biamp vs uniamp

Hey all! It's been a while since I've been in here but I have ran across something that I can't determine which is correct and I was hopeing that the smart people here could help me out.

I know that when running 2 speakers off of one channel of an amplifier that the wattage is shared between the 2 speakers (assuming same impedences, etc...)

Here is where I am a little fuzzy. Lets say I have a source putting out 40 watts RMS and 2 speakers 4Ohms each. With nothing else, connecting the 2 speakers they will share the wattage. Lets say now that I connect a crossover and split the frequencies - one speaker is receiving freqs 40-3700 and the other is receiving 3700-23000. Is the wattage still shared between the 2 speakers or is each speaker getting the full 40 watts, but only at the frequencies the crossofer is letting through??

I am aware that for the same volume, more wattage is needed for the lower freqs than the higher - but let's assume just to make this simple that all freqs will be balanced in such a way that the full 40 watts is driven through the entire spectrum.

My thinking is that with the crossover in place, each speaker will see the full wattage for that freq range. Am I correct? And if not, please provide an explaination why so that I can better understand exactly what is happeneing.

Many thanks!

If you are referring to a standard passive x-over, the power is divided unevenly. Generally a tweeter is far more effecient and requires far less power, where a mid is less effecient and will require more power. Generally it's about a 70/30 split.

So in a broad way, my assumption was correct(of not 100%)? If that's the case then theoretically I would get more out of using a 2x50 amp into a pair of components with passive crossovers (a mid/tweet combo per channel) then I would a 4x25 amp already crossed over with an active crossover, or using the passive crossovers in bi-amped mode (2 channels on the mids and 2 on the tweets)?

Had to read that a few times

I personally don't think there would be much to gain or lose in either setup you have. Generally ( I like general terms) with a true active setup with proper power you will reap more benefits such as over all volume and far more flexibility for tuning based on speaker location. Basically if you had a larger four channel amp with either an external electronic x-over or simply a head unit capable of going active like an 880prs or eclipse 8053 I would opt for that.

However...the use of passive x-overs has plenty of beneifts including ease of install (very easy and great for simply apps with optimal speaker locations) the x-over, so long as it the one that comes with the set is considered the "voice" of the system.

I plan trying an all active system, soon.

Well, here is what I want to do - My wife's car has an Alpine 9856 (4x20 I think is the RMS) pushing a pair of MB Quart 6.5s in front with the musicomp crossover and I still have factory speakers in the rear. For my setup in my truck, I have a 9861 pusing the same speakers in the front and rear as hers. For my setup, I was thinking about taking it to competitions and decided I wanted a 4x50 to run my front and rears with (the rear speakers in my truck will be MB Quart by the time I get my amp).  I also have an old (still works GREAT) A/D/S/ PH 12 which is 6x22 RMS. I was toying with the idea of maybe using that to bi-amp my front speakers and have 2 channels left to run a center channel and going with a 2x50 in the rear.

From what I am gathering now, this may not be a good option unless I really turn down the rear. So, I am thinking what I will do now is keep with my original plan and just put the PH12 in my wife's car. I'd bi-amp the front speakers and run the rear full range - this should give a little more oomph than what she has now.

Does my conclusion sound solid? or am I thinking too much and just need to dump the PH12?

Thanks! This is actually helping me out quite a bit!!!!

Almost any thing is better than deck power, the PH12  is a great sounding amp, I used use a PH15 as a matter of fact. If I recall correctly, there is not on board processing on those amps, like x-overs, just gains. You had to use the 642csi electronic x-over with their propriatary 8 pin din cable. So if you are up to it, I would give it a shot as I think your deck may be capable of doing the processing. 

Those muisc comp x-overs give you the option to bi-amp, which is better to some degree but experimenting is your best bet.

Well, I have a 642CSi that I was going to use with the PH12 - the HU doesn't give many options for crossovers except for the SUB crossover freq and slope. The only thing is I need to build some crossover modules for the 642CSi to have it run ch 1/2 close to full range (probably drop it at about 60Hz for the HP) for the rears, ch3/4 for the front tweeters and set the HP at 3700 (the crossover point that is on the musicomp crossovers) and ch 5/6 (since the 642 provides LP crossover for these channels) set at 3700 LP.

As for the amp on the HU, it is astounding how good it actually does for a built-in HU amplifier. Running it with the PH12 though will allow me to add some EQ in there - although, I'll admit, not much EQ (if any at all) is really needed on her setup. But, it will be nice to have a small EQ with some presets to change for different types of music.

Thanks!