Alta Audio Hestia Titanium loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Alta Hestia Titanium's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. (I measured S/N HST02706.) The Alta's voltage sensitivity is specified as a higher-than-average 90dB/2.83V/m; my estimate was much lower, at 82.5dB(B)/2.83V/m. In part, this will be due to the fact that my figure is based only on the speaker's frontal radiation, whereas the Hestia Titanium, being a dipole design in the midrange, will also be putting out almost as much energy behind it as in front of it. But this is still a low sensitivity, and will be exacerbated by the speaker's impedance magnitude, which drops to just 1.75 ohms at 264Hz (fig.1). There are also demanding combinations of magnitude and electrical phase at 50Hz (4.3 ohms and –46°) and 450Hz (2.9 ohms and +49°). Though its impedance remains above 6 ohms in the treble, the Hestia Titanium will need to be driven by a powerful amplifier if it is not to be starved of current.

118AHTfig1.jpg

Fig.1 Alta Hestia Titanium, electrical impedance (solid) and phase (dashed) (5 ohms/vertical div.).

There is a major discontinuity at 100Hz in the impedance traces, as well as minor ones at 200 and 400Hz. This behavior suggests that the enclosure has resonance problems, and indeed, when I investigated the behavior of the woofer bin with a plastic-tape accelerometer, I found a high-level mode at 203Hz on the rear panel (fig.2), and a lower-level mode at 98Hz on both sidewalls.

118AHTfig2.jpg

Fig.2 Alta Hestia Titanium, cumulative spectral-decay plot calculated from output of accelerometer fastened to rear of bass bin (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

But it was when I examined the nearfield response of the front-panel port that loads the woofer that I found disturbing behavior that correlated with the discontinuities in the impedance plots. The port's output (fig.3, blue trace) covers a wide passband, from 15 to 85Hz, but then has a sharply defined peak visible at 100Hz, with peaks lower in level at 200 and 400Hz. The two lower-frequency resonant modes are sufficiently severe to disturb the woofer's nearfield output (red trace). When Jim Austin writes, "While bass instruments had great impact through the Hestias, sometimes they didn't sound precisely as a conscientious sound engineer might want them to sound," I believe he is referring to the effect of this behavior.

Higher in frequency in fig.3, the sum of the midrange units' outputs—all three seem to have an identical frequency response—is shown as the green trace. This splices the sum of the nearfield outputs to the farfield response at 450Hz. The peak between 100 and 500Hz appears to be real and not an artifact of the nearfield measurement technique, as it was also evident in wide-range farfield measurements. The upper-midrange output is flat, but then there is a 5dB step down in output before the midrange units hand off to the ribbon tweeter. I suspect that this lack of presence-region energy affected my estimate of the Hestia Titanium's sensitivity.

118AHTfig3.jpg

Fig.3 Alta Hestia Titanium, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield responses of midrange units (green), woofer (red), and port (blue), respectively plotted in the ratios of the square roots of their radiating areas below 350Hz, 420Hz, and 1600Hz.

Fig.4 shows how these individual responses sum in a 30° horizontal window centered on the tweeter axis. As recording engineer Phil Schaap said when he heard the Altas in Jim Austin's room, "These speakers have too much bass." I admit that the rise in low-frequency output in this graph will be due in part to the nearfield measurement technique, which assumes a half-space environment for the drive-units; ie, a baffle that extends to infinity in both planes. Nevertheless, the Hestia Titanium does have too much bass.

118AHTfig4.jpg

Fig.4 Alta Hestia Titanium, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield midrange, woofer, and port responses plotted below 300Hz.

It also looks as if it has too much lower-midrange output, at least on axis, but the fact that the speaker behaves as a dipole above the woofer's passband needs to be taken into account. The Hestia Titanium's lateral dispersion, normalized to the response on the tweeter axis, is shown in fig.5. You can see from this graph that the Alta's response rolls off rapidly to the sides between 300 and 700Hz, which in the listening room will tend to ameliorate the excess of energy in the same region shown in fig.4 and result in a more neutral midrange output. Higher in frequency, the contour lines in fig.5 are even and uniformly spaced, something that tends to correlate with stable, accurate stereo imaging. The tweeter does become relatively directional above 10kHz, which might make the speaker sound too sweet in large or well-damped rooms.

118AHTfig5.jpg

Fig.5 Alta Hestia Titanium, 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.

The vertical dispersion is shown in fig.6, again normalized to the response on the tweeter axis, which is a high 43" above the floor. The speaker's balance doesn't appear to be as fussy about listening axis as JCA's listening suggested, but a suckout does develop at 1.6kHz more than 10° below the tweeter axis; I think that is what he was compensating for when he tilted the speakers forward for his auditioning.

118AHTfig6.jpg

Fig.6 Alta Hestia Titanium, 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 5–15° below axis.

