NEAT Acoustics Iota Alpha loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the NEAT Acoustics Iota Alpha's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. The first challenge I faced was deciding on which axis I should place my microphone for the farfield measurements. Sitting on its spikes, the Iota Alpha is 19" high, and its tweeter is just 17" from the floor. However, the section of the front baffle on which the tweeter and midrange unit are mounted is canted back at 30°, which aims those units directly at the ears of a listener seated a reasonable distance away. I therefore chose to make my primary response measurements on an axis perpendicular to the baffle, with the microphone pointed at the tweeter.

As might be expected from its small size, the Iota Alpha offers a low voltage sensitivity, my estimate being 83dB(B)/2.83V, which is 3dB lower than the manufacturer's claim. Looking at the NEAT's plot of impedance magnitude and electrical phase angle against frequency (fig.1), while the Iota Alpha is specified as a 4 ohm load, the impedance remains above 6 ohms for almost the entire audioband, dropping to 4 ohms only below 50Hz, and reaching 3.6 ohms at 10Hz. As the electrical phase angle is generally benign, I would venture to say that an 8 ohm–rated amplifier would have no difficulty driving the Iota.


Fig.1 NEAT Iota Alpha, electrical impedance (solid) and phase (dashed) (5 ohms/vertical div.).

Fig.1 reveals a small discontinuity just below 500Hz in each of the traces, implying the existence of some kind of resonant mode. Investigating the enclosure's vibrational behavior with a simple plastic-tape accelerometer, I found a fairly strong mode at 465Hz on the rear panel and front baffle (fig.2), and another, stronger mode at 684Hz. You can also see that the baffle "pumps" a little at one of the port's tuning frequencies.


Fig.2 NEAT Iota Alpha, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of front baffle (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

One of the port's tuning frequencies? As you can see from the red trace in fig.3, the rear-facing port behaves in a more complex way than the norm. While the downward-firing woofer has a sharply defined minimum-motion notch at 51Hz in its output (blue trace), instead of peaking at that frequency, the port has peaks both below and above it. Though there is a third peak at 400Hz in the port's output, this is well down in level and should have no effect on sound quality. As I had for the impedance measurement, I measured the woofer's nearfield output with the speaker raised, on its spikes, the necessary 1.5" from the floor; it covers a narrow bandpass of 80–140Hz, while the midrange unit (green trace) rolls off with the 12dB/octave slope typical of a sealed enclosure below 200Hz, which is higher than the specified 80Hz. The black trace below 200Hz in fig.3 is the complex sum of the three nearfield responses; it peaks dramatically between 70 and 120Hz, with a sharp rolloff below 40Hz. I note that while Ken Micallef didn't remark on the NEAT's low frequencies being boomy, he several times referred to its bass being "soft." With the Iota Alpha's lack of bass extension, it needs to be used relatively close to the wall behind it to get enough low-frequency weight, as KM found.


Fig.3 NEAT Iota Alpha, anechoic response on tweeter axis perpendicular to baffle at 50", averaged across 30° horizontal window and corrected for microphone response, with nearfield responses of midrange unit (green), woofer (blue), port (red), plotted in the ratios of the square roots of their radiating areas, and complex sum of the nearfield responses plotted below 300Hz.

Higher in frequency in fig.3, the Iota Alpha's response is even overall, with many small peaks balanced by small suckouts and the tweeter rolling off sharply above 15kHz or so. However, the narrow peak just above 3kHz raised my eyebrows, and may well correlate with KM's having noticed an occasional nasality.

Fig.4 shows the NEAT's lateral dispersion, referenced to the tweeter-axis response: the off-axis differences on the midrange unit's side of the baffle are shown to the rear, those on the tweeter side's to the front. As is to be expected with two drive-units mounted side by side, a suckout develops in their crossover region to the speaker's sides—this appears to be set at 2.75kHz rather than the specified 5kHz—more on the midrange unit's side than on the tweeter's. This suggests that the mirror-imaged Iota Alphas be set up with the tweeters on their inside edges. Though the reflections from the room's sidewalls will thus have insufficient energy between 2 and 4kHz, this might work against the audibility of that on-axis peak in the presence region. The tweeter has very limited dispersion in the vertical plane (fig.5); to get a full measure of top-octave energy, you should sit within a ±5° window centered on the tweeter axis.


Fig.4 NEAT Iota Alpha, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis on midrange side, reference response, differences in response 5–90° off axis on tweeter side.


Fig.5 NEAT Iota Alpha, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

Looking at the NEAT's performance in the time domain, its step response on the tweeter axis (fig.6) reveals that all three drive-units are connected in positive acoustic polarity, with the tweeter's output leading that of the midrange unit and woofer. There are some ripples in the decay of the midrange unit's step that the Iota Alpha's cumulative spectral-decay plot (fig.7) reveals to be associated with that on-axis peak just above 3kHz. However, while the initial decay of the speaker's sound is relatively clean (other than at 3.24kHz), several other lower-level ridges of delayed energy are visible in the treble.


Fig.6 NEAT Iota Alpha, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).


