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Discussion Starter #1
Hello all,

I have a "new to me" 2015 Mazda3 Sport and have upgraded the audio system. I've had it about 2 weeks so am not familiar with the expected behaviour of the electrical system. The audio setup is an MTX TC4004 which is rated at 50WX4. I have a single JL Audio 10W3v3 that's getting about 200 watts from the amp when bridged and a set of components for the front stage. It's not a crazy sound system. I've got 4 gauge cable running to the amp from the battery and 4 gauge grounded to a bolt holding down the rear seat. I sanded the metal so it was bare it it seems like a good, strong connection.

However, I took the car out last night. It was cold (-19 degrees celcius). Drove it around for about 15-29 minutes to warm it up and was driving on a dark road and noticed that the headlights were dimming to the bass, worse at louder volumes.

Headlights were on, heater was at the middle setting.

So I'm curious. Those who own Mazda3's and have done system upgrades, is this something to be expected with the electrical system or is it possible that something's not quite right?
 

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I don't have such a system, but the indications are it is drawing more power than your alternator / battery can handle under those circumstances.

You might get a voltmeter to see what it reads with and without the sound system operating.

A 200 W / 16.7 Amp load is not insubstantial, but I would guess it should be OK. Are you sure it's 200 Watts? A 4-gauge cable implies a pretty big load.

Is your battery in good shape? Does your car start OK?
 

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Discussion Starter #3
I don't have the birth sheet, but the TC4004 likely puts out 10-15%% more than spec. So It may hit 250 watts and then another 50 to each of the component sets up front.

4 gauge is because I always run a large cable in case I get bit by the bug again (used to have multiple PPI amps, Blade Amps, and higher end equipment). These days it's more or less entry level stuff.

Car starts okay. The amp has (2) 30 amp AGT fuses and it's a class AB (I believe) so not a Class D monoblock. So not as efficient. There doesn't seem to be any performance hit...
 

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Something I've noticed which may or may not be odd. During the daytime with only the daytime lights on, the interior dome light also flickers to the music even when not playing at a high level. Volume increases and the dimming becomes more apparent, but it seems odd to me. I also noticed that when I rev the engine while in Idle, the dome light brightens and then dims back down after a fraction of a second almost like it's spiking and then being regulated.
 

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Discussion Starter #6
Okay, went to Partsource and they did a battery, starter and alternator test.

Battery when car was off was 12.43 volts
Starter was good
Alternator came in at 14.3 when running.

So I did some additional testing. When the stereo is running and the heater is off and the dome light is on, the light dims to the bass when at a semi (not even loud) level. When I turn up the volume, it dims more. If I turn on the headlights and crank the heater up to full, it doesn't seem to make much of a difference. The dimming is approximately the same.

Thoughts?
 

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Since you've reported the headlights and interior lights are dimming only when the stereo system is playing, I have to assume this indicates the stereo load is too much for the battery and alternator to handle.

It would be interesting to know what the voltage is when the lights are dimming with the stereo playing. Obviously, it is dropping enough to see the effect via the dimming lights.

I will say that the 12.43 battery voltage level with the engine off implies the battery is not fully charged, and/or is declining in health. At rest with no load on it, a fully charged battery should be closer to 12.6 or 12.7 volts or thereabouts. However, if the battery is tested without removing it from the car, there probably is a bit of a load on it even with the key off, which could explain the voltage level, at least partially.

Did the guy who tested your battery put a load test on it to see if it passes muster? Such a test can detect a dead cell or other serious battery problems that a voltage test can miss.

The system voltage of 14.3 with the car running sounds normal, especially in cold weather when the charging system likes to maintain fairly high levels.

As I noted, I don't own such a powerful stereo system. Perhaps another poster can comment on the effect theirs has on their Mazda3.

Personally, I think the dimming lights is a warning sign that something is not up to par to handle the load.

An added thought: could it be the stereo system has some sort of internal fault which is causing an extraordinary load? An ampere meter could tell what the stereo system is drawing. On the other hand, since it is not blowing fuses and assuming the fuses are properly sized, this may not be the problem.

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Hi,

I have 4 amps in my Mazda 3 on stock electrical and I experience no dimming.
I suggest you turn off bass boost on your amp and play with the gain settings until dimming is disapeared or very little.
 

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Discussion Starter #9
Hi,

I have 4 amps in my Mazda 3 on stock electrical and I experience no dimming.
I suggest you turn off bass boost on your amp and play with the gain settings until dimming is disapeared or very little.
Bass boost is off but I did adjust the gains so that full volume would be achieved at around 50% HU volume (to help compensate for the bass roll off of the HU that apparently exists). However, I'm not understanding the science of how the gains would affect the dimming if the sound output ends up being the same?

I always thought that the gains were best to be as low as possible for the least amount of noise. In this case, I do have them turned up higher than I normally would so this is an interesting possibility. Are you suggesting that if I turn the gains down, but turn the volume on the HU up that the dimming may decrease?

