Morel Octave 6 Limited Edition Bookshelf loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Morel Octave 6 Bookshelf's frequency response in the farfield; for the nearfield frequency response, I used an Earthworks QTC-40, which has a ¼" capsule and thus doesn't present a significant obstacle to the sound.

My estimate of the Octave 6's voltage sensitivity was 85.1dB/2.83V/m. Though this is what I would have expected from a small two-way speaker having a 6" mid/woofer, it's significantly lower than the specified 88dB/2.83V/m. The speaker's nominal impedance is 4 ohms; its impedance magnitude (fig.1, solid trace) indicates that the Octave 6 actually remains above 8 ohms for almost the entire upper midrange and treble, dropping below 6 ohms only in the lower midrange. Although the minimum impedance is 4.2 ohms at 165Hz, the combination of 6 ohms magnitude and –44° electrical phase angle at 103Hz suggests that tube amplifiers will work best when used from their 4 ohm output-transformer taps.

Fig.1 Morel Octave 6 Bookshelf, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The sharply defined discontinuity between 380 and 400Hz in the impedance traces indicates the presence of some kind of resonance in that region. Investigating the enclosure panels' vibrational behavior with a plastic-tape accelerometer, I did find a series of resonances, the lowest in frequency lying at 395Hz (fig.2). This graph was taken on the top panel; the side panel (not shown) behaved similarly. However, when I examined the behavior of the rear-panel port, I found two high-amplitude resonant peaks in its output, at 400 and 800Hz (fig.3, red trace). The effect of this behavior on music will be unpredictable, because the port faces away from the listener and because, as these resonances are of very high Q (Quality Factor), music will have to have sustained content at precisely these frequencies for the resonances to become fully excited. Nevertheless, these peaks could be easily heard on the noise-like MLS signal as a hollow-sounding coloration.

Fig.2 Morel Octave 6 Bookshelf, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of top panel (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

Fig.3 Morel Octave 6 Bookshelf, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with nearfield responses of woofer (blue), port (red), and their complex sum (black), respectively plotted below 300Hz, 620Hz, and 300Hz.

The saddle centered on 53Hz in the impedance-magnitude trace suggests that this is the port's tuning frequency; the woofer's output does indeed have a sharp notch at that frequency (fig.3, blue trace), at which the back pressure from the port's tuning resonance holds the cone stationary. Other than the midrange peaks discussed above, the port's output covers a well-defined bandpass from 40 to 100Hz. The complex sum of the woofer and port outputs (fig.3, black trace below 300Hz) peaks at 80Hz. Some of this peak will be an artifact of the nearfield measurement technique, but the shape of the trace does suggest that the Octave 6's low-frequency alignment is underdamped, which correlates with the trouble HR had getting the speaker's bass to speak in balance with its upper ranges.

Higher in frequency in fig.3, the Octave 6's response, averaged across a 30° horizontal window centered on the tweeter axis, slopes upward in the midrange, reaching a peak between 1 and 2kHz. Above that region the speaker's output is impressively even, before dropping off above 17kHz or so. Fig.4 reveals that the Morel's horizontal dispersion is wide and even, with the small suckout at 12kHz filling in to the speaker's sides. However, the tweeter becomes quite directional in the top audio octave. This suggests that the Morel will sound a little too mellow in large rooms when used well away from boundaries, though that is when the speaker's bass will sound best. In the vertical plane (fig.5), a major suckout in the crossover region develops more than 5° above the tweeter axis, which confirms HR's finding that the speakers' sound is optimally balanced when they sit on high stands.

Fig.4 Morel Octave 6 Bookshelf, 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 Morel Octave 6 Bookshelf, 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.

Turning to the time domain, the Octave 6's step response on the tweeter axis (fig.6) reveals that the tweeter's output arrives a little earlier at the microphone than the woofer's, but the fact that the decay of the tweeter's step smoothly blends with the start of the woofer's step indicates optimal crossover design, as shown in fig.3. The decay of the woofer's step has some ripples with a period of around 0.75 millisecond. These correlate with a ridge of delayed energy in the cumulative spectral-decay plot (fig.7) at the frequency of the on-axis response peak. Other than that, however, the Octave's 6's waterfall plot is impressively clean, especially in the region covered by the tweeter.

