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RBH Sound SI-615 In-Ceiling Atmos Speakers Review

RBH Sound SI-615 In-Ceiling Speaker

RBH Sound SI-615 In-Ceiling Speaker


  • Product Name: SI-615
  • Manufacturer: RBH Sound
  • Review Date: March 13, 2019 00:00
  • MSRP: $525/ea
  • First Impression: Gotta Have It!

RBH Sound SI-615

  • Series: Signature In-wall
  • System Type: In-ceiling 2-way Speaker
  • Frequency Response: 50Hz-20kHz (±3dB)
  • Sensitivity: 88dB (2.83V @ 1 Meter)
  • Recommended Power: 15-120 Watts
  • Woofer: (1) 6-1/2" (165mm) Aluminum Cone
  • Tweeter: (1) 3/4” (19mm) Ring-Radiator
  • Tweeter Protection: Yes
  • Swivel Tweeter(s): Yes
  • Crossover Frequency: 3,000 Hz
  • Crossover Slope: 12dB/Octave
  • Impedance: 8 Ohms
  • Cabinet Material/Color: Black Frame
  • Grille: Magnetic White Steel (Paintable)
  • Cutout Dimensions: 7-3/4" (197mm) Dia.
  • Finished Dimensions: 9" Dia. x 4-3/8" D (229mm Dia. x 111mm D)
  • Weight: 3.65 lbs. (1.66 kg)
  • Warranty: 25 Years

RBH SI-615 Introduction

RBH SI-615 sideviewWhile I love reviewing new floorstanding super towers from RBH Sound, I also recognize in-walls represent a big chunk of their Custom Integrator business. Let's face it, not everybody has the space to accommodate a pair of Signature reference towers in their listening space or those that do simply can't replicate the same speaker setup as a surround channel. But, what if there was a way to get Signature level of performance without having the big hulking box? RBH Sound has an entire line of Signature in-wall speakers that are up to the task, such as their SI-6100 and SI-663 LCR speakers. But with the advent of immersive audio, it was time for them to introduce an in-ceiling speaker at the quality level of the rest of their Signature in-wall line. The SI-615 in-ceiling speakers feature a 6-1/2” aluminum cone woofer and a ¾-inch pivoting ring-radiator tweeter.  The speaker has a great sensitivity rating of 88dB (2.83V @ 1 meter) and the 6 1/2" driver boasts bass extension down to 50Hz (-3dB, free air).  There is a o/- switch on the tweeter mount that allows you boost the treble if desired. RBH claims the SI-615 is primarily designed to be used for in-ceiling channels of object-based surround systems, but is also equally adept when used as a pair for high-end stereo listening or other whole-house audio applications.

For this review, we look at installing two pairs of SI-615's with matching BC-6R insulated backcans as height channels. After all, we don't do the bouncy house speakers for Atmos, and RBH is on the same page as us by not producing them. Kudos to a company that pursues science over marketing.


Installing the SI-615's is fairly straightforward process. First you attach the SI-615 to the BC-6R backcan as shown in our accompanying YouTube video.

RBH Bc6r backcanNote: If you don't have the space to accommodate the 7,84" depth of the BC-6R, RBH does offer a BC-6S that is about half as deep.  You will sacrifice some bass extension going with the shorter can but that's a perfectly fine tradeoff to not having a backcan at all in a tight installation.  The backcan is retrofitable meaning it doesn't have to be preinstalled before drywall during construction.

The backcans are made of 15 AWG steel and are stuffed with insulation. They provide a controlled enclosure for the speaker while also minimizing sound leakage to other rooms. RBH also offers a foam backbox called the FB-6C which simply expands into the attic after you push it through the speaker cut out and provides up to -9dB of isolation. I highly recommend using one of these options if you can as opposed to just installing the speaker free-air.  A speaker of this caliber deserves to be treated like a high performance box speaker. Give it a controlled acoustical environment to achieve maximum performance. 

Note: A backcan may be required for safety/fire reasons in many areas of the country so it's always a good idea to check with your local building codes when installing in-ceiling speakers.

