Dynaudio XEO 4 speakers

Dynaudio made a big splash with their wireless XEO speakers two years ago, but their engineering staff has not been sitting on their laurels.  The new second generation speakers feature more wireless bandwidth, better drivers and more extensive tuning.  Our recent visit to the Dynaudio factory in Denmark found their engineers intensely involved in wireless development, so you know this is a solid path for Dynaudio’s future.

The new XEO range, introduced at this year’s Munich High End show builds on Dynaudios initial success, making wireless audio a much higher performance option than ever before.  Watch for a full review soon.

Dynaudio XEO 4 speakers



Dynaudio Evidence Platinum loudspeakers

As the sound-level meter bounces above 105 dB during playback of the title track from Iron Maiden’s The Number of the Beast (and I see nods of approval from the non-audiophile buddies present to take this all in), I’m reminded that you need big speakers that can move a substantial amount of air to really enjoy this kind of music. The same can be said for Mahler’s Symphony No. 5 or Deadmau5, if Maiden is not your favorite faire. Dynamic swing and contrast is a big part of recreating the illusion of live music in your listening space, and a large pair of speakers with the appropriate amount of power gets the job done.

In the day where $200,000 speakers are becoming more and more common, Dynaudio’s top speaker tips the scale at only $85,000 per pair. Yes, yes, the word only is going to offend a lot of people, but if you happen to be in the market for a six-figure pair of speakers, this level of greatness for $85K is a bargain—it’s all relative. After living with the Evidence Platinums for some time now, I see no need to drop $200K on a pair of Wilson XLFs. And that’s enough money left over to put a new Porsche GT3 in your garage. I know what I’d rather buy.

A number of things make the Evidence Platinum speakers unique. Though they are over 6 feet tall, they carve a very small footprint in your listening room, and thanks to a wide range of wood finishes, along with piano black, they should blend in with any décor. While minimalist yet tasteful grilles are included, the precision craftsmanship of the front sculpted baffles beg them to be left uncovered. Those without large pets or small children will have an easier time leaving the grilles off.

No Limitations

Much like a high-performance supercar, the Evidence Platinums have few limitations. And just as an Aston Martin feels different from a Porsche or a Ferrari, all three cars still provide stellar performance way beyond that of normal transportation. Sticking with the automotive metaphor, the Evidence Platinums remind me of the Audi R8: a new concept that offers similar if not better performance than its contemporaries—and with a bit more style. The Dynaudios are definitely one of the most svelte large speakers around.

Having lived with Dynaudio’s much smaller Confidence C1 Signatures for a few years, I notice a striking parallel between the two speakers. The comparatively diminutive C1s, with their highly optimized front baffle, present a musical picture almost like a point source, while the massive Evidence Platinums simply disappear. In a small room at low volume, with equally high-quality electronics driving the speakers, you’d be hard pressed to tell the difference, other than on the deepest low-frequency excursions.

However, in a larger room, when the sound level comes up and dynamic expectation increases exponentially, the Evidence Platinums justify their price tag. Queuing up the Stereophile test CD reveals solid bass performance at 25 Hz, which is lower than what you’ll need for most program material. Playing Mickey Hart’s “The Eliminators” at high volume confirms the measurement; these speakers can punch you in the chest—hard. The four 7-inch woofers move more air than a single 12-inch unit; yet, because of their small size, they are faster, providing mega bass with maximum tone and definition.

The Evidence Platinums make it a breeze to discern between bass players and their respective styles: The difference between a Hartke bass-guitar amp with aluminum cone drivers and a vintage Ampeg amp with paper cones is now easily apparent. This is what adds so much to the musical experience, making your music so much more immersive. And that’s what you should get when you write the big check.

Top-of-the-Line Technology

Dynaudio has left no stone unturned with the Evidence Platinums, taking advantage of the company’s top technological advancements. Relying on silk dome tweeters since the beginning, Dynaudio’s design requires a very labor-intensive process that involves shaping the fine-fabric dome and treating it with a specially formulated coating. The “Precision Coating” used throughout the Platinum range is Dynaudio’s latest refinement to that process. The higher uniformity of the dome’s shape results in a smoother high-frequency response and even more dispersion of mid and high frequencies.

