Amp

grizlee · June 2005

I want to pick up the MMC5250 and the MMC690. Both sets are rated at 100w and 4 ohms. Can they handle 2 ohms? I have yet to see a 400 watt amp that will push 100wx4 at 4 ohms. Also will my deck which pushes 40wx4 additionaly push power to the speakers even with an amp?

-Zane

coldrealms · June 2005

A speaker is rated, ohm wise, based on the resistance load it places on the electrical lines. wiring 2 4 ohm speakers will present a 2ohm load (parralel) or an 8 ohm load (series) to the amp but that is not an ideal situation given the loss of fader control and doubled distortion values.
I would suggest, and so would many members here, that you ditch the idea of the rear fill speakers and bi-amp the 5250's with a 50x 4 amp or 75 x 4 amp (like the polk c400.4). You will get better quality sound without the hassle of rear speakers for stage balancing and other SQ issues.
As for your other question, no the deck's power (which is never quite what it's rated) does not add to amp power.

grizlee · June 2005

So ditch the rear speakers all together?

coldrealms · June 2005

Yes, unless you usually have people in the back seat and want to cater to them. Otherwise save the hassle and focus on front stage.

grizlee · June 2005

Would I even need a 400w amp to do that?

coldrealms · June 2005

Nope, not really. But the more power you have availiable the more headroom you have for clean sound. The speakers you have for the front are rated at 100w RMS and 200w peak per speaker. So trying to hit 50 watts per channel on a 4 channel amp just barley fits the bill if you bi-amp. the polk c400.4 was made for this setup on the mm6's (last years model) so if you return the 6x9's and use the $$ to get that amp you'll be set. As the mmc series is rated a tad lower on power handling just set the gains sensably and you'll be fine.

grizlee · June 2005

I didnt buy anything yet I am just double checking some things before I go through with it.

My original setup was going to be

Kicker 2 12" Solo Baric L7s
Kicker 1200.1 Class D Mono Amp
Polk MMC5250
Polk MMC690
?? ?? 400.4 Amp
Tsunami Power Cables
Monster Cable Audio Cables
Panasonic CQ-DF88EUC Head Unit

coldrealms · June 2005

Ahh i see, well the kickers I don't have an opinion on, keep the 5250's and the polk c400.4 and just forget the 690's.
One thing though... I am assuming that mono block amp is 1200 watts? If so that plus the 975watts of the c400.4 adds up to 151.12 Amps of continous power draw. What type of power upgrades are you planning to do?

grizlee · June 2005

No idea, any suggestions?

MacLeod · June 2005

The reason for not going with rear speakers is strictly for imaging. Having speakers in the rear can make your soundstange move to the rear and you want it in front of you.

However theres not really anything wrong with rears especially if you have a bigger car and haul a lot of people around and want some speakers back there for them.

That being said, the Polk 400.4 amp makes about 90 watts per channel so it would be a perfect match.

Bi-amping is my favorite way to run speakers as it offers you much more felxibility in tuning the output of your tweeters. But the MMC crossover has an attenuator that can either be set at 0db, -3db or -6db so even if you straight wire them youll have some tuning flexibility, just not as much.

Those L7's are bad ****. Pound like a **** and sound very good. Youll like em.

coldrealms · June 2005

Well that depends on your current power output on your alternator. I would suggest looking into a High Output alternator upgrade or even a second alternator depending on what you preferr / what you can find on a good deal. Replacment would be easier and I think they can be had up to 200 amps though it may be much higher then that. Just be sure to get one that hit's it's peak at low RPM's not at high rpms. Might also want to look into a yellow top optima battery(or two) if you ever want to run it without the car being on. Wait on getting a cap until the rest of the electrical system is upgraded, if after that you notice sever dimming of the lights or other odd things (usually timmed with bass hits) then we can discuss capps and such.

grizlee · June 2005

Where would the best spot be for the crossovers?

coldrealms · June 2005

Depends, if you use the c400.4 and just the fronts the amps crossovers are much better, if your going to keep the rears or use a different amp anywhere but in the doors (water and such) they look nice and so should be mounted somewhere that looks nice, but their physical placement will be a matter of preference.

MacLeod · June 2005

975 watts of the 400.4????

360 tops!

You dont need a cap. Also, dont get a Yellow Top. They are just too unreliable. Search around the forums and youll read plenty of gripes about them with little praise.

Unless you have a 40 amp alternator your stock alternator will more than likely work. The thing most important is the battery.

coldrealms · June 2005

Like I said cap is last resort, and the 975 was taken from peak power draw according to the polk website.
And as I said it all depends on his current alternator output.
Either way at the 360 watts thats still 109 AMPERS of draw (both amps), thats ALOT of power draw to ask of a stock alt, don't you think?

MacLeod · June 2005

The amp will pull its power from the battery. The alternator only charges the battery so as long as he has a stout battery he'll be fine.

Ive ran many systems over the years and have never used anything more than a Sears Diehard or Duralast. Never had a problem.

Plus, an amp will probably never draw its max ratings. This is especially true with peak ratings and the fuse ratings.

Amp

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