Fig.7 NEAT Iota Alpha, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

KM loved how this attractive little speaker sounded, and its shape and small size make it domestically very friendly; however, I was disappointed by its measured performance.—John Atkinson

NEAT Acoustics Ltd.
US distributor: High Fidelity Services
2 Keith Way, Suite 4
Hingham, MA 02043
(781) 987-3434

mrkaic's picture

As far as I know, this is the first review of Neat speakers that includes measurements. I wonder why.

To my knowledge Neat designs their speakers mostly by ear. This approach does not seem very scientific to me and the poor measurements here are likely the outcome of this process.

I had a pair of Neats, but sold them when I could not find any reviews that included measurements (there was a lot of subjective reviews, but I don't care about those). I simply cannot trust equipment that is not thoroughly measured and it seems that I made the right decision.

Scliff's picture

It's a shame to be so hung up on something so irrelevant as measurements.
If I like the way a component sounds, that's all I need or care about.

mrkaic's picture

It is a shame to be so hung up on something so irrelevant as subjective impressions. If I like the way a component measures, that's all I need or care about.

johnnythunder's picture

Bad food may measure well but may taste like shit. A $5 dollar bottle of wine may measure better than a $50 bottle but tastes like shit. You can have your Consumer Reports level of audio quality but most of us will be very happy listening first and worrying about measurements later. Stereophile is a perfect blend of sometimes corroborating the sound quality of a component based on measurements or telling you to ignore it. We are human beings listening to art. The essence of that is subjective. To deny it or to knock it in others is folly.

mrkaic's picture

Pompous and Rigid?! Is that supposed to refer to me? It is sad that you cannot refrain from insulting me because we don't agree.

Anton's picture

That is the strangest post I have ever seen.

"I had a pair of Neats, but sold them when I could not find any reviews that included measurements (there was a lot of subjective reviews, but I don't care about those). I simply cannot trust equipment that is not thoroughly measured and it seems that I made the right decision."

If, by chance, you happened by them while your system was on, how did you think they sounded?

mrkaic's picture

That is the strangest post I have ever seen.

What a compliment, many thanks. :)

But seriously, I did listen to them and did not like the sound. That is why I started looking for measurements. After not finding any, I ditched the Neats and never looked back.

Anton's picture

You didn't like what you heard, so why would measurements matter?

What if you had liked them, but didn't like the measurement?

Your ears don't rule?

mrkaic's picture

What if you had liked them, but didn't like the measurement?

I would get rid of them, of course. I would feel victimized by poor engineering and/or manufacturing. A component that does not measure well has no place in my home.

Your ears don't rule?

No, please see the answer above.

Pedro's picture

Most magazines don't take measurements of gear they review like Stereophile does, so it's hardly a surprise that this is the first review of these speakers with scientific measurements. But the same can be said about loads of gear, I'm sure...

mrkaic's picture

I agree, measurements are hard to find. I suppose some of the reasons might be cost, lack of expertise by reviewers, or resistance by subjectivist reviewers who seem to be the ruling class of the audio world.

Pedro's picture

Most magazines are just snake oil sellers. Without measurements and any kind of scientific approach they can sell everything they want, including stupid stuff like very expensive cables (even directional ones - ahaha) and so forth.

avanti1960's picture

the complete story of how a speaker will sound but they are hardly irrelevant, especially measured frequency response.
That +5db peak at 100Hz is something that turns me off because I know what it sounds like.
Since this speaker was especially sensitive to room position it would have been interesting to see response plots at some different positions, perhaps getting rid of that peak (if possible).

hhi92010's picture

This looks Old School, I like it!

romath's picture

You wrote: 1) "But once the Iotas were fully broken in, they ended up 14" from the front wall and 95" from the listening chair in my larger room..." and
2) "Moving the Iota Alphas into my nearfield rig, I placed the speakers 12" from the front wall and 85" from my listening chair..."

85", i.e., 7'1" is near field?? You've got to be kidding. The Quad (active) speakers on my desktop, an arm's length away, are near field. And really, other than the room and associated electronics, what makes 7'1" and 7'9" fundamentally different? Very strange.

corrective_unconscious's picture

I'd like to have some definitive reason for it to do so, as a matter confidence in the design staff.

My hearing can vary hour to hour, just as my resting pulse, my attention span, my visual acuity, my lucidity, my testosterone levels, my mood, my digestion, and so on, can. Having basic measurements, especially ones that look at least within the realm of standard, can provide a nice baseline for any subjective impressions. An example is "bad" pair matching over a limited frequency range - measurements will find that flaw faster than my ears will in most instances, I'm sure.

will1's picture

With about 30 hours of run in (Neat recommend 200) and going straight to the positioning suggested here I can't wipe the smile off my face. Powered by a Naim Nap100 and a Cambridge Azur 851n I challenge anyone to find a more enjoyable listen for the money. The mid range is a joy and the treble is stunning. You can rattle the walls but still enjoy at a sensible volume if you have neighbors.

steve59's picture

I heard these speakers at axpona 2018 and really liked what i was hearing. Nothing wrong with a speaker measuring good as long as it sounds good.