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MonAcoustic SuperMon Isobaric Bookshelf Speaker Review

by March 27, 2023
MonAcoustic SuperMon Isobaric

MonAcoustic SuperMon Isobaric

  • Product Name: SuperMon Isobaric
  • Manufacturer: MonAcoustic
  • Performance Rating: StarStarStarhalf-star
  • Value Rating: StarStarStar
  • Review Date: March 27, 2023 00:00
  • MSRP: $ 25,000/pair with stands
  • Buy Now
Mon Acoustics Speaker Overview
  • Configuration: 2.5 Way Isobaric
  • Cabinet Material: Aluminum 6061 Grade
  • Face Plate Colors: Silver, Black, Red, Royal Navy
  • Bespoke Color: Available on request for additional cos
  • Tweeter Unit: SEAS Exotic T35
  • Mid Woofer: Audiotechnology 6A77
  • Woofer: Eton Bass Woofer
  • Frequency Range: 37hz ~ 25,000Hz
  • Impedance/Sensitivity: 4 Ohm/ 89dB
  • Speaker Dimension(inch): 9.69w x 16.54d x 19.69h
  • Stand Dimension(inch): 10.63h x 17.32d x 23.54h
  • Speaker Weight (lbs.): 80 lbs.
  • Stand Weight (lbs.): 62 lbs.


  • Build quality is second to none
  • Very well-controlled midrange
  • Excellent imaging capabilities
  • All aluminum cabinets make for an impressive sight
  • Interesting solution for speakers’ contact with stand


  • Depressed bass response below 100Hz (fixable w EQ)
  • On-axis angle has a rough treble response


Mon Acoustic MiniMonIn our review of the Mon Acoustics SuperMon Mini, we found it to be a good little desktop speaker for a luxury office space or a small bedroom. A mini speaker with an aluminum cabinet and an isobaric woofer system made it one of the more unusual speakers that we have reviewed. Today, we look at what happens when that design philosophy is expanded into a full-size stand-mount speaker in the SuperMon Isobaric. The size and weight are increased by a factor of seven and the price is increased by a factor of twelve. The SuperMon Isobaric is a seriously high-end offering with a formidable spec list, but what is it like in practice? That is what we intend to find out in this review…


While the SuperMon Isobarics are stylish and classy-looking speakers, they aren’t the kind that will disappear in a room without notice, so people who do not care for the appearance of speakers will not like how prominent they will be. They do not come with grilles to hide their ‘speakerness.’ They are bound to be noticed by guests and will be a point of discussion unless they are placed in a room with so many high-end luxury pieces that they wouldn’t stand out. These are large aluminum stand-mount speakers, and even the stands that they come with are very posh. The stands are some heavy-duty aluminum constructions with three massive legs that come down to a thick base with a slightly chamfered front lip. The base rests on top of large aluminum feet that are tipped in a broad conical spike. The spikes rest in some saucers that protect the floor, and even the saucers are glistening solid metal pieces that look swank.   

SM pair5

The speakers themselves have an unapologetically metallic presentation. That is not a bad idea since much of what the buyer is paying for is the specialized metal enclosure. The front plate can be had in different colors other than metallic grey, and MonAcoustic can work with customers to find a preferred color. The front baffle is flat except for some mild rounding at the top edge and a shallow beveling at the lower edge that continues into the top plate of the stand. The drivers are somewhat recessed into the front baffle. Both the plate of the tweeter and the trim ring of the woofer are anodized black to match the black dome and cone of the drivers. No attempts are made to hide the machine screws, and that gives them an industrial chic aesthetic that would make them easy to blend in with any modernist interior decor. As speakers go, I think they look great, but the appearance of the SuperMon Isobarics will be divisive; those who like the sight of speakers will love them, but those who prefer speakers to be subdued and out-of-sight will likely abhor them.

