Speakers randomly not playing

[homeaudionoob]

Hi,

I'm currently using a Denon AVR-3808CI for music and home theater duty in an open-in-the-back & fan cooled cabinet with the following speakers:

Bi-amped Klipsch RP280Fs for fronts, RP-150Ms for satellites, a single SVS SB-12 sub for bass, crossed at 80Hz.

I'm playing music in 5CH Stereo mode and Movies in one of the surround modes, all at very moderate volumes.

My problem:

Occasionally and unit temperature independent, some of the channels / speakers aren't playing. The fronts will come back if I turn the AVR off and on or switch to a movie/TV source but the satellite(s) I have to disconnect and reconnect one of the speaker wires. It can take 10 or more attempts including shutting off the AVR completely to get the signal through those speakers back. The wire to pole connections are solid, the impacted speaker pattern isn't really random and sometimes the sub isn't playing either, which is hooked up via RCA.

Is there a problem with my amps or internal connections on this unit?

Thanks!

 

[lovinthehd]

Well I'd get rid of the silly bi-amp setup first I wouldn't use the 5ch stereo thing either. Have you tried a soft reset (unplugging the avr for a bit) or a full factory/microprocessor reset?

 

[TLS Guy]

As above. Passive bi-amping is a useless endeavor and a cause of problems. And yes, 5 channel stereo is something that not only causes very poor sound, but really stresses the receiver unnecessarily. So stop doing both of those things and see if that corrects it. If not then do a hard reset on the receiver. If that does not correct it then your receiver needs repair/replacement. Your set up as you describe it may well have stressed your receiver and shortened its lifespan.

 

[Eppie]

@homeaudionoob I think a little more information is in order. First off, your main speakers have a very high sensitivity rating of 98dB, so they do not take a lot of power to drive them. The AVR has 130W/ch so plenty of power for those speakers. I don't see those speakers stressing your amp unless you're playing at concert level volumes on a regular basis. Bi-amping is not necessary as mentioned above, especially since you have an AVR with all amps integrated and running off of the same power supply. You gain little if anything with bi-amping using that AVR. Having said that, bi-amping does change the speaker impedance presented to the amps. The speaker is rated at 8 ohms in normal configuration, but when you remove the jumpers the impedance can be lowered on one set of terminals, which could potentially stress the amps. Unfortunately KEF does not list the impedance with the jumpers removed, so I can't say for certain.

5 channel music is a personal preference. Use whatever surround modes you enjoy, whether it's 2 channel or 5 channel for music. It may not appeal to others but there's no right or wrong, just differences in opinion.

What you describe sounds like a problem with the internal circuitry of the AVR, especially the way the surrounds and sub are behaving. Full factory reset may help, but I suspect that there is an internal problem with the Denon.

 

[homeaudionoob]

Thanks. This problem predates me bi-amping my fronts using the rear surround channels. I'm not going to get into the weeds of why I'm testing bi-amping or why I prefer 5CH St in my specific room.

As the mute channel(s) can return to playing even without fiddling with the wires, I think you may be right that there's an internal issue with the AVR. I wonder if anyone else has run into this issue and figured out if it can be fixed rather than replacing the whole unit?

The 3808CI was made in a Japan plant and sounds great, IMO. I don't route video signals through it and 5.1 Dolby for 4K UHD audio through Toslink is good enough for me for movies until I move into a new place with a room and ceiling allowing for Atmos. I had bought this Denon used and was hoping to avoid buying another AVR until then. Will need to look into resetting it but recall doing that and also trying to get a newer firmware over Ethernet but to no avail.

 

[lovinthehd]

I'd try the reset again in any case. I've also got a 3808 out in my workshop, still working fine until recently where the left channel sometimes comes on at reduced volume (but turning the master volume up high briefly brings it back to normal), reminds me I've gotta try a reset myself! Then again it may be time for a new avr, doubt the 3808 is all that worthy of repair costs.

