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NHT C3 Review (3-way speaker)

amirm

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This is a review and detailed measurements of the NHT C3 3-way, sealed speaker. It was purchased new by a member and kindly drop shipped to me. It costs US $391 on Amazon for a single unit.

I must say, I was impressed by the fit and finish of the C3:

NHT C3 review sealed speaker.jpg


The enclosure is sold and dense with a beautiful piano black finish.

I love that the back panel has threaded screw holes to mount the speaker to the wall/ceiling for surround/Atmos applications:

NHT C3 review sealed speaker binding posts.jpg


Speaker is manufactured in China.

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 1000 measurement which resulted in error rate of around 1%.

It is down to freezing outside so the best I could do was raise the temperature to 56 degrees. Speaker however was kept warm indoors prior to measurements.

Reference axis was that of the tweeter. Grills were not used.

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.

NHT C3 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 C3 Measurements Speaker Spinorama CEA-2034 Frequency Response.png


EDIT: looks like the mid-range is damaged in this unit. It has a dimple on the bottom of it. This could explain the mid-frequency dip. Unfortunately I only have one unit to test so can't verify.

On-axis response is kind of wavy. This was unexpected as measurements performed elsewhere are much flatter. My in-room measurements showed the same so I don't think it is an issue with NFS measurements. Likely a design change was made to tilt up the highs more to keep up with the competition in the showroom. We can see the uneven response in individual driver response:

NHT C3 Measurements Speaker driver frequency response.png


Seems like one could push up the tweeter level a bit or else, bring the tweeter down. The tweeter by itself has uneven response.

As noted in the first graph directivity is good so for good or bad, early window reflections follow on-axis irregularities:
NHT C3 Measurements Speaker Spinorama CEA-2034 Early Window Frequency Response.png


Predicted in-room response shows very little tilt so speaker is going to sound bright:

NHT C3 Measurements Speaker Spinorama CEA-2034 Predicted In-room Frequency Response.png


As I noted, directivity is good due to use of mid-range driver:

NHT C3 Measurements Speaker  horizontal beamwidth.png

NHT C3 Measurements Speaker  horizontal directivity.png


If you are going to use this up high for surround applications, be sure to tilt it down some:

NHT C3 Measurements Speaker  Vertical directivity.png


Distortion was two completely different stories depending on level:
NHT C3 Measurements Speaker relative distortion.png


At 86 dB, this is professional monitor level of distortion, not a budget passive speaker! Push it though and things get bad especially with that tweeter. I have not seen one fall apart this badly. Fortunately that is where we have elevated response so we would want to EQ that down anyway and that should help keep that distortion in check.

Needless to say, at 94 dBSPL it exceeds our threshold:
NHT C3 Measurements Speaker THD distortion.png


Impedance is typical of these speakers, down to 4 ohm or so:

NHT C3 Measurements Speaker impedance and  phase.png


I forgot to mention earlier that sensitivity is rather low, dropping to 82 to 83 dB in mid-range area. Company advertises 87 dB which would only be true of the peaking tweeter.

NHT C3 Listening Tests and Equalization
The high frequency peaking was not obnoxious but clearly overdone (as appealing as that could be for a few seconds). So had to EQ that anyway and while there, might as well tweak the rest:

NHT C3 Equalization EQ Filters.png


Filling that little but wide dip in upper bass was important in providing balance relative to highs (which I did not fully cure on purpose). I then filled in the 1 to 4 kHz region and job was done. Once there, the benefits of a sealed enclosure was there with its ability to play sub-bass without getting distorted. Alas, without the boosted upper bass that we get from ported speakers, the bass was a bit light but I was fine with that.

Dynamics was very good and speaker could handle a lot of power. And a lot of power is what I had to feed it so don't get a 50 watt amp. You need more than that.

Conclusions
It is a shame we didn't measure the C3 as well as others had. That would have made it a lot closer to ideal. As is, without EQ it is bright and hence "detailed." To my ears, that gets old fast so EQ is mandatory in my book. And so is filling in the other two dips. Speaker takes EQ well since we are not trying to push it where distortion is highest.

Overall, I was happy with the NHT C3 and would recommend it with EQ. No without.

------------
As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

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Doodski

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Wowowow a 3 way speaker. Those are rare as hen's teeth these days. :D
 

cursive

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Been looking forward to this one, thanks for taking the time to do it Amir. Also it saved me from having to send mine in, so thank you to whomever sent it!

I feel like I definitely hear the benefits of the sealed design in the bass as you pointed out, but is there any benefit to this unit being a 3 way, or is it more of a selling point and could be achieved with just two drivers?
 

dfuller

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Doesn't look too bad! And, always nice to see sealed cabinets. I find them preferable at prices where big investment in R&D isn't feasible because ports always have problems if they aren't designed perfectly. .
 
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amirm

amirm

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Shoot, the owner noticed that in my picture the midrange is poked in on the bottom and it is!!! That could explain the worse than normal response in that region. I tried to see if I can poke it with my finger and I cannot. So it must have come that way. I will add a note to the review.
 
