Perlisten S7t loudspeaker Measurements

Sidebar 3: Measurements

The center of the Perlisten S7t's DPC high-frequency driver array is just 32" from the floor. While the distributor had placed the loudspeaker on a 3"-high dolly when he delivered it, I wasn't able to lift the speaker any higher for the measurements. (It weighs 122.5lb.) I therefore performed my farfield frequency response measurements at 1m rather than my usual 50" in order to push the reflections from the floor as far back in time as possible.

(I allowed for the slight tiltback of the loudspeaker's front baffle, to ensure that the microphone was on the central tweeter axis, and I didn't use the vestigial grille.) I used DRA Labs' MLSSA system, an Earthworks microphone preamplifier, and a calibrated DPA 4006 microphone to measure the Perlisten S7t's farfield behavior, and an Earthworks QTC-40 mike for the nearfield responses.

Perlisten specifies the S7t's sensitivity as a high 92.2dB/2.83V/m, which was confirmed by my B-weighted measurement. The S7t's impedance is specified as 4 ohms nominal, with a minimum magnitude of 3.2 ohms. Using Dayton Audio's DATS V2 system, I found that the impedance magnitude (fig.1, solid trace) remained above 4 ohms for much of the audioband with minimum values of 3.125 ohms at 147Hz and 2.47 ohms between 14.5kHz and 16.3kHz. The electrical phase angle (dashed trace) is occasionally high when the magnitude is low. For example, there is a combination of 4.7 ohms and –45° at 88Hz, a frequency where music can have a high level of energy. The EPDR1 drops to 2.2 ohms between 32Hz and 39Hz, 1.5 ohms between 93Hz and 111Hz, and 1 ohm at 20kHz. The EPDR also lies below 3 ohms for the entire midrange. The S7t should be used with amplifiers that don't have problems driving 2 ohm loads, though the drive difficulty will be alleviated by the speaker's high sensitivity.


Fig.1 Perlisten S7t, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The traces in fig.1 are free from the small discontinuities in the midrange that would imply resonances of some kind. When I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I found a couple of resonant modes in the midrange (fig.2). However, these are low in level and have a relatively high Q (Quality Factor), both of which imply that they will not affect sound quality.


Fig.2 Perlisten S7t, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall level with the second woofer from the top (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle centered on 27Hz in the impedance magnitude trace suggests that this is the tuning frequency of the reflex-loaded woofers. The red trace in fig.3 shows the nearfield response measured at one of the vents at the speaker's base. There is a broad peak centered on 27Hz but also significant output in the midbass region before the response rolls off steeply above 80Hz. The blue trace below 350Hz is the summed nearfield response of the four woofers. Although the information sheet on Perlisten's website says that the woofers can be operated with the reflex ports open or closed, all four woofers behaved identically, with a minimum-motion notch at the port tuning frequency, which indicates that the ports were open. The boost in the upper bass is an artifact of the nearfield measurement technique, which assumes that the radiators are mounted in a true infinite baffle, ie, one that extends to infinity in both planes. When corrected for this, the woofer's upper- and mid-bass output will be flat.


Fig.3 Perlisten S7t, acoustic crossover on tweeter axis at 1m, corrected for microphone response, with the nearfield response of the ports (red) and the summed nearfield responses of the woofers (blue), respectively plotted below 220Hz and 350Hz.

The blue trace above 350Hz in fig.3 shows the farfield response of the woofers. The woofers at the top and bottom of the front baffle start rolling off above 600Hz, but the two woofers closest to the DPC array cross over to the farfield output of the array (green trace) at 1.4kHz, with then a steep, 18dB/octave rolloff. The DPC array rolls in steeply with what appears to be a 24dB/octave slope. Its output is flat in the low and mid-treble, though a slight peak is apparent at 10kHz. The tweeter's fundamental dome response can be seen at 23.7kHz, safely above the audioband. Fig.4 shows the S7t's farfield response averaged across a 30° horizontal window centered on the tweeter axis. The nearfield bump in the upper bass is present, but overall the response is impressively even in the midrange through to 7kHz or so. There weren't any significant differences when I repeated this measurement with the grille covering the DPC array (not shown).


