PMC fact.8 signature loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the PMC fact.8 signature's farfield behavior. I left the grille off for the measurements. PMC specifies the fact.8's sensitivity as 89dB/W/m; my estimated sensitivity was within experimental error of the specification, at 88.5dB(B)/2.83V/m. The fact.8's nominal impedance is specified as 8 ohms, which the solid trace in fig.1 indicates is appropriate, the impedance remaining above 8 ohms for much of the audioband. The minimum values are 5.47 ohms between 185Hz and 200Hz and 5.15 ohms at 11.3kHz. Although the electrical phase angle (dashed trace) is high at some frequencies, the impedance magnitude is also high at those frequencies. The fact.8 signature will be easy to drive.


Fig.1 PMC fact.8 signature, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

Although there are some wrinkles in the impedance traces between 100Hz and 400Hz, the enclosure seemed inert, perhaps due to the complicated internal panels that form the transmission line that loads the woofers. When I examined the vibrational behavior of the cabinet walls with a plastic-tape accelerometer, the only resonant modes I found were both high in frequency and low in level (fig.2). The cabinet is commendably quiet.


Fig.2 PMC fact.8 signature, 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).

Although PMC describes the fact.8's woofers as being loaded with an "Advanced Transmission Line," the solid trace in fig.1 doesn't look significantly different from the impedance of a conventional reflex loading, with a low-frequency saddle at what would be the tuning frequency of the port. I investigated further by examining the nearfield step responses of the woofers and the vent at the end of the line. As with a reflex design, the output of the port is in opposite polarity to that of the woofers, though the length of the line delays the vent output by several milliseconds.

The red trace in fig.3 shows the frequency-domain behavior of the PMC's vent. It does have a peak close to the frequency of the saddle in the impedance magnitude plot, but there is also a higher-level peak centered on 110Hz, the frequency of one of the wrinkles in the impedance traces. There is also a slight suckout at this frequency in the nearfield output of the woofers (fig.3, blue trace), and the woofers do have a minimum-motion notch at what appears to be the tuning frequency of the vent, 32Hz. (This is where the cones are held stationary by the back pressure from the reflex port resonance.) This graph was taken with the LF control set to "0." The "–1" and "–2" settings, respectively, reduce the level of the woofers by 2dB and 4dB between 70Hz and 200Hz and by up to 5dB and 10dB below 70Hz.


Fig.3 PMC fact.8 signature, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield responses of the woofer (blue) and ventt (red), respectively plotted below 350Hz and 480Hz.

The output of the woofers—both behave identically—is relatively even in the midrange, and it crosses over to the tweeter (green trace) at the specified 1.7kHz. The tweeter's response appears to be a little too low in level for the first octave of its passband, which might relate to KR feeling that the fact.8 was less sensitive than the specified figure. This graph was taken with the HF control set to its center position. Setting it to "+1" increased the tweeter's output level by 1dB above 6kHz; setting the control to "–1" reduced the output above 6kHz by 1dB.

I left both controls set to "0" when I examined the fact.8's farfield response, averaged across a 30° horizontal window centered on the tweeter axis (fig.4, black trace above 300Hz). A slight lack of energy between 1.5kHz and 6kHz is evident in this graph, along with a similarly slight excess of energy in the top octave. The black trace below 300Hz in fig.4 shows the sum of the PMC's nearfield woofer and vent outputs, taking into account acoustic phase and the different distance of each radiator from a nominal farfield microphone position. The usual excess of upper-bass energy due to the nearfield measurement technique, which assumes that the radiators are mounted on a true infinite baffle, ie, one that extends indefinitely in both horizontal and vertical planes, is absent. Instead, there appears to be a lack of upper-bass energy, which might correlate with KR's describing the fact.8 as having a "reduced contribution in the upper bass and low midrange." More on this aspect of the fact.8's behavior later.


Fig.4 PMC fact.8 signature, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and vent responses plotted below 300Hz.

