Speakers and Crossover.

[jrz126]

I just bought some new speakers for my car, It's a nice set of components (a woofer, tweeter, and external crossover). These will be the new front speakers in my car and they are capable of 125Wrms. My rear speakers (4 of them, I added 2 below the back windows), were purchased from a truckload tool sale for 10 bucks, they can only handle 40Wrms. They all have a 4 ohm load.

I'm going to power them all with a 2 channel amp, (L R channels). How do I go about hooking them up so I can get plenty of power to the fronts while putting less power to the rears?

One idea I had was to connect the 2 rears (per channel) in series then connect that in parallel with the front speaker. Initially I thought this would solve my problem but the external crossover is passive, so once I put some power into it the resistance will go up, which could force the power to go through the rears. Is this a correct assumption?

I think I will only need the rear speakers for when I have people back there, so I'm going to wire some relays so that I can turn them off when I want.

 

[MonkeyMera]

The best option is to have the rear speakers runnung off of your head unit (car stereo) and the fronts running off of your amp, you can then tweak the controls from the stereo to have the rears a bit quieter, wire the fronts up using the crossover as it will split the frequency to the mid and tweerters for clearer sound, i'd leave the rears on perminatly as this will give you as fuller sound stage through the car.

if you put the speakers in series you will be effectivly creating a 8 ohm speaker from 2 x 4 ohm speakers and the amp is set-up to give you a 4 ohm signal, so you will loose sound quality and power,

or you could buy a 4 channel amp and run 2 sets of RCA's from the head unit for front and rear.

or buy another 2 channel amp and put a switch on the remote cable fron the head unit so you can switch off the rears

personally the top idea is what i would do

 

[jrz126]

Forgot to mention that the amp inside my headunit blew, but the RCA's still work, with some added alternator noise :roll:.
The amp I'm going to power these with is a Kenwood 600W (150-200Wrms?/channel)

ooooo I just remebered that I have a cheepo 50W max, probably 10wRms :lol: rat shack amp in my garage, that'll give the rears enough power to suit my needs. Now as long as I havnt blown the RCA inputs to it, I'll be ok.

Uggg. another thing to do...

 

[MonkeyMera]

Forgot to mention that the amp inside my headunit blew, but the RCA's still work, with some added alternator noise .
The amp I'm going to power these with is a Kenwood 600W (150-200Wrms?/channel)

Doh!!!

where are your RCA's and power cables running? they should be as far apar as possible and the RCA's as far away fron the gear box as possible as well, if your still getting noise you can buy a noise suppressor, they dont cost much, thats a bit over kill amp, you will have to wind the gain down to about 2/3rd if you use any more you will blow the speakers and/or it will sound rubbish.

ooooo I just remebered that I have a cheepo 50W max, probably 10wRms rat shack amp in my garage, that'll give the rears enough power to suit my needs. Now as long as I havnt blown the RCA inputs to it, I'll be ok.

yeah that should be ok

 

[jrz126]

My power wires are going down the pass side. (a 4 gau. and a 6 gau :twisted: ) and my rcas down the drivers side. I bought a suppressor, doesnt work though. I'm going to buy a power filter for the head unit eventually, a small one will do the since the player only draws 720mA.

The speakers i just bought are 125Wrms (200 max i think), and with no other speakers it'll be connected at 4 ohm which mean it wont draw the max possible. And that crossover in there is going to consume some of the power as well. I wouldnt adjust the gain past 2/3 anyway, you're just asking for distortion if you do.

I also have a 1000W (709Wrms) class D amp pushing the 2 12" kickers in the trunk. they give off a mean rattle :twisted:

 

[MonkeyMera]

Have you tried a supressor diirectly on the alternator??

have you had you system SPL'ed i got 142DB with 2 atomic 12" subs 600wrms and a kenwood 1200rms D class amp

im going for more power with some alpine X types pusshing 1000wRMS and 2 1000Wrms amps

 

[Nigel Goodwin]

As long as the speakers are honestly rated in RMS watts, I can't forsee any problem - a car is a very small space, these stupid amounts of power (if they ever exist) would permanently damage your hearing in a very short time. You also wouldn't be able to drive the car, as even a moderate amount of power would be above the threashold of pain!.

