Energy ES-12 Subwoofer Whining Noise after Power Down

[Defcon99]

I have an Energy ES-12 powered subwoofer. 20 to 30 seconds after turning power off after playing, a sound is emitted (I believe through the speaker) that last 3 to 4 seconds. Sound is similar to a mid-frequency whine from high to low, then stops and all is quiet. The subwoofer performs very well when playing music and produces strong, low bass. I purchased new approximately 15-20 years old. It has been a great sub. I’m hoping someone might be familiar with this issue and point me in the right direction as to what the problem component could be.


Thanks in advance for your help.

 

[evsentry3]

Well, clearly you're not familiar with speaker technology. Where do you think all that sound it puts out comes from? That's the turbines winding down! Dah!!!

JK. JK. Probably electrolytic capacitors values drifting due to age. Might keeping making noise or might drift off far enough from intended value to cause a serious problem too.

Your option to have it serviced or cross your fingers and hope it doesn't let the magic smoke out. At which time if repair is still an option, the price just went up.

Electrolytics are regarded as having a life of around 7-10 years, so if that's what it is, you've done well. Sub amp duty is really pretty brutal on them.

EV3

 

[Defcon99]

Thank you EV3. It is an odd/funny sound. If one were inclined to attempt a repair before more serious problems occur, do you have any recommendations on where to start? My first guess would be with the power supply caps? I could pull the plate and carefully study the board for any visible cap issues. However, If nothing visibly wrong, not really sure which caps to focus on. If I knew which one(s) were failing, I could replace them myself. It has been a great sub that sounds great with music. Subs are so relatively cheap, not really cost effective to pay someone to repair. I was hoping to repair myself if possible. Thanks again.

 

[evsentry3]

First thing to ask yourself is if anything else could be the cause of the sound. Are you shutting off anything else upstream and it's slowly discharging before the subs plate amp is fully off?

While PS caps should generally be changed by that kind of age, your sonic description makes me think of uneven drop in the plus and minus rails to an op amp. Often there are small value caps there, like 1-3ufd kind of values. If they age in an uneven way, then at discharge the voltage rails go down at a different rate and can produce some output resulting in funny sounds.

EV3

 

[Defcon99]

Thanks EV3. Using master switch on a power strip, so everything turns off/on at same time. I have also tried different amp/same result. The sub has a delay that shuts power 15 seconds or so after signal loss. I’m pretty certain it’s in the sub. Are you referring to an op amp on the sub board? If so, I will study the small caps around that area. I tried to attach a sound recording of the noise, but the site would not accept. Sound is definitely coming out of speaker. If the darn sub didn’t sound so good, I would just let it fail and move on. Like you said, I’ve done well with it. I just don’t want to throw it out if it can be saved. When I can, I will inspect the boards for any obvious signs (bulging, leaking caps, burn marks, etc,) Otherwise, I believe capacitors have to be removed to be tested, and would need a special measuring device, which I don’t have. Unfortunately, my troubleshooting skills are limited due to experience/tools. Do you think a transistor could also be a suspect? I really appreciate your help. Thanks again.

 

[evsentry3]

Turning on and off all at the same time could be an illusion. How long something takes to discharge is more why it's generally recommended to turn on and off in a certain reversing order. But all that aside, the noise is likely from the plus and minus rail to IC's going down at a different time. Some pieces just seem to do that. But if you are pushing 20 years, then you are way past the point that electrolytics should be replaced routinely before drying out to the point of failure. FWIW, the little ones seem in my experience to go sooner than the bigger ones and that's what the symptoms sound as if they are pointing towards.

If you aren't sure if the noise is from the sub, then you need to put a close ear to the driver as it powers down to be more sure. But still the age you've mentioned on a plate amp still says you've more than gotten you're money's worth and TLC is overdue if it's to live on.

By the time you've removed a cap to check it, and it's pushed two decades of life, it's a mistake to not replace it!

Electrolytic capacitors are about the only thing that age. Enough so that starting with them will be where a bench tech will go.

EV3

 

[Defcon99]

Thank you EV3. Sound is confirmed to be from the sub speaker as the sub amp power indicator light slowly fades to black (about 20 seconds after power is turned off). Overall, the sub still sounds/performs great. I’ve got it on the “to do” list. I will focus on replacing the smaller caps on the power board as you suggested. Thank you again for your help.