Design Analysis

SM domeThe SuperMon Isobarics are very involved loudspeakers from an engineering perspective, so there is a lot going on to discuss. Let’s start our discussion with the enclosure design since that is the first thing that would be noticed about the speakers. The enclosure is made from aluminum; a lot of it. The front baffle is 1” thick and the side panels are ⅖” thick. Leather seals are used for resonance elimination, and melamine foam is used for tuning isobaric resonance and port output harmonics. It adds up to 80 lbs., the heaviest stand-mount speakers I have dealt with yet.

The tweeter used is the SEAS Exotic T35. This is a heavy-duty 1.5” fabric dome tweeter with a 600Hz free-air resonance and 100 watts of long-term power-handling ability- numbers that indicate this is a very beefy dome tweeter. The Exotic T35 lives up to its name by using an AlNiCo magnet in the motor system. AlNiCo is a metal alloy with the word deriving from Aluminum-Nickel-Cobalt. It is much more expensive than traditional iron ferrite magnets (mainly due to the difficulty in sourcing cobalt), but it isn’t as subject to induction effects or modulation distortion.

SM cone2

As its name indicates, the SuperMon Isobaric uses an isobaric woofer system. The SuperMon Mini also uses this system, so we will simply quote our description from that article:

Isobaric derives from Greek and means the quality of having equal pressure. For an isobaric loudspeaker design, the equal pressure refers to an air mass suspended in a chamber that is sandwiched by two active drivers which are moving in phase. So the SuperMon Isobaric’s other driver is hidden and is mounted behind the exposed woofer at a halfway-deep point in the enclosure, and the two drivers enclose a sealed pocket of air between them. The reason to use this design is to get deeper bass from a small cabinet. The effect of having a pocket of air with unchanging pressure between two drivers is that the system retains a lower resonant frequency in a smaller cabinet by doubling the moving mass yet halving the compliance. It is like using one driver with a heavier moving assembly but a larger and softer suspension; it will have a low resonant frequency although at the cost of efficiency. The efficiency cost is minimized with an isobaric system since it halves the impedance and sensitivity.

The SuperMon Isobaric doesn’t fully load the woofers using an isobaric equal pressure system. The exterior woofer crosses over to the tweeter at 2.7kHz, but the rear woofer is low-pass filtered at 130Hz. The rear woofer also loads a large port mounted on the back of the speaker so the outer pressure that it is subject to will not be the same as the pressure load on the front-mounted woofer. That means it is not entirely an isobaric system, but it does take advantage of isobaric loading in the range where it counts for most, in the lowest frequencies. The exterior bass driver is the AudioTechnology 6A77, a high-performance 6” driver made in Denmark. The interior driver is a German-made Eton bass driver. Both are premium drivers known with a good reputation among loudspeaker designers. Likewise, the crossover circuit is using premium components such as heavy-duty Mundorf capacitors and air-core inductors to ensure the highest tolerance filters with the least amount of losses.

SM rear4 

The SuperMon Isobarics come with their own stands, and the way that the speakers rest on the stands is interesting. The underside of the speakers and the top of the stands have three matching concave cavities. The speakers each come with three ball bearings that are seated in the concave recesses. The bearings are slightly larger than the combined depth of the recesses so they give the speakers a small rise above the stand. This gives the SuperMon Isobarics a stabilized wobble on the top of the stand. I assume the benefit is supposed to be some kind of damping for lateral movement caused by driver motion. I wouldn’t guess that this feature has any real audible benefits, but it is nonetheless a cool way to be mounted on top of a stand. One problem with it is that the clearance between stand and speaker does not allow enough room for fingers, so it can be a potential pinch point for someone lowering the speaker into the stand itself. My method for dealing with this was placing some thin paperback books flat on the stand, then lowering the speaker on the books, and then slide the books out so the speaker would be gradually lowered onto the ball bearings. The stand has three thick legs going to a base. The base rests on the ground on some massive spiked feet. The spikes rest on some hefty metal floor pads that have some inverse conical divots that the spikes can be slotted in. The overall stand itself is a heavy-duty contraption, and, at 62lbs., weighs more than many floor-standing speakers alone. That's a whopping 142lbs (80lbs speaker and 63lbs stand).