This is clearly evident when comparing female vocals through the Confidence C1s and the Evidence Platinums. A quick spin of Ella and Louis Again uncloaks the difference in the timbre of Ella’s voice, which is already silky smooth and convincing when played through the C1s. By comparison, the Evidence Platinums dematerialize completely, even though they are so much bigger physically. This is truly the magic of these speakers: They vanish like a mini monitor and are transparent like an ESL, yet they have the drive of an enormous cone speaker.

The Evidence Platinums throw a soundstage that is staggeringly wide and deep, but they also get the height aspect right—probably due in part to their physical height. While playing the MoFi copy of Frank Sinatra’s Nice And Easy, I feel as if Sinatra is standing right in front of the speakers, with his voice coming from where his mouth would be.

Custom drivers, check. Precision optimized crossover network, check. Premium electrical and mechanical parts throughout, check. The combination of all these technologies is certainly present in most flagship loudspeakers, but Dynaudio’s DDC (Dynaudio Directivity Control) system is the heart of what makes these speakers perform the way they do.

The combination of the finely shaped front baffle, driver placement and matching the phase response of the individual drivers makes for a more focused dispersion pattern that does not require nearly as much room treatment to sound their best as do many large speaker systems. This is all trickle-down technology from Dynaudio’s professional division, taking advantage of what the company has learned building studio monitors.

Another benefit of this optimization is the ease of setting up the Evidence Platinums. We’ve spent hours (sometimes a day or more) to get reference-caliber speakers to sound their best. The Evidence Platinums sound great right out of their crates before much attention is paid to positioning. About an hour’s worth of fine-tuning brings the speakers to the point where, when Dynaudio USA’s Michael Manousselis stops by to check my work, he merely makes a few fine adjustments and then I’m on my way. These are not finicky speakers by any stretch of the imagination. Even the machined plinth offers a choice of footers for hard and soft surfaces. Once unpackaged, the Evidence Platinums only take a few days of 24/7 play at modest volume to open up and sound their best.

Still Solid, Months Later

After listening to these speakers day in and day out for months, I am still amazed and impressed. It’s easy to get carried away with premium speakers after first listen, especially after running through a number of well-recorded audiophile classics.

This is not the case with the Evidence Platinums. I go out of my way to dredge up even the worst-sounding selections in my music collection, and these speakers do a fantastic job with any program material. There is nothing I can throw at them that trips them up. Regardless of the program material and volume level, we simply cannot drive the Evidence Platinums hard enough to invoke listener fatigue.

With a sensitivity rating of 89 dB and a crossover network of 6 dB per octave, the Evidence Platinums are very easy to drive with either tube or solid-state amplification. Even in my 16-by-25-foot listening room, more than adequate volume levels are achieved with the 20-watt-per-channel Nagra 300i integrated amplifier. I would suggest about 100 watts per channel or more for best results, especially if you like to hear your favorite music reproduced loudly.

While these speakers can reproduce some great dynamic swings, they are highly linear, with their massive stereo image still intact, even at very soft volume levels—again, not unlike a great mini monitor. Chrissie Hynde’s signature vibrato comes through clearly on the original Pretenders album. The delicacy present in “Private Life” puts Hynde in the room, right near the center of the listening position.

Coupled to the amazing Pass Labs Xs300 monoblocks, with nearly boundless power on tap, the Dynaudios really come to life. As I blast Lou Reed’s The Creation of the Universe, there isn’t a point at which the wide, vivid stereo image ever collapses—no matter how high the volume. Much like the Focal Maestro Utopia speakers that we just got done auditioning, the Evidence Platinums excel at reproducing large-scale music, especially drums and percussion—and they do so without fatigue.

You Need a Pair

If you are looking for a statement loudspeaker, look no further than the Dynaudio Evidence Platinum. After six months of constant listening (and punishing) on an incredibly wide range of musical program material, I can tell you that there is nothing that the Evidence Platinums can’t handle, if you have enough amplifier power on tap.

Along with their musical performance, the Evidence Platinums offer a level of fit and finish that is in keeping with a speaker of this level. They exude luxury and will be an excellent fit for the world’s finest listening rooms, a fact that can’t be overlooked when spending this kind of money. Lastly, Dynaudio is a major player in the speaker industry, so this is a purchase that can be made with confidence, knowing the company will be around to support these speakers.

With so much capability, the Dynaudio Evidence Platinums should be your last speaker purchase.

