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NHT Super Zero 2.1 Review (bookshelf speaker)

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amirm

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This is a review and detailed measurements of the NHT Super Zero 2.1 "Mini Monitor" speaker review. Despite the "monitor" designation, this is a passive speaker needing external amplification. I purchased this unit back in January for US $70 (single unit). Company list price is US $149 but is on sale now for $125 (again, each).

This is a very compact and rather dense speaker:

NHT Super Zero 2.1 Review speaker wall mount bookshelf.jpg


The back panel shows lack of any kind of port:
NHT Super Zero 2.1 Review speaker wall mount back panel bookshelf.jpg


The finish is nice and glossy but the corners are very sharp which is not easy on the hand or measurements likely.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 800 measurement which resulted in error rate of less than 1% throughout the range.

Temperature was 60 degrees F. Measurement location is at sea level so you compute the pressure.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the tweeter center.

NHT Super Zero 2.1 Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Spinorama CTA 2034 Spinorama Frequency Respo...png


The most glaring issue he is lack of bass response which is due to lack of port and tiny enclosure. Second issue related to same factors is very low sensitivity. Third is poor directivity due to lack of any mechanism to get the beamwidth of the tweeter and woofer to match at crossover point:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Horizonta Beamwidth.png


The blue arrow shows the classic response of a tweeter (or any driver) as wavelengths get smaller. The tweeter gets progressively more directional. Same is happening to the woofer so we get a mismatch around 4 to 5 kHz. This then translates into our off-axis response being uneven and not match the direct sound:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Spinorama CTA 2034 Spinorama Early Window Fr...png


Result is a response with a dip in critical range of music:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Spinorama CTA 2034 Spinorama Predicted In-ro...png


Combine that with lack of bass and this speaker will likely not sound good.

Directivity plots show what we have seen already:
NHT Super Zero 2.1 Measurements Bookshelf Speaker Horizonta directivity.png


NHT Super Zero 2.1 Measurements Bookshelf Speaker Vertical directivity.png


Distortion story naturally is not good:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Relative Distortion.png


NHT Super Zero 2.1 Measurements Bookshelf Speaker  Distortion.png


Finally here is our impedance and phase:

NHT Super Zero 2.1 Measurements Bookshelf Speaker impedance nad phase.png


EDIT: forgot the drive response:

NHT Super Zero 2.1 Measurements Bookshelf Speaker Driver Response.png


NHT Super Zero 2.1 Speaker Listening Tests
I hooked up the 2.1 to my main system placed on top of a stand for standard far-field listening. The sound was dead on multiple fronts: there was no volume making me crank my powerful amplifier to ungodly levels. Then there was no bass and I mean no bass. The moment the music would rely on bass notes to carry on, the sound level would go way down. Ditto for anything in 2 to 3 kHz range. A 3 dB boost in that region gave the speaker some lift but really, I was so unhappy with the experience that I shut everything off and that was all she told.

Conclusions
Amazing that a company like NHT that had a great reputation in the 1990s into 2000s has fallen by the wayside so much. There is nothing in this design that follows what we know listeners want: bass, even response, even directivity. And oh, some efficiency would be good too as I doubt someone wants to save money on a speaker and then wants to spend more to buy a powerful amplifier/receiver to drive it.

Very disappointing. Needless to say, I can't recommend the NHT Super Zero 2.1. If you need something this small, get a powered monitor as they have a far more optimized design than that is here.

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dougi

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NHT say the crossover is at 2kHz, 12dB slopes. The poor directivity seems to suggest it is higher for a woofer that small. Too late to do driver plots @amirm?
 

BillH

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The onslaught of reviews keep coming - thank you Amir.
I remember along time ago the super zeros were a bit of a darling of the community about the same time the paradigm titans or atoms came out.
if all that mattered was on axis FR they would mostly only be base shy. The days of mediocrity are long gone.
 
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amirm

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NHT say the crossover is at 2kHz, 12dB slopes. The poor directivity seems to suggest it is higher for a woofer that small. Too late to do driver plots @amirm?
Oops. Forgot to put it in the review. It is there now:

index.php
 

Rock Rabbit

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Oops. Forgot to put it in the review. It is there now:

index.php
Tweeter resonance at crossover frequency (?) no good for tweeter health. If not for efficiency the tweeter makes a "good" woofer (if a "woofer " start at 100 Hz :()
 

617

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2k LR2 with these size of drivers should have nicer directivity blending but NHT had managed to snatch defeat from the jaws of victory
 
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Amir,

What is it you were expecting from this speaker?

This is a 30+ year old design where they didn't pay any attention to directivity control.
Also, it was never designed as a full range speaker and always intended for mated subwoofer bass augmentation. That's why it's a sealed-box design for crying out loud.

My goodness.

Dave.
 

SIY

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MZKM

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Amir,

What is it you were expecting from this speaker?

