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“Hoellstern… has this been going on?” Paul Carrack on the road

The soul singer’s UK dates provided a solid platform for new amps and speakers from Germany

The seemingly limitless wave of German innovation is visible again in a new generation of amplifiers, point source cabinets and line array from two manufacturers in the south of the country.

Hoellstern Amplifiers and ProAudio Technology GmbH (PAT), just a few kilometres apart in the area of Freiburg, are building a reputation at home but could now be on the cusp of wider international recognition. Hoellstern, a brand founded under the auspices of ASID GmbH by engineer Udo Höllstern in 2001, has developed Class D amplification, digital signal processing and proprietary ‘Konfigurator 2’ software for the pro-audio market, while PAT now has a full range of speakers, rigging and amplifiers designed for high-end touring and installation by founder and MD Thomas Müller and his team.

Pete Sharman, co-founder and co-director of Yorkshire-based rental company Isophase Audio and a graduate of LIPA, is the first UK customer for Hoellstern and ProAudio Technology and the first anywhere, he believes, to tour all of these products on a major scale.

“We were looking for more efficient, Class D amplifiers for our existing system,” he explains, “and Hoellstern was recommended by one of their distributors we’d met. We checked out the specs, they looked promising and we got in touch with Udo. We auditioned many Class D amps with onboard DSP but none could match the efficiency or clarity of the Hoellstern units, so we started to add them to our hire stock. We subsequently discovered Hoellstern amps have system set-ups to simulate many manufacturers’ proprietary amps, so we used the amps for multiple projects powering products from Alcons Audio, d&b, L-Acoustics and others…”

“The universal DSP loudspeaker library is a kind of hobbyhorse for us, and a very useful feature for our customers,” Udo Höllstern notes.

“It was Udo who mentioned ProAudio Technology loudspeakers, as they had been working on some projects together, so we went out to Germany for a demo,” continues Sharman. “Initially looking for a point source, stackable system for smaller jobs, we demo’d the HT16 Tourset system – the trapezoid cabinet with three 18-inch subs – and it was pretty amazing. We A-B’d it with similar systems on the market but it soon became apparent that there were many advantages to the Tourset: better handling, stacking for transport and of course the primary goal of high-output linear audio. So we took a set, plus some monitors and smaller in-fill cabinets.

“The conversation evolved into a discussion of line array, which we knew was in development at PAT, and we made it clear that we really needed something more efficient and less amp-hungry: amps are expensive, we figured a 4-channel Hoellstern amp could run 16 boxes if it was right, twice as many as we were currently running. Thomas finalised the designs in the light of these talks, and we took delivery of the new VT20 line array in time for last summer’s festival season.”

One of these was Yorkshire’s Underneath The Stars, a boutique trip into electro-acoustic pastures and the perfect showcase for the VT20’s phase linearity and clarity at distance. But the system has proved itself beyond the paisley, being immediately used for the speech bubbles of cosmetics company LUSH at a conference at the Bournemouth International Centre. “It was perfect for the corporate environment too,” confirms Sharman, “and we’re still in on-going development with Thomas about things like DSP settings and transportation. It’s his baby, but we can make suggestions for the real-world practicalities that we deal with every day.”

All the DSP is in the Hoellstern amps, Sharman explains. “The speakers are designed to harness the DSP powers in the amplifiers, so Thomas has made them specifically to utilise the Hoellstern DSP. It’s a different approach to most companies, one that cements the close relationship between Hoellstern and PAT: Thomas has conformed his designs to be one of the most genetically compatible on the menu.”

Isophase now has the largest system anywhere, and it was needed at the cavernous Birmingham Symphony Hall when freelance engineer Graham Bonnett was mixing FOH for veteran blue-eyed soul crooner Paul Carrack as part of an extensive UK tour.

“I came to the tour after mixing Paul’s latest album Soul Shadows,” says Bonnett later. “I’m experienced in both fields so feel equally comfortable working in the studio or live.”

Anton Dunbar from Isophase assured Bonnett he would enjoy working with the PAT VT20 gear. “The first time we ran it in production rehearsals, I was immediately impressed by the lack of colouration,” he reflects. Now, after mixing with the VT20s for thirty shows on the tour, he finds them smooth sounding and coherent with low distortion. “System or mix EQ decisions we’re making seldom seem related to driver artefacts. I’ve not yet had any need to push them hard, but the headroom seems effortless, with no trace of power compression. The Hoellstern amplifiers are extremely powerful and integrate well into the system.”

PAT’s Thomas Müller backs up Bonnett’s observation: “ProAudio Technology manufactures complete high-performance loudspeakers systems with an ‘integrated system thinking’ in the south of Germany. Highest quality components and the state-of-the-art DSP amplifiers are the basis of every speaker and every resulting system.

“A lot of practical features, well engineered accessories, easy and fast handling, the know how from over 15 years in rental and touring business and the five years warranty offer decisive advantages for musicians, bands and rental companies.”

The larger venues on the Carrack tour have combined PAT’s groundstacked point source and flown line array, while other variations have included a straightforward 12-per-side left-right hang with ground subs, for example at Cambridge Corn Exchange or Leicester De Montfort; sometimes a flown centre cluster if there’s a proscenium arch or a tricky room acoustic, as at Victoria Halls in Stoke; even a point-source box on a lighting bar in smaller theatres, plus delays and ground subs as required.

Bonnett again: “Rival PA systems seem to me to have their own sonic signature – which I often find myself wasting time and brainpower trying to reduce – but the VT20s present more of a ‘blank canvas’, giving us more control of the voicing. We’ve had some great results in notoriously difficult halls, with favourable comments from audience members and house staff, due partly of course to Pete Sharman’s expert system design and implementation!”

In Germany, the VT-20 has been picking up new customers at the rate of one a month since its launch. Hoellstern amplifiers, meanwhile, are attracting attention across Europe but a break into the US has one caveat, for now: “They only run on 230V,” points out Sharman, “and that’s why they’re so incredibly efficient. There’s no 110V mode, yet. The amps have advanced peak and RMS limiters, very high-resolution programmability – two or three decibel places on the dB cut and boost – all on Hoellstern’s in-house software and DSP platform. But the main thing is the efficiency: at Birmingham Symphony Hall it was a 16-hang per side running off one 2U amplifier, per side. Without the subs, that would be off one 13amp plug each side! You can get four VT20 elements – or four subs – per channel from the biggest model, which is the 20.4-DSP.” (“An amp city was not necessary!” as Höllstern puts it.)

Sharman: “They’re all networkable too: you can build recallable memory files telling you what each channel is driving, which input, which output… all via USB to RS485 using a laptop interface. The programmable mains input limiters let you scale down the draw, especially handy for outdoor gigs on small generators.

“The VT-20 has lots of headroom,” he reflects, “it’s easy to mix on and it never seems to need much EQing: you feel confident when you hang it that it’s going to do what it says it will do – which is everything we wanted, really. Having been forced to use venue systems at a couple of stops on the tour due to rigging restrictions, we all noticed much lower distortion and more transparent sound when returning to the VT20 – confirming the system design is superior.”

Or as Paul Carrack’s trusted engineer Graham Bonnett puts it: “I’m not looking forward to times of having to work without them…”

Top pic: Paul Carrack on tour earlier this year. Middle pic: Pete Sharman (left) and FOH engineer Graham Bonnett. Bottom: VT20 hang in the Birmingham Symphony Hall