Barefoot Footprint 01 Review (Studio Monitor)

[AndreaT]

This is a review and detailed measurements of the Barefoot Footprint 01 powered studio monitor (speaker). It is on kind loan from a member in Canada who sent it to me as fair bit of expense. The Footprint 01 costs US $3,950 a pair. Seems likes distribution is a bit limited as I did not find it at some of the major online retailers.

The Footprint 01 differs from its competitors in a number of ways starting with the "PA" enclosure material:

View attachment 130597

It is super dense material though so other than looking industrial, it seems like a decent choice.

Another departure is dual side-mounted woofers which are crossed at 250 Hz:
View attachment 130599

This is a common technique in subwoofers and larger tower speakers to take advantage of vibration cancellation. It worked as combined with the dense cabinet, I could only feel some vibration at the center of the cabinet and the back metal side only.

Note that despite being an active DSP speaker, that only applies to the woofer to mid-range transition (and bass response). The midrange and tweeter are driven by one amplifier so the crossover is passive! Seems like the wrong tradeoff to me as I rather get the midrange to tweeter right than the woofers which get messed with in the room anyway (so need external DSP for correction). But maybe they know something we don't.

Here is the back panel which departs yet again from the norm:
View attachment 130600

Notice the absence of universal dip switches to tailor the tonality of the speaker. It is replaced with a rotary control (not shown) that mimics a few other speakers/target responses (including distortion???). We also lack digital inputs which at this price range should probably be there.

----
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% except for around 4 kHz where it reached about 2% error.

Testing temperature was around 65 degrees F.

Reference axis for measurements was the LED light just above the tweeter as the manual instructs. I actually ran it both at this setting and center of the tweeter and there was no difference to speak of in the measurements.

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.

Barefoot Footprint 01 Measurements
As usual we start with our spin frequency response measurements:

View attachment 130601

As we see, the passive crossover is not optimal with a prominent resonance at 1.3 khz surrounded by other roughness. Company literature from what I recall talks about uniformity of dispersion but that clearly is not the case with the tweeter getting beamy proportional to frequency to far greater level than I have seen in many speakers much less monitors. This directivity loss is seen in company measurements as well but an entirely different view is shown of the on-axis response:

Their vertical scale is zoomed in even more than mine yet they show a remarkably flat response. The explanation may be them using a warehouse with a speaker raised from the floor for measurements which most likely includes some manual tweaks.

Our early window reflections (for far field listening) shows the impact of the drooping side radiation from the tweeter:
View attachment 130603

Combining both, far-field predicted in-room response doesn't look good:

View attachment 130604

Result will be somewhat boomy sound with some strangeness around 1 to 3 kHz.

Beamwidth plot shows how the woofer is getting directional at 250 Hz before hand off to the mid-range which is not:

View attachment 130606

And of course the tweeter's beam width gets narrower with frequency in textbook manner:
View attachment 130605

The vertical directivity is no better or worse than any other:

View attachment 130607

Near-field response of each driver shows a mid-range that doesn't have a flat response which a DSP could have fixed:

View attachment 130608

I was surprised bass distortion was not better than it is:

View attachment 130612

View attachment 130613

Waterfall shows some resonances:

View attachment 130609

Barefoot Footprint 01 Listening Tests
I assumed the inclusion of the dual beefy woofers would make for a good far-field listening so I placed the Footprint 01 on my usual stand in my 2-channel listening setup and started to listen. I was mistaken. There was little that I liked about the sound. It was somewhat boomy and I did not like the sound in mid-range. I brought out EQ tools and corrected what I could but the end, I was not satisfied at all. I was also surprised that I could get the clipping light to come on before a level that I thought was too high. Fortunately it was not indicative of massive distortion so more loudness could be had.

A couple of times I heard some spatial effects that were unusual. Hard to describe but the background male vocals seemed to come from behind the front baffle. My guess is that it may be due to the side woofers playing these notes due to their high crossover point. I put my ear in front of the woofers though and could not confirm this. So take it for what it is as the saying goes.

