Monoprice Monolith AMT Headphone: Going after the big boys, does the AMT merit a mention? For a good part, yes.
Between Will and me, we seem to be going in a nice circuitous route with regard to headphone reviews. We had several from HiFiMan in house at the same time split evenly between us. We now have a good representation from Monoprice as well. Since I knew what Will had already, I decided to see what might fill in a hole, which was lacking. Since I absolutely loved the HEDDphone from HEDD, rating it as one of my top five headphones ever (even with the fit), I found it a natural choice to go with the Monolith AMT, which fits into Monoprice’s Monolith line as the top representation for headphones. To many, the Monolith line represents the pinnacle of Monoprice’s offerings, much like a Lexus is to Toyota. A fair assessment, and to me the AMT fits naturally into that niche. With a now raised price of $999, the price difference between the HEDDphone shrinks a bit as well.
Specs:
| P/N | 43235 |
| Type | Open back headphones |
| Transducer Type | Air Motion Transformer (AMT) |
| Magnet Type | High‑grade N52 Neodymium |
| Maximum Power Handling | 10 watts for 200ms |
| Frequency Response | 15Hz ~ 40kHz |
| Total Harmonic Distortion | <0.1% |
| Nominal Impedance | 32 ohms |
| Sensitivity | 90dB/mW |
| Headphones Cable Connectors | Mini 4‑pin XLR |
| Audio Plug Connector | 1/4″ |
| Weight (without cable) | 24.0 oz. (630g) |
| Included Accessories | 6‑foot cable and 1/4″ to 3.5mm adapter |
For those of you not familiar with AMT (Air Motion Transfer) technology, it is a way of maximizing the surface area of the respective driver technology, much like crinkling a piece of paper, increases the surface area. Mind you, AMT is done with much more precision and thought of how the sound waves react (using a pleated driver design) to the refraction and reflection of sound (air motion) off the surface. From my review of the HEDDphone: AMT is an electrodynamic transducer that allows air to move significantly faster than a common voice coil, planar or electrostatic system. The faster the driver can react to the electric signal waves; the better sound reproduction will be due to a more accurate (faster) representation. Combined with the magnets present in the driver, air is forced into, then out of every fold, accelerating the air significantly. Thus, the faster the air reacts to the electronic signals, the closer it is to the representation of the source signal. Yielding faster transient responses, along with increased precision, clarity and a greater treble extension (without harshness and excellent bass characteristics as well) will give a more realistic audio reproduction in sound.
I strongly suggest you read about it here, because it really is a fascinating technology, essentially saying, “all other driver technology is wrong; we are right;” sort of stuff. I like the resulting sound from the HEDDphone, and as such thought a good comparison would be a worthy endeavor. A downfall of this technology is the need for power. Smartphones need not apply for best sound quality and some DAP’s struggle a bit to fully utilize the AMT technology. Used across many platforms here, I did find some worked better than others.
More Detail:
The Monoprice Monolith AMT retails for $999, so it is not cheap by any means. And in that price bracket, the competition is as fierce as it gets. From models such as the HiFiMan Edition XS (significantly less) to the Arya (now $1300, so closer) to any of several Sennheiser models; you have many choices. In other words, it will take something rich and worth it to stand out.
The AMT (93mm x 63mm driver w/ N52 Neodymium high grade magnets) is a large over ear open back headphone. There is no getting around that. The pads engulf your ears in opulence due to the thick (THICK!) leather shaped in a rectangular fashion. Pad pressure was minimalized as a result of the thick pads and larger size. Quality of construction was good as well. I will note that one of the min-xlr ports was hard to attach and take off, but it did not alter the sound. The cable is thick, and on the heavier size, but laid well. Covered in fabric, it is a quality cable with a tightly woven fabric cover (plastic threaded). Coming with a 6.35mm to 3.5mm adapter allows you to use it on any source, which has either of those as headphone jacks.
The headband is where I ran into trouble. Normally in heavy headphones, there is a double band; one for actual contact and the other to lend support in the whole set up. On the AMT though, there is a single, albeit thickly padded, curved headband. At 24 ounces, the AMT is not light by any stretch, and that weight does not allow much room to flex the headband. It does flex, but due to the singular nature, does not allow for much clamp adjusting pressure. It is also a very short headband, and when combined with the large drive size, gives very little adjustment. I had to run the band all the way in the closed position to get the best fit. Those with smaller heads will have issues getting the proper fit. That said, the ear cup is of such a large size that it might work for most.
