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Old 19th November 2011, 11:17 AM   #1
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Default help Pensil 12 with strong 53Hz resonance

Hi, i have bild a pensil 12 and I am verry happy with it. But, after a week of 4 I noticed a peak at 52 / 53 Hz. I can see that the surface of the cone also vibriting more than normal.
I build the enclosure within 2 mm. Is this normal or is it something to do with the filling or damping?
Joost.
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Old 19th November 2011, 03:56 PM   #2
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Before going to the effort of changing the stuffing in the boxes, it might be worth it to try moving the boxes to a different room location. Moving the boxes less than 1 meter may make a big difference.

In the end, you will probably need to adjust the stuffing to address the excessive cone movement. Have you checked your turntable to make sure there isn't any feedback or vibration getting through to the record surface?
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Old 19th November 2011, 07:27 PM   #3
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Hi Joost,
Hope you (and the good lady) are well.

Member silverhairbp maybe right about the feedback from the Turntable, or possible room effect. There should be very little cone movement for most music on this driver/box combination. How much damping material do you have in the boxes?

In the meantime, make sure not to over-load the drivers. From memory, your room is large and also the speakers go outside?

Can you post some pics of the inside of the box, your room and set-up? This could help.

Thanks
Mark.
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Old 20th November 2011, 07:12 AM   #4
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Hi Silver and Mark,
Thanks for your reactions. As you see I put some pictures with. The filling is as recomended, Behind the driver empty, the most of the filling under and above the driver and the bottom opening.
I do not use a turntable as you can see. (bussy looking for a decent cd player, the old maratz tube player is just cone to haven)
Even oudside there is the resonance, I calculated the wave length of 51/52 Hz = about 6.6 mtr. The room is 3.7 W x 7.7 L x 2.6mtr H so I don't see here a problem.
The one thing I can think of is that the power supply is 230V/50Hz. But then I must hear it when I don't play anything...

Mark, Caroline is verry well and she hope's that you still intending to come over...
Joost.
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Old 20th November 2011, 07:51 AM   #5
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I would 1st eliminate the input to the speakers. Your resonance is very near the modeled system tuning. Minimum motion point.

dave
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Old 20th November 2011, 08:41 AM   #6
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Hi Joost,
The build looks very nice. Like the colour!

Dave's suggestion is well worth trying. Are you getting/measuring a constant signal @ 53Hz? Or is it only in some music?

I've posted a copy of your pic:

1 - Recommend you round off the edges on this brace. Ideally, a round brace would be better since its immediately behind the driver. I've found bracing so close to the driver of this size and having a rectangular profile facing the driver, can sometimes cause reflection.

2 - Similarly, round off the edges on these braces. Some sanding paper should be OK.

Can you send a pic of the cabinet with the back open so we can see the damping?

Say "hi" to Caroline for me.

Cheers
Mark.
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Old 21st November 2011, 08:18 AM   #7
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Hi Mark, after new year I will open de box and will do some sanding. Now i am too bussy.
First I sounded like if there was a kind of loudness on, specialy in the bass. Then I used a test cd with frequeties from 20 till 500Hz. On this way I found out that it was arround 52Hz.
I did already some extra filling behind the units and this made a difference..
Oke, I will contact you again after new year, stay healthy Joost.
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Old 21st November 2011, 04:31 PM   #8
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my 2 cents worth:

More bracing, in the form of interlocking vertically oriented panels could significantly mitigate enclosure wall resonance issues - I'd pay particular attention to more rigid coupling the removable rear panel to front.

At the cited frequencies damping fill levels will have likely less affect than cabinet integrity derived from bracing.
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