Radiant Acoustics Clarity 66 Speaker Review

[dfuller]

Erin's review is out now:

View attachment 556217

LLM summary:

This video by Erin's Audio Corner features a detailed review and Klippel Nearfield Scanner measurements of the Radiant Acoustics Clarity 66, along with comparisons to the Arendal 1723/1961 tower series and Mobile Fidelity (MoFi) SourcePoint monitors.

Key Takeaways​

• Design and Build: The Clarity 66 is a 2-way system (despite housing dual 6.5-inch Purifi woofers) paired with a custom Air Motion Transformer (AMT) tweeter. It features a 15 mm aluminum front baffle and a ported cabinet tuned to ~30 Hz [01:29].
• Listening Impressions: Erin found them exceptionally enjoyable and non-fatiguing over long sessions, praising their tonal balance and ability to strike a sweet spot between wide envelopment and precise imaging [00:29].
• Pros:
  • Exceptionally low distortion and high overall linearity [03:56].
  • Deep in-room low-frequency extension down to roughly 30 Hz [04:06].
  • Predictable, clean off-axis response that allows for easy tonal tuning via toe-in [05:08].
• Cons:
  • Very tight vertical dispersion: Requires a strict listening height, making it less ideal for casual wandering or multi-row home theater seating [05:42].
  • Lower sensitivity (~85 dB): Demands robust upstream amplification to reach high output levels without clipping [06:31].
  • Bass character: While it extends low, it lacks the visceral chest-punch at 30–40 Hz that a dedicated subwoofer provides [04:16].
• Measurements & Comparisons: The Klippel data confirms an overall smooth frequency response and excellent resonance control, though it highlights a slight upper-midrange dip due to vertical lobing constraints. Compared to the MoFi and Arendal alternatives, the Radiant Acoustics model offers superior bass linearity and controlled horizontal dispersion (~60°), though individual trade-offs in distortion and room interaction mean choice ultimately depends on listener preference and room layout [16:53].

This is what I mean when I say that Erin's distortion measurements are usually lower than Amir's - check this out.

Erin doesn't show it going over 1% down to below 30hz. His are true free field, using the Klippel distortion module that allows for it.

Amir's, on the other hand, goes way higher (over 3% at 40hz) because his measurements consistently show a response droop in the low end. It's probably about the same distortion, but Amir's distortion measurements consistently read higher.

 

[Curvature]

This is what I mean when I say that Erin's distortion measurements are usually lower than Amir's - check this out.

View attachment 556279


Erin doesn't show it going over 1% down to below 30hz. His are true free field, using the Klippel distortion module that allows for it.

Amir's, on the other hand, goes way higher (over 3% at 40hz) because his measurements consistently show a response droop in the low end. It's probably about the same distortion, but Amir's distortion measurements consistently read higher.
View attachment 556280

I believe @amirm's distortion plots are not anechoic.

 

[amirm]

Erin doesn't show it going over 1% down to below 30hz. His are true free field, using the Klippel distortion module that allows for it.

Amir's, on the other hand, goes way higher (over 3% at 40hz) because his measurements consistently show a response droop in the low end. It's probably about the same distortion, but Amir's distortion measurements consistently read higher.

There are a lot of factors behind the scenes which impact distortion measurements:

1. You don't really know the true SPL levels. Speakers have variable frequency response. I basically eyeball 1 kHz but you could argue other frequencies should be used for the calibrated output. And Erin may have used another strategy altogether.

2. You don't know if my calibrated level mic, or Erin's are more correct.

3. The Klippel NFS structure is great for frequency response measurements but rather poor for distortion. The whole thing buzzes and rattles with speaker resonances as do other objects in the room. I use a 1/3 meter distance to sharply reduce these effects. That could raise the distortion that the mic generates but it has the benefit of not capturing as much of these other noise sources. Again, i don't know what Erin uses.

4. Best place is an ultra quiet anechoic chamber. To that end, I have compared my distortion measurements to ones generated by Neumann and KEF. Their results correlate very well according to companies. So much so that we found an issue with a KEF sample which was replaced.

