The Epicenter splits the signal internally. One side of the split does
high-order filtering to remove anything above about 160Hz, then uses
variable comb filtering to identify a set of harmonics for a missing
fundamental note (harmonics are the overtones that make a C-sharp from a
clarinet sound different than the same note from an oboe), then
amplifies the fundamental tone and passes everything through a low-order
low-pass filter (so the harmonics don't become too overbearing). The
"boosted" side is then combined back into the main signal and what you
hear is more -real- tones down low. (I say -real- tones, because your
brain so much expects to hear a combined fundamental and it's harmonics,
that when it's fed only the harmonics it automatically puts the
fundamental back in.)
I've heard and used the Epicenter on several cars, both mine and
others. It's very easy to overboost the sound and make the low end
sound really unnatural (good for boom-boom dance music, bad for anything
that came out of an instrument). If the boost knob is used reasonably,
it definately makes a audible and measurable difference in the sound.
It works best for me if I have the signal pass to the Epicenter -after-
the sub crossover (between the sub crossover and the sub amp) and the
sub crossover is set to no higher than 70Hz or so.
As far as ground loops, all of those noise issues can be solved by very
meticulous troubleshooting. David Navone at Autosound 2000 wrote a
pretty good article a number of years back on the how-to's for tracking
these issues down, and even did a flow-chart type of thing that was like
"if you test XYZ and get this result, then change blah...blah...blah".
In the end, ground loops (the alternator whine that varies by RPM, or
whine when a fan motor or light is used) are caused by differences in
the ground path potential between the components. (english
interpretation: electricity is like water, in that it will always seek
the path of least resistance. The amplifiers have a really good ground
-let's say .005ohms- and the radio has a less good ground -let's say
.006ohms-; the radio will send a part of the ground electricity through
normal ground wire and a smaller portion through the RCA cables -in this
example, one sixth of the juice goes through the RCA cables-. The
trickle of 12voltDC juice in the radio-to-amp path creates the noise.)
For radio induced ground loop noises, I have had best success by doing a
variation of what Dester had done with the RCA ground loop isolators.
See, there's two ways of fixing the problem: either (a) eliminate the
path for the trickle to happen, or make the radio and amplifier have the
same ground potential. Most of the RCA ground loop isolators I've
worked with are not 100% effective, and I've built a couple of cars for
competition where the absolute best is just barely enough, so I've taken
a slightly different approach. I will have a Power Distribution Block
for the amplifiers/crossovers/whatever for the POSITIVE and NEGATIVE
connections, then I've simply connected the radio's + and - leads to the
same block as the amplifiers using a good (no joins or splices) 16/18
gauge wire. Then, I put a RADIO ANTENNAE GROUND LOOP ISOLATOR (also a
Radio Shack part) between the radio's antennae lead and the car's
antennae. (this affects sound quality less in my experience)
There you are. The parts cost for either approach is about the same
(two or four RCA isolators vs. one antennae isolator and a few feet of
wire), but the second approach definately is more intricate and takes
more planning.
Hope this helps.
Kurt
Dester223@aol.com wrote:
>
> I've heard of an Epicenter. It's supposed to slow down the bass notes, so
> they sound deeper and "longer" I have never heard it in real life.
>
> For my ground loop problems (i have 2 amps) I bought an inline ground loop
> isolator for the RCA cables. costs about 15 bucks from radio shack or a
> stereo shop. I think it's the best product out there. It literally stopped
> all the alt whine/stereo hiss in my audio application.
> -Dester
>
> << Also does anyone have or has had an Epicenter and
> would you recommend it? pros and cons?
>
> http://thematrix.acmecity.com/oracle/195/98dakota.html
> Alberto
> >>
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:49:48 EDT