Blumenhofer Acoustics Tempesta 20

Hardware Review

Blumenhofer Acoustics Tempesta 20
Friday, January 21, 2022
horn loudspeakers
Richard Barclay

Blumenhofer Acoustics have been designing loudspeakers for more than four decades. Specialising in two-way horns, they defy the archetypal view of German engineering by building speakers that are all about stirring human emotion. Thomas Blumenhofer’s mission is to “bring the concert into the home” by convincingly reproducing the sensory energy that is experienced during live music performance, and his experimental DV-3x16 demonstrates the extremes to which he will go to achieve this. Music lovers with listening spaces too small for this near two-metre deep modular loudspeaker with up to six horn-loaded 16-inch woofers per channel needn’t despair, there is a generous menu of more modestly-proportioned designs to choose from. 

The Tempesta 20 is one such, it’s a floor-ported, divergent bass reflex design with a mylar membrane, HF compression horn and an eight inch paper sandwich mid/bass driver with a claimed 40Hz-20kHz (+/-2dB) frequency response. It offers 150W of power handling from a slender but sturdy 27kg enclosure that stands 116.5cm (46 inches) high. The cabinet is constructed from one inch HDF and is internally braced to minimise resonance, a consideration extended to the crossover which is internally housed in its own chamber well away from the drive units. The front of the speaker gently slopes backwards, an aesthetically flattering form that also improves time-alignment by compensating for the different path lengths of the drive units to the listener. Care has also been taken to minimise the distance between the acoustic centres of the drivers to achieve a smoother vertical off-axis response at the crossover frequency. 

Available in a choice of standard, special and premium exotic wood veneers, each pair of speakers is unique in appearance. The review sample I received are Macassar, a straight-grained species of ebony dashed with delicious accents of toffee. Fit and finish is first rate as you would expect at this price, the Tempesta series is backed by a very generous 10-year warranty. Gold-plated tellurium copper input terminals facilitate bi-wiring or bi-amping, though for this review I stuck with single-wiring and used the supplied jumper leads to bridge the LF and HF terminals. Sensitivity is a reasonably high 92dB and impedance a tube-friendly 8Ω.

 

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Engaging the built-in passive Impedance Linearisation filter makes Tempesta even more benign by flattening the impedance of the compression driver, reducing the frequency response variations that occur when it is driven by an amplifier with high output impedance. As most solid-state amps have very low output impedances, this effect is most evident with tube amplification, particularly designs that employ little or no negative feedback. The manufacturer recommends listening with the filter in and out to decide which presentation is preferred. While it makes no audible difference with my solid-state Yamaha amp, the effect it has on a Mastersound valve amp is marked. Bypassing the linearisation filter raises the output level of the compression driver above that of the woofer, resulting in a top-heavy voicing. In the context of this SET amp, at least, the desired balance is obtained with the filter engaged.

Set up
The enclosures are designed to be anchored to the floor using the supplied spikes, there are two captive outriggers at the back and the front spike screws into an M8 thread just in front of the port opening. There is a small amount of adjustment in the spikes to raise or lower the height and this fine-tunes the port by increasing or decreasing its ground clearance.

It’s often advisable to avoid placing speakers that have an omnidirectional bass response between 60cm and 140cm from the wall, this avoids the worst effects of bass cancellations caused by boundary interference (a.k.a. SBIR). In smaller rooms this usually means setting them close to the wall and balancing the response by moving the listening position further away from the wall behind it. Tempesta’s down-firing port meant I was able to place it as near to the rear wall as an unvented floorstander without the additional boominess that would have been experienced with a rear-vented design. I also did not perceive exaggerated or lethargic bass resulting from the port’s closeness to the floor. The divergent reflex tunnel is tuned to 35Hz, a frequency that would be excited by a ceiling height of around 16ft. In my 11ft high room the system is well-damped. 

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Blumenhofer recommends toeing-in the speakers to where the tweeters intersect behind the listening seat, 10 to 15 degrees off-axis is a suggested starting point. The optimal angle depends on listener preference, distance and the acoustics of the room, but with horns you generally want to avoid on-axis listening due to their tendency to beam. Horn waveguides control dispersion by directing more energy forwards and providing a smoother roll-off as you move off-axis. This makes high frequency reflections off the side walls less harmful and reduces the need for both toe-in and acoustic treatment. With horns it can often be beneficial not to treat the side walls so as not to over-absorb the middle and lower frequencies. I normally use side wall absorption to sharpen image precision but with Tempesta I obtained a more natural balance with only the back wall treated. The sweet spot within which a coherent and defined image is maintained is very generous, this speaker is an excellent choice for shared listening. Indeed, Blumenhofer designed the Tempesta series with home cinema as much in mind as music and there are centre, surround and subwoofer options available for multichannel setups. 