5. This is an aside but it is NOT wise to compare absolute levels of distortion because no speaker frequency response is flat. -50 dB relative to 0 dB is a very different animal than -50 dB vs -10 dB signal. This is why I lead with percentage instead of absolute levels. I realize you eyeballed the same from Erin's graph but that it is best to not go through that gymnastic.

Net, net, best to not cross shop distortion results.

 

[Penelinfi]

We sent Amir a completely new sample. He's the only one who's used them. There should be little reason for concern

Hmm, shipping and taxes would probably cost as much as the savings where I am

 

[smokeymackinsey]

Hmm, shipping and taxes would probably cost as much as the savings where I am

Our prices always include shipping, tax and duties
Jasper
Nordic Hifi / Radiant Acoustics

 

[Curvature]

There are a lot of factors behind the scenes which impact distortion measurements:

1. You don't really know the true SPL levels. Speakers have variable frequency response. I basically eyeball 1 kHz but you could argue other frequencies should be used for the calibrated output. And Erin may have used another strategy altogether.

2. You don't know if my calibrated level mic, or Erin's are more correct.

3. The Klippel NFS structure is great for frequency response measurements but rather poor for distortion. The whole thing buzzes and rattles with speaker resonances as do other objects in the room. I use a 1/3 meter distance to sharply reduce these effects. That could raise the distortion that the mic generates but it has the benefit of not capturing as much of these other noise sources. Again, i don't know what Erin uses.

4. Best place is an ultra quiet anechoic chamber. To that end, I have compared my distortion measurements to ones generated by Neumann and KEF. Their results correlate very well according to companies. So much so that we found an issue with a KEF sample which was replaced.

5. This is an aside but it is NOT wise to compare absolute levels of distortion because no speaker frequency response is flat. -50 dB relative to 0 dB is a very different animal than -50 dB vs -10 dB signal. This is why I lead with percentage instead of absolute levels. I realize you eyeballed the same from Erin's graph but that it is best to not go through that gymnastic.

Net, net, best to not cross shop distortion results.

I have to disagree here. With care, the end result is still meaningful. At every stage a lot of thought has been put into accuracy and and reliability, so although there are uncertainties and inaccuracies, they are fine rather than gross in most cases.

The graph below presents your absolute THD measurement relative to FR. Your data vs. Erin's has only small deviations other than in the bottom octave despite everything. Figuring out the root causes for the difference would take work and some level of collaboration.

Comparing your results to Neumann's shows a lot of agreement. Note that their measurement is at 95dB vs your 96dB SPL.

Despite the Radiant 66 being much bigger and Purified, the KH150 competes.

 

[Curvature]

For completeness, I was thinking Purifi will point to IMD being the more telling metric. I showed the accuracy of @Nuyes's multitone distortion measurement procedure vs. Erin's here: https://www.audiosciencereview.com/...re-about-to-launch.54794/page-77#post-2345533 Not surprising since they both use Klippel products.

Below compares the KH150 vs. Clarity 66 MTD at 96dB. Nuyes uses the separate Klippel distortion module, not the NFS, so although the KH150 is being tested full-range, he does not show results lower than 100Hz due to the intrusion of room noise. We would probably see greater separation between the curves in that region between these two speakers. I do like the MTD plots in general because they show what happens at crossover points and frequency extremes, where distortion tends to climb.

Finally, I don't see how, despite claims to the contrary, THD is not a reliable predictor of other distortion, or that Purifi-based speakers necessarily outperform others by skilled designers by a wide margin. One thing for sure: Purifi has closed the technological/knowledge gap or other firms and probably increased the level of competition across the industry.

 

[b73i57dc3f]

Despite the Radiant 66 being much bigger and Purified, the KH150 competes.

Not really. Look at the fundamental, the Clarity 66 extends far deeper, and at 30 Hz, was playing a whopping 9 dB louder than the KH 150 in that measurement:

Same (roughly) THD relative to the fundamental, while actually playing the fundamental 9 dB louder, in my book that's a clear win for the Clarity 66. Your graph also shows that the THD of the Clarity 66 is clearly lower from about 60 to 2000 Hz.

