Spendor D7 loudspeaker Measurements

Sidebar: Measurements, from April 2015 (Vol.38 No.4)

Sam Tellig wrote about Spendor's D7 loudspeaker in his column, "Sam's Space," in the September 2014 issue, concluding that this English floorstanding speaker was "a splendid Spendor," and that "one might seriously question the need to spend any more than $6495 for a pair of speakers" (footnote 1). What he found especially rare, for a relatively small speaker, was the D7's "authority, weight, and speed. You could spend far more for a speaker and not get such a fast, highly resolving sound, and such a sweet midrange."

We don't usually publish measurements of the products covered by Stereophile's columnists, unless the writer feels that there is something about the sound that merits further investigation. But in the case of the D7, some readers complained about the lack of measured results in comments posted to the website reprint of Sam's report. In response, Jay Rein, of Bluebird Music, the brand's North American distributor, posted that "Bluebird Music has repeatedly said the D7s are the best speakers Spendor has ever made. We are more than willing to back up this claim by providing a pair of D7s to be measured and tested as you do in your regular reviews."

Accordingly, I asked Rein to ship a pair of D7s to me for measurement. (The serial numbers were 324000289 and '290.) I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Spendor D7's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses.

Fig.1 Spendor D7, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The D7's voltage sensitivity is specified as 90dB/W/m; my estimate was close, at 89.3dB(B)/2.83V/m, which is above average. The D7's nominal impedance is specified as 8 ohms, with a minimum magnitude of 4.5 ohms. Fig.1 shows the measured impedance magnitude (solid trace) and electrical phase angle (dotted). The minimum impedance was indeed 4.5 ohms, at 183Hz, and the magnitude remains above 6 ohms in the upper bass and from the upper midrange upward. Although the phase angle exceeds 40° at 53 and 76Hz, the magnitude is high at those frequencies, ameliorating the extra current demand imposed by the impedance phase.

Fig.2 Spendor D7, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel level with mid/woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

Though there is a slight discontinuity at 125Hz, the impedance traces are free from the small wrinkles in the midrange that would suggest the presence of cabinet resonances. Nevertheless, when I investigated the vibrational behavior of the enclosure panels with a plastic-tape accelerometer, I found a strong mode at 391Hz that was most pronounced on the side panels level with the midrange/woofer (fig.2). This mode disappeared lower on the panel, replaced by one much lower in magnitude, at 348Hz. It's possible, therefore, that despite this mode's high amplitude, the areas affected are small enough that it won't lead to coloration or midrange congestion.

Fig.3 Spendor D7, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with nearfield responses of: mid/woofer (green), woofer (blue), port (red), with complex sum of nearfield responses, respectively plotted below 500Hz, 500Hz, 950Hz, 300Hz.

The black trace above 300Hz in fig.3 shows the Spendor's farfield anechoic response, averaged across a 30° horizontal window centered on the tweeter axis. Below 300Hz, the black trace shows the complex sum of the nearfield outputs of the mid/woofer, the woofer, and the vent in the base of the enclosure. The green trace is the mid/woofer's output, the blue trace the woofer's, and the red trace the vent's, each scaled in the ratio of the square root of the radiating area. The port has a peak in its upper-midrange output, but this will be subjectively inconsequential given that the port fires away from the listener. The port's output covers a much wider bandpass than in a traditional reflex alignment; perhaps that slight discontinuity in the impedance traces at 125Hz is due to the vent's actually behaving with some aspect of transmission-line tuning, which extends the port's output higher in frequency than is usually the case. The port's output is also low in level, which suggests that the alignment has been optimized for the fact that the port is so close to the floor.

The minimum-motion notch in the woofer's response (blue trace) occurs at 27Hz and the mid/woofer's notch at 22Hz, but the two drive-units' outputs in the mid- and upper bass are otherwise similar. However, the woofer's output starts to gently roll off above 100Hz, and is 3dB below the mid/woofer's output at 500Hz. The D7 is thus a "2½-way" rather than a three-way design, with the low frequencies shared by the LF drivers. This seems to be an effective technique, judging from ST's favorable comments about the D7's bass reproduction: "I take back everything bad I've written about floorstanding speakers: troublesome bass, poor integration of drivers in the nearfield, etc. . . . Few loudspeakers can convey the power without the aid of a pesky subwoofer or two. Or without pooping out. The D7s could, given enough power."

