well to be completely honest, i've completed everything in terms of power and speed for my WRX this year...and i've returned to the world of car audio.

as of right now i am running a Rockford/Fosgate amp (no idea what model...how much power...how old.., it was a gift from my brother and was professionally installed. i believe the box says "150S" or something...) and a Kicker comp 10 sub. I'm really enjoying the kicker in terms of sharpness and punch, for my Infinity blew a few days ago.

i guess i have a series of questions. and some of them might be dumb, but hey...you must have read the title of my thread.

My stereo sounds great, from inside the car...and genuinely that's all i care about. But when those certain cars drive by and you can literally FEEL the bass from their cars, what is the source of all that? Can you run the same sub on amp A and amp B and have one amp make the sub hit harder and louder? do 10's hit harder and 12's hit deeper? Do dual or even triple subs have any significance?

from a quality standpoint...i'm happy with my setup. but from the standpoint of "wow dude...sounds sick" coming from the guy standing 10 feet away from my car...i'm not so happy. All you can hear is my license plate rattling.


anyone willing to tackle my newb-ness...i'd appreciate it.

----TOM

A 15'' subwoofer with very high power handling should put out enough sound to be heard for quite a distance. You'd have to deaden the entire trunk, and add a couple more bolts to the license plate/spoiler/everything, but it would get you there.

Yeah, to get the axle-snapping bass you're talking about, you need to do some modification to your car's power setup <battery, maybe a second alternator>, as well as spend some big bucks on high power amps/15"+ subs if you want it to sound like anything but an earthquake.

Yes the WRX alt is a little low for too much bass. It is most all in the enclosure to make it sound loud; at least that is the hard part. It isn't hard getting a decent sub and matching amp. Are you willing to give up your trunk?

offset
my Car Audio Manifesto (http://forums.nasioc.com/forums/showthread.php?t=824983)

let's try to touch on a bunch of this...

first, physics has a lot to do with this. 10" subs have the myth of hitting harder and 12" subs hitting deeper because basic physics rules say that the smaller cone size will flex less - hence the hit harder theory. again, physics would suggest that 12" subs would play lower and deeper notes because the bigger cone size will match the bigger sine waves of the lower deeper notes. These are only basic rules to start with, but they don't apply 100% of the time. There are SOOO many other factors that also apply, that you can't really use this rule in reality. Some brands of speakers may not be built as well as others. One brand of 12" may hit a lot harder AND deeper than another brand of 10". Or one brand of 10" may hit a lot harder AND deeper than another brand of 12". When you get to a certain level of quality, you need to compare speakers on an individual basis...

Next, you asked why two or three subs would be better than just one. Well, again it is simple physics - bigger is better (or actually, bigger is louder). More surface area will move more air... and the movement of air equals sound, so more surface area equals more sound. I forget exactly how the surface area works out, but you can use simple math. I think two 10" subs has the same surface area as a 13" speaker?!? So why choose one 12" if you can have more sound with two 10" subs?!? And how many 10" subs does it take to equal one 15" or 18"?!? Anyway, there are sooooooo many physics laws that factor in when you atlk about using two small speakers vs. one bigger speaker that I can't type it all in a couple hours (like the fact that two small speakers will respond quicker than one bigger speaker, one bigger speaker will usually take less power than the two smaller speakers to make the same amount of sound, etc...) In any case, just remember more speakers equals louder sound assuming that you have the amp power to back it up...

Why can some stereos be heard easier from the outside? Well, the shape and size of certain cars helps. The way the box is designed and where it is placed in the car has something to do with it too. The amount of reinforcement and sound deadening used in the car affects it. Also, as discussed above, the amount of speakers and size of speakers affects it. And the amount of power put to the subs affects it. I had two 12's and a 1000 watts (real, not some cheap amp) that was way louder than one 18" sub and a 200 watt amp in...

the rockford 150 is a good little amp. Do you know if your sub is 4 ohm or 8 ohm? The sub for this setup should be 4 ohm, but not in every case. some sub/amp combos may require something different to maximize sound and power...

i'm going to go check on that sub...the box is out in the garage.

thank you for your in-depth post...you cleared up quite a bit for me.

basically i now understand that if i really want that "oomph" to my stereo...i'll probably need to pick up a more powerful amp and a good quality 12" sub that will hit just as hard as my kicker comp 10.


i'm glad that you (janikphoto) recognized my amp...maybe you could help me out a bit more? i'll shoot a PM your way.