 

[Curvature]

Not really. Look at the fundamental, the Clarity 66 extends far deeper, and at 30 Hz, was playing a whopping 9 dB louder than the KH 150 in that measurement:
View attachment 556617
Same (roughly) THD relative to the fundamental, while actually playing the fundamental 9 dB louder, in my book that's a clear win for the Clarity 66. Your graph also shows that the THD of the Clarity 66 is clearly lower from about 60 to 2000 Hz.

Wouldn't you expect more from speakers that cost $10k a pair vs. $3400? On a relative basis I'm not seeing clear dominance.

Easier to make FR-related comparisons here: https://www.spinorama.org/compare.h...aker1=Neumann+KH+150&origin1=ASR&version1=asr

 

[b73i57dc3f]

Wouldn't you expect more from speakers that cost $10k a pair vs. $3400? On a relative basis I'm not seeing clear dominance.

We were talking THD, not price, that's a whole different can of worms. I mainly wanted to highlight that the THD performance of the Clarity 66 is actually markedly better in deep bass compared to the KH 150, since this is very easy to miss when just looking at the relative THD graphs you posted, since they don't show the fundamental. If you added the KH 420 ($11,200) to your comparison, at first glance, it wouldn't look very impressive compared to the KH 150 either.
Speaking of the KH 420, that's also a good example for THD not being a reliable predictor of MTD. In a MTD measurement, its distortion throughout the upper midrange is quite a bit lower than the Clarity 66, but not so in a THD measurement.

Easier to make FR-related comparisons here: https://www.spinorama.org/compare.h...aker1=Neumann+KH+150&origin1=ASR&version1=asr

I am aware, but talking THD, one has to look at the fundamental in the THD measurement, since sometimes there can be compression or limiting at higher output levels, and Amir's THD measurments are also not anechoic and he's not aligning SPL the same as spinorama.org.

 

[Curvature]

We were talking THD, not price, that's a whole different can of worms. I mainly wanted to highlight that the THD performance of the Clarity 66 is actually markedly better in deep bass compared to the KH 150, since this is very easy to miss when just looking at the relative THD graphs you posted, since they don't show the fundamental. If you added the KH 420 ($11,200) to your comparison, at first glance, it wouldn't look very impressive compared to the KH 150 either.
Speaking of the KH 420, that's also a good example for THD not being a reliable predictor of MTD. In a MTD measurement, its distortion throughout the upper midrange is quite a bit lower than the Clarity 66, but not so in a THD measurement.

I am aware, but talking THD, one has to look at the fundamental in the THD measurement, since sometimes there can be compression or limiting at higher output levels, and Amir's THD measurments are also not anechoic and he's not aligning SPL the same as spinorama.org.

I used a little math to show the distortion relative to the FR. In other words the charts you're seeing distortion compensated for FR and the actual difference between the measurements. I mainly went through this exercise to demonstrate that this data can be compared meaningfully between reviewers and a reputable manufacturer, all of whom are careful about accuracy, even though the methods are different.

The fact that a little, cheaper speaker can come close means a lot to me. The same little speaker has better directivity, on axis flatness, fewer resonances and I would bet better speaker to speaker consistency. Although it's not completely fair to compare a passive to an active speaker.

I'm not surprised that the Clarity 66 has better distortion performance in the low bass and midrange—it makes sense given an extra driver, transmission line design and large box. What I found surprising and interesting is that in some areas the difference is fairly small.

 

[kharan]

I used a little math to show the distortion relative to the FR. In other words the charts you're seeing distortion compensated for FR and the actual difference between the measurements. I mainly went through this exercise to demonstrate that this data can be compared meaningfully between reviewers and a reputable manufacturer, all of whom are careful about accuracy, even though the methods are different.

The fact that a little, cheaper speaker can come close means a lot to me. The same little speaker has better directivity, on axis flatness, fewer resonances and I would bet better speaker to speaker consistency. Although it's not completely fair to compare a passive to an active speaker.

