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Cone travel one way more than the other
Cone travel one way more than the other
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Old 5th November 2019, 12:26 PM   #1
Augusts is offline Augusts  Latvia
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Default Cone travel one way more than the other

Hello

The device under test is Eminence Lab12c. It has been recoiled.

When I test the speaker on free air feeding it a sine wave signal at 30hz, everything is as should be - the cone moves an even distance both ways and starts to scream for help when movement reaches 13mm one way as this is the xmax.

But when I feed it a mastered track that has a rhythm and a bassline the cone moves one way a whole lot more than the other (about 13mm inward vs 5 outward). I tried cutting off the lower frequencies, I went until a bandpass region of 55-100hz. The amp is not clipping.

Why do I have this question is because, the speaker was in a TL enclosure and the sub freqencies sounded nice and could hold the power they are supposed to but at 60Hz up where the kick bass starts to play the speaker started to rattle. So I took it out for a test and this is what I saw.
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Old 5th November 2019, 12:39 PM   #2
Brian Steele is offline Brian Steele  Grenada
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Swap the leads connected to the speaker. Does the situation reverse, i.e. does the driver show more outward than inward movement?
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Old 5th November 2019, 12:54 PM   #3
Augusts is offline Augusts  Latvia
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Hi

I tried swapping the polarity, it does not change. A lot more inward than outward.
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Old 5th November 2019, 01:19 PM   #4
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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What kind of baffle/cabinet are you using? Or it is at free air?
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Old 5th November 2019, 04:51 PM   #5
whgeiger is offline whgeiger  United States
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Compliance at the zero point is quite large. Its is like a teetertoter when the moving system is undergoing large oscillations; i.e., the zero point will shift due to any small directional difference in suspension elasticity. Any DC offset in the driving signal will also influence this behavior as well. WHG
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Old 5th November 2019, 07:14 PM   #6
Xoc1 is offline Xoc1  United Kingdom
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When the speaker is in free air the resistance to movement will be minimal. When the speaker is in the cabinet the loading on the driver will be greater. You stated that the driver has been rewound.
Are you sure the driver coil has been fitted at the correct height?
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Old 5th November 2019, 09:08 PM   #7
freddi is offline freddi  United States
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Cone travel one way more than the other
"port rectification" can cause the effect.
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Old 6th November 2019, 03:27 AM   #8
whgeiger is offline whgeiger  United States
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Quote:
Originally Posted by whgeiger View Post
Compliance at the zero point is quite large. Its is like a teetertoter when the moving system is undergoing large oscillations; i.e., the zero point will shift due to any small directional difference in suspension elasticity. Any DC offset in the driving signal will also influence this behavior as well. WHG
See Attached Article. WHG
Attached Files
File Type: pdf DC displacement.pdf (341.6 KB, 28 views)
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Old 6th November 2019, 09:22 PM   #9
tonskulus is offline tonskulus  Finland
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Sometimes I have noticed the same, cone is moving more inwards at some frequencies (especially in ported enclosures and some tapped horns etc). This sympton may actually lead to spider/suspension sagging.

Any good solutions for that "port rectification"? could not find any documents..
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Old 7th November 2019, 04:54 AM   #10
whgeiger is offline whgeiger  United States
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Thumbs up Don't use ports.

For clean, deep bass at home, use a sealed enclosure and servo control. Use multiple units as well. WHG
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