Random LFE Thumps - NBC Network Broadcasts Only! - AVS Forum
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Old 11-07-2012, 07:03 PM - Thread Starter
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Having this extremely strange audio problem. At first I thought my subwoofer was failing but convinced it's something inside the Dolby Digtal audio track of the encoded HD signal.

Some Key A/V Info:

- Tivo HD Series 3 HDMI connected to receiver. Audio Setting on Tivo: Dolby Digital

- Onkyo NR-709 Receiver with 7.1 Surround speakers. Audio Setting: Dolby Digital Expanded

- Panamax 5400 filtering power and HFC cable TV Signal


With the local NBC Affiliate here outside Boston, I am receiving random audio LFE thumps from my subwoofer ONLY during Network broadcasts, NOT the local NBC affiliate broadcasts (WHDH in Boston). The problem ONLY happens during NBC Today show, NBC Nightly News, Presidential Election night. NEVER during any other local or network broadcast on any other HD Channel.

Facts:
- Thumps can be heard in same scenario with HFC cable connected directly to clear QAM Tuner TV card in my PC. This tells me it's not the Tivo.

- Thumps occur in the same scenario with HFC cable connected directly to my Samsung LED TV using clear QAM tuner inside TV Set. This tells me it's NOT the Tivo.

- Random thumps ARE recorded on the Tivo. I can play them back to the cable company when they are here to diagnose the problem.

- Cable company came in and tested the QAM frequency (607) and it's clear and almost error free.


I contacted the NBC affiliate in Boston regarding this problem but they weren't aware of the problem. Had the local cable company out here and inquired if the "Network" broadcast feed was coming in via satellite and being re-encoded and spliced locally with the Boston affiliate station. Nope, they only have one signal off the satellite and they do no encoding or re-modulation.

What I DID find: Whatever is encoded in the original Audio track coming into my Tivo is "filtered out" when I set the Tivo to down convert to PCM. In this mode, I can't run Dolby Digital Expanded, audio sounds OK but I am stuck on THX Cinema.

This problem doesn't happen on ANY other HD channel that I might watch. FOX, CBS, ABC etc...ONLY NBC and ONLY during Network originating broadcasts.

Suggestions Anyone? Grasping at straws here.
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Old 11-08-2012, 05:58 AM
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Quote:
Originally Posted by howardru View Post

Having this extremely strange audio problem. At first I thought my subwoofer was failing but convinced it's something inside the Dolby Digtal audio track of the encoded HD signal.

Some Key A/V Info:

- Tivo HD Series 3 HDMI connected to receiver. Audio Setting on Tivo: Dolby Digital

- Onkyo NR-709 Receiver with 7.1 Surround speakers. Audio Setting: Dolby Digital Expanded

- Panamax 5400 filtering power and HFC cable TV Signal


With the local NBC Affiliate here outside Boston, I am receiving random audio LFE thumps from my subwoofer ONLY during Network broadcasts, NOT the local NBC affiliate broadcasts (WHDH in Boston). The problem ONLY happens during NBC Today show, NBC Nightly News, Presidential Election night. NEVER during any other local or network broadcast on any other HD Channel.

Facts:
- Thumps can be heard in same scenario with HFC cable connected directly to clear QAM Tuner TV card in my PC. This tells me it's not the Tivo.

- Thumps occur in the same scenario with HFC cable connected directly to my Samsung LED TV using clear QAM tuner inside TV Set. This tells me it's NOT the Tivo.

- Random thumps ARE recorded on the Tivo. I can play them back to the cable company when they are here to diagnose the problem.

- Cable company came in and tested the QAM frequency (607) and it's clear and almost error free.


I contacted the NBC affiliate in Boston regarding this problem but they weren't aware of the problem. Had the local cable company out here and inquired if the "Network" broadcast feed was coming in via satellite and being re-encoded and spliced locally with the Boston affiliate station. Nope, they only have one signal off the satellite and they do no encoding or re-modulation.

What I DID find: Whatever is encoded in the original Audio track coming into my Tivo is "filtered out" when I set the Tivo to down convert to PCM. In this mode, I can't run Dolby Digital Expanded, audio sounds OK but I am stuck on THX Cinema.

This problem doesn't happen on ANY other HD channel that I might watch. FOX, CBS, ABC etc...ONLY NBC and ONLY during Network originating broadcasts.

Suggestions Anyone? Grasping at straws here.

Add a high pass filter to the segment of the signal chain that is giving you the thumps. There's a high probability that you aren't receiving anything really ugly via your TIVO, but that the subsonic response of your system is tipped up quite a bit, and turning rapid temporary losses of signal or subsonic disturbances into more than they started out to be. A lot of people are finding that if they put a high pass fitler in line with their subwoofer so that it only sees signals that it can respond to cleanly, the sound quality of their system is greatly improved.
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Old 11-08-2012, 11:57 AM - Thread Starter
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Thanks for the advise and responding.

Maybe my explanation sounded intelligent, but my knowledge is limited here in the audio stream.

How, where and what piece of electronics am I looking to buy? Is there some frequency that I should be specifying to filter out? Can you provide a URL to Amazon or some electronics store that I can get an idea as to what you are referring to?

