C300.2 + MM100 wiring

toygixxer

Hi, i'm new to this forum. I'm impress with "Polk's" forum users on advices to others, so hopefully you experts out there can help me with mines

I've got a polk amp C300.2 and 2 subs MM100 in a sealed box, I'm trying to hook it up to my Yukon XL stock unit. I will need to go get a line-output converter to get the signal to Polk amp. I probably wire it myself 'cuz i'm on a budget. And i had bad experience with car audio installer's "rip-offs" for crapy job in the past.
My questions are:
1) Is the amp good enough for the 2 subs for beginner level like myself?
2) Do i need a remote wire for the amp? If so, any way of doing so without tearing into the dashboard to the headunit?
3) Not understanding about the "ohm" theory. I should just wire the speaker wire straight from the sub to amp, right?!?!
4) Will any line output converter will do?

Any suggestions is well appreciated!!!!!

exalted512

your loc should have a rem wire. if not, tap into the blue/blue w/white stripe wire on the back of your radio...and no, theres no way of doing so without pulling the radio. but honestly, you drive a yukon--thats one of the easiest automobiles to take apart. depending on if its a new body style or old, its still very easy. new body style: turn ignition on (not the car, just the ignition), drop the shifter into first. pull out the trim panel that goes around your headlights, instrument cluster, and a/c controls(one big piece). there should be no wires connected with that. after thats pulled, theres two tabs on either side of the radio that you push down at the same time and pull the radio. the only difference if you have the old body style is you have to disconnect some wires on the trim piece after you pull it.

the 300.2 is not big enough for 2 mm100s. in fact, polk doesnt make a single amp that will push those subs sufficiently. If you do want to stick with all polk get the 500.1 or 2 300.2s. 2 300.2s will power them more than adequately, while the 500.1 will be pushing them about 70% of their potential. But with those subs, you have to be careful about how you power them, so the 500.1 would be a better choice IMO
-Cody

neomagus00

since you already have the 300.2, it'd be better to simply power one sub with that amp (be careful with the gains - here is a link to a tutorial that will walk you through that process). if you wire the sub this way, you will be bridging the amp into a 4-ohm load, which is all fine and dandy. any other configuration could get a little complicated, but should be no problem.

i second everything cody said, it should be fairly straightforward. make sure you set the switch on the amp to "high" when you stick the RCAs in. to save money on RCAs, run speaker wire from the outputs on the stock HU to the amp, then stick the LOC and a short segment of RCA next to the amp - foot by foot, speaker wire is a LOT cheaper .

spend a bit of money on the LOC - you don't need the top end, but you don't want to get the bottom-feeder, either, you want something in the middle.

toygixxer

I don't know if i can wired 2 amps. But if i do get the 500.1 , how do i wire it from a single channel amp? should i wire it in series or parallel? And with the LOC, i can just connect it to one of the rear speaker in the rear, without having to run the RCA wire from the head unit to the back? thanks for the tips.
-chris

MacLeod

The single channel amp is stable to 2 ohms mono which is 2 4 ohm subs wired in parallel.

So simply hook the positive of each sub to the positive of the amp and the neg of each sub to the neg of the amp and youve got 600 quality watts!

PoweredByDodge

you're better off with a single 500.1

trying to run two amplifiers off the weak signal output of a single "LOC" (line out converter) is a bad idea. those line out converters only do about 0.250 volts - with a limited current. split that off, and regardless of what its intended voltage, it's going to drop down significantly due to lack of current. i think the momo amps need a minimum of 0.250 (as do most any other amp) volts input to produce their rated output.

side note - most car audio head units (aftermarket) put out between 2 and 5 volts ... this is why we all hate LOC's on factory decks.

run one amp - a 500.1 should do... wire the subs in parallel... it's not going to drive them to their full potential, but it'll certainly do for your setup with factory speakers and factory head unit.

as far as the remote trigger wire ... if the LOC does not have one, run a "speaker wire" line from the amplifier to the dashboard... put a toggle switch in your dashboard. (there's a "cleaner" way to do this, but you dont want to open up your dash, so i'm going to keep it as SIMPLE as possible)

just drill a little 3/8 inch hole in the bottom of your dash and put a 2 dollar toggle in there (down where its not visible or ugly or anything, like by where your knee "hits" the dash jsut above the gas pedal. now take the two leads from one end of that speaker wire, and hook them to each terminal on the toggle switch (doesn't matter which is which). then, back at the amp, you've got the other end of that speaker wire... take one lead, and hook it to the "Battery +" terminal on your amp (where the big red power wire goes into the amp, just slide it under the screw so it makes contact). the other lead goes to the "remote trigger" on your amp.

what this will do is... when you flip the switch at the bottom of the dash, a connection will be made between the 12 volt battery power cable and the remote trigger on your amplifier... this will turn your amp ON. flip the switch back, and it'll turn your amp off.

just be careful - don't turn the car off and get out and forget to turn the switch off... then you MAY drain your battery over night.

