[Peter Larsen[_3_]]

Peter Larsen wrote:

Phil Allison wrote:

** From your graphs, the woofers seem close in level but there is
something fishy going on with the other two drivers.

DHL found and delivered the other PL315/4 today. Like the 8 Ohm box
it has a bit too much bass, midrange and treble but a nice open
sound, so this does appear to be about a somehow broken box,
measuring comes later, 4now I just wanted to verify that it arrived
OK.

A bit of initial data: bass resistance some 2.5 Ohm, mid some 7 Ohm and
piezo some 3.3 Ohm. Bulb resistance around 1 Ohm. After opening and
assembling the deviant one its mid and treble went totally silent. Opened
rear panel for bulb access. The main cause of problems was the bulb fixture.

The bulb has small bullet on end that should match a contact surface that is
loaded by spring. That surface was not perpendicular to the bulb axis and
consequently the bulb had gone from lacking to no contact.

Finagling with the contact surface and repeatedly rotating the bulb removed
the majority of the difference between the two 4 Ohm boxes. Sound - nor
curves - are not totally identical, but making physically identical
measuring setups so exactly as required by an off-axis tweeter is
non-simple. It probably will require soldering a bypass of the
bulb-protection device to eliminate it as a cause of difference, at least
during measurement and it is a long long way from being roadworthy in my
understanding of that word.

Consequently - and with the total cost of them, shipping cost included, in
mind - I have informed the seller that I have accepted them as OK within
what they are.

The boxes are totally clean inside, conformant with the sellers description
of them as having been used for ballroom dancing and being stored inbetween.
I wonder whether they have led too silent a life ...

Opinions on replacing the piezo with a Beyma CP16, impedance curve looks
benign and there may be enough front panel real estate for it?

Peter Larsen

Kind regards

Peter Larsen