SM bottom 

SM Stand Top bearings 

With high-power handling drivers, a large enclosure, and a large port, the SuperMon Isobarics should be very capable in dynamic range for stand-mount loudspeakers. Given the premium components used at every turn, it should offer a very high-fidelity experience as well. Let’s now find out how all of this over-the-top design pans out in some listening sessions…

SM Stand feet 

Listening Sessions

In my 24’ by 13’ (approximately) listening room, I set up the speakers with a few feet of stand-off distances between the back wall and sidewall and equal distance between speakers and listening position. I gave the speakers a slight toe-in, and I found the treble a bit aggressive when facing my listening position directly. The listening distance from the speakers was about 9 feet. Processing was handled by a Marantz 7705, and amplification was handled by the Monoprice Monolith 5x200. Equalization was used but not automated room correction equalization. No subwoofers were used unless otherwise noted.

When I first set the SuperMon Isobarics up and started listening to them, I noticed they were relatively light on bass. In order to alleviate this, I set them up closer to the back and sidewalls, and that did help a bit, but to my ears, the bass still sounded thin. To be sure, they had bass, but it was not quite level matched with the rest of the frequency range. It’s possible that this was deliberate voicing, since my own room doesn’t get much low-frequency room gain, and these speakers are geared more for smaller rooms that are more common in Korean households which would get significantly more low-frequency room gain. So the natural sound of these speakers in my room sounded somewhat thin. With two beefy 6.5” drivers, I knew that they had the output capability for more bass, so I installed an equalizer on my computer, which is the source for most listening (Equalizer APO with the Peace interface extension). I boosted the range below 70Hz by 6dB and rolled the elevation off to 0dB at about 300Hz. This voicing made these speakers sound more natural and full to my ears.

I don’t normally use any equalization for loudspeakers under review, since I prefer to hear them in their most natural state. However, anyone who can afford the SuperMon Isobarics can also afford any number of tone control solutions for them, so it’s a problem that is easily remedied (the software solution I used costs nothing). It’s also possible that my own room acoustics just wasn’t playing nice with these speakers in particular. This being the case, I have opted to use an equalized response with these speakers for my listening. The response curve I use is very simple and only raises the bass, and it leaves other audio characteristics of the speaker alone.

Music Listening

By the time he passed away at age 48 in 2018, Johann Johannsson had already left a body of work that cemented his status as a major figure in contemporary orchestral music. His status wasn’t based on sheer volume of work but rather the unique quality of his music, thanks to albums such as “Drone Mass.” This album is performed by a choral octet and a string quartet accompanied by some electronic atmospherics arranged by Johannsson himself. The lyrics are taken from the Coptic Gospel of the Egyptians, and some of the hymns from that text have almost no consonants, a trait that can be used to place greater emphasis on the sound of the singers’ voices in themselves. This vital work of art was performed and recorded posthumously to Johannsson’s death, and it was given an appropriately excellent production courtesy of Deutsche Grammophone. I listened to it in a hi-res 24-bit/96kHz resolution stream from Qobuz.

The clarity of the singers was astonishing, both in tonality and imaging.

The first thing that impressed me was the definition of the voices. The clarity of the singers was astonishing, both in tonality and imaging. The positions of each of the singers were easy to discern, even though there were eight of them. The sound mix has a lot to do with that, of course, but the speakers need to be good enough to reveal that level of artistry, and I am happy to report that the SuperMon Isobarics was more than good enough. Similarly, the stringed instruments, which consisted of two violins, a viola, and a cello, were exquisitely reproduced and were given a lifelike presentation by the SuperMon Isobarics. While this recording was done in a sizable church (The Garrison Church in Copenhagen), the acoustics weren’t awash in reverb and helped to retain detail that might have been lost otherwise. Nonetheless, some acoustic elements of the environment could be heard through the speakers, and the sound of the performers was not completely dry. The electronics were organically mixed in with the performers and sounded like a natural part of the soundscape rather than an external element. “Drone Mass” is a somewhat challenging listen as an album, but thankfully the SuperMon Isobarics made the experience easier, through their superlative fidelity which made it more engaging than it might have been otherwise. 