I brought the speaker to my workstation area but it was too big to put on the side of my monitor. So I put it on top of my test instrument rack to my right. 5 seconds of playback showed remarkably good sound! Track after track was enjoyable to listen to with the EQ I had developed in the fair field:

View attachment 130611

One big difference here was listening level so maybe distortion was playing a role. Another major difference is activation of room modes which would be wildly different in the new setup than old. And maybe he effect of the side-firing woofers was different.

Conclusions
The Barefoot Footprint 01 charts its own way with a studio monitor that is not architected the same as its competitors. Some of these departures are working in their favor, others are not. I suspect some of the flaws here is their improper measurement scheme that is not allowing them to see the flaws in the execution of this speaker. $1000 spent on an NFS measurement would do them wonders instead of using semi-DIY schemes as they seem to be deploying.

Anyway, near-field performance is very good with a bit of EQ. Far-field use is more questionable and likely requires proper in-room measurements to correct for all bass modes and lots of time spent on positioning due to poor directivity.

I am going to put the Barefoot Footprint 01 on my recommended list for near-field listening.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150

Great review. Could the woofers dsp, likely optimized to extend first two octaves frequency response in what seems a sealed design, and less than stellar woofer choice be responsible for the elevated distortion below 100 Hz? Are they trying to prettify the woofers beyond their electro-mechanical limitations?

 

[H-713]

FWIW, it's almost certain that the reason they've got an active crossover (and / or DSP) on the woofer, with a passive on the tweeter / midrange, is because a passive woofer crossover is considerably more expensive than a passive tweeter / midrange crossover since it needs to handle a lot more power. It's not because it's better.

I suspect that this is a very costly speaker to manufacture.

 

[FeddyLost]

Are they trying to prettify the woofers beyond their electro-mechanical limitations?

Most probably this enclosure is too small for these woofers and powers that they have to handle at high SPL.
With DSP they have flat LF response, but pressure and all the consequences still there.

 

[Jas0_0]

The guy who sold me my Genelecs said he was upgrading to Barefoots.

It would probably be mean of me to send him this review.

 

[Pearljam5000]

The guy who sold me my Genelecs said he was upgrading to Barefoots.

It would probably be mean of me to send him this review.

Lol
It would be mean if he already bought the Barefoots

 

[Χ Ξ Σ]

The guy who sold me my Genelecs said he was upgrading to Barefoots.

It would probably be mean of me to send him this review.

Funny how the guy who sold me my Genelecs upgraded to ATC. What can I say, I wish more sellers were like that.

 

[YSC]

Funny how the guy who sold me my Genelecs upgraded to ATC. What can I say, I wish more sellers were like that.

well, that's called mutually beneficial!

 

[thewas]

While this is true, it's far worse with these than it is with other speakers I've owned in the same room which certainly had enough extension to get down that low (it's around 77-78hz, an Eb2), all of which were front firing.

A partial possible reason could be the different location of the woofers, which for example can coincide with the distance of 2 or more boundaries.

 

[Maiky76]

This is a review and detailed measurements of the Barefoot Footprint 01 powered studio monitor (speaker). It is on kind loan from a member in Canada who sent it to me as fair bit of expense. The Footprint 01 costs US $3,950 a pair. Seems likes distribution is a bit limited as I did not find it at some of the major online retailers.

The Footprint 01 differs from its competitors in a number of ways starting with the "PA" enclosure material:

View attachment 130597

It is super dense material though so other than looking industrial, it seems like a decent choice.

Another departure is dual side-mounted woofers which are crossed at 250 Hz:
View attachment 130599

This is a common technique in subwoofers and larger tower speakers to take advantage of vibration cancellation. It worked as combined with the dense cabinet, I could only feel some vibration at the center of the cabinet and the back metal side only.

Note that despite being an active DSP speaker, that only applies to the woofer to mid-range transition (and bass response). The midrange and tweeter are driven by one amplifier so the crossover is passive! Seems like the wrong tradeoff to me as I rather get the midrange to tweeter right than the woofers which get messed with in the room anyway (so need external DSP for correction). But maybe they know something we don't.

Here is the back panel which departs yet again from the norm:
View attachment 130600

Notice the absence of universal dip switches to tailor the tonality of the speaker. It is replaced with a rotary control (not shown) that mimics a few other speakers/target responses (including distortion???). We also lack digital inputs which at this price range should probably be there.