The Hestia Titanium's step response on the tweeter axis (fig.7) reveals that the tweeter and midrange units are connected in inverted acoustic polarity, the woofer in positive polarity. (I checked the woofer's polarity by momentarily connecting a 2V dry cell, positive to positive, across the Hestia's terminals; the cone moved away from the enclosure, as predicted by fig.7.) The cumulative spectral-decay or waterfall plot on the tweeter axis is shown in fig.8. The decay is impressively clean in the region covered by the ribbon tweeter, but there is a ridge of delayed energy at 1.2kHz that, all things equal, I would expect to add a small degree of nasality to the speaker's sonic signature.

118AHTfig7.jpg

Fig.7 Alta Hestia Titanium, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

118AHTfig8.jpg

Fig.8 Alta Hestia Titanium, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

There is a lot to admire in the measured performance of Alta Audio's Hestia Titanium, and it looks as if designer Michael Levy has worked hard to balance the omnidirectional radiation pattern in the bass with the dipolar behavior in the midrange and the tweeter's forward-firing pattern. The excessive low frequencies can be adjusted to some extent with careful placement, but I remain bothered by the resonances I found in the woofer's and port's outputs, and that delayed energy at the top of the midrange units' passband.—John Atkinson

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COMMENTS
dalethorn's picture

"....the bassoon that enters 13 minutes into the first movement of the Shostakovich: it's positioned in space with far greater precision than the wavelength of the fundamental tone would allow."

There are a few things where I find it useful to focus on a fundamental or a harmonic, but the whole tone and how it interacts with the room is the final arbiter for so many things.

spacehound's picture

I'm not at all sceptical about his 'titanium' stuff, but these speakers have far too many drivers to ever sound coherent.

It's the inevitable consequence of putting enough stuff in to make it appear to people with more money that sense that they are worth 32,000 dollars.

(And it always amuses me that so many go on about 'space' around the speakers yet so many buy big and expensive floorstanders where there is no 'space' at all above what is often the most reflective and resonant part of the room.)

Michael Levy's picture

While I agree that melding multiple drivers is not an easy task, the reviewers agree that the Hestia Titanium does just that, or to quote Jim Austin from this review: "When I listened to a live version of "Corcovado," from disc 3 of Stan Getz's The Girl from Ipanema: The Bossa Nova Years (4 CDs, Verve 823 611-2), singer Astrud Gilberto stood on a stage, a few feet up from where I sat in the fourth or fifth row. Getz and his tenor sax were on the same level, farther back and slightly to the right. João Gilberto was on Astrud's right, just inside the left speaker, obviously seated, his guitar in his hands. He was human-sized, and his voice emerged from a spot maybe 18" above the sound of his guitar—as it would in an unamplified live performance. Astounding.
Read more at https://www.stereophile.com/content/alta-audio-hestia-titanium-loudspeaker-page-2#4PYKvtcdgtxsUB7d.99

otaku's picture

I heard the Alta Audio FRM-2 bookshelf speakers at the Brooklyn show in 2014 and was very impressed. Maybe bigger is not always better.

Michael Levy's picture

Our speakers are designed to match the room in which they are played. The Celesta FRM-2s are designed for moderate sized rooms, such as those that would be found in a Manhattan apartment, the Hestia Titaniums favor larger rooms. they both create an accurate representation of the space where the original recording was recorded, with the Hestias more able to portray the full grandeur of that space.

mtrot's picture

What speaker terminal jumpers appear in the picture? Thanks.

Michael Levy's picture

We provide AntiCables jumpers with the Hestia Titanium Speakers

eriks's picture

What a funny review of a funny speaker. Let me touch on one of many things stated which made me giggle:

"Levy told me that the crossover between the midrange and the tweeter is asymmetric, the tweeter coming in much faster than the midrange fades out. That asymmetry adds complexity."

Asymmetrical in this sense means that the poles, or order of the crossover is not the same on the low pass as the high pass section. This is quite typical in flat-baffle designs. This doesn't add any complexity at all and is often necessary for proper phase and amplitude matching between drivers. The designer in this case seems to have only had partial success.

The "dipolito" is a sad riff indeed. This is no such thing. While D'Appolito designs may have asymmetrical (2nd and 3rd order for example) crossovers the good doctor is very much aware that higher order filters minimize lobing and interference. Using a first order low pass filter on the mids is why you have the big dip when vertically off-axis at 1 kHz.

On the positive side, cutting off 6-7" mid-woofers at 1 kHz will prevent the comb filtering / interference effect you were concerned about. They should play as a single surface, or rather, they should _if_ they were the same make and model of driver, but they aren't. This speaker really is an endless garden of delight when it comes to curiosities.

