Music and technology: Reverb wars

Music and technology: Reverb wars

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King's College Chapel, Cambridge, U.K. There's an IR for that. (Via Wikipedia)

COLLEGE PARK, Md., March 19, 2014 – While digital-audio workstations (DAWs) and notation software packages generally come packed with an almost complete line of plug-ins and audio toys, no package on the market currently provides a truly satisfying reverb.

Conversely for composers, nothing bespeaks of a lack of acoustic sensitivity (or general taste) than the submission of dry recordings. For composers seeking a complete audio editing or midi mockup package, a third party reverb product is a must.

This review compares the great granddaddy of convolution reverb, Audio Ease’s Altiverb, with the relative newer and much more affordable QL Spaces (EastWest). The results of this head-to-head comparison are beyond surprising. But for those who aren’t reverb aficionados, a brief initial explanation is in order.

Reverb packages fall into one of two camps: the “algorithmic” reverb, and the “convolution” reverb. Algorithmic reverbs generally use mathematical algorithms to estimate the sound of a given space. Convolution reverb actually samples the acoustic response of real spaces – be they cathedrals or closets – and affects the source recording with the result of these “impulses.” Whichever approach you prefer may be a matter of taste or application, as algorithmic reverbs often can sound tinny, while convolution reverbs have been criticized as being flat and overly dark by comparison.        

The acoustic needs of pop and classical music diverge sharply where reverb is concerned. For  classical and chamber style recordings or mock-ups, judiciously applied convolution reverb is clearly the way to go. We tested these two products with a variety of tracks including a midi realization made with low quality instruments, a high-quality midi orchestral mockup, a recording of a men’s chorus, and a professional string quartet recording, which needed just a bit more distance.

QL Spaces. Screenshot of console interface.
QL Spaces. Screenshot of console interface.

The immediate difference one notices between QL Spaces and Altiverb is the interface. Spaces has a simple, clean set-up with very few options, relying on the user to find a good preset, which is tweaked slightly to achieve the desired result. Altiverb is a much deeper program, going so far as to allow musical gates, increased delay controls, and even the combination of a synthetic reverb on top of the convolution reverb in order to enable additional brightness in the sound.

This last item is an important remedy to the perceived flatness of convolution reverb, affording users with the opportunity to add a bit of high-end algorithmic sheen to the final product while retaining the realism that convolution reverb can offer.

Furthermore Altiverb opens the door to an online reverb community, allowing users to download free new impulse response patches (IRs ) from either the company or individual users, or to even create one’s own impulse response patches for any space imaginable. (The full set of digital tools is provided with the Altiverb install package.)  Just as this interview was being written, for instance, this writer was able to download a new IR of King’s College Chapel in Cambridge, UK.

Screenshot of Altiverb interface.
Screenshot of Altiverb interface.

Users will notice that Altiverb includes the named IRs for some very famous places, such as L.A.’s Walt Disney Concert Hall. QL Spaces offers more mysterious and generic names, such as “NY String Hall.” Furthermore Altiverb gives more IR options, including a host of vintage gear along with strange spaces such the cabin of a Sikorski helicopter or a small underground cave.

Altiverb provides a number of interactive charts and views regarding both the acoustic characteristics of a space as well as the methods used to achieve the capture of the IR. Users can synthetically modify the placement of the speakers in the IR process, varying the quality of the IR presets significantly by estimating the placement of the source ensemble.

Where QL Spaces fights back against Altiverb’s plethora of options involves their claim

to achieve superior convolution results with their “source specific” method of recording impulse responses, which attempts to emulate “instrument specific” positions in various spaces. While not every preset seems to represent the full richness of this technique, the results were nevertheless palpable. One did not seem to desire the algorithmic brightness option available in Altiverb with many of the QL Spaces IRs, while satisfying results were generally quicker to be achieved. Furthermore while they do not boast this in their own advertising, Spaces proved to be extremely CPU efficient.

Both products offer an extremely useful project-specific menu of presets for use in targeting specific types of IRs to specific source tracks. In both programs users may look at a list of IRs specifically designed for various musical uses such as string recordings, vocals, or orchestral recordings. Given Quantum Leap’s claim to “source specific” IRs, a welcome update would include a slightly deeper menu of ensemble specific IRs, especially with regard to chamber music. This would only further bolster the accurate “fast track” claim to fame that Spaces is garnering across the web.*

The results of comparing these two packages proved somewhat unexpected. All four test recordings were immediately improved by applying a number of presets from both packages, with even the cheap and tinny midi mockup achieving some acoustic breadth and believability when it was placed in Altiverb’s Walt Disney Hall and Space’s “Northwest Concert Hall.” The most humble midi studio, it seems, can profit greatly from a good convolution reverb.

The high quality midi mock-up fared very well in both applications across a variety of concert hall IRs, with Spaces and Altiverb in a dead heat regarding achievable quality (Spaces, as throughout most test applications, was simply faster.) The men’s chorus, by contrast, was favored by Altiverb, in which the Notre Dame Cathedral IR worked beautifully with a bit of tweaking, lending additional depth and even volume to the recording.

The tie-breaker came down to the professional string quartet recording, in which a beautifully recorded ensemble in a large concert hall had been placed a bit too to the microphones, requiring some additional distance and acoustic sweetening to achieve the desired final edited product. A slightly tweaked QL Spaces “NY String Hall” took the prize in this case, providing the recording an incredible depth and a gorgeous tail. Ultimately we were able to achieve similar results in Altiverb, but QL Spaces got us there much faster and with less hassle.        

Tech-heads and recording engineers will appreciate the options and total versatility that Altiverb has to offer, as it may currently be one of the most robust plugins available on the market for any audio application. Yet one cannot simply relegate QL Spaces to a lower niche, as the quality of its IR presets easily matched that of Altiverb. In the final analysis, audio engineers will certainly want to own both products, while those with more limited budgets (and smaller technical aspirations) will find Spaces a riveting addition that – with careful use – will yield the highest professional results.

It was difficult to grade these products when comparing one to the other. QL Spaces only misses getting an even score with Altiverb due to having fewer options on board. Yet given that one can own Spaces ($249.00) at half the price of that of the most basic version of Altiverb ($595.00), Spaces may be the preferred reverb upgrade for a majority of this column’s readers.

We can conclude that Altiverb remains king of the hill. But Spaces is an impressive new product, which is very nearly on an equal footing with this old standby. Quantum Leap and EastWest has a real gem here, and should make every effort to increase the options available in their product. The ability to add third party IRs might even rocket their product to the top of the reverb heap.

* Note: In the So. Cal. Orchestral Hall IR Menu, composers will find a deeper list of impulses recorded from specific instrument and section sounds, a very welcome addition indeed.


Audio Ease Altiverb: **** (4 out of 4 stars)
EastWest Quantum Leap Spaces:  *** (3 ½ out of 4 stars)

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