Posted by Matt Rogers on October 29, 2002 at 08:09:32:
Dear Fellow Sound Labbers
I have a pair of Pristines II with a new set cores (installed a few months back) and have been very happy with them before and after the upgrade. Recently I have biwired the speakers and had the whole x-over taken out of the back plates. It is now attached on the top of the back-plate with wires coming through the hole left by the removal of the brilliance pot. At the moment it is very easy for me to experiment with different values and quality of resistors and caps. They would be housed in a nice box and properly hard-wired in the future after all tweaks have been "completed" if ever.
The thing that I am trying to achieve with these tweaks is for the Pristines to sound less bass heavy. The bass sounds too good compared to the upper mid range which I think is slightly recessed and undynamic. All things said, I have lived with them for many years and is now going for "perfection." They are great speakers.
I have since changed the value of the resistor from 7R5 standard to 12R back to about 9R. The change in tonal bablance is absolutely huge. I have also increased the value of the caps from 16uF (standard) to 24uF. As it is, it is definitely much more dynamic than the standard configuration. Perhaps a bit bright at the moment - maybe paper in oil caps may help here. Still mucking around at this stage.
This speaker came standard with a non-toroid trans and even though I have been tempted to upgrade to the toroids, I am pretty happy with the high frequency response that I got out of the speaker even before the tweaks.
Qustions:
What is the benefit of going toroid?
What values of R and uF should I be trying?
I have read in this site that some x-overs have 12R and 24uF including 15mH pararelled to the resistors. Others have 48uf and 10R. Should I be toying with some inductance here?
The Kevin Covi tweak (elsewhere on this site) on his A3 does not sound right to me. How does he get away with the overlap of frequencies (6dB slope) if he had the two x-over points meeting at 350Hz?
12R made the sound of my Pristines really aggressive, is there some tweak that I could apply here?
How do I listen for transformer saturation?
Has the bass trans been changed over the years of production? Are all models using the same trans?
How does Roger West sets the x-over points?
Will Roger West send out toroids and parts for upgrades?
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Any actual experiences or even thereotical inputs would be gratefully appreciated.
Cheers