Speakers randomly not playing

[TLS Guy]

The 3808 is one of the more powerful receivers. Tested into 2ch at 187 wpc at 8 ohm (.1%thd), into 5ch at 119 wpc at 8 ohm (.1%), into 7ch at 113 wpc at 8 ohm (.1%)....

I had a hard time finding any reliable specs. Denon have minimal on their site.
Eppie has given the correct advice to sort this out. I think this is one of the strangest faults we have ever had reported. The only connection I can think of between the cone moving and speakers, is if some circuit is getting woken up by the back EMF created by moving the cones. It could feed back to the PA input first stage via negative feedback. The specs you quote show enough power to blow the speakers. Since he uses 5 channel stereo it is highly plausible to blow up all the speakers.

I know one thing, unless the speaker wiring is a mess, he has either dud speakers or a dud receiver.

 

[lovinthehd]

I had a hard time finding any reliable specs. Denon have minimal on their site.
Eppie has given the correct advice to sort this out. I think this is one of the strangest faults we have ever had reported. The only connection I can think of between the cone moving and speakers, is if some circuit is getting woken up by the back EMF created by moving the cones. It could feed back to the PA input first stage via negative feedback. The specs you quote show enough power to blow the speakers. Since he uses 5 channel stereo it is highly plausible to blow up all the speakers.

I know one thing, unless the speaker wiring is a mess, he has either dud speakers or a dud receiver.

It's an older product so doubt there's much on Denon's website but maybe the manual. The specs I quoted are from @PENG's spreadsheet he made from various bench tests of various avrs.

@homeaudionoob curious, if you push on the cone of one speaker it affects more than just that one speaker at the same time?

 

[PENG]

I can bring it back (wake up the channel) by pushing the cone in, carefully of course.

Could you do that consistently, that is every time this happens?

If not, it could be just coincident.

What was your typical volume setting when this happened? If it was no where near -15 or so then it would have nothing to do with using 5CH Stereo. In many (but not all obviously) cases 5CH or even 7CH stereo would not stress the amp unduly, because when more channels are playing at the same level one would naturally turn the volume down, say by at least 3 dB, likely more. For every 3 dB lower in volume the amp's total power output would drop by half. If the issue is in the digital domain especially if happens not in direct/pure direct mode then a factory reset may help. Keep in mind after the reset your biamp setting would be cleared.

Have you try using analog input and direct mode to see if the same issue is still there? If it is then at least you know the issue is within the analog signal path, and do more troubleshooting accordingly. The Denon AVR-3808 is quite powerful, probably more so than most 100 W integrated amps at the below $1,500 range, under two channel driven conditions. With 5 channel driven continuously, it should still not be a problem as explained earlier depending on your volume setting, assuming the level trims are at near 0.

 

[highfigh]

This happens randomly across all speakers in the setup. The towers are barely 2 years old. Are you suggesting all of them are bad?

Are you saying that pushing on one cone brings all of them back or that if any stop working, each can be brought back separately?

I agree- that sounds like an amplifier problem. Have you verified that the wiring to the speakers is correct and that the negative wires aren't crossed from one channel to another? I know that many consumer amplifiers use a common ground scheme, but there may be a reason this is happening, especially if you're bi-amping. Don't do that.

Just out of curiosity and because I can't see the speaker terminals, you did remove the jumpers on the speakers, right?

 

[PENG]

Are you saying that pushing on one cone brings all of them back or that if any stop working, each can be brought back separately?

I agree- that sounds like an amplifier problem. Have you verified that the wiring to the speakers is correct and that the negative wires aren't crossed from one channel to another? I know that many consumer amplifiers use a common ground scheme, but there may be a reason this is happening, especially if you're bi-amping. Don't do that.

Just out of curiosity and because I can't see the speaker terminals, you did remove the jumpers on the speakers, right?

Good point that no one mentioned so far, but if if the unit had shutdown on short circuit, overcurrent, high dc offset etc., the OP will know because the unit would shutdown with flashing light presumably.

So I think it may be one or more bad relay/contacts on the volume control IC or something to do with the DSP or other parts of the digital section, hence I suggested he should try analog input/direct mode and see if it can be narrowed down a little.

 

[highfigh]

Good point that no one mentioned so far, but if if the unit had shutdown on short circuit, overcurrent, high dc offset etc., the OP will know because the unit would shutdown with flashing light presumably.

So I think it may be one or more bad relay/contacts on the volume control IC or something to do with the DSP or other parts of the digital section, hence I suggested he should try analog input/direct mode and see if it can be narrowed down a little.

The VC on the face would control a multi-channel VCA (Voltage Controlled Amplifier), which isn't very close to the output WRT the circuitry- some component would need to fail (like a cap or semiconductor) in order for a problem at the speaker terminals to affect the VC. The processor would obviously handle all in/out, DSP, channel assignments, etc but something is triggering protection for audio out/breaking the latching connection for the relays and it needs to be investigated. From at least 50 years of past experience, I can say that hitting the top or sides of the AVR might show that it's a bad connection (we called it 'percussive diagnostics' at the stereo store). Not very hard, just give it a decent rap and see if it comes back- these probably undergo harder impacts during shipping, especially if UPS, USPS and FedEx handle them.

