Copyright 2010 © Troels Gravesen
PL14WJ-09-08 + XT25TG
The PL14WJ09-08 is to my ears one of the most smooth sounding 5" drivers ever made and no wonder it has been a steady driver in the Tymphany program for years and years. Due to cone geometry, coating and suspensions, it's got an even response all up to 7-8 kHz, allowing simple crossover construction. It's not particularly efficient, but the result is decent bass response down to 50 Hz in suggested cabinet. With a Qt = 0.36, it's a perfect driver for box simulation. Overall system sensitivity is around 84-85 dB/2.8 volts. The XT25TG tweeter is a well-proven tweeter too, so no further comments on this driver.
C20WH-07-08 + Monacor DT300/waveguide
Looking at extinct Snell E/II and /III speakers, I came to think about the old Vifa C20, 8" driver. The C20 is found in numerous versions like the C17. The C20 has a lightweight paper cone, a narrow foam surround and the "H" provides a 90 mm magnet for a 1" voice coil, probably giving decent sensitivity. Googling the C20WH, I found a single shop where the C20WH was available, probably some old stock and this is what I found in seller's storage. This construction also part of HES-II, High Efficiency Speakers, part II
PL18WO-09-08 + Vifa XT25TG-30-04
Two well-know units, driven from a series crossover in a 24 litres floorstander.
The C17 story
Get 95 dB/2.8 volts sensitivity for your
low-wattage amp - in case it runs 4 ohms speakers. The
Vifa C17WH-69-08 is a "special" driver. Special
because it's so ordinary - probably made in tenth of
thousands - and special because a lot of things went
right with this driver. Sometimes a driver turns out to
have the right cone material and coating for a given
size, thickness and weight; the right voice coil
diameter; the right surround providing the right damping
to cone motion; the right magnet size to provide useful
TS-data, etc. When all the individual parts are made
right, the result may be better than what we might expect
from the sum of the parts. Read the first
part of this long journey.
I've been looking at the Monacor DT300
tweeter for some time and finally decided to buy a pair.
This is a 30 mm soft dome and how would this driver
perform compared to my much loved ScanSpeak D3806/8200
tweeter? The latter has a 38 mm voice coil and really
needs a supertweeter to make it up to 20 kHz.
Aake in Sweden stayed home one
day - alone - and played rather loud - and send me a note
telling the tweeter appeared rather grainy and distorted
at times and some mails back and forth made it clear
there was something to it. I hadn't run the C17
particularly loud and doing so, I had to admit the
tweeter took some serious cone excursion on certain
recordings. Taking the speaker to the workshop and
connecting a sine wave generator made it clear that
something around 500 Hz wasn't as it should be. First I
thought the front panel/waveguide really wasn't airtight
and the C17 drivers would introduce some pressure into
the unit, but disconnecting the C17 drivers made it clear
this wasn't the case either. Read third part
of C17 journey.
Vifa C17 mk4, the final chapter
Qualifying for being part of my stock
speakers, the C17s certainly needed some nicer cabs. Some
22 mm MDF sheets were bought and I took it to my local
veneering company and had mahogany applied. Next to the
veneering company is my local carpenter, having a table
saw at the size of a tennis court, fitted with a huge
saw-blade with uncountable teeth. Cuts MDF so sharply, I
usually cut my fingers bringing it home in my car.