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Old 24th March 2012, 05:29 PM   #1
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Default phase-plugging

so i've gotten around to removing the dustcap on my guinea pig drivers.

there's still a few rough bits on the edges, is this a problem or should i smooth it off?

there's a very slight lip between the main cone and the whizzer, is this a problem or should i try and get it plush?

a bottle of vits makes the perfect fit into the voice coil thinger, does anything need to be changed to make the phase plug fit closer to the whizzer cone, there's a lot of messy cone area.

thanks for your help

p.s sorry for the picture size.

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Old 24th March 2012, 05:49 PM   #2
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Was the dust cap made of a porous material? ...one that would allow air movement?
I ask as it appears the pole piece is vented through the small screen. If that is the case I would be inclined to maintain some freedom for air movement.
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Old 24th March 2012, 05:53 PM   #3
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Originally Posted by Ed LaFontaine View Post
Was the dust cap made of a porous material? ...one that would allow air movement?
I ask as it appears the pole piece is vented through the small screen. If that is the case I would be inclined to maintain some freedom for air movement.
same material as the cone, looked to be pressed paper - listed as paper on the spec sheets.

trying to blow air through it now, i can't.

would i need to make some kind of hollow phase plug?
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Old 24th March 2012, 05:56 PM   #4
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Hold the driver such that the opening is facing downwards and take a bit of 150-200 grit sandpaper to clean up the rough edges. Don't be fanatical about getting the ridge flat -- your whizzer could come off.

The gap should be small, but not so small that there is contact as the driver moves...

dave
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Old 24th March 2012, 05:59 PM   #5
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Quote:
Originally Posted by Ed LaFontaine View Post
I ask as it appears the pole piece is vented through the small screen. If that is the case I would be inclined to maintain some freedom for air movement.
You might want to leave a bit larger gap for cooling, but i feel covering up the pole piece vent will give a sonic improvement.

If the vitamin bottle is to be used, it should get filled with something... the other issue is how it willbe attached?

dave
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Old 24th March 2012, 06:09 PM   #6
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You might want to leave a bit larger gap for cooling, but i feel covering up the pole piece vent will give a sonic improvement.

If the vitamin bottle is to be used, it should get filled with something... the other issue is how it willbe attached?

dave
i will carve a phase plug from wood, this is just playing around with the size etc, comparison with the vanilla driver.

the next question was going to be about the best shape? teardrop? also the overall height of the phase plug, equal to the whizzer? or is the bullet shape the best way to go?

attachment is usually just magnetic no? if not i'm open to wisdom.

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Old 24th March 2012, 06:39 PM   #7
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I use a turned walnut bullet shape with a 1mm ish gap around the edge on my 12LTA's. Two screws in the base and the magnet does the rest. Never managed to move them even when playing at high volumes.
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Old 24th March 2012, 06:55 PM   #8
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The bullet shape is known good, you can play to your heart's content. 1/2-1 mm gap is good, my plugs have 4 small screws.

Plug should poke out just over the top of the whizzer as a starting point.

dave
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Old 24th March 2012, 11:01 PM   #9
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just given it a little play, they seem to sound better with no dustcap. not sure how to describe the change in sound. they seem less fatiguing, smother i guess. at the same time vocals and other things seem to have been brought forward in the sound. i don't think any of the highend has been lost, just moved behind other parts of the sound which gives a more pleasing sound. lowered the SPL of the upper regions?

using the make shift phase-plug doesn't seem to immediately make any change in sound. typically what does a phase plug tend to do?

how long does it usually take to sand down the nub from the dustcap? i'm being fairly careful but the paper cone seems surprisingly tough for such a thin thing. so there's still a fairly pronounced bump and lip which could be interfering with sound?
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Old 25th March 2012, 04:02 AM   #10
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Originally Posted by gafhenderson View Post
how long does it usually take to sand down the nub from the dustcap? i'm being fairly careful but the paper cone seems surprisingly tough for such a thin thing. so there's still a fairly pronounced bump and lip which could be interfering with sound?
A couple minutes... very often with a whizzer there will be a discontinuity where the whizzer attaches... just make it smooth.

dave
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