The plot of the fact.8's horizontal dispersion, referenced to the response on the tweeter axis (fig.5), indicates that the speaker's output drops off to the sides above 10kHz. This will tend to balance some of the on-axis top-octave excess in medium-sized and large rooms. In addition, some of the missing presence-region energy on the on-axis response reappears off-axis. The contour lines in this graph are otherwise relatively even throughout the midrange and treble, which correlates with stable stereo imaging. In the vertical plane (fig.6), a suckout develops in the crossover region 15° above the tweeter axis, but the speaker's response hardly changes over a ±5° window centered on the tweeter axis, which is 38.5" from the floor.


Fig.5 PMC fact.8 signature, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.


Fig.6 PMC fact.8 signature, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–15° below axis.

The red trace in fig.7 shows the PMCs' spatially averaged response in my room with the level controls set to "0." (This trace is generated by averaging 20 spectra, taken for the left and right speakers individually using a 96kHz sample rate, in a vertical rectangular grid 36" wide by 18" high and centered on the position of my ears.) For reference, the blue trace shows the spatially averaged response of the Vimberg Mino speakers that I reviewed in the April 2020 issue of Stereophile, when placed in the same positions, well away from room boundaries. Although I usually use 1/6-octave smoothing for my in-room measurements, at Jim Austin's suggestion I used 1/3-octave smoothing in this case, to make the differences in the response trends easier to see.


Fig.7 PMC fact.8 signature, spatially averaged, 1/3-octave response in JA's listening room (red) and of the Vimberg Mino (blue).

With loudspeakers that have nonflat responses, the question is at what frequency to make their outputs equal, in order to compensate for their different sensitivities. I decided to normalize the in-room responses of the PMCs and Vimbergs at 1kHz. The Vimberg Minos have a relatively even in-room response, though with a slight excess of energy between 1 and 8kHz. By contrast, the PMC fact.8s' in-room response is shelved down in the lower midrange and bass and has significantly less presence-region energy. While the Minos' sloped-down response above 6kHz is mainly due to the increased absorptivity of the room's furnishings in this region, the fact.8s have up to 4dB greater output in the top audio octave.

Interpreting the PMC fact.8s' in-room behavior is going to be very dependent on the music being played. If with one recording the listener perceives the level of the upper midrange as being correct, then the lower midrange and low frequencies are going to sound a little lacking in warmth, and the mid-treble is going to sound rather uninvolving. Conversely, if the levels of the lower midrange and presence region are perceived as being correct, the upper midrange is going to sound somewhat forward but also very detailed. Although it wasn't possible for me to perform a set of spatially averaged measurements in KR's room, I think they do explain his auditioning comments.

In the time domain, the fact.8's step response on the tweeter axis (fig.8) indicates that the tweeter and woofers are all connected in positive acoustic polarity. The decay of the tweeter's step doesn't quite blend smoothly with the start of the woofer's step, which suggests that the optimal axis is slightly below the tweeter axis. It is fair to note, however, that the vertical dispersion graph (fig.6) indicates that the frequency response doesn't change between the tweeter axis and an axis 5° lower. The PMC's cumulative spectral-decay plot (fig.9) is impressively clean, though the excess of energy in the up- per midrange is associated with some low-level delayed energy. (Ignore the small ridge just below 17kHz, which is due to interference from the computer monitor's line-scan frequency.)


Fig.8 PMC fact.8 signature, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).


Fig.9 PMC fact.8 signature, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

The PMC fact.8 signature's measurements do correlate with the sonic character Kal reported, I feel.—John Atkinson

The Professional Monitor Company Limited
US distributor: Motet Distribution Inc. (a division of XLO International Inc.)
90 Nolan Court, Unit 30-32
Markham Ontario L3R 4L9, Canada
(905) 474-433

Bogolu Haranath's picture

May be KR could review the new Magico A5 speakers ($22,000/pair) :-) .........

JRT's picture

Any reader of this review looking for a very much better transmission line loudspeaker at fraction of the price should consider the Salk Silk Tower, at the link below:

Bogolu Haranath's picture

They use RAAL ribbon tweeters, which are very good measuring (and, sounding) ribbon tweeters :-) ......