Dynaudio Evidence Platinum loudspeakers

MSRP: $85,000 per pair


Dynaudio Confidence C1 II

Blasting Joy Division’s “She’s Lost Control,” (the 12-inch version), I once again forget that the Dynaudio Confidence C1 II speakers are small in stature, because these stand-mount speakers move serious air.  With a claimed LF spec of 45 Hz, they practically defy physics for a speaker this size.  The Burmester 911 mk. 3 amplifier in room two produces 350 watts per channel into four ohms and proves a perfect match for the C1s, which have a sensitivity of 85 dB/1 watt.  Powered thusly, the speakers never run out of headroom, making for an enormous soundstage in my second sound room (13 by 16 feet).

I keep the volume level high as Bowie’s “The Heart’s Filthy Lesson” tests the speakers’ ability to deliver a coherent rendition of this dense mix, which combines a deep, driving synth-bass line with dissonant keyboard lines and layer upon layer of sound, while Bowie’s lead vocals remain anchored well out in front of a gigantic ball of sound.  This track is tough for $50,000 floorstanding speakers to handle at this volume, but the C1s ace yet another torture test.  Now it’s time for some Iggy Pop.

While the woofer and tweeter of the C1 look identical to the components used in the floorstanding C4, Michael Manousselis at Dynaudio makes it clear that “the Confidence models all feature the Esotar2 driver platform, but each model has its own unique drivers with optimized parameters.  While very similar overall, each speaker is indeed different.”  The C1 is the perfect speaker for the audiophile wanting extremely high performance in a compact space, but it also carries itself well in a big room:  A visit to Simaudio in Montreal earlier this year reveals the C1s playing in Sim’s main sound room (almost 22 by 30 feet) and filling it nicely, with LF output that had me looking for a subwoofer.

A True Destination Speaker

The C1s are easier to drive than their 85-dB sensitivity spec suggests.  Even the 10-watt per-channel First Watt SIT-2 power amp drives them without trouble.  This is also great news for vacuum-tube lovers.  The C1s are tube friendly, and I must admit to being in sonic heaven when coupling the C1s to the KR Audio Kronzilla dual monoblock tube amplifier.  This 50-watt SET amplifier has incredible bass heft with the delicacy of a 300B amplifier, but that extra 40 watts per channel makes for spectacular dynamic swings impossible to accomplish with a low-power SET.

This is an excellent long-term speaker to build a system around, and it only gets better as you upgrade the rest of your source components.  The C1s deliver good sound with modest amplification and cost-is-no-object components, or anything in between.  Their level of resolution makes it easy to distinguish nuances between five-figure amplifiers, but they still sound fine connected to a vintage Harman/Kardon Citation amplifier.

See-Through Sound

The top hallmarks of a two-way speaker and its associated simplicity are transparency and freedom from driver interaction.  Taking advantage of a gentle, 6dB/octave crossover slope, the C1 achieves a level of coherence reminding me of the Quad 57s sitting here for comparison.

The C1s disappear instantly, painting an enormous wall of sound that belies their size.  Cueing up Patti Smith’s “Space Monkey,” the Farfisa organ pulses in and out of the track, almost breathing in the room as if you can hear the speaker cabinet rocking back and forth about to tip over on stage.  A similar rendition of depth is achieved at the beginning of Thin Lizzy’s “Cowboy Song.”  The harmonica at the beginning of the tune sounds miles in the distance, with Lynott’s voice staying anchored as the lead vocals take center stage and the rest of the song builds.

Putting the pedal down with Genghis Tron’s album Board Up The House proves these speakers can play loud, provided you have enough clean power behind them.  Romping through a playlist heavily populated by Slayer, Mastodon and Van Halen underscores the ability of the C1 to play heavy tracks without overhang or fatigue.  This is a speaker that can keep up with whatever you throw at it.  But the low-level resolution is what makes the C1 so special—this speaker is dynamic in a way that no panel ever could be.  During the first guitar break in Zeppelin’s “Heartbreaker,” you can hear the slight hum of Jimmy Page’s amplifier stack right before he goes back to maximum volume.  Twenty minutes rocking out with these and you’ll drop your Magnepans off at the nearest Goodwill on your lunch hour.

