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Old 20th March 2005, 03:25 PM   #1
watou is offline watou  United States
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Default shielded subs or passive radiators?

Hello friendly 'philes, I am currently on a hunt for a shielded subwoofer or passive radiator (I think that's what they're called) to be instaled inside a video arcade cabinet. I'm actually only looking for a device that will rumble at frequencies < 100Hz.

I have the amp and a subwoofer already, but the sub is not magnetically shielded and it has to me mounted too near a CRT and other electronics. And because it doesn't need to move air, just shake the cabinet, it doesn't need a cone, just a voice coil. (Please correct me if my terminology is off.)

Many, many thanks for suggestions of where I can find such a 4-Ohm, shielded, approx 5 1/2" diameter subwoofer or passive radiator for this purpose.
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Old 20th March 2005, 06:01 PM   #2
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watou,

Let me take a stab at this.

1) Look for shielded woofers at the PE site or wherever you buy raw drivers from.

2) A passive radiator is a drone cone with no coil or magnet. It is used to recover some of the bass from within the cabinet similar to a bass reflex but instead of a port, is uses something resembling a partial speaker. This drone is usually larger than the actual woofer. No wires are connected to it.

Your quote:

"And because it doesn't need to move air, just shake the cabinet, it doesn't need a cone, just a voice coil."

This is confusing. It sounds as though you are looking for a bass shaker not a woofer. Please elaborate.

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Old 20th March 2005, 11:46 PM   #3
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I think what you really want is a Tactile transducer.
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Old 21st March 2005, 07:27 AM   #4
watou is offline watou  United States
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Quote:
2) A passive radiator is a drone cone with no coil or magnet. It is used to recover some of the bass from within the cabinet similar to a bass reflex but instead of a port, is uses something resembling a partial speaker. This drone is usually larger than the actual woofer. No wires are connected to it.
Obviously I have the terminology wrong. Thank you for explaining that.

Quote:
This is confusing. It sounds as though you are looking for a bass shaker not a woofer. Please elaborate.
I didn't even know the term "bass shaker"! It certainly sounds more like what I'm after.

Essentially, I'm building a video arcade machine in the form of an enclosed cocktail table, and I want to route the low frequencies into rumbling from within the table. I have a 2.1 computer speaker setup which routes frequencies below 100Hz to the subwoofer, and two two-way speakers for the rest. The subwoofer did its job decently as a subwoofer in a ported box, but reusing it in this application has two problems:
  • it has a giant, unshielded magnet that would wreak havoc on the CRT and electronics inside the cabinet
  • there is no reason to move air with a cone inside the cabinet -- I just want the cabinet to rumble from frequencies <= 100Hz.
What would be the ideal driver for this application? Many thanks in advance for suggestions.

-- watou
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Old 21st March 2005, 07:27 AM   #5
watou is offline watou  United States
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Quote:
I think what you really want is a Tactile transducer.
Is a tactile transducer another way of saying bass shaker?

Does anyone make a relatively inexpensive one of these that is already magnetically shielded? I would rather avoid the procedure of shielding one myself, due to cost and the potential of doing so inadequately.

Thanks for your helpful advice!
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Old 21st March 2005, 04:09 PM   #6
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This PE page shows them. It doesn't say anything about shielded. I would contact them by phone and speak with their techies.

http://www.partsexpress.com/webpage....7&WebPage_ID=3

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Old 21st March 2005, 04:11 PM   #7
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Well, since that link doesn't seem to work, go there anyway and input "bass shaker" into the search keyword. You will get both shakers and tactiles.

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Old 21st March 2005, 08:23 PM   #8
watou is offline watou  United States
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Cal, thank you for your replies. I have contacted PE regarding bass shaker shielding and I await their reply.

If I were to construct my own shielding, what is the superior alloy that should be used to enclosed the magnets?

Is it generally available as a construction material or does one have to go through a specialty source to obtain it?
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Old 21st March 2005, 08:50 PM   #9
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