Just as the title reads. I have been working on my system and I have a nice tube 4 channel amp. I will also run 1 amp for sub duty.
Over the past few months of reading plenty of posts and such, it seems a lot of people run their front stage with bi-amp set up. Now due to space, I really can not have more that 2 amps and a eq/cross over. I'm trying to keep everything stealthy and stock looking. Is it necessary to lose say, your rear fill due to cross over points of the front stage. Now my amp is 110 w x 4. This I feel is plenty of power. In fact for a small car, running 440 watts to the front stage seems like a lot.
The car is XR4TI. If anybody knows about this car, I would say it has the cabin room of and early 80's celica or hatch mustang. You see what I have to work with. The front speakers are (by stock sizing)4" or 5x7 depending on the mounting(I have both). This is in the lower dash at a 30* angle facing the floor. The 4" brackets correct the angle and the are facing the front, not so for the 5x7. I will be making door pods. I would like them to be sealed or vented. < does not make sense, huh. This will be driver dictated.
So basically, do I combine the the rear fill with the woofer on the front stage and give the tweeters their own set of channels or use the passive cross overs for the front and split the amp up front to back.
So you want to have active or bi-amp front stage, rear fill and a subwoofer. Is there really a problem? You just need six amplifier channels for speakers and one for the subwoofer. I would recommend to buy two 4-channel amplifiers. You can use four channels to power the front stage, two channels for the rear fill, and bridge the last two for the subwoofer. One of these should be relatively large to provide a good power to subwoofer. A high output Class D amplifier will probably work best for this. You can use two channels from it for the front midbasses and two bridged for subwoofer. The other 4-channel amplifier can be relatively "small" (e.g. 4x50watt) amplifier powering a set of tweeters and also the rear speakers.
I understand your problem. I was facing the same dilemma. I want to keep the number of audio gear in the trunk (besides the sub woofer) down to three because that's the number of power wires coming out of my distribution block, and also because I think I don't have the interest in finding the space for the fourth. One of these will be some kind of processor, so I can have only two amplifiers. Unfortunately, this means that I can't really have a mono block amplifier for the subwoofer, which can be somewhat limiting but not the end of the world. My rear speaker and subwoofer amplifier will be PPI P900.4. This amplifier provides 450watts at 4ohms in bridged mode, plenty for many subwoofers. There is also a 4-channel amplifier to power my front stage. The third device will probably be JBL's MS-8 processor.
By the way, I personally don't recommend rear fill without having any advanced processing. In my car, I will not be running rears until I get the MS-8 or something comparable. If you search the forum, there are many ways of running rear fill. Simply attenuated rear fill can be nice, but not very effective. At very least, the rear fill should be time delayed, attenuated, and probably band-passed. Sending L-R difference signal is better. One of the ways to implement this is to use the miniDSP processor. Proper surround sound processor like Logic 7 on MS-8 or Dolby Pro Logic is probably even better.
As of buying anther four channel. I don't know if this would work. I mean I know it would work for some, just not what I'm working with. Helix tube amps are not the most abundant amp around. I could go zed. I'm just not liking buying more amps. I do have some small 4 channels laying around.
So I can afford to lose refill. Now, do I need a dsp unit if only running front stage and a sub. Is a 1/3 octave 30 band ok for front stage, or something I can do separate frequencies over the 4 channels. Hmm , makes me think. I just want to spend money wisely, scene I have a few amps to work with now.
BTW, my head unit is as simple as simple gets. Rockford 8250ti. If this helps.