TwinDamp™: Improving the Damping Capacity of Manganese-Copper

While designing the Diamond Insert for our Carbide Base footer we sought to utilize a high-damping metal alloy to improve isolation performance. Through research and testing we developed TwinDamp™ – a temperature treated manganese-copper twin crystal metal alloy with exceptional damping properties from 0.01 Hz to 10 MHz .

When manganese-copper alloys are subjected to vibrations, the strain caused by the movement of martensite twins or by the mutual movement between the twin boundaries and martensitic phase boundaries relaxes the stress and dissipates the vibration energy[1]. In other words, small movements between boundaries within the material allow it to effectively dissipate vibrations through a conversion into heat.

Manganese-copper alloys are among the highest damping metal alloys in existence having a damping capacity over 10 times greater than copper[2]. While the damping capacity of these alloys is much less than the elastomers utilized in our ViscoRing™, they have the distinct benefit that as a rigid metal they better maintain their form under load.

Incorporating TwinDamp™ Into the Diamond Insert

The rigidity of TwinDamp™ allowed us to incorporate it in areas of the Diamond Insert where an elastomer would not be sufficiently rigid.

Three pads made of TwinDamp™ were incorporated above the diamond coated ceramic bearing races utilized inside the isolator. The pads were arranged such that they are in series with the vibration transmission path through the device. In other words, vibrations must pass through the pads in order to pass from one side of the footer to the other side. This configuration further improves the overall damping performance of the footer.

The top center threaded hole on the jam bolt was also replaced with an insert made of TwinDamp™. This was to provide a highly damped interface for the tip of a spike to contact if the footers are placed directly under speakers with floor spikes. The insert also provides additional damping if the footers are mounted using the supplied bolts.

TwinDamp™ spikes are optionally available to improve damping of vibrations in and out of the bottom of the footer when three spikes are pointed downward. A single spike can also be used to provide a highly damped interface to the underside of equipment when pointed upward from the top center of the footer.

TwinDamp™ Alloy

Improving Manganese-Copper with Temperature Treatments

It is known that manganese-copper alloys are sensitive to temperature treatments. Sustained exposure to high temperatures also known metal aging can initially improve the damping and strength properties of these alloys. This is due to the enhancement of manganese-rich regions within the material. Over aging can begin to compromise damping capacity however, so balanced treatment temperature and duration is needed for optimal results[3].

A gradual exposure to cryogenic temperatures can also enhance the crystalline structure within metals. This cryogenic tempering process can impart desirable sonic improvements to manganese-copper alloys.

Through experimentation we developed an effective temperature treatment process for the manganese-copper alloy that we use. Our distinct process involves multiple stages of both hot and cold treatments. The treatments are performed over a two day period to improve the damping and sonic performance of this alloy.

1100° C Furnace

Cryogenic Freezer

Measuring Vibration Attenuation

Comparing TwinDamp™, Manganese-Copper, and Stainless Steel

To quantify the vibration damping performance of TwinDamp™ we conducted an experiment. Three sets of three spikes made of stainless steel, manganese-copper, and TwinDamp™ were separately threaded directly into a steel plate. A 3.6 kg (8 lbs.) weight was placed on top the plate to simulate the weight of equipment. The plate was then placed with the three spikes pointed downward on top of a sealed 18 inch subwoofer. Accelerometer sensors were attached to the plate. A log swept sine signal from 15 Hz to 200 Hz was then played through the subwoofer to measure the attenuation provided by each set of spikes.

Stainless Steel measurements are shown in red, manganese-copper in green, and TwinDamp™ in blue.

Vibration Amplitude for All Spikes

Stainless Steel Waterfall

Manganese-Copper Waterfall

TwinDamp™ Waterfall

Conclusion

The manganese-copper spikes provided a subtle but measurable improvement in vibration attenuation compared to the stainless steel spikes. The TwinDamp™ spikes provided even more attenuation than the manganese-copper validating the effectiveness of our temperature treatment process. The improvements were most significant around the subwoofer cabinet resonance at 80 Hz. Both the manganese-copper and TwinDamp™ also showed increased damping capacity as evidenced by the smoothing of the vibration amplitude traces and faster vibration decay in the waterfall graphs.

References

[1] Lu F-S, Wu B, Zhang J-F, Li P and Zhao D-L 2016 Microstructure and damping properties of MnCuNiFeCe alloy Rare Met. 35 615–9

[2] Zhang, J., Perez, R. J., and Lavernia, E. J., “Documentation of damping capacity of metallic, ceramic and metal-matrix composite materials”, Journal of Materials Science, vol. 28, no. 9, pp. 2395–2404, 1993. doi:10.1007/BF01151671

[3] Ke, T. S., Wang, L. T., & Yi, H. C. (1987). Internal friction in manganese-copper and manganese-copper-aluminium alloys. Le Journal de Physique Colloques, 48(C8), C8-559.