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
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
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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.)
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.)
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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
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
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.
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.
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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
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
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... 
I thought it was time I updated this. Listening at the moment 3-Way crossed 300/4k
this mid has a natural second order roll off similar to the P-13 but not as clean ( well it is 30 years old ) and this XO iteration (~300 ) is too low, Listening yesterday crossed at 500 it was a lot clearer, 500 is too high for this 10 inch woofer tho so more playing around needed.
I should add that this XO wasn't designed, it was cut and try based on the crossover in the big Plessey box which was a lot simpler, 2 coils and 3 caps
this mid has a natural second order roll off similar to the P-13 but not as clean ( well it is 30 years old ) and this XO iteration (~300 ) is too low, Listening yesterday crossed at 500 it was a lot clearer, 500 is too high for this 10 inch woofer tho so more playing around needed.
I should add that this XO wasn't designed, it was cut and try based on the crossover in the big Plessey box which was a lot simpler, 2 coils and 3 caps
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I just received an old Jaycar catalogue from 1991, ( eBay for $5- last week) these are in there would you believe.
There is an attached graph showing a reasonable similarity to reality which shows a steep roll-off below 300
Catalogue number CM-2080, giving the response as 350 to 5500 and "Suitable for use with the XO CX-2619"
Which is a book XO using Butterworth values at 600Hz and 3500Hz.
I'm going to have another go at these and use a "book" LR 2nd electrical using what values I have (5.6mH) coil and play some more.
There is an attached graph showing a reasonable similarity to reality which shows a steep roll-off below 300
Catalogue number CM-2080, giving the response as 350 to 5500 and "Suitable for use with the XO CX-2619"
Which is a book XO using Butterworth values at 600Hz and 3500Hz.
I'm going to have another go at these and use a "book" LR 2nd electrical using what values I have (5.6mH) coil and play some more.
Your woofer Pete
Third iteration
SWMBOs comment , not enough bass LOL
Sarah Brightman's "You take my breath away" has a deep synthesiser note about halfway through, CC is used to the bedroom system that has a 12 inch subwoofer as part of the system, I guess there is no substitute for surface area when it comes to bass.
this is 3.5 way with an 8.5mH coil on the .5 10 inch, CC is right, needs a little more bass
Third iteration
SWMBOs comment , not enough bass LOL
Sarah Brightman's "You take my breath away" has a deep synthesiser note about halfway through, CC is used to the bedroom system that has a 12 inch subwoofer as part of the system, I guess there is no substitute for surface area when it comes to bass.
this is 3.5 way with an 8.5mH coil on the .5 10 inch, CC is right, needs a little more bass
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I am beginning to believe that Jaycars stated 93dB/M/W isn't too far off the mark, after a few hours of listening they are too far forward and even two woofers cant keep up. Needs a highly efficient 12 inch woofer I think, just like the original design.
I hate to throw away SPL as heat tho so these may be for sale again, I cant seem to make them work together as well as they should
I hate to throw away SPL as heat tho so these may be for sale again, I cant seem to make them work together as well as they should
Hi Moondog, good to see the 8"ers getting a workout; Re hoffman's, yeah, I've got a similar problem, a pair of no-name mids that sound quite good but are too efficient for anything I've got to put under them. Like you, I'm reluctant to pad them down, but have face the reality that a couple of resistors is far cheaper than buying more woofers....
Well padding them down does have some advantages over using a mid of lower sensitivity. With the padded, higher sensitivity driver, power compression is still going to be reduced because the driver doesn't need to be driven as hard. Sure, you're now dissipating the excess in a resistor, but it's better in the linear resistor then all of it being inside the voice coil of the lower efficiency driver.
Thanx 5th
Best solution (If I can find one) is an efficient 10inch and a bigger sub woofer. These are garage speakers so I don't want to go overboard, but my mates garage is also his carpentry workshop and quite large and lossy.
I do have a pair of L-Pads I can take from the old Tandy cross-over tho to save buying resistors and that way he could dial in his preference.
Only trouble is padding the mid down also means padding down the tweeter, which IS 95dB and at the moment only has a 1R1 resistor in series to bring it up to 8Ohms
Best solution (If I can find one) is an efficient 10inch and a bigger sub woofer. These are garage speakers so I don't want to go overboard, but my mates garage is also his carpentry workshop and quite large and lossy.
I do have a pair of L-Pads I can take from the old Tandy cross-over tho to save buying resistors and that way he could dial in his preference.
Only trouble is padding the mid down also means padding down the tweeter, which IS 95dB and at the moment only has a 1R1 resistor in series to bring it up to 8Ohms
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