After you've got your backcan or backbox figured out, simply use the carboard cutout template RBH provides with the speaker to trace your hole in the ceiling. Once you cut out the hole, you can either push through the FB-6C foam backbox or install the speaker with backcan using a power drill on the lowest torque setting until you hear/feel the clamp lock onto the drywall and pull the speaker flush into place. Be careful not to over tighten or you will damage your drywall and/or speaker.  Oh, do connect the speaker wire before pushing the speaker through the wall. I've heard stories from installers that forgot this very critical step and it had them scratching their heads wondering why the speakers weren't working during the calibration phase. These aren't wireless, so be sure to make your connections!

One nice touch I just wasn't expecting was the magnetic grilles RBH included with the SI-615.  You simply push and twist them into place until the neodymium magnets line up and you're good to go. In my case, I carefully spray painted the grille covers black before installing them to match my ceiling.

Note: Be sure to remove the cloth lining inside of the grill before attaching the grills to the speakers otherwise you will sacrifice some high frequency performance.

Placement and Set Up

Since I have two rows of seating, I attempted to get the best possible coverage for both by ensuring the front and rear height channels weren't too close or far from either row.  Both sets of height channels were positioned about the same distance apart as my front and back channels with the front height about 2-3 feet in front of the front row and the back height channels about 2-3 feet behind the back row of seating.  The angles work out closely to what Dolby recommends (30-55 degrees) depending on whether the listener is positioned in my front or back row. The speakers are placed about as far apart as the main and back channels, again per Dolby recommendation. Height of the speakers relative to the listening position is about 2X that of my side and back channels (again within the 2-3X recommendation from Dolby). However, my 8ft ceilings did somewhat restrict how much separation I was able to achieve between ear level and height channels.

See:  Dolby Recommended Speaker Placement

Speaker Layout  RBH SI-615 grille

Speaker Layout Audioholics Showcase Theater Room (left pic) RBH SI-615 with standard white grill cover

The SI-615's do have a pivoting tweeter but I left it in the default position as I didn't find much use for directing only the tweeter towards the listening area. In fact, I believe height channels work best to provide broader as opposed to focused coverage which is the job of the ear-level "bed" speakers.

For installations where the angles are excessive (i.e. placing the height channels towards the front of the room), it may be prudent to consider a pair of VA-615s which have a 15-degree fixed offset 6½-inch woofer and 1-inch pivoting tweeter which allows the speaker to be pointed more directly at the listening position rather than just the tweeter alone.

I may add an additional pair of height channels towards the front of the room to do a full 7.1.6 Atmos setup when I get my hands on a AV processor that supports it, but right now I will just have to "settle" for 7.1.4.  During the time of writing this review, I was using the Yamaha CX-A5100 Atmos processor and MX-A5000 11CH amplifier to power all but my Status 8T front channels.  I chose to bass manage the SI-615's crossing them over at 90Hz. I see people on various forums touting the "bass" of the height channels which makes little sense to me since any good home theater uses multi subs and that is where ALL of the bass for small speakers (usually the front channels too) should be routed to.  I would suggest using bass management and at least an 80Hz HPF on these speakers if you're using them for height channels. However, if you're running them as a stereo pair, then by all means, go full range.



SI-615 Impedance 

RBH SI-615 Impedance/Phase with and without back can

RBH rates the SI-615 as 8 ohm impedance, but they actually measure a bit lower at very high frequencies. In order to spec a speaker 8 ohms, per IEC, it should not drop more than 20% it's nominal rating (6.4 ohms). It appears RBH is using a 4-ohm tweeter to increase system sensitivity. Stil,l the phase angle is rather benign and given the high sensitivity, these should be an easy load for any receiver to drive without incident. The backcan raises system resonance from around 45Hz to just under 100Hz. You give up some bass adding the backcan but the isolation it provides is well worth it, especially since it will be used bass managed in most installations.

SI-615 Frequency Response 

RBH Sound SI-615 2-meter in-room frequency response (smoothed)

This is a smoothed frequency response measurement of the SI-615 installed in the ceiling measured 2 meters away. The switch on the speaker (0 or -) toggles between woofer with or without resistor padding relative to the tweeter. IF you want the speaker to be subjectively brighter sounding, set the switch to “-“. I didn't find this to be necessary in my listening tests and instead preferred to employ the PEQ of my Yamaha CX-A5100 AV processor to do final system tuning.