the "clean" way is to tap that remote trigger on the amp into a "switched AC power" lead somewhere inside the dash (cigarette lighter power or radio switched ac power) and then have a toggle onthat as well.. that way god forbid you forget to shut it off, it'll shut itself off. but that may be too much for you at this point, and honestly, the method i described above will work 100%.

if you haven't bought the amp yet - check out a hifonics or mtx 800 - 1000 watt mono amp.. it can probably be had for the same price as the momo 500 watter.

were i to be doing a "all polk" setup, and wanted to keep the speakers and the amps the same, i'd put a C300.2 bridged on EACH MM100 subwoofer. that would give me a solid 500 or more watts to each sub... which is ideal. (and class AB for even happier listening).

exalted512

vince, what happens if you put an 8volt source(like an eclipse) on an amp that can only accept up to 6 volts? I was told amps have a built in voltage regulator to prevent damage, is this true?
-Cody

PoweredByDodge

i'm sure some amplifiers do have built in voltage regulators, others dont.

but, if your amp does not, then you simply do this...

set your gain to "0" which would be right for a "6 volt" input.

then, before hooking your head unit to your amp - hook a scope up to the RCA output, and dial that **** up (the head) - look for clipping, figure out "at what volume level" it starts to clip, then arbitrarily declare tha to be the "8 volt point" (you might want to actually take a reading of what exactly the real voltage is at that point anyway - because if its not over 6, then don't worry about it at all, and stop right here and use your **** like normal).

but, if its over 6 - then declare that point on the volume scale as the 8 volt point... divide by 4, multiply by 3, and you've got your "six volt point" - remember where on the volume dial that is and never go past it - and you won't hurt your amp. it would also be a good idea to actually test it - put it at that "6 volt point" test voltage, and see what you get... it may not be a steady ratio of increase.

anywho - u get the idea.

neomagus00

wouldn't it be a little odd to have it be a linear increase? doesn't the voltage have to increase logarithmically? so, mightn't it be easier to simply turn the gain all the way down, hook up your DMM to the preouts whilst playing a 60 Hz tone, and find the 6 volt point?

PoweredByDodge

yes sir

neomagus00

yay me

MacLeod

neomagus00 wrote:

wouldn't it be a little odd to have it be a linear increase? doesn't the voltage have to increase logarithmically?

Ummmm......huh? Do you really know what all that means?

PoweredByDodge

scratch that - i just bunked my response...lol

it couldn't be a logarithmic increase... you'd have such screwed up powers it would be ridiculous ... once you hit a few clicks you'd go from "medium volume" to "blow your speakers 10 times over".

i imagine there's some sort of curve to it but it would be just that a minor functional curve rather than a wicked log jump.

then again, it may in fact be nothing more than linear with the volume dial being nothing more than a virtual pot.

neomagus00

yes, mac, i really know what all that means, or i wouldn't have said it

pbd - i think it must be a logarithmic increase... consider that analog volume pots have a 'logarithmic taper' (cheaply implemented as two separate lines, but whatever). then consider the human ear - we hear 3dB more with twice the power, which is exactly a base-10 logarithm (i.e. log10(2) = 0.3). Throw ohm's law into the mix (P = V^2 / R) and i'm pretty sure you end up with a logarithmic curve; like you said, a few clicks would make a big jump in voltage... just with the bottom end being very very small, and the far right being whatever, 4 or 6 volts from the preouts.

edit: the voltage curve would actually probably be exponential, not logarithmic, to make up for our logarithmic hearing. then you get the small-small-small-medium-HUGE curve of an exponential function. it's all the same, though .

MacLeod

neomagus00 wrote:

pbd - i think it must be a logarithmic increase... consider that analog volume pots have a 'logarithmic taper' (cheaply implemented as two separate lines, but whatever). then consider the human ear - we hear 3dB more with twice the power, which is exactly a base-10 logarithm (i.e. log10(2) = 0.3). Throw ohm's law into the mix (P = V^2 / R) and i'm pretty sure you end up with a logarithmic curve; like you said, a few clicks would make a big jump in voltage... just with the bottom end being very very small, and the far right being whatever, 4 or 6 volts from the preouts.

edit: the voltage curve would actually probably be exponential, not logarithmic, to make up for our logarithmic hearing. then you get the small-small-small-medium-HUGE curve of an exponential function. it's all the same, though .

OK, now youre just showing off!

PoweredByDodge

... yet i still understand what he's saying... which puts me one step ahead of the average bear.

considering the human ear's perception... i think you're right.

consider this... if one volume "click" equaled a rise in preout voltage of "1 volt", also assume, for purely sake of arguement - that you've got a 1 ohm load on the end of that preout line - then... 2 would be 4 watts, 3 would be 9 watts, 4 would be 16 watts, 5 would be 25... and so on and so forth.

which, "furthermore, heretofore", leaves us with the undeniable fact (oh how loosely i use the word "fact") that it's got to be exponential.

MacLeod

Do the inputs of the amp have resistance? I never thought of the inputs having a 4 ohms or 2 ohm load or whatever.

neomagus00

yeah, yeah, exponential, logarathmic, whatever, they're both definitely NOT linear

and yes, the inputs have resistance, quite high in fact... the 500.1 for example has an imput impedance of over 10,000 ohms... i BELIEVE - and maybe pbd can help out here - that this is because the electronics in an HU work better when pushing into a bigger load...

