NHT 02-ARC Outdoor Speaker Review

Let’s face it, everyone likes great sound once they are exposed to it.  It’s not always easy to get great sound outside of the home theater environment.  Most outdoor speakers we’ve seen leave us wanting in the fidelity department.  How do the new NHT 02-ARC Outdoor Speakers perform?  You’re gonna have to watch our video review and check out our measurements to get the answer.

NHT 02-ARC Outdoor Speaker Video Review

Design Overview

This is NHT’s third generation of outdoor speakers.  The market is mostly flooded with indoor/outdoor speakers that are made to be weather resistant but not necessarily tuned ideally for an outdoor environment.  Most outdoor speakers tend to offer anemic bass response since they can’t rely on natural room gain that an indoor environment ordinarily would provide. NHT claims this is not the case with their new 02-ARC Outdoor Speakers.  NHT designed the bass response to be very balanced outdoors, enough so that adding a subwoofer is an option, not a requirement.  As an aside, NHT claims the 02-ARC speakers also work very well in large, high-ceiling rooms (restaurants, health clubs) for background music.  They cannot however be used with a microphone in a PA system; that’s not the design intent.

This latest design uses a material they call “Anti-Resonance Casting”. The material is actually bulk molding compound (BMC), extremely rigid, acoustically dead, material.  It’s used for airplane and truck parts primarily.  The cabinet walls are 7mm thick with nine, 3mm ribs that run continuously – side, bottom, side.  3 short ribs top and bottom.  Front baffle has one large rib running side-to-side above the woofer and 6 smaller ribs around the perimeter.  Let me tell you, this is definitely the heaviest and most rigid outdoor speaker I’ve ever tested in this size.  Most outdoor speakers utilize 5mm thick walls with far less support bracing.

NHT added some neo magnets so that the grille adheres tightly to the front baffle to keep little creatures from building homes in your tweeters or prying kids from playing Kung Fu Panda.  The cabinet is a completely sealed design, also called acoustic suspension

The 6.5” mid-bass polypropylene driver and 1” polyester fabric dome with urethane coating are moisture resistant.  Both drivers utilize conventional ferrite magnets.  The 6.5” driver has a stamped frame with an extended pole piece for higher excursion capabilities.  Unlike some competitive outdoor speaker models that simply slap a resister and capacitor on the tweeter and call that a crossover, NHT actually employed a real network with a 2^nd order electrical (4^th order acoustical) response.  All parts are 5% tolerance including the laminated core inductors, non-polarized electrolytic caps, and cement resistors.

The NHT 02-ARC outdoor speakers are available in both Black and White finish options.  The paint NHT chose has had 1000s of hours of environmental testing and is said to be UV resistant.  Our review samples came in the black finish. 

Installation

The 02-ARC speakers are voiced for near-boundary installations. So for best results outdoors, you’ll want to mount them on a wall surface.  We did just that in our Sun Room which serves as a workout area and play room.  The 02-ARC’s were mounted on the wall above our glass sliding door.

We used tapcons to mount the “C-Clamp” brackets onto the stucco block wall.  We did this by first pre-drilling the holes using a concrete bit and then using hexagon head tapcons.  It’s important to line up the screws with the narrow hole area of the bracket. This will ensure the head doesn’t fall through the bracket once tightened down to prevent massive head trauma to any unfortunate soul in the gravity’s path of the speaker that was installed improperly. 

Getting the speaker to tighten down on the bracket is a bit tricky mostly because it’s challenging to line up the screw holes.  I found it easiest to line up the bottom of the speaker first and slightly tighten down the mounting screw before doing the top one.   

Before fully tightening down the mounting screws, you will want to properly position the speaker.  The bracket allows pretty good horizontal adjustments but absolutely NO vertical adjustment flexibility at all.  This was a bit disappointing as we’ve seen more sophisticated mounting brackets on other systems.  My advice is to place the speaker as low as possible but high enough so there is absolutely NO chance that Kareem Abdul-Jabbar can bump his head if he ever plans on paying you a visit. A workaround to getting a slight tilt downward would be to wedge an angled wooden mounting plate underneath the top of the bracket while screwing it into the wall with a longer tapcon.

