Impedance matching (speakers - amp) with Altec autoformers
Janos
The Altec Electra Voice autoformers have arrived, so tried them out
instead of the 8ohms resistors. These autoformers are rated 100W, and
have taps for 4,8, 16, 50, 70, and 100ohms. Hooked the 16 ohms tap to
the amp, and the 4ohms tap to the speakers. The connection is
temporary, with magnetic interim connectors and a single CAT5 twist
running from the Altec to the speaker binding post - probably not
optimal at all, since the autoformer transforms voltage to current
drive.
Gave a first listening test with 12 Concerti grossi op 7., from
Locatelli. It opens up with the playfulness and complexity of Mozart
(Nelli thought I was playing Mozart), but from the second concerto on
it is of 100% hard-core italian tradition, a la Antonio Vivaldi, the
Red Priest. He is an almost unknown composer, but of the finest kind.
I was prepared to hear someting like what the resistor was doing to the
sound: somewhat extended base, and highs. Well, it worked out nothing
like that. Change in base and highs was not standing out, as with the
resistor.
However, there was an overall change, that was nothing less than a
revelation.
Lately I have been plagued by unsatisfaction with the sound. Many times
the setup sounded thin, compressed, and distorted. I was blaming the
preamps volume control, the front end, and lack of synergy.
The Altec iron changed the overall sonics to what I had when my chain
sounded the best, rougly two years ago. (Since then, with consistent
hard work, I managed to downgrade sonics significantly... some aspects
improved, but, overall, two thumbs down.)
The Locatelli CD sounded so different compared to without the
autoformer, that I would not have recognized the two presentations
coming from the same disc. For one thing, it sounded like vinyl. No
digital haze, artificial pressure, and electric presence in the air.
After all, the CD player was not to be blamed, as I was suspecting
wrongly.
The soundstage is analog-like, instruments have that analog-kind of
body, lacking the artificial, "digital" over-clean, color-less edge
that makes "digital" soundstaging different from that of real life
instruments.
The body of the instruments is better, and the lack of mid-base that I
was having is not that apparent anymore. However, the influence of poor
room acoustics is much more apparent now. I can start toying around
with speakers placement and furniture... as my place gets more and more
crowded, the harder it is to find listenable speakers positions. The
sweet spot is hopelessly gone until I have a bigger place, but the
sound is quite consistent even listenig from the kitchen.
The dynamics handling became much better with the Altecs. When the
double bass section enters, you can feel it. Before, it was clean, but
audible only for golden ears. Now you can hear the contrasts much more:
they are playing in forte, the entire double bass section sustaining a
low note; suddenly every instrument stops, and the violin starts a
solo. Very hard to describe the emotions. The violin sings, with full
body, harmonic and dynamic richess.
I could go on describing the improvements, but to no avail, as it still
does not sound as high-fi as my system sounded at its peak. But it has
gained back the quality that no matter what I put on, I want to listen
to the end, erasing all the tweaking-urge.
>From LP, I checked out a Led Zeppelin album. Although phase inverted,
(I was too lazy to change the phase at the speakers), and one channel
working only (I need a Kahuna to purge out that phono stage of the
PAS...) it made my feet move, and I listened to the entire album.
Without the Altecs, a phase-inverted album (either CD or LP) sounded
completely unacceptable to my ears.
The story is not over yet. Charlie has also a pair of these iron, and a
pair of inexpensive Rat Shack autoformers, too. I'm very curious what
they could do to his Yamamoto...
I have chosen the 4ohms and 16ohms taps on random; trying out different
taps could be beneficial, and probably different taps would work best
for different SETs.
To everyone with SETs I recommend a try with autoformers. I have a
spare pair, everyone is welcome to try them out.
Janos