4311B woofer constantly "flapping"

[nee]

When my 4311Bs are connected to the amp and the amp is on, both woofers are moving when no signal is applied and the volume is down - maybe 10-12 cycles per second. One of the woofers moves so much I would call it flapping - really quite a large excursion.

If I plug the ports then the flapping stops.

If I swap channels it's the same speaker that flaps. I know I need to try them with a different amp, but has anyone come across this kind of thing?

IanG

[1audiohack]

I have seen a couple of "unstable" amps do that. I have a GTI1800 that has the suspension absolutely socked out from that. Don't wait for it to kill something, get it out of your system and repair or replace it.

[jcrobso]

When my 4311Bs are connected to the amp and the amp is on, both woofers are moving when no signal is applied and the volume is down - maybe 10-12 cycles per second. One of the woofers moves so much I would call it flapping - really quite a large excursion.

If I plug the ports then the flapping stops.

If I swap channels it's the same speaker that flaps. I know I need to try them with a different amp, but has anyone come across this kind of thing?

IanG

The amp is oscillating with the speaker load, this is a dangerous thing, lots of power is going to the woofers, get a different amp ASAP!!

[Beowulf57]

Heed the warnings...this used to be called "motorboating" as in a low frequency oscillation/instability in an amplifier circuit: "Putt, putt, putt, putt."

[webmonkey]

You can try connecting a 20 Ohm 10 Watt resistor across the speaker terminals, if the oscillation stops,leave the resistor in place. Reflex systems can exhibit a large impedance peak at a very low frequency, plugging the port removes the lower peak. This was very common in Fisher Amps of the late 1960's. Best to replace the amp if possible.

[pyonc]

When my 4311Bs are connected to the amp and the amp is on, both woofers are moving when no signal is applied and the volume is down - maybe 10-12 cycles per second. One of the woofers moves so much I would call it flapping - really quite a large excursion.

If I plug the ports then the flapping stops.

If I swap channels it's the same speaker that flaps. I know I need to try them with a different amp, but has anyone come across this kind of thing?

IanG

Hi,

I have the 4311B, too.
When I play CD, there is no "flapping" on the woofers even at noon volumn, but when I play LP, the woofers start to flap from 11 o'clock volume. I've no idea why. I play 4311B with a Marantz receiver.

[BMWCCA]

I have the 4311B, too.
When I play CD, there is no "flapping" on the woofers even at noon volumn, but when I play LP, the woofers start to flap from 11 o'clock volume. I've no idea why.

Turntable rumble? :dont-know

[pyonc]

Turntable rumble? :dont-know

Nope! Turntable stands tight on a wood stand.
When I push the 'Loudness' button on the Marantz receiver, though,
I see the woofers starting to flap from around 11 o'clock volumn when I play LPs. But, I don't see that happen at all when I play CD.

[Robh3606]

It's not rumble at all it's acoustic feedback from the bass boost of the loudness switch. Either move the turtable or lay off the loudness switch. You should only be using it at low voulme. All you are doing is wasting all your amps headroom and that could be part of the reason why you are have issues with how the 4343 sound in your other thread.

Rob

http://en.wikipedia.org/wiki/Loudness

[pyonc]

It's not rumble at all it's acoustic feedback from the bass boost of the loudness switch. Either move the turtable or lay off the loudness switch. You should only be using it at low voulme. All you are doing is wasting all your amps headroom and that could be part of the reason why you are have issues with how the 4343 sound in your other thread.

Rob

http://en.wikipedia.org/wiki/Loudness

Thanks. Actually I don't turn on the Loudness button when I play CD or LP because of this issue...

[herki the cat]

& [pyonc ] & [IanG ] =My 4311B's connected to the amp, with no signal, & volume controis down = One woofers moves maybe 10-12 cycles per second - really quite a large excursion. If I plug the ports the flapping stops. nee283769, pyonc & IanG.

[quote=BMWCCA;285188]Turntable rumble? :dont-know[/quote]

& this circuit should be just about perfect for you. It is tuned for 17 Hz to provide a rumble filter, but you can change it easily if you need to.Loren42

Member nee; It was mentioned in this thread, "cone flapping does not occur playing CD's" which confirms BMWCCA suggestion "turntable rumble" __read: "a Turntable rumble filter is in order". To that end. Member Loren42;283351 is fixing his cone "flapping" & "slamming" with an excellent high pass filter at his power amplifier input, to wit: >Click this button= < This circuit should be just about perfect for you.

Also with due respect for the other excellent posts regarding amplifier instability & susceptibility to "speaker enclosure Ports , amplifier motor boating, & speaker low frequency impedance aberrations", and other instabilities primed to flare up etc suggesting the need for a better, more stable power amplifier before ALHBL="all hell breaks loose." = very cogent advice.

Bonne Chance, herki the cat

[JBL 4645]

Maybe a video would help us see what is happening.

Flapping :dont-know

I want to see the video without excuses no later than today 6pm UK time. So chop, chop get to it and may the flapping be with you.

you now have "flipping" 28 minutes till 6:00pm UK time that's 18:00 hours for all those who can't tell time.