MacLeod

10,000 ohms?!?!? How can that work.

neomagus00

yep! but the same amp only pushes against .02 ohms of its own resistance on the output side.

i believe that works like speakers do... all else being equal, a speaker with a higher impedance will allow the amplifier to exhibit a higher damping factor... i.e. if it has a damping factor of 50 on a 4-ohm load, it'd be 100 on an 8-ohm load... i have no way to back this up, but if i were to guess, i'd say that's why it's like that, to allow the HU to exert a very large amount of control over the signal it produces...

MacLeod

Is there a point where the resistance is so high that the input cant get thru?

exalted512

MacLeod wrote:

Is there a point where the resistance is so high that the input cant get thru?

at an infinite point, but not many people can reach infinity, cept for maybe buzz lightyear.

and im pretty sure it is in fact exponential but i cant remember why. ive just remember something my EE teacher told us and something i read. but why are you talking about analog pots neo? Just because you turn it and its not digitally enhanced(as to say enter it in in a electronic key pad) doesnt mean its analog, in fact, i highly doubt it.
-Cody

MacLeod

Great, now Im the only regular here that doesnt know **** about electronics.

CrBoy

MacLeod wrote:

Great, now Im the only regular here that doesnt know **** about electronics.

You're not alone

MacLeod

Good. We'll hang out and talk about all the cool lights and shiny new amps are while they discuss E=MC^2

PoweredByDodge

*dusts off his magic stick* ...

The higher the input impedance the better.

The RCA inputs on an amp most certainly do have a resistance... if they didn't then you'd have 2 possibilities.

1- infinite resistance = no signal would cross the "eyes" of the input, so you'd get jack ****.
2- zero resistance = you'd short out the head unit and fry the RCA output.

I do not know the input impedance, it depends on the amp, they're all very very high though. I imagine some are higher than others... side note - that "input" switch on the momo amps for "high power preamp" versus "low power preamp" either adjusts the input impedance or it simply scales you into another pot-like device that adjusts gain differently.

Either way - the higher the input impedance, assuming all other things equal, the better. Neo's right, the higher the impedance put onto an amplifier (or any signal source - this includes pre-outs) the higher the damping factor. Damping factor - which we hashed out before - is, in ghetto terms, a description of how well the amplifier controls the speaker. Does it "slap" itself back when it gets to its Xmax points or does it move like a well oiled piston in a shiny new Hemi - snapping back with a ferocity. Tight grip versus Loose grip.

Any who - the higher the input impedance, the more amps you can run off a single pre-out. There's not much of **** for current coming out of those preouts - so the less current you need to drop 4 or 8 volts or whatever you're using, the better. Probably reduce heat in the head a little too... although I don't think that would become a factor until you started to seriously load up a preout line (example, 4 or 5 **** flea market amps running off a single preout with an assload of Y-connectors).

I make it a habit not to run more than 2 amp-inputs off a single pre-out line.

Anyway - you'll also find that newer amplifiers - say after about the late 80's early 90's, will have higher input impedances. FET's became widely used in car audio after about that time. While BJT's do truly produce a more sonically sweet amplifier output, they're no where near as efficient as FET's. Besides that, it's much more difficult and "parts consuming" to try and declare an input impedance for a BJT input stage. A J-fet input stage can have any arbitrary input impedance you desire... keep it under a Mega-ohm if you want any real signal transfer to take place, but 100,000 ohms is feasible. You may run into issues of "analog signal dealing with **** carbon resistors" and other mumbo-jumbo that's over my head. I'm sure more savvy nerds can figger it out.

I'm vastly too tired for this **** - specially since I took last semester off and have been on mental vacation.

MacLeod

Ya done good bro. I think I actually understood that.

If I remember right, didnt you build an amp one time a year or two back?

PoweredByDodge

yes, yes, and yes.

it wasn't anything sickly powerful... i wish i could remember the spec. i think it was like 30 or 40 watts rms - i forget into what load - but nice and clean - was mono though. however it was so small it could easily be paired with another one and made into a little 2 channel the size of like double thick pack of smokes. the whole idea was to incorporate it into a head unit - so that you could quadruple it up - get a true clean full bandwidth 30 or 40 x 4 and have it be REAL rms power. in "not so many feature" headunits that dont have a lotta junk inside them, you could probably fit it in a standard din casing with the cd player and stuff still in tact (so long as it was all strategically planned out).

neomagus00

i remember that, didn't it have flat extension up to like 100 kHz?

PoweredByDodge

*scratches head* - i dunno... it was something wicked sick though - you ****, you're gonna make me go pull the file out on it aren't you? i hate you people.

i should probably build a practical field testable prototype as opposed to the sloppy work bench-sticken original. i can put it in giant shoe boxes and leave the wires hanging out - sell it to kids who want to hook up 4 Kraco (Crack-Ho) 15" subs and shizzle.