Sjöfn HiFi (the clue) loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Sjöfn Clue's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. My estimate of the Clue's B-weighted voltage sensitivity confirmed the specification of 87dB/2.83V/m. The minimum impedance is specified as 4.2 ohms; the solid trace in fig.1 shows that our samples went a little lower than that, reaching 3.7 ohms at 270Hz and 2.67 ohms at 4.7kHz. However, as the electrical phase angle is never high when the impedance is low, a good, 4 ohm–rated amplifier should have no problem driving the Clue.

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

There is a small discontinuity in the impedance traces just below 400Hz; when I investigated the cabinet's vibrational behavior with a plastic-tape accelerometer, I found a very strong resonant mode at 387Hz on all surfaces (fig.2). This resonance is high enough in amplitude and low enough in frequency that I would be surprised if it didn't give rise to audible coloration. However, it's fair to note that Herb Reichert didn't comment on any midrange congestion that might have resulted from this behavior.

Fig.2 Sjöfn Clue, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle at 36Hz in the impedance-magnitude trace suggests that the port is tuned to this frequency; the port's output, measured in the nearfield (fig.3, red trace), does indeed peak between 30 and 40Hz. However, the corresponding minimum-motion notch in the woofer's nearfield response (blue trace) occurs a little lower in frequency, at 33Hz. This is a low tuning frequency for a relatively small speaker, and the Clue's overall low-frequency response (black trace) actually starts to shelve down two octaves above the port's peak output. It must be remembered that the Clue is intended to be used when placed flush with the wall behind it. However, as the nearfield measurement technique assumes just such a condition, this graph therefore correlates with HR's finding the speaker's low frequencies to sound lean. And note the high-Q resonance in the port's output at 800Hz.

Fig.3 Sjöfn Clue, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with nearfield responses of woofer (blue) and port (red) and their complex sum (black), respectively plotted below 300Hz, 1kHz, 300Hz.

The right portion of fig.3 shows the Clue's farfield response, averaged across a 30° horizontal window on the tweeter axis. It is not all flat, but discussing the implications is not easy, as it depends on which frequency region(s) the listener's ear/brain takes as a reference. If the peaks in the high midrange and mid-treble are heard as correct, the lows will be shelved down, the presence region will sound way too polite, and the top octave will be lifeless. But if the midrange and presence regions are heard as being correct, then the aforementioned peaks will be heard as colorations.

In rooms of small to medium size, the balance will also strongly depend on the speaker's radiation patterns in the horizontal and vertical planes. Fig.4 shows the Sjöfn's horizontal radiation pattern, normalized to the response on the tweeter axis. The contour lines in this graph are smooth and evenly spaced in the midrange and low treble; however, the woofer becomes quite directional at the top of its passband, which results in a significant lack of off-axis energy in the region where the on-axis peak in the mid-treble begins to develop. In the top octave, where the trace in fig.3 has a severe suckout, there is actually a lot more energy off axis, which in a small room like HR's will probably give enough output in the top two octaves. Note that HR did write that the Clue's "high frequencies were extended and well dispersed." In the vertical plane (fig.5), the Sjöfn's radiation pattern suffers from severe suckouts at 5kHz above and below the tweeter axis, which will also work against the audibility of that mid-treble peak in the tweeter-axis response.

Fig.4 Sjöfn Clue, 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.5 Sjöfn Clue, 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.

The Clue's step response on the tweeter axis (fig.6) indicates that both drive-units are connected in inverted acoustic polarity. The small height of the tweeter's step implies a high crossover frequency, most likely the same 5kHz as the off-axis suckouts in the plot of vertical dispersion. There is a strange double arrival in the woofer's step. Finally, the cumulative spectral-decay plot on the tweeter axis (fig.7) reveals a clean decay throughout the treble, but with some delayed energy associated with the on-axis peaks centered on 1 and 6kHz.

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

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

Overall, to judge from HR's comments on the Clue's sound, the speaker's balance is dominated by that shelved-down bass region. And while the Sjöfn's on-axis problems will be to some extent balanced by the off-axis behavior, especially in smaller rooms, I'm not surprised that when HR set up his Rogers LS3/5As, he found that even with that vintage speaker's own departure from a flat response, their octave-to-octave tonal balance was "significantly more realistic," and their soundstage was "more open and naturally proportioned."—John Atkinson

Mikeymort's picture

You mention the Dynaco ST120/A-25 combo which is my reference as well. (I still use my A-25's but sold my ST125 years ago.) I have kept the A-25's in service as they have the quality of never being fatiguing. I listen to audio almost constantly, music, news and sports. (I love a baseball game on the radio, or these days, being streamed over the internet) Since you have liked the A-25's, I'm guessing you heard this quality as well.

