mostly OT: bass diminishes under acceleration

G-Forces? Quantum physics? doppler effect?

Seriously, if it 'fades', either a bad power connection or bad amp. See any drop in voltmeter while accelerating? If so, either engine ground or alternator

Nah, sounds MORE like the engine is taking the power it needs from the available power output from the alternator, thus decreasing the amount of power going to the amp. Then when it doesn't NEED all the electricity it goes back to where it was, thus increasing the power to the amp. Try a capacitor in the power wire before the amp and that'll fix it since now the power will be sucked from the cap (power storage) while the alt is under a greater load, thus allowing the power to flow uninterrupted to the amp.

I was thinking of the noise-cancelling effect of the exhaust pipes. Unless proven quantifiably, the bass isn't going away - just being overpowered by a similar sound in the same general range.

dwight

I was wondering if something like that was going on, but I didn't think the engine's draw on the electrical system would increase under acceleration; maybe it does? And even if something like the fuel pump was drawing more power, it doesn't seem like it would be enough to sap the bass.

I wonder if this is a sign my battery is on its way out...

Yeah I wondered about that too. I did some experimentation and it happens even in 5th gear at moderate speed, where there's no real change in exhaust sound or volume. I know that the low frequencies bounce around the car a lot before they make it to the ears, and my first thought was that something was changing the bounce angles - such as the sub box moving around (but that wasn't the case). I wish I had a way to measure the amount of movement in the driver, to see if it really is petering out.

I need to go out and see if the voltage is dropping under acceleration. If that turns out to be the case, what would cause such a condition? Doesn't an alternator always produce more juice as the rpm's go up?

And what about the idea of the engine pulling more power from the electrical system under acceleration?

The battery has nothing to do with it. It takes more electricity through the coil(s) and more energy to spark the engine when your RPM's go up. Remember the your increasing the number of times it has to fire those plugs as the engine RPM increases thus taking more available power away from everything else.

Kinda the same principle as the really low amp alternators. When you turn the headlights on and the bass makes the headlights dim?!?! SAME THING! Just reversed, the engine is taking the power away from the amp.

Yes, until it reaches its peak output. If you are asking for more power than that, (70 amps or 120 amps or whatever your alternators peak output is) then you will see anomalies like you are experiencing...

Do you know what the max amp draw is for your amplifier?

Without knowing the specifics, your cars electrical system doesn't have unlimited capacity. It is probably not able to supply power much beyond what the car requires from the factory with no add-on accessories..

I once had a van, with two batteries, and a high output 140 amp alternator, that at highway engine speeds, would immediately drop from 13+ volts to around 10 volts when I turned on some big very power hungry after market lights.

That is not exactly right... I told the guy to watch his voltmeter. That would tell the tale, right there.

If his voltage goes down when he accelerates, that's a sign of a bad alternator

He could ALSO easily check to see if bass dies out when he turns engine off.

Bass is fine with engine off, running with key in accessory position!

The amp is 300W rms so it should be about 25 amp draw. I don't doubt that I'm exceeding the capacity of the alternator; what I don't get is why it only happens when my foot is on the gas.

I wasn't exactly correct when I said it happens when I'm accelerating; it's when the engine is under load. If I'm in 5th gear and going up a little hill, at fairly low speed like 45, and I step on the gas the car doesn't accelerate (well not much anyway) but the bass goes away.

That's because it's sucking everything from the battery and there's nothing else drawing power EXCEPT the stereo. Nothing occasionally draining the power away.

"JohnV@nn" wrote

At full blast maybe. I doubt you have the gains turned ALL the way up.

Because, as I said, the engine is drawing the power and the amplifier is getting starved.

Again, Same exact thing I've been saying all along. Go to a mobile electronics store and explain the problem. They'll give you a lot of bullshit and try to sell you a buncha shit you don't need. What you need is at least a 1/2 farad capacitor OR a bigger alternator.

Whaa??? Whilst idling or even under acceleration and engine should not be drawing anything from the battery. The battery should be charging at that time. If anything an amplifier should be able to draw more power while the engine is running since the alternator is going.

Where are you getting this? The engine should never draw more power than the alternator puts out or there is a problem somewhere.

Unless your engine accessories, and amplifier are drawing more power than the alternator can put out.

Like I already posted elsewhere in this thread, I once had a van, with two batteries, and a high output 140 amp alternator, that at highway engine speeds, would immediately drop from 13+ volts to around 10 volts when I turned on some big very power hungry after market lights.

Are you not aware that your alternator only makes so much power? Most automobiles do not come from the factory with much more electrical system capacity than they require to operate. If someone goes about adding a bunch of power hungry accessories, they can easily call for more power than their alternator can supply! You do get this right?

If you are trying to use more power than the alternator makes, then all of your sysems start suffering from a lack of power problems. This can be easily witnessed with a simple volt meter. Check my other post on this thread about the van.

HOW MANY times do I have to ask what your voltmeter is saying when this happens?????!!!!!

I'm sorry I haven't answered your question yet but I haven't driven the car since you asked. I'm going to take it out later just to test this.

Thanks for your help.