REVIEW / MEASUREMENTS: (Anthony) Gallo Acoustics A'Diva Ti (~2005) & Nucleus Micro Speakers (~2000).

Hey ladies and gents, let's switch from discussing headphones this week and have a look and listen at some speakers.

You've probably seen speakers like the ones above over the years. These are the "iconic" Gallo Acoustics A'Diva Ti speakers from the UK. These specific ones are probably something like 16 years old and the 5" diameter A'Diva orb (with 3" driver) is in fact the larger of the 2 speakers from Gallo we'll be talking about today.

Here's the smaller 4" diameter (also 3" driver) little brother - the Nucleus Micro. Note that this is the "non-Ti" version which is from the previous generation, made around year 2000 with presumably a different driver. Unlike the stainless steel protective grille of the A'Diva, the fabric grille is easily removed for photography:

Since I didn't have both speakers for testing at the same time, unfortunately, I could not take a picture side-by-side to show size comparisons.

In hand, they feel very well made. Solid sealed metal balls weighing about 1.5kg (3.3lbs) for the A'Diva Ti and just under 800gm (~1.8lbs) for the Nucleus Micro.

The larger A'Divas sold for around CAD$300 back in 2005 as you can see on the box (with an on-sale price of CAD$250):

Let's see, this works out to about CAD$350 (~US$290) with inflation today for each of the A'Diva speakers. Certainly not cheap for a pair around US$600. I see that indeed this 6Moons review of the A'Diva Ti listed the price back in 2005 as US$275 each and the Nucleus Micro was a bit less at around US$200 each.

Notice in the picture above how they included a rubber "O-ring" to put under the speaker to prevent the sphere from rolling off your table.

Here's what the back of the speakers looks like. We see the multi-way binding posts that accept standard banana plugs as well as spades and bare wires. They are a little close so one would not want huge wires/connectors plugged in:

A'Diva Ti, rear.

Nucleus Micro, rear.

Notice the single screw mounting hole that you can use to attach to a stand or wall mount (the hole below the binding posts). If you're using the O-ring on a table and given their light weight, be careful with thick speaker cables! It can be a balancing act using just 14AWG cables as I did. The last thing you want is for the metal ball to roll off a table or land on something like hardwood or tile flooring! 

Let's have a look at the impedance and phase graphs for these speakers:

As a single driver, we basically see the main resonance frequency and a gradual increase in impedance into higher frequencies as a result of inductance. For the A'Diva Ti, resonance frequency is around 150Hz and the Nucleus Micro, it's higher up at 230Hz.

Minimum speaker impedance is indeed almost exactly 8Ω as specified by the company; we can see that the EPDR can dip down to a 5Ω equivalent for both. Other than the difference between drivers themselves, the change in the resonance frequency is also a result of the different enclosures - as expected, the larger A'Diva Ti has a lower resonance frequency.

Let's now have a peek at the 2.83V signal sweep at 1m for sensitivity of these orbs:

I think both the A'Diva Ti and Nucleus Micro are about the same rated sensitivity based on the manufacturer which is what I found. Taking an average amplitude of the gated frequency response from 500Hz to 7kHz, I got a sensitivity of 88dB/2.83V/m with the A'Diva Ti and a slightly lower 86.5dB/2.83V/m for the Nucleus Micro. I believe the official specs listed both as somewhere around 88dB/W/m. Certainly not high sensitivity speakers, but not bad for a single driver.

The graphs above provide a preview into the gated on-axis frequency response which as you can see is reasonably flat between 500Hz to 7kHz for both these speakers.

Okay, let's put the speakers up on the qSpin rig and capture some "CTA-2034-inspired" graphs to get a better look!

Little Gallo Nucleus Micro ready to go for a (q)Spin...

I think it goes without saying that the appearance of these speakers is a selling point. As such, all measurements will be with the grille in place. Let's use the 50dB/dec aspect ratio with 50dB Y-axis as standard.

Well... Clearly these are the most bass-limited speakers I have measured to this point. If we look at the larger A'Diva Ti, -6dB from 1kHz is around 105Hz. For the smaller Nucleus Micro, we're looking at -6dB around 200Hz. Sure, you could put these against a wall for bass reinforcement, but IMO that would still not be enough. Clearly, these, especially the Nucleus Micro simply must be paired with a woofer/sub to reproduce a more complete frequency response.

Notice that both speakers have a high frequency extension to around 15kHz, beyond which it drops off quickly. For the Nucleus Micro, there are quite a number of resonant "bumps" throughout the "presence" and "brilliance" regions with major peaks at 7.5 and 12kHz. The A'Diva Ti particularly shows strong cone break-up behaviour (due to non-pistonic movement creating strong resonances) from 8-15kHz just before the abrupt frequency response collapse. There's also a notable 1.5kHz resonance in an otherwise relatively smooth mid-range listening window response with the A'Diva Ti.

Directivity indices show progressive "beaming" into the high frequencies from the single driver. It looks reasonably smooth until irregularity above 7kHz (again, likely due to cone break-up).

Here's a look at the directivity polar maps for the 2 speakers; horizontal and vertical planes are symmetrical due to the shape so I'll just show the horizontal measurements +/-180°.