Fig.4 Perlisten S7t, anechoic response on tweeter axis at 1m, averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield responses plotted below 300Hz.

The S7t's horizontal dispersion is shown in fig.5. (The traces are normalized to the response on the tweeter axis, which thus appears as a straight line.) Other than a slight off-axis flare in the presence region, the loudspeaker's radiation pattern is smooth and even up to 6kHz. Above that frequency, the DPC array's radiation pattern starts to narrow, which might make the speaker sound a little airless in very large rooms. The Perlisten's vertical dispersion, again normalized to the response on the tweeter axis, is shown in fig.6. The loudspeaker's balance doesn't change appreciably over a wide ±10° window, though a suckout at the crossover frequency starts to develop 15° above the tweeter axis. Don't listen to this speaker while standing.


Fig.5 Perlisten S7t, lateral response family at 1m, 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 Perlisten S7t, vertical response family at 1m, normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–10° below axis.

In the time domain, the S7t's step response on the tweeter axis (fig.7) reveals that all the drive-units are connected in positive acoustic polarity. The decay of the DPC array's step smoothly blends with the positive-going start of the woofers' step, which implies optimal implementation of the crossover filters. The S7t's cumulative spectral-decay plot (fig.8) is superbly clean, especially in the region covered by the DPC array.


Fig.7 Perlisten S7t, step response on tweeter axis at 1m (5ms time window, 30kHz bandwidth).


Fig.8 Perlisten S7t, cumulative spectral-decay plot on tweeter axis at 1m (0.15ms risetime).

To say that I was impressed by the Perlisten S7t's measured performance would be an understatement. It typifies excellent loudspeaker engineering.—John Atkinson

Footnote 1: EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier's output devices as the loudspeaker. See "Audio Power Amplifiers for Loudspeaker Loads," JAES, Vol.42 No.9, September 1994, and
Perlisten Audio
807 Liberty Dr.
Verona, WI 53593
(414) 895-6009

rt66indierock's picture

I'll take the robaot over any reviewer as long as Paul Seydor's wife Danielle says it desn't sound like hi-fi. Now I'm down to the age old question, will it play my reference albums and recordings?

Kal Rubinson's picture

What is a robaot?

rt66indierock's picture

The Kippel is an important tool to measure speakers. Kind of a shame Amir is the only reviewer using it.

John Atkinson's picture
rt66indierock wrote:
The [Klippel] is an important tool to measure speakers. Kind of a shame Amir is the only reviewer using it.

While I have personally spent >$50k on test equipment over the years, the $100k the Klippel NearField Scannner costs is out of reach for me financially. :-(

There is also the fact that the Klippel needs to be used in a space with a 10' ceiling height, which is not feasible in my NYC home.

Nevertheless, I don't feel my loudspeaker measurements are lacking.

John Atkinson
Technical Editor, Stereophile

rt66indierock's picture

for a discussion of measuring techniques for loudspeakers. I'm going to use measurements from a Klippel when I can. I don’t use yours because I want to measure speakers myself. And of course, play my reference albums and recordings in an environment I control.

I recently acquired a new SUV and have heard six tracks from my reference albums in the last month. It will be an adventure to adjust the audio system to play them reasonably well.

remlab's picture

also uses Klippel, but for what it's worth, JA's measurements do get the job done, except for maybe loudspeaker THD measurements.

John Atkinson's picture
remlab wrote:
. . . for what it's worth, JA's measurements do get the job done, except for maybe loudspeaker THD measurements.

Thank you.

John Atkinson
Technical Editor, Stereophile

remlab's picture

vs Klippel is A little like Garry Kasparov vs Deep Blue. Deep experience vs pure processing power. Each obviously has their strengths and weaknesses.

SamTroft's picture

Dont know who Amir is but Erin's Audio Corner has been using Klippel for his reviews.

dc_bruce's picture

While it certainly seems possible that system of this size could be set up for bass extension to 20 Hz (-3dB), the designers apparently have made a choice to forego that in favor of a bit more efficiency. Given that most home listening environments have a 3 to 6 dB boost in the 40-50 Hz range, it's likely that, in-room, this speaker is "flat" to below 40 Hz. The result, according to Kal's report is plenty of bass power (undistorted, uncompressed loudness) achieving a sense of realism that most people want. As Mr. Austin's footnote advises, those wanting 20 Hz extension can always add a subwoofer or two (of equal dynamic capabilities to the main speakers) in order to hear the "hall sound" and other ULF. Given that most subs feature self-adjusting room correction, this probably would result in better sound than a totally passive, uncorrected single "full-range" system of equal LF extension.