Drone Mass  Gabi Hartmann

2023 saw an auspicious album debut of jazz vocalist Gabi Hartmann, a singer who exhibits tremendous talent as a lyricist as well as guitarist, and who holds a very promising future if her eponymous album is an indicator. She effortlessly mixes her native French with English, Portuguese, and a bit of Arabic into a melodic brew that world music fans and jazz lovers alike are sure to find intoxicating. The songs are all gentle, personal pieces consisting of Gabi’s reflections and lamentations. “Gabi Hartmann” is a wonderfully produced studio album that could sound good on any sound system but will really shine on a truly hi-fi setup. I found this marvelous album on Qobuz’s new releases spotlight and am glad that I did.

The SuperMon Isobarics projected a wide, enveloping soundstage...

The SuperMon Isobarics presented a strikingly realistic soundstage on “Gabi Hartmann.” Her voice was centered squarely between the two speakers, and various instruments flanked her at well-defined positions throughout the soundstage. In track 4, “Une errante sur la Terre,” the depth of imaging from the woodwinds and piano made my room sound larger than it actually was. Track 6, “L’amour incompris,” does the opposite, and the simplicity of Gabi and her guitar performing close to the microphone made my room into a much more intimate setting than it was, thanks to the imaging abilities of the SuperMon Isobarics. Tonally, everything sounded good, although anything with bass would have been highly influenced by the equalization curve that I implemented. Without the equalization, bass guitar and lower frequency percussion were present but fairly recessed. With equalization, the sound was full without becoming bloated on the low end, at least with the curve that I used. Gabi’s voice was recreated with nice articulation. It was finely detailed without being sharp or sibilant. In some of the tracks, it was as though she had been teleported into my room by the speakers. I quite enjoyed “Gabi Hartmann” on the SuperMon Isobarics. The album sounded terrific on these speakers, and I would strongly encourage SuperMon Isobaric owners to give it a try regardless if they like jazz or not.

December of 2022 saw the passing of iconic composer Angelo Badalamanti, a tremendous musical force in my life ever since I saw the premiere of “Twin Peaks” in 1989. The score for “Twin Peaks” has to be considered one of the greatest ever written for a television series, but Badalamenti has done so much more since then. Outside of his many collaborations with David Lynch, his body of work is an eclectic mixture of genre movie scores, collaborations with a wide range of other music artists, and scores for experimental short films. While it is not all that unexpected for an 85-year-old man to pass away, his death still came as a shock since he has been such a musical titan for so much of my own life. I thought it would be the perfect time to revisit some of his classic pieces as well as explore works that I had not yet heard, and a good vehicle to do that looked to be the compilation titled “Angelo Badalamenti: Music for Film and Television.” Like its title says, this is a collection of music that displays Badalamenti’s range for the scores he has written.  

The SuperMon Isobarics projected a wide, enveloping soundstage on this album, which is how I would have guessed it was meant to be heard. The venue sounded like a soundstage, so it didn’t have much symphonic hall reverb. That is how soundtrack music is usually engineered to sound; the listening room is supposed to be the performance space, whether that be a commercial theater or a living room. As was heard in other recordings, imaging was excellent, with the various lead instruments taking center stage, whether that be piano, vocal, guitar, or accordion, with other orchestral sections spanning the width of the soundstage, each with their own defined area. Solo instrumentalists and performers were rendered with vivid detail, and an example of this can be heard in track 7, “Who Will Take My Dreams Away, “ which features singing from Marianne Faithful whose delicate voice is realized with superb precision. Most of the music was made with sweeping, dramatic orchestrations, which is very much a Badalamenti trademark, and, on the SuperMon Isobarics, it was a lush and immersive sound.

