Dissatisfied with Alpine Amps

Be careful taking a measurement of the cable that you don't short the center to the reference (ground).  This would fry the head unit.  Safest way is to use alligator clips.  Or, what I do is measure at the amp outputs where you measured voltage output...but with the gains all the way to minimum (have you noticed the 4 volt reading that shows in the JL tutorial when they describe this procedure?).

As for listening to the sub by itself, playing music:  that sounds to be normal with a good crossover.  You shouldn't be able to hear much musical melody.  The sub would have to be playing freqs higher than its intended range to do that.

The damping in the doors is crucial, so get that done ASAP.  Damp both the outer skin and the panel.  And the MDF baffle will help a lot, too.  You're not getting sufficient midbass.

The sub should still be loud in those freqs up to 100 Hz.  You're not getting what you should be there.  Borrow a pair of channels elsewhere to test, or borrow another mono amp for that purpose.

Here's one for you, Alpine Guy:   I had two different people that stock the MRV-F450 swear to me today that the sub channel is not only 2 ohm stable but that the power rating of 200W RMS is actually at 2 ohms rather than 4 ohms.   They claim that the reason my sub seems underpowered is because I am only sending it 100W RMS by presenting it with a 4 ohm load.  They also claim that many of the published Alpine specs on the amp are either completely inaccurate or contradictory.   Have you heard anything like this before about the MRV-450?

I've read that most (if not all) mono subchannels are two ohm stable, so between that, what I've experienced with my setup, and the fact that you were able to run your setup at 2 ohms for over a year, I'm starting to believe them.  Maybe I'll try your suggestion of presenting the amp with a 2 ohm load just to see what happens.  

Worst case scenario, I'll end up having a legitmate reason to replace the amp!  LOL!

You know what your problem is Sedate?  You're too easily impressed. 

If I decide to replace the VRs, what would you recommend?   I've heard nothing but good things about CDT.   In fact, I almost replaced the VRs with the ef-61cfi/25 earlier this year.   The only reason I didn't is because the tweeters are so damn big and I didn't want to cut into my door panels again.   (There's really no where else to install the tweets in my car unless I go with kick panels.)

How do you like the CDT sets you're using?   Having heard both, do you think I would be happier with the CDT's than the VRs?

I'm not sure what I'll do about the subs yet.  I can see how I would need more cone area,  but I should probably decide what I'm going to do with the rest of the system first.

...and then the lights went on.

At 14.4 volts, the amp is rated at 50W x 4 and 200W x 1 RMS

At 12 volts, the amp is rated at 30W x 4 and 150W x 1 RMS

When I set my gains, I used the 14.4 volt ratings.   So running off the battery instead of the alternator, I went back and set the gains according to the 12 volt values.

BIG improvement in clarity and overall SQ.

With the ignition running, I'll probably see something closer to 13.8 volts, but either way, I had my gains set way too high.   In fact, I even had to turn the non-fader (sub out) down on the deck in order to come in at the right voltage.   The earlier comment about the input sensitivity on the MRV-F450 not being able to accomodate the high voltage preamps on the HU was right on the money.

So, the bottom line is that I'm seriously underpowering my system and the MRV-F450, while probably a good amp in and of itself, just isn't a good match for the HU and speakers I'm running.   The JL 500/5 is much better fit, so at least now when I upgrade I'll know why I'm doing it and what I'm trying to accomplish.

I'm still not ready to give up on the JL VRs, because I want to see what they can do when my system is properly powered and tuned, but I probably will look into the CDTs at some point.  Based on Sedate's description, they sound like they're more my style.

Humm, i really doubt the alpine amp was rated at the 2 ohms, back when that amp was produced they were a stand up company still. But hey, you never know right? At 2 ohm i can truely say it made those R-15's move like they were getting a good 400 wrms.

From what it sounds like you want out of your system its probably a good idea in the future when it is justifyable to get new equipment, possibly get a 4 channel amp and a mono sub amp powering a 12" ported woofer.  So far it looks like your already narrowing down the speaker choices.

I was trying to figure this out today.   The amp can be run in three channel mode by bridging the front and rear channels, so by definition, it has to be 2 ohm stable, right?

Also, since Alpine provides specs for the amp at 2 ohms stereo, 4 ohms stereo, and 4 ohms mono (4 ohms stereo, and 4 ohms mono (bridged), I'm thinking that each individual channel is 2 ohm mono. 

If that's the case, then the guys at the shops were right and I was running a 4 ohm mono load into a 2 ohm mono channel.   If that's the case, then I'm probably sending somewhere in the neighborhood of 100 watts to the sub which would explain a lot.