Tommythecat

So you can plot like BL/RE/etc. across stroke on a graph like the Klippel does with its laser? Awesome!

Unless you really care about the cosmetics being perfect: 1) Get large flathead screwdriver 2) Set woofer down and grab the farside of the basket 3) Put screwdriver between frame and motor 4) Push down on the screwdriver like a lever until you hear a pop. Do it quick and hard and you wont even leave much of a mark on aluminum baskets. I do it all the time.

Wow, what a douchenozzle thing to say. Makes me want to buy an Icon.

Well, I dont have a full report right now - but I figured I could throw something out there. I don't want to come off as some know-it-all who doesn't seem to know-anything. I guess I owe this thread a response. Our first graph shows the Driver's free-air impedance response and a bass-reflex enclosure response. Typical results. Free-air response has a single impedance peak which comes from the mechanical resonance from the spring-mass relationship between the spider+surround and moving mass. The vented response has two-peaks but they cannot be attributed to a certain single thing. (scaled for emphasis - not absolute values) This graph (is mislabeled because I'm lazy) and it shows some interesting things. We have the: 1) port resonance impedance - rising to a peak at the desired tuning frequency 2) the driver's mechanical impedance - a parabolic curve with a minimum at the driver's Fs 3) combined response of the two above plots Now we see the combined response plotted against the (electrical side) impedance. This should illustrate where the impedance valley and peaks come from and why the valley is centered on the tuning frequency. Technical Chatter: Why are these graphs inverted? What you have to keep in mind is that what goes on mechanically seems to be inverted from what we electrically measure. When the mechanical impedance is "reflected" into the electrical domain it is related by the factor of Bl^2 / Z. So our drivers mechanical impedance (as seen in figure 2) appears as a parabola mechanically, but electrically it appears as a hump. What about the peaks being directly related to driver/port? I believe the only way this could be arrived at is how the port and enclosure losses can affect the impedance peaks. Because our model is an ideal - we can and should account for some of the friction/leak/etc. losses that occur. For a closed box we account for box losses (Ql) and for a ported box we account for both box (Ql) and port (Qp) losses. These losses must be measured and compared against our model to be sure of their absolute values - but there are some general values that can be used to predict the reponse. When you model a bass-reflex system and vary the losses (Q's) you start to see that the Ql will affect the lower peak and the Qp will affect the upper peak. This has lead some to infer that upper peak is "created/controlled/or something" by the port and the lower peak by the driver(box would be more accurate). But this isn't the case. If you simply model a loudspeaker and tune the box below the driver's resonance you'll see that changing the Qp will affect BOTH impedance peaks. It's something of a coincidence that one loss factor changes one of the peaks in a system where the box tuning frequency is higher than the driver's Fs.

He does mean that 3,6,7,8 will be in the "ON" position (to the right) while the others are "Off" (to the left). That's what my memory tells me works for bridged mode. And while it's a little confusing - I think it helps force users to think about what the hell thery're doing back there so they dont blindly flip switches.

What sub? My buddy had some JBL's with "1500 Watts" written/painted on them and they came right off with rubbing alcohol or some other slightly toxic liquid.

Why not try 20 cubes?

3.5-4.5 cubes tuned to 30ish Hz.

Well, I guess it doesn't have a magnesium/banana/silver cone so its flawed from the start. That and it doesn't fall in the xmax sweet spot for SQ (either 1mm or 30+mm).

Quick, where's M5 to back you up? I think he just meant does it sound like complete ass or at least reasonable.

Sarcasm is not always funny to those who are on the receiving end if they understand it. And ThomasW is a moron because he booted me from HTGuide forum for asking him to back up his statement that "ported gives you 3db more efficiency over sealed" which is a classic misleading diy creation. As for the Crunch amps - I have not heard them, but those 3000W guys do rated and are c-h-e-a-p.

Smilies make it seem like Im joking.

I obviously dont post my thoughts enough on here - my sarcasm does not bleed through the computer screen.

Yeah, I mean - Class D? No thank you, I listen to music not 1's and 0's...such philistines

And if you dont need the fancy screen get the 9883 for even less.

I would think the old Seas T(B/D)FC would be the "budget" king at almost half the price.

Understanding what's physically happening with a loudspeaker is something of a feat. I certainly haven't found any comprehensive and yet perfectly understandishable explanation of it. It's something I hope to cover in a lecture next semester - hopefully I can get it down to 1 hour including prerequisite knowledge (simple differential equations, circuit analysis, etc.). Even beyond an hour audio-visual extravaganza it takes some effort and hours of problem solving/coding to start to truely understand (the kind of "understand" when light-bulbs go off in your head). I think it's funny that someone like ThomasW could make a statement such as "ported enclosures give you 3db more output over sealed" and get away with it. What does that statement even mean? I tried to pose the question to him at Htguide and was promptly banned and the post deleted. You can search for it because he's said it more than once - but it's a waste of time. I'm not a big fan of ignorant, blanket statements that run rampant in DIY audio. That and my mommy didn't love me enough. That's why I think he's kind of a moron or at least willfully ignorant.

I have emphasized what I find to be a common mistake among many people. The impedance "humps" you see are not characteristics of one part of the circuit or another. The impedance shape comes from two things: 1) The impedance peak from the drivers' mechanical resonance 2) The impedance dip caused by the port The dip is really "dug out" of the impedance peak by the port resonance. That is why the dip is centered on the tuning frequency of the box. It's really a bit more complicated than this explanation, but it would take a entire primer on loudspeaker modeling to uncover what's going on here.

Do you have a song picked out for something like 55Hz?

Have you tried the Memphis higher I meant, they might keep the voltage up that way.

Not too many, just look for some pictures of an old volvo wagon and imagine a Brazilian flag on the hood. edit: yeah, i didn't remember too many here: http://www.termpro.com/asp/competitorstats...2007&Page=2