D-fend™ Loudspeaker Protection

D-fend™ is the industry’s first all-digital, programmable loudspeaker protection and attenuation circuit designed to solve the age-old problems associated with protecting loudspeakers from excessive power conditions. D-fend™ has eliminated the headaches for speaker engineers – no more hassling with polyswitches, blown lamp filaments, lossy resistors, or slow relays.

Incorporating such features as digital signal processing with on-board digital filtering, customizable microprocessor and MOSFET construction, the D-fend™ protection circuit enables a designer to use this technology prior to passive filtration and allows different sensitivity settings in specific frequency bands, such as woofer over-excursion bands or high frequency peak damage regions.

A patented technology of Evenstar™, D-fend™ allows maximum driver performance while ensuring damage-free operation. Continuing in the successful evolution of their electronic technology, Evenstar™ has pushed the limits of modern technology and achieved unparalleled performance in speaker protection with the implementation of the unique features listed below.

Digital Signal Processing

With on-board digital filtering, D-fend™ provides multiple frequency dependent thresholds and independent attack/release timing parameters. This enables the designer to use D-fend™ technology prior to passive filtration, and allows increased sensitivity in specific frequency bands such as woofer over-excursion bands or high frequency peak damage regions.

Digital Attenuation
Significantly reduced heat, no bulbs, no light output.

Fully Programmable
On-board microprocessor allows user customizable attack, release, and threshold to maximize loudspeaker performance and minimize SKUs.

High Power
Capable of protecting high power woofers and sub-woofers from over power conditions as well as mechanical damage thresholds, an achievement unseen within the audio industry.


MOSFET construction allows easy device voltage and current selection, allowing operation with woofers, tweeters, or midrange devices. Under certain circumstances, D-fend™ may also be utilized as a continuous attenuator.


Monitors both voltage and current under algorithmic control, allowing a diversity of customizable implementations such as adaptive thresholds and attack times, temperature dependent protection, and real-time impedance and power delivery measurements.

No Aux Power
Operates from a standard speaker-level signal, does not require auxiliary power.

Affordable solution allowing various implementations for cost-sensitive applications.

Attenuation slewing algorithms provide lamp-like musicality without the nuisance of light and flammability concerns. Think of it as a high-power, speaker-level compressor/limiter allowing the designer to guarantee unmatched levels of protection for their unpowered loudspeaker solutions.

The following plots illustrate how D-fend™ can be programmed to match a loudspeaker’s power handling characteristics, including both response time and required attenuation levels:

D-fend™ loudspeaker protection is ideal tor:

Word of mouth can be an installer’s best triend or worst enemy. D-fend™ will not only protect your carefully installed equipment but also gives you peace of mind knowing your reputation is protected as weil.

Rental Companies
By using D-fend™ you can rent out your speakers and know that you’lI get them back in the same condition they left. What comes in on Monday can go back out the door again without a visit to your repair shop.

OEM Manufacturers*
What can be better than offering a bulletproof loudspeaker system? With D-fend you can ofter your customers something they’ve never seen before: a passive speaker that can’t be destroyed, no matter how hard you punish it.

Own some passive speakers? Chances are you’ve come closer than you think to blowing a driver. There’s nothing worse than stopping a show in progress because you just lost your subwoofer. Why take the chance?

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