What causes speaker cones to visibly vibrate badly?

Ok, so needle hitting vinyl with a thump you’ll see the excursion easily but some albums give far worse effects than others - ‘rumble’/‘wow’ or similar?

Bafflingly my question doesn’t really relate to analogue but something I noticed with an HD download which I assume has some similar sonic characteristics. (Estrons)

It’s something that can usually happen most with vinyl, particularly where the low frequency resonance of the arm/cart combination falls within the audio band, usually as a result of a compliance mismatch. The vinyl itself can exacerbate things, as can any additional LF noise from motor or bearing (commonly known as “rumble”), as the equalisation to bring back the correct level of low frequencies also greatly amplifies any existing LF issues. It’s why a LF filter or a steeper and earlier LF rolloff is sometimes preferred - this is where the IEC made amendments to the original RIAA curve. An amplifier and the speakers have to work really hard to reproduce this, for little or no sonic gain - and indeed, by having to work so hard, there’s usually a sonic penalty, hence why an earlier rolling off of the extreme LF is often quite a good idea.

An HD download may have something similar happening at very low frequency - especially if it’s an HD ‘vinyl rip’…


Thanks for the detailed response Richard.

Just wondering if these low frequency effects just happen to be quite low frequency hence why they are visible to the naked eye? Or perhaps some kind of summation effects.

I’ve seen speaker cones doing some really rather alarming excursions - often looking like they’re wobbling like a pistonic jelly. The really weird bit is that sometimes the frequency is so low you don’t actually hear much of it.

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Yes I’ve seen that too - quite worrying - maybe that’s a good enough reason alone to stick the acoustic foam on!

I have seen exactly this happen during a dealer demonstration of a vinyl system that was installed on a Hifi Racks rack (as it were) in a room with a wooden beam floor.

The very low bass was coming out of the speakers, making the floor boards sing along, sending the vibration up through the racking and into the turntable. The cartridge was beautifully isolated from all this by the high quality tonearm, so the stylus was led a merry bass dance by the record on the turntable’s platter. The speakers’ bass cones wobbled quite alarmingly, moving in and out by a good 10mm or more.

Short of installing a low bass filter in the phono stage, the only vinyl alternative was to get the turntable on to a wall shelf.

I had to get rid of my 2m black on my lp12 as it made the speakers go mad quite often
Bought a Hana sh and never did it again …plus it sounded better too

I had the problem with excessive woofer excursion and it was twofold. One was inadequate turntable isolation, even though I use a wall shelf. I solved that part by replacing the spiked feet of my turntable with isolation pucks (HRS Nimbus, isoAcoustics Orea also work). Secondly, the Clearaudio Magnify tonearm I had uses magnetic bearings and that was causing excessive LF feedback. I upgraded to the Universal tonearm, which uses mechanical ball bearings, and that resolved the issue entirely. Now I can play whatever I want as loud as I want and the speaker bass drivers and subs are very stable.

I also use icoAcoustic Gaia II isolators in place of spikes on the speakers.

My old Epos ES14s cone-flapped a treat. I had an Audiolab PPA phono stage with a subsonic filter which tamed the old flappery - not sure if it did much in terms of SQ though!

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Loud music?

No, very specific albums generally and not always played loud.

So it is in a sense low frequency feedback

Same speakers!

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