Thanks
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Old 11-08-2012, 05:02 PM
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Quote:
Originally Posted by howardru View Post

Thanks for the advise and responding.

Maybe my explanation sounded intelligent, but my knowledge is limited here in the audio stream.

How, where and what piece of electronics am I looking to buy? Is there some frequency that I should be specifying to filter out? Can you provide a URL to Amazon or some electronics store that I can get an idea as to what you are referring to?

Not a lot of options.

The class of device is called a "Subsonic Filter".

Here's an example:

http://www.kabusa.com/rf1.htm



Less preferred:

http://store.hlabs.com/pk4/store.pl?view_product=12




Some powered subwoofers have a built-in "Subsonic Filter".
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Old 11-08-2012, 05:51 PM - Thread Starter
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I have a Polk DSW Pro 600....I'm not seeing it in the specs, would you happen to know if Polks has this?

http://www.polkaudio.com/products/dswpro600
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Old 11-08-2012, 10:57 PM
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Quote:
Originally Posted by howardru View Post

Having this extremely strange audio problem. At first I thought my subwoofer was failing but convinced it's something inside the Dolby Digtal audio track of the encoded HD signal.

Some Key A/V Info:

- Tivo HD Series 3 HDMI connected to receiver. Audio Setting on Tivo: Dolby Digital

- Onkyo NR-709 Receiver with 7.1 Surround speakers. Audio Setting: Dolby Digital Expanded

- Panamax 5400 filtering power and HFC cable TV Signal


With the local NBC Affiliate here outside Boston, I am receiving random audio LFE thumps from my subwoofer ONLY during Network broadcasts, NOT the local NBC affiliate broadcasts (WHDH in Boston). The problem ONLY happens during NBC Today show, NBC Nightly News, Presidential Election night. NEVER during any other local or network broadcast on any other HD Channel.

Facts:
- Thumps can be heard in same scenario with HFC cable connected directly to clear QAM Tuner TV card in my PC. This tells me it's not the Tivo.

- Thumps occur in the same scenario with HFC cable connected directly to my Samsung LED TV using clear QAM tuner inside TV Set. This tells me it's NOT the Tivo.

- Random thumps ARE recorded on the Tivo. I can play them back to the cable company when they are here to diagnose the problem.

- Cable company came in and tested the QAM frequency (607) and it's clear and almost error free.


I contacted the NBC affiliate in Boston regarding this problem but they weren't aware of the problem. Had the local cable company out here and inquired if the "Network" broadcast feed was coming in via satellite and being re-encoded and spliced locally with the Boston affiliate station. Nope, they only have one signal off the satellite and they do no encoding or re-modulation.

What I DID find: Whatever is encoded in the original Audio track coming into my Tivo is "filtered out" when I set the Tivo to down convert to PCM. In this mode, I can't run Dolby Digital Expanded, audio sounds OK but I am stuck on THX Cinema.

This problem doesn't happen on ANY other HD channel that I might watch. FOX, CBS, ABC etc...ONLY NBC and ONLY during Network originating broadcasts.

Suggestions Anyone? Grasping at straws here.


You are being deceptive when you say "network originating broadcasts". Then you only mention live network news shows.

You get those thumps because you are talking about live news shows. You even get those thumps on local news shows. Just unintended thumps related to the use of live microphones. The election night results on NBC had thumping noise that was quite loud and happened quite often. I had to turn the subwoofer off for the night.
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Old 11-08-2012, 11:12 PM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by howardru View Post

Having this extremely strange audio problem. At first I thought my subwoofer was failing but convinced it's something inside the Dolby Digtal audio track of the encoded HD signal.

Some Key A/V Info:

- Tivo HD Series 3 HDMI connected to receiver. Audio Setting on Tivo: Dolby Digital

- Onkyo NR-709 Receiver with 7.1 Surround speakers. Audio Setting: Dolby Digital Expanded

- Panamax 5400 filtering power and HFC cable TV Signal


With the local NBC Affiliate here outside Boston, I am receiving random audio LFE thumps from my subwoofer ONLY during Network broadcasts, NOT the local NBC affiliate broadcasts (WHDH in Boston). The problem ONLY happens during NBC Today show, NBC Nightly News, Presidential Election night. NEVER during any other local or network broadcast on any other HD Channel.

Facts:
- Thumps can be heard in same scenario with HFC cable connected directly to clear QAM Tuner TV card in my PC. This tells me it's not the Tivo.

- Thumps occur in the same scenario with HFC cable connected directly to my Samsung LED TV using clear QAM tuner inside TV Set. This tells me it's NOT the Tivo.

- Random thumps ARE recorded on the Tivo. I can play them back to the cable company when they are here to diagnose the problem.

- Cable company came in and tested the QAM frequency (607) and it's clear and almost error free.


I contacted the NBC affiliate in Boston regarding this problem but they weren't aware of the problem. Had the local cable company out here and inquired if the "Network" broadcast feed was coming in via satellite and being re-encoded and spliced locally with the Boston affiliate station. Nope, they only have one signal off the satellite and they do no encoding or re-modulation.

