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Unsolvable Woofer Pumping (Phono only)

Doesn’t seem like feedback, since it happens when OP records onto Digital with speakers off, then plays back recording and observes pumping.

If all the TTs he tried have cartridges that have the ability to create a signal in the subsonic range, then if the digital recorder can record and playback in that range, the pumping is probably the result of subsonic rumble in the grooves of the records. The frequencies are on the records, they are just inaudible. Especially on the lead- in and run-out grooves.
As Classic Carl said, that’s what the subsonic filter is for.
 
turboyam said:
You should listen to everybody here, saying you need a subsonic filter. It's the only really usefull, and inaudible, filter ( Sub., low and high filters).
When using a TT, especially with high compliance woofers it's a must, full time insurance.
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I have been listening! I just wanted to be sure that it wasn't a different issue. I'll wait for my cheap in-line subsonic filters to come, try them, if I don't like them I'll get something better like a KAB RF-1. Or maybe (as another forum suggested) a subwoofer, which has a filter built in, and would improve my sound greatly :)
 
branden_8091 said:
I'm at a loss for trying to find the source of my "woofer pumping." It's most noteworthy when playing something that is mostly/all treble, and the woofers of my Focal Aria 906s are going nuts (inaudibly, of course). Turntable is a Debut Carbon with Ortofon 2M Blue.

Initially I was told it's an isolation problem, so I better isolated my TT, even put it right on the concrete floor to test! Next I thought maybe a problem with the TT itself, so tried a couple others, no change. So I figured it must be acoustic feedback, as with the TT stopped and stylus on a record, I could produce woofer pumping by tapping on certain parts of my stand...but it is also not this! I turned off my amplifier and recorded from the pre-out to a Tascam digital recorder and played that back afterwards and the pumping STILL happened! So I tried an Schiit Mani phono stage, no change in woofer pumping...I was sure it had to be my pre-amp...

So a local audiophile came over with a couple of pre-amps and we tried those. The only time the problem went away was when the subsonic filter that one had was engaged. So, I've ordered some Harrison Labs "FMODs" (20Hz high pass) to see if they will help. If they do, I may order a KAB RF1 one day...but don't want to spend that much if I don't have to.

Any other ideas on what could cause this?!

tl;dr: Woofer pumping not caused by isolation, acoustic feedback, phono/preamp or a compliance issue...what's happening?!
Click to expand...

I've owned certain speaker/amp combo's that have exhibited this and low-pass filter was required to make it stop. Added a powered sub and kept the L/P filter activated, problem solved. I think the issue relates to certain speaker, needle combo's.
 
Hajidub said:
I've owned certain speaker/amp combo's that have exhibited this and low-pass filter was required to make it stop. Added a powered sub and kept the L/P filter activated, problem solved. I think the issue relates to certain speaker, needle combo's.
Click to expand...
I think it's something like that too. I've just finished doing some more experimenting...and I think that after alllllll of this, it is just record dependent. I'm relieved, but not overly happy that it's something so simple! My Hotel California LP must be particularly bad, especially the way I was playing it with loudness on. I found that if I moved to certain records and cranked it (with loudness off of course), there was very little/no woofer pumping. I still would like to try a filter to get rid of it, just for peace of mind...but now I'm not so worried.
 
branden_8091 said:
I think it's something like that too. I've just finished doing some more experimenting...and I think that after alllllll of this, it is just record dependent. I'm relieved, but not overly happy that it's something so simple! My Hotel California LP must be particularly bad, especially the way I was playing it with loudness on. I found that if I moved to certain records and cranked it (with loudness off of course), there was very little/no woofer pumping. I still would like to try a filter to get rid of it, just for peace of mind...but now I'm not so worried.
Click to expand...

Branden I just thought of something. Through out the years of messing around with stereo crap every time I've experienced this issue it's always been a speaker with a very simple crossover setup (single phase). Just food for thought.
 