You never really followed up on on how the Sjöfn was different from the Dynacos, I'm sure it's better on the top-end, I'd be interested in your observations.

Allen Fant's picture

Nicely done! HR-
IME, Creek builds a very nice integrated that does well w/ many loudspeakers, inculding my reference, Thiel CS 2.4 - while the little Creek cannot satisfy the high power/current hungry Thiel spearks, it holds its own regarding "timbre".

dalethorn's picture

I'm not surprised by any of this. They need to optimize at both ends - best cases and worst cases, and it looks like they did only one.

Ishmael's picture

I very much enjoyed the article, well done Herb. I myself own the Clues and am very impressed with them but it was not an easy road to get here. I, like you, tried the suggested configuration for setup. I also rolled through tons of amps and sources. I ended up with good but not great result.

After about 6 months of trying (I was about ready to bail on the whole thing) I ended up trying more placement options in a last ditch effort to make the things work. I went extreme on the wall placement - nearly touching on the one corner, slightly more distance on the other due to toe-in. I also spread them out more than usual which put the left speaker up against a side wall - an unthinkable placement with most any other speaker. Bingo. This did the trick, and I'm getting substantially better sound than any other speaker I've tried in this room (including the LS50 and a bunch more in the $2k-3k range).

In summary, I bought these hoping for easy placement and good sound in my difficult room. I ended up with GREAT sound but it took more work to get there than with any other speakers I've owned, in any other room I've tried.

brian2010's picture

I wonder if this is the same Jim Croft who built transmission line four channel speakers for me in Vancouver, WA in the 1970s? He and a gentleman named Huber were just starting out in the industry and the speakers, hooked up to a Pioneer QX-8000 receiver, Thorens, Nakamichi and Teac sources were awesome. The system is still the best I have ever owned four decades later.

brian2010's picture

It is the same Jim Croft and I can tell you from experience any speaker he is involved with is going to be exceptional. I will soon go to Seattle to personally check these speakers out and you should, too. I doubt he has regressed in 40 years in the business.

Hi-Reality's picture

Dear Herb,

I use a pair of (the clue) loudspeakers from Erickson/Croft at Sjöfn HiFi driven by a pair of Khartago Mono Extremes from Klaus Bunge at Odyssey Audio as a reference system. They generate a dynamic and transparent experience with an amazing LF response ('Coffee', rather than 'Wine', is perhaps a good word to describe them. I think they will perform even better after I am done with the necessary improvements planned. One of my to-do items is to ask Lars Erickson for some Supra speaker cables and interconnects.

So my question #1: did you sense improvement/added realism after you installed them? this info was unfortunately missing from your report.

My question #2: What were the room size and shape you tested (the clue)'s in? what I can reveal at this point of my project is that these speakers' highest performance level is achieved in smaller and symmetrical rooms (I can't say what shape or how small though :-). So, in that sense they are performing as near-field monitors rather than the usual stand-mounters. And damn good ones!

My question #3: you have listed headphones and headphone amplifier in your equipment list; but there is no mention of them in the review. what was their function?

Thanks for this review. I was very happy to finally see a Stereophile review of Sjöfn HiFi (I had previously asking Stereophile to be kind and review them, see url below for one)

I am looking forward to your feedback.

Regards, Babak
Founder, The Hi-Reality Project,

corrective_unconscious's picture

I see your base instincts have come to the fore.

danger's picture

HR starts out in his high chair and ends in his slippers with his little dog. Seriously!? I think the review says more about HR than the speakers. Writing is unfocused just like HR's review process. He is all over the place.

argyle_mikey's picture

The company website diverts you to their eBay page. That offers plenty of nice looking cables etc but no sign of this most interesting sounding speaker. I do hope that they didn't stop making it.