Jack L's picture

.........uncorrected single "full-range" system of equal LF extension." quoted dc bruce.


IMO, SURELY not "probably".

My experience tells me active sub(s) when blended properly with any "full-range' loudspeaker system will surely improve its ULF than without.

I finally get back the music I missed soooo much before without my active subs installed!

Listening is believing

Jack L

BluesDog's picture

No small feat competing well against your Revels. Also would you say it plays better ported or sealed?

Kal Rubinson's picture

Dunno. Only used them as ported, at the recommendation of the distributor/installer. Also, despite their supposed good accommodation for subs in the sealed configuration, a domestic speaker of this size would most likely be employed in stereo in most systems and would be expected to perform well without subs.

BluesDog's picture

Thanks, Kal. How far from the front wall would you say is prudent?

Kal Rubinson's picture

??? Prudent in what way?

BluesDog's picture

As far as I’m concerned John and Kal are among the best there is at what they do. They are in Elysium, which we can almost grasp but which enlightens us and helps us to be better. John will always be the standard by which all testers and their equipment are measured. I’ll take John’s meticulous approach, scientific consistency and sheer will over anybody else and the latest “Flux Capacitor” out there. John gets my lifetime vote as the Michelangelo of testing components and speakers. Kal consistently produces gem reviews with insight and music choices that unearth a speaker’s capabilities. We, as readers, get a frequent real treat from John, Kal and the rest of the Stereophile Audiophile Squad!

John Atkinson's picture
BluesDog wrote:
I’ll take John’s meticulous approach, scientific consistency and sheer will over anybody else . . .

Thank you. I appreciate your comments. About consistency: I have always felt that consistency of approach to testing and the presentation of the results is important. The loudspeaker tests in Stereophile feature a common format that allows a speaker's measured results from 30 years ago to be easily compared with those of current-day models.

John Atkinson
Technical Editor, Stereophile

Dan Nagar's picture

Thank you for an amazing review about amazing speaker.

this one as all the bass needed .

the issue with sub woofer integration should be considered in every system and its not related (always) to fronts speakers extension or specific in room response( again - in terms of room gain)

sub or multiple subs - configured correctly will give a much smoother response .

thank you again

Jack L's picture


Hopefully the speakere driver units are NOT made in China as well !!!

Jack L

jmsent's picture

..are all made in China. They appear to be excellent performers.

Lee Robert's picture

No disrespect but I will wait for a more credible review before I seek these out for a demo.

Kal Rubinson's picture

If you doubt our credibility, you can easily find several other reviews out there but, of course, I cannot vouch for their credibility.

Ortofan's picture

... a better way for 'Lee Robert' to have phrased that comment, rather than "wait for a more credible review."

Following is a link to another review (that includes a set of measurements) and their results essentially confirm the findings of KR, along with those of JA1.

rschryer's picture

From whom?

Kal Rubinson's picture

My remark was not to impugn other reviewers nor did I intend to provide links to other reviews but as directive in response to the implication that our review was less credible than other, yet undefined, reviews. They do exist and Mr. Robert should use Google to seek them out.

BluesDog's picture

I can’t believe how many people engage in what the Brits would term “rather shirty” remarks just for attention. People the caliber of Kal and John have WAY better things to do then defend themselves from what radio announcers were forced to call “bullsch.” I read another article about the Perlisten S7t with testing. While a good and decent article, Stereophile is always the gold standard. It’s like comparing Double AA or Triple AAA baseball players to the Gods of Baseball, Sheesh! Long after the universe has shrunk to it’s last dying star, people will be saying about Stereophile reviewers, especially Kal and John, To add lib Aztec 2Step: There will never be a faster gun or another one like you are!

So to snarky readers here is what bikers would have to offer: Sit down, shut up, and hold on!

BluesDog's picture