JRT's picture

Yes, the Salk Silk Tower uses RAAL ribbon tweeters and ScanSpeak Illuminator midwoofers, excellent drivers utilized in a well designed loudspeaker. The cabinets are very nicely made, and for moderate upcharge Jim Salk will apply a bespoke veneer of the customer's choosing.

(edit: On reflection, I see that this does read like SPAM, but I have no financial interest in any of this.)

To give some credit where credit is due... My understanding is that R. Dennis Murphy designed and developed the crossover, and Paul Kittinger designed the transmission line enclosure using Martin J. King's Mathcad worksheet(s).

Martin J. King has done a lot to advance the art and science of modeling quarter wave transmission line alignments, and also developed accurate characterization of the behavior of stuffing/damping material utilized at key points within those.

MJK's website:

Some good info on TLs:

Bogolu Haranath's picture

SP(iced H)AM :-) ......

SPAM n' eggs :-) ........

Bogolu Haranath's picture

Bose 'Acoustic Wave' systems use a type of transmission line technology :-) ........

RH's picture

JA: "The PMC fact.8 signature's measurements do correlate with the sonic character Kal reported, I feel."

Fascinating. As soon as I saw this review I wondered if the reviewer would hear what I did, and if it would show up in the measurements.

I spent some time (over a few different days) listening to the PMC fact.8s (IIRC, it was that model), and I heard the same thing reported by Kal. Clear, clean and brilliant high end, but I found the lack of warmth "rather uninvolving."

I continue to value Stereophile's combination of subjective reviews with objective measurements!

Bogolu Haranath's picture

Your favorite Joseph Audio Perspective2 Graphene is close in price ....... It would be interesting, if JA1 provides in-room FR measurements comparing the Joseph speakers with this model PMC speakers :-) .......

RH's picture

I think this can already be seen when comparing the stereophile measurements of the Joseph and PMC speaker. The Joseph speakers also have a very clean, clear sound while maintaining a more even richness in the lower mids/upper bass. Not a "fat" richness, like an old Spendor or a Devore O series speaker (which I also enjoy!), but enough to not feel robbed. That's the type of balance that attracted me to them in the first place.

Bogolu Haranath's picture

Yes ..... These PMC speakers have a 'dip' from 100 Hz to about 500 Hz ...... also, another 'dip' from 1.5 kHz to about 6 kHz in the FR :-) .......

latinaudio's picture

Every time I read JA measurements, I think the same: don't manufacturers have access to equipment like the one used in Stereophile? I think so, they must have it because that is their goal: to create speakers with the fewest defects. Most of the time they are easily correctable things, without major costs. "Those looking for more mid and high bass weight should listen to the fact.8 carefully before buying"... and I need to pay $ 12,000 for this outstanding limitation? If the final product is so low in its performance, the final price should also be low...
Bogolu Haranath: now I understand you!!!

Bogolu Haranath's picture

I agree with you ...... At least, those manufacturers should listen to speakers in their price range, before bringing them to market :-) .........

hb72's picture

some electronics manufacturer offer products that tend to have the characteristics opposite to those mentioned for the PMCs, ie I read some Naim amps, especially when "HiCapped" (add-on PSU for pre-amp stage), tend to have a more pronounced (yet funky!) mid-bass, so that a combination of NAIM & PMC *might* gel quite impressively (helped by suitable speaker cable joice etc), also (or shall we say primarily) w.r.t. famous PRaT.
In other words, its the system neutrality that counts, not so much the neutrality of each and every component, though of course, the latter makes system building a lot easier.

Kal Rubinson's picture

Here's my take. I think that most of them employ intelligent engineers and designers and that they provide them with adequate technical support. However, it is the role of management/owners to decide what product they want to offer including price range, size, materials technology, appearance, finish and sound character. The company then creates those products. Just as with the audiophile market, there are different preferences among the manufacturers. Just IMHO.