----
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% except for around 4 kHz where it reached about 2% error.

Testing temperature was around 65 degrees F.

Reference axis for measurements was the LED light just above the tweeter as the manual instructs. I actually ran it both at this setting and center of the tweeter and there was no difference to speak of in the measurements.

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.

Barefoot Footprint 01 Measurements
As usual we start with our spin frequency response measurements:

View attachment 130601

As we see, the passive crossover is not optimal with a prominent resonance at 1.3 khz surrounded by other roughness. Company literature from what I recall talks about uniformity of dispersion but that clearly is not the case with the tweeter getting beamy proportional to frequency to far greater level than I have seen in many speakers much less monitors. This directivity loss is seen in company measurements as well but an entirely different view is shown of the on-axis response:

Their vertical scale is zoomed in even more than mine yet they show a remarkably flat response. The explanation may be them using a warehouse with a speaker raised from the floor for measurements which most likely includes some manual tweaks.

Our early window reflections (for far field listening) shows the impact of the drooping side radiation from the tweeter:
View attachment 130603

Combining both, far-field predicted in-room response doesn't look good:

View attachment 130604

Result will be somewhat boomy sound with some strangeness around 1 to 3 kHz.

Beamwidth plot shows how the woofer is getting directional at 250 Hz before hand off to the mid-range which is not:

View attachment 130606

And of course the tweeter's beam width gets narrower with frequency in textbook manner:
View attachment 130605

The vertical directivity is no better or worse than any other:

View attachment 130607

Near-field response of each driver shows a mid-range that doesn't have a flat response which a DSP could have fixed:

View attachment 130608

I was surprised bass distortion was not better than it is:

View attachment 130612

View attachment 130613

Waterfall shows some resonances:

View attachment 130609

Barefoot Footprint 01 Listening Tests
I assumed the inclusion of the dual beefy woofers would make for a good far-field listening so I placed the Footprint 01 on my usual stand in my 2-channel listening setup and started to listen. I was mistaken. There was little that I liked about the sound. It was somewhat boomy and I did not like the sound in mid-range. I brought out EQ tools and corrected what I could but the end, I was not satisfied at all. I was also surprised that I could get the clipping light to come on before a level that I thought was too high. Fortunately it was not indicative of massive distortion so more loudness could be had.

A couple of times I heard some spatial effects that were unusual. Hard to describe but the background male vocals seemed to come from behind the front baffle. My guess is that it may be due to the side woofers playing these notes due to their high crossover point. I put my ear in front of the woofers though and could not confirm this. So take it for what it is as the saying goes.

I brought the speaker to my workstation area but it was too big to put on the side of my monitor. So I put it on top of my test instrument rack to my right. 5 seconds of playback showed remarkably good sound! Track after track was enjoyable to listen to with the EQ I had developed in the fair field:

View attachment 130611

One big difference here was listening level so maybe distortion was playing a role. Another major difference is activation of room modes which would be wildly different in the new setup than old. And maybe he effect of the side-firing woofers was different.

Conclusions
The Barefoot Footprint 01 charts its own way with a studio monitor that is not architected the same as its competitors. Some of these departures are working in their favor, others are not. I suspect some of the flaws here is their improper measurement scheme that is not allowing them to see the flaws in the execution of this speaker. $1000 spent on an NFS measurement would do them wonders instead of using semi-DIY schemes as they seem to be deploying.

Anyway, near-field performance is very good with a bit of EQ. Far-field use is more questionable and likely requires proper in-room measurements to correct for all bass modes and lots of time spent on positioning due to poor directivity.

I am going to put the Barefoot Footprint 01 on my recommended list for near-field listening.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150

Hi,

Here is my take on the EQ.

The raw data with corrected ER and PIR:

Score no EQ: 6.0
With Sub: 7.1

Spinorama with no EQ:

• Not that flat
• bad (for this price) in the 1 - 3k range
• too much bass
• Directivity not great

Directivity:
Better stay at tweeter height
Horizontally, it looks like this speaker must be listened to off axis about 10deg will help dosing the upper range, put them parallel to each others?

EQ design:

I have generated two EQs. The APO config files are attached.

