Audyssey sub management warning/problem - AVS Forum
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post #1 of 4 Old 05-02-2013, 12:06 PM - Thread Starter
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I posted this in the audyssey thread, but realized it could be important as a stand alone so it doesn't get buried and is seen by people that aren't 'experts' so they can avoid potential damage to their sub. I am an audyssey fan and hope to have a response from them soon on how best to remedy this:


Have some bad news to report about Audyssey's sub management.

Background: have a HRS 12 Sunfire 1000watt sub thats rated 18hz-100hz. I noticed some 'rattle' like sub distortion during 'the impossible' tsunami sequence. My sub is set to 3 out of 10 on the gain and the audyssey trim applied is -0.5db.

I contacted the sub company and we've been troubleshooting for the past few days. What we found was startling. The 'distortion' only happened in the 10-15hz sound spectrum. With audyssey off, there was no distortion at all during the bass sweeps. With it on, the rattling/gurgle was back. The technician re did the audyssey setup and the 'distortion' came back in the same range. Turns out Audyssey is boosting the subsonic 20hz region significantly.

The 'distortion' wasn't distortion at all either, it was the spider coil slamming into the cone and even just seconds of this type of abuse can damage my expensive subwoofer.


I've written to Audyssey and am waiting on a response on how I can enjoy Audyssey room correction in a way that doesn't damage or distort my subwoofer.
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post #2 of 4 Old 05-02-2013, 12:28 PM
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Suggest you try a different location for the subwoofer..
Pulling out from the wall and/or corner can make a big difference.
No Room EQ scheme is perfect...
Sounds like you have a low frequency acoustic resonance from the room/furnishings, and the Audyssey software is having a challenge in dealing with..

Note that we have the Audyssey Pro setup and have experienced this issue previously.

Just my $0.02... 👍😉
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post #3 of 4 Old 05-02-2013, 12:46 PM - Thread Starter
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thanks for the response. I'm going to try and pull it out a few more inches from the wall and see if that will help. Sticking it somewhere else entirely won't pass WAF. I'm waiting for a response from Audyssey and will post what they say.

I hope going forward there is someway to deal with subsonic boosts in the Audyssey MultiEQ room correction (disable switch maybe?) since this could easily damage any average joes subwoofer - and subs aren't cheap!

I love how well audyssey performs for the rest of the sound spectrum.
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post #4 of 4 Old 05-02-2013, 01:00 PM - Thread Starter
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Ok case closed IMO. See ths post from Batpig below.
Quote:
Originally Posted by batpig View Post

Audyssey will almost certainly give you the runaround and deny that their technology could damage the sub by boosting it below its capabilities. During the measurement they calculate the lower limit (F3) of the sub and the filters taper off below that point to avoid boosting the sub below its lower limit. However, the subwoofer can still be boosted below this frequency due to the "normalization" problem that has been amply discussed in this thread (also something else which Feri will deny exists despite the large body of evidence). One thing you didn't mention is what receiver you are using? There seems to be some evidence that Audyssey corrected the normalization problem in more recent models.

I do think the suggestion of moving the sub and re-running Audyssey could be effective. As some background, the "normalization" issue is caused by Audyssey re-leveling the sub channel to match the levels of the other speakers after its EQ correction is applied. After EQ correction, Audyssey looks at a narrow frequency band in the subwoofer's response (centered around 60Hz according to Chris K) and then raises/lowers the sub level to compensate for any major cuts/boosts in the frequency response. For example, if the sub level is set to 75dB to match the other speakers, but there are some giant peaks in the sub response in the 40-80Hz range that need to be tamed, after EQ the perceived level of the sub will now be well below 75dB because of the removal of those peaks. To maintain perceptual balance with the EQ filters enabled, Audyssey will "normalize" the subwoofer channel to the other speakers by globally boosting the subwoofer level to keep the perceived level the same with Audyssey on vs. off. Unfortunately, the global level boost when normalizing does NOT get filtered below the F3 of the sub, so if there is a large boost needed it will end up providing a lot of extra energy below the sub's F3. Relocating the sub to a different spot in the room may mean that Audyssey's EQ filters don't have to do as much cutting and lead to a more moderate normalization which won't overtax the sub.


See this post for some more info and links to other posts discussing the issue: http://www.avsforum.com/t/795421/official-audyssey-thread-faq-in-post-1/50430#post_21653246

And here is a graph from this post which shows a worst-case-scenario situation for this problem.




You can see some huge cuts in the 45-70Hz range in the equalized pre-out measurement (blue line) and then Audyssey raises the global level to match the un-EQ'd pre-out measurement (purple line).... but unfortunately this in a giant boost below 15Hz.


I'll go back to the main Audyssey thread. Looks like solution is a high pass filter or finding a spot in the room that doesn't cause this issue.
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