The crossover point between woofer and tweeter is 1,800 Hz, but the drivers are so well integrated that there are no anomalies in the critical vocal range.  Male and female vocals are both reproduced with ease.  Johnny Cash’s voice has the right amount of weight and grit to sound convincing, and the C1s equally represent the subtle nuances of the female voice.  Listening to the eponymous album from Roberta Flack and Donny Hathaway via 24-bit/192-kHz download is an exquisite experience—the C1s keep both vocalists properly sorted.  And Ella is just heavenly.

Multiple Personalities

While the C1s will perform admirably with small amplifiers, prepare for a completely different experience if you have a large, high-current power amplifier at your disposal.  The character of these speakers changes, now having more reach and control in the last octave.  Concentrating on music with a lot of LF output, I never really felt like these speakers needed augmentation at the low end of the frequency spectrum.  The famous heartbeat that opens Pink Floyd’s Dark Side of the Moon rumbles the room with authority.

Even when delivering large-scale orchestral music, the small Dynaudios thoroughly convince, especially with the Simaudio 880M monoblocks that just arrived for review. Again, power goes a long way with these speakers.

Behind (and Beneath) the Grille

The C1s have an interesting shape.  The main enclosure—a slim design only 6 inches wide, 14 inches deep and 15 inches high—is bonded to a front panel extending beyond the enclosure boundaries.  Removing the grille reveals the 6.6-inch woofer mounted just over the 1.1-inch Esotar2 soft-dome tweeter.  Using the speakers sans grill also reveals optimum performance.  The grille does not hamper things much, but the nuanced imaging suffers slightly with the grilles on.  Besides, these speakers look much more like sculpture with the grilles removed, so why leave them on?

My review pair came with the $450-per-pair Stand4 stands, which simply bolt into the bottom of the speaker cabinets.  This removes all the guesswork that can surround selecting the appropriate stand—the provided ones minimize stand interference and provide ideal playback height.  Stylish and massive, the stands work well, though I am informed that Dynaudio will soon replace them with the new Stand6 models, which come with a slight price increase to $500 per pair.  Because of the slim form factor of the speakers, I suggest using the Dynaudio stands and leaving it at that.  They are elegant, they complement the speakers perfectly and they have sufficient mass to do their job properly.

In terms of the speakers’ aesthetic, the standard maple finish just seems more Danish to me (and suits my personal preferences), but standard finishes also includes rosewood, cherry wood and black ash.  Black or white gloss and clear gloss lacquer are also available for an additional $800 per pair.

The Signature version of these speakers, at $8,500 per pair, is slightly more expensive than the standard edition.  With the Signature speakers, upgraded finishes come standard and include two extra choices that are exclusive to the Signature model:  Bird’s-eye maple, stained in either a dark-brown Mocca or dark-red Bordeaux finish with clear-gloss lacquer.  An additional bonus to the Signature model is a 10-year warranty, where the standard version has a 5-year warranty.

The Standard and Signature models share exactly the same drivers and crossover components, so they do sound the same.

I’m Keeping ’Em!

The official listening sessions end as they began, playing heavy music louder than I should.  (i.e. Grinderman’s “Evil” at equally wicked volumes.)  The combination of the C1s and the Burmester 911 is too much fun to keep the volume or choice of music at civil levels.  As I repeatedly push these compact speakers to the edge of their performance envelope, they continue to take everything I can throw at them with ease—so I happily wrote Dynaudio a check for the Confidence C1 IIs, which will be the reference speaker in room two going forward.  Their combination of wide-frequency response, natural tonality and high resolution makes them a perfect fit for a top-quality audio system.

The Dynaudio Confidence C1 II

MSRP:  $7,700 – $8,500 (stands additional)



Analog Source AMG V-12 turntable    Clearaudio Goldfinger
Digital Source dCS Paganini stack    Sooloos Control 15    Aurender S10
Preamplifier Burmester 011
Power Amplifier Burmester 911 mk. 3
Phonostage Simaudio Moon 810LP
Cable Audioquest Sky
Power Audience AR6Tss
Accessories Furutech DeMag and DeStat    Audio Desk Systeme RCM    GIK room treatments

Dynaudio Xeo 3 Wireless Speakers

Dynaudio’s reputation for coaxing great sound from a small cabinet remains intact with the Xeo 3 speakers, which add wireless operation to the mix, as do the floorstanding Xeo 5s.  This is indeed an exciting prospect for those not wanting to deal with a traditional amplifier-preamplifier-DAC setup, or the looming cable mess.  For Dynaudio’s Xeo speakers, the term “wireless” is only slightly misleading, as AC power is still required and you still need to connect a small interface to your computer, but you can kiss interconnects and speaker cables goodbye!

