Cooper Aspire RF Dimmer makes LEDs buzz?

I’ve been researching z-wave lights and switches for a while, and finally decided to buy some Cooper Aspire RF9540-NAW dimmers. They’re fairly expensive at about $90 each, but they specifically support dimmable LEDs, and instant status. Both features are important to me.

I hooked one up today in a single location control configuration, as per the instruction diagram at

  • Incoming hot black wire to the black wire on the switch

  • red wire out of the switch to the black (load) wire of the lights

  • white neutral wire from the switch to a wire nut, with both the white wire from the light and the white neutral back to the breaker box

  • green ground out of the switch to the copper ground in the box

The six bulbs on the circuit are CREE 60-watt-equivalent soft white dimmable LEDs from Home Depot. Cree bulbs are on Cooper’s list of compatible dimmable LED bulbs at

All six bulbs buzz (loudly) at every possible light level. I thought these dimmers would not have this issue, particularly when I chose a a model that requires a neutral.

I thought it might possibly be a defective dimmer, so I tried another. Same exact behavior.

Any ideas?

I don’t have Cooper dimmers but I have the same Cree bulbs hooked up to a Leviton Vizia RF+ VRI-06 incandescent dimmer and I do hear them buzzing at all light levels. I’ve got three bulbs in a light. Seems like I’ve read other posts with this as well. I agree it’s not ideal.

@JamesDVB - If you have multiple bulbs buzzing, especially loudly, I would contact Cooper and see what they say about it.

I have very good hearing and am particularly sensitive to high-pitched buzzing or squealing. I am able to hear buzzing in a large amount of CFLs, that are not on dimmers. I’m even able to hear the buzz/squeal of the video chip in many PCs, while most people can’t hear it.

I’ve never used the Cooper switch, they’re just too expensive for my needs, buy I use the same bulbs with Linear and Evolve dimmers(no Instant Status). They work well and there is no buzzing. Out of dozens, I have had the occasional bulb buzz a little bit. I would describe the sound as a quiet hiss when dimmed. The room needs to be absolutely silent to hear it. Having spent so much money for the bulbs I will not tolerate any defect and these bulbs should not buzz. The couple noise making bulbs that I have had have been returned to HD for silent replacements.

I’ll also note that these bulbs are susceptible to sags and surges at low dim levels. Switching loads on and off such as bathroom fans on the same breaker, can cause a dimmed light(s) to do a near imperceptible flicker, regardless of the dimmer being Z-Wave or standard.

I decided to try some Philips LED bulbs to see if they had the same problem, so I bought one of these:

Same problem. Buzzes about the same amount, maybe a little less than the Cree bulbs, but still absolutely a no-go.

Also tried both the Cree and Philips on a different circuit and different fixture. Same issue. Neither buzz at all on an on/off Cooper Aspire RF switch, but I really wanted to go the dimmable route…

@Z-Waver, what’s the ramp rate like on your Linear dimmers? In reviewing them as a possible alternative, I notice the ramp rate is not programmable on those.

On the Cooper Aspire dimmers, it is adjustable, which is good, because the default ramp rate is annoyingly slow. When you turn on the light, they fade on over the course of about 5 seconds, but it’s long enough to be annoying when you walk into a dark room and have to wait for light. I’d prefer something quick, or instant-on.

This is a tough question to answer since I don’t have an accurate way of measuring it and I’m not sure I can describe it clearly. When switching on, with a 100% last use preset, the Linears reach 100% in about 3 seconds or less. But it seems much quicker than that beacuse the starting dim level is pretty high and even more so when you are using LEDs because a low dimmer setting is still a pretty high bulb brightness. You can see this in my dimmer power savings tests post. There a Cree bulb dimmed to 20% appeared to have a lux output ~40% of the bulbs rated output.

Using Cree bulbs and the Linear dimmer, in the previously described Off to 100% turn on ramp up, the bulbs seem to start immediately at ~70% brightness and then continue to ramp up for another ~2 seconds to 100%. The turn off ramp down takes the same time, ~3 seconds. But the ramp down appears slower that the ramp up because the bulbs fade all the way off rather than a sudden cut off, the inverse of the start up.

You won’t be annoyed, waiting for light. The Linear dimmers produce ample brightness immediately. But, they do not support Instant Status.