Angelo Badalamenti  Overdriven

To see what the SuperMon Isobarics could do when driven hard, I threw in a compilation of electronic bass music titled “Overdriven.” The title was apt, since it was what I might very well do to these speakers in spite of their high cost. Anyone forking out 25 large for a pair of speakers has a right to know what their limits might be. The tracks in this album come from a range of genres within electronic bass music from faster-paced drum’n’bass to lower-velocity dubstep and dubfunk, but the one thing that they all have in common is heavy-duty beats and bass, perfect for pushing a sound system hard. In theory, the SuperMon Isobaric’s beefy woofers and port should be able to get along great with this kind of music, but the proof is in the listening.

This music definitely benefited from boosting the bass. In fact, I gave low bass an extra 4dB for this album, and the SuperMon Isobarics were game for such hot bass. Many other stand-mount speakers would have had trouble with high-volume playback plus a cumulative 10dB bass bump below 100Hz, but these speakers could handle it. The woofers were visibly moving, so I probably didn’t have much headroom left, but there was no doubt that these speakers could jam. Kick drums had a real thump, snares had a sharp snap, and cymbals sparkled with vivacity. The bassline could be nearly subwoofer-like. While a serious subwoofer would have had more oomph, these bookshelf speakers could be made to produce some honest-to-God meaty bass. While MonAcoustic probably didn’t envision that buyers would purchase these speakers for electronic bass music, they did sound good with it, albeit with an equalized low end. The SuperMon Isobarics made this album a fun experience, an impressive feat considering these are stand-mount speakers playing heavy-bass music without any help from subwoofers.

Movie Watching

One movie that I watched with the SuperMon Isobarics was the WW2 espionage adventure “Operation Mincemeat.” This 2021 Netflix production concerns a ruse to trick the Axis powers into believing that the imminent allied invasion of southern Europe was going to occur in Greece rather than Sicily. With an all-star cast and a big budget, this movie looked like a good opportunity to demonstrate the dialogue, music score, and period effects sound of a major Hollywood production. This movie is based on true events, and even though I had picked up a fair amount of trivia about World War II events over the years, I knew very little about this particular episode.

Thomas Newman’s pensive music score sounded terrific on the SuperMon Isobarics...

While the fullest expression of the sound mix for “Operation Mincemeat” would have been for a full surround sound system rather than a two-channel system, it still sounded terrific on the SuperMon Isobarics, and I didn’t miss the additional channels or subwoofer at all. These bookshelf speakers could dig fairly deep in bass, and I was not left wanting for a subwoofer, at least for this particular sound mix. They did need some prodding with equalization to apply their muscle, but they certainly had the muscle to do that heavy lifting when required. I never had any problems with dialogue intelligibility, and that is critically important in a dialogue-driven movie such as this. “Operation Mincemeat,” is not an action movie, but the effect sounds it did have were reproduced with enthusiasm.

The most notable aspect of the sound mix is undoubtedly Thomas Newman’s pensive music score. Thomas, son of renowned film music composer Alfred Newman, gives the music emotional subtlety as well as a propulsive drive. It sounded terrific on the SuperMon Isobarics, and it lent this talky movie a tension without which it might have come across as staid. In the end, I quite enjoyed the movie, and it compelled me to look up the real Operation Mincemeat to learn more about this historical episode.

operation mincemeat  bullet train

For a movie with a more bombastic sound mix, I watched “Bullet Train,” a 2022 big-budget movie with an all-star cast and a very over-the-top vibe. This movie concerns a semi-competent assassin (think the anti-John Wick, hilariously played by Brad Pitt) who decides to take a simple assignment to steal an aluminum attaché on a high-speed train in Japan. Complications arise when he discovers five other assassins onboard who each has also been given the assignment to take the briefcase. I had yet to see this colorful and comical action movie but now seemed to be a good time with loudspeakers seemingly as capable as the SuperMon Isobarics. It looked to be a good demonstration of what a sound system could do with lots of action scenes.

