Question Subwoofer problems; any ideas?

[JohnV]

I have a KEF PSW4000 subwoofer. It has worked well for c5 years.

Recently I changed my AVR to a Yamaha 777. Initially I had problems setting the subwoofer up and it was never recognised in the auto setup, i.e. never output a sound. Swapping around lots of cables, turning things off and on, etc. eventually sorted it, but it wasn't very scientific and it wasn't obvious what the problem was.

Now the problem has re-emerged and once again I can get no output from the sub, although it may be different this time.

Everything in the AVR menu is setup as if a sub is connected. A sub signal is being output according to the amp display. If I power off the sub at the wall and then power it back on again, the sub switches on and it outputs as normal for about 2-3 seconds, then stops. Everything else appears functional on the subwoofer, e.g. the volume, crossover and phase adjusters, but whatever I do I can't get any output. If I switch it of and on at the wall I get the same 2-3 seconds and it repeats. It's almost as though some sort of protection is kicking in, but for the life of me I don't know what.

I've sent an email to KEF, but obviously open to any other suggestions. It's a very sizeable paper weight at the moment!

 

[fatboy frank]

What trim levels has the Yamaha set for the sub, or hasn't it ? if the levels are high in the negative value ie -10 dB or even higher and the sub has an auto on/off sensing circuit, the signal getting through to the sub might not be high enough to make the sub work! Hope that makes sense ?

If the sub is being seen, try and adjust the dB figure up, start it off at 0dB, as a rule i try to keep them within +/- 6dB, adjust the sub gain on the sub itself to get an even balance, ie ..... if the figure in the Yamaha is too low, it generally means the Sub volume is too high, so back it off accordingly, obviously this works the other way around too.

 

[JohnV]

The level on the amp is currently set to 0 dB, although I have tried this at various settings, e.g. all the way up to the max +10 dB.

The sub has an auto on/off sensing circuit and can be set to auto to use this, or left in manual to always be on. I have set it on manual. When the output from the sub stops after 2-3 seconds (until I turn it off an on at the mains for the process to repeat) it doesn't go into standby or power down; it just doesn't output.

 

[fatboy frank]

Ok, so sounds like there is either a problem with the sub itself, the lead or possibly the sub/LFE out on the Yamaha. Have you tried a known good RCA lead to the sub, bit of a longshot, but worth cleaning all the contacts too.

 

[JohnV]

I'm going to give that another go today. I would have thought, however, that if it was something to do with the leads or contacts that it simply wouldn't work, not that one could get 2-3 seconds of normality by turning the sub off and on again without touching anything else before the output stops.

 

[fatboy frank]

I'm going to give that another go today. I would have thought, however, that if it was something to do with the leads or contacts that it simply wouldn't work, not that one could get 2-3 seconds of normality by turning the sub off and on again without touching anything else before the output stops.

I agree but it can't do any harm. The other thing i'd maybe try is bypass the line input and try running direct to the speaker terminals, or if you have an MP3 player or similar hook that up directly to the sub and bypass the Yamaha to see if it works then, however, i suspect it is more likely to be a fault with the sub itself.