These only do a full protect if voltage is present somewhere it shouldn't be, over temperature and component failure- not aware that it would go dark from speaker protection because it's easy enough to shut off the connection without affecting the rest of the unit.

 

[homeaudionoob]

This owner ran into what sounds like the same issue:

Denon 3808 and audio channels falling out

I have a Denon 3808 that has been plagued by audio channels (speakers) falling out once in a while. When they do fall out it has always helped clicking the "mute" button, and then unmuting again. The sound always returns (until it decides to fall out again). The first time this happened it was...

www.avforums.com

As stated in my Initial post, turning the unit off and on would occasionally bring the channel back "online", as well but very light tapping the cone is the quickest way.

I don't believe the speakers are bad. That would mean all 5 are. This also didn't happen with the 588 this AVR replaced.

Time for a new receiver. Oh well.

 

[lovinthehd]

Well if speakers can "jump start" an amp like that by pushing on the cone, that's the first time I've heard of that.....but on my 3808's issue with the left channel, I didn't do the reset yet but went thru the speaker connections (disconnecting and reconnecting) at all speakers and avr and the problem hasn't returned (yet).

 

[TLS Guy]

This owner ran into what sounds like the same issue:

Denon 3808 and audio channels falling out

I have a Denon 3808 that has been plagued by audio channels (speakers) falling out once in a while. When they do fall out it has always helped clicking the "mute" button, and then unmuting again. The sound always returns (until it decides to fall out again). The first time this happened it was...

www.avforums.com

As stated in my Initial post, turning the unit off and on would occasionally bring the channel back "online", as well but very light tapping the cone is the quickest way.

I don't believe the speakers are bad. That would mean all 5 are. This also didn't happen with the 588 this AVR replaced.

Time for a new receiver. Oh well.

As I think about it, that makes sense. So what is happening when you move the cone, it is generating enough back EMF voltage to remake the relay contact.

Of course Denon do not make the relays, but they have been shopping in the cheapest markets. There is a lot of current going through those speaker relays, and they are a potential source of trouble, as you have found out.

The real solution is to use solid state MOSFET relays, that have no moving parts, and are far more reliable than mechanical relays.

These receivers are at the heart of people's systems. Now the technology is becoming mature, quality needs to improve. Now time to think in 20 to 30 year lifespans and not this five year or so, nonsense. It is possible, as car electronics is designed not to fail and it very rarely does, despite a harsh environment.

I can tell you that paying more up front for a longer lifespan, saves dollars, and lots of them. The main reason, I have such a nice system, is that I choose my gear very carefully, and seldom buy new equipment. Pretty much all my purchases in the last 15 years or so have been buying Pre/Pros and TVs. This has been driven by obsolescence. Although I still have, and use all my five flat screens except for two, which were bought in 2006. I still have all my pre/pros except the first one. Three are in use, and one is stored for a quick get out of trouble should the need arise.

 

[Eppie]

Yeah, I was thinking the same thing, that pushing the cones was inducing voltage into the coils and triggering something in the amp. That's a new one for me too. On the bright side it's probably better that the problem is in the AVR but sucks that it's not likely something that could be easily repaired.

 

[homeaudionoob]

The saga continues...

After removing the biamping setup of my fronts and resetting the receiver ahead of an attempted firmware update (that failed, not able to connect to Denon servers even following all recommended steps), I had two more startups with 4 of my 5 speakers not playing.

Then, magically, all of a sudden this problem stopped occurring and hasn't returned in more than 10 subsequent avr startups.

BUT, before anyone jumps to biamping or the reset as the culprit / fix: I realize now that this very problem actually first occurred the first time I hooked the unit up after purchasing and resetting it... I went through Audyssey and countless times, one or more speakers, especially the side surrounds wouldn't emit a tone during the measurement cycle. At that time, the receiver had been reset and the fronts weren't biamped.

So I'm going to keep monitoring this, of course, but if the problem doesn't return will be happy to keep this unit for a while.

To me, the 3808-CI sounds very good and apparently has an awesome Amp section / PSU just based on some comparative power measurements:

Old receivers are beasts.

www.avsforum.com

Re the comments about my 5CH Stereo setup. I cross over to my sub at 80hz, listen at very moderate volumes and the Klipschs are easy to drive. This should be pretty easy on the amps. I've played 5CH stereo on other Denon AVRs and different speakers for years w/o a problem, just not very loud.

There are very specific reasons I play music this way. My room is very long with a high vaulted ceiling and the way I have the speakers setup and calibrated relative to the MLP creates a very enveloping sound stage where the sides almost sound like front wides. I don't obsess over instrument placement in the stereo field and absolutely prefer this to 2 or 2.1 listening in this specific room. For the future, I'm considering a separate setup in a different room, focused on music listening with a dac, stereo amp and different speakers but until then, this is what I have room for.

Lastly, tapping the cones would only bring that specific speaker back.

Thanks for everyone chiming in here, great forum / group.