Sound quality
I kick things off with a 100wpc Yamaha A-S3000 integrated amp and Schiit Audio Yggdrasil DAC upstream and am immediately impressed by the insight these speakers provide. Captured with a simple pair of binaural mics, Little Crimes by Melissa Menago is a beautifully intimate vocal performance in which the only effects heard are provided naturally by the acoustics of the venue. Menago's cover of Leonard Cohen’s Hallelujah harnesses the reverberation of the 130-year-old Brooklyn church to great effect and Tempesta does a stunning job presenting her effortless ability to modulate both the timbre and power of her voice and express the lyrics with maximum emotional impact. Every time I listen to this track on these speakers the hairs on the back of my neck stand on end, the midrange presence is spectacular. 

Joined by her two June Divided bandmates on If The Fire Goes Out, the soundstage suddenly grows wider. A cajon (box drum) and ukulele now occupy the peripheries beyond the outer edges of the right and left speakers and are bathed in the same, glorious church ambience. At lower listening levels Tempesta 20 is among the clearest and most open-sounding I’ve auditioned in this room, detail retrieval and dynamic response is simply superb. There is such immediacy to the sound of Menago’s fingers on the fretboard of her guitar as she changes chords that – with your eyes closed – you’re fooled into believing she is in the room with you. This is a known benefit of horns, they come to life more easily at lower volumes than lower sensitivity speakers. Tempesta is not however an all-out horn design, it uses a midbass driver with reflex loading to reproduce everything below 1.2kHz. 

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I was initially concerned this might be a marriage of convenience and result in timing issues but the integration between the two drive units is superb, there is no evident lag or disjointedness between the high and low frequencies. I cue Daft Punk’s Random Access Memories next and the opening eight bars of Give Life Back to Music explode from the speakers like a cluster of paint bombs, ejecting layer upon layer of vibrant colour into the room in all directions. The sonically sparser verses provide some sensory respite – only until the rhythm invades my being and syncs my right foot to the groove – but there is still plenty of ear candy to stimulate the senses. Nile Rodgers’ signature guitar licks, the shimmering tinkle of triangles and, of course, the extremely hooky backbeat hand claps that transport you back in time and onto the dance floor of a 70s nightclub; Tempesta presents all of this in amazingly crisp detail.

Game of Love begins with J.R. Robinson’s delicate cymbal caresses that hang in the air for what seems like an eternity, setting the song’s melancholic mood. These are juxtaposed with a staccato kick drum pattern that punctuates each bar, a pattern that Nathan East mirrors with a funky but pared-down bass riff that leaves space for the track to breathe. This is when I fully appreciate the control and tunefulness of the Blumenhofer’s low end, the kick drum and bass guitar both start and stop on a sixpence and you can easily differentiate their respective pitches and textures. Robinson’s tom fills remind me of Russ Kunkel’s improv at the end of James Taylor’s Fire And Rain; Kunkel’s toms aren’t soaked in reverb of course, but Tempesta delivers them both with impressive slam and scale.

Random Access Memories is deservedly lauded for its exceptional production but, while its beefy bottom end may be ideal for exploring a speaker’s low frequency credentials, its polished mids and highs tell us little about how forgiving a speaker is of edgier recordings. Crash Test Dummies’ God Shuffled His Feet is a far brighter production by comparison and will glare proudly on highly revealing systems. This album confirms that the Blumenhofers are tuned on the brighter side of neutral, there is an emphasis on the upper harmonics in Brad Robert’s bass-baritone vocals and an accentuation of the tinny timbre of Mitch Dorge’s drum kit. This is, perhaps, a natural consequence of voicing a speaker so that it delivers stunning realism with live acoustic performances, it can be too revealing of overly-processed studio creations. 

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It’s also possible that my ancillaries aren’t the best match for Tempesta. My Yggdrasil DAC delivers lots of top end detail and although the MOSFETs in my Yamaha provide a touch of analogue warmth, it is still a relatively neutral-sounding amplifier. This pairing works marvellously with my own loudspeakers that are quite polite in their delivery but can be too much of a good thing with more ebullient designs. Replacing the Schiit D/A converter with a Bricasti Design M3 brings a slightly warmer and smoother presentation, the top end becomes sweeter and the leading edges of transients are softened a touch, especially when the DAC’s filter is set to Minimum Phase. The overall reproduction is still, however, a little on the dry side. 

