Impious

Yes, the Fs may drop some as a result of the Cms increasing. However, since Fs or Cms are also used to calculate Vas, Qes, Qms, and hence Qts, the net change in in-box performance will be completely inaudible. We are talking a difference in response in the same enclosure of tenths of a decibel and a tenths of hertz. So while yes, the Fs may drop some....you can not attribute a change in sound to this phenomenon since all of the other determinant parameters change in proportion to Fs aswell.

This would be why no one t/s parameter can be relied on to determine woofer quality? Also why there's no "perfect" woofer? Short answer because I'm tired; Pretty much. I'll try to help if I can

Ultimately you can't just arbitrarily adjust Cms without consequence even if it doesn't directly impact sensitivity. If you look at the BTL example I posted earlier, the Fs jumped by nearly a half octave when we halved Cms. So the engineer is going to have to balance Cms (and sensitivity) with the other performance goals for the driver.

I would rather have a pair ported than a trio sealed.

Team SSA is not responsible for possible side effects of (and probable embarrassment resulting from) experiencing The Brown Note Team SSA is proud to be responsible for the 1st place trophy you just lost.

Nope, efficiency would remain the same aswell. Sensitivity is based on the relationships between motor force, cone area and moving mass.

Nope, efficiency would remain the same aswell. Sensitivity is based on the relationships between motor force, cone area and moving mass.

Meh, I guess if I were re-running all of the wiring anyways I would spend the extra couple minutes and hard-wire the 12V switched (ignition) wire. I don't care how fancy of a plug you get.....IMO tapping the fuse box is a little ghetto and lazy. For quick-fix scenarios or short term temporary use, sure. But for a permanent install.....no. If all of the factory wiring is intact you should be able to trace the OEM wire back to it's origin.

Clamping the DC side of the amp would tell you how much power the amplifier is drawing from the electrical system, not outputting to the speaker. When someone "clamps" an amp they are measuring the output side of the amp, which is AC. They normally keep a DMM on the power input side to monitor what the input voltage is dropping to, but that's not how they are deriving their power output figures. Anyways.....many people fall under this delusion that they are performing some meaningful act by "clamping" their amplifiers. As Crazy said, they connect their amplifier to a load (normally just a subwoofer in most cases) and play a test tone. They then use a DMM to measure the voltage output from the amplifier and a clamp meter to measure the current on the output side of the amplifier while playing the test tone. They then use basic ohms law to calculate power (Voltage * Amps = Power) and the impedance of the load (Voltage/Amps = Resistance). As I previously mentioned, most people will also use a DMM on the power input side of the amplifier to monitor the voltage drop the electrical supply is experiencing. The problem is, 99% of the time people are simply wasting their time. It's a mostly meaningless endeavor that has been perpetually (and incorrectly) promoted on the internet as having actual relevance. There are several problems with this method. Along with being able to question the accuracy of the measurements themselves for various reasons (accuracy of the devices, the type of measurement being conducted, the varying impedance of the load, the varying stability of the supply, etc), many people try to compare these "clamp test" results to the manufacturer rated power. The problem is, the manufacturer's rated power is specified at a certain distortion level. Nobody performing these clamp tests are measuring distortion. One could make any amplifier appear highly underrated very easily in one of these "clamp" tests as there is a total disregard of distortion.

What is your budget? How much power or what amplifier are you using? How were you planning to actively crossover the drivers? What frequency range did you intend to use the drivers? How much room do you have to work with?

Umm....what? Not sure how you are arriving at that conclusion or that correlation.

Forgot to even mention yesterday that Cms (suspension compliance) doesn't directly affect sensitivity Let's take an example of the BTL, a high power handling SPL-oriented subwoofer. It has the following relevant parameters (dual 1ohm version): Fs - 39.3hz, Qes - .21, Vas - 25.7L. If we plug this into the formula for calculating sensitivity, we find; SPL = 112+10*LOG(9.64*10^(-10)*39.3^3*25.7/0.21) = 90.5db Now let's take the same driver and double the stiffness of the suspension, meaning suspension compliance (Cms) would be halved. This changes the relevant parameters (per WinISD) to: Fs - 55.9hz, Qes - .303, Vas - 12.8L. If we plug these parameters into the same sensitivity formula, we find; SPL = 112+10*LOG(9.64*10^(-10)*55.9^3*12.8/0.303) = 90.5db So we cut the compliance of the suspension in half (doubled stiffness), but the sensitivity of the driver remained unchanged. You can alternatively calculate driver efficiency with the following formula; Efficiency = (BL^2 * Sd^2) / (Re * Mms^2) * 5.445*10^-4 Which you can see, neglects to reference the suspension compliance or stiffness.

Like KU40 said, no difference. Ideally you would want to avoid wiring the two subwoofers together in series to avoid each subwoofer from "modulating" the other, but chances are for a daily driver you won't notice any difference.

