Are We On the Cusp of a DSP (Digital Signal Processing) Audio Revolution? Part 2

Are We On the Cusp of a DSP (Digital Signal Processing) Audio Revolution? Part 2

,
,

Part 1 here.

From the Netherlands

Photo 2:ย  Dutch & Dutch 8c Active Loudspeaker (photo by the author)

As Dutch & Dutchโ€™s motto on its website says, โ€œItโ€™s not about the best audio. Itโ€™s about the best audioย in your space.โ€ In that spirit, the Rotterdam-based speaker manufacturer builds high-end active speakers, including its three-way 8c speaker, designed to couple acoustically to your listening room via a front and side-firing cardioid midrange and internal DSP.

During a demo of the 8c at this yearโ€™s AXPONA, Dutch & Dutchโ€™s Gabriel Jones explained: โ€œDSP is an integral part of the design of the 8c. It augments the physical design of the speaker. Making it work involves telling the software how far you are from physical boundaries, such as the rear wall. Then REW (Room EQ Wizard) software is used to phase-align the rear-facing woofers to enable near-perfect room response.โ€ The 8c, according to Gabriel, can operate within 4โ€ณ of the rear wall (see photo 1). The REW software sets the speakersโ€™ response without the dips or valleys caused by room interactions. The user can also customize the response to their preference. Initial setup is done with a phone app. A USB microphone is plugged into the speaker, and it is used in conjunction with the REW software to measure the room response and then set the speaker for linear response.

The internal DSP crossover is a three-way design that delivers each range of frequencies to the speakerโ€™s three drivers via their respective internal power amps, two of which output 250 watts, while the third, for bass, outputs 500 watts. The amps are based on Pascal class-D modules, selected, as per Gabriel, for their superior performance. The tweeter crosses over at 1250 Hz, which is low for a tweeter, but it allows the midrange to operate with less beaming, while the bass driver operates below 100 Hz. Time alignment is accomplished through a FIR (Finite Impulse Response) filter and DSP.ย 

โ€œOne of the nice features about the D&D 8c is that it is a platform, not a unique product,โ€ said Gabriel. โ€œFirmware and software can be updated continuously.ย It can accept plug-ins. It can now stream from Roon, Spotify, and other sources. And the speakers cardioid cabinet take care of the sound environment in which they are used.โ€

When I asked Gabriel what he thought of DSPโ€™s audio playbackโ€™s future, he replied, โ€œThe sky is the limit.ย Without DSP, you have a car without a steering wheel. DSP is growing in both the professional and audiophile markets. Equalization and crossovers are accomplished without drawbacks and DSP is also used to help eliminate driver limitations.โ€

From Another Planet

Ron Meyer is the president and CEO of Texas-based Planet Venus Audio. The company offers a proprietary product designed to improve the sound of most recordings by eliminating noise from the recording itself. The product is called โ€œSpectral Coherence Controlโ€, and it works by using DSP to locate noise in the frequency domain, and eliminate it.

I spoke with Ron, who explained that sound quality can be degraded in various parts of the recording and playback process. Sound waves can easily be interfered with during the recording process, such as when two microphones or more are used to pick up the same source.ย The signal becomes distorted because timing of the musical wave may be confounded by the alternate signal(s). This can distort the image and make the stereo effect less palpable.ย 

To curtail this problem, Spectral Coherence Control can be used to eliminate the distortion embedded in the recording, a process that can be done at the source when the recording is mastered or in the listening room by the end-user. Planet Venus Audio, in conjunction with another company, Sonic Studio, developed a new type of DAW (Digital Audio Workstation) plug-in (Patent #10587983), that can alter the soundโ€™s perceived clarity or coherence. The companyโ€™s website, (https://planetvenusaudiotech.com/), offers some sample sound files and a white paper explaining what is meant by coherence in audio and how it affects what we hear.ย 

Using a good pair of headphones, if you listen closely to the sample sound files on the website, itโ€™s not hard to hear the difference this product can make. The track compares the original sound with the corrected sound and also plays the incoherent sound removed by the process. To my ears, the original version sounded good, but the corrected one brought out certain instruments from the mix. For example, the electric guitar in the second sample sounded distinctly clearer than in the original one and was much easier to make out.ย 

This plug-in works on Mac DAWs, but a Windows version is in the works. Room correction, for now, is not in the companyโ€™s plans. Ron suggested that professional users have not yet fully embraced his technology, but that the high-end audio market could view this product as offering a significant benefit since it removes many of the distortions associated with listener fatigue.

Any downside? Ron admitted that itโ€™s possible to overdo it. If you remove too much noise and distortion from a recording, the sound can begin to sound unreal. Itโ€™s like overdoing the contrast or brightness controls on the TV.

