MartinLogan announced the USR51 on 7 October, via a press release that calls it a stealth AV receiver. It is a 5.1-channel networked receiver, 50 watts per channel into 8 ohms or 92 into 4, with Anthem Room Correction, AirPlay, Google Cast, Spotify Connect and Bluetooth, a VESA bracket in the box so it can hang behind the TV, and a price of $1,299.99. The release says it was built "in partnership with Anthem". That is one way to put it. Anthem has sold the MRX SLM at $1,299.99 since well before this week, and every number MartinLogan publishes for the USR51 is the MRX SLM’s number. The two brands share an owner, Paradigm Electronics of Mississauga. I added the USR51 to the database this week as our first MartinLogan receiver, and this post is about what the badge changes, which is less than the press release suggests, and about where a receiver this thin lands among the 57 we already held.
MartinLogan USR51 mounted in an in-wall media box behind a television
Quick facts
- $1,299.99, the same as the Anthem MRX SLM. Five channels, 50 W into 8 ohms, 92 W into 4 ohms, ARC Genesis. MartinLogan’s own page says "in partnership with Anthem"; the rear panel says "Powered by Anthem".
- The rear panels match connector for connector. Phoenix speaker block, sub out, 3.5 mm analog in, HDMI out with eARC, one HDMI in, optical, USB for updates, LAN, two Wi-Fi antennas, IR extender, and a 325 W maximum power draw printed on both.
- One HDMI input. Every other receiver we hold has four to seven. The USR51 expects the TV to do the switching and send sound back over eARC.
- The thinnest receivers we hold, by a distance. The MRX SLM is 38 mm tall and 3 kg. The next thinnest of 57 is the Marantz NR1510 at 105 mm. MartinLogan has not published the USR51’s dimensions yet.
- Built for MartinLogan’s thin speakers. The Motion SLM series, the Motion 2i to 8i, and its in-walls, all of which we hold.
What MartinLogan publishes, and what Anthem published
Here is the whole comparison, from the two makers’ own pages. The MRX SLM row is what we already held, from Anthem and Crutchfield; the USR51 column is from martinlogan.com and the press release.
| FEATURE and SPECS COMPARISON | |  |  |
| Model | MartinLogan USR51 | Anthem MRX SLM |
| Type | Home Theater Receiver | Home Theater Receiver |
| Amplifier Class | - | D |
| Power into 8 ohms | 50 watts | 50 watts |
| Power into 4 ohms | 92 watts | 92 watts |
| Minimum Impedance | 4 ohms | 4 ohms |
| Built-in DAC | | - |
| Analog Inputs | 1 | 1 |
| Phono Input | | |
| Optical Digital Inputs | 1 | 1 |
| Coaxial Digital Inputs | No | No |
| USB Input | No | No |
| HDMI Input | 1 | 1 |
| HDMI ARC | eARC | - |
| Preamp Outputs | No | No |
| Subwoofer Output | 1 | 1 |
| Headphone Output | No | - |
| Bluetooth | Yes | - |
| Wi-Fi | Yes | - |
| Chromecast built-in | | - |
| Room Correction System | ARC Genesis | ARC Genesis |
| Handheld Remote | | - |
| Height | - | 38.1mm |
| Width | - | 280.9mm |
| Depth | - | 328.7mm |
| Weight | - | 2.99kg |
| MSRP | 1300 USD | 1300 USD |
| Check Current Price | Amazon, B&H Photo | Amazon, B&H Photo |
| MartinLogan USR51 | Anthem MRX SLM |
|---|
| Price | $1,299.99 | $1,299.99 |
| Channels | 5, plus a sub output | 5, plus a sub output |
| Power, 8 ohms | 50 W per channel | 50 W per channel, two driven |
| Power, 4 ohms | 92 W per channel | 92 W per channel |
| Room correction | ARC Genesis | ARC Genesis |
| HDMI | 1 in, 1 out with eARC | 1 in, 1 out with eARC, HDMI 2.0b |
| Other inputs | Optical, 3.5 mm analog | Optical, 3.5 mm analog |
| Streaming | AirPlay, Google Cast, Spotify Connect, Bluetooth | AirPlay, Google Cast, Spotify Connect, Bluetooth |
| Speaker terminals | Toolless Phoenix block | Phoenix block |
| On-screen display | None, web UI and app | None, web UI and app |
| Mounting | VESA bracket included, 1U rack kit optional | Bracket included, rack kit optional |
| Size | Not published | 38.1 x 280.9 x 328.7 mm, 2.99 kg |
| Maximum draw | 325 W | 325 W |
| Made in | China | China |
The one row that differs is the size, and only because MartinLogan has not printed it. The press release says the USR51 fits 1U of rack space with the optional kit; the MRX SLM is 1.5 inches tall, which is 1U less a hair. I have left the USR51 dimensions empty in the database rather than copy Anthem’s across, and I will fill them when MartinLogan or a dealer prints them.