• The first one, labelled, LW is targeted at making the LW flat
• The second, labelled Score, starts with the first one and adds the score as an optimization variable.
• The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose.

Score EQ LW: 6.8
with sub: 8.0
LF extension contribution is higher than usual as opposed to smooth response hence the lowish Sub score...

Score EQ Score: 7.2
with sub: 8.2

Barefoot Footprint 01 APO EQ LW 96000Hz
May202021-172458

Preamp: -1.4 dB

Filter 1: ON PK Fc 64.5 Hz Gain -2.4 dB Q 1.4
Filter 2: ON PK Fc 146 Hz Gain -2 dB Q 0.87
Filter 3: ON PK Fc 397 Hz Gain 0.6 dB Q 1.78
Filter 4: ON PK Fc 709 Hz Gain -1.98 dB Q 1.83
Filter 5: ON PK Fc 1399 Hz Gain -3.77 dB Q 5.33
Filter 6: ON PK Fc 3000 Hz Gain -2.1 dB Q 2.83
Filter 7: ON PK Fc 10010 Hz Gain 1.41 dB Q 1.7

Barefoot Footprint 01 APO EQ Score 96000Hz
May202021-172256

Preamp: -1 dB

Filter 1: ON PK Fc 66.5 Hz Gain -2.35 dB Q 1.4
Filter 2: ON PK Fc 150 Hz Gain -2 dB Q 0.87
Filter 3: ON PK Fc 380 Hz Gain 0.84 dB Q 2
Filter 4: ON PK Fc 700 Hz Gain -1.98 dB Q 1.83
Filter 5: ON PK Fc 1406 Hz Gain -3.77 dB Q 4.67
Filter 6: ON PK Fc 2722 Hz Gain -2.85 dB Q 2.33
Filter 7: ON PK Fc 10020 Hz Gain 1 dB Q 1.95

Spinorama EQ LW

Spinorama EQ Score

Zoom PIR-LW-ON

Regression - Tonal

Radar no EQ vs EQ score
Nice improvements

The rest of the plots is attached.

@pierre
The score I calculate with your EQ is 7.0 not 7.5
plus you opted for boosting the through around 1900Hz
Filter 2: ON PK Fc 1885 Hz Gain +4.23 dB Q 7.02
I would not recommend it, it does significantly improve the score but another unit may be different (manufacturing tolerances) and this might not be robust...

 

[Spocko]

Hi,

Here is my take on the EQ.

The raw data with corrected ER and PIR:

Score no EQ: 6.0
With Sub: 7.1

Spinorama with no EQ:

• Not that flat
• bad (for this price) in the 1 - 3k range
• too much bass
• Directivity not great

View attachment 130847
Directivity:
Better stay at tweeter height
Horizontally, it looks like this speaker must be listened to off axis about 10deg will help dosing the upper range, put them parallel to each others?
View attachment 130855
View attachment 130854
EQ design:

I have generated two EQs. The APO config files are attached.

• The first one, labelled, LW is targeted at making the LW flat
• The second, labelled Score, starts with the first one and adds the score as an optimization variable.
• The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose.

Score EQ LW: 6.8
with sub: 8.0
LF extension contribution is higher than usual as opposed to smooth response hence the lowish Sub score...

Score EQ Score: 7.2
with sub: 8.2

Barefoot Footprint 01 APO EQ LW 96000Hz
May202021-172458

Preamp: -1.4 dB

Filter 1: ON PK Fc 64.5 Hz Gain -2.4 dB Q 1.4
Filter 2: ON PK Fc 146 Hz Gain -2 dB Q 0.87
Filter 3: ON PK Fc 397 Hz Gain 0.6 dB Q 1.78
Filter 4: ON PK Fc 709 Hz Gain -1.98 dB Q 1.83
Filter 5: ON PK Fc 1399 Hz Gain -3.77 dB Q 5.33
Filter 6: ON PK Fc 3000 Hz Gain -2.1 dB Q 2.83
Filter 7: ON PK Fc 10010 Hz Gain 1.41 dB Q 1.7