The Swiss Army Knife

Parks Audio makes a DSP phono preamp called Puffin that I like to refer to as the Swiss Army Knife of phono preamps because it does so much. But more than that, itโ€™s a Swiss army knife that keeps getting features added to it. When first introduced a few years back, this phono stage had several notable features not normally seen in a phono stage, such as tone controls that can bring a more tube-like character to the sound. But since then, a plethora of features (Iโ€™ve put their names in parentheses) were added, including one to grade records for quality (Grade), eliminate pops and clicks (Magic), adjust cartridge azimuth (Azimuth) and anti-skate (Antiskate), measure turntable speed accuracy (Test), perform room EQ (RoomEQ) and mono record noise reduction (Super Mono), and more! Thatโ€™s the strength of DSP.ย  An easy update of the productโ€™s firmware made all the new features available and improved several of the old ones.

But hereโ€™s a news flash: Parks Audio now has a new product called Waxwing. Itโ€™s similar in function to Puffin, but it incorporates the use of a phone app to control the device settings and allow for easier upgrades to device functions.

I spoke with Shannon Parks, the companyโ€™s founder, and asked what he thought DSP could do and where it was headed. Hereโ€™s our Q&A session:

MH:ย  How does your product use DSP and what are the advantages?

SP: The functions are like spices in a spice cabinet.ย For me, I primarily end up using Super Mono, Magic, Grade, Treble, and Derumble an awful lot. At this point, I couldnโ€™t live without those features. I use Super Mono to get clean mono LP sound, Magic for pop and click attenuation, Grade for grading records, Treble to sometimes bring vocals a bit more forward, and Derumble to lower whoosh noise on stereo LPs. ย 

MH:ย  What are the strengths and weaknesses of DSP?

SP: The strength of DSP is that it really gives the audio designer a hugeโ€”almost limitlessโ€”toolbox to work with versus analogue methods. This same strength is also a weakness, as you can easily overuse DSP to get sound into an aural uncanny valley. Going back to the 1990s, a lot of audio devices started adding fake reverb to everything, but did anyone use it or want it? People hate fake sounding or fake looking things, whether itโ€™s poor generative AI, over-Photoshopped images, or Auto-Tune.ย I think AI, Photoshop, Auto-Tune, etc., can be used skillfully by the artist, but folks using these tools are always tempted to take things to eleven.ย It makes more of a โ€œwowโ€ when doing an A vs. B comparison, but restrained use is key and hard to do in practice.ย Uplift the source material but donโ€™t clobber it.

MH: Where do you see this going in the future?

SP: Dedicated AI chips are coming that will do a host of things. Noise reduction is always a goal, and this goal connects us all the way back to Edison with his first phonograph and his continued attempts to get a better signal-to-noise ratio.ย I watch a lot of YouTube, and Iโ€™m constantly amazed at the unbelievable 4K video yet horrible audio.ย I look forward to AI chips that will correct all kinds of sound flaws in video recordings, such as room echo, high noise floor, unintelligibility, low frequency mike thumps, noise from traffic outside, etc.ย But audio DSP managed by AI will be pervasive and will be amazing in some ways and horrible in others.ย Hopefully, there will be continued experimentation in audio design with future entrepreneurs.ย And AI will be a huge help to the small audio company just getting started in a garage.ย So, Iโ€™m hoping folks will opt for a toolbox loaded with tools and that theyโ€™ll develop the intuition of an expert chef who can season their dish perfectly.ย We really need this innovation and not to just cede things over to boring mega corps.ย I live in the Seattle area and am a Hendrix fan, and I always think to myself: WWJD? What Would Jimi Do? New ideas are wonderful, and they entertain us in exciting ways.ย 

MH: Since youโ€™ve stuck to applying DSP to an analogue source in the form of a phono preamp, can or should DSP be used in pure analogueโ€”tape and recordโ€”reproduction? And how?

SP:ย  As far as tape noise reduction is concerned, there are some techniques that I have used with Audacity in restoring some 50-year-old compact cassettes of my family sharing conversations.ย Some of the techniques in tape noise reduction are extremely useful and I want to research them in more detail.ย For example, in Audacity you can examine a noise floor and develop a specific filter profile for it.ย Iโ€™d like to experiment and learn more about these types of filters in the future, particularly for real-time usage.

The Great Carmike Predicts:

Some would argue that DSP or anything digital might somehow alter the sound in a non-musical manner, producing audible artifacts from timing shifts to digital noise and distortion. As weโ€™ve seen from the cautionary statements by the experts about the overuse of DSP, this is certainly a concern. But we can also overuse the contrast control on our TVs. Some keen-eared listeners may also be able to hear the digital artifacts caused by such things as low sampling rate and incorrect phase response. And there are some problems with DSP that will linger, such as its inherent latency and computational shortcomings. Many such problems may not be audible but itโ€™s fair to assume there will be an ongoing effort to determine which artifacts of DSP may cause audible distortions or noise of various types.