NHT 02-ARC Installed in Sun Room

NHT 02-ARC Outdoor Speaker Sound Quality Tests

I connected the 02-ARC speakers to my Emotiva MPS-1 7CH amplifier that is used for multi-zone audio around the Audioholics Showcase Home which is directly connected to a Yamaha RX-Z7 AV Receiver.  The source was my Yamaha MusicCAST MCX-2000 and cables were the 10AWG from Bluejeans.

I flipped around the music server to a variety of music to get a true understanding of the versatility of the NHT speakers.  I started out with Diana Krall “Popsicle Toes” (a Michael Franks remake).  Diana’s vocals sounded very sultry as it should.  The brushes had great air and the sound was very well separated.  I moved on to Morph the Cat, Donald Fagen’s latest album.  I found the 02-ARC’s once again excelled though there was a bit of heaviness in the upper bass region.  Some of this is in part due to the recording but most of it has to do with the placement of the speakers so close to so many wall surfaces (backwall + ceiling + sidewalls).  This is known as 1/8^th space or pi/2 loading which can yield up to +18dB of boundary gain.

I fired up some Latin music as my wife wanted to hear how the 02-ARC’s would render her favorite music.  Corazon Profundo from Carlos Vives was rockin’ our room.  Track #1 “Volví a Nacer” demonstrated that the NHT’s meant business.  They handled the percussions with aplomb and the high frequency detail was excellent, never sounding overly bright or fatiguing.  The elevated treble response we measured really helped with off-axis performance since these speakers were placed a few feet above our heads without the ability of being tilted down.

We finished off our listening session with our wedding song from Richard Marx, “Keep Coming Back.”  I never tire of this great song and feel that Richard Marx is one of the most underrated artists of our time.  The bass produced by the 02-ARC’s was not exceedingly deep but it was well-controlled.  The stereo separation was excellent and the bite in Richard’s voice was well reproduced.  The amount of detail extracted in this recording given the environment the speakers were installed in was most impressive.

The NHT 02-ARC’s proved to be a significant step up in sound quality, build quality and measurements compared to my reference Axiom M3 Outdoor speakers.  While the Axiom’s reached down a bit lower in extension, they weren’t as clean sounding or tight in the bottom end.  The NHT’s proved to be far more linear, producing a larger, more open soundstage, cleaner more articulate vocals and better separation of instruments.

NHT 02-ARC Outdoor Speaker Measurements and Analysis

The measurements were conducted in conformance with Audioholics Loudspeaker Measurements Standard

NHT 02-ARC On-Axis Frequency Response

The on-axis frequency response was conducted with the measurement microphone at 1 meter from the speaker baffle between the woofer and tweeter with a 2.83V excitation signal. Audioholics measures sensitivity as the average sound pressure level (SPL) from 300 to 3kHz.  The Audioholics rated sensitivity for the NHT 02-ARC outdoor loudspeaker is an average 85.4dB.  The speaker approaches the manufacturer rated 88dB sensitivity at around 100 Hz and above 8kHz.  The overall frequency response of the loudspeaker is +/- 2.5 dB from 70Hz to approximately 15kHz.  Directly on-axis, the tweeter has a steep rising response above 15kHz. The rising response above 15kHz on-axis yields a flatter off-axis response, which may be a benefit for an outdoor loudspeaker.  The qualitative effect of a rising tweeter response above 15kHz depends on the hearing range of the listener.  Bass response in the sealed cabinet falls off very linearly at 12dB/octave below 80Hz allowing for simple integration with a subwoofer.

NHT 02-ARC Listening Window

The listening window response is the average of 5 measurements ranging from 30 degrees left to 30 degrees right plus measurements 15 degrees above the speaker and 15 degrees below the speaker.  When the loudspeaker has symmetry about the vertical axis, the right and left are equal and the total number of measurements is reduced to five. The measurement provides a picture of how the loudspeaker performs from seating locations that are not directly on axis with the speaker.  The top curve is the average of the seven positions and provides an idea of how the speaker performs throughout a listening area.  The listening window response for the NHT 02-ARC is excellent.  Notably, at 15 degrees off-axis the loudspeaker frequency response is very flat.

