Subwoofer volume randomly goes berserk. Sub or receiver problem?

[Mithrandir]

I have the following situation - sometimes while i'm watching movies subwoofer volume goes out of control, and volume control on the subwoofer does nothing (volume level stays the same). Sometimes it helps if I switch mode on subwoofer or plug/unplug it.

Reciever is Marantz SR5004 and sub is Monitor Audio R370HD, connected on LFE out on receiver.

I accidentaly discovered the following: if I touch the back metal plate on sub with one hand (while power cable is plugged in) and touch the tip of RCA cable with other hand (plugged in receiver, unplugged from sub), I feel some static/current on my hand, even when receiver is unplugged from power.

I have tried plugging in subwoofer in 2 different sockets, behaviour is exact in both cases.

Anybody has the idea what might be the problem?

 

[shadyJ]

sounds like a short somewhere in the subwoofer amplifier. You really need to junk the sub, that could turn into a fire hazard. You might want to have your electrical outlets checked for safety issues as well.

 

[Mithrandir]

Is it worth replacing the amp in the sub, or I'm better buying a new sub? MA R370HD wasn't that cheap when I bought it, I would like to avoid additional expenses If I can

 

[shadyJ]

There are better subs for the same price in the USA and Europe. If you aren't in those areas, I don't know. It doesn't strike me as a great subwoofer.

 

[Mithrandir]

I'm in Europe (Croatia). It's not primary, but looks of R370HD are great, and the rest of the lineup is also Monitor Audio Radius HD.

Can you recommend some subwoofers if amp replacement is not worth it, my room size is about 3.5x6 meters or 11.5'x20' in feets. I'm sitting in front of 3.5' wall.

I have this set: Monitor Audio R270HD10
http://www.monitoraudio.co.uk/products/past-products/radius-hd/r270hd10

Fronts: Monitor Audio Radius R270HD
Center: Monitor Audio Radius R225HD
Surround: Monitor Audio Radius R90HD
Sub: Monitor Audio Radius R370HD

I had to go for slim fronts because of room and furniture, larger fronts wouldn't fit.

 

[tyhjaarpa]

I'm in Europe (Croatia). It's not primary, but looks of R370HD are great, and the rest of the lineup is also Monitor Audio Radius HD.

Can you recommend some subwoofers if amp replacement is not worth it, my room size is about 3.5x6 meters or 11.5'x20' in feets. I'm sitting in front of 3.5' wall.

I have this set: Monitor Audio R270HD10
http://www.monitoraudio.co.uk/products/past-products/radius-hd/r270hd10

Fronts: Monitor Audio Radius R270HD
Center: Monitor Audio Radius R225HD
Surround: Monitor Audio Radius R90HD
Sub: Monitor Audio Radius R370HD

I had to go for slim fronts because of room and furniture, larger fronts wouldn't fit.

What would be the budget for a sub? As it is really hard to recommend a sub without knowing that. But for european market BK offers best value. http://www.bkelec.com/HiFi/Sub_Woofers.htm I personally have two XXLS400-DF and I'm really happy with them.

 

[KEW]

That looks like it might be a lifestyle system (4" woofers in the mains). If you replace it, you need to make sure you get a sub that can cross-over at the right frequency.

Certainly, it would do no harm to find out cost of replacement amp from monitor audio.

 

[KEW]

You also might want to open it up and inspect the amp module for any signs/odors from overheating/short.

 

[tyhjaarpa]

That looks like it might be a lifestyle system (4" woofers in the mains). If you replace it, you need to make sure you get a sub that can cross-over at the right frequency.

Certainly, it would do no harm to find out cost of replacement amp from monitor audio.

Those towers frequency response is rated at 48 Hz - 35 KHz, if those are even close to real numbers then I wouldn't see a problem with crossing them with any sub. How ever if the actual output is over 100 Hz for low end then this must be taken in consideration.

 

[Mithrandir]

Audyssey MultEq did the crossover on 80Hz.

Because of the volume went berserk, some small part was loose inside sub box and was making noise on some frequencies.
That's why I took it to official Monitor Audio distributor for Croatia, but they couldn't find the problem and I'm quite sure they didn't even inspect the volume issue.

I opened the box home and found small plastic cap stuck in the edge of the box and took it out, so didn't have the rambling issue anymore, but volume issue persisted That's why I'm not confident taking it to official MA service in Croatia.

I'll inspect the amp and post the results. Thanks to all for the advices.

 

[lovinthehd]

That's a shame they can't support their product better than that. If the sub amp cannot be repaired and the driver hasn't been damaged, an external amp could be utilized fairly easily (but may not be worth the expense vs simply buying a better sub).

 

[Scott Y.]

People use the term "short circuit" freely. It could be an open-circuit or cold solder joint. Possibly a potentiometer with a bad connection. Probably not that hard to find.