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

Fig.7 Morel Octave 6 Bookshelf, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

I have been impressed by the performance of Morel's tweeters ever since I first measured one, the soft-dome MDT33, 25 years ago. But I was disappointed by the Octave 6 Limited Edition Bookshelf's measured performance, in particular the high-Q port resonances and the response peak at the top of the midrange (though Morel says that this peak is due to the grille). These spoil what would otherwise be an excellent report card.—John Atkinson

Morel America
1301 Hempstead Turnpike, Suite 1
Elmont, NY 11003
(877) 667-3511

Nellomilanese's picture

Who needs a subwoofer? just get a tiny bookshelf LOL
I have a VERY hard time believing a bookshelf speaker with a single 6" woofer can go to 30Hz at -3dB. Please....the B&W sub with a 200W amp and a 8" driver goes to 32Hz at -3db!
Silly me...all along I could've just get this tiny bookshelf and have a FULL RANGE sound. In an instant these speakers have wiped out the hi-fi industry...need to sell your CM9 guyz...useless...a floorstanding with dual 6.5" drivers and it only goes to 30Hz but at -6db! pffff losers!
Someone needs a Nobel prize for reinventing physics here...more likely it's time to cut the cr@p...both the manufacturer and Stereophile for having the guts to even publish these specs.

John Atkinson's picture
See the measurements sidebar for the actual LF extension. The Morel's port is tuned to 53Hz, which corresponds to the -6dB point.

John Atkinson
Editor, Stereophile

seank's picture

I assume that's a typo.

John Atkinson's picture
seank wrote:
I assume that's a typo.

Yes it was. Good catch. I have corrected the price to $1299.00/pair.

John Atkinson
Editor, Stereophile

Nellomilanese's picture

But burying the REAL -3db point in a graph at the last page is just fraud. This fraud is perpetrated by the manufacturer making such ridiculous claims and Stereophile for allowing it.
How many americans do you think can read a graph like that John? assuming they understand anything about -3db point and it's meaning.
Yet the bogus spec is printed right there -30HZ.
I suggest you start doing that if you want to keep any (little) trace of credibility left.
This is like me selling jewellery with a 18k gold sticker and price on it....but then burry inside the last page of the owner's manual the fact that it's actually scrap metal.
Because make no mistake, when it comes to speakers, the difference between 30HZ at -3db and 57HZ at -3db, is the difference between gold and scrap metal painted in gold.
Best regards.

John Atkinson's picture
Nellomilanese wrote:
burying the REAL -3db point in a graph at the last page is just fraud.

I really hope you're smiling when you accuse me of fraud.

Nellomilanese wrote:
How many americans do you think can read a graph like that John? assuming they understand anything about -3db point and its meaning.

I assume that people read the measurements sections we publish, otherwise what would be the point of publishing them.

Nellomilanese wrote:
I, as an honest person, would've start the article in BOLD letters ... I suggest you start doing that if you want to keep any (little) trace of credibility left.

Please ask yourself how you know that the Morel's LF response doesn't extend down to the manufacturer's claimed frequency - it is because Stereophile told you so, right there on our website and in the print magazine. So please don't lecture me on our supposed lack of credibility.

John Atkinson
Editor, Stereophile

JoeinNC's picture

"So please don't lecture me on our supposed lack of credibility."

Nellomilanese's comment was over the top, but then you respond by... lecturing him. C'mon, really?

There is some validity to the point that manufacturers' specs are stretched beyond credibility, and that Stereophile's measurements (while I don't doubt they are accurate) are not as readily deciphered by those with less technical backgrounds. Or shorter attention spans. (They've already had to wade through stories about kleptomania and where the sun rises to get to the subject of the review.)

Yes, "fraud" is too strong a characterization, but the attitude with which some of the reviews are written might invite such comments, and then your vaguely threatening response to what is obvious trolling ("I really hope you're smiling when you accuse me of fraud.") doesn't elevate the conversation or win any converts.

Thus endeth my "lecture." Make of it what you will.

Just the facts's picture

I have been under the impression that the smallest acoustical pressure difference generally discernable was 3db.
Hardly gold to scrap to most.
If the Mfr stated its -3db point was 57hz and the reviewer noted it was down 3db at 30hz, that's -6db.
You probably are not in the market for 6" woofer stand mounts anyway.

