Steve-
I appreciate the help. I figured it was a simple question of the
head-unit being 2-ohm stable up front, but wasn't too sure. I guess I
worded my question all too complicated for such a simple question, really.
I put some Polk speakers up front and already have the infinity 4" in
the rear. I didn't touch the tweeters since it was a budget thing. The car
was brand new (<100 mi) when I had the work done and I wasn't up for taking
the door apart myself so I left the dofisses at Circuit City do it for me.
I couldn't rationalize paying another $35 instillation cost just to have
them install the tweeters (in what would have been 3 more minutes of work,
seeing as the door was already taken apart to do the woofers). The short of
it is that I'll get around to it sooner or later. No hurry.... And yes,
they had to do a _lot_ of modifying. In fact, the factory speakers in my
car where integrated into the mounting points so they had to cut the
original cones and magnets out and carve up the plastic parts to make the
speakers fit. It sounds good now, but there is still some door-rattle even
with the noise suppression B.S.. As soon as I get a subwoofer installed I
will put bass-blockers on the other speakers.
The stereo sounds fine, now but I still want more bass. I've still got
my 12-inch 500W Pioneer speaker and box left over from my old Camaro and
need to install it in the trunk. Don't wana put it in the trunk (I fear
rattles and loss of space), but unfortunately the 200W 10-inch Infinity
powered sub (which I really want and hear is quite adequate) won't fit under
the passenger seat. And I think the Subaru version (same as the Clarion
7-inch unit) is too crappy and cheap. So I will use my box/sub and do the
amp install myself. I like the "look and feel" of the brushed aluminum
head-unit, it goes well with the new interior of the '05 Subbie, and is a
6-disk version. Any spacer DIN would be too guady looking for my tastes. I
don't need MP3 option because I will put an in-line PPL FM modulator in for
my iPod (although I hear the '05 Subbie antenna is weird and won't fit
anything already on the market...). Although that sounds inplausible, then
again...
So I guess I'll have to take some line-level inputs to my amps (4-ch for
the main speakers 1/2-ch for the sub). I don't know if I can drive the rear
speakers and tap off for the amp at the same time (until I get the 4-ch amp
installed). Then again, I think the speaker-level inputs on the amp have a
high (ideally, "infinity") impedance so it won't really effect the way it
drives the rear speakers. In the end, my plan is to tap the rear speakers
into the bass amp&sub and then split the front speakers and plug it in as
both front and rear inputs of the 4-CH amp. I will route (via a high-pass
filter) back into the front 2-channels (woofers and speakers) at 2-ohms and
the rear speakers on the other two channels at 4-ohms. Again, I think this
is all possible because the inputs only need amplitude and frequency, not
power, because of their high input impedance.
Mike
P.S. Do you know the size of the tweeters and recomend any specific brand?
----- Original Message -----
From: "Steve Jernigan" <(e-mail address removed)>
To: <(e-mail address removed)>
Sent: Tuesday, August 17, 2004 8:22 AM
Subject: Re: WRX Alignment Specs
Hi Mike!
I tried to reply from home; alas I am stuck with unix command-line "mail" when
using my wifes PC. The message bounced, maybe because of the leading "_"
character in your return address? This is what I see on this end when I
reply:
Mike Lloyd <(e-mail address removed)> (remove)
Anyway, here it comes again, without the _ . . .
**********************
These numbers should work fine:
Set front camber to max negative using stock adjusters. This will probably
only be a degree or so; but more is better up to about 1.5-2 degrees (spec
for performance street tires on stock suspension). No adjustment available
for the back, unless you install camber bolts, a very common mod.
Set front toe to 0-2mm total toe out. The more toe-out, the better turn-in
response, at the expense of some high speed stability. For a daily-driver
(never autocrossed), aim for 0.
Set rear toe to 0 to 2mm total toe in. 0 for turning response, 2mm for high
speed stability. Aim for 2mm on the daily driver.
DIY, using string on jack-stands. 1st set the camber, max out the adjusters on
both sides. Tie a string between two jack stands and set alongside the car.
Do another for the other side. Adjust the jackstands such that the strings
are at the same height as the hub centers, and equal distance left to right.
This makes the strings parallel to the car. Record the distances from the
string to hub centers, this will make subsequent set-up easier. Oh. and be
sure the steering is set straight.
Measure (use a steel ruler) from string to the front of the front rim, and the
back of the front rim on both sides. If the front distance is greater, you
have toe in; less, you have toe out. Begin by setting toe as close to 0 as
possible, and note how much adjustment to the tie-rod it takes to get there.
This can be a bit tedious the first time thru, but it gets easier with
practice.Take the car for a drive around the block, and repeat the
measurement.
By now you should have a pretty good idea of how much adjustment it takes to
move the alignment by X. If you end up with the steering wheel cocked a bit,
adjust both sides differentially to correct.
Repeat this process for the rears.
This sounds kinda primitive, but it is very accurate, and is the way virtually
all race car alignment is done. After you've done it a time or two, you'll be
able to set-up, make measurements, make necessary adjustments, and verify
them in an hour or so. On _any_ car.
Search the internet for a product called "Smart Strings". Just a fancy way of
doing it (works well, tho), but they have a down-loadable manual that goes
over the process in better detail than I can provide in an email.
Hope this if helpful.
ByeBye! S.
--
Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101
S said:
that the radio only has one set of front channel outputs. That means that
the tweeters take a splice off the front speaker wires. (I also know that
the tweeters have a built in hi-pass filter, not an in-line one).
2K2 WRX, the tweeter has a small crossover capacitor attached. The
tweeter is in parallel with the front woofer, and the wiring is in the
door (ie only one pair of wires enter the door).
If you put an extra set of speakers in parallel with the front speakers at
the same resistance (I assume), then the effective resistance is halved as
far as the head unit (or amp) sees things.
Modern electronics are generally happy driving anywhere from less than
2 ohms, to 16 ohms or so; the higher load impedance (Z, AC resistance)
yields a reduced power output. Having a tweeter+capacitor in parallel
with the woofer is a very common arrangement, and results in the
system Z falling from ~8ohms at low frequencies, to ~4 ohms in the
treble ranges (assuming 8 ohm speakers). No problem.
or how is it compensated for?
See above.
want to go into a 4-CH amp and then back into my 100W Polk speakers (Ft. and
Rr). How then can I also feed into the tweeters without throwing off the
resistance balance to the amp? (and don't say get a 6-CH amp, plz...)