Listening Tests

RBH SV661WRI started out my listening session with the Dolby Atmos August 2014 Demo disc. I familiarized myself with the Ricky Iglesias Bailando music track listening in regular 7.1 Dolby TrueHD. In regular 7.1, the kid screaming "Bailando" at the beginning has a slight elevated effect but more diffuse using my RBH 66-SE/R Dipole/Bipole speakers. When I switched to 7.1.4, I definitely heard more elevation in his voices with the pair of SI-615's but it didn't blow me away like I've heard on other 7.1.4 systems. In fact, I had similar experiences with other Atmos cuts from movies like Unbroken. The elevation was present and the surround field a bit more enveloping, but I wasn't blown away. It did occur to me that I literally had 8 surround speakers in close proximity to the listening area, so it was likely my brain wasn't able to differentiate the localization cues as well as it would have with more separation between speakers.  Thus, the only solution I could think of was to change my side channels to direct monopoles since I simply couldn't do the alternatives (raise the ceiling height or make the room bigger).  RBH Sound just unveiled their new SV-661WR on-wall speaker with AMT tweeter so  I swapped out my side channels for these and gave it another run.

Note: We confirm Dolby's recommendation is sound to change out side and rear channels from bi-poles to monopoles in order to get the best separation possible between ear level and height channels in immersive surround sound.

With the SV-661WR monopoles running side channel duties, I was able to clearly delineate directional cues above and surprisingly behind me. The boy’s voice in the song Bailando was clearly coming from above me as it was meant to and the clapping sounds were more focused and pinpointed.  I was hearing the Atmos immersive bubble that reviewers often talk about.  I was pleasantly surprised just how well the SI-615's were keeping up both tonally and dynamically with the rest of the surround speakers in my system. 

My daughter insisted we watch the movie Get Out, which she owns on DVD. I was a bit hesitant being limited to DD 5.1 but I decided to run it through the DSU to see just how good the Dolby upmixer was. I was happy I did since I really enjoyed the suspense of this movie and was pleasantly surprised at how enveloping the soundfield was. Switching between PLIIx Movie mode and the DSU allowed me to appreciate both the advances in Dolby upmixing and adding the four SI-615 height channels in the mix. The immersive effect from the SI-615's was subtle most of the time but they came to life during chase scenes, fooling me into believing I was listening to a native Atmos surround mix. The DSU really does work excellently with 5.1 ordinary content so do give it a try.

Get Out  Thor

The SI-615s helped to create the seamless soundstage I was hearing from the Atmos soundtrack in Thor Ragnarok 4K/Ultra HD Blu-ray. The storm clouds that converged after Odin's death had me immersed into the landscape.The scene where Thor is first dropped off on Skaar, the planet of junk (not to be confused with Junkion from G1 Transformers cartoon), showcased the SI-615s abilities to provide clear visual cues from above each time junk dropped to the planet surface. I was particularly awed by the realism of the panning of Valkyrie's ship flyby as she entered the scene where Thor was about to be captured by scavengers.


SI-615 RearThe RBH Sound Signature SI-615s proved to be a very capable in-ceiling speaker for Atmos and also a good tonal match for the rest of my RBH system. That speaks volumes since we're talking about matching these speakers with the very best RBH has to offer in boxed cabinet products.  The SI-615s were easy to install, have a very slick magnetic grille that (once painted to match the color of your ceiling) visually disappear, and offer an optional retrofit backbox to provide an isolated controlled acoustical space for them to operate in. They have broad dispersion, play plenty loud, and won't bottom out if driven hard, though I do recommend crossing them over at 80Hz to let your dedicated sub(s) handle bass duties.

About the only thing I can fault about these speakers is their asking price. At $525/ea, it makes them an expensive proposition to add height effects to a system. This costs about 2X what most Atmos-enable reflection speakers run but having discrete speakers of this quality is a big upgrade in sound, especially if you're running Signature Series products from RBH for the rest of your channels. The SI-615s make a welcomed addition to my reference system and I'm happy to report that they've helped me appreciate the leap I've made into a fully discrete immersive surround speaker system.

Have you recently upgraded to Immersive Surround Sound? Let us know if you went with discrete height speakers or the bouncy house Atmos-enabled type in the related forum thread below.

RBH SI-615 Summary


  • Sonics to match RBH Signature series products
  • Great speaker choice for Atmos installations
  • Easy to install
  • Slick magnetic grilles


  • Pricey

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Gene manages this organization, establishes relations with manufacturers and keeps Audioholics a well oiled machine. His goal is to educate about home theater and develop more standards in the industry to eliminate consumer confusion clouded by industry snake oil.

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