What I DID find: Whatever is encoded in the original Audio track coming into my Tivo is "filtered out" when I set the Tivo to down convert to PCM. In this mode, I can't run Dolby Digital Expanded, audio sounds OK but I am stuck on THX Cinema.

This problem doesn't happen on ANY other HD channel that I might watch. FOX, CBS, ABC etc...ONLY NBC and ONLY during Network originating broadcasts.

Suggestions Anyone? Grasping at straws here.

Add a high pass filter to the segment of the signal chain that is giving you the thumps. There's a high probability that you aren't receiving anything really ugly via your TIVO, but that the subsonic response of your system is tipped up quite a bit, and turning rapid temporary losses of signal or subsonic disturbances into more than they started out to be. A lot of people are finding that if they put a high pass fitler in line with their subwoofer so that it only sees signals that it can respond to cleanly, the sound quality of their system is greatly improved.



The thumping on NBC election news was above the subsonic range (may have also included infra). Loud live microphone thumps galore on that live program. Very unusual. Seems that most people on AVS that have he man subwoofers do not use them on a daily basis. If they did, you would hear more about this issue.
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Old 11-09-2012, 05:36 AM
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Quote:
Originally Posted by howardru View Post

I have a Polk DSW Pro 600....I'm not seeing it in the specs, would you happen to know if Polks has this?

http://www.polkaudio.com/products/dswpro600

From the owner's manual (online)



Short answer: no subsonic filter visible.
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Old 11-09-2012, 08:02 AM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by howardru View Post

I have a Polk DSW Pro 600....I'm not seeing it in the specs, would you happen to know if Polks has this?

http://www.polkaudio.com/products/dswpro600

From the owner's manual (online)



Short answer: no subsonic filter visible.




That is a ported subwoofer, so it most likely has a fixed high pass filter near the 20 Hz area.
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Old 11-09-2012, 08:09 AM
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Quote:
Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by howardru View Post

I have a Polk DSW Pro 600....I'm not seeing it in the specs, would you happen to know if Polks has this?

http://www.polkaudio.com/products/dswpro600

From the owner's manual (online)



Short answer: no subsonic filter visible.




That is a ported subwoofer, so it most likely has a fixed high pass filter near the 20 Hz area.

I would need a schematic to be convinced about that. ;-)
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Old 11-09-2012, 08:10 AM - Thread Starter
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Thanks guys. I'll look into this.
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Old 11-09-2012, 10:55 AM
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I've noticed a lot of mic thumping on the ABC College football games and also get pops on FM radio from the dj's when using words with P's and B's. It happens in my car audio also so it's them and not the system.
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Old 11-10-2012, 02:15 PM
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I always thought that this is just not a perfect world. I simply turn down the sub when watching live sports ...football...baseball...not much bass in there anyway, the commercials come on too loud:D

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Old 11-11-2012, 06:29 PM - Thread Starter
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Guys, I'm not convinced it's a microphone issue. It doesn't always happen during a segment when someone is talking. I'll capture the segment and rip it from my Tivo and post here for all to view.
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Old 12-07-2012, 05:41 PM
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YES! I have the same problem. Boston here too.
I have tweeted many times to NBC, DirecTV and WHDH many times about it.

Only happens on NBC especially during NBC Nightly news but I noticed its usually during live national broadcasts.
I don't think it has ever happened during a regular show (The office...etc) and I doubt its a mic issue since it happens at random times during the broadcasts (pre-recorded segments and sometimes national commercials)

Ichiro
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Old 12-07-2012, 06:10 PM - Thread Starter
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OMG..Finally! Someone to prove I'm not crazy


The problem continues. I happened to be swapping out my Tivo 3 for a new Tivo Premiere 4 this morning and I heard the problem on the clear QAM tuner on my Sony TV this am. I also heard the problem on the clear QAM tuner on my Happauge TV card in my windows 7 PC a few days ago.

It's definitely something in the Dolby audio track but I just don't know what to do.


I'm on SELCO cable in Shrewsbury, but it looks like you're on DirecTV which tells me it's not a SELCO problem either.

What now?
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Old 12-10-2012, 06:21 PM
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You could try contacting the station and asking to speak to the lead engineer, or check their website for his email address and fire off an email to him. I have had to do this with local stations in regards to closed caption issues before.

Bill
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Old 12-13-2012, 03:02 PM
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I didn't hear the problem last night. Lets hope the same is tonight.
I tweeted it out to them with a link to this thread so maybe they will actually (or may have) fix it.

https://twitter.com/IchiroA/status/277210872869433344

Yes, im on DirecTV and it happens on both my boxes and the LFE display lights up on my receiver when it happens.

Ichiro
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Old 12-20-2012, 04:37 PM
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Good news! WHDH verified and was able to hear the problem too! They are working on it.
We are not crazy wink.gif

Ichiro
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Old 12-20-2012, 09:29 PM
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I also get the same bumps here in the Northwest.
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Old 12-21-2012, 07:40 AM
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Thanks for the info, I will pass it along.
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