Clearly not the most symmetrical looking directivity polar maps I've measured. In particular, the Nucleus Micro got a little nasty and unpredictable up in the higher frequencies beyond the cone's comfort zone. Listening to these speakers within +/-30° would be prudent.

Shifting to the time domain, let's look at the step response and waterfall plots for each speaker:

It's a simple non-crossover, single-driver speaker as shown in the step response pattern. Note that the step response starts at 0µs (the slight negative deviation before that is due to a linear phase filter of the miniDSP UMIK-1 microphone sampling at 48kHz).

The waterfall CSD shows roughness higher up but otherwise it's a steep waterfall pattern without resonance persisting beyond ~3ms. As usual for my speaker measurements, I've used a 25dB dynamic range from the floor to the cursor level correlating with approximately the lower end of the frequency response.

We can have a look at speaker linearity - that is, how loud the output from the speakers track the target amplitude as we increase the voltage:

Notice that both measurements are anchored relative to 85dB SPL as the 0 point. The A'Diva managed quite well but notice that the little Nucleus Micro showed more error as it went louder beyond 94dB SPL. This suggests that one should not try pushing the volume too high with these little speakers and we might also see significantly more distortion.

Switching now over to distortion characteristics then, here's the THD across the audible frequencies at 85dB SPL at 1m amplitude level:

On average beyond the bass frequencies, I'm consistently seeing a bit more distortion with the larger A'Diva Ti than the little Nucleus into mids and upper frequencies. Much of the harmonic distortion is 3rd order which is generally inaudible. I found this to be consistent with a few repeated measurements. -40dB is 1% where the reference line is. Be mindful of the weak bass reproduction. For example, below 200Hz as the frequency response rolls off with the little Nucleus Micro, distortion rises substantially.

Using an intermodulation test with 300 + 1300Hz sine multitone, we can examine what happens with distortion as we increase the amplitude from 60 to 90dB SPL.

Apologies for the ultra-high resolution of the A'Diva Ti IMD FFTs above; went a bit overboard with the graph size.

Basically, we can see that when we get above 80dB SPL and definitely by 90dB SPL, the distortions worsen. Like the THD graph above, it looks like the A'Diva Ti has a bit more distortion even at 80dB SPL compared to the smaller Nucleus Micro. As for the Nucleus Micro, that jump from 80 to 90dB SPL increases distortion quite a bit more, perhaps tracking with the deviation from linearity.

As you can see in the picture at the very top of this post, I borrowed both a matte black and matte white-colored A'Diva Ti with quite different serial numbers. Here's a frequency sweep to check for consistency between speakers:

We can see that both speakers performed equivalently. Likewise we can have a look at the 2 white Gallo Nucleus Micros I borrowed:

I can't see any serial numbers on the white cardboard boxes they come with nor on the speakers themselves. Again, the "channel balance" looks good with a bit more deviation in the higher frequencies >10kHz. Overall this speaks well to the manufacturing quality control and driver matching.

 

Subjective sound quality...

As usual, I listened to these speakers before running the measurements. Here's one of the little Nucleus Micros on my computer workstation desktop:

Notice the tiny size compared to my Emotiva B1+ bookshelf speaker.

I put the larger A'Diva Ti in my sound room for a listen as well - here's a shot with the RME ADI-2 Pro FS R Black Edition and my Raspberry Pi 4 "Touch" streamer in the background:

Since I'm using bi-wirable banana plugs, note an unused plug peeking from behind.

Admittedly the positioning of the A'Diva Ti isn't perfect. I actually could not mount these well on typical speaker stands because they're small and my heavy DIY cable would easily pull them off so I made do with putting them on either side of my equipment rack for a listen.

I listened to the Nucleus Micro on my computer workstation for about an evening and likewise the A'Diva in the soundroom another night. I used a playlist of "audiophile" songs (many listed in my Soundroom Article).

Basically what I heard were speakers with limited bass, slight mid-range accentuation (Nucleus Micro more than A'Diva), and rather uneven upper frequencies. On the track "Moonlight on Spring River" (The Dali CD, Vol 3), whole bass parts were missing with the Nucleus Micro and if you didn't know the music, might have no clue of what's gone! With the A'Diva Ti there was at least a hint that one is missing something down below 100Hz.

They do a good job with female vocals (like Jennifer Warnes or Ella Fitzgerald), but male voices like Nat King Cole (listening to Cole En Español - Greatest Hits) missed out on his usual lower frequency fullness. It sounded like Cole was singing with just his head and neck in the room, a bit hypernasal, missing the warmer tones of the "chest voice". 

I'm not sure how best to describe the treble. Certainly the high frequencies are present but they don't sound as refined nor as "airy". I've mentioned before the little bell/triangle sound on The Bangles' "Eternal Flame" (Everything) a few months back in the Realistic Minimus 7 measurements. Like with those speakers, this sound did not seem anchored well in the soundstage and the decay was a bit "nervous", not trailing off with composure as one would hear with better speakers. Although I didn't specifically hear any issues in my listening sessions, be mindful of the treble resonances above 7-8kHz which may draw attention to themselves if you have music with quite a bit of high-frequency content.