As long as you keep the volume at a sensible level, you shouldn't exceed 40WRMS to the speakers.

 

[martinH]

Have you tried a supressor diirectly on the alternator??

have you had you system SPL'ed i got 142DB with 2 atomic 12" subs 600wrms and a kenwood 1200rms D class amp

im going for more power with some alpine X types pusshing 1000wRMS and 2 1000Wrms amps

Run the + supply to the amp direct from the battery(with a fuse at the battery end).
Keep the earth wire as short as possible, connect it to the bodywork of the car,

 

[jrz126]

Have you tried a supressor diirectly on the alternator??

have you had you system SPL'ed i got 142DB with 2 atomic 12" subs 600wrms and a kenwood 1200rms D class amp

im going for more power with some alpine X types pusshing 1000wRMS and 2 1000Wrms amps

No i haven't thats what im looking to buy, but if I get one for the alt, it'll have to be capable of 60-80amps, where as for just the cd player (I'm assuming this is where the noise is coming from b/c of the blown amp) it will only need to handle 0.72A.

And I havnt gotten meterd, I dont really want to know. I'm afraid it will be too low , then I'll have to spend more money to get a better system. I had a ported box in there, 2.5 cubes per sub and a port tuned to 32 hz. It was louder than my fiberglassed box (sealed) that I'm using now. (check it out in the www link at the bottom of my post).
But I'll give up a few Db's to get my trunk back and for the looks of the glassed box as well 8) .

What kind of box are you running those atomics on? if you havent already, you should look into making a slot tuned box, you'll be able to squeeze a few more Db's out of them.

 

[MonkeyMera]

if its a whining noise then its more than likely comming from the alternator, you would get it if your head unit was working propoely with the amps, the interference is comming down the power cables from the battery, you can either put a supressor on the alternator, change the alternator, or change the power cables, you should only have 1 cable comming from the battery, the split it close to the amps, that minimises noise from the engine bay, check the route that the cables take from the battery to the cabbin, make sure it goes no where near the alternator or any other mechanical part, ( i know it and egning but see if you can get the cables as far away as poss for most of the engine.

the other possibility is its gear box whine, i had it but thats cos i put the RCA's near the grear box, a quick and easy test is run the RCA's from the head unit out side your car and to the amp that way, then you can tell if it is gear box or alternator.

is your car front wheeled drive or rear wheeled drive, cos if its rear you could be getting noise from your Diff. try the RCA out of the car thing first though

 

[stevez]

I was struggling with some rather severe 'alternator noise' - 80% of the problem was a failed diode in the alternator. My electrical system did not draw enough power for me to miss the alternator capacity. Filters helped but once the alternator was repaired it was much easier to deal with the remaining noise.

 

[jrz126]

Could I have a failed diode? I've noticed that the lights dim pretty good when the bass starts. It's only when the subs first start to hit too (like for a long bass note, they will only dim at the beginning).

I took it to advance auto, they have a battery/alt. checker. I think it said everything internally turned out ok, but it was only putting out either 60 or 80 amps max. (it should be around 100 amps). So I dont have the full capacity.

Maybe I should just go out and but the HO alt. from excessive amperage. They say it'll put out 200 amps.

 

[Gaston]

i have had the same problem with a bad diode in my alt.it made a severe noise

 

[jrz126]

The crossover is nothing like what I expeced. I thought it was fully adjustable for the woofer and tweeter, turns out there is only a switch for the tweeter for -6,-3,0,+3 dB. I'm kinda disappointed in that but they sound 50x better than my truckload toolsale specials.

Oh yeah, I wouldnt recommend trying to put 6.75" speakers in a spot which is meant for 5.25". Nothing a dremel and angle grinder cant handle though. And I have about 1/8" gap between the window and the speaker when I put the window down.