Bogolu Haranath's picture

May be the management/owners like only sopranos but not baritones ...... Just kidding :-) ......

Bogolu Haranath's picture

If Louis Armstrong sings 'Show Me How You Burlesque', he would sound just like Christina Aguilera :-) ......

Bogolu Haranath's picture

On a side note ....... May be KR could review the new Legacy 2, 5, 7 channel ICEedge Class-D amp, 610 WPC X 7, into 8 Ohms, $7,950 :-) .......

Ortofan's picture

... ultimate transmission line type speaker:

Bogolu Haranath's picture

Take a look at the PMC fact fenestria TL speakers ($65,000/pair) :-) .........

Ortofan's picture

... the mid-range driver.

Bogolu Haranath's picture

I know ..... The midrange driver is isolated just like the tweeter, which is ideal in a 3-way speakers ...... Mid range is not interfered by the bass frequencies ....... TL usual principle is to extend and increase the amplitude of bass frequencies, not the midrange or treble :-) .........

Bogolu Haranath's picture

You can read about 'Transmission line loudspeakers' in Wikipedia :-) .......

Bogolu Haranath's picture

KR also, wrote about the principles of TL in his review of PMC IB-1S speakers :-) .......

DavidParis's picture

Well, that's a pity. I've been planning to audition and hopefully acquire the new PMC Twenty5 23i for use with Naim electronics. It's clear that the fact 8s are different animals but many of the design principles are similar with PMC's other models. Clearly, neutrality and linear response seem to correspond to a "house" philosophy and may not please everyone. For the 12K USD expenditure, I would've expected a more impressive and certainly better balanced result.

Bogolu Haranath's picture

For the price of PMC Twenty5 23i, you could consider Monitor Audio Silver 300, reviewed by KR for Stereophile :-) ........

Bogolu Haranath's picture

Couple of other choices for the price of 23i are, NHT C4 and Revel performa F206 :-) .......

Peter-PhonoPhono's picture

After reading the listening report as well as the comments, I could not resist commenting on the PMC Fact. I am dealer in Berlin, Germany and carry PMC for years. The Fact.8 is - in my opinion - a fascinating speaker. As all PMC speakers, the FACT.8 is very natural and - with the wrong amplifier - can sound a bit (too) dry. I cannot judge the Benchmark or Bryston amp, as I don't carry those brands.
I present the Fact.8 with an excellent, well matching amplifier like a Sugden IA-4: this combination sounds breathtaking in any aspect. I can only encourage anyone looking for an elegant, excellent sounding speaker in this price range, to try the PMC FACT.8.

Kal Rubinson's picture

From Jim Austin's review of the Sugden preamp: "As I heard it, the Sugden Masterclass LA-4 was not quite a straight wire with gain: it subtly illuminated the music."

Perhaps that's what the PMC needs.

Bogolu Haranath's picture

Tubes are known to have that 'inner glow' :-) .......

Bogolu Haranath's picture

Measuring the PrimaLuna EVO 400 pre-amp, JA1 said, 'it has second-harmonic distortion signature, which will fatten-up the sound' ........ So, EVO 400 could also, 'illuminate the music ' :-) .......

Peter-PhonoPhono's picture

I agree, a Sugden might not be the most neutral amplifier on earth - but also far away from coloring. A Sugden will make many (most?) speakers sing, which is what most listeners love.
We also use a lot of valve amps as partners for PMC , i.e. EAR Yoshino, Air Tight, Mastersound. Many 'british' amplifiers (Rega, Croft and others) also go well with PMC. All those amps might play a tiny little bit on the sweater side.
I don't think, the Fact.8 is a critical speaker. However, it will immediatedly show wrong system matching (as it should do with this price tag!).

JRT's picture

What this overly flawed loudspeaker really needs is a complete redesign, not just a pairing with a boutique amplifier that cascades another set of sound defects onto the highly flawed electroacoustic transfer function.