“Bullet Train” proved to be a wild ride, visually, sonically, and narratively. The sound mix was densely packed with action, music, and dialogue from beginning to end. The action was primarily hand-to-hand combat, and the SuperMon Isobarics made these sequences lively and dynamic. Music was a mixture of orchestral and classic pop music, and it shined on the SuperMon Isobarics. The Bee Gee’s “Staying Alive” was the anthem for this movie, and it played in English, Spanish, and Japanese versions at moments throughout the film. Englebert Humperdinck’s “I’m Forever Blowing Bubbles” also makes an appearance with perfect comic timing. Dominic Lewis supplies the original music to the movie, and it is an appropriate combination of kitsch and kinetic energy for the action. The SuperMon Isobarics delivered the score with as much enunciation as could be had underneath all of the dialogue and effects sounds. Dialogue intelligibility was never a problem on the SuperMon Isobarics, even with the cast affecting a variety of accents from British Cockney, bland American, Japanese, Russian, and Mexican. The dialogue was delivered with a screwball comedy fast pace, but I could easily follow everything that was said and did not miss any of the many quips or F-bombs. I liked “Bullet Train,” and the SuperMon Isobarics ended up being a fine sound system to hear this bombastic movie. I am sure that most potential buyers will see the SuperMon Isobarics as speakers for a two-channel music system, but I can report that they can be used to enjoy an extravagant action movie as well if needed.

Mon Acoustic SuperMon Isobaric Measurements and Conclusion

The SuperMon Isobaric was measured at a height of 4 feet at a 1-meter distance from the microphone, and the measurements were gated at a 5-millisecond delay. In this time window, some resolution is lost below 600 Hz and accuracy is completely lost below 300 Hz. Measurements have been smoothed at a 1/12 octave resolution.

SuperMon Iso 3D waterfall response

SuperMon Iso 2D waterfall response

The above graphs depict the speaker’s lateral responses out to 90 degrees in five-degree increments. More information about how to interpret these graphs can be read in this article: Understanding Loudspeaker Review Measurements Part II. The overall response shown here is not bad but there are some oddities. Firstly, the treble at and around the on-axis angle seems to be a bit hot above 5kHz. By the 20-degree off-axis angle, it is level-matched with the lower frequency range, but as we move inward toward the on-axis angle it does become a bit elevated, perhaps 3dB hotter than the average below that range. I didn’t notice an especially hot treble in my listening, but I didn’t listen to the speakers at an on-axis angle. The mid-range from 500Hz to 3kHz is generally well-controlled, and that is where the heart of most music is, so it was important that the SuperMon Isobaric got that right. There seems to be a slight lowering of amplitude below 500Hz that may have contributed to the weakness in bass that I heard, at least before I equalized them, but the main explanation for that will follow when we examine the groundplane measurement of the low frequencies.

SuperMon Iso Polar map 

The above polar map graphs show the same information that the preceding graphs do but depict it in a way that can offer new insight regarding these speakers’ behavior. Instead of using individual raised lines to illustrate amplitude, these polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is they can let us see broader trends of the speaker’s behavior more easily. For more information about the meaning of these graphs, we again refer the reader to Understanding Loudspeaker Review Measurements Part II.

The SuperMon Isobaric’s front radiation pattern is a bit ragged but generally is fine with no major bursts of energy or nulls at off-axis angles. One unusual feature is that we can see a small dip on and around the on-axis response just above the crossover frequency. This suggests that there is not perfect phase alignment between the tweeter and woofer, at least on-axis with the tweeter. In that same region, there is also some extra off-axis energy. This is occurring at the tweeter level, and this attribute would certainly change with height, so a higher or lower angle might correct this minor error. Something else interesting to note is that the tweeter manages to keep a somewhat wide dispersion out to a relatively high frequency. At 1.5”, the SEAS Exotic is a large dome tweeter. Typically these kinds of tweeters will begin to constrict dispersion at relatively low frequencies. This tweeter does constrict its dispersion somewhat above 5kHz, but it doesn’t get really narrow until above 10kHz. The listener could be listening at a 30-degree angle and still be met with high treble. It’s would be an unusually broad angle of high-frequency energy for a large dome, except that it seems as if the tweeter had been voiced a bit hot to achieve this effect. 