NHT 02-ARC Polar Response with Grill

The polar response graph shows how a loudspeaker performs at various seating positions in a room.  The polar response graph above was generated by measuring a loudspeaker at 7.5-degree intervals around a circle half way between the woofer and tweeter height at a distance of 1 meter.  The NHT 02-ARC has uniform polar response with slight aberrations in the upper treble range.  The grille of the loudspeaker has a squared off plastic edge that extends from the speaker baffle approximately ½”.  An additional polar response measurement was conducted without the grille yielding the response shown below.

NHT 02-ARC Polar Response Without Grille

Clearly, the loudspeaker grille has a substantial effect on the off-axis upper treble frequency response.  The performance of this loudspeaker is quantitatively superior with the grille removed.

NHT 02-ARC Impedance

The impedance of the NHT 02-ARC loudspeaker dips far below the IEC 6.4 ohm minimum for a manufacturer rated 8-ohm speaker.  So much so that I checked all of the settings and connections several times to make sure the measurements were accurate.  When all else failed, I measured a speaker with known impedance to validate the test rig.  From 500Hz up, this speaker could be considered an 8-ohm speaker.  For frequencies below 500Hz, this speaker is clearly a 4-ohm speaker.  It is highly advisable to drive this loudspeaker with an amplifier that is 4-ohm stable.  If these were my speakers, I would get a label maker out and cover the 8-Ohm label with a 4-Ohm label. 

 

NHT 02-ARC Harmonic Distortion

The harmonic distortion graph was generated using a 90dB stepped sinusoid sweep measured at 2 meters.  This is the last test we perform on a loudspeaker since it really tortures loudspeakers.  This test was run full range putting the sealed 6.5” polypropylene woofer through the ringer.  Considering the size of this loudspeaker, the distortion remains very low averaging well below 1% for the 2^nd and 3^rd order harmonics above 60 Hz.  The offensive higher order harmonics are very well behaved. There is nothing to complain about here.  This is superlative performance and no doubt a major contributor to the speaker’s taut, controlled sound.

NHT 02-ARC Cumulative Spectral Decay

Cumulative spectral decay (CSD) is derived from the impulse response measurement taken with a 90dB excitation signal at 1 meter.  The cumulative spectral decay shows how sound at various frequencies dies out as a function of time.  It is important to note that the leftmost ridge is not valid and is a product of the measurement technique.  The CSD for the NHT 02-ARC does not show any offensive artifacts except the ridge that reappears at 1500Hz at around 2ms.  One explanation, albeit not conclusive, is that the speaker is stand mounted.  Resonance and reflections from anything close to the speaker will affect the measurement and there isn’t much any manufacturer can do to fix this issue.  Since this is greater than 20dB below the reference level, it is nothing to worry about. 

NHT 02-ARC Group Delay

The group delay graph shows the rate of change of the slope of a loudspeaker’s phase.  As a rule of thumb, values below 1.6ms in the mid to high frequencies will likely not effect perception of sound quality.  Increasing group delay in the low frequencies is not as objectionable as it is in the mid to high frequency ranges.  The NHT 02-ARC group delay values are below 1ms at 300Hz.

NHT 02-ARC Outdoor Speaker Conclusion

NHT proved they could make a truly high performance speaker system designed for the outdoors.  The 02-ARC’s impeccable build quality, and fit and finish is among the best I’ve seen in this category of product. They measure like a high quality indoor bookshelf and sound great in any environment.  The only caution is they should be paired with amplification stable into 4 ohm loads.  Some lower-end receivers may not be too happy with these speakers.

If you’re looking for a true high-performance, weather-resistant outdoor speaker system, the NHT 02-ARC comes with my highest recommendation!

NHT 02-ARC Outdoor Speaker Video Review

NHT 02-ARC Review

 NHT Audio LLC

Benicia, CA  94510

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

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Dynamic Range
Performance
Value