Bogolu Haranath's picture

If we add active or passive subwoofer(s), that could help for this model PMC speakers ....... The crossover could be set around 160 Hz with the subwoofer(s) ........That could help in the bass, upper bass and lower midrange regions ........ Of course, that would add to the total cost of the system ..... PMC makes some TL subwoofers, BTW :-) .......

JRT's picture

There are better loudspeakers available at much lower price point, and there are very much better loudspeakers available at similar price point.

I would argue that it would be better to choose something else, regardless any consideration of subwoofers.

And perhaps the money saved by choosing something better at a lower price point might free up some budget to pay for a good low frequency subsystem. For example, you can get an SVS SB16 Ultra powered subwoofer for $2.0k or two for $3.8k. Those are relatively well designed with good performance from a retail product at the price point.

Bogolu Haranath's picture

Yes ...... Q Concept 500 which I mentioned, see below ....... Another choice is Revel Performa F228Be, $10K, which KR reviewed ...... There may not be a need for subwoofers for the Revels :-) .......

JRT's picture

Modal response of the room around and below Schroeder frequency, more specifically the interference from associated Eigentones, can sometimes be exacerbated by full range loudspeakers with positioning optimized for good performance above the Schroeder frequency.

In more plain English, the locations and positioning good for the spectrum of sound radiation from tweeters and small midwoofers might not be good at the much longer wavelengths of subwoofer frequencies which excite standing waves in the room (room modes) at low frequencies, sub-Schroeder spectrum where that causes very audible interference problems.

That modal response might be improved, the problems ameliorated with use of a well designed separate low frequency subsystem using multiple subwoofers suitably positioned, using suitable processing, maybe using some PSI AVAA C20 active interference sources in room corners, etc.

Bogolu Haranath's picture

Yes ...... We can do it either way ....... Full-range speakers with digital room-correction technology such as Dirac Live, Anthem Room Correction (ARC), Audyssey multi EQ etc can also be utilized :-) .......

Ortofan's picture

... now buy a pair of the Revel Studio2.

Quoting KR:
"What's not to like—indeed, love—about the Revel Ultima Studio2? Almost nothing. I could point to the flimsy trap door and the less-than-overwhelming soundstage spread, though the latter was probably particular to my room. In the areas of lack of coloration, integration across the audioband, dynamic range, imaging, and soundstage depth, the Studio2s were simply outstanding. Including electrostatics that can't approach the SPLs that the Revels handled with aplomb, the Ultima Studio2s imposed less of a fingerprint on the sound than any speaker I have used. Urgently recommended, both to those in the market and to those who simply want to hear how good a loudspeaker can be."

Quoting JA1:
"The Revel Ultima Studio2 offers superb engineering and measured performance for which no apology need be made. It is a worthy successor to the original Ultima Studio, which has been one of my speaker references for the past seven years."

Kal Rubinson's picture

Ortofan wrote: The $12K price of these PMC speakers will now buy a pair of the Revel Studio2.

Yes and, in fact, I bought a pair and a half!

Ortofan's picture

... Victor Kiam level of endorsement, but close enough.

Bogolu Haranath's picture

Not so fast ....... Who knows, KR could buy the Revel speaker company after he retires :-) .......

Kal Rubinson's picture

I retired in May of 2015.

Bogolu Haranath's picture

I meant retiring from reviewing for Stereophile ....... However, we don't want you to retire from reviewing for Stereophile for many many more years :-) ........

Bogolu Haranath's picture

Mr. Kevin Voecks thanks you for your support :-) ........

Kal Rubinson's picture

Yes, he has and I have thanked him for his. :-)

Bogolu Haranath's picture

Another choice for $15k price tag, Yamaha NS-5000 :-) ........

Bogolu Haranath's picture

Adding couple of powered subwoofers from other manufacturers could bring the total price tag to around $15k ....... Then the total set up could produce decent full-range sound :-) ......

Bogolu Haranath's picture

Q Acoustics Concept 500 reviewed by Stereophile, may be a better value for the money at half the price :-) ........