Pre-flight Check

The modestly sized Xeo 3s are 7 inches wide, 10 inches deep and 11 inches tall, and are available in white or black, with either glossy or satin finishes.  The front grilles disguise a 5-inch woofer and 1-inch soft dome tweeter derived from Dynaudio’s Excite X12.  This small size allows for multiple placement options.  Our art director has been using them as near-field desktop speakers for some time now with excellent success.  (I received a Marge Simpson growl as I pried them away from her for this review.)

Those preferring to mount the speakers on stands will have the best results using 24- to 30-inch-tall stands, which will keep the tweeter close to ear height.  The speakers’ rear-firing port does not interfere with operation when close to the wall, so placement on a tabletop or desktop also works well. Dynaudio offers its Stand 3X matching stands (available in gloss black, gloss white, matte black or silver finish), which feature cable management for the Xeo power cord and retails for $350 per pair.  If using the speakers on a tabletop, desktop or shelf, I advise placing something small, soft and squishy beneath the speakers to act a buffer between the woofer and said surface. Dynaudio markets its SF1 speaker foot base for $85 per pair as a solution for such applications.

The Xeos have an MSRP of $1,950, with the wireless transmitter costing an extra $350.  It’s worth noting that operating the speakers does not require interfacing them with your current Wi-Fi setup; they have their own direct 2.4-GHz wireless connection from the transmitter to the speakers.  Plugging the transmitter directly into your computer eliminates the need for the provided power supply, which further minimizes desktop clutter.

While a nearly $2,000 price tag might seem high at first for a pair of compact speakers, the Xeo 3s are each equipped with a pair of 50-watt onboard power amplifiers – one for the woofer and one for the tweeter.   Because the digital amplifiers integrated into the speakers is a PWM (Pulse Width Modulation) design, it recalculates the incoming digital signal data in a way that the drivers see the data much like an analog sine wave.  This offers the least amount of signal conversion loss, but does limit the files that can be played to 24 bit/48khz.  Dynaudio’s well-written manual will take you through the full setup in just a few minutes.  I run Windows 7, and my initial trepidation melts away, as the Xeo 3s’ setup requires just a few mouse clicks; our art director concurs that the Mac side is equally trouble free.

Setting a Course

There are a few switches on the back of the speaker boxes with which you will need to familiarize yourself.  The power switch activates the 50-watt built-in amps; once the speakers are on, the remote puts them in low-power standby mode when the speakers are not in use.

The speakers also sport a few other switches, which enable various usage scenarios.  You can designate each speaker as either a right or left channel module in a stereo setup, or you can use them both in mono mode.  When using the Xeos as a main stereo pair, or as rear speakers in a home-theater setup, one left and one right speaker are the obvious choice.  For those wishing to fill a larger space with sound, or those not worried about stereo imaging, the speakers can be set to mono—a cool feature if you need sound reinforcement for a party.

Note that each pair of Xeos has one speaker with a small blue LED light behind the grille, which blinks to acknowledge that the remote signal is active.  While the speakers communicate with each other to preserve the same volume level, there is no volume control on the speakers themselves—so don’t lose the remote!

Multiple pairs of Xeos offer enormous versatility for those wanting sound throughout their listening space.  A second toggle switch on the rear panel of the speakers assigns one of three zones—A, B or C—and each transmitter can be assigned to any of the zones.  All speakers can be set to receive the audio signal from one transmitter and one source, thereby playing the same content on all of them.  Alternately, you can plug different sources into different transmitters (purchased separately) and assign that audio signal to any speaker pair.

These scenarios facilitate, for example, playing computer-based music on one pair of Xeos in a bedroom, while the main room hosts a movie from your DVD or Blu-ray Disc player.  The volume of the Xeo pair in each room can be adjusted independently by their respective remotes.  Again, refer to the well-illustrated manual for setup assistance.

