Ok... I figured I'd stop hijacking that other audio post and start a new one. Although I've been listening to and have upgraded my sound system in the past, i'm still thirsting for knowlege on the subject of car audio. My first question is what do HPF and LPF really mean? High and Low right? Where i'm running in to confusion is my amp has an hpf and lpf setting. Then, my head unit has hpf and lpf settings on it also.

You are correct. LPF = Low Pass Filter designed to send on ly the lower frequencies to say a subwoofer. HPF = High Pass Filter designed to send higher frequencies (block the bass) to the smaller remaining speakers. You would typically only use one set of filters either the ones n your deck or on your amp. Using both can create 'holes' in your frequency response making the system sound awful. Now to determine which one to use i'd suggest checking the manuals to determine which has the steeper crossover slope represented as ##dB/octave. 6,12,18 and 24 are the most common. The higher the number the steeper the slope. I also use the steepest slope available to the sub, but for the high pass i trust my ear, but usually I use 12dB/ocatve as a minimum. I would be hapy to help you choose if you can find the information on you equipment.

What amp and what head unit do you have?

If you are interested in car audio and have a thirst for information, here is a good site, you should read the whole thing:

http://www.bcae1.com/

Then when you have questions, ask them on this forum:

http://forum.elitecaraudio.com/forumdisplay.php?forumid=2

Head unit is an Alpine CDA-7893:

Ai-Net CD Receiver (Silver with Blue LEDs).
AM/FM/XM Ready, 60W x 4 V-Drive Amplifier, Bass
Engine Plus, 4V Sub, 3-Pre with Sub Level, V-Link,
Media Xpander, Remote Control Included, Swing
Mechanism

General
60W x 4 V-Drive Amplifier
3 PreOuts
4V Subwoofer PreOut
Versatile Link Ready
Bass Engine Plus«
Subwoofer Level Control
Subwoofer Phase Control
Bass Center Frequency Control
Bass Width Adjustment
Treble Center Frequency Control
3-Position HP/LP Crossover (12dB/Oct.)
4-Channel Digital Time Correction
Media XpanderÖ (MX)
Rotary Encoder Volume Control
Separate Bass & Treble Control
Fader & Balance Controls
Oversampling ...................................................................................8X/352.8kHz Wow & Flutter (%WRMS) ................................................................................B.M.L
Bass Engine«
Subwoofer Level Adjustment Range .........................................-15dB to 0dB (1dB steps)
Subwoofer Phase Control ...............................................Normal (0?) or Reverse (180?)
Bass Center Frequency (Selectable).............60Hz, 70Hz, 80Hz, 90Hz, 100Hz, 130Hz, 150Hz, 180Hz
Bass Width Adjustment (Q) ........................................4 Choices (1= Wide, 4=Narrow)
Bass Level Control Range ..................................................?14dB at 60Hz (2dB steps)
Treble Center Frequency (Selectable) ..................10.0kHz, 12.5kHz, 15.0kHz, 17.5kHz
Treble Level Control Range............................................?14dB at 10.0kHz (2dB Steps)
Crossover Type .....................................................Independent HP/LP (2-Way)
Analog High Pass Crossover Frequency (Selectable)..........................Off, 80Hz, 120Hz, 160Hz
Low Pass Crossover Frequency (Selectable) ...........................Off, 80Hz, 120Hz, 160Hz
Number of Time Correction Channels ................................4 Independent (FL, FR, RR, RL)
Time Correction Adjustment Range........................................0.0ms to 9.9ms (99 Steps)
Media XpanderÖ Modes/Level ..........................FM, CD, XM, MP3 (Level 1, 2, 3, Off), .................................................DVD Video (Level 1, 2, Off), DVD Music (Level 1, Off) Media XpanderÖ AUX Settings .................................MP3 , Music, Movie (Level 1, Off)

Here's what the cadence site says about my amp:
Model Q2000
4 Ohm 2 X 60
2 Ohm 2 X 100
Mono 4 1 X 200
Freq Resp 20Hz-30Khz
SN Ratio >100dB
THD <0.05%
Damping >200 @ 100Hz
Channel Sep >65dB
Dimensions (LxWxH) 6 x 10.75 x 2
Inputs 2
Input Voltage 0
Outputs 0
X-Over Frequencies
Accessories

The audio place that did the install has it 4 Ohm bridged.
There are recessed knobs on it saying:
LPF 50-120Hz
HPF 70-700Hz

A 3 position switch:
HPF-LPF-FULL

A Bass Drive on off switch.

Sub is a kicker Comp VR10


On a side note: Why is this particular amp so expensive? MSRP on it is $359. Granted I paid less for it but I see cheapo amps in the much higher power rating for less. Is it a quality amp? The guy at the audio place reccomended it.

Let the audiophooling begin. <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> <img src="/forums/images/graemlins/nana.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/shiner.gif" alt="" />

Lots of things come into play. For example:

S/N (signal to noise ratio). The higher the ratio, the better.

IMD (distortion rating). The lower the number the better.

Channel separation. The higher the number the better.

Etc, etc, etc...and you can drive yourself nuts.

Alot of auto amps are rated in "peak power" which is a crock. Basically can pump out 100 watts but only on peaks...and with lots of distortion. RMS rating is a continuous rating where an amp can pump out continuous power and still meet it's specs.

So...you could have a 1000 watt peak power amp that sounds crummy compared to a 50 watt RMS rated amp.

Audio also has ALOT of voodoo science.

I'd be scared to put all that equipment in my Kia and trash it in a bad road. I have a simple JVC MP3 radio 50Wx4 with 6.5" coaxial Jensen speakers in the front and two 10" boxed speakers in the rear and this thing rocks. I used to add amplifiers to my systems, but I got tired of dealing with a bunch of wires and noises coming from all different parts of my radio system. I admire those who like to tangle the sound properties of a good sound system, but I just gave up. My wife does have the goodies, amplifiers and all, but she does not go off-road. Still, let me ask this question, I have a couple of really good Yamaha boxed speakers 6ohm's, they are not too big. I was wondering, if I used them, is there a chance I would fry my stereo output amplifiers. I know the front speakers are 8ohms (I think).

Are you sure your front speakers are 8 ohms? Almost all car audio speakers are 4 ohms.

The impedence of the speaker is measured in ohms. With amplifiers, you can hook up speakers that have HIGHER impedence and not cause damage. What you don't want to do is hook up speakers that are LOWER impedence than the amp is rated for.

For example, if your amp was truly only rated for 8 ohms and you hooked up 4 ohm speakers, you would risk overheating the circuitry and frying it.

I have a feeling your deck is probably really designed to run at 4 ohms, so 6 ohms speakers would be NO problem whatsoever.

I stand corrected. I forget which is which. I know now that if my car speakers are 4 ohms, the home speakers are 8 ohms. What would happen if I used a couple of home speakers in the rear of my car (8ohms) and a couple of car speakers in the front (4 0hms) on a 4 speaker system radio? Would I burn the heck out of it? I know for a fact that the 4 ohm speakers would get more current than the 8 ohm ones thus more volume, but can the stereo hold up?