phantom cone excursion

Swifty · 20th July 2011, 10:33 AM

Hi everybody,

On some tracks my loudspeakers (Pensil 10.2) exhibit a very worrying behaviour: The cone excursion just goes crazy, while the music is not playing any low frequency notes. Now, I have previously noticed this on my previous loudspeakers, a pair of Tannoy D300's.

What could be the cause? Could it be the amp? It's a hybrid amp, a Unison Research Unico. Could dying tubes in the pre amp stage cause this kind of behaviour?

IG81 · 20th July 2011, 12:17 PM

Is your source a record player? It could be some kind of ELF feedback loop. If it was an amp power supply AC leak, you'd likely hear it at 60Hz or 120Hz (or make that 50Hz or 100Hz in your country?) depending on design.

IG

Swifty · 20th July 2011, 12:51 PM

No, the source is a cd player. I also played the offending tracks on my dvd player, with the same results.

Cal Weldon · 20th July 2011, 01:42 PM

It's likely just source material that is too low for you to hear.

chris661 · 20th July 2011, 03:34 PM

Agreeing with Cal here.

I've heard of studios that have picked up near-by trains and things like that, which add a lot of LF content.

To be on the safe side (for your speakers/amp's sake), it would probably wise to add in an infrasonic filter, to cut out the frequencies that'll cause silly excursion with no output.

Chris

mondogenerator · 20th July 2011, 03:43 PM

i have found this with some 'action' movie DVDs. Some SFX 'rumbles' are subsonic and i have no idea why they are present, i always thought the BW of CD/DVD was 20-20k, but these are maybe 5hz tones. I can only imagine that they are to move air and provide 'IMPACT', but they just seem to waste my amps power, and unload the speaker.

simon7000 · 20th July 2011, 03:50 PM

Does the cone move when everything is connected but the CD is not playing?

enigmaticEntity. · 20th July 2011, 04:11 PM

I have a RadioShack amp that produced 1Hz excursions on the woofer when music was turned up. Replacing a bulging and cracked capacitor seemed to fix the problem. Perhaps something to check?

Also, you could try some very large caps on the audio output, to reduce signals below 20Hz, for example. That is if you don't fix the problem another way...

vacuphile · 20th July 2011, 04:19 PM

I have had a similar situation with my McIntosh pre-amp, same problem as mentioned by enigmaticEntity.

Only question I have is where Swifty mentions that this happens only 'on some tracks', pointing to perhaps a different problem altogether.

Cal Weldon · 20th July 2011, 04:21 PM

I think we all have that problem. Interesting to find out if Swifty is the same as most of us. Like Chris says: Studio too close to train tracks or is there is actually something wrong.

20th July 2011, 10:33 AM	#1
Swifty diyAudio Member Join Date: Jun 2004 Location: Holland	phantom cone excursion Hi everybody, On some tracks my loudspeakers (Pensil 10.2) exhibit a very worrying behaviour: The cone excursion just goes crazy, while the music is not playing any low frequency notes. Now, I have previously noticed this on my previous loudspeakers, a pair of Tannoy D300's. What could be the cause? Could it be the amp? It's a hybrid amp, a Unison Research Unico. Could dying tubes in the pre amp stage cause this kind of behaviour?

20th July 2011, 01:42 PM	#4
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	It's likely just source material that is too low for you to hear. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

20th July 2011, 03:34 PM	#5
chris661 diyAudio Member Join Date: Feb 2008 Location: Lancashire Blog Entries: 7	Agreeing with Cal here. I've heard of studios that have picked up near-by trains and things like that, which add a lot of LF content. To be on the safe side (for your speakers/amp's sake), it would probably wise to add in an infrasonic filter, to cut out the frequencies that'll cause silly excursion with no output. Chris __________________ "Throwing parts at a failure is like throwing sponges at a rainstorm." - Enzo My setup: http://www.diyaudio.com/forums/multi...tang-band.html

20th July 2011, 03:43 PM	#6
mondogenerator diyAudio Member Join Date: Sep 2009 Location: England	i have found this with some 'action' movie DVDs. Some SFX 'rumbles' are subsonic and i have no idea why they are present, i always thought the BW of CD/DVD was 20-20k, but these are maybe 5hz tones. I can only imagine that they are to move air and provide 'IMPACT', but they just seem to waste my amps power, and unload the speaker. __________________ Im starting to think its gone beyond a hobby, a wardrobe full of drivers instead of clothes...

20th July 2011, 04:19 PM	#9
vacuphile diyAudio Member Join Date: Apr 2011 Location: Seaside	I have had a similar situation with my McIntosh pre-amp, same problem as mentioned by enigmaticEntity. Only question I have is where Swifty mentions that this happens only 'on some tracks', pointing to perhaps a different problem altogether. __________________ If my 15 V DC were the radius of the Earth, Mount Everest would be 1 meter tall.


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20th July 2011, 12:17 PM	#2
IG81 diyAudio Member Join Date: Feb 2008	Is your source a record player? It could be some kind of ELF feedback loop. If it was an amp power supply AC leak, you'd likely hear it at 60Hz or 120Hz (or make that 50Hz or 100Hz in your country?) depending on design. IG

20th July 2011, 12:51 PM	#3
Swifty diyAudio Member Join Date: Jun 2004 Location: Holland	No, the source is a cd player. I also played the offending tracks on my dvd player, with the same results.

20th July 2011, 03:50 PM	#7
simon7000 diyAudio Member Join Date: Nov 2008 Location: Oakmont PA	Does the cone move when everything is connected but the CD is not playing?

20th July 2011, 04:11 PM	#8
enigmaticEntity. diyAudio Member Join Date: Oct 2009 Location: Tasmania	I have a RadioShack amp that produced 1Hz excursions on the woofer when music was turned up. Replacing a bulging and cracked capacitor seemed to fix the problem. Perhaps something to check? Also, you could try some very large caps on the audio output, to reduce signals below 20Hz, for example. That is if you don't fix the problem another way...

20th July 2011, 04:21 PM	#10
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	I think we all have that problem. Interesting to find out if Swifty is the same as most of us. Like Chris says: Studio too close to train tracks or is there is actually something wrong. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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