Barefoot Footprint 01 APO EQ Score 96000Hz
May202021-172256

Preamp: -1 dB

Filter 1: ON PK Fc 66.5 Hz Gain -2.35 dB Q 1.4
Filter 2: ON PK Fc 150 Hz Gain -2 dB Q 0.87
Filter 3: ON PK Fc 380 Hz Gain 0.84 dB Q 2
Filter 4: ON PK Fc 700 Hz Gain -1.98 dB Q 1.83
Filter 5: ON PK Fc 1406 Hz Gain -3.77 dB Q 4.67
Filter 6: ON PK Fc 2722 Hz Gain -2.85 dB Q 2.33
Filter 7: ON PK Fc 10020 Hz Gain 1 dB Q 1.95

View attachment 130846

Spinorama EQ LW
View attachment 130843

Spinorama EQ Score
View attachment 130842

Zoom PIR-LW-ON
View attachment 130844

Regression - Tonal
View attachment 130845

Radar no EQ vs EQ score
Nice improvements
View attachment 130840

The rest of the plots is attached.

@pierre
The score I calculate with your EQ is 7.0 not 7.5
plus you opted for boosting the through around 1900Hz
Filter 2: ON PK Fc 1885 Hz Gain +4.23 dB Q 7.02
I would not recommend it, it does significantly improve the score but another unit may be different (manufacturing tolerances) and this might not be robust...

View attachment 130859

Clearly a labor of love, thank you!

 

[abdo123]

No that's the cost of having one speaker measured by klippel nfs distributor.

I always wondered whether individuals can send speakers to Klippel in Germany and they would do measurements for a price.

Do you have any idea where to reach out for such services?

 

[markb]

The guy who sold me my Genelecs said he was upgrading to Barefoots.

It would probably be mean of me to send him this review.

Very similar to how I bought two pairs of Genelec 8xxx series from two different sellers, both of them were “upgrading”. I just smiled while thinking “you fools”.

Now, 5 years later, these are all 15 years old and still like new. I see I can actually sell them at a significant profit now, but have no intention of doing so at this point.

 

[FeddyLost]

The guy who sold me my Genelecs said he was upgrading to Barefoots.
It would probably be mean of me to send him this review.

Funny how the guy who sold me my Genelecs upgraded to ATC. What can I say, I wish more sellers were like that.

Very similar to how I bought two pairs of Genelec 8xxx series from two different sellers, both of them were “upgrading”

I'd like to remind that studio monitors are just one of sound engineer's tools and final reason for monitors' choise is expected profits from his works done with these monitors.
Monitors can be wrong and weird, but if mixes and masters became better/faster/easier, then upgrade is successful.
Also, attempts to apply preference scores, worked out for consumers' speakers working mid/far field for nearfield monitors is slightly wrong. Design priorities might be different as needs of target audience. Not all sound engineers prefer Genelecs.

 

[YSC]

I'd like to remind that studio monitors are just one of sound engineer's tools and final reason for monitors' choise is expected profits from his works done with these monitors.
Monitors can be wrong and weird, but if mixes and masters became better/faster/easier, then upgrade is successful.
Also, attempts to apply preference scores, worked out for consumers' speakers working mid/far field for nearfield monitors is slightly wrong. Design priorities might be different as needs of target audience. Not all sound engineers prefer Genelecs.

kind of agree and disagree on this, yea, if the upgrade make things easier then of course it is successful, but I can't understand the argument of the inaccurate speaker will make things easier to mix for X audience... since I don't recall a specific "tuning" or model of speakers are widely used enough to make mixing with particular speaker easier than an accurate one... Sure Genelec isn't the best in the world and golden standard, but it's pretty close to neutral

 

[Pearljam5000]

Genelecs are polarizing even among sound engineers,take that huge "The love hate relationship with Genelec" thread as an example.
To my ears they just sound neutral, flat and detailed, and above all i like the tonality, so i don't care what other people think

 

[thewas]

To my ears they just sound neutral, flat and detailed, and above all i like the tonality, so i don't care what other people think

Really? I have the feeling you ask in every second thread here what people thing about a Genelec vs. another monitor.