Sound clarity was generally good. John Renbourn's guitar work (The Guitar of John Renbourn) sounded "fast", precise, if a bit sonically uninspired without more low-end presence overall (imagine "Seven Up" without decent bass impact on those drums!). While I did not put them in the soundroom with ideal separation distance, the soundstage was pretty good in terms of width and conveying the sense of depth - but one cannot ignore the frequency domain issues as paramount.

Summary...

Tiny white Gallo Nucleus Micro in the living room flanking 55" TV. Better soundstage and overall sound than the tinny TV speakers at least. I suspect these days, a decent sound bar like the Yamaha SR-B20A would be quite effective.

I find these speakers historically interesting because they came out at the turn of the 21st Century. Back in those days (Y2K, 20 years ago), home audio was experiencing a drive towards the surround sound home theater experience. It was a time when Dolby Digital discrete multichannel (AC3) had become inexpensive enough to integrate into consumer-level receivers and DTS was also making its way into homes. Furthermore, SACD and DVD-A were promising "high-resolution" surround as well to entice the audiophile (because they knew "hi-res" stereo barely sounds different than CD even if marketing hype still touted bit-depth and big samplerates!).

Small speakers like these would have been of interest as "lifestyle products" that could be placed out of the way and the audio press would also have been following these Industry changes as there could be money to be made if multichannel took off with audiophiles and mainstream consumers alike.

As "lifestyle products", these little speakers appear to be well made. These days, I see that Gallo Acoustics has added a "bespoke colour service" to spice up the look of these orbs further with custom Pantone and RAL color choices. My wife thought they looked "cute" sitting on my computer desktop but it was obvious to her that the sound was lacking compared to the less expensive Emotiva Airmotiv B1+. I think it's interesting reading the positive "audiophile" reviews written in 6Moons, Part-Time Audiophile, SoundStage!, and CNet in retrospect now that I have these here to listen and think about what was said. The Sound+Vision review is the only one I've seen with measurements of the A'Diva Ti with their -6dB bass roll-off point at 103Hz equivalent to what I also measured.

Obviously, with a small form factor like this there need be no big surprises around the kind of sound these produce. These are small, single-driver, closed, passive dynamic speakers and the results conform to the rules of physics with limited bass extension and frequency range the driver is "comfortable" with reproducing. Compared to good 2-way bookshelves or floorstander speakers, while one might be "surprised" that a speaker of this size could produce sound at a reasonable volume, it's simply not going to be "room filling" in any special way.

Yeah, the company literature will no doubt focus on the single-diver, crossover-less design as being time coherent, a "point-source", and the round shape would reduce baffle diffraction effects. In the big picture, these are IMO minor benefits in the face of poor bass performance if used alone. If we took the high and low -6dB points on the measurements as the realistic frequency limits to these speakers, the A'Diva Ti would have a frequency range of 100Hz to 15kHz while the Nucleus Micro covers 200Hz to 14kHz. Since the content between 100-200Hz is rather important (you don't need to be a Golden Ear to hear this ;-), between the two, the A'Diva Ti sounds significantly better even though interestingly, I found that it had a bit more harmonic distortion in the measurements (both black and white speakers showed this tendency).

I would obviously insist on pairing these with bass/sub-woofers (especially the Nucleus Micro) if you really want the sound to resemble anything like "high fidelity". Back in the day, these small speakers were often paired with the Gallo TR-1 sub with 10" driver, 100Wrms "active sub" with claimed frequency response of 20-180Hz. I think my friend AudioPhil whom I borrowed the little Nucleus Micros from has one of these and maybe at some point I'll have a listen to the combination of these "satellite" speakers integrated with the matching bass/sub. My concern especially with the Nucleus Micro is that the limited low-frequency performance requires the woofer/sub to fill in too much of the content essentially to 200Hz and thus results in easy localization of the bass module.

Even as surround speakers, I would prefer satellites having reasonable frequency response down to 80-100Hz. The only exception I would make would be Atmos add-on height effect channels (like the ELAC Debut 2.0 A4.2 previously reviewed/measured).

These days, one could still buy updated versions of these speakers. Presumably there have been improvements to the drivers although specs like frequency response have not changed all that much from what I see. The Gallo Micro is available for around US$200 still. The newest versions come with the "SE" designation and have a 4Ω impedance rating rather than 8Ω - the Micro SE and A'Diva SE.

A big thanks to linnrd for lending me the A'Diva Ti and AudioPhil for the Nucleus Micro to test out!

--------------------

If you like binaural audio, have a listen to Jean-Michel Jarre's new release Amazônia (binaural mix) - rainforest sounds, ambient synth, subtle tribal chants. This is basically a soundtrack for a photo exhibit. Strictly for those who like "sounds" rather than "music" as you'll be disappointed if you're waiting for a coherent melody!

Find a quiet space, put on some comfy headphones (personally, large circumaural ones like my modded Dekoni Blues are the only way to go ;-), close your eyes, allow your mind to be swept away in the soundscape of the 52-minute exotic trip.

Alright friends... Into June we go. Hope you're all doing well and enjoying some great music!