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Showing content with the highest reputation on 10/27/2009 in all areas

  1. 1 point
    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. Cheers!
  2. 1 point
    Imo I think you get more from the Sundown. Plus it is on sale. If your serious about getting a new amp, now is the time to jump on this deal. Here is some testing results ... Sundown FTW!
  3. 1 point
    well for starters the SAE1200d (v1 output nearly 1770 RMS at 1ohm) and the V2 is the upgraded version of hte V1 so it should do that plus more! lol! so SAE > Kicker (so much more power then the kicker) as for less amp draw maybe at 1200rms lol!! top that off with number one in customer service and some of the best made amps and you got yourself a killer amp! but you also need the electrical to bakc it up like any other amp does right! here is the clamp test for the V1 and also NOTICE how it was at 12.6volts!! very nice! i think the kicker is rated at 14.4volt? but i could be wrong
  4. 1 point
    i've been making and tweaking a box calculator the last few months. it's come along nicely i'd say. it's been over on *** (i'm ExpoSport over there...and if it's possible to change this name to ExpoSport me love you long time so after getting it tweaked to a good point i figured i'd share it elsewhere now. one thing that is still in the works is an open/save feature so you can save designs instead of printing or writing them down everytime. this is mainly for square/slot ports. plain boxes will be easier to do, but if you build a box in the car for example, you'd need to figure out the volume on your own and then fill the boxes in accordingly to get that volume, and then do what you need to do for tuning. same if you use angled sides in the box, tho i may try to come up with something for those, but the open/save feature comes first. Box Calculator.exe - 0.05MB ***you'll need the most up to date .net framwork for this program to work click this link to get it http://www.microsoft.com/downloads/details.aspx?FamilyID=0856EACB-4362-4B0D-8EDD-AAB15C5E04F5&displaylang=en ***just to clarify...when doing a slot port to add in end correction, use the port height as the the distance from the box wall to the side of the port wall. switching the numbers will give you a different tuning, as port width will be longer in and it'll extend the tuning a lil further than it should hope you guys like lemme know what ya think or any ideas i could possibly incorporate. as far as i know it should be pretty error proof
  5. 1 point
    More then likely you had them wired down to low. Generally home audio amps aren't built for low loads, most in the 8ohm range. Seeing the btl only comes in D1 or D2 ohm the highest you could have had it wired was 4ohm which would be low enough to blow a cheap plate amp that was rated for an 8ohm load.
  6. 1 point
    bump for the slot port correction - thanks bromo fixed that lil error. should be accurate now. you can check if you'd like it's late here...so hopefully i didnt overlook something. also added a check box that you can check if there are bends in the port. since bends do not require the port to physically be as long, this will yield a slightly larger net volume, which will change tuning. so i made it a check box instead of entering in the bends. if my math was right...you can have 4 or 5 bends without changing anything, which i dont see many boxes having that many bends as that would be a low ass tuned box. everything should be good to go now EDIT: oh yeah i guess i should post the new link, eh? lol Box Calculator.exe - 0.05MB
  7. 1 point
    Here is what I got compared to your calculator. Checking it against RE. Checking it against Sketch up.