Question Faulty AVR or sub??

bandyka

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Well, my system has been acting funny lately when it comes to bass response. I cannot figure out if its the sub or the processor for certain.

Components are in my signature.

So the issues are:
- Cannot raise test tone in AVR higher then +5db as the subwoofer cuts out completely (fine if plugged into one of the main pre-out on the AVR but than its not the same test tone frequency)
- Sub making cracking popping noise at certain frequencies between 70-90hz over a certain volume when bass heavy content is played such as EDM music with pumping bass.
- ARC room correction detects sub low frequency extension at 30hz, it used to be lower than 20hz as the sub is capable of that.
- pulled out the sub out connector board of the AVR and no problems were detected on inspection its a simple connector board.
- the sub has a built in test sweep which goes fine.
- the sub gets enough power I checked.
- using the sub's gain control to raise volume instead of the AVR it plays the test tone fine at any loudness without the popping noise however the certain cracking popping noise with content sounds like a driver problem..??

Tested a new sub cable as well. Reset AVR.

So trying to be as sure I can be before sending them in for repair as the sub is 50kg and I am in the country so its not an easy exercise.

Thoughts are appreciated.
 
The sub may be cutting out because you are putting too much strain upon its internal amp? =5db would be a higher volume than the receiver would ordinarilly calibrate reference to and is 5db greater than reference. Lower frequencies such as those ordinarily dealt with by a sub (lelow 120Hz) require more power to amplify them than higher end frequencies and such frequencies put more strain upon amplifiers. The sub may simply be invoking its own integral safety circuitry in order to prevent damage being caused to the sub's amplifier?

The only thing that makes the above unlikely is the 850 watts available via your sub's own amp. Your AV receiver would either need to be incorrectly calibrated or you'd need to be some considerable distance away from the sub for it to have to power itself down because of its amp being put under too much strain.

Try decreasing the receiver's sub level via its configurations and then try outputting the test tone again with the master volume set to 0db. You'd then need to measure the output from your seated listening position and adjust the sub's level until you get an SPL reading of 85db. If this still results in the issues you were having then yes, the sub has a fault or you are sat way too far away from it?

Why are you trying to output a test tone at +5db? You'd only need to send a test tone with a master volume of 0db in order to be able to calibrate your setup and or to level the speakers.
 
mmm thanks for the response and while what you are suggesting would be true when its being over driven there is not too much strain on the sub, +5 is not even close to overdrive as it also depends on the manual sub gain control its a beast of sub it can take a whole lot more, the AVR autocal set it to +7. I checked it is drawing up to 300watts of power at my listening levels. When it cuts out its around 80db it should be able to do well over 90db as it used to. I can't be too far as the cable is the same nothing changed in terms of setup for years and also tested another shorter cable. It has to be an electrical fault but I am not sure if its the sub or the processor. This is what I ma trying to ascertain.
 
Checked again. It cuts out at 84db however it can be driven to any level via the manual sub level control so logically it should be the AVR that cuts out however why is the popping cracking sound at 70-90hz that sounds like a bad driver?
 
Another test. Lowered the sub to its lowest setting yet it still cuts out at +5db in the AVR so no matter the actual sub output. It seems it is the processor.
 
When you say "cuts out" then what exactly do you mean? Is the sub itself powering down or do you mean that it is simply no longer outputting anything? If the latter then yes, it is quite possible that there's an issue with the pre out onboard the AV receiver or with the processing/circuitry associated with that channel?

What about the bass management on the AV receiver, what are your configurations in terms of speaker sizes and crossovers? If set to SMALL then maybe try things with the speakers set as large in order to determine whether or not the issue is with the discrete :FE channel, frequencies being directed by crossovers or both?
 
The sub turns off as if it was being over driven so I am guessing the processor outputs the signal in a way that drives the sub into protection mode.
Any bass management configuration will end up in the same result. When running the test tone bass management does not apply as far as I know.
 
The AV receiver is simply conveying a variable line level signal to the sub. It is only the sub's own amp that could be invoking the sub's protection mode. If so then reducing the subs own level should reduce the amplification power being employed. The issue would be why is the sub amplifying the signal to such a degree if correctly calibrated? Have you tried running the receiver calibration to ensure that it is correctly calibrated? THe only other reason for the sub's amp to strain itself and overheat would be if you are sat so far away from it that iy is having to run full pelt to attain reference relative to your listening location?
 
