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PSD 2002 modifications [message #41865]

Thu, 10 July 2003 08:24

Adam
Messages: 419
Registered: May 2009

Illuminati (1st Degree)

Hey guys,

I had a bit of an experiment I wanted some comments on... I have owned a lot of PSD 2002's and one thing that has always irked me about them is that rear chamber. It's tiny and it's reflective. I can only imagine how many frequencies are being bounced around in that rear chamber, causing smearing, frequency response spikes and who knows what else.

Would there be any positive results from building a damping chamber onto the rear of PSD-2002's to obsorbe and diffuse the rear waves from the compression diaphram? My car horn compression drivers have such a chamber on them and it seems to work pretty well... thoughts?

Adam

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Re: PSD 2002 modifications [message #41869 is a reply to message #41865]

Thu, 10 July 2003 09:50

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

I'd fire this question off to the folks at Eminence. You'd be surprised how unassuming they are and how willing they are to discuss matters like these. For example, I asked about ferrofluid treatment of the PSD2002 and they told me that the stuff evaporated but that they had, in fact, done comparitive testing of their drivers with and without ferrofluid.

So they may very well have measured a PSD2002 (or an earlier model) with the back cover removed to see how much effect there is. And honestly, I would expect this from them in order to confirm the response with the system having its specific back chamber volume.

If you do write to them, I encourage you to tell us what they say.

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Huh? [message #41873 is a reply to message #41869]

Thu, 10 July 2003 10:06

mollecon
Messages: 203
Registered: May 2009

Master

Quote:

"..I asked about ferrofluid treatment of the PSD2002 and they told me that the stuff evaporated.."

Argh! I need to check my old, trusted D28's now...

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Re: PSD 2002 modifications [message #41874 is a reply to message #41869]

Thu, 10 July 2003 10:46

Adam
Messages: 419
Registered: May 2009

Illuminati (1st Degree)

Thanks dude... I'll shoot them an e-mail now.

Adam

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Ferrofluid [message #41875 is a reply to message #41873]

Thu, 10 July 2003 10:50

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

The issue with the PSD2002's is that the areas around the voice coil aren't sealed. Following is the reply made by an Eminence designer when asked specifically about using ferrofluid with their PSD2002 compression driver:

"We have experimented with FerroFluid many times and always come to the same conclusions: it is not for us. It has some advantages, but we feel the disadvantages outweigh them. It does help raise the power handling a bit, but not dramatically. The downsides are it is messy, it is expensive, and it evaporates over time turning into a thick sludge. Not a pretty thing."

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Reply from Eminence [message #41879 is a reply to message #41869]

Thu, 10 July 2003 16:37

Adam
Messages: 419
Registered: May 2009

Illuminati (1st Degree)

"Adam,

According to one of our design engineers, in theory, the back volume should change the response, but our experiments have indicated that doubling or tripling this volume made little difference in the response. If you choose to pursue this, we would, of course, be interested in any results confirming or contradicting this...

Charlotte"

I will probably build a test unit. It's too bad I don't have a concrete way of measuring it.

Adam

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Thx Wayne [message #41880 is a reply to message #41875]

Thu, 10 July 2003 16:57

mollecon
Messages: 203
Registered: May 2009

Master

I guess it's the lack of sealing that makes it possible for the fluid to evaporate when the unit is driven hard - the D28's aren't build that way! :-)

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rear chamber access [message #41881 is a reply to message #41879]

Thu, 10 July 2003 18:01

ToFo
Messages: 219
Registered: May 2009

Master

Adam,
I have been wanting to experiment here as well. I assume from looking at the diaphragms (and the sturdy glue around the surround) that the only rear chamber access is to carefully cut off the back cap, leaving enough cylinder to attach the new chamber. If you know, or discover a cleaner and easier method, please ellaborate. (not that it would be bad that way, just pondering the best approach)
Thanks,
Thomas F.

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Re: rear chamber access [message #41882 is a reply to message #41881]

Thu, 10 July 2003 18:54

Adam
Messages: 419
Registered: May 2009

Illuminati (1st Degree)

I haven't messed with it much yet, but it occurs to me that a soldering iron with a melting tip would be good approach. Not as difficult to handle, probably give you a cleaner edge or as clean and if you happened to make contact with the diaphram by accident, you wouldn't do any damage as long as you didn't hold it there for a long time... Whereas with a cutting blade or whatever, you're screwed!!

Just a thought.

Adam

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