Originally Posted by Ohhhtaco
Cross posted in the Definitive Technology Owners Thread and the Subwoofers forum... New to AV, Having issues with sub/amp and need guidance troubleshooting, preparing for appropriate repair, etc.
I have a set of Definitive Technology BP7004 Bipolar SuperTowers for my front left and front right speakers. These speakers each have a standard high-frequency speaker component but also feature a powered sub / LFE. The speaker component of these towers is functioning fine but one of the subs is misbehaving.
These are relatively old but in appearance are in great shape, inherited from a relative who passed away.
One of the pair emits low frequency sub sounds whenever the powered amp is plugged into an outlet (have tried multiple outlets around the house), without any LFE input attached to the tower. The sound is constant, though not consistent in intensity as it fluctuates in how loud it is. Adjusting the sub volume knob does not seem to affect this behavior. Would best compare the sound to when a mic is placed in a windy environment. The sound is quite loud and disruptive and isn't something that could be tolerated or loved with. When not plugged into an outlet, no sub sound, and HFE speaker functionality works without issue.
From the research I've done it sounds like an issue with the powered amp driving the sub--potentially capacitors needing replacement.
1. What steps can I take to further troubleshoot the powered amp/sub? Is this the sort of thing that an electronics/AV store is capable of diagnosing/repairing, and is this sort of repair typically cost effective or recommended?
2. If I don't plug in the tower to an outlet, am I "missing" anything from the HFE? Would the powered amp/sub only trigger with LFE input hooked up or would the HFE speaker input utilize the amp and sub on its own?
While I can't solve all of our problems I can offer you a few bits of advice. In my secondary theater I have a CS-8080HD center channel (i.e., the previous top-of-the-line center channel), a pair of Studio Monitor 55's in the front (which will eventually be replaced with a pair of Studio Monitor 65's), a pair of Surround 8080's in the rear, and and SVS subwoofer. If you are unaware the center channel has a powered 5"x10" racetrack style "subwoofer" with two passive 5"x10" "subwoofers" on the top. When I received the speaker direct from DefTech the amp was not working. They were a pleasure to deal with and sent me a new amp for free. Replacing it was very easy - I simply removed a few screws, pulled out the "board" which houses the components, removed a wire or two, connected them to the new board, slid it in, and screwed it back in. The repair probably took me no longer than three minutes. So, if the amp is indeed shot, I would take care of it yourself.
If you choose not to plug in your towers you will be leveraging your receiver or amp's power to drive the tweeters, mid-range, and low-end drivers. This is can be a lot to ask of a receiver or amp. I would recommend trying them unplugged just to see if your issue persists, understanding that this is not a long-term solution. It sounds to me like your amp(s) is/are shot. Give DefTech a call and see what they say.
Please post an update - I'm curious to see how this shakes out.