Born to Fly

The Xeo 3s perform beyond what their small size might initially suggest.  The internal amplifiers are well matched to the speakers, optimizing the sound produced and ultimately offering great value.  As with all the other Dynaudio speakers I’ve experienced, the hallmark ease and midrange clarity of the brand is well intact here.  The richness of Anjani’s voice on the title track to her 2006 album, Blue Alert, alongside the delicate and tuneful rendering of piano and saxophone notes, demonstrates just how well the Xeo solution works to create a satisfying musical experience.

Waldeck’s “Slowly” illustrates the Xeo 3’s ability to generate solid, dynamic bass, despite its small enclosure.  Magma’s “Horn Antenna” further reveals the low-frequency capability of these speakers.  Again, table mounting will add a little bit of LF gain and grunt, but at a slight loss of imaging finesse.  The speakers reproduce the other end of the spectrum with equal ease and precision.  The cymbal strikes in Norfolk & Western’s “Letters Opened in the Bar” illustrate a gentle ring and delicate decay.

Further listening with recent Blue Note releases on XRCD confirms the ease with which the Xeo 3s handle acoustic instruments.  The gentle vocal styling present on Jakob Dylan’s first solo effort, Seeing Things, combined with the acoustic guitar on the opening track, “Evil is Alive and Well,” demonstrates the large sound space these speakers can reproduce without losing the delicacy of the track to wireless transmission.

The only restriction to the Xeo system is the 24-bit/48-kHz limit of incoming files; for now, those with major high-resolution music collections will not be able to enjoy full-bandwidth audio with a Xeo system.  The Dynaudio Xeo 3 speakers present great value, fantastic sound and excellent build quality to the music lover who is perhaps not ready to go for a full-blown audiophile system, but who is dissatisfied with the similarly priced wireless offerings from Sonos, B&O and Bose.   In this respect, the Dynaudio Xeo 3 is miles ahead of the competition in terms of its natural delivery and tonal finesse.

Addidional Listening

By Jeff Dorgay

Of course I had to torture these speakers with some Iron Maiden, Slayer, Van Halen and Zeppelin just to see if they could take it.  And like the Confidence C1 IIs I’ve been using as a reference in room two for a year now, these tiny Danish marvels rock the house—or in this case, my desk.  Using the Xeo 3s on either side of my 30-inch Apple Cinema Display makes me wonder why anyone would ever want a pair of headphones.

The mix is immersive, with the stereo image unfolding between me about a foot in front of my head, as I blast David Lee Roth’s “Ice Cream Man,” and then quickly segue to Maiden’s “Powerslave.”  The small, wireless Dynaudios provide fatigue-free listening during long photo-editing sessions, and underline just how much they have in common with the Confidence series.  This is where you can really reap the benefit of a compact speaker produced by a major speaker company that builds its own drivers, and that possesses extensive research and design capabilities.  The technology trickle down is tough to ignore.

Even if the Xeo 3s don’t turn you into a sound-crazed audiophile right away (but they just might), don’t forget that analog input.  It’s a great way to augment the sound of your television, or perhaps sneak a turntable into the mix.  Plugging the Pro-Ject Debut Carbon table (paired with the Ortofon 2M Red cartridge and Lounge MM phonostage) into the Xeo expands my desktop/small-room experience tremendously.  Spinning some of my favorite albums in this space has me forgetting all about the high-res files on my Mac mini.

Everyone on the TONEAudio staff who had a chance to play with the Xeo 3s agrees that they are excellent in every way, from their subtle aesthetics to their ease of setup and use.  We are happy to award them one of our Exceptional Value Awards for 2013.

The Dynaudio Xeo 3 Wireless Speakers

MSRP: $1,950 per pair; $350 for the Xeo wireless transmitter; $350 per pair for optional Dynaudio Stand 3X; $85 per pair for optional Dynaudio SF1 speaker foot.




Speakers Piega P10
Amplifier Mark Levinson 335
Preamplifier Coffman Labs G1-A
Digital Sources Audio Research CD3 MKII    dCS Purcell processor    EAD 9000 MKIII DAC   Genesis Technologies Digital Lens
Cables Jena Labs Valkyrie and Symphony interconnects    Jena Labs Twin 15 speaker cables
Power Conditioner Running Springs Audio Haley
Power Cords Cardas Golden and RSA Mongoose
Accessories Mapleshade SAMSON racks and shelves    ASC TubeTraps    Cathedral Sound room-dampening panels