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Old 1st June 2008, 09:15 AM   #1
wixy is offline wixy  Australia
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Default Excessive FE206E cone movement

When playing vinyl through my FE206E's i've noticed that the speaker cones move far more excessively than when playing cd's.

Please see video here: http://www.yourfilelink.com/get.php?fid=464248

Is this likely to damage my FE206E's?
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Old 1st June 2008, 10:48 AM   #2
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What cabinet design do you use ?

When listening to Vinyl, there is very much subsonic
signal ( i think 'rumble' is the english word ) caused
by the record/turntable system.

This is because the record is crimped and excentric,
because the pickups reacts on external vibration
in your house and so on ...

Tonearm and and pickup have a subsonic resonant
frequency which is excited by that mechanism.

An open cabinet like Bass Reflex or Transmission Line
has no reset force for the driver at subsonic freq., which
causes high excursion.

Of cause this may damage your driver, when listening
too loud. Too much unwanted subsonic excursion also
decreases the dynamic headroom of your system and
potentially the sound quality.

In unlucky cases some subsonic resonant frequency of
the speaker and the resonance of the turntable are
close together or the same.

A closed box is more benign concerning rumble, but the
problem occurs anyway.

There are two ways to go and they should be combined:

1) Keep rumble as low as possible.
- use methods for decrimping the records (vacuum, weights ...)
- use a well damped tonearm/pickup system
- isolate your turntable from footfall sound

2) Use a subsonic filter.
If your preamp hasn't got one use an
external one, with high steepness (24db/Octave or more)

But even a Passive Line Level Filter should impove the
situation. You can build one easily, google for PLLXO.
But you cannot achieve steepnes over 12dB/Octave using that.

The cutoff frequency of the subsonic filter should be tuned to
come below the cutoff of your speakers. Say e.g.
0.5 ... 0.7 * fs ( -3dB speaker cutoff frequency)
This way you attenuate rumble as much as possible, while
maintaining the lower bass notes your speaker is able to
produce.


Regards Oliver
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Old 4th June 2008, 04:55 PM   #3
badman is offline badman  United States
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Default For subsonic filtration, Harrison Labs

A company named Harrison Labs has a large number of passive and active filters for high-pass (rumble) filtration. The products which I've used of theirs have been excellent.
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Old 5th June 2008, 02:22 PM   #4
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Default Re: Excessive FE206E cone movement

Quote:
Originally posted by wixy Is this likely to damage my FE206E's?[/B]
Eek, yes -- the cone on that particular driver should only travel 1.5mm (xmax = maximum excursion). Guessing from the video, it's moving out at least a centimeter.

Does it not sound terrible as well? No doubt the LF is inaudible but how can the driver make those sweet mids and highs when the cone has to swing so far out of the zone, and then return again? Hey, is this a joke by any chance?!
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Old 5th June 2008, 02:55 PM   #5
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Xmax is only linear excursion, i.e. how far the driver will travel before distortion / compression sets in.

Whatever, you're unlikely to physically damage one of these units. AFAIK, due to the nature of their VC & suspension you simply can't drive them to Xsus under realistic conditions, so they won't bottom out. If you pump sufficient power into them you might burn out a VC, but that's not at all an easy task -they can take a lot of punishment.

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Old 5th June 2008, 04:48 PM   #6
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Quote:
Originally posted by Scottmoose Xmax is only linear excursion, i.e. how far the driver will travel before distortion / compression sets in... you're unlikely to physically damage one of these units...
My apologies, gentlemen. So exceeding Xmax means distortion, not damage. I see I still have much to learn. I guess I'm prone to panic. As inept as I am, it's good to know I have drivers that can take some (unintentional) punishment.
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Old 5th June 2008, 05:01 PM   #7
badman is offline badman  United States
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Default Re: Re: Excessive FE206E cone movement

Quote:
Originally posted by rjbond3rd


Eek, yes -- the cone on that particular driver should only travel 1.5mm (xmax = maximum excursion). Guessing from the video, it's moving out at least a centimeter.

Does it not sound terrible as well? No doubt the LF is inaudible but how can the driver make those sweet mids and highs when the cone has to swing so far out of the zone, and then return again? Hey, is this a joke by any chance?!

Exactly, it can't. Driving it out of the gap increases distortion pretty dramatically. A good metric for sufficient displacement of a speaker system is, "Can it go as loud as I listen without visible cone excursion?" Dramatic metric to be sure, and requires a LOT of subwoofer if you're running deep bass, but it's about the surest way to make sure you're operating in the happy zone. This method is best used with high Qms drivers, which tend to sound better at tiny excursions. Call it memory effect if you like, it's just my preference.

Anyway, check out the harrison labs devices. In a tuned cab, not a lot of reason to allow input signal any more than half an octave below tuning.
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