As i mentioned above I can drive the sub at any level when adjusting the manual level knob so that rules out the sub amp IMO unless it's somehow misinterpreting the signal form the processor.
Also running the sub at the lowest level does not solve the problem even when it literally is silent.
I sit 1.5 meter from the sub. It is not running any louder or being driven harder then it used to be.
 
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If the sub itself is shutting itself down then it has to be the sub doing this due to it overheating. The only reason for this would be if the sub's amp it struggling. Processing onboard the AVR wouldn't invoke the sub's protection circuitry. The only other thingI can think of is if there's a short onboard the AV receiver and the AV receiver is in some way conveying this to the sub's analogue LFE input? Maybe there's dodget earthing between the AVR's sub pre out and the sub's LFE input?
 
If the sub itself is shutting itself down then it has to be the sub doing this due to it overheating. The only reason for this would be if the sub's amp it struggling. Processing onboard the AVR wouldn't invoke the sub's protection circuitry. The only other thingI can think of is if there's a short onboard the AV receiver and the AV receiver is in some way conveying this to the sub's analogue LFE input? Maybe there's dodget earthing between the AVR's sub pre out and the sub's LFE input?
Yes that is the only logical explanation I can arrive at as well. As if the sub was overheating it would shut down with any output not just the test tone. This is what I am trying to figure out how to test and diagnose.
 
Another thing I recall. There was a huge 15-20 db dip in the frequency range at 26-28hz which seems to have gone after re-seating the sub pre-out board. ARC only picks up the sub response starting at 28-30hz so there could be something there...
 
Another thing I recall. There was a huge 15-20 db dip in the frequency range at 26-28hz which seems to have gone after re-seating the sub pre-out board. ARC only picks up the sub response starting at 28-30hz so there could be something there...

...
 
I am going to try 2 things today. Plug in one of the mains into the sub pre-out to see if test tones fail, hook up the sub to an old Technics amp to see if it plays ok, it doesn't do test tones but there is a techno tune with heavy bass I found that causes the popping sound every time time so I'll test with that played through the Panny UHD player.
 
Well. Signs are pointing to a bad sub driver unfortunately but I could be wrong. Tested with a tune with heavy bass at the frequencies that produces the popping/cracking noise and it only seems the be coming from one of the drivers (the sub has opposing dual drivers) so could this cause the sub to go into protection mode when running the test tones and to generally reduce performance I wonder?
Also tested the sub shuts off at around 85db when running the test tone.
 
It could be simply a dry joint on the soldering some where.
The vibrations could be simply causing the joint to arc, or heat can do the same. The joint will split slighty when it gets warm.
The only thing you can really do is get it checked out professionally. Or take the amp plate out yourself, if you feel confident enough and go over the whole board with a powerful magnifying glass. The dry joint can show up as the tiniest of a line on the joint, you really have to take your time.
On my Rel B1 it was farting every now and then so I checked the board. I found about 6 or 7 possible dry joints, they probably were mostly ok, but I resoldered the lot anyway.
Job sorted, still ok after a couple of years now.
Also check the board for evidence of burn marks, like a black soot deposit. Again this could be tiny.
If you have a friend with the same sub, swap the amp boards in yours to see if the problem persists. If it sorts it, it's your amp, (though I doubt it), or the driver is humped.
Good luck and I hope you get sorted soon.
 
It could be simply a dry joint on the soldering some where.
The vibrations could be simply causing the joint to arc, or heat can do the same. The joint will split slighty when it gets warm.
The only thing you can really do is get it checked out professionally. Or take the amp plate out yourself, if you feel confident enough and go over the whole board with a powerful magnifying glass. The dry joint can show up as the tiniest of a line on the joint, you really have to take your time.
On my Rel B1 it was farting every now and then so I checked the board. I found about 6 or 7 possible dry joints, they probably were mostly ok, but I resoldered the lot anyway.
Job sorted, still ok after a couple of years now.
Also check the board for evidence of burn marks, like a black soot deposit. Again this could be tiny.
If you have a friend with the same sub, swap the amp boards in yours to see if the problem persists. If it sorts it, it's your amp, (though I doubt it), or the driver is humped.
Good luck and I hope you get sorted soon.
Thank you. I was going to pull the sub apart and inspect it so you just gave me the go ahead :)
 

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