Subwoofer is much louder when car is not moving.

S

StayGoldPonyBoy

Audiophyte
Okay so I installed a single 12in subwoofer a while back, nothing special, it's a pioneer TS WX1210A with a built in amp. It's at least twice as loud when the car is not moving. Does not matter if the car is running at idle or off it's still way louder when stationary. I have tried revving the engine in neutral when stopped it still stays loud. I can pull up to a stop light and the thing shakes the car, start moving again and suddenly it's nowhere near where it was. I have a 90amp alternator, the lights do not dim when the bass hits. Battery is a Napa legend, nothing special. Sub is inside the cabin of the car in the back seat, it's a Honda prelude so pretty small cabin. I thought it could be some weird issue with the battery or alternator but if so wouldn't it be louder or quieter when the car is off? Anyway any thoughts would be appreciated.
 
tyhjaarpa

tyhjaarpa

Audioholic Field Marshall
You realize that this is a home audio forum? Have you measured the difference with SPL meter? Could it be that you just don't feel it the same when car is running and vibrating?
 
Pogre

Pogre

Audioholic Spartan
You realize that this is a home audio forum? Have you measured the difference with SPL meter? Could it be that you just don't feel it the same when car is running and vibrating?
That's what I was thinking. Road noise, engine, bumpy road... it all adds up and influences how you hear. Measure with a SPL meter might clear things up pretty quick.
 
highfigh

highfigh

Audioholic Overlord
Try reversing the polarity of the wires from the amp to the sub. The way it is now, the sound from the car is out of phase with the sub and it's reducing the level or it's loud enough that it's masking the sound from the sub. A car has its own noise signature and if you have a way to measure the car's response, you'll see that much of it is in the same range as your sub, which means the power to the sub needs to be greater than it is now because it's not able to overcome the car's sound. You can also try a lower Low Pass crossover frequency, to reduce the overlap. Since the car is already producing the frequencies between the new LP setting and the High Pass, you won't notice the lack out output from the system. 60Hz is a good starting point on the Low Pass and 120 is a good starting point on the High Pass. It doesn't seem to make sense when reading it, but in practice, it works pretty well.

What make and model of car?
 
S

StayGoldPonyBoy

Audiophyte
Ok thank you guys. No sorry, I did not realize this was a home theater forum lol. Car is a 1994 Honda Prelude Si. The sub has a phase switch normal and reverse, is that the same as physically reversing the polarity of the wires? And I will try your low pass and high pass numbers, thanks for the suggestions.
 
Pogre

Pogre

Audioholic Spartan
Ok thank you guys. No sorry, I did not realize this was a home theater forum lol. Car is a 1994 Honda Prelude Si. The sub has a phase switch normal and reverse, is that the same as physically reversing the polarity of the wires? And I will try your low pass and high pass numbers, thanks for the suggestions.
Yeah, but we have a couple guys familiar with car audio. @highfigh knows his stuff.
 
lovinthehd

lovinthehd

Audioholic Slumlord
Ok thank you guys. No sorry, I did not realize this was a home theater forum lol. Car is a 1994 Honda Prelude Si. The sub has a phase switch normal and reverse, is that the same as physically reversing the polarity of the wires? And I will try your low pass and high pass numbers, thanks for the suggestions.
Yes, the phase switch should be set for the stronger bass (and it is basically a polarity switch). I was thinking when I originally saw the post it must be the noise floor of the car but after reading the description wasn't so sure....
 
Pogre

Pogre

Audioholic Spartan
Yes, the phase switch should be set for the stronger bass (and it is basically a polarity switch). I was thinking when I originally saw the post it must be the noise floor of the car but after reading the description wasn't so sure....
I'd never heard of car noise phase issues before but it seems plausible. The rumbling noise floor in a moving vehicle would fall into those frequencies, no?
 
lovinthehd

lovinthehd

Audioholic Slumlord
I'd never heard of car noise phase issues before but it seems plausible. The rumbling noise floor in a moving vehicle would fall into those frequencies, no?
I'd not thought of that phase issue either, but would be part of initial setup normally, too. I wonder if he's got one of the modified exhaust systems popular on such cars.....
 
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StayGoldPonyBoy

Audiophyte
I own the only stock 94 prelude left in existence lol. But it does have an exhaust leak and isn't exactly quiet.
 
highfigh

highfigh

Audioholic Overlord
I'd never heard of car noise phase issues before but it seems plausible. The rumbling noise floor in a moving vehicle would fall into those frequencies, no?
The road noise/car sound starts at a particular point in time and if the music starts at a different point in time, it won't always be 'in phase'. Generally, it's only really 'in phase' at a few times and then, only by coincidence, but it's close enough for Rock N Roll. This is the reason people started leaving a gap between the HP and LP crossover frequencies- the car fills the gap.
 
highfigh

highfigh

Audioholic Overlord
I own the only stock 94 prelude left in existence lol. But it does have an exhaust leak and isn't exactly quiet.
And the fact that it has an exhaust leak didn't tell you why you hear more bass when the engine is idling vs driving?
 
SPLaddict90

SPLaddict90

Enthusiast
gotta use noise dampening material to reduce the road noise from outside and vibrations, your also vibrating the vehicle which causes small amounts of cancellation etc. if your car has a lot of accessories running such as ac lights and all the alternator will not be charging your battery and the voltage drop will decrease output. Do you have any sound treatment on the vehicle? do you have stock alternator, how much power are you running and where did you ground your amplifier. but rule of thumb your car will be loudest sitting still running at around 1800-2000 rpm as this is where your alternator puts out peak current.
 

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