Fig.4 Spendor D7, 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 Spendor D7, 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 5–10° below axis.

Higher in frequency in fig.3, the soft-dome tweeter's output drops off rapidly above 18kHz, but the D7's farfield response is impressively even, with a couple of small peaks balanced by equally small dips. Whether this will translate into a flat perceived balanced will depend also on the speaker's dispersion, of course, and the D7's horizontal radiation pattern is shown in fig.4. This graph reveals that the mid/woofer's output drops off rapidly to the speaker's sides above 2kHz, which results in an off-axis flare at the bottom of the tweeter's passband. Whether the flare results in a slightly bright balance, or the off-axis lack of energy half an octave lower in frequency results in a slightly polite balance, will depend both on the music played and on the listening-room acoustics. Fig.4 also indicates that the tweeter maintains its top-octave output over a wider angle than is usual with a 1" dome. In the vertical plane (fig.5), the D7 should be listened to within 5° of the tweeter axis, which is 35" above the floor.

Fig.6 Spendor D7, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Turning to the time domain, the Spendor's step response on the tweeter axis (fig.6) is reminiscent of BBC-legacy designs, with the tweeter connected in inverted acoustic polarity and its output leading that of the positive-polarity lower-frequency units by a quarter of a millisecond or so. The decay of the tweeter's step blends with the start of the woofers' step on this axis, however, implying optimal crossover design. The decay of the D7's output is clean in the tweeter's passband (fig.7), though a ridge of delayed energy is apparent at 4.2kHz, the frequency of a small peak in the D7's HF-axis response.

Fig.7 Spendor D7, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Overall, the Spendor D7 offers excellent measured performance. I must agree not only with Sam Tellig but also with Martin Colloms, who wrote of the D7, in the July–September 2013 issue of The HiFi Critic: "here is a modern interpretation of the classically neutral, accurate and well integrated design."—John Atkinson



Footnote 1: The D7's price was reduced to $5995/pair in January 2015 (add $1000 for a premium finish).
COMPANY INFO
Spendor Audio Systems Ltd.
US distributor: Bluebird Music Limited
2299 Kenmore Avenue
Buffalo, NY 14207
(416) 638-8207
ARTICLE CONTENTS

COMMENTS
fy415's picture

I appreciate the subjective reviews, but really look forward to the measurements. It's hard to compare different speakers (and other products) when different people reviewed them. Measurements, however, take away a significant amount of confusion and doubt.

John Atkinson's picture
fy415 wrote:
I appreciate the subjective reviews, but really look forward to the measurements.

The D7's measurements are published in the April 2015 issue of Stereophile and are now appended to this Web reprint.

John Atkinson
Editor, Stereophile

allhifi's picture

Quote: ...." Measurements, however, take away a significant amount of confusion and doubt."

Indeed, Stereophile's measurements can be very informative --and the magazines regular 'testers' no doubt can "interpolate" specific "data/readings" with subjective impressions.

Personally (with loudspeaker tests) I prefer to see a linear frequency response as wide as possible, but critically in the
50 Hz -to 5-KHz (preferably to 10-KHz) range.
LF loading is absolutely critical, preferring to see a damped (or over-damped) design.

With that said, I wonder if there is a distinguishable "measurement" differences between the PSB T-3, and KEF Reference -1's (same retail value) --and also one's I've auditioned side-by-side many times.

Quite simply, the (current) KEF Reference 1 is in a completely different league than the T-3's --the "subjective" impressions leave the PSB in the dust-bin. There is simply no comparing the PSB T-3 to the spectacular REF-1's (KEF).

Observing the construction details (not to mention million-dollar design investment of the KEF's)reveals impressive attention to (vital) details: Six-to-eight BOLTS, secure the drive-units to the (advanced) baffle board, while the impressive MF/HF driver itself is additionally secured (and strengthened)by a metal-plate (between driver and baffle-board) --again anchored my metal, threaded BOLTS !

(You'd think many/most similarly priced (and more expensive loudspeakers) also bolt the driver's to the enclosure --not so.)

