Hi All.
A very nice gentleman dropped off a pair of Jensen LS-2b Loudspeakers for free today.
The first thing I noticed was the foam surrounds were toast and need replacing.
I then removed the driver to find the complete absence of a crossover or any parts (capacitors, inductors, nor resistors).
The cabinets are in walnut vinyl wrap.
The one of the main drivers is stamped JI050 31285 NUMBER 2207938
The one of the tweeter drivers is stamped C9972 31114 NUMBER 2207938
The thin internal cabling is soldered directly to rear of the cable terminal plate.
Were there cheaper versions of this speaker model progressively over time?
Is there a factory specified crossover (values etc) .
I'm happy to build crossovers to improve these speakers.
thanks cliff
A very nice gentleman dropped off a pair of Jensen LS-2b Loudspeakers for free today.
The first thing I noticed was the foam surrounds were toast and need replacing.
I then removed the driver to find the complete absence of a crossover or any parts (capacitors, inductors, nor resistors).
The cabinets are in walnut vinyl wrap.
The one of the main drivers is stamped JI050 31285 NUMBER 2207938
The one of the tweeter drivers is stamped C9972 31114 NUMBER 2207938
The thin internal cabling is soldered directly to rear of the cable terminal plate.
Were there cheaper versions of this speaker model progressively over time?
Is there a factory specified crossover (values etc) .
I'm happy to build crossovers to improve these speakers.
thanks cliff
Both tweeters have voice coils and substantial magnets.
The paper can be seen through the wire grilles.
Pictures please
regarding the tweeters: piezo tweers do have a housing. A piezo tweeter needs no blocking capacitor or filter.
But a piezo unit is light, made of plastic. No magnet inside.
So - hold a magnet close to it? Is it magnetic?
Attachments
P.S. There is no point in pursuing this unless you first test the tweeters and woofers (albeit with perished surrounds) to see if they are actually working.
You see - I have a good memory! 😉
You see - I have a good memory! 😉
Those are Jensen cone tweeters (made 42st week of 1977), there should be at least a cap in front of them.
dave
dave
My research reveals that the crossover consisted solely of a 2.7 uF capacitor in series with the cone tweeter.
My memory is fading in old age. Good point. I'll do some tests. 🙂
PS: Thanks to all contributors.
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Galu seems to have solved the mystery.
What's with the neat surround removal.. The glue may have deteriorated but I'm thinking someone was working on these. So when you replace the surrounds the compliance may have changed, along with the sensitivity. You might want to tweak the crossover just a little.
What's with the neat surround removal.. The glue may have deteriorated but I'm thinking someone was working on these. So when you replace the surrounds the compliance may have changed, along with the sensitivity. You might want to tweak the crossover just a little.
Someone did a neat job on the front suspension - with the four cut-outs. I have made such with paper/phenolic rings on the rear sustension]
Too bad the box then has a different function. Not a mass suspension box. [In the '50ies there were French designs that by intent so on purpose had a space between speaker unit and box, it in fact increased bass . . ]
Too bad the box then has a different function. Not a mass suspension box. [In the '50ies there were French designs that by intent so on purpose had a space between speaker unit and box, it in fact increased bass . . ]
If the "neat job with the cutouts" is referring to the white sections appearing between the basket frame sections, it's just the material packing.
I just shoved it in for storage during my assessment phase.
When they arrived at my doorstep, they included their surround foam. It was in very bad shape.
I removed it (very easily). It virtually disintegrated on touch. The glue no longer had any bonding power so the remnants of the foam mostly turned to powder and easily came away from the cones. Replacement surround foam (AUD$5 a pair shipped) is on its way. Being light foam (not rubber), hopefully it shouldn't interfere with the sound.
Both enclosures had missing caps.
Interestingly, all the internal wiring is black with red insulation tape near the two +ve terminations.
Don't know if this is factory? Apart from that the enclosure wadding was stapled in place.
It's still important to know the DC resistance of the tweeters (and the woofers while you're at it), to know if they still work. The suspicion is that with each woofer and tweeter connected in parallel, the high bass power from the amp can easily burn out the tweeter voice coils. A high or infinite resistance of a dynamic driver indicates the voice coil is open and it no longer works.
I might suggest trying a 1.5V battery, but use a 20 ohm or so resistor in series to be sure you don't burn out the tweeter. If the driver clicks when you complete the circuit then at least you know it works to some extent.
I might suggest trying a 1.5V battery, but use a 20 ohm or so resistor in series to be sure you don't burn out the tweeter. If the driver clicks when you complete the circuit then at least you know it works to some extent.
At this point you need to question everything. (fortunately there are only a few particular issues)