Bryston Middle T loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Bryston Middle T's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. (The grilles were left off for all the measurements.) My estimate of the Middle T's voltage sensitivity was 85dB(B)/2.83V/m, significantly lower than the specified 88dB/W/m.

Though the Middle T's impedance is specified as 4 ohms, my measurement indicated that the magnitude remained above 4 ohms up to 30kHz (fig.1, solid trace). However, while the electrical phase angle (fig.1, dotted trace) is benign up to 8kHz or so, it becomes increasingly capacitive above that frequency, exceeding –45° above the audioband, where the magnitude also drops to as low as 2 ohms. The Middle T therefore starts to resemble a short circuit at ultrasonic frequencies, which will have an unpredictable effect on the partnering amplifier, depending on the program material. This impedance plot is very different in the top octaves both from those published in other reviews of this speaker and that supplied with the speaker, and was taken with an Audio Precision test system. I therefore repeated the measurement using DRA Labs' MLSSA system in impedance testing mode, and got a result identical to fig.1.

Fig.1 Bryston Middle T, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The impedance traces are free from the small wrinkles in the midrange that would suggest the presence of enclosure resonances. However, the rear half of the Middle T's cabinet sounded very lively to a knuckle rap, and when I investigated the vibrational behavior with an accelerometer, I found a strong mode at 500Hz on the sidewalls level with the midrange drive-unit and adjacent to the ports (fig.2), with another strong mode at 250Hz level with the upper and lower woofers. The section of the sidewalls adjacent to the midrange unit was much better damped. Whether or not these resonances will degrade sound quality will depend on the areas of the affected panels. It is fair to note that Kal Rubinson didn't note any midrange congestion or coloration that might have resulted from this behavior, though I see that he commented that "there seemed to be just a bit more lower midrange than I thought was right."

Fig.2 Bryston Middle T, 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 two woofers behaved identically, as did the two ports. The blue trace in fig.3 shows the response of the woofers, measured in the nearfield below 350Hz and in the farfield above that frequency, while the red trace shows the nearfield response of the ports. Below 350Hz, the green trace in this graph shows the nearfield response of the midrange unit, with the farfield output of the midrange and tweeter on the tweeter axis shown above that frequency. The woofers appear to peak in the upper bass, but this is primarily an artifact of the nearfield measurement technique. The notch at 27Hz in their output confirms that this is the tuning frequency of the twin ports and that their combined output peaks between 20 and 50Hz, implying good low-frequency extension. There are two peaks in the ports' output between 300 and 450Hz; though both are relatively low in level, the peak lower in frequency does give rise to a suckout in the woofers' nearfield output.

Fig.3 Bryston Middle T, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield responses of midrange unit (green), woofers (blue), ports (red), respectively plotted below 350Hz, 350Hz, 500Hz.

Higher in frequency in fig.3, the woofers' low-pass rolloff is very shallow. Their output at 1kHz is just 6dB below that of the midrange unit, and while it rolls off rapidly above 1kHz, there are two peaks in the treble. I don't think these peaks are due to interference between the two woofers as I could hear their effect on pink noise with just the woofers operating. However, it's possible that they're masked when the midrange unit is active. The midrange driver's response is impressively flat, though the tweeter's output gently rises on axis. The tweeter's primary dome resonance occurs around 25kHz, which is significantly higher in frequency than the resonance shown in other published reviews.

Fig.4 shows that the Bryston speaker's bass is down by 6dB at the port tuning frequency, as expected, which correlates with KR's finding that the bass extension is "substantial." The Middle T's farfield response has a slight "smile" characteristic, the decade between 500Hz and 5kHz generally 2–3dB lower in level than the regions to either side. However, the slight peak just above 3kHz might tie in with KR's comment that the Brystons "seemed to place images just a bit more forward in terms of distance, though not of character."

Fig.4 Bryston Middle T, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield responses plotted below 300Hz.

The Middle T's lateral dispersion, referenced to the response on the tweeter axis, is shown in fig.5. The contour lines in this graph are generally smooth and evenly spaced, correlating with the good imaging performance. This graph shows that the suckouts between 3 and 4kHz and around 15kHz in the on-axis response fill in to the speaker's sides, which will render the in-room treble smooth. Overall, however, the Middle T is relatively directional in the top two audio octaves, which will tend to balance the excess of energy in this region on axis. In the vertical plane (fig.6), the Bryston's output doesn't change much over a wide angle (±10°) centered on the tweeter axis, which is 38" above the floor.

Fig.5 Bryston Middle T, 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 Bryston Middle T, 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.

In the time domain, the Middle T's step response on the tweeter axis (fig.7) indicates that all four drive-units are connected with positive acoustic polarity. The smooth blending of the tweeter and midrange steps indicates optimal crossover design, while looking at the individual steps reveals that the outputs of the midrange unit and woofers arrive coincidentally at the microphone. The cumulative spectral-decay plot on the tweeter axis (fig.8) is generally impressively clean, though with a slight ridge of delayed energy at the frequency of the peak in the woofers' response.

Fig.7 Bryston Middle T, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.8 Bryston Middle T, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Although I was somewhat puzzled by the crossover between the Middle T's woofers and midrange unit, and didn't like to see that lively enclosure, the speaker's measured performance generally indicates a well-balanced design. And again I must point out that excellent cumulative spectral-decay plot. It is uncommon to see a large, affordable tower speaker with so clean an initial decay.—John Atkinson

COMPANY INFO
Bryston Limited
677 Neal Drive
Peterborough, Ontario K9J 7Y4
Canada
(705) 742-5325
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COMMENTS
william.meredith's picture

Made by Axiom, the K-Mart of Canadian speaker manufacturers.

