Does X-max = Spl

[emperorjj1]

good points on here. sorry i have to do some drew bashing on here thou. XXX will be the cleanest sub out of anything listed here period. With that being said anyone using them for an SPL application is stupid (sorry), they are not SPL drivers and are not made to do SPL the new v4 XXX isnt going to handle a lot of power for an extended period of time. Short bursts only. and if ur only doing burps and have plenty of power why not get an MT, BTL, Lv5, DD 9918 ect. you wouldnt buy a mini van to turn into a drag car nor should u try to make a SQ sub an SPL one... but one thing the XXX can do that the others cant is play those low ass notes. You spl guys cant play "the dream - i love you girl" like i can

[Forevrbumpn]

I didn't read all of this, my eyes suck

But one thing xmax is good for SEALED

if you have say a 15" in a 1cf box, yet can do 3" total xmax, that would be a damn good SPL woofer as far as sealed goes

but to ported, no, doesn't matter.

sealed xmax does matter xmax x's cone area-

That was the whole JLw7 vs MTX9500 debate

what could push the most air in a sealed box

[RobClay]

Maybe the guy who said this to me need's to really read this thread..

Why don't you just get 3 12" Btl's? You don't HAVE to put 2000rms on each.

The Btl's will be louder than any other Fi sub on the same power.

Why would you say that? Also the Btl's wont be louder on same power, the bl's would because they'll be at max.

[sound xtreme]

If your going to be going for pure SPL, you need as much cone area as possible, as much power as you can afford(and then take out a loan to buy more) buy a shit ton of batteries, build a enclosure and refine it for a few years. While all the ratings are nice to look at, you can take the worlds best woofer (parameter wise) and stick it in a shit prefab box and its gonna sound like a shit best buy woofer. or you can take a shit best buy woofer and use it in a refined enclosure and it will be amazing.

A few years ago, Team loud from finland hooked up 1 SPL dynamics 1000D and burped a 170+, then they put the 32 amps back in that they were using and burped a 179.xx. Is the amp that good, or is the enclosure that well built??

Bob Perillo was using 9 memphis mojo woofers and was maxing out in the mid 168's, now he is using a much better built T3 TSNS woofer and is topping out inn the high 169's.

Stop being so overly concerned with numbers, build the box, rebuild the box, refine, refine, refine................

[Boon]

Cone area and power be damned.

At the shop we pulled a 142.7 with 2 DD1508's on 600wrms total. Because the box was damn good and in a tiny little car

[Jville140db]

This is always an interesting and controversial topic. Every couple of weeks, a debate rages regarding the relevance of high Xmax and whether it is truly valuable to achieving SPL scores. Perhaps the greatest argument is that Digital Designs Audio drivers, who have a very impressive track record in SPL competition, have been routinely tested to show below average Xmax numbers. How is it possible that a driver with limited linear excursion can still be amongst the loudest? The answer is simple and complex all at once: Xmax is relevant to SPL and it's not. Now that I've confused you, let's proceed.

I'll touch on how a speaker makes sound and how it's interpreted at a later time, but let's skip to some ground works. Acceleration is a critical component of creating SPL. The higher the rate of acceleration, the more pressure that can be created. Let's figure out how to get there.

If you've been through any high school physics classes, you're probably very familiar with this equation.

F=m*a

Hey, that looks like Newton's Second Law of Motion. In short, it states that the net force of an object is equal to the product of it's mass and it's rate of acceleration. Of course, we can re-write the simple formula to better suit our needs.

F/m = a

After our spinning, the formula reads that the rate of acceleration is equal to the net force of an object divided by it's mass. Let's apply this to speakers for a moment, shall we? The force of an speaker is determined by the two factors:

1. BL - the combination of the magnetic field strength (B ) and the length of the voice coil in the gap (L)

2. i - the level of input current

Taking that information and our above equation, we can easily translate this to a speaker relevant equation.

(BL* i)/m = a

Let's make some logical conclusions from this formula.