I'm not surprised that the Clarity 66 has better distortion performance in the low bass and midrange—it makes sense given an extra driver, transmission line design and large box. What I found surprising and interesting is that in some areas the difference is fairly small.

I'm surprised that a little box can do that much in terms of distortion, this is true. I don't think price is that interesting of a comparison, there are $3K speakers that can handle bass better than the KH150.

But at the same time, the KH150 is also doing a LOT less in terms of output.

I used the Sound Power since it is more reflective of what goes into the room in the bass.

 

[Curvature]

there are $3K speakers that can handle bass better than the KH150.

I'm not saying that the KH150s are the best. It's just a good comparison with reliable data and interesting results.

 

[Jonazkur]

Just listened them. Bass was really good and overall sound was balanced. Imo i heard slight sibilance at treble. Could be bcouse the climbing on axis cant say for sure.

 

[kharan]

I'm not saying that the KH150s are the best. It's just a good comparison with reliable data and interesting results.

Despite the Radiant 66 being much bigger and Purified, the KH150 competes.

Your post made me think that you considered that there was more than a interesting data point comparison, it is an interesting factoid that their dis torsion numbers are similarish, but to me they don't "compete" in any way except for that anecdotal similarity in the numbers, they don't play in the same court.

Now, the Radiant 66 are $10k in the US, the KH420 is $11k, now these do absolutely compete.

And we'll see how the KH350 fares, I expect it'll be excellent.

 

[Curvature]

Your post made me think that you considered that there was more than a interesting data point comparison, it is an interesting factoid that their dis torsion numbers are similarish, but to me they don't "compete" in any way except for that anecdotal similarity in the numbers, they don't play in the same court.

Now, the Radiant 66 are $10k in the US, the KH420 is $11k, now these do absolutely compete.

And we'll see how the KH350 fares, I expect it'll be excellent.

I see it differently. Similar driver sizes and baffle width, similar lower limit of directivity control, similar distortion performance above 100Hz for both THD and MTD. The Clarity 66 pulls ahead in most places, with the main difference bring extension. I would guess max SPL would be similar too outside of the low bass if we had that information for the Clarity 66.

Edit: Typo.

 

[dfuller]

I believe @amirm's distortion plots are not anechoic.

Yes, my point was basically "looking at percentage isn't 1:1, Amir's are non-anechoic and read considerably higher at LF likely due to the droop in response below ~100hz".

Perfect example is the KH420 which Amir's measurements show rocketing up above 5% THD at 96dB below ~100hz... Where other measurements from S&R (RIP) and Neumann themselves show it not going beyond 3% at 95dB until below 30hz. Point is, be careful reading and comparing like for like, you can't do that if measurement conditions are not identical or at least very similar.

 

[Curvature]

Yes, my point was basically "looking at percentage isn't 1:1, Amir's are non-anechoic and read considerably higher at LF due to the droop in response below ~100hz".

The difference is on the order or 10dB so it has to be something more substantial than calibration differences.

It could be room noise or fixture vibration. Or it could be related to capturing the output correctly due to the position of the TL vent. I thought distortion would be captured during sound field separation, but perhaps that's incorrect and it needs a separate specific measurement.

 

[amirm]

. I thought distortion would be captured during sound field separation, but perhaps that's incorrect and it needs a separate specific measurement.

That process doesn't generate any distortion results. You have to measure distortion using a different module. Then, you can use yet another module to make it anechoic.

 

[kharan]

I see it differently. Similar driver sizes and baffle width, similar lower limit of directivity control, similar distortion performance above 100Hz for both THD and MTD. The Clarity 66 pulls ahead in most places, with the main difference bring extension. I would guess max SPL would be similar too outside of the low bass if we had that information for the Clarity 66.

To me that reads like those speakers would be comparable if you added a subwoofer to the KH150.

Getting good linearity and low distorsion in the midrange and in the treble is not that expensive, that the KH150 and the Clarity 66 compete there isn't surprising. What costs money is bass. You need stronger motors, larger enclosures, bigger drivers...