Well back to working on it, just thought I'd share my story of butchering my car

 

[Juglenaut]

Why in the world would you tune a box for 32 Hz, let me guess a rap fan right.

I tuned my 3 cube (1.5 side by side) with 4 inch ports to 60 Hz with a curve favoring upto 100Hz then it drops steady down to 500Hz after that anything higher is rejected. I worked mine to respond upto the start of midrange. Responds to: lower than 60Hz at -5dB per decade, higher than 60Hz -2dB per decade

I have 2 AudioBahn Alum 10 running of a Kicker ZR600 at 6 ohms mono (each DVC is wired for 12ohms), 2 rockford 150w 6x9's running off a Kicker ZR360 at 4 ohms stereo, 4 Infinity referance series components 8ohm running off one ZR240 at 4 ohms stereo (2 wired parallel to one channel). I have made 8 array's of 180,000uF each wired in to stiffen voltage in different areas of need.

I don't know what the power is of my system all I know it sounds good and has a decent threshhold.

Most all alt are full wave rectified, if you lose one diode the alt turns into a half wave rectified which requires double the amount of filtering to maintain the DC voltage and most voltage regulators these manufactures use have built in filtering for a full wave signal. Since the voltage produced by the alt windings is by comparison a large ratio to regulated voltage output so very little cap filtering is required to get a stable DC output.

I suspect a voltage negate to near zero point going through the positive so this can be tied off if you stiffen the DC voltage, filter in respect to ground as close as you can get the the regulated supply.

In stead getting a ________straight line DC, the alt is putting out a __ __ __ Pulsed DC

 

[MonkeyMera]

you need a power cap, whats happening is that when your bass kicks in your amp need more power it need 14.4v on its own, the standard battery and alternator cant cope with that sort of demand and starts taking power from other parts of your car IE lights etc. so you need to put a power cap in, a minimum of 1 farrad. it will also give you more volume and a more stable bass note cos the amp is working to its optimum power, but you only put this on your sub amp only.

i would check out for the noise is your earth points, this can also generate noise if you had a bad earth, there needs to be no paint or grease where youve earthed your amps and 1 earthing point per amp as well cos you can get a sort of feed back through the earth cable

 

[jrz126]

But once the cap is drained from the long bass notes, won't it draw the same amount of current to charge back up? If anything I'd spend the money on a High output alt. or a second batt.

 

[Juglenaut]

Regardless where you put a cap the capacitance is electrically the same throughout the system.

What drives inductive loads really well or great for that matter?? Are capacitors.

Since the subwoofer system has a inductive load and the amp itself is a load, this can be figured for continous resistance from a given current, and the supply voltage at RMS. This resistance most times reflect the ohm load at the speaker output. Time constant R*C> 4ohms * 1F is four seconds. Which in turn means that the cap will no longer keep the DC at peak value as soon as it hits its time constant. All the current will be drawn over the amps and speakers, so yeah extended periods of extreme bass will cause the the RC time constant to drain away as the cap slowly drops down in capacitance because less voltage will be able to charge it. The amount of time for a 1F cap to charge is almost instant as the opposition to the battery is minimal.

The voltage drop will not happen all of a sudden, draining the stiffened DC supply to max current capability you will see a gradual slope, draining a unstiffened DC supply at max capability you will notice a drastic curve or even a wave form mimicking the loaded (bass hit) and unloaded phase of operation.

Buying just any car battery will not do the same job as one made specifically for high drain, even if you did get a regular car battery and hook it up which most likely is parallel the capacity of the battery is nearly doubled not necessarily current capability and the weaker battery is a load to a stronger battery. A deep cycle battery is needed one that can deliver huge amounts of amps with out dropping it rated voltage and these batteries are not cheap.

I would still go with caps as this will also filter noise, which most batteries don't do filtering.
A high output alt is the only other real solution, but even then you may still want to uses some caps to stiffen the output some.

 

[MonkeyMera]

Exactly what Juglenaut said,