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amirm

amirm

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And one more thing :). The bubbles you see on the slanted sides of the speaker are not there. They are a reflection from my lightbox. The whole speaker is smooth, black piano finish.
 

txbdan

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Interesting! I sent this one in to Amir as I have a pair of these on my desktop. I did a casual $300ish bookshelf shootout where I really liked the C1, but wanted more low end. That prompted me to up-budget a bit and get the C3s. The price fluctuates quite a bit on Amazon, I paid $322 each. The two standout qualities for me is the accurate low end and (don't shoot me) transparency. They sounded so natural to my ears. Finish and build quality is very good, too, they are tanks. That said, I do currently use Dirac Live to correct them :-D

FWIW, here's my measured room response. Interestingly it looks a bit more like soundstagenetwork's measurement than Amir's. Bump at 1.5-2kHz and dip around 5-7kHz. Of course the mess below 600Hz is my room. (The light colored line is the response, the dark flat line is Dirac's predicted response after correction)
C3corrected2.png
 
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Beave

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Shoot, the owner noticed that in my picture the midrange is poked in on the bottom and it is!!! That could explain the worse than normal response in that region. I tried to see if I can poke it with my finger and I cannot. So it must have come that way. I will add a note to the review.

Those midrange domes are incredibly fragile. The slightest touch can dent them. I know from experience with the previous version, the Classic Three. :facepalm:
 
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cursive

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Those midrange domes are incredibly fragile. The slightest touch can dent them. I know from experience with the previous version, the Classic Three.

I was going to say the same thing! I had the Classic Three as well which had an even smaller guard on them.

I have seen them able to be pulled out by sticking very mild/weak tape to the dent, and carefully pulling, but obviously that will be up the owner to decide how to proceed. It could easily be damaged with tape as well.

@txbdan I also have these on my desktop and love them! Thank you so much for sending one in.
 

Beave

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The NHT C3 with the "carbon fiber" finish was measured by Soundstage at the NRC. Results here.

Note that the NRC measurement axis was between the midrange and tweeter, which could account for a *little* of the differences shown in the response in the midrange to lower treble.

That small dent in the midrange dome might also be contributing, but I wouldn't think it would make for such a broad dip over the driver's entire range.

I can't help but wonder if this is a unit-to-unit variation, possibly in crossover component tolerances, making the entire midrange output a little lower than it should be (as Amir notes in his plot of individual drivers).
 
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Beave

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I was going to say the same thing! I had the Classic Three as well which had an even smaller guard on them.

I have seen them able to be pulled out by sticking very mild to the dent, and carefully pulling, but obviously that will be up the owner to decide how to proceed. It could easily be damaged with tape as well.

@txbdan I also have these on my desktop and love them! Thank you so much for sending one in.

Yeah, when I bought my Classic Threes used, they had a tiny indentation. I tried to pull it out with tape and only made it worse with the slightest touch. Doh!
 
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amirm

amirm

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Note that the NRC measurement axis was between the midrange and tweeter, which could account for a *little* of the differences shown in the response in the midrange to lower treble.
Oh. I almost did the same but then went with the tweeter. I can still manually recompute it.
 

Beave

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It's crazy how much the distortion jumps up at the higher output measurement.

The sensitivity is low, and the impedance phase angles get pretty high (down to almost -50 degrees and up to almost +60 degrees).

Put all that together and these aren't speakers that are made to play super loud.
 

Beave

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Been looking forward to this one, thanks for taking the time to do it Amir. Also it saved me from having to send mine in, so thank you to whomever sent it!

I feel like I definitely hear the benefits of the sealed design in the bass as you pointed out, but is there any benefit to this unit being a 3 way, or is it more of a selling point and could be achieved with just two drivers?

The three way here helps a lot with the consistently wide directivity in the upper midrange to low treble.
 

Beave

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And one more thing :). The bubbles you see on the slanted sides of the speaker are not there. They are a reflection from my lightbox. The whole speaker is smooth, black piano finish.

Ha, I saw that and was immediately puzzled, then I realized it had to be reflections. :)
 

Tks

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That upper end distortion is worrisome. Question Marks trying to find how high it really goes was a nice touch lol.
 

ROOSKIE

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The Sound Stage measurements are pretty different.
1613020065202.png


I do wonder if damage exceeds just cosmetic. Maybe something interanl. That tweeter is just lost at 96db.

What is strange is that their HD test shows very low HD even at [email protected] equivalent (they use [email protected]) & no issue with the tweeter.

1613019915305.png



Was the speaker brand new or was it an Amazon Warehouse special?
 

YSC

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Shoot, the owner noticed that in my picture the midrange is poked in on the bottom and it is!!! That could explain the worse than normal response in that region. I tried to see if I can poke it with my finger and I cannot. So it must have come that way. I will add a note to the review.
That’s great eyesight! I didn’t thought that’s the surround originally! So it seems like some shipping problem?
 
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amirm

amirm

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Was the speaker brand new or was it an Amazon Warehouse special?
As far as I know, new. Owner just arranged for an exchange. Once the other sample comes I will repeat the measurements.
 
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