John Atkinson's picture
Just the facts wrote:
I have been under the impression that the smallest acoustical pressure difference generally discernible was 3dB.

A difference of 3dB is often quoted, but it is is not correct. 1dB is more typical and depending on the bandwidth covered and the frequency range in question, a level of just 0.1dB can be detected. See my article on the significance of small measured differences between 2 speakers at

John Atkinson
Editor, Stereophile

Anon2's picture

This looks like a nice product. Debates over the low-end aside, the product has a nice response curve.

Stand-mount speakers are like compact sedans. Both still fall short of the performance of larger products. But both exhibit performance, in a small size, that far exceeds what was available 20-30 years ago.

We are debating in this forum the frequency response of the Morel stand-mount in the vicinity of 30 Hz. 20-30 years ago the debate would have centered on whether a similarly sized speaker was capable of any meaningful response around 50 Hz.

Another thing I like is that there is a raft of medium-grade stand-mounts coming out with relatively flat, or reduced prices from predecessor models. B&W, Kef, Amphion, Dynaudio, and now Morel, are getting a sense that consumers see $1,500 to $2,500 as the viable price range for an upgrade of stand-mount speakers ("affordable" for the editors who may need a sense of what that threshold might be for real consumers). $3,000 is not an "affordable" price for products in this quality grade.

Stand-mounts have their limitations; they have their benefits, too. One thing is clear though: there is a lot more than ever to be had in a small package.

corrective_unconscious's picture

There's no debate about whether this specific, small speaker has any meaningful response near 30hz. (A -6 point anywhere around 53hz puts that "debate" to rest.) That is not what the debate is about. The debate is about manufacturers' specs and then, apparently, how many "Stereophile" readers actually read the Measurements sidebars with comprehension.

crenca's picture

That article of Elizabeth Newton's was not "wildly insightful". It took NPR's flawed assumptions and ran with them with radical subjectivism and a healthy dose of neo-Marxist analysis that seems to live only in the darkened and insular world of academia. Sure, it was written in a lively style that affirmed enjoyment of music, but those who seek "fidelity" are not against enjoyment of music despite what you seem to think.

You guys need to get out more and read more - try some of the classic canon where you will find real "insight"...

Catcher10's picture

As I was reading this I was expecting to see "...and all for just $5,999.." Still $2,799 for a small bookshelf with 6" mid/bass to me is high. But yes does signal hopefully the audio companies are starting to see the bubble bursting....Upgrading today means a 2nd mortgage.

Archimago's picture

A few concerns and objections...

Russell Dawkins's picture

JoeinNC, I think John's response to the hysterical blatherings by Nellomilanese was measured and entirely appropriate, and where do *you* get off in lecturing John?
Catcher10 - it's $2499, not $2799 and, yes, it appears the high priced boutique bookshelf bubble may be leaking if not bursting with such as Andrew Jones newest three way bookshelf, the Elac Uni-Fi B5 at $500 the pair.

JoeinNC's picture

Russell Dawkins> "and where do *you* get off in lecturing John?"

The same place *you* get off in your response to me. It's a comment section. If you invite comments, should you should not expectthem?

Nellomilanese's picture

So i'm calling bs on ridiculous claims by the manufacturer and you think that's "histerycal blatherings"? Interesting and fascinating at the same your reaction proves EXACTLY why manufacturers can make such outrageous claims.
Can you imagine the equivalent claim in the auto industry?
The whole credibility of a brand would be wiped billions in fines....but in audio? everything goes....the many drooling, open-mouthed idiots with money burning in their pockets believe everything.