 

[sarumbear]

Genelecs are polarizing even among sound engineers…To my ears they just sound neutral, flat and detailed, and above all i like the tonality…

You are lucky that your “tonality” is neutral. For many people flat frequency response is not good “tonality” — as it should be! There’s no “tone” to hear from the speakers, they are tone-less, in other words flat!

This reminded me a story. Back in the early 70s when Julian Vereker RIP had a small shop in Salisbury, hand building amplifiers, a guy from Australia visited him. (He was to become NAIM’s first dealer.) He was critiquing the NAP250 - Linn Isobaric system, Julian used as his demo, as toneless. Julian and I were good friends. I joined Julian to “wine & dine” the guy, so to speak, during the week he stayed in the UK. In order to prove him that Hi-Fi means nothing to be added to the recorded sound, we took him to the Royal Festival Hall in london to a LSO concert. I had the exact piece the LSO was to play on an LP. We played him the record and off we went to London. After the concert we asked him what he thinks? He said “too much highs, not enough bass” — for the concert sound!

The moral of the story: Most people don’t like Hi-Fi.

 

[Pearljam5000]

You are lucky that your “tonality” is neutral. For many people flat frequency response is not good “tonality” — as it should be! There’s no “tone” to hear from the speakers, they are tone-less, in other words flat!

This reminded me a story. Back in the early 70s when Julian Vereker RIP had a small shop in Salisbury, hand building amplifiers, a guy from Australia visited him. (He was to become NAIM’s first dealer.) He was critiquing the NAP250 - Linn Isobaric system, Julian used as his demo, as toneless. Julian and I were good friends. I joined Julian to “wine & dine” the guy, so to speak, during the week he stayed in the UK. In order to prove him that Hi-Fi means nothing to be added to the recorded sound, we took him to the Royal Festival Hall in london to a LSO concert. I had the exact piece the LSO was to play on an LP. We played him the record and off we went to London. After the concert we asked him what he thinks? He said “too much highs, not enough bass” — for the concert sound!

The moral of the story: Most people don’t like Hi-Fi.

Most people don't like flat sound
What i meant is, that every instrument and voice sounded closest to reality with no coloration.
Even if the sound is "ugly" the monitor isn't colored like most people like
So... flat= perfect tonality

 

[Francis Vaughan]

Could the woofers dsp, likely optimized to extend first two octaves frequency response in what seems a sealed design, and less than stellar woofer choice be responsible for the elevated distortion below 100 Hz? Are they trying to prettify the woofers beyond their electro-mechanical limitations?

Modifying a sealed bass enclosure alignment is a well understood mechanism, it doesn't even need to be DSP. Siegfried Linkwitz (that guy again) codified what has become known as the Linkwitz Transform, which allows, from first principles, the design of filter sections that allow you define whatever bass alignment you want (within reason) for a driver in an arbitrary sealed enclosure. In many ways you end up with the bass response that driver would have had in a different (typically larger) enclosure. But there is no free lunch, the usual downside is that it requires more power. This does mean higher heating of the voice coils and higher modulation of the magnetic field in the gap, so two sources of distortion are increased in severity.
The driver used has a shorting ring that helps mitigate gap modulation, but it can only do so much. Higher price drivers tend to apply a lot of copper in the gap to help here. It may be that this is where problems are coming from.
But other sources of distortion are unaffected. In general it is a reasonable and effective approach that sees a lot of use. It is limited to active systems, or powered subs, where it sees extensive use.
What the mechanism can't do is compensate for lack of swept volume. All drivers have maximum output defined by their area and maximum excursion. Given this speaker uses two well respected if lower cost 8" Peerless drivers, the overall approach is good. But eventually you can't shift more air than the drivers can sweep, and then you hit limits. However this doesn't explain higher frequency (say above 50Hz) bass distortion. The high distortion seen at these frequencies and low outputs is a trifle puzzling.

 

[Francis Vaughan]

He said “too much highs, not enough bass” — for the concert sound!

Do you remember the piece?
I wonder what experience he had with live music. A lot of people are quite shocked the first time they hear many instruments live. Usually they are just not prepared for the impact, and often had no idea how harsh and in your face some instruments are live.

Anyone selecting a speaker for mixing or monitoring based on whether they like the sound of the speaker needs to stop and think for a moment about what they are about to do.