: Revel.

The result is an incredibly stiff and inert enclosure with all the benefits of MDF at the price point Revel was targeting. I can say first-hand that giving the F36’s a good series of knuckle raps on the speaker cabinet showed that Revel succeeded. Unlike the Ultima2 Salons, however, which have a totally consistent sound from one end to the other when you knock on them, the F36s had a few points on the speaker cabinet where the knuckle wraps sounded more dense or more hollow in line where the internal bracing is located.

Revel Concerta2 F36 measurements

The Concerta2's tweeter has an improved response thanks to the included waveguide and acoustic lens.
Measurement Courtesy of Harman International.

The acoustic lens on the tweeter has purpose.  Don't remove it!

One look at the Concerta2’s front baffle shows additional areas of improvement and refinement.  Through their acoustic and psycho-acoustic research, Revel has always advocated for wide dispersion and accurate off-axis speaker response.  The new Concerta2 models show advancements in this area.   In Revel’s previous generation waveguides, for example, there was excess directivity and lower output above 9kHz. In both technology papers and measurements that Mark Glazer provided to me, Revel has improved the output above 9kHz by as much as 3 dB. Revel has also matched the directivity of the midrange at the crossover better thanks to a large, gentle blend radius at the exit of the waveguide and adding an acoustic lens in front of the tweeter’s dome. So if you’re the type who likes to tweak your speakers, please don’t remove the tweeter’s acoustic lens and then say that you hear a “dramatic sonic improvement.”

Revel Concerta2 F36 graph sum of all drivers and tweeter.

SPL vs. Frequency of each driver and the overall sum in the F36's 2 1/2-way arrangement.
Measurements courtesy of Harman International.

Mark told me that to increase the F36’s sensitivity, a third woofer was used instead of a separate midrange (as in the Concerta F12). All three drivers are identical 6.5-inch anodized aluminum cone woofers but don’t have the same crossover frequency.  In this configuration, which takes advantage of the higher-impedance woofers, Revel has implemented a crossover design that divides the two lower woofers with the top woofer  (drivers are crossed over at 1.8kHz and 600Hz).  In essence, the top woofer also supplies sufficient energy in the mid-band and then crossed higher to the tweeter, while the lower two are crossed lower to the top woofer.

Even though Revel states that the F36 is a 6 ohm speaker, the impedance graph (below) shows that this is really a 4 ohm speaker.  In other words, you should try and use the best quality amplification you can afford with this speaker. At 150Hz, the speaker's impedance drops to 3.8 ohms.

Impdedance of the Revel Concerta2 F36 at different frequencies.

Impedance vs. frequency curve of the Revel F36.
Measurements courtesy of Harman International.

At 150Hz, the speaker's impedance drops to 3.8 ohms. This is a 6-ohm rated speaker but in reality it measures more like a 4 ohm speaker per IEC rating on loudspeaker impedance.  You can see by the dip in the impedance curve between the two peaks that system tuning frequency is around 35Hz. The amplitude of the saddle points are quite asymmetric. This indicates a system tuning a bit too low for the available box size needed to produce a more optimal response. This isn't surprising as many speakers make this compromise in favor of aesthetics.

Unlike some other speaker manufacturers, Revel doesn’t use off-the-shelf drivers. The company is known for developing custom driver designs and materials for their particular application.  The Concerta2 follow suit. The drivers are made up of a Micro-Ceramic Composite with two layers of ceramic with aluminum in the center.  Harman’s patented process deep anodizes aluminum, producing a ceramic substrate.  Revel says that because the speed of sound through the two materials is different, there is added dampening. Revel claims that the resulting composite cone is superior to other conventional metal or aramid fiber cones.

The F36 is also a ported design. The port on the F36 and across the Concerta2 line is what Harman calls a ‘Constant Pressure Gradient Design’ (Harman Patent). Harman developed this patented port design to produce what the company claims is the highest output with minimal compression or distortion. Harman says that with the Concerta2’s port, the inner wall of the port is contoured so that the pressure gradient or change in pressure along the longitudinal axis of the port from its inlet duct to outlet duct is substantially constant.  The Performa3 and Ultima2 speakers do not use this port design.

All Revel Ultima2  and the larger Performa3 (F208 and C208) models have contour controls.  None of the Concerta2 speakers have this feature.  The contour switch allows you to adjust the speaker’s bass response depending on room placement with respect to the proximity to nearby walls. Because most AVRs today handle this type bass adjustment with some kind of built-in room correction, Revel chose to omit this feature so that they could stay within the Concerta2’s target price point.

 

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Recent Forum Posts:

head_unit posts on November 23, 2020 01:59
“This indicates a system tuning a bit too low for the available box size needed to produce a more optimal response. This isn't surprising as many speakers make this compromise in favor of aesthetics.” I don't see what that has to do with aesthetics, since a lower port is bigger. Per my friend who worked at Harman/JBL and designed many Revel drivers, the idea is the same as I applied in automotive audio: tune lower than “optimum” to have a more extended slower rolloff, to better match room gain. Regarding F3 and “optimum” folks are WAY too obsessed with F3. It is NOT some holy grail and it is NOT the best figure of merit. When I was lucky enough to meet Dick Small in Indiana in his Harman days, he agreed F3 was just a useful mathematical convenience grabbed from filter theory for his thesis.* It has nothing to do with loudspeakers in rooms; F6 or F10 are more relevant but aced out by F3 because of…Dick Small using that in his thesis! (Understand also this was before Allison had published work on boundary reinforcement http://www.aes.org/e-lib/browse.cfm?elib=2760.)

(*He was a really nice guy, good humouredly laughing in surprise that I had a bootleg copy of his entire thesis Xeroxed out of Jim Novak's personal library. Now THAT, my friends, is some heavy bedtime reading…and yet at the same time, done in a clear manner, kudos Mr. Small!)
Irvrobinson posts on September 12, 2016 18:42
BoredSysAdmin, post: 1152869, member: 28046
Tell it to TLSGuy, ADTGuy who run speakers fullrange. Gene does same, but supplements with few extra subs to even out the bass in room.
I feel that generalizing a bit too much and a bit off on more than few points.

I do this too, but it only works with relatively expensive towers with powerful bass, so the towers are able to keep up with subs. For the majority of budgets, I'd recommend going with smaller mains and bigger subs. I also completely agree with ShadyJ that the best positioning for imaging and mid-high smoothness is seldom a good location for smooth bass response.
BoredSysAdmin posts on September 12, 2016 17:44
shadyJ, post: 1152864, member: 20472
Because the best place for low frequency emission in-room is rarely the best place for higher bands. It doesn't hurt to have that capability there, but the the way most systems are setup, it doesn't help either, since they are typically high-passing their mains at 80 Hz. I feel that full range tower speakers are more a matter of convention than logic.
Tell it to TLSGuy, ADTGuy who run speakers fullrange. Gene does same, but supplements with few extra subs to even out the bass in room.
I feel that generalizing a bit too much and a bit off on more than few points.
shadyJ posts on September 12, 2016 17:17
Because the best place for low frequency emission in-room is rarely the best place for higher bands. It doesn't hurt to have that capability there, but the the way most systems are setup, it doesn't help either, since they are typically high-passing their mains at 80 Hz. I feel that full range tower speakers are more a matter of convention than logic.
BoredSysAdmin posts on September 12, 2016 16:53
shadyJ, post: 1152859, member: 20472
A deep bass f3 on a full range speaker is nearly useless for conventional home audio applications.
Why do you think so?
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