Allen Fant's picture

The Aerial is way over-priced.

funambulistic's picture

The first time I saw the Model T, I thought, "That's an M80 - dual tweeters and all!" The Middle T looks like a beefed up M60. I am sure, in working with Bryston, Axiom has developed a fine loudspeaker (I have not heard either Bryston model) but I cannot help but be reminded of when I bought into the Axiom hype when the M22 was the FOTM on another review site. Not bad for the price but always left me unfulfilled...

Stanley1's picture

I have a pair of Axiom M60s and they are wonderful sounding speakers. I have to admit it took longer than usual to break them in, but was well worth the wait. Such clarity and sweetness with plenty of thump. I also have Harbeth Compact 7ES3 speakers which I love. But make no mistake the Axiom speakers are every bit as good and even better for rock and roll.

corrective_unconscious's picture

I don't know who else Axiom has been OEM'ing drivers for over the years, but it now appears they're trying to go upmarket.

I suppose the drivers could be of fine quality. What strikes me is how utterly conventional the Bryston speakers appear to be in every way. They might be good values for all I know, but there's definitely a complete lack of any unique selling proposition or visible tech breakthrough.

william.meredith's picture

My findings with the Bryston Middle T are consistent with those of the reviewer. Bryston's lack of expertise with speakers is reflected in the Middle T's lack-luster performance. It just doesn't present music as accurately and realistically with the type of imaging and soundstaging that can be experienced with more established and proven brands.

CliffS's picture

Ever since Bryston was sold off, it never quite was the same company.

Partnering with Axiom is just a prime example of squeezing out as much profit in a box as possible. These Bryston speakers are using the exact same mediocre tweeter found in most Axiom speakes.

JA revealed the cabinets are poorly braced in his tests and Kal shows just how ridiculous the grilles are and the ugly shape of the cab.

These would be fine speakers at $2k/pair but cannot compete with speakers in its price class and this is what I found when hearing them at CES. Bryston priced these speakers like they've been pricing their amps, way too high! But this is high end audio so if you slap on a high price it must be good, right?

Anon2's picture

I'll give Stereophile and Bryston credit for an honest effort and honest review with this product.

This is a first effort for Bryston. While they went to a maker of less expensive speakers, they did avail themselves of some manufacturing and design resources that would have been a difficult and resource-draining endeavor to do internally. They may go on to better things. They may abandon the effort after this first product roll-out. Time will tell.

Their manufacturing partner, while a maker of less expensive speakers, certainly has some knowledge of what it takes to make a more expensive speaker (though perhaps less R&D and actual experience than companies that devote themselves to obtaining these hard-earned findings from years of research).

This is the reason why I find it interesting, though I am not the expert who did this review, of how a first try at making a speaker gained such favorable comparisons to the notes of past reviews of the products of some very experienced, even eminent, manufacturers' products.

It is all part of the mystery surrounding the speaker industry. There are some manufacturers whose products are the result of unquestioned devotion to acoustic research (in small letters) and materials science. The results, which I have had the opportunity to hear at product expos, "speak" for themselves. Some of these manufacturers allow some of this technology to trickle down to their lower priced models. These products often gain positive reviews, no doubt with some recognition of "you get what you pay for." Still, the value per dollar proposition is good.

Then, in an industry with what I think many would say are reasonably low barriers to entry, we get a fascinating, and frustrating at times, array of products. Some of these products are in, what I have written in these forums before, this $3,000 to $10,000 gray range. This range of products, and others are free to put their own limits on it, is where the price for value equation becomes fuzzy, particularly speakers.

Yes, a $5,000 speaker is better than $1,000 speaker. But is it 5x better? Above the $10,000 level, for those who can afford it, there are products of evident merits given the prices charged to the consumer.

I have stayed out of this "middle range" of products mainly for financial reasons. But had I the resources to afford products in this middle range, I would be asking questions about what I am getting.

There are some unquestionably great speaker products, with credible R&D and advanced materials science, in the products above this price range. There are some surprisingly great values in the $1,500 and below range; Stereophile has ably reviewed many of these products.

It is this $3,000 to $10,000 range, with better electronic and driver components perhaps, but in the same low-tech encasement of the lower-end products (perhaps better braced) that make me wonder what all the extra money is going towards.

One observation I'd make in defense of all speaker manufacturers to some extent is that any high initial profit mark-ups, particularly when inventory stocking is involved, are offset by the physical distribution and inventory carrying costs of bulky, damage-prone, and slow moving physical inventories (compared to other consumer goods). Currency exchange rates and less-than-container/truckload shipping also impact some manufacturers, again my guess.

My concern is how much of the customers' money can and should go to cover these costs. Sure it is the consumer's choice to do what he/she sees fit. But with other unrelenting expenses, it's going to be a choice that collides with many other expenses of life.

An interesting solution of one very established name in speakers, and in another case the very maker of the Bryston speaker reviewed in this article, is to sell directly to the consumer through internet/phone orders. This centralizes any inventory stocks, probably promotes more of a make-to-order manufacturing process, and reduces physical inventories. I'm sure the consumer gets some savings out of all of this.

I often go back to a late 2008 Stereophile interview with a leader in coalescing speaker technology with advanced materials. The remarks of this speaker manufacturer resonated greatly with me (and if I daresay, with the writer of the interview). It often motivates me to ask these questions.

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