1. Increasing the magnetic field strength (B ) or the length of the voice coil in the gap (L) will increase the rate of acceleration

2. Increasing the level of input current (i) will increase the rate of acceleration

3. Increasing the mass of the driver will decrease the rate of acceleration

Naturally, the inverse of these conclusions holds true as well. For example, if you decrease the moving mass of the driver, the rate of acceleration will increase. Simple stuff, me thinks. Now we have our foundation for understanding why Xmax is and is not relevant to SPL.

We know what we want to have a really loud driver, don't we? Huge BL, ability to take a lot of power, with extremely low moving mass. When looking at thiele/small parameters, we are looking for something with a high BL^2/Re, high power handling, and low Mms. It's odd that Xmax isn't factored into that equation, don't you think? Ahh, but it is, in a sense.

Once we apply current to the voice coil, it moves. Based on the Understanding Power Compression thread, we know that as the voice coil moves out of the gap, BL decreases. It stands to reason that as the voice coil moves out of the gap, BL decreases, and based on our previous conclusions, so does the rate of acceleration! In this sense, high Xmax is a good thing because it means the driver is capable of moving further without an alarming decrease in BL. In this sense, high Xmax is a great thing. A driver that can move great distances while keeping BL very linear can make for a very good, very loud driver. This is handy for competitions like Bass Race, where everyday music is played for longer durations.

With that said, there is another aspect of SPL competitions where high Xmax may not matter so much. In DBDrag style competition, high Xmax is not always critical. Typically, a competitor plays a short burst sine wave near the resonant frequency of the port(s) used in their enclosure. This excites the air mass in the port, causing it to become the primary source of our pressure. Meanwhile, the driver that is exciting the air mass is relatively stationary; it is not excurting itself very much at all. If your driver is only moving +/- 2mm, what is the difference in BL between a driver with 16mm of Xmax and a driver with 100mm of Xmax? Not much at all.

There is one more important consideration in the "high Xmax vs. SPL" equation. Again, looking back at that original equation, we know that high moving mass decreases our rate of acceleration. Let's pretend I'm engineering a driver for a client who wants high Xmax using conventional designs (more on this another day). How do I do so? Quite simple: I add length to the voice coil. There is, however, a caveat to adding length to your voice coil: more wire (be it copper, aluminum, etc) adds mass to the driver as well. This is not a good thing from an SPL standpoint.

As we can clearly see, high Xmax and SPL are not necessarily mutually exclusive; in fact, sometimes they go hand in hand. At the same time, some situations call for very little Xmax. This is why companies like Fi Car Audio deserve more credit than they receive: there is no one answer for every question, but we'll allow you to customize our answer to suit your question.

The point comes back to a daily engineering focal point: where can I afford to make sacrifices for the application? And that ultimately brings us to Newton's Third Law:

For every action, there is an equal and opposite reaction.

There you go.

ok simple definition big bl, low moving mass, decent excursion, equals a high sens and makes spl that is why most spl driver are paper or pulp cone with some coating, foam surround, medium size coils, and have huge amounts of magnetic energy hell look at some of the most famous of all dd9900 seris, the amican bass vfl, mmats juggernaut, mtx rfl152 sorry that one was for me lol, and last but certain not least those wonderful fi btl's

[Jville140db]

If your going to be going for pure SPL, you need as much cone area as possible, as much power as you can afford(and then take out a loan to buy more) buy a shit ton of batteries, build a enclosure and refine it for a few years. While all the ratings are nice to look at, you can take the worlds best woofer (parameter wise) and stick it in a shit prefab box and its gonna sound like a shit best buy woofer. or you can take a shit best buy woofer and use it in a refined enclosure and it will be amazing.

A few years ago, Team loud from finland hooked up 1 SPL dynamics 1000D and burped a 170+, then they put the 32 amps back in that they were using and burped a 179.xx. Is the amp that good, or is the enclosure that well built??

Bob Perillo was using 9 memphis mojo woofers and was maxing out in the mid 168's, now he is using a much better built T3 TSNS woofer and is topping out inn the high 169's.

Stop being so overly concerned with numbers, build the box, rebuild the box, refine, refine, refine................

awwwwwwww thats strikes me deep best buy woofer [i work their] but i'll take it in stride because your right test and tune is the only way to perfect a build my cars been changed 4 times