This is a 30+ year old design where they didn't pay any attention to directivity control.
Also, it was never designed as a full range speaker and always intended for mated subwoofer bass augmentation. That's why it's a sealed-box design for crying out loud.

My goodness.

Dave.
It’s a current model, and MSRP is $300/pair. I see no qualities that would compel someone to buy this over another offering.
 

GDK

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ROOSKIE

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NHT say the crossover is at 2kHz, 12dB slopes. The poor directivity seems to suggest it is higher for a woofer that small. Too late to do driver plots @amirm?
The directivity difference between a 4" and 5.25 or 6.5" is not much. In other words you generally gain very little, a 4" woofer still needs to be crossed at nearly the same frequency as a 6". OR use a waveguide or a true midrange driver (anything LESS than 4 or a 4" designed for midrange specific duty)

Amir,

What is it you were expecting from this speaker?

This is a 30+ year old design where they didn't pay any attention to directivity control.
Also, it was never designed as a full range speaker and always intended for mated subwoofer bass augmentation. That's why it's a sealed-box design for crying out loud.

My goodness.

Dave.
Have to partially agree here, this is a good design choice as they simply require a sub - no stressing that cheap 4" woofer.

NHT still sells a lot of these due to popularity though which is a shameful excuse not to update them. So on that level NHT needs to get with it. They have design chops but this model is well overdue for a little freshen up.
 

ROOSKIE

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From that page:

”Unlike most small speakers, which try to fool you with boomy, pseudo-bass from a port, the SuperZero 2.1 acoustic suspension (sealed) enclosure skips the bass and focuses on making beautiful, lifelike midrange and high frequencies.”

EDIT: Who needs bass? Let’s just skip it...
No you buy a subwoofer.
 

SIY

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I haven't heard the current versions. I have a pair of the Super Zeros from the '90s that I've used over the years as lab speakers (amp loads, noise sources, background music). When you play pink noise through them, the tweeter and "woofer" sound very separate and distinct from one another rather than integrated. They definitely could use some crossover work...
 

ROOSKIE

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NHT still does have some decent gear.
Wish I still had the NHT C3 pair to submit.
I did not keep them but they were generally excellent speakers.
Be cool to see them measured here

Obviously not a post about this speaker reviewed here but just for some NHT insight
Both C3 reviews show very good measurements. (likey still need a sub, I found them slightly bright but tolerable and very, very detailed with shy but articulate bass. These were not a warm speaker.)

https://www.soundstagenetwork.com/i...carbon-fiber-loudspeakers&catid=77&Itemid=153

https://hometheaterhifi.com/reviews/speaker/bookshelf/nht-c3-bookshelf-speaker-review/

1608605796369.png
 
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MZKM

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NHT still does have some decent gear.
Wish I still had the NHT C3 pair to submit.
I did not keep them but they were generally excellent speakers.
Be cool to see them measured here

Obviously not a post about this speaker reviewed here but just for some NHT insight
Both C3 reviews show very good measurements. (likey still need a sub, I found them slightly bright but tolerable and very, very detailed with shy but articulate bass. These were not a warm speaker.)

https://www.soundstagenetwork.com/i...carbon-fiber-loudspeakers&catid=77&Itemid=153

https://hometheaterhifi.com/reviews/speaker/bookshelf/nht-c3-bookshelf-speaker-review/

View attachment 100800
Was surprised by the low sensitivity they measured as well as for the models Amir has measured. Reason being that I emailed them asking how they rate sensitivity, and their engineer responded by saying they basically calculate it how we would hope:
“We use the average anechoic SPL over a range (~500-2KHz) @ 1M, on-axis with 2.83 VRMS driving voltage.”
I guess he just lied to me via email.
 
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whazzup

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Is this considered a 'narrow directivity' speaker? Supposedly narrow ones are better for home theatre surround use?

Or should this just be a 'bad directivity' speaker? Trying to understand the distinction when looking at the directivity aspect in different use cases.
 

Kachda

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Is this considered a 'narrow directivity' speaker? Supposedly narrow ones are better for home theatre surround use?

Or should this just be a 'bad directivity' speaker? Trying to understand the distinction when looking at the directivity aspect in different use cases.
A narrow directivity speaker would still have good directivity, just that off axis is at lower volume compared to wider directivity speakers. This speaker has bad directivity, causing off axis and reflections to sound different from on axis, muddling to the sound.
 

dougi

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The directivity difference between a 4" and 5.25 or 6.5" is not much. In other words you generally gain very little, a 4" woofer still needs to be crossed at nearly the same frequency as a 6". OR use a waveguide or a true midrange driver (anything LESS than 4 or a 4" designed for midrange specific duty)
Yeah I guess even among 4" mid woofers they vary. I recently used the SB12PFC25-8 to replace blown SEAS CA14-RCY and a sealed conversion. Much better off axis at 2kHz but other issues such as surround diffraction. This may have been better than whatever NHT used.

sb.JPG
 
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