I get a LOT
of calls from the great members here and recently a lot of the same questions have been asked pretty often so I thought I'd take a few minutes to post my thoughts/experiences on some of them in one place
. BTW, please note that I'm not trying to discourage anyone from calling me for help because I'm always willing to help if I can
and I really do answer the phone!
Q: "I kept the factory headunit and replaced my factory speakers but the new ones don't sound much better (or in extreme cases they actually sound worse)
A: A lot of the factory headunits have built in "non defeatable processing" to compensate for the "less than stellar quality" speakers so this can happen."
They can also have "volume dependant" equalization which alters the response to keep from blowing the speakers (typically the bass will be reduced at higher volumes). A device such as the JL Cleansweep will dramatically improve the quality of sound in the situation where you want to keep your factory head unit.
Q: Are aftermarket headunits "better" than factory headunits?
A: Not necessarily. Aftermarket headunits typically will have more features however in
some cases the the OEM factory specs will require tolerances that are tighter than those for some aftermarket units (this info is from a friend that is an engineer for Ford).
Q: Do I need to separate my power wire from my speaker wire and interconnects?
A: This is a myth that has been around a long time. I believe it came from cases where people ran the wires together and got induced noise. They would then separate the wires and the noise would go away so they figured it was the wires next to each other that caused the problem. This can be dispelled quite easily if you look at it this way-it takes a positive and negative connection to complete a circuit, correct? The ground wire from your vehicles battery is connected to the chassis/body correct? So if that's the case no matter where you run the speaker wire/interconnects they will
always be "on top of the power wire" per se, correct?
. This is not to say that there cannot be noise induced with the wires next each other rather that the problem was most likely caused by a bad cable, something electronic the wire was near or what I call a "hot spot" on the vehicle where the wire was and when said wire was moved "away from the power wire" the noise went away.
BTW, I've run all the wires together in the countless number of systems I have installed over the years and have never had a noise problem in any of them.
Q:Is sound deadening my vehicle worth it?
A:IMO yes, but it also depends on what "level" of sound quality you are looking for and what it is worth
to you. Personally I am always looking to get the "most" out of my sound system so I go overboard however for some people the "point of diminishing returns" comes before the cost/time of deadening.
Q:What are the "best" speakers out there?
A: There is no "best"
for everybody and every application since as I mentioned,
I cannot hear what you can hear and you cannot hear what I can hear! Since speakers are
what actually make the sound 
I ALWAYS make them the first priority in my
sound system or any system I build. The best bet in finding speakers that work best
for you is to listen to them yourself however I know that is not always possible so you'll have to rely on the ears of others/reviews and hope they have similar tastes to yours. And don't forget,
a "good" speaker installed properly will sound better than a "great" speaker installed improperly"
Q: Should I use "rear fill"?
A: As with most things, car audio is all about "personal preference".
If you like sound "all around you" or are concerned with the rear passengers use rear fill! If you are looking for "competition type" soundstage/imaging I'd say not to use rear fill as it will be more difficult to maintain a coherent front stage. An easy way to find if you like rear fill is to fade your headunit all the way to the front and if you like it like that don't spend any money on the rear! If you do prefer rear fill, the front speakers will still be doing the majority of "the work" (or should be
) so I typically suggest spending the "lions share" on the "best" speakers within your budget for the front and using a pair of mids only in the rear. Also, if you are using the rears for "ambient fill" only (and not 5.1 surround etc) you won't need much power to them. When I install systems with rear fill speaker I usually run them off of the headunit and I typically don't use tweeters as they can "pull" the sound towards the rear (but again, if that's what
you like then do it!).
Q: Will I blow my speakers if I "under" power them?
A: Another one of those myths I keep seeing repeated all the time but I beleive it is just because some have not actually had this explained before. This one came from people blowing speakers while using amps that were rated less than what the speaker(s) could handle and blaming it on "under" powering. A very simple answer that dispells this myth is "if that were the case, every time you turned the volume down you would blow the speakers"!
Let's say you had a speaker rated at 200 watts rms and your amp produced 100 watts rms. When an amp goes into "heavy" clipping it can "theoretically" produce twice its rated power so you could "theoretically" send 200 watts to that speaker when clipping the amp. This will NOT blow the speaker (sans a defective speaker or inaccurate rating) since the speaker is capable of handling that amount of power and it doesn't "know" if that power is from a "clipped" source. Now let's say you have a 200 watt rms speaker and a 150 watt rms amp. Under heavy clipping this amp could "theoretically" produce 300 watts which
can blow a speaker rated at 200 watts rms since that is more power than the speaker is rated to handle. In these cases people would state "I blew the speaker because I was
underpowering it when in fact as you can see by the example they actually
overpowered it. (part of this was based on info I received from several audio engineers as well as testing I did on my own after learning about it).
Q: Amp "A" has .05% THD and amp "B" has .0005 THD. Does this mean amp "B" will "sound" better?
A: If you can hear the difference between .05 and .0005 you must be superman!
Here's a little test you can take to determine just how much distortion a human is capable of hearing and you may be surprised at how much you
can't hear.
http://www.klippel.de/aura/default.html
Again this is not meant to sound like the "Holy Grail" (check my disclaimer above
), I'm just passing along some experiences in hopes it will help others since I have been hearing these questions a lot lately.
You may or may not agree with my "opinions" on certain things and that's cool however before disputing anything else please ask yourself "Do I have any
solid proof to dispute that or am I just "repeating" something I heard/read?"
If you do have
solid proof please pass it along as I am always willing to learn something new myself!
Lunch time is over and I gotta get back to work but I'll check back later to field any questions/provide references or add more as I think about it.
I have and used to wonder about it until we did some experimenting using numerous mid level/high end headunits/amps at one of my car audio meets some time ago. The major finding was that MANY headunits/amps had "built in processing" even when the EQ was set on flat! 
Linear Mode