----thanks, TOM

To go off on what Janikphoto said, and to expand it a bit more:

The "law" that governs adding subs, or speakers, and power is called the "Inverse Square Law." You can Google it for more Physics than you'd ever want to see for the rest of your life. But here's a quick (and very simplified) breakdown of how it works.


(Point Source basically means speaker. These rules hold true for all audio based on a point source system, but are only close for "line sources" (line array's at concerts for example))

The inverse square law states that "For each doubling of the distance from the point source, the measured SPL will drop by 6dB"

This rule works a few other ways too. So Every time you double the amount of power to a point source it will increase the SPL by 6dB

or

Every time you double the number of point sources at equal power it will add 6dB

6dB is exactly a doubling of the amount of actual sound there is, but isn't perceived as a large difference to us due to the way we hear.

Now this is in a perfect world, where there is no cancellation, etc... realistically you actually only get somewhere between 3 and 6dB.

(This is why at concerts you see SO MANY speakers. Because every time you get 2x farther away from the speakers, you loose 6dB, but every time they double the # of speakers they gain between 3 dB and 6dB. So if they needed 12 speakers at 10 meters, they would need at least 24 at 20 meters, and at least 48 at 40 meters. (yeah, sux don't it))

Sorry, I'll get back on topic.
To make something actually sound 2x louder to us, because of our logarithmic hearing, takes a boost of 10dB. So 100dB is 2x louder than 90dB, and 4x louder than 80dB.

So the true added power of having a second sub really isn't that much at all. You are only gaining between 3dB and 6dB, and that is only if the box is built correctly, and you have spent the time on things like time alignment and sound deadening. If you haven't you can induce insane amounts of comb filtering, and the system can actually appear to have less bass than with just the one sub. This is why proper design of the system does so much more than just having lots of it.

This can come in real handy when you are purchasing stereo equipment also. Because sales-persons will swear up and down that the 600 watt amp is SO MUCH LOUDER than the 300 watt amp. But in reality, in a perfect world, the most difference that it could make would be 6db. And if you're dealing with a...lets say a 4 channel amp that is rated as a 400 watt amp, so 100 watts per channel. And they're trying to sell you a 500 watt 4 channel amp. which is a 125 per channel amplifier. You will actually only gain 1.5dB TOTAL from that extra 100 watts.

Also, don't be impressed by a 6000 watt system, versus a 1500 watt system. it seems like a huge difference, but the 6000 watt system (again, in a perfect world, real numbers will probably be lower) is actually only 12 dB louder, which is slightly more than twice as loud, for 4 times the amount of power, and an @$$load of money

Ok, I don't really know what made me want to write all this nonsense out, But it's handy knowledge to have. I tried not to oversimplify it too badly, and not make it too technical. But now the next time you go to buy a home theatre receiver, or a head unit, and they're trying to sell you on "5 more watts of power per channel" you can laugh at them, and save your $50 or $100

If you get a chance and you'd like someone local to give you some advice or just take a look firsthand at your setup, I'd be glad to help out a fellow NASIOC member.

If you get a chance and you'd like someone local to give you some advice or just take a look firsthand at your setup, I'd be glad to help out a fellow NASIOC member.


hey yeah that'd be cool. i'll shoot a PM your way.


--TOM

yeah, I was gonna touch on the whole inverse square law and how it affects power and a person's perception of volume, but I got side-tracked and forgot. Thanks for adding that info, because it plays such a big part in understanding why and how to make a stereo louder...

and let's also remember that 1000 watts isn't always 1000 watts. some cheaper brands have ways to fudge their power ratings and I use dto sell a rockford amp rated at 75 watts that would blow away some cheap brands rated at 400 watts. My customers would be so surprised...

Yeah, 1000W at 1 ohm is NOT 300W @ 4 ohms :lol:

Companies REALLY try to screw ya with numbers, always look carefully