Archived from groups: rec.audio.tech (
More info?)
Michael Squires wrote:
[quoting me]
>>I do not know the current status of this, but traditionally
>> JBL supports [pro products or something to that effect]
> JBL no longer has the original aluminum 375 diagphragm in stock,
> but does stock a replacement in titanium which they consider
> superior.
It is not irrelevant for an old system whether the membrane resonance
frequency is changed, conceivably some systems may require a cross-over
modification if it is higher in the new version than in the old version.
Similarly an extended top range may be a dual edged sword for a system
that crosses over to a 075 at 5 kHz, there too a cross-over modification
could be relevant.
> The people whose opinions I trust (sound engineers) are pretty
> clear that they consider the titanium version superior;
In a new system, no doubt about that, in an existing well balanced one
it will change it. It is a last resort, do both loudspeakers kind of
thing, there are similar spareparts recommendations for the L100. But
the local repair shop (Quali-Service) had all the old parts on the
shelf, so now the treble units of the somewhat deranged L100's I bought
some years ago have new original foam front covering and new
center-domes, some kid or cat dented the old ones and they were
consequently somewhat sharp sounding.
> however, having an original set of aluminum diaphragms with the
> red (glyptal?) seals is currently worth hundreds of dollars on eBay.
Of course, and perhaps they even fit the new magnets .... I know that
Altec did offer remagging, but I have not heard of JBL offering it, and
I do wonder whether just any loudspeaker manufacturing plant could do
it, I have encountered 2440 units that had lost 6 dB sensitivity due to
demagging by heavy use.
> If the woofer in the L65 is anything like the D123 a friend
It hurts whenever I read about those, someone lent me a pair that was
not in use some 20 years ago. I couldn't afford them at the time, so
fool as I was I returned them, I didn't want to keep borrowed things for
too long.
> had in a folded horn system ca 1965 then it is capable of some
> pretty amazing bass (above the cutoff frequency of the horn,
> of course).
The D123 is a front horn thingy rather than a rear loaded horn thingy,
rear loaded horns benefit tremendously from having a driver with Fs
below the horn cut-off, with front loading it is more about matching the
compliance in front of and behind the unit so that it moves
symmetrically.
The L65 woofer is however nothing like it, I have tried to remember
whether it is the same chassis, and I am fairly certain that it isn't,
it is more like the K120 chassis, it could be that it is a K120 with a
heavy membrane, foam front suspension and a very soft rear centering
spider instead of the fairly rigid K120 spider. I think the reason for
the lack of spareparts now is that the L65 never did appear in a "4
digit version", ie. was "just a loudspeaker for the home" and not a
Loudspeaker. Marketing wise it was somewhat an ugly duckling ....
neither one nor the other and it died just before it could have been
sold as "digital ready" .... an O76 had probably been a much betteer
match to its 5", it was a most pleasant thing to listen to.
> Mike Squires
Kind regards
Peter Larsen
--
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