Plessy midrange by Foster

Moondog55 · 03:22 AM

Just picked these up as I thought they were the correct midrange for a mates rebuild, now I'm not so sure as he hasn't given me the original boxes and I am totally in the dark as to whether the old boxes are Sansui or something else.

Would anyone have the approximate parameters for these little 130mm wide flange integrated enclosure midrange drivers??
Black surround white paper cone and a black plastic compartment 120mmDia * 120mm deep
Only marking on the back are Plessey by Foster' Japan
130M08
8R 20 watt

and down the bottom 0648

Actually all I really need is the approximate Fs to work out if they will work in the original XO when I get the boxes.

Sound OK, quite loud and a little bright when played full range

Moondog55 · 21st July 2011, 03:24 AM

Pictures disappeared here they are

Moondog55 · 21st July 2011, 09:00 PM

The very hard flat dust cap reminds me of another driver range, Bump??

sreten · 01:35 AM

Hi, surely the impedance peak is easy to measure for Fs / Fb ?, rgds, sreten.

I'd hazard a guess its relatively low, as the chamber is relatively large for
such types and probably far lower than an enclosed type if original fitted.
(Enclosed = sealed frame, no seperate enclosure, the most common.)

Moondog55 · 22nd July 2011, 01:40 AM

Sreten you are right as almost always but I have lost all my stuff in the pile of renovation rubbish and building materials, I can't even find my multimeter at the moment.
SWMBOs bathroom takes precedence over speakers.
I'd be happy with anything lower than 200Hz, but I think the very stiff surround means it may be a bit higher.
Still haven't got the boxes I promised to look at, these may drop in they may need work, but it is a swap for building work so they need to be a little better tan just OK when finished

sreten · 02:04 AM

Hmmm......

The separate cup looks quite deep to me, I'd say Fb is likely < 200Hz.
Maybe Vcup is a lot bigger than Vas if the driver has stiff suspension,
but then the question is why the depth / volume of the cup ?

Will you get the original mid drivers (bust or not) ? Cone
tapping should quickly illustrate the relative Fs's or Fb's.

rgds, sreten.

Moondog55 · 22nd July 2011, 03:14 AM

Maybe, I certainly hope so.
Although the last pair of "broken and useless s*** " speakers I was given were fixed in 30 seconds with a soldering iron and sounded quite good when a little poly was added to the box. At the moment I don't even know if the woofers are 12 or 15 all I know is that they are ::"HUGE" :: which in todays world of mini surround systems means anything larger than about 6inches

Moondog55 · 22nd July 2011, 03:15 AM

Volume is 1'3 liters which is as you say reasonable

PeteMcK · 22nd July 2011, 05:11 AM

Hi Moondog, IIRC, the Foster units were part of Plessy's last stand before they dissappeared from downunder; perhaps a search of old EA mags (~ late 70's?) if you can track them down in a local library may have a project that used these units?? (Sounds like you're a bit busy for that though... :-)

Moondog55 · 22nd July 2011, 07:14 AM

G'Day Pete
Only said yes to the rebuild because the mate is a carpenter and he will reciprocate in kind.

21st July 2011, 09:00 PM	#3
Moondog55 diyAudio Member Join Date: Jun 2007 Location: Norlane; Geelong: Victoria: Australia	The very hard flat dust cap reminds me of another driver range, Bump?? __________________ QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"

22nd July 2011, 01:32 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, surely the impedance peak is easy to measure for Fs / Fb ?, rgds, sreten. I'd hazard a guess its relatively low, as the chamber is relatively large for such types and probably far lower than an enclosed type if original fitted. (Enclosed = sealed frame, no seperate enclosure, the most common.) __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow Last edited by sreten; 22nd July 2011 at 01:35 AM.

22nd July 2011, 01:40 AM	#5
Moondog55 diyAudio Member Join Date: Jun 2007 Location: Norlane; Geelong: Victoria: Australia	Sreten you are right as almost always but I have lost all my stuff in the pile of renovation rubbish and building materials, I can't even find my multimeter at the moment. SWMBOs bathroom takes precedence over speakers. I'd be happy with anything lower than 200Hz, but I think the very stiff surround means it may be a bit higher. Still haven't got the boxes I promised to look at, these may drop in they may need work, but it is a swap for building work so they need to be a little better tan just OK when finished __________________ QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"

22nd July 2011, 02:01 AM	#6
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hmmm...... The separate cup looks quite deep to me, I'd say Fb is likely < 200Hz. Maybe Vcup is a lot bigger than Vas if the driver has stiff suspension, but then the question is why the depth / volume of the cup ? Will you get the original mid drivers (bust or not) ? Cone tapping should quickly illustrate the relative Fs's or Fb's. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow Last edited by sreten; 22nd July 2011 at 02:04 AM.

22nd July 2011, 03:14 AM	#7
Moondog55 diyAudio Member Join Date: Jun 2007 Location: Norlane; Geelong: Victoria: Australia	Maybe, I certainly hope so. Although the last pair of "broken and useless s*** " speakers I was given were fixed in 30 seconds with a soldering iron and sounded quite good when a little poly was added to the box. At the moment I don't even know if the woofers are 12 or 15 all I know is that they are ::"HUGE" :: which in todays world of mini surround systems means anything larger than about 6inches __________________ QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"


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22nd July 2011, 03:15 AM	#8
Moondog55 diyAudio Member Join Date: Jun 2007 Location: Norlane; Geelong: Victoria: Australia	Volume is 1'3 liters which is as you say reasonable __________________ QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"

22nd July 2011, 05:11 AM	#9
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Sydney	Hi Moondog, IIRC, the Foster units were part of Plessy's last stand before they dissappeared from downunder; perhaps a search of old EA mags (~ late 70's?) if you can track them down in a local library may have a project that used these units?? (Sounds like you're a bit busy for that though... :-) __________________ ‘today… there lives alongside the twentieth century the tenth or thirteenth. A hundred million people use electricity and still believe in the magic power of signs and exorcisms” Trotsky

22nd July 2011, 07:14 AM	#10
Moondog55 diyAudio Member Join Date: Jun 2007 Location: Norlane; Geelong: Victoria: Australia	G'Day Pete Only said yes to the rebuild because the mate is a carpenter and he will reciprocate in kind. __________________ QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"

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