Kal Rubinson's picture

Peter-PhonoPhono wrote: I agree, a Sugden might not be the most neutral amplifier on earth - but also far away from coloring.

Either/or. It is one or the other to some degree.

Bogolu Haranath's picture

Another Sugden model A21-ai integrated amp was reviewed and measured by Stereophile ........

May be two negatives make a positive :-) ........

DA KOOL 1's picture

Hi y'all

I just wondered if any of you will be familair with this vintage speaker and could give me someadvice on their performance.

I'm thinking of buying a pair

Roger That's picture

This review basically describes a pair of loudspeakers that perform below what it should, even if their price was 10% what really is.

One can argue that maybe it will sound good on a particular room (maybe the one that the engineer’s used to “tune it”?), but it seems way too flawed to work properly on most rooms.

There are loads of loudspeakers that behave and sound a lot better from a fraction of the price (some were mentioned on the review), and I believe that the Stereophile method of reviewing (subjective performance first, measuring after) usually shows a correlation, or at the very least, helps in understanding what might be the behavior of a specific reviewers room and the loudspeaker itself.

I don’t trust most subjective reviews in isolation because even if the reviewer has very similar sonic tastes as I do, we might get totally different sound performance from the same speakers because the room got too much in the way.
I learned it with my own money (by basically wasting it in the process of bad decisions).

I can now measure my rooms (which leads me to understand their problems) and I strongly feel that John Atkinson measurements are a huge and amazing library of data on loudspeaker performance.

It doesn’t suppress the need of human reviewers (at all), but it goes hand in hand on helping to understand the science behind it and maybe have a greater chance of making informed buying decisions.

I believe that both reviewers were as polite as possible in the way this $12.000 loudspeakers behaved, and all but the seriously distracted reader understood what was presented.

This is also great for the manufacturer if it acknowledges that we’re not longer in a age where real information is scarce, and brings this product (and future ones) back to the drawing board.

I would like to congratulate both Stereophile and Mr. John Atkinson for the amazing contribution on loudspeaker reviewing and testing for all these decades.

Thank You.

John Atkinson's picture
Roger That wrote:
I would like to congratulate both Stereophile and Mr. John Atkinson for the amazing contribution on loudspeaker reviewing and testing for all these decades.

Thank you Roger. I believe that the suite of measurements I have developed over the last 30 years for Stereophile provide good correlation between a loudspeaker's measured performance and its sonic character. These measurements do a good job at revealing coloration, overall balance, low-frequency behavior, and stereo imaging accuracy. However, they won't tell whether a loudspeaker is great or merely good. For that the listening experience is paramount.

John Atkinson
Technical Editor, Stereophile

Bogolu Haranath's picture

JA1's loudspeaker measurements are the gold standard, best in the world ....... Even better than Hi-Fi News measurements, if I'm allowed to say so ...... Thank you JA1 :-) .......

Kal Rubinson's picture

Roger That wrote: I believe that both reviewers were as polite as possible in the way this $12.000 loudspeakers behaved, and all but the seriously distracted reader understood what was presented.

I would like to congratulate both Stereophile and Mr. John Atkinson for the amazing contribution on loudspeaker reviewing and testing for all these decades.

I have no doubt that Stereophile readers understand what was presented as evidenced by their scrupulous analysis (in letters and posts) of what we publish. We have no need to be nasty or snide although the temptation is undeniable.

JA's efforts over the years have been critical. For readers, he has provided not only clear and useful information but, also, an accessible database that allows one to compare products objectively and to see how manufacturers have advanced their their technology over time.

For reviewers (or, at least, this one), the knowledge that JA will be testing and measuring the products that are passed on to him imposes a need to consider "What am I hearing?" in addition to "How does it sound?" That, alone, enforces a deeper appreciation of the product's performance.

Bogolu Haranath's picture

If you look at the FR measurements of DeVore GibbonX, you can find a lot of similarities, especially from 100 Hz and above :-) .......

MikeP's picture

I bet these new NSMT Model 100's are better than any of these speakers !