Help needed with utterly bizarre sound problem

[Dudgeman]

So rehearsing tonight in a very well equipped rehearsal room. Every time I hit a low E one of the wall mounted pa speakers made a bizzare stuttering sound...The owner and ourselves wondered if any of you guys could help explain it. So no other frequency set it off...just high E or low E... we thought it might be a weird ground loop so we turned the speaker down....still did it ..so we unplugged it..it still did it....totally disconnected it still did it... it was a very audible sound...not a rattle ...

Owner dismantled the speaker and one of the soldered connections had come loose to the speaker...but it still doesn't explain how a completely passive disconnected speaker makes sound based on the frequency of an E note..

 

Can anyone explain how this happens...it had us all stumped...cheers

[Kevsy71]

I'm guessing it was a resonant frequency if it was only E - causing the speaker to oscillate at its natural frequency. But over to the experts!

[MoonBassAlpha]

Yeah it's not beyond the realms of possibility that the speaker would have a resonant frequency of  ~82 Hz if it's not a specialist bass speaker.

[Dudgeman]

So it is possible for the speaker to make sound just from the effect of frequency of an E note? High or low ? Just because the speaker is in the room....how freaky is that! 

[MoonBassAlpha]

I'm wondering if the voice coil is distorted and rubbing on the magnet as the cone resonates? Unless the speaker has an obvious tear in it, it's hard to see how else it could make a noise under passive resonance.

[Dudgeman]

No tear in the speaker.....the only thing that was wrong was the defectective soldering on the cable to the speaker that had come loose... it really was most bizzare and would love to know the science behind it. 

[leemarseillebass]

The above comments sound about right. I’m no expert but if you imagine a port is shaped differently for each speaker cabinet be it PA, home audio - it’s there because when a sine wave is fed through it there’s likely to be a point where everything goes mental and it’s a bit like our ‘brown note’ (allegedly)

[bazzbass]

Blue note, Brown note, let's face it, we have the POWER

[Dudgeman]

I like the fact that, despite some awesome musicians in my band,  it is only the bassist that can can summon the sound demon through witchcraft and magic... maybe its not science after all..... bass ruuuuules.! 

[SubsonicSimpleton]

In most smaller rooms, bass frequencies are not distributed evenly

https://en.wikipedia.org/wiki/Room_modes

Causes some pretty extreme effects in some rooms.

 

[Dad3353]

The use of passive radiator speakers is (or was, back then...) quite common in high-end hifi systems, and the isobaric cabs (Orange, I believe, and a few others...) use 'em, too. Normally, a speaker's cone is braked by the connection to the amp, but when unplugged (or, it would appear in this case, disconnected...), that brake is no longer, and the cone becomes free to resonate with any passing frequencies. I'd suggest that this could explain the cone movement, and the sound emanating from the unit. The speaker has become a passive radiator, resonating at a specific frequency (or its harmonic...) that happens to be audible.

...

Or ghosts, of course. 

[Dudgeman]

That's a great explanation  ....thanks. I knew it was ghosts all along!