A. Hourst's picture

This strange preamble has been brilliantly answered by Archimago on his website, but there’s still a few points that call for attention. First, the major part of this ferocious tirade is occupied either by an odd and meaningless anecdote about an ex-girlfriend (Both “really…?” echoing one another are supposed to tell us what? That both comments were as obvious as they are useless…? “Sun rise in the east” and “euphonia does not mean accuracy”…?), or by a confession of faith, so a lot of words for not much. Second, there’s the typical audiophile reaction “what even is reality?”, found in Ms. Newton’s text, which elsewhere should bring up the question of the validity of our senses, but here is intended to diminish the concept of reality itself. Sad. And then the idea that the truth is like a hot bath in which you can relax (“One that requires the least psychic effort or brain processing on my part to hook me in”); we have to wonder if the reasoning methodology employed by Mr. Reichert isn’t the same as his music enjoyment one. Because fidelity means “faithful” or “truthful” to the original, as annoying and difficult to assess this can be. To determine if the truth have been said, or the signal faithfully transmitted, in any field, require “psychic effort” and a level of consciousness beyond simply enjoying a pleasure… By any meaning of the words, to lose oneself into something means to lower one’s critical thinking and get partial to what’s being enjoyed. Not to get closer to its objective value, which is what “fidelity” is about. Like Archimago said, you could get an extremely euphonic system, very pleasing, and far from faithful. That’s the paradox of the high-end: audiophiles can not admit that some design choices are a deviation from fidelity. Instead, they will distort the meaning of the word “fidelity” so it will adapt to the feeling associated with one piece of equipment.

The audiophile community is embedded in a world of confusion regarding each people or each equipment’s role, which is materialized by a confusion regarding the terms they employ. Elizabeth Newton navigates with difficulties between philosophical, sentimental and practical concept, and comes up with what finally appears to be a tasteless soup. The artist role is to touch your emotions, the hardware role is to relay the information. To those who claim that their audio gear have spirituality, I would ask: what spirituality does have the molecules of air between you and the singer of a live performance?

michaelavorgna's picture

I've come to realize there are different approaches to hi-fi. I don't see this as "confusion", unless someone feels they are in a position to dictate to everyone the means and ends of listening to music.

Since hi-fi is a hobby, there is no one correct approach to its enjoyment. The definition and understanding of the word "fidelity" as it pertains to hi-fi is not carved in stone, as is evident in reality. Beyond the fact that we can disagree over what we are being faithful to, i.e. some limited set of measurements taken somewhere along the reproduction chain or the experience of music, the steps involved in the recording process and the reproduction process are littered with choices that have nothing to do with some fictional notion of objectivity.

If we could first agree on an appropriate sampling of state-of-art equipment from the recording studio out to the listening room, we would find wildly varying sound. If this notion of some "objective reality" is the goal of hi-fi, then we have obviously failed miserably in its pursuit. However, that's simply not the case. In reality, music reproduction has led to the inspiration to create, among other things more music, which has shaped our society. I can think of no higher goal.

My approach to hi-fi defines fidelity along these lines:

"Let's redefine high fidelity as being faithful to the passion for and discovery of music. This means that the best hi-fi is the one that perpetually fans the flame of this passion." from my AWSI "Why Music Matters Most" (2010)

If someone else wants to define fidelity as a common objective goal guided by measurements and these arbitrary "rules" extend into what happens in the recording studio all the way through to my living room, and further that everyone's experience is dictated by this necessarily limited and unrealistic goal, I'll happily to stick to my approach since the outcome of listening to music, in reality, far exceeds such mundane concerns.

Michael Lavorgna
Editor, AudioStream

A. Hourst's picture

"Let's redefine high fidelity as being faithful to the passion for and discovery of music"

Let's redefine truth as what makes me feel comfortable.

michaelavorgna's picture

If you prefer to be uncomfortable when listening to music, that's fine by me ;-)

John Atkinson's picture
michaelavorgna wrote:
If you prefer to be uncomfortable when listening to music, that's fine by me

The late J. Gordon Holt used to say that as live music can sound aggressive and harsh, so should a good audio system when reproducing the same music. To me and others, this was a non sequitur: yes, some live orchestral music can sound harsh, particularly when the brass are playing flat-out. I also know from my experience as a violinist that the sound of a string instrument with your ears inches away from the instrument has an astringency that has disappeared at the audience's distance. But live classical music never sounds like a tweeter resonance, a woofer cone breaking up, or an amplifier driven into non-linear behavior.

John Atkinson
Editor, Stereophile

michaelavorgna's picture a recording which employed close miking, turn it up too loud, and stick my ear against the tweeter for an aggressive and harsh experience ;-)

Michael Lavorgna
Editor, AudioStream