Summarizing, test measurements are an essential tool, but so are design details (as described) that are almost NEVER examined or disclosed. Why ?

peter jasz

JunkyJan's picture

...I'm really tired of being treated like "Well-to-do Professional who knows Law / Medicine / whatever but baffled by technical mumbo-jumbo". Without seeing real measured values, I feel like I am being asked to part with cash based on a review writer's ability to write flowing prose and praise. I am in the market for new speakers at the moment - and I will do some listening tests - but my "candidate speaker list" selection should be based on more than just the most flowery -sounding reviews.

allhifi's picture

Listen to the current KEF Reference -any model.

Search over.

pj

andy_'s picture

Is the absence of measurements a blip, a permanent change to the format of loudspeaker reviews or perhaps something in between?

JunkyJan's picture

No, it's been going on for years. Some (paper)magazines will give you a full technical run-down with measurements as well - "HiFi News and Record Review" used to do that, no idea if they still do. IIRC "HiFi Answers" or "What HiFi" started this "pure subjectivity" trend back in the late 70s or early 80s.

Also remember that test equipment is DARN expensive, and people who know how to operate it even more so. So since the early 80s many magazines went the route of "Bombard the reader with enough pretty euphemisms and the advertisers will shower us with money" (increasing circulation is always the driving motivation).

The problem for me, being on the verge of shelling out the equivalent of (U.S.)$10,000 on a pair of speakers, is that I can no longer stomach the lack of actual measurement to back up however reasonable the claim of the author may be. Without it, it all becomes just one man's opinion :(

brian2010's picture

At current exchange rate these speakers are only $5,500. Only? Measurements in the lab are a part of the picture, I agree. But the part that matters is one's own ear and no measurement is going to make that much difference if you like the speakers. Outside of power handling capabilities I find measurements more than a bit obtuse, but to each their own.

remlab's picture

In the twenty years I've been reading Stereophile, I have never seen a measurement acompanying his reviews. In a way, It's like a having a little, tiny "Absolute sound" subscription!

John Atkinson's picture
Quote:
In the twenty years I've been reading Stereophile, I have never seen a measurement accompanying his reviews.

I don't routinely publish measurements of the products that are covered in our monthly columns. However, I do measure some of these products when I have the time and opportunity, even those reviewed by Sam Tellig. See, for example, www.stereophile.com/content/musical-fidelity-v90-dac-da-processor.

John Atkinson
Editor, Stereophile

remlab's picture

.

fy415's picture

"I don't routinely publish measurements of the products that are covered in our monthly columns. However, I do measure some of these products when I have the time and opportunity...."

I think I can understand how columns are autonomous, and don't necessarily follow the same format as full articles/reviews. But what are the chances that a product covered in a column will also be given a "formal" review (and measured in the lab), without the review becoming redundant?

Whatever the reasoning for the current situation re: whether or not a product is measured, it seems unfair (and is certainly frustrating) that, as a reader, I am not able to get consistent and complete information about the different products that I read about. With different writers having different musical/acoustic preferences and writing styles, the technical measurements are the only thing that provides all these different pieces of equipment context, and an even playing field.

I believe I read that a speaker manufacturer (Magnepan? My apologies if I'm mistaken) has repeatedly declined to provide review samples because they don't agree with the magazine's testing protocols (or, to be more precise, their speakers don't "measure well"). That is certainly their prerogative, and readers of this magazine can make their own decisions in response.

But I believe that more effort should be put into lab testing all products that are given substantial coverage in the magazine. In my opinion, measuring only "some" of these products is not adequate, and unfair to the the manufacturers whose products went through the rigors of lab testing, regardless of the results--products with "good" measurements may not receive enough credit for their achievement, and products with "bad" measurements may be unduly punished because their peers avoided the tests.

Is it possible that a manufacturer can exploit Stereophile's practices, i.e., the columns' autonomy (and logistical difficulties in arranging for lab testing), to get a subjecive review published without fear of having its technical deficiencies exposed in a lab test?

John Atkinson's picture
fy415 wrote:
I believe that more effort should be put into lab testing all products that are given substantial coverage in the magazine.

It comes down to resources. As I said, I try to measure some of the products that are covered in our columns, but it is impracticable to measure all such products. As was said in another comment, lab testing is time- and resource-consuming, which is why so many magazines and webzines don't do it at all. With Stereophile, we publish as many measurements as is possible within the constraints of budget and a monthly publishing schedule.

fy415 wrote:
In my opinion, measuring only "some" of these products is not adequate, and unfair to the the manufacturers whose products went through the rigors of lab testing, regardless of the results--products with "good" measurements may not receive enough credit for their achievement, and products with "bad" measurements may be unduly punished because their peers avoided the tests.

