Technical help le175

[davidpou]

Hi,
I have a pair of L101 that need some checking since they have been untouched in the last 40 years...
I have 4 questions (for now), as follow:

1 I assume the lansaloy is dead as described on the forum in pervious post; is this the correct replacement : http://reconingspeakers.com/product/jbl-le14a-c8rle14a-recone-kit/#prettyPhoto ?

2 I read also in prvious post that the LE 175 might need some care as a foamy substance is decomposing after serveral years. i tried to undo them but find only what you see on the pictures... and nothing wrong so far. do I need to undo the JBL red wax to reach this substance ? (othe pricture)

3 I have changed in the past the Lpad... I have been adviced on the site to go for 8 ohms (this is on the Ts for the LX10) and 15 W ... but as I turn the knob I do not hear much difference between min and max... is 15 W the correct power for this L pad ?

4 I measured the impedances... The Le 175 are good I think since It says 6.2 ohms and TM says between 5.9 and 7 ohms, but for the LE14A I measured 5.7 ohms and TM says between 5.9 and 7.1 ohms ... is it that bad ? if yes, can something be done ?

below, some pictures, to illustrate.
many thanks for your help
David

RED WAX TO GET OFF IN ORDER TO ACCESS THE FOAMY SUBSTANCE ?
61504

WHEN I UNDO THE BIG SCREWS IT DOES....NOTHING ! i can t pull bits apart
61505

PART THAT LOOK FINE AND CAN BE DETACHED:
61506

To be exhaustive, measurments:
61507
61508

[more10]

I read also in prvious post that the LE 175 might need some care as a foamy substance is decomposing

In order to check this you need to remove the back of the driver. Since you drivers have original seals this is not recommended since the value will be lower. This is a collectors item.

The LE175 is has a weaker magnet than LE85, so swapping your pair to LE85 will be an upgrade. I have no idea on the collectors market for LE175 is, but it would be worth trying selling them on ebay.

[macaroonie]

Here is a pic of the inside of a 175. Google images is helpful to find this type of image.
If you can see rotted foam it has not come from here. I'm not sure if there was a foam damping pad in the back cap but it cannot get through to the horn as you can see.


61518

[jbl]

Before taking resistance measurements, short your probes. Subtract this reading from you measurements. That is the actual reading.

[davidpou]

hi,
sorry can you explain "short your probes"... ?
My english fall short on this ...
David

[hjames]

hi,
sorry can you explain "short your probes"... ?
My english fall short on this ...
David


Touch the two Probes from the meter together (short them against each other)
and set that as zero on the scale ...

This may not be necessary on newer meters ...

[jbl]

Touch the two Probes from the meter together (short them against each other)
and set that as zero on the scale ...

This may not be necessary on newer meters ...Thanks, Heather for saving me the time to reply. My Fluke 179 (Bought new in 2010) still needs to have the probes shorted in this way. If not the reading is about 0.2 Ohms. Must be the resistance of the test probes/leads. The best way to measure resistors is to connect them directly to the post on you DMM. This is only needed for very accurate measurements.

[subwoof]

The picture above of the 175 shows AFTERMARKET diaphrams that have the diamond surround and are made of titanium.....the original 175/2410 diaghrams with th tangential spiral surround and are made of aluminum ( and no hokey sticker ) look much different.

sub

btw - most of the older LE series used felt pads with no foam..:)

[more10]

btw - most of the older LE series used felt pads with no foam..

Do NOT remove the red seal! Do NOT open the back of the driver! Unless there is no sound of course.

[martin2395]

Do NOT remove the red seal! Do NOT open the back of the driver! Unless there is no sound of course.

Yes, DON'T TOUCH the red seals - it will kill the collectors value.

[davidpou]

Ok ok I WILL NOT UNDO THE WAX....

ok for the meter i will set the probes as you said thanks for help in translation...

so do you guys think I bought the correct Lpad ? is 15W enough ?
I yes, how can we explain the so thin difference beween max and min ? Why do the medium is not that nice ? (as compared to my 4312A that most of you would, I am sure, describe as easily beatable ?) provided the impedence is good....