Shaped similarly to the HEDDphone, the AMT has interchangeable pads and is built of good quality materials. The plastic is matte finished to minimize glare, and the metal parts accent the overall look. You can of course look into the outside of the cup and see the whole driver unit, which in its bronzish-gold color accents the overall appeal nicely. Build solidly, with good materials, the AMT can fit into the price point so far based upon quality alone.
The Sound
As stated above, the AMT will not shine is a Smartphone atmosphere. There simply isn’t enough power. Switching to the Kann Max we have on hand, I found that running the Max AMP in “Super” mode, and with a volume of 80+ (out of 150), I could get good response with Dave Matthews Dodo & Gravedigger. To really run the AMT, I ran the volume to 120/150, which was plenty loud enough to me. Settling on 100, Up And Away came across with vivid treble extension without becoming tiresome and a bass reach, which was deep and with a solid fast thump. There is no denying the speed of response in the sound signature, which can often lead to a sound, which is too analytical. One of the best attributes of the HEDD was its smooth and slightly warm tilt, which added to the speed of response, instead of detracting like one would think. The same can be mostly said in the AMT as well. I was able to discern placing of the instruments well, and with a vivid response resulting from the volume level and the AMT technology. While not as detailed and lacking the clarity of say the HiFiMan Arya, the sound was nonetheless quite pleasant.
Vocals came across with a bit of alacrity, but to me they hit higher inside my head than most headphones I have heard of late. This led to an almost disjointed result between the music and singer, but not quite. Moving to Coldplay’s Paradise, I found the resulting mix of many instruments in the string department and digital worked well, and the whole of the element seemed lifted like the vocals mentioned above. Adjusting fit, for a more parallel interface between the side of my head and the ear cups lowered the signature to a more central location. This may come down to fit as an issue. Regardless, the sound was still smooth with very good character. Not once did the sound feel like it lagged behind the music. Speed can often times lead to a thinning of sound, and what some call an analytical sound, or even more neutral. Desired by some, I find it lacking in depth and character. Here though, on the AMT that rich sound permeated throughout, working in concert with the speed of signal response that AMT drivers are known for.
Switching to the excellent Cambridge Audio Alva Duo (has its own headphone amplifier built in) through my Linn Axis (Basik LX V w/ Signet cartridge), Art Blakey’s Moanin’ sounded thick and rich. I did have to run the volume all the way up, but the sound came across as if I was in the jazz club while the song was playing. Switching to my Arcam AVR300, I had to run the headphone volume up to 84/99 for any quality sound feedback. But it was worth it. The combination of the Linn paired with the Arcam and AMT gave me that smooth jazz touch needed to enjoy the sound with plenty of tight low end.
Across three sources, the AMT played well, but some of course functioned better. For sheer volume (with a quality sound) the Kann Max was the choice here. For “just getting by,” the iPhone 13 Pro Max worked, but was not nearly enough to allow the full AMT experience. And the album experience? To me, this was my favorite, even if it did not reach the volume levels necessary to “properly” drive the AMT. Deep reaching bass came through the Axis, and the jazz notes presented me with an experience that showed the qualities the AMT had on offer. Under proper direction, the AMT can play music very well. Some will not have the necessities to try many sources to fit properly, and that to me is one of the downfalls of the AMT. Properly driven, it sounds quite nice. Driven by less than that needed to allow the AMT to breathe shows its limitations. An audition with your sources is thus of necessity to me.
finite:
The Monoprice Monolith AMT is not cheap. You are moving into the realm of many other top-notch headphones at this cost, and even some much better headphones can be had near this price secondhand (properly cared for, I hope). And therein lies the dichotomy of the AMT. It can sound very nice, with the proper source, but driven by less than it deserves, and it falls short. The technology is a grand idea, as witnessed by the model copied. But whether the AMT did enough to warrant your hard earned will have to be a decision taken after a good listen. It might just fit the bill.
The Monoprice Monolith AMT can be purchased here (on sale for $749): AMT
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