SM iso response per angle graph 

The above measurements compare the on-axis response of the SuperMon Isobaric to a couple of off-axis measurements. We are doing this to illustrate the optimum toe-in angles for those users who are looking for the most neutral sound. As we saw in the polar map, the on-axis angle has a null around the crossover frequency indicating a phase conflict, at least for the point in space where we measured. Moving off-axis smoothes out the irregularities from the on-axis angle and can yield a fairly neutral response. From 20 to 30 degrees, the response becomes relatively flat, which can be seen on the 25-degree curve. Moving even further off-axis, we can see the tweeter’s dispersion narrow, and the higher frequencies become rolled off. Listeners are likely to end up in a neutral response angle if they position the speakers to straight face forward in a parallel aim with no-toe-in angling. I would recommend users start with this type of placement in setting these speakers up.

SuperMon Iso low-frequency response 

The above graphs show the SuperMon Isobaric’s low-frequency responses that I captured using groundplane measurements (where the speaker and microphone are on the ground in a wide-open area). There are two curves here: the purple curve is the speaker measured with the microphone 2 meters in front of it, and the brown curve is measured with the microphone 2 meters behind the speaker. One feature of the front-measured response that leaps out is a high-Q dip just above 100Hz. While that may have contributed to the lessened bass response that I heard, what I heard was not quite a null, but rather an overall attenuation of low bass. This null occurs in front of and on the sides of the speaker, and I would guess that the isobaric loading design of the speakers creates some kind of sharp cardioid null. Rear-generated output by the port would help to fill it in somewhat in-room. The cause of the reduced bass is better explained by the overall lowered output below that null. Everything below 100Hz looks to be at least 3dB softer than the range above the null. Something else to note is that this speaker is tuned quite deeply for a stand-mount speaker. The response extends well below 40Hz before it even begins to roll off. That is more like the bass extension that we typically see from floor-standing speakers, not stand-mount speakers.

SM Impedance 

The above graph shows the electrical behavior of the SuperMon Isobaric. These are unusual impedance curves, to say the least, but they aren’t bad or especially problematic. The only spot of concern is 100Hz, which dips down to 4 ohms along with a very steep phase angle. That is going to be rough for a cheap amp, but no one who buys these $25k speakers is going to pair them up with a cheap amp, so there isn’t anything to be concerned about here. One unusual feature we see is evidence of two resonances in the low frequencies; one for the port tuning at 35 Hz, and another at 100Hz, which is presumably related to the isobaric design. The tweeter’s impedance seems relatively high for a dome tweeter, and I think that is due to some resistor padding in the crossover circuit on the SEAS Exotic. I measured the sensitivity to be 88.5dB for 2.83v at 1 meter, and that is pretty close to the manufacturer’s spec of 89db. This is about the sensitivity I would have expected of a large stand-mount speaker, so no surprises there. Any decent amp should be able to make these speakers get loud. However, I would recommend a somewhat beefy amp for those who want to give the bass more muscle via equalization, which I think will be a lot of owners.


We will wrap this review up by briefly going over the strengths and weaknesses of the product under review. As always, we will start with the weaknesses, since I am the kind of person who likes to get the bad news out of the way first. The SuperMon Isobarics do have their flaws. The most prominent flaw, one I have already discussed at length, is that the entire lower bass frequencies have been significantly attenuated. This can be remedied by a simple equalization curve, but I would have hoped that loudspeakers as expensive as these wouldn’t need equalization to make sub-100Hz bass levels match up with the higher frequencies. I think that using an isobaric design has likely caused more problems than it has solved in this instance.

