My findings on sub placement

Today I experimented with different sub placements in my extended cab pick-up. I built a 1.07 ft^3 sealed box for a single 10" sub. So that's what I had to play with. I played a single sine wave tone to keep things simple. After spending a few hours in the truck, I concluded, that to maximize your output you need two things:

1) Turn your sub AWAY from you. If you keep it facing you or even playing up at the ceiling, the output is A LOT LESS. My ears tell me there must be at least a 10 dB difference when the sub faces you...a little less when it plays at the ceiling.

2) Place the sub as far away from you as possible. I noticed this before too. Even my front components would output much more bass if you sit at the rear seat. I placed my sub on the rear seat facing the rear wall, and seating in the driver seat and leaning over, increased an audible amount of dB! I remember when I had a 2dr Prelude, I had a sub in the trunk facing the rear of the trunk. When I sat in the rear sit, I would get significantly less bass. I didn't think of it much then, but now I know for a fact that bass gets louder the further you're away from it.

So if you're thinking about sticking a sub right in your face...you will only lose. I know this for a fact too.

Yep vbel, your findings are pretty typical, although every installation can be different.  It has to do with physics and the wavelength of subwoofer frequencies.  For example, a 50Hz sound wave is approximately 22 feet long, so to be able to hear the peak of that sound wave you need to be about 22 feet from the speaker.  Good for you to try different speaker placements and discover what works best in your installation.

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My question to vbel would be, where do you go to get your ears tuned to pick up a 10db or greater difference? Just asking...

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VEHICLE: 2002 GMC Sonoma ZR2
Alpine CDA-7940
AudioControl EQT x2
JL Audio 1000/1
JL Audio 10W6 (originals) x3
Kicker ZR120
Kicker ZR460
Polk GXR-6 x4
Polk GXR-4 x2

nouseforaname wrote:

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my hearing is so bad, i probably couldn't notice a 50dB difference.

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Your ears are fine. I think its that thing between em thats malfunctioning...

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'89 Mercedes-Benz 300E
Pioneer DEH-5900UB
(2)RE Audio SX 10"s
(1)US Amps MD3D
3ft^3 @ 37Hz

Blowing up in a car accident doesnt worry me, as long as I'm putting out some major dB's when I die...

nouseforaname wrote:

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it's nice to see people actually get in there and experiment insted of just asking what other people think. great job. but a 10dB difference?

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I was in the driver's sit and the sub was on the passenger sit facing me. Then I turned it away from me to the door, and it became about twice as loud, which is what 10dB is, I believe. Of course I'm not an SPL meter, but that's an approximate figure. It was at least twice as loud I should say.

3dB gain would be doubling of power, not doubling of volume, which is 10dB. And from my findings, it didn't have much to do with bouncing it off something or not. If I bounce it off the door by facing it to the door, and come bring my head up close to the sub, I would lose volume! And I'm sure it has something to bounce off when it faces me, and the door behind me.

Another thing I forgot to say, is when the sub is facing the door, away from me, and tilting it slightly up would cause volume loss. I doubt the door's window had anything to do with it. You just need 180 degrees to make the most of it. Now it will be interesting to see if this tilt has the same effect in the trunk, because I see so many boxes made with a tilt.

nouseforaname wrote:

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power isn't measured in dB's you know. if someone hit 120dB and then hit 123dB, their sound is twice as loud.

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I don't know where you got this from. Power isn't measured in dB, but what happens when you double the power? How many dB's do you gain? Also, if you have a home receiver that displays volume in dB, then you know for sure there is just a slight change in volume when you turn it up by 3dB.

nouseforaname wrote:

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power isn't measured in dB's you know. if someone hit 120dB and then hit 123dB, their sound is twice as loud.

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Decibel

~wirewise~

nouseforaname wrote:

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the "tilt" as you called it, which i assume you're refering to an angle in the box, is to reduce the standing waves inside the box.

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Low frequency waves are too long for a small car audio box to develop in. This isn't an issue.

nouseforaname wrote:

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half power is the point at which the low frequency system acheives a -3dB down point. again, power is not measured in dB's.

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I never said it is measured in dB. I agree with "half power = -3dB" formula.

I don't think that the F3 is where the system is only putting out half of its capable power...just doesn't seem logical to me...or maybe I'm stubborn...

I know in a home system for sub placement you take the sub and put it in the chair you will be in the most and walk around the room and find the best bass and then move the sub to that spot. This should work the same in a car or truck but you do have space limitations. You can't walk around in a car or truck.:)



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Shane

+10db SPL = "twice as loud."  +3db SPL = "twice the power."  It takes approximately 10 times the acoustic power to create a doubling of perceived loudness or +10db SPL.  The F3 of a speaker system is the point where the output is -3db down from average, which is about 1/3 less output, but yes it is about 1/2 the power level.  Power can indeed be measured in db's, by the way, but the common usage in car audio refers to loudness, so people often misuse "db" to really mean "db SPL."

Also, for subwoofer frequencies there can be no "standing waves" inside the enclosure as the enclosure is far too small for this.  Indeed, subwoofer standing waves are also N/A inside vehicles.  In large rooms standing waves can be generated by subwoofer frequencies so they can be a major concern in home theater design.  But for subwoofer enclosure design and for use inside a car, they are not applicable.

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Thank you DYohn, nicely put.

Since we're on the subject I thought I'd mention that the sensitivity rating on a speaker is in direct relation to this equation as well. The sensitivity rating is the volume in dB at 1 watt of power from like 1 meter or 1 foot (I forget..) in front of the speaker. Each time you double your power you get +3 dB. So a speaker with a sensitivity of 90 dB would put out 93 dB at 2 watts, 96 dB at 4 watts, 99 dB at 8 watts, etc. doubling the wattage each time. Other factors obviously will make huge differences on how loud your system will be, but this is a way to get a general idea of what a speaker is capable of putting out when put in relation to the power handling capabilities.

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2 x DD9515f's, Digital Designs Z1 amplifier