Pro car audio competition pysics of getting really loud?

[Huricaine]

Hi, since I've been helped before with a question about the pysics of subwoofer resonance, I thought I would ask another question I need for my audio knowledge bank.

I am into car audio, I like competitions where people burp single frequencies to acheive staggering spl levels like 145-180 db! But for me, what I would like to work on is doing music as loud as I can with one 15", and 2 18"s later.

I have read about two types of subwoofers: mass controlled, and compliance controlled.

The way I take it is that for a compliance controlled subwoofer, xmax and cone area, are the two key factors for a subwoofer to get loud, and they tend to be inefficient, and not perform well in the upper mass controlled frequencies.

And how does using more force from higher bl make a subwoofer louder in the upper freqs, I know at like 40 and up, the motor has to interup the cones momentum so that it can move faster, thus a strong motor would controll better, but is there a point where there would be an end to needed motor force one you know that the subwoofer is contolled enough, and not gain any extra spl? How does this equate to higher spl? In conjunction with a vented box, and say a qts of .32-.34. So also, if you could use more force, then how would the subwoofer be atthe Sam frequency if the acceleration should change?

Question, for subsonic compliance controlled subwoofers, is xmax the main thing given same cone area, to get loud?

And I've read that mass controlled subwoofers get loudest with high sensitivity, so given the same cone area, xmax, suspension compliance, a bigger motor force will make it louder?

I am trying to understand mass controlled subwoofers and: power compression, ported box pysics in somewhat simple terms, why xmax dosnt matter supposedly with mass contolled subwoofers when it could move more air
with more xmax, is the amount of air moved not equate the spl? I thought It was everything, and maybe it is for compliance controlled transducers, but I guess a ported box and a low qts somehow change this all, no? If ported boxes can also be explained would be great, I've heard something about the phase of the vent air being opposite at time but don't understand how and why.

[uzernaam]

A mass controlled sub is another way of saying "its motion is resisted because it's so heavy." These kinds of subs are usually large. I know clarion made a 30" sub, and it was "mass controlled."

Compliance controlled are those that are dominated by the resistance of air pressure and the speaker's surround and spider. These are smaller subs.

Whatever you have, if your goal is to get gigantic SPL, what you're dealing with are primarily 3 factors (none of which have to do with the above two) -

1) Power output. You need a lot of watts to start with.

2) Resonance. Your vehicle and the box your subs are in will create a cavity that will resonate at certain frequencies.

3) Containment. Leaks of the pressure inside the car to the outside world, and physical motion of parts inside the care will bleed off energy and diminish SPL. The biggest "leak" is the body of the car, expanding and contracting like blowing up and deflating a big balloon. It's hard to avoid unless you build your car out of welded, reinforced bulletproof armor.

Once you have the power available, and the subs to turn that power into pressure, after that it's a matter of experimentation and trial and error to create an enclosure that matches the volume of the air mass in your car for resonant frequency. Get it right and you can get as much as 15 dB higher than you would if you had it all wrong.

In the SPL competition circuit, it is assumed you already understand what kinds of speakers you will need, and how to build a big, sturdy box for them. After that, it's watts, resonance, containment.

[soho54]

Start by forgetting the mass/compliance controlled things you have read. I'm assuming you saw the Top Subwoofer Myth list posted somewhere.

They don't really mean anything, and are pretty pointless. Mass controlled drivers are not the huge drivers, they are your pro-type drivers, low xmax and high sensitivity. They are mass controlled because they are designed to operate at frequencies where the moving mass of the driver affects the acceleration more so than the compliance of the driver/enclosure combo, which is a greater factor at lower frequencies.

Look at it this way, a mass controlled driver is designed to run from 40Hz up several hundered hetz into woofer territory, and a compliance controlled driver is one that likes to stay below 100Hz, and dig to 20Hz and below.

This really doesn't tell you anything. If you want to burp a 20Hz, you are not going to use a driver that dies at 40Hz anyway, and if you are going for 80Hz you aren't going to waste your time with a low sensitivity driver with a huge xmax that will torch the VC long before half the xmax is used up. If you want something in the middle you use a driver that is a mix of both, no big deal.

In the end it doesn't really mean anything, as you just pick the driver that does what you need it too. If you want 30Hz up then you need to look at pro audio designs. If you want infrasonics then you need drivers with low Fs, and very high xmax.

Xmax always matters though, you just don't need as much as you go up in frequency.

[MaVo]

I am no expert, but i think the maximum spl depends on power rating, xmax and enclosure size. Power rating is obvious since spl is directly related to how much watts go into the speaker, xmax is a necessary thing, since the more watts go into the speaker, the higher the excursion will be. Enclosure size isnt so obvious, but compare a horn and a closed box, driven by the same speaker. The horn will be much louder than the closed box. Within limits, the bigger the box, the louder it will be.

So, if you search for an optimal driver, first choose a bandwidth, then set a size limit, then figure out what drivers with which watt/xmax ratings are available for the possible enclosures and you should arrive at a pretty good spl value.

[Huricaine]

Thanks everyone, and soho, I understood all of what you said, i had understood it from the myths article from audiopulse...I just didnt realize that mass controlled drivers were controlled mostly by driver-mass and not box/other, i actually figured it opposite, that, mass controlled subs were VERY dependant on enclosure mostly.

So what about xmax? I undertand alot about caraudio like tsps, and etc. But, it has been controversial that people claim that xmax isnt needed for pro audio subwoofers, and i do understand that because the driver cant move very far at higher freqs. But i figure, what if you can get a subwoofer with good xmax that is a good amount efficient, fictional or not, and have so much motor force that the driver can reach 2.5" PP excursion at like 50hz? Sounds impossible but, would this create much more spl?
I know people who will say: Amount of air moved (vd) dosnt make higher numbers, its about the acceleration. But isnt acceleration the frequency? Or is acceleration how quickly the driver can start the next wave? Because i thought rate of acceleration, and acceleration were the same? Im a little confused.

Also, things will change rom sealed i know, when going ported.

Btw, i have a subwoofer already, i dnt want to burp or compete per se. I just want a loud hard beating daily system for my truck. And i have 1 15" subwoofer that has a motor that looks like an atomic apxs or a little bigger and comming is a ss dtr 1700w, or 2200w amplifer, for the single sub.

[chris661]

For SPL competitions, it's been recommended to use a series tuned 6th order bandpass, where one chamber vents into the other. If you get the tuning frequencies the same, you get extremely hard hittting bass, but only at one frequency. You'd have to operate the cabinet solely at that frequency, but it will be very very loud.

Subwoofer Enclosures, Sixth and Eigth Order/Bass Reflex and Bandpass

For every day use, a sealed box would likely be better.

[AndrewT]

The only poster here that has a reputation that I may trust, starts off with "I am no expert".
I shall read the remainder but I don't hold out much hope of understanding what physics you bring to the discussion.

edit:
I have read the remainder & I guessed right.

[Top Shelf]

+1 to SoHo on forgetting that crap, no one that I've seen has talked about that or even concerned themselves with it.

[Huricaine]

But it makes plenty sense. Because the two categories are like night and day. For instance u really dnt want to burp with a subsonic subwoofer or use it for live reproduction.

[454Casull]

What frequency are you trying to burp?