Best,

Erik

Michael Levy's picture

Do you consider this only partially successful? Quote Jim Austin: When I listened to a live version of "Corcovado," from disc 3 of Stan Getz's The Girl from Ipanema: The Bossa Nova Years (4 CDs, Verve 823 611-2), singer Astrud Gilberto stood on a stage, a few feet up from where I sat in the fourth or fifth row. Getz and his tenor sax were on the same level, farther back and slightly to the right. João Gilberto was on Astrud's right, just inside the left speaker, obviously seated, his guitar in his hands. He was human-sized, and his voice emerged from a spot maybe 18" above the sound of his guitar—as it would in an unamplified live performance. Astounding. or It's a Saturday, after midnight, and I'm listening to Steely Dan's Aja, remembering Walter Becker, who died a few weeks ago. These extraordinary musicians—Steve Gadd, Joe Sample, Larry Carlton, Lee Ritenour, Wayne Shorter, plus the core Steely Dan crew—are arrayed across my living room and beyond its walls, their instruments like orchestra sections. I've never heard this recording with such depth, weight, and relaxed separation.
Read more at https://www.stereophile.com/content/alta-audio-hestia-titanium-loudspeaker-page-2#PVAtScO97mLPcdUJ.99estia-titanium-loudspeaker-page-2#PVAtScO97mLPcdUJ.99 , or Steve Guttenberg on U tube, I heard one of the best systems of my life last night

https://www.youtube.com/watch?v=8otW-hzmMhc

eriks's picture

I think you misunderstand.

Only in a very narrow context did I consider this speaker design any sort of success. I said: "is often necessary for proper phase and amplitude matching between drivers. The designer in this case seems to have only had partial success."

As for the rest, to paraphrase Tim Gunn, "If that's what you like, you should buy more of it."

Erik

Michael Levy's picture

No, I think you misunderstand. The measure of a speaker is in the listening. Anyone who has ever constructed a technically perfect speaker knows this. They sound like crap. The only way to properly design a speaker is through a beta test group as we did. The members of the group included a Grammy awarded recording engineer, a symphony conductor, several reviewers, and a few fellow audio design engineers. They were tasked to compare the sound to live natural music. The process took over two years. That is what resulted in the comments I quoted from Jim Austin in this review, but as Steve Guttenberg's post shows, his was not the only one. It is a naive designer who thinks that the proof of his design is in the measurements. They are at best a guide.

ksigman's picture

My reference speakers are Alta Audio FRM2 Celesta; a 2-driver model that works beautifully with my space which is a (small) 100+ year-old apartment in NYC. Would I jump up without hesitation to these extraordinary larger (Titanium), meant for a larger space--but with the same essential qualities that I adore in the FRM2--if I had a larger space? Absolutely. I have heard them in various venues (spaces), many times, and with various supporting equipment, including my own amplifiers, and with my own personal supply of music. I have heard them in Levy's house, others' houses, at shows and (the best so far), at the Rhapsody Audio show room in NYC. Give them a listen. The soundstage and imaging is truly extraordinary--to my ears. There are no perfect speakers sound-wise (Holy Grail?) and we all have our own personal preferences as to what that might be, and it can't be based only on measurements or preconceived ideas about what a proper design should be.

Timbo in Oz's picture

Q. If QUAD's successors in China can give us essentially perfect speakers for 1/2 to 1/3rd this one's price?

Why does this one cost so much?

A. Greed! and BBB aka 'bullshit baffles brains'.

Since the late 1970s I've owned a pair of 2-way spheres which are almost as good as 57s or 63s and the cost me less than $900 to buy and a bit more to position correctly.

They go lower and play louder than 57s.

Money and display?!

98, 99, 100, ... change hands 101, 102.

Are ANY of you interested in music at all?!!!

Sigh!

TIA folks.

Timbo in Oz

JimboJumbo's picture

You were very kind to this by saying “there’s a lot to admire”.

For $32K I would expect a lot more precision in the tests.

I have measured/tested so many better speakers/monitors than these; that cost 15% of the asking price for these.

There is hardly any test that it performs really well in.

Horizontal off axis response is pretty good. Step response is appalling. CSD is a mixed bag; take out the ribbon tweeter (they usually perform well in CSD tests) and what have you got. Frequency response is barely acceptable. Impedance and phase plots are concerning. Cabinet design is average.

For $32K I would expect a lot more precision. This price range can buy you some exceptionally good stuff; perhaps some active ATC’s.

This system is basically - hate to say it - an example of an unrefined design approach.

There are $10K kit speakers and $5K active 2 way monitors out there that absolutely annihilate this in terms of design and measured performance. For example, several years ago, I measured these 2 and they performed exceptionally well . .

https://vaf.com.au/collections/signature-speakers/products/signature-i-93mkll

http://mackie.com/products/hrmk2-series

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