That's a fair point.

John Atkinson
Editor, Stereophile

GQ's picture

If you looking for measurement, you can see a very nice one in HI FI Critic magazine.

http://www.spendoraudio.com/Images/Spendor%20D7%20HiFi%20Critic%20Sept%202013.pdf

fy415's picture

Thank you for the link to the technical review.

It's not as thorough or as descriptive as Mr. Atkinson's tests and descriptions. The product was most likely tested in a different location, with different equipment, and possibly different protocols. Still, this gives me and other readers a more complete picture of the speaker being reviewed.

Thank you.

To Stereophile: I'd much rather not have to go to different sources for different aspects of a review for every product that interests me. Please, please try harder to publish complete reviews.

remlab's picture

John
Why doesn't Magnepan just use Sam's column to safely shield themselves from your evil measurements? That way, they can be happy and you can be happy!

andy_'s picture

I suspect Magnepan's concerns may be valid about how potential customers may interpret the standard set of Stereophile measurements of their door sized panel speakers. For example, how many manufacturers that have worked hard to get a flat bass response to within +/-X dB are comfortable with Stereophile showing a bass rise in the measured frequency response and their specifications appearing to be false? Despite JA's comments in the accompanying text I am pretty sure it is not going to stick with a fair few readers who have no interest in measurement techniques and the physics of sound.

corrective_unconscious's picture

That measurements with a review of their speakers would reveal proprietary design details. Now, they must mean "widely reveal," because a lot of manufacturers could do such measurements (and more) of Magnepan products on their own.

Magnepan must also mean "certain measurements," because their speakers have been reviewed within the half year in one of the British audio mags which did offer at least some measurements along with reviews.

Perhaps an alternate idea to yours of Magnepan being worried about how readers would interpret such measurements as we find in Stereophile would be that Magnepan is worried about how Stereophile's measurements are conducted.

Richard Vandersteen (among others) has voiced considerable skepticism regarding some of the measurements' procedures and findings in the past, as one example. But he said so openly in the Manufacturers' Comments after allowing one of the II series to be reviewed....

It would be interesting to know for sure.

Roger That's picture

One of the main reasons why I quit buying What-HiFi magazine back in the nineties was the lack of any objective measurements.

That’s one of the major assets of Stereophile, with all the (great) work made by John Atkinson.

Please don’t turn Stereophile into another (near) useless audio resource. It’s not like I don’t value the reviewers opinions (they’re actually fundamental), but without any kind of objective data it’s only that, one informed (but personal) opinion.
That’s great for a column article, but not so great for a review, imho.

Thank you for all your great work.

DaveinSM's picture

I agree! I really, really appreciate John Atkinson's measurements, plus they are always thoughtfully and insightfully explained to boot.

Bluebird Music's picture

Bluebird Music has repeatedly said the D7s are the best speakers Spendor has ever made. We are more than willing to back up this claim by providing a pair of D7s to be measured and tested as you do in your regular reviews. You only have to say the word and we would be delighted to send a pair. Frankly, I would like to see how they measure too! - Jay Rein, Bluebird Music

John Atkinson's picture
Bluebird Music wrote:
We are more than willing to back up this claim by providing a pair of D7s to be measured and tested as you do in your regular reviews. You only have to say the word and we would be delighted to send a pair.

That's an excellent idea. I will publish a measurement follow-up of the D7 in the March or April 2015 issue. (It's too late for the February issue, which ships to the printer on Monday.)

John Atkinson
Editor, Stereophile

Shangri-La's picture

Does Stereophile have plans to review the Spendor D9? Really interested in the new flagship.

Mark McLaughlan's picture

Hi,

I had a pair of SPENDOR A9's until a year or two ago and liked them a lot except they needed a fair volume before the bass seemed to be at one with the rest of the music - well possibly still not quite "as one".

I am wrestling between the Spendor D7 and the new KEF R7 which sound rather good and look real pretty. Unfortunately the Spendor dealer is in another state so I can't listen to them before committing.

Any recent experience with these two speakers please?

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