There's a hole in my subwoofer, dear SSA, dear SSA, There's a hole in my subwoofer, dear SSA, a hole. Then fix it, dear youngb94, dear youngb94, dear youngb94, Then fix it, dear youngb94, dear youngb94, fix it. With what shall I fix it, dear SSA, dear SSA? With what shall I fix it, dear SSA, with what? With a recone, dear youngb94, dear youngb94, dear youngb94, With a recone, dear youngb94, dear youngb94, a recone. The recone is too expensive, dear SSA, dear SSA, The recone is too expensive, dear SSA, too expensive, Then repair it, dear youngb94, dear youngb94, dear youngb94, Then repair it, dear youngb94, dear youngb94, repair it. With what shall I repair it, dear SSA, dear SSA? With what shall I repair it, dear SSA, with what? With silicone, dear youngb94, dear youngb94, dear youngb94, With silicone, dear youngb94, dear youngb94, with silicone. Any other options, dear SSA, dear SSA? Any other options, dear SSA, other options? With superglue, dear youngb94, dear youngb94, dear youngb94, With superglue, dear youngb94, dear youngb94, with superglue. It depends on the size of the hole dear youngb94, dear youngb94 It depends on the size of the hole dear youngb94, the hole. Too much time on my hands, but I think I captured the essence of this thread.

I really don't know how they arrived at that figure. There are multiple ways to manipulate sensitivity. The website lists a sensitivity of 96.4db, but the T/S I found were from a CA&E article that listed rated sensitivity at 98.2db, which would be a 9db difference. It could be a difference in power (5x more power for a 7db increase, 8x the power for a 9db increase). It could be a difference in "measurement style", meaning it might be an "in car" measurement. Or, decreasing the distance of the measurement by half (.5m instead of 1m) would result in a 6db increase in output, so they may have varied the measurement distance by some amount. If they wired the driver to 4ohm and drove it with 2.83V, that would be a 3db increase. Halving the distance a 6db increase. Combine the two and you have a 9db increase. Or just wiring the driver to 1ohm and giving it 2.83V would also be a 9db increase.

The W205 is a good unit. I use it's prior incarnation, the W200. But I honestly couldn't tell you anything about them as the only utility they have that interested me, or that I paid any attention to, is full control of the H701. $415 for a slightly used W205 that includes everything is a pretty good price though.

Sigh........ This is a case of not being able to take the specifications at face value....Massive is simply playing a numbers game. As I outlined in the Sensitivity article that I linked to earlier (which apparently went unread ), sensitivity "ratings" are not created equal. But if we have the T/S parameters, we can level the playing field with one simple formula I couldn't get the manual on Massive's website to work (the T/S parameters are all blank and Adobe Reader gives me a font error), but from what I could find the relevant T/S for the DMX 12, which is rated 96.4db sensitivity on Massive's website, are; Fs - 31.1hz, Vas - 61.46L, Qes - .33 If we plug those numbers into the formula from the aforementioned unread article, we would find; SPL = 112+10*LOG(9.64*10^(-10)*31.1^3*61.46/0.33) = 89.3db The ACTUAL 1w/1m sensitivity isn't quite as high as advertised there with the "manufacturer rated" sensitivity, eh? I have no doubt you would find an equivalent difference between the actual 1w/1m sensitivity and the "manufacturer rated" sensitivity of the DMX 15 aswell. If anyone can find the T/S parameters, we could "set the record straight" so to speak.

The decrease in sensitivity has had more to do with enclosure size. Lower sensitivity allows for better low frequency extension in smaller enclosures.....the smaller enclosures being beneficial to car audio with our limited real estate, especially as cars (and hence available space) got smaller Power wasn't the "sole reason".

Technology has improved greatly over the past 20 years......however the laws of physics remain the same, which is what we are battling in the realm of sensitivity. An article on sensitivity can be found here (and was also linked in my post in the DVC thread) that will provide the answer to your question: Subwoofer Sensitivity - SSA Car Audio Forum

It's probably in the "order of operation". If you view the help file (or Getting Started or whatever it's called), one of the topics gives you the order to input the parameters, which parameters will auto-calculate and basically walks you through it. You will need to let WinISD auto-calculate certain parameters (which may vary slightly compared to the manufacturer's parameters, in most cases it's not enough variance to matter in the modeling). If you don't do this, chances are good the input figures won't match exactly with what WinISD calculates they should be and it won't let you save the file. Also keep in mind that the Re listed on Fi's website is per coil, so you will need to double Re (since the parameters are with coils in series) when you input it into WinISD. Nope its doing exactly what it's supposed to do. The BTL cannot be modeled in WinISD. Sure it can. The BTL isn't a physics-defying transducer. It's not that modeling programs can't model the BTL. The "issue" is that WinISD and other modeling programs suggest certain "target curves" which the BTL's parameters don't allow it to meet with a reasonably sized enclosure. So yes, while it's best to stay within Fi's recommended enclosure range and not use the modeling programs suggestions.....getting the driver loaded into a modeling program and comparing the differences in enclosure volumes and tunings within Fi's recommended range will help the user determine which alignment fits their needs best or the differences between them.

"The goal of every super sub builder is to eclipse the current king, the Funky Pup. No one may get there, but we keep trying....." - Dan Wiggins

What's up with the shirts from the design contest? Are you guys having them made?

If you are only using a single coil of a DVC driver and leave the other coil open Qes and hence Qts would double, sensitivity would decrease by 3db, motor force (Bl^2/Re) is halved, the inductive corner frequency doubles and power handling is decreased (some argue that power handling is not cut completely in half because the 2nd coil helps act essentially as a heat sink which helps dissipate some of the heat, but I've never seen any testing done to confirm power handling of a single coil compared to both coils). I found this link by accident one day a couple years ago, and it shows a good comparison of a driver's change in T/S parameters with coils wired in series, parallel, one coil driven the other shorted (for both coils), and then one coil driven and the other open (for both coils); woofertester.com If you are interested in the math of why the above happens, you can skim through