Multiple impedences on a 2 ch amp?

Hey,

I'm setting up a budget system... I've bought a 2ch phoenix gold 350 w amp off ebay, I'm hopeing to hook my 4 midrange speakers up to it, plus a 10" sub. I was planning on wiring all 4 speakers up to one channel (2 in series (8 ohms), then those pair to parrallel = 4Ohms). Then hooking to sub up to the other channel. Is it possible to get a dvc sub, wiring it to 2 ohms and driving that to get more power to the sub? What do you think of this setup?

Maybe my how I wrote my post was not quite clear enough, sorry about that. Just got busy with a customer and his new turbo WRX. How I have setup this is as follows.

your 2 channel amp is running in two channel mode at 2 ohms for your midranges. Now for arguements sake lets call the amp 30watts rms x2 and 350w x1 in mono.

By wiring the 4 midrange speakers in parallel, this will create a load of 2 ohms stereo. See the parallel wiring guide on this site. Again for arguements sake let's say that at 2 ohms stereo your amp makes 60watts rms (root mean square), therefore each midrange will see 30 watts each.

By wiring the sub to the bridged output, I chose a single voice coil sub for a specific reason. You don't want to unbalance the amp and you don't want to work it to death. A 2ohm mono load by the sub more more than likely put the amplifier into protection. Even though yes you get more power, but the trade off is for how long. I am not a Phoenix dealer so I do not know it's exact capablities, however I do deal with the distributor and can check Monday AM PST.

Do not use the bass boost. It affects all of your speakers, the reason for the caps on the smaller mids is to keep the damaging bottom end from being reproduced, if you use this bass boost it will cause your smaller speaker to play frequencies that may be damaging, unless the bass boost is parametric, which I do not believe it is. As far as the passive crossover for the sub, the inductor I talked about (probably 6mh) is a passive crossover and you will need to install it on the positive lead going to the sub.

Let me know how you make out

OK, so you want to use a 2-channel amp and run 4 mids off, say, the left channel and a sub off, say, the right channel?  Sure, you COULD do this.  Be sure to give each channel a mono input, and be sure you are using the proper crossovers.  I suggest a low pass for the sub and a notch filter for your mids.  The filters could either be mono active crossovers on the line level input side or passive filters on the amp output side.  Also, wire your speakers to give the amp the lowest safe impedence load it is rated for.  Look at the amp ratings and if it is rated at 2 ohms stereo, that is essencially what you are doing.  Realize you cannot acheive stereo with this limited setup.

Now, while I say this CAN be done, it is not a very good idea.  I would not recomend it if you are looking for sound worth listening to.  Most lower quality (like Phoenix Gold) amps have sufficient cross-talk between channels that you may end up with terribly muddy and noisy mids.  The power draw from the sub may color the mids as well.  Stereo 2-channel amps are NOT a set of seperate mono amps in the same chassis unless the amp is very high quality (like McIntosh.)  Cheaper amps share components, especially power supply components and often things like pre-amps and sometimes even output amps, and this leads to cross-channel noise.

You'd be much better off to save up a few more pennies and find another amp on eBay to run your mids in stereo.  Good luck!