In a recent article in the Loudspeaker Industry Sourcebook, authors Phenix Nunlee and coauthors Ryan Boyle, Matthew Tyler, and David Thibodeau of Analog Devices, comparison-tested a pair of custom loudspeakers using analogue versus DSP crossovers. One remarkable statement made in that article is that top speaker manufacturers tune their crossovers to provide matched responses from the speakers. This is a frequent practice in the industry and is necessary because of variability in the drivers and crossover components. The DSP crossover eliminates this problem by allowing exact matching of the speakers. Itโ€™s a lot easier to do this in software than in hardware. They concluded that the response at the listening position of their test setup was smoother using DSP compared to the analogue crossover and that the benefits of using DSP are โ€œabundant and clearโ€.ย ย 

DSP seems poised to touch every aspect of sound reproduction. If weโ€™re listening to digital, weโ€™re already listening to DSP. Weโ€™ve merged digital sound with specialized computers and software to make many of todayโ€™s playback limitations in audio trivial. Weโ€™ve seen DSP applied to room correction, parametric equalization, crossover filtering, noise reduction, and personal sound preferences, in products from phono preamps to active loudspeakers with powerful class-D amplifiers. Thatโ€™s todayโ€™s picture. What about tomorrowโ€™s?ย 

I donโ€™t have Carnac the Magnificentโ€™s turban, nor the flowing robes of the Cable Guru (itโ€™s actually a Canadians hockey team-inspired hoody I bought at Canadian Tire โ€“ ed.). But input from the experts along with a little research might shed light on the future of DSP.ย This is what I predict:

Within 20 years, DSP in its various forms will be incorporated in nearly all audio products, including the high-end stuff, and be applied in ways even the Great Carmike canโ€™t begin to fathom today. Two-channel stereo may still be the norm for most audiophiles, but DSP will make it better. Immersive audio will be huge. The problems plaguing speakersโ€”distortion, non linearity, sonic differences between the left and right speakersโ€”will be vanquished. Speakers have already nearly reached the pinnacle of what can be achieved in performance with transducers and passive filters in a box, panel, open-baffle, or whatever type of speaker design. Yet, speakers are still nonlinear, unmatched, and with distortion figures high above that of the best electronics. We already have great-sounding DSP-powered speakers. Even digital-specific problems like jitter and quantization noise are becoming a thing of the past now with DSP.

But of all the places DSP may prove the most beneficial, it may be in the car, where there is no listening sweet spot and the noise level from road vibrations and wind can reach 50 to 80 dBs. Thatโ€™s not to mention engine noise, but that will diminish with new engine technologies.ย In the future, DSP-enabled cars will have the ability to alter the audio perspective in the vehicle to put the driver and/or passengers in a place much closer to a sweet spot, whileย active noise cancellation will prevent outside noises from coming inโ€”that is, until it senses the presence of an approaching emergency vehicle with its lights flashing and sirens blaring, at which point your carโ€™s DSP will recognize the danger, quiet the music, and allow the sirens (and maybe even the lights) to clearly come through. DSP can make this happen!

So, is this the end of the road for analogue?ย  Well, technically, it canโ€™t be, since we are analogue beings, not digital computers, so we need analogue signals to hear sound. Many of us are still quite attached to our analogue equipment and tools, although I envision that in 20 years most things analogue will become as passรฉ as the Edison cylinder from the 1890s.ย Digital streaming has taken over the world now. It wonโ€™t go away any time soon.ย The chore of handling physical media will be replaced by a constant stream of hi-res music playback supplemented with the best liner notes one could hope forโ€”with more information than anything that could fit on a 12โ€ณ LP cover. You could become an expert on a musical work, with details about its performance, recording, musicians, history, reviewsโ€”in just one sitting. I donโ€™t think weโ€™ll need to wait long for some major improvements to happen to the sound of audio.ย As stated by Al Clark of Danville Signal, โ€œAs time goes on, the cheapest DSP is going to catch up with the more state-of-the-art.โ€ย That means that excellent sound reproduction is being democratized. Even with limited funds to invest in audio, we will be able to own a superb-sounding system with tons of features.ย This is it, folks. We are on the cusp of an audio revolution in sound quality the likes of which weโ€™ve never seen, thanks to DSP.

2024 PMA Magazine. All rights reserved.


PMA Poll: How much did you spend on your last pair of speakers?

Dear readers,

As you might know, PMA is an independent consumer audio and music magazine that prides itself on doing things differently. For the past three years, weโ€™ve dedicated ourselves to bringing you an authentic reading experience. We steer clear of commercial influences, ensuring that what you hear from us is genuine, unfiltered, and true to our values.

However, independence comes with its challenges. To continue our journey of honest journalism and to maintain the quality of content you love, we find ourselves turning to you, our community, for support. Your contributions, no matter how small, will help us sustain our operations and continue to deliver the content you trust and enjoy. Itโ€™s your support that empowers us to remain independent and keep our ears to the ground, listening and sharing stories that matter, without any external pressures or biases.

Thank you so much for being a part of our journey.

The PMA Team

If you wish to donate, you can do so here.

Search for a Topic

and enjoy exclusive content and early offers

SIGN UP TO OUR NEWSLETTER

Email field is required to subscribe.