Blumenhofer promotes their loudspeakers as tube-friendly and I was keen to hear how Tempesta responds to glowing glass in the signal chain. Swapping out the Yamaha for a Mastersound Compact 845 triggers a much bigger transformation than I anticipate. I notice straight away that this 30wpc Class A single ended triode (SET) amp brings out the warmer side of these speakers, the low end gains far more mass and the top end is dialled back slightly. I still get that exciting, edge-of-the-seat listening experience but the chiaroscuro – the balance between light and shade – has become kinder to poorer recordings and makes fatigue-free listening possible with a broader range of music. 

After some time it is also clear that the 845 encourages Tempesta to relax a little and take deeper breaths between notes. They are afforded more time to develop and there is a more equitable balance of attack, sustain and decay with less emphasis on the leading edge. This can be heard in David Gilmour’s unplugged In Concert where each instrument has more body and texture. The resonance of the nylon-strung guitar Gilmour uses in High Hopes is richer, his vocal is more haunting, and the slam of the percussion and thump of the upright bass carry more heft when Tempesta is partnered with the Mastersound. Even the feedback from the audience is fleshed out to the extent that you feel like you’re sitting in the front rows of the Royal Festival Hall surrounded by ‘crazy diamonds’, Tempesta conveys their vocal enthusiasm with incredible energy and intensifies the already rapturous atmosphere.

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The Mastersound 845 Compact proved to be a fabulous match, the only compromise I perceived when switching from solid-state to SET amplification was a modest reduction in low end control. The looser and more weighty bottom actually benefited acoustic genres of music which were, by comparison, somewhat dry and over-damped before tubes were introduced. Those who listen predominately to beat-driven electronic music may, however, prefer the stronger grip and sharper contouring that solid-state amps exert on these speakers.   

Before my time with the Blumenhofers was up I experimented with some shielded speaker cables. I tend not to review using cables that differ from those in my own system as it introduces yet another variable that must be factored into the evaluation. However, I made an exception this time when the distributor suggested I try some from Tiglon, his effusiveness over its synergy with Tempesta was very persuasive. The DF100SP-HSE model celebrates the Japanese cable manufacturer’s 10th anniversary and uses dip-formed oxygen-free copper for an ultra pure conductor, patented magnesium separate shield sheathing and additional magnesium filters on both ends for maximum EMI and RFI noise rejection. The best cables, in my view, tend to be those that enrich the listening experience without drawing attention to themselves; the latter can be fun initially but it’s usually the former that provides long-term contentment. The DF100SP makes no sonic imprint that I can hear, it is perfectly poised and does an admirable job of getting out of the signal path. Its transparency and low noise floor provides an exceptionally black background that makes Tempesta's ability to resolve microdynamics even more effortless. This is not an inexpensive cable but it compliments these speakers extremely well and shifts more focus away from the gear and onto the music, which is what hifi should ultimately strive to achieve.

Verdict
Blumenhofer’s Tempesta 20 delivers a thrillingly detailed and dynamic sound with convincing scale from an enclosure that’s both slender and elegant enough to be accepted into most living spaces, even small ones thanks to its ease of placement. Its ruthlessly revealing character requires sympathetic system matching. Best results are achieved with tubes but – with a little extra effort – solid-state amplification can also work very well. If you’re set on recreating the unfiltered, front-row energy of the live music experience, this speaker will knock your socks off.

Specifications: 

Type: horn loaded 2-way floorstanding loudspeaker
Crossover frequency: 1.2kHz
Drive units:
Mid/bass: 8-inch P2F® paper sandwich woofer 
Tweeter: 1-inch compression horn throat with with 1.75-inch Mylar membrane 
Nominal frequency response: 40Hz-20kHz ±2dB
Nominal impedance: 8 Ohms with switchable impedance linearisation filter
Connectors: gold-plated tellurium copper bi-wire/bi-amp
Sensitivity: 92dB
Dimensions HxWxD: 1165 x 240 x 346mm
Weight: 27kg
Finishes: various real wood veneers.
Warranty: 10 years

Price: 
From £6,750 at time of publication
Manufacturer Details: 

Blumenhofer Acoustics
www.blumenhofer-acoustics.com

Distributor Details: 

Connecting Music
www.connectingmusic.co.uk