 SM pair11

SM Mon badgeOn top of the missing bass, the frequency response at and around the on-axis angle is a bit rough in treble frequencies. Listening to the speaker head-on can be piercing with certain content at times due to the prominent treble. This is easily solvable by listening with only a mild to no toe-in angle where the response becomes fairly neutral at the listening position. Nonetheless, I have had plenty of less expensive speakers that didn’t have this problem. I believe the root cause is that if the tweeter were level-matched with the woofer at an on-axis angle, its off-axis energy would be fairly low, and it would end up with a mismatched dispersion with respect to the woofer. So Mon Acoustic chose to have better off-axis behavior at the cost of a smooth on-axis response. While this issue is solvable for a single listening position by merely repositioning the speaker to an angle of response that suits the listener’s ears better, it is not easily addressed with equalization for a broader listening area.

With my complaints out of the way, let’s now get into compliments. With EQ’d bass and correct placement, the SuperMon Isobarics can sound terrific. They do take some work to get there, but they can certainly get there. The effort involved in attaining a great sound from these speakers will inevitably be a turn-off for some people, but there are those audiophiles for whom that would actually be a draw. The soundstage and imaging are excellent. The speakers can have a good dynamic range if given enough power to compensate for bass equalization. The midrange performance is generally good out of the box on and off-axis, and, as we noted before, that is where most audio content lie. I enjoyed listening to them once I had them set up optimally for my tastes.

Outside of their sound, the build quality of the SuperMon Isobarics is nearly as good as can be had. It would be difficult to make a more inert, dense enclosure. Perhaps a thick marbled stone would be even more enduring and massive? Or maybe a denser metal like titanium? But to have a large stand-mount loudspeaker built out of aluminum is pretty over-the-top. The Isobarics feel like they look too. Picking one up is akin to lifting a boulder. At 80 lbs. each, users will need to be careful when handling these speakers. As we said about the SuperMon Minis, if taken care of, these speakers could potentially last a very long time. The soft components are going to be the limiting factor in the lifetime of these speakers, but if they are kept in a climate-controlled environment without experiencing too many temperature extremes or humidity cycles, then these speakers could last many decades.

Their appearance is pretty stunning- as any fully metal loudspeaker would be. Owners looking for a speaker that looks high-end without being over-stylized have a great choice in the SuperMon Isobarics. These are not speakers that will meekly blend in with the decor; these are speakers for audio lovers to proudly display. Visitors will notice them, and they will likely be the subject of conversation.

SM pair

SM labelWhile getting to know the SuperMon Isobarics proved to be a bit frustrating at first, once I did get a grip on them, I could elicit a great sound and had a very enjoyable experience overall. But to focus on the sound alone is to partly miss the point of loudspeakers like these. These are not just about the end result but how that result is arrived at. Rolex watches are not desired for how well they track time, but for the mechanical engineering used to accomplish that objective without resorting to quartz crystals or other digital means. Similarly, the use of aluminum as an enclosure material and isobaric loading of the woofer plays a role in the desirability of these speakers, even if those design aspects don’t necessarily make them more accurate for audio reproduction (although I have no doubt that Mon Acoustic does believe that those aspects assist in superior sound quality).

Some audio enthusiasts just view audio equipment as a means to an end, but others celebrate the method by which that end is achieved. Most readers knew which side of that line they stood on before they started to read this review, so my guess is that reading this review won’t do a lot to change the minds of those who already knew about these speakers. As for myself, I can appreciate both perspectives, but I do lean more toward the function-over-form, so I can’t say that the SuperMon Isobarics would be my first choice if I had $25k to spend on a speaker pair. For my own tastes, too much of its design budget was allocated to aspects that don’t contribute to sound reproduction (again, I am sure that Mon Acoustic would disagree on this point). I can say that I could easily live with a pair if someone just gave some to me and that the past few months living with them have been a delight.  

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

  • StarStarStarStarStar — Excellent
  • StarStarStarStar — Very Good
  • StarStarStar — Good
  • StarStar — Fair
  • Star — Poor
Build QualityStarStarStarStarStar
Treble ExtensionStarStarStarStar
Treble SmoothnessStarStarStar
Midrange AccuracyStarStarStarStar
Bass ExtensionStarStarStarStar
Bass AccuracyStarStarStar
Dynamic RangeStarStarStarStar
Fit and FinishStarStarStarStarStar
About the author:

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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