The problem is speaker related. The drive units in ported speakers have nothing to restrict their movement below the port tuning frequency. At very low frequencies the port allows the enclosure to behave as if it was completely open, so the drivers can flap about. Sealed enclosures don't exhibit woofer pumping like ported enclosures do.
 
rothwellaudio said:
The problem is speaker related. The drive units in ported speakers have nothing to restrict their movement below the port tuning frequency. At very low frequencies the port allows the enclosure to behave as if it was completely open, so the drivers can flap about. Sealed enclosures don't exhibit woofer pumping like ported enclosures do.
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My Infinitys mentioned above are sealed. Sure a ported speaker may exhibit more "flapping" but it's not restricted to this design by any means, hence the rumble/subsonic filter on vintage equipment.
 
Grenadeslio said:
My Infinitys mentioned above are sealed. Sure a ported speaker may exhibit more "flapping" but it's not restricted to this design by any means, hence the rumble/subsonic filter on vintage equipment.
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Getting rid of subsonic noise is a good idea, regardless of speakers - noise is just noise, after all. Maybe I should have said sealed enclosures don't exhibit cone flapping to the same extent ported speakers do.
 
I recently solved this issue (last week). I had a wall mounted turntable that included being mounted on vibrapods and it was chuffing like crazy at higher volumes.

Moved the turntable and problem solved. Found that the entire wall was vibrating (interior wall).
 
quadtech said:
I had the same problem with both a Dual 1229 and a SL1200. My amp is a EL34 PP tube amp and very sensitive
horn loaded speakers.
I believe the glass shelves in my audio rack were at least partly responsible.
I built a ESP project 99 DIY subsonic filter and all is good now.

https://sound-au.com/project99.htm
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That's a neat project, I could do it...but don't have the time :( I'll likely go for the KAB, unless the cheap high pass ones do the trick. The problem for me seems to be record related, and now that I've changed some stuff it only happens at higher volumes. That being said, I still want to correct it with a filter.
 
rothwellaudio said:
The drive units in ported speakers have nothing to restrict their movement below the port tuning frequency. At very low frequencies the port allows the enclosure to behave as if it was completely open, so the drivers can flap about. Sealed enclosures don't exhibit woofer pumping like ported enclosures do.
Click to expand...

Grenadeslio said:
Sure a ported speaker may exhibit more "flapping" but it's not restricted to this design by any means...
Click to expand...

rothwellaudio said:
Maybe I should have said sealed enclosures don't exhibit cone flapping to the same extent ported speakers do.
Click to expand...

quadtech said:
I built a ESP project 99 DIY subsonic filter and all is good now.
https://sound-au.com/project99.htm
Click to expand...
I took a look at the ESP page and found this:
"Not only will vented subs be completely unable to handle such a signal linearly, but sealed subs will also be stressed."
 
branden_8091 said:
That's a neat project, I could do it...but don't have the time :( I'll likely go for the KAB, unless the cheap high pass ones do the trick. The problem for me seems to be record related, and now that I've changed some stuff it only happens at higher volumes. That being said, I still want to correct it with a filter.
Click to expand...
The filter needs to be steep to be effective and inaudible.
 
gadget73 said:
Had a chance to listen to a subsonic filter over the weekend. It was audible and visual. Stopped the woofer pumping but it sucked the bottom end right out of the music. Its not a device I object to in principle but once it becomes negatively audible, no thank you.
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Definite compromise. Not sure how much this sub-sonic woofer movement shortens the foam surround life? My 15-inchers are on their second set of surrounds. Though, no detriment to their sound, once fixed. They are over 30 years old, now. :)

speakers before (small).jpg
 
gadget73 said:
Had a chance to listen to a subsonic filter over the weekend. It was audible and visual. Stopped the woofer pumping but it sucked the bottom end right out of the music. Its not a device I object to in principle but once it becomes negatively audible, no thank you.
Click to expand...
I have no idea what the specs of the unit you used were, but to be effective and inaudible the roll-off needs to start low, say 20Hz, and then roll off very steeply at 18 or 24dB per octave. If the roll-off starts too high it will be audible and if the filter slope is't steep enough it won't be effective.
 
yeah I don't know either. It was whatever was in the Luxman we were listening to. Just a quick on/off test and I didn't care for the results. Its on a piece of gear I'm not likely to own, so the specifics don't really matter all that much. I wouldn't judge all of them from a small sample size, I just didn't happen to like that specific one.

Doubt woofer pumping has much effect on surrounds. That looks more like typical old age failure to me.
 
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