Coaxial frequency

How many hz should I have it set to? I haven't set up the slope for the crossover...I'm still reading through the instructions.  Is 12db a good setting? BTW, I'm using the crossover feature on my Alpine cda-7998.

I've already created a test CD with various tones....50,52,54,56,58,60 etc etc. I thought I was going to be able to turn the knobs over the frequencies I recorded and that once I past 100hz I wouldn't be able to hear anything but I was wrong...I still hear sounds past 100hz even though I only recorded tones up to 100hz.

Yes, I definatly agree with the comment above that 100Hz is a bit low for a 4" speaker.  I'd suggest setting it up around 250Hz.  Also, those MBQ coaxials are rated at 30 watts RMS, so if you are bottoming them out it could be due to overpower.

Stevdart is correct concerning a crossover slope.  Crossovers are not like a cut-off switch.  If it is a 6db/octave crossover for example, that means the musical power will be reduced by 6db one octave (eight tones, or twice the frequency) above or below the crossover setting.  So if you have a HPF for your coaxials set at 100 Hz, you will still send 50Hz information to the speaker, only it will be attenuated by 6db.  Crossovers with steeper slopes (higher number of db/octave) will reduce the signal strength faster around the cross point.

Oh, I was under the impression that I wouldn't be able to hear anything once I past that frequency because it was going to cut off. My MB Quarts are actually RKC110's not PKC....the box said something like 80rms. When you guys are refering to the filters are you talking about the ones on my  HU or the ones on my amp...or both? So I'll definitely hear the difference between 105 and 100hz?

Howcome the knob on my amp goes all the way up to 5khz? Do some people actually have it go that high depending on the setup?

If my amp has a max rating of 800rms, when does it actually put out 800rms?

Stevdart, I've read some posts you responded to about setting gains and so forth and you recommended having the volume at 85% on the HU. Am I deaf because when setting mines I had it at 33 out of 35 and I didn't hear any distortion...so I just backed it back down to 26 just to play it safe.

1.  Yes, "filter" usually refers to a crossover.  The one in your HU or your amp can be used, but I recomend you only use one and disable the other one.  The actual RMS rating fro those speakers should be listed in the owner's manual.

2.  I doubt very seriously you can hear the difference between 100Hz and 105Hz.  Like I said before, with a 4" speaker I would try 250Hz.

3.  Yes, an HPF up to 5KHz is very useful, especially if you are driving a set of tweeters.

4.  "Max" and "RMS" ratings are two different things.  Post your amplifier make and model and I will look it up.

5.  The recomendation that you use "85%" or any other setting to set input gain is simply a ballpark.  You may use any volume setting you choose as long as you stop before you drive the head unit into clipping and you never turn it up past that point.  As far as you not being able to hear distortion, if you are talking about hearing it in your subs that is not unusual.  Try using a tone (at, say, 80Hz) and (wear hearing protection!) try this:

Disconnect main speakers amp.  Set subwoofer amplifier gain to minimum. Turn up tone volume using the HU until you can hear the pitch seem to change.  This is the audible clipping point.  Back it off until it returns to normal and never operate above this volume level.  Increase the input gain on the sub amp slowly until you again hear the pitch change.  Back it off until it returns to normal.  This is your max gain setting for that head unit.

85% is not in my vocabulary, so maybe that was someone else.  I don't like to put a number on deck volume.  For instance, in my car I'm using the factory deck, and found that the max level that I felt it sounded good was just under 2/3.....about 60 to 65%.  So just use the volume level of the head unit that you think still sounds good without distortion.  You have to listen to it with the amp gain set all the way down.  Normally, 3/4 or 75% is the given default setting for maximum on the deck.

Back to question 1:  a decimal (db) is the unit of sound measurement that people can actually hear a difference in the sound level.  3 db is a noticeable difference in sound level.  So if the crossover is at 100, you will definitely be able to tell the difference between that and 105 db (if you're setting a mid/tweeter highpass).   Keep turning the setting until you hear the difference. 

There's no such thing as a max rating in RMS.  There's RMS, period.