The rear panels of the MartinLogan USR51 and the Anthem MRX SLM with the same connectors in the same order
The rear panels are the clearest evidence. Same connectors, same order, same labels, same "Made in China", same 325 W figure on the mains socket. The USR51 adds "Powered by Anthem" and "Designed and Engineered for MartinLogan Ltd." in the corner where the SLM says "Designed and Engineered by Anthem Electronics, Inc." MartinLogan and Anthem are both Paradigm Electronics brands, so this is not a licensing deal between strangers. It is one receiver sold through two dealer networks, with a front plate that matches the speakers the MartinLogan dealer is already selling.
Why the badge matters anyway
If it is the same unit, why is this worth a post? Because of who sells it. The USR51 is named on its own page as the partner for MartinLogan’s Motion SLM, Motion SLM XL and Motion SLM X3 on-walls, the compact Motion 2i, Motion 4i, Motion 6i and Motion 8i, and the brand’s in-wall and in-ceiling range. We hold all of those, and they explain the amplifier. The SLM X3 is a 1.22 m wide on-wall bar, 51 mm deep, 93 dB sensitive, 4 ohms, rated for 20 to 140 W, at $1,300. The Motion SLM is 94 dB and 4 ohms in a cabinet 48 mm deep. Into those, 92 W per channel at 4 ohms is the right size of amplifier, and 50 W into an 8 ohm speaker at 86 dB, which is what the Motion 2i is, is not. The USR51 is a receiver for thin, efficient speakers on or in the wall, and MartinLogan sells a whole range of exactly that.
MartinLogan USR51 front panel in a cabinet shelf
It also fixes a selling problem. A customer buying a pair of SLM X3s and a Motion 8i centre from a MartinLogan dealer needs five channels of amplification that disappear as well as the speakers do. Until now the answer was an Anthem, which the same dealer may or may not carry. Now it is a MartinLogan, in the same catalogue, with the same name on the front.
Where a 38 mm receiver lands among the 57 we hold
Before this week we held 57 home theater receivers from 11 brands, Denon and Marantz to McIntosh, $400 to $9,500. Their average height is 161 mm, their average weight 13.2 kg, and the average box takes up 29.3 litres. The MRX SLM is 38 mm, 3 kg and 3.5 litres, which is an eighth of the average volume. The next thinnest receiver we hold is the Marantz NR1510 at 105 mm, then the Marantz Cinema 70s at 106 and the JBL MA310 at 110. Those are the slimline receivers of the mainstream brands, and the Anthem is a third of their height and a third of their weight. Nothing else in the table is in the same class physically, and the USR51 is the same box.
MartinLogan USR51 on a cabinet under a wall-mounted TV and soundbar
The price is a different story. Ten of the 57 are five-channel receivers, and nine of those cost between $400 and $700: the Denon AVR-S670H at $649 gives you 75 W x 5, six HDMI inputs and Audyssey; the Yamaha RX-V4A at $650 gives you 80 W x 5, four inputs and YPAO. The MRX SLM and now the USR51 ask $1,300 for 50 W x 5 and one input. Per channel, per watt, that is $26 against the Denon’s $8.65. What the extra $650 buys is 120 mm of height, 5 kg, a bracket, and Anthem’s room correction, which is the part of the package an installer will actually argue for. Whether that trade is worth it depends entirely on whether the receiver has to be invisible. If it can sit on a shelf, it is a bad deal. If it has to hang behind a TV, there is nothing else in our database that will.
