What is burn-in and why?

The practice of burn-in originated with the commercialization of electronics about a century ago -- and it makes a difference to nearly all things associated with the audio system. Some things about burn-in are easy to grasp, but they are the exception.

As burn-in relates to sonic fidelity, nearly all solidly burned-in audio equipment and devices (including cables) sound better than the same device when new. Many feel that even loudspeaker cabinets, like musical instruments, need years of play to sound their best. Certainly all audio cable or wire impacted transmitting and receiving systems are influenced by burn-in.


We’re not totally sure. There are so many variables -- and very little conclusive, in-depth scientific research can be correlated meaningfully.

What We Learned

In 2001, Zu began tracking and investigating the effects of signal and power on various cables and loudspeaker systems. During the course of this investigation, we stumbled upon a few tricks and processes that get us pretty excited.

Electric burn-in seems to relate to the stressing of the insulator’s electric behavior (Wave Mechanics or Quantum -- both seem to get you there in this case), standing waves, or is it electron orbital, or is it electron clouds, or sets and metrics? Interplay with van der Waals forces, electric standing waves, and Pauli exclusion effects too; not only between signal, power and dielectric but also the conductor and the conductors electric behavior. Catalyst for electronic change is the propagation of signal and its power component. It looks like it has little to do with the “conductors changing structure” as a few cable marketing companies have hyped. 

Even with a few happened on insights of our own, and the work of many others, we're still not prepared to release any new data or findings. We can only relay that we fully believe in the sonic effect we hear.

How real and how much difference is there?

Significant in most cases. So significant, that we made some heavy investments in exploiting the phenomenon.  

While running extreme soak tests, we found that through long hours of play, there is potential to improve wire, cable, component, and loudspeaker drivers beyond what is possible with a traditional burn-in or break-in procedure.

In 2006 we undertook the challenge of applying some of our accidental discoveries -- along with all the great stuff from the giants of physics -- to production processes and finished products. There were a few accidents along the way -- a burnt rack of power amps, cooked voice coils, and shredded driver cones -- but the time, money, and setbacks were completely worth it. 

The proof of the pudding is in the eating, or in Zu’s case, how satisfied the customer is in the listening.

What Burn-In Means to Zu

Zu’s first big indicator that burn-in was essential to get our stuff sounding its best was when one of the original pair of Zu Druid loudspeakers was shipped to Don Garber of Fi in New York.  He liked 'em but never loved ‘em. A year later, Zu had them collected and went about checking them over. The consensus was that Don should have loved ‘em, and that someone at Zu must have screwed something up, or that there might have been a transformer compatibility issue. 

Everything checked out like new -- and that was the problem. A year of play with very low power had done nothing to break them in. 

It was then that we realized most users are not going to lean on the speakers the way Zu does. After thinking about it for half a second, we realized that our whole concept of how our speakers were going to be broken-in was not possible for the vast majority.

Concert level playback -- concert after concert after concert -- meant we had to get a soak and burn-in system up and running quick. 

On September 31, 2006, Zu committed to running all loudspeakers though our factory burn-in system. This aging/burn-in treating process ensures Zu loudspeakers will sound their very best without the user having to burn them in with specified program material or at high playback levels. A new pair of loudspeakers that have been hit with factory burn-in process will reach peak performance within a very short time -- a week or two in the summer months, two to four weeks in the winter as wide temperature gradients seem to cause delayed burn-in.

The speakers will sound better as time passes, but users really shouldn't sweat it. Just play as you will!

We're excited about our burn-in process. Since adding it as part of the manufacturing process, our 60-day satisfaction guarantee refunds have gone from roughly 6% to less than 2%. The comments from customers went from, “They're good, but a bit restricted sounding,” to, “Man, these things rock!”

No, we’re not kidding, the difference is night and day. That’s how we hear it, and that’s what end users are telling from all over the world.

This difference was confirmed in the first quarter of 2011. During the fourth quarter of 2010, we introduced the Omen series. As a cost cutting measure, we announced that this line would not be getting factory burn-in. This was a mistake and our return rate rose, hitting 8%. Lesson learned.  All Zu loudspeakers now have factory burn-in.

2013 Burn-in Program

Beginning 2013, all Zu loudspeakers receive 600 hours of near soak test level burn-in. This new system and schedule helps to ensure your new Zu speakers will wake up and perform quickly -- assuming that the room and gear are working well together, and you're playing the loudspeakers for roughly four hours a day, at normal daytime listening levels. 

Live sound pressure levels are not necessary -- the burn-in program takes care of this phase for you -- but doing so will shorten the time it takes for your new loudspeakers to relax and open up. This is especially true if the program material has a large, dynamic, full-spectrum power density.

The 2013 burn-in system and schedule is music based and dynamically varied—low levels during production hours, cranked to “11” for the remainder of the day, and non-working weekends.

(And if you're wondering, we are in an industrial park with a liberal 24 hour workday noise ordinance.) 

Burn-in is done in matched pairs to the complete electromechanical systems (drivers, cable harness, connectors, high-pass network). This portion of our manufacturing and forced aging is also an important stage of our quality assurance program. 

The burn-in is completed before final assembly, where guts meet cabinet, and final tests and measures are performed.

Outside Conditions That Affect Fidelity

Shipping, handling, temperature, and prolonged duration of inactivity can cause fidelity disruption of all Zu loudspeakers and cable. 

After Zu products are transported (and especially if they pass through cold temperatures), they take a bit of time to settle in and come to life. This is generally true of dynamic loudspeaker systems, but we have found these factors dramatically influence the sound of ours. 

How much time? 

One to four weeks. One week or so when warm and shipped by truck, and up to four weeks if the transit time is long and the temperatures are very cold.

Why does handling, temperature changes, temperature gradient rates, and duration of inactivity cause fidelity disruption? 

There are many reasons, some known some speculated.

In our loudspeakers, the major electromechanical subsystems seem sensitive to these influences and proportional to the level of success realized in each of our loudspeaker design tenets: 

  • high-efficiency/huge dynamic range
  • wide well behaved bandwidth from a full-range driver weighted on the human voice
  • doing so sans crossover or other filters on that wide-bander

We do what we can to ensure a good first sonic impression and to maximize short and long term music fidelity -- our new 2013 burn-in program is proof. 

If they don’t sound awesome right out of the box, please give them time to loosen and warm up. Go ahead and call us—we're here to help you get great sound. 


Technical, Show AllSean Casey