I'll make the changes and report back (Out of town the next couple days though).
 

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Discussion Starter #11
Hi,

I have 4 amps in my Mazda 3 on stock electrical and I experience no dimming.
I suggest you turn off bass boost on your amp and play with the gain settings until dimming is disapeared or very little.
So I adjusted the gains. I have a PAC AOEM-MAZ2 with the gains turned way down (the way it was from the factory pretty much) and turned the amp gains down (though the sub requires the gains to be somewhat high for some reason to be audible). Not sure why fronts can be set really low while the sub requires it to be high.

There may have been a minor improvement in the dimming, but it's still there. Though I don't believe it to be nearly as bad. I'm wondering if it may have something to do with the PAC?
@DanB0yDro, what kind of line level converter are you using (if you are?)
 

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Discussion Starter #12
So I've tried a new ground and replaced the cable coming from the battery to the fuse (8").

It was 4 gauge from my previous vehicle, but it appears like it was actually 8 gauge wrapped in a 4 gauge piece of plastic. That's now been resolved so it's true 4 gauge from the battery to the amp.

I've also adjusted the levels. Neither items have made a significant dent in the headlight/dome light dimming issue.

I also tested with a voltmeter on the battery with the audio cranked. It's consistent between a little higher than 13 volts and 14.2(or so) volts. Never saw it dip below 13volts even with dubstep music and consistent bass.

Is it safe to say that the voltage is what's affecting the dimming? I mean, I guess that's the difference between unregulated and regulated power supplies. Headlights, etc aren't regulated so they'll brighten and dim with whatever voltage they can get? Is that correct?
 

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Audio-SQ-Maniac
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So I adjusted the gains. I have a PAC AOEM-MAZ2 with the gains turned way down (the way it was from the factory pretty much) and turned the amp gains down (though the sub requires the gains to be somewhat high for some reason to be audible). Not sure why fronts can be set really low while the sub requires it to be high.

There may have been a minor improvement in the dimming, but it's still there. Though I don't believe it to be nearly as bad. I'm wondering if it may have something to do with the PAC?

@DanB0yDro, what kind of line level converter are you using (if you are?)
Your highs gain dont need to be set high because these speakers have higher sensitivity vs the sub: They go louder with the same amount of power. Sure, your sub can probably go louder than the fronts, but it will require multiple times the power to do so. Also, our ears dont hear every frequencies at equal loudness levels (google Fletcher-Munson) so you need WAY more power on a sub stage vs a tweeter. If you raise the gains to get around that, you will get voltages drop and dimming.

I dont have a line level converter, here is my build:

http://mazda3revolution.com/forums/2185954-post192.html
 

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Discussion Starter #14 (Edited)
Your highs gain dont need to be set high because these speakers have higher sensitivity vs the sub: They go louder with the same amount of power. Sure, your sub can probably go louder than the fronts, but it will require multiple times the power to do so. Also, our ears dont hear every frequencies at equal loudness levels (google Fletcher-Munson) so you need WAY more power on a sub stage vs a tweeter. If you raise the gains to get around that, you will get voltages drop and dimming.

I dont have a line level converter, here is my build:

http://mazda3revolution.com/forums/2185954-post192.html
Fascinating. That's a good amount of equipment to be experiencing no dimming. Very helpful in my troubleshooting, thank-you. And because you have a 2018, I suspect you're using the stock battery?

I figure my amp is likely drawing no more than 40 amps max. Even still, your sub amp can draw more and if the power system is stock, then it must be something in my setup. Did you do any upgrades to the Big 3?

[edit] - just re-read thread and you you said "stock electrical and I experience no dimming." - so no big three upgrade.
 

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Discussion Starter #15
So I disconnect my HU and connected the amp inputs up to my iPhone headphone jack. Kept the levels where they were which worked quite well for the gains where they were.

No difference. Still dimming. I think I may try to swap it out for a different amp and see if that affect things better?
 

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Audio-SQ-Maniac
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Yeah, no big3 upgrade.
My battery is a 150$ AMG.
I had a 2014 Mazda 3 sedan before that with pretty much the same setup, with stock battery, and dimming was minor under very heavy use (135+ decibels)
 

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Discussion Starter #17
Yeah, no big3 upgrade.
My battery is a 150$ AMG.
I had a 2014 Mazda 3 sedan before that with pretty much the same setup, with stock battery, and dimming was minor under very heavy use (135+ decibels)
I actually had a 2014 Mazda3 before as well with the exact same setup and didn't notice it as much (if at all).

I bought the car second hand and apparently the previous owner had a pretty beefed up system. I was wondering if they had prematurely worn out the battery or alternator with their usage.

Another user mentioned a Kinetic battery, but I wanted to eliminate any other possibilities first (wiring, levels, etc).

So my dimming could very well be resolved with an AGM battery...
 
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