Four MartinLogan USR51 receivers stacked in a rack, one unit per 1U with the optional rack kit
Readers here open the MRX SLM most often against the Denon AVR-X1800H, a $849 seven-channel receiver with six HDMI inputs and 80 W, which is the comparison that shows the size premium most plainly. Across all 57 the most-opened pairs are the Denon AVR-X3900H against the Denon AVR-X4800H and the Marantz Cinema 70s against its Series 2, both of which are "do I pay for the newer one" questions. The USR51 against the MRX SLM is the first pair we hold where the honest answer is that there is nothing to pay for either way.
The weak points
One HDMI input. The whole design rests on the TV being the switch: your sources plug into the TV, and the TV sends the sound back over eARC. That works for streaming boxes and consoles on a 2020-or-later TV with eARC. It does not work for a disc player you want to feed directly, or a TV that only has ARC, where you lose lossless Dolby TrueHD and DTS-HD. If you have more than one source you do not trust the TV to pass through properly, this is the wrong receiver.
50 watts, two channels driven. Anthem rates the 50 W with two channels running. MartinLogan prints the same number without the footnote. Five channels at once will deliver less, and the chassis has no room for a bigger supply. For a bedroom or a den with 90 dB speakers that is fine. For a 40 square metre living room with 86 dB bookshelves it is not, and no MartinLogan badge changes the physics.
The Phoenix connector. Speaker wires go into a screw-down terminal block, not binding posts. Fast for an installer, and it rules out thick cable, spade lugs and banana plugs. If you own a set of expensive speaker cables, they will not fit.
MartinLogan USR51 rear panel with the Phoenix speaker block sub out analog in HDMI out with eARC HDMI in optical LAN and IR extender
No on-screen display. Setup, ARC and every setting live in a web page and the Anthem Remote app. The receiver puts nothing on the TV, by design. Some people will call that clean; some will find it exhausting to adjust a crossover from a phone.
It is the same price for the same thing. MartinLogan is not undercutting Anthem by a dollar, and it is not adding anything. If your dealer carries both, buy whichever is in stock. If a MartinLogan dealer quotes you more than $1,299.99 for the USR51 "because it is the MartinLogan version", walk out.
Anthem MRX SLM front panel with the Dolby Vision Dolby Atmos DTS:X HDMI and ARC badges
No dimensions yet. MartinLogan’s page and the press release give the chassis no height, width, depth or weight. Everything I have said about size is Anthem’s figure for what appears to be the same box. I will update the row when MartinLogan publishes its own.
Who does this rule out? Anyone with several HDMI sources and an older TV, anyone with a large room or inefficient 8 ohm speakers, and anyone who was hoping the MartinLogan name meant MartinLogan electronics inside.
The bottom line
- You own or want MartinLogan on-walls or in-walls: the USR51 is the matching amplifier, and the Motion SLM X3 at $1,300 a pair, 93 dB and 4 ohms, is exactly the speaker it was sized for.
- You want the slim Anthem and do not care about the badge: the MRX SLM, same money, and Anthem’s dealers have had it longer.
- You have a shelf and five speakers: the Denon AVR-S670H at $649 or the Yamaha RX-V4A at $650 give you more power and more inputs for half the price, in a box four times as tall.
- You need more than five channels in a thin box: nothing we hold does that. The Marantz Cinema 70s at 106 mm is the thinnest seven-channel receiver in the database.
The USR51 is on the MartinLogan receivers page, and you can compare it against the MRX SLM or any of the other 57 receivers we hold.
Have you hidden a receiver behind a TV, and did eARC do the switching well enough that you stopped missing the HDMI inputs?