TennesseeTuxedo's picture

As an owner of the clues for many years now I am politely mystified by this review. As a Denver resident and long standing audio nut and therefore a regular attendee at RMAF (Rocky Mountain Audio Fest), I stumbled upon the Sjofn Hi-Fi room many years ago back when they had a product called the Guru, which was an excellent speaker though, alas, out of my price range at the time. I lamented that to Lars Erikson, the man in the chair in socks and sandals at the Sjofn room and he said "Don't give up on us. We're working on that!" And a few years later I was pleased to find the clues in the Sjofn room, and in my price range no less. In addition to being affordable I made numerous trips to many rooms and to come back and compare the clues sound against: NHT, Sonus Faber, Zu Audio, Vandersteen, everything by Andrew Jones, Siggy Linkwitz, Hsu Research, Emotiva, Macintosh (!), Magnepan, Audio Research, German Physiks, YG and I don't remember the others. What impressed me was that the clues sounded as good as the best of those, and much better than the worst of them. So I purchased a pair of the clues and have been QUITE happy with them ever since. I knew they would sound best in a smaller damped room like the hotel room I heard them in. So I paired them with a simple Yamaha Natural Air integrated amp/receiver and a Carver FM tuner and just plunked them on tv tables in the corner of my smallish bedroom. I can tell you Colorado Public Radio and KUVO the jazz Station sounded PHENEMONAL, balanced, rich, and 3-dimensional. And whatever computer audio I was running also sounded excellent (without a DAC). Now I have a tall condo with a tv hutch and wouldn't you know it - the clues are a perfect fit for tv hutch design, now paired with a Denon AV Receiver/Integrated amp (and boat wire tin coated copper as speaker cables - hee hee hee!). But they need lots of clean power and symmetrical geometry in the room. You give them that and they will reward you for years to come, as mine have.

I also have a robust Rotel component system powering Revel M22's, Vandersteen Model 2's and Thiel CS 1.2's all connected via the requisite absurdly expensive cables. All three of those speaker sets sound best in a BIG TALL room. Whereas the Clues rule the SMALL COZY room. So basically if your ceiling is over 12 feet the clues are not going to impress you. If the ceiling is under 12 feet and you put them very close to the wall on stands 22 inches high with a smidge of toe in, then you will be delighted. Music. Home Theater. Whatever.





argyle_mikey's picture

Well, Lars responded to my email pretty quickly. The Clues are still available for 999 of your US dollars and he will post to the UK, so I'm going to jump in too. Amp will be a NAD M2, which seems to fit the bill power-wise at least. Should be interesting...


LostnAmerica's picture

Greetings from across the pond, I am eager to hear if you have received your speakers how your setup is working with your "the clue" speakers and, if any insight you might share in seting up. I thank you in advance...



LostnAmerica's picture

The latest comment from November of 2016 gave a little hope, they are still available, thats good news for the average consumer. I am taking a "chance" on a used pair of the clue that I found. And are patiently waiting for their arrival this week. I read as many reviews on this speaker as possible and about 90% were positive and encouraging that is why I searched and searched for a used pair. With the exception of the review on Stereophile which had led to (less than favorable) a recommendation which is a little confusing. I understand that the issues of concise placement and possibly the correct power supply (?) and I hope to conquer them, being a novice, this will be fun. I am excited about these little gems and will hope to draw out their full capabilities . Time will tell. Meantime, I hope others will report of their successes and issues with these speakers and look forward to reading and learning. I can understand how the performance of such a diminutive speaker and company could conceivably cause issues with the mainstream and "hi-End" speaker system companies, but really...I would add that I am a subscriber to this magazine and love it. And I would hope another updated "review" by possibly another of these speakers with no malicious intent to the original reviewer/author (however unprofitable as this might be) for the average consumer who might be able to afford the $1000 speaker and might see and eventually hear. Thanks for listening to my tirade...

argyle_mikey's picture

The curse of the audiophile - household repair demands for your hard earned cash - delayed my purchase. Sorry. In the meantime, I also think it's time for a reappraisal. I can't think of another component that received such a mixed review but remains in the Stereophile Recommended list. This speaker appears to be a bit of an enigma.


argyle_mikey's picture

Just bumping this (do people still bump things?) because I’m genuinely curious.

I don’t understand why some long-standing products get re-reviewed every few years - Totem Mani 2 seems to get a full review more often than I change my underpants - yet others are ignored. If ever a product required a follow up, I’d say it was this one.

How about it JA ?