 

[homeaudionoob]

OK, I'll try that. I definitely wouldn't pay to have it repaired but if there was a known fixable issue like cold soldering joints, I'd do that myself. Thanks

 

[Eppie]

OK, I'll try that. I definitely wouldn't pay to have it repaired but if there was a known fixable issue like cold soldering joints, I'd do that myself. Thanks

Like so many modern devices a repair often requires replacing an entire module and that's if you can get the parts. Rather frustrating for those of us that used to be able to repair amplifiers quite easily. If they are easily accessible, going over the solder joints should not do any harm as long as you know how to avoid overheating the parts and keeping static electricity away from the ICs. The challenge with an AVR is the multiple layers of circuit boards and ribbon cables, making access a little complicated. For the uninitiated you need to be willing to dive in knowing that things may end up worse. The amplifier section is easily identifiable because the power transistors or modules are mounted to the large heat sinks. Remember to let the AVR sit, unplugged from the wall, for a good while to drain the capacitors. The large caps on the power supply store a lot of electricity.

 

[lovinthehd]

Still, it sounds more like a software/firmware glitch than just physical wiring for the amp section....and thats what makes repairs difficult like Eppie said....

 

[homeaudionoob]

So, here's an update I thought I'd share for good measure in case it helps narrow things down and someone else with the same issue: if one of the speakers isn't playing, I can bring it back (wake up the channel) by pushing the cone in, carefully of course.

 

[lovinthehd]

Sounds like the speaker's wiring then, maybe the voice coil leads (?) are about to go....

 

[TLS Guy]

Sounds like the speaker's wiring then, maybe the voice coil leads (?) are about to go....

I agree, it sounds as if there has to be voice coil damage to the loudspeaker drivers.

 

[Eppie]

Yup, sounds like a voice coil issue. The only thing you can check visually is the connection from the speaker terminals to the voice coil, usually a copper braided wire that runs from the terminal strip to the cone. Resoldering at the terminal strip is simple. Resoldering the voice coil connection is not for the uninitiated. You can permanently damage the speaker.

Anything internal will require having the speaker reconed (replacing the speaker cone and voice coil). That's an option for professional speakers but not typically available in the consumer market. For consumer speakers it usually requires replacing the entire driver.

 

[homeaudionoob]

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

 

[Pogre]

As always, check all of your connections and make sure there are no frayed strands of wire touching the opposite binding posts or bare spots in between.

 

[Pogre]

Sounds like the speaker's wiring then, maybe the voice coil leads (?) are about to go....

That was my first thought. This sounds similar to what was going on with my old setup when one of my puppies got to one of my speaker wires.

 

[Pogre]

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

No, not all, but you might have a short somewhere. Check all of your connections and make sure everything is clean. No stray strands at the connection points.

 

[TLS Guy]

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

Well if moving the cones, reliably brings the sound back, then I can't see how the problem can not be in the speaker.

I repeatedly advise against using the 5 channel stereo mode. This puts the same power on all the amps, and the same power to all speakers.

Now Denon have deliberately obfuscated the specification, with a meaningless 130 W X 7 power rating. One thing I can tell you for sure is that it is not going to produces 130 watts to more than 1 channel at once. So my strong bet that in 5 channel stereo mode the power is actually 26 watts X 5.

So that would mean you likely have been clipping all five amps running it in 5 channel stereo mode. Therefore there is a very good chance you have damaged all your speakers.

 

[Eppie]

It never hurts to double check the wiring as Pogre suggested, but you can do further testing with a multi-meter. The next time the speaker cuts out, disconnect the speaker cables at the speaker and measure the resistance at the speaker terminals. Then gently push the cone in as before and see if the resistance drops when the internal wire makes contact again. If the resistance changes while the speakers cables are not connected, then you have confirmed that it is internal to the speaker.

 

[lovinthehd]

Well if moving the cones, reliably brings the sound back, then I can't see how the problem can not be in the speaker.

I repeatedly advise against using the 5 channel stereo mode. This puts the same power on all the amps, and the same power to all speakers.

Now Denon have deliberately obfuscated the specification, with a meaningless 130 W X 7 power rating. One thing I can tell you for sure is that it is not going to produces 130 watts to more than 1 channel at once. So my strong bet that in 5 channel stereo mode the power is actually 26 watts X 5.

So that would mean you likely have been clipping all five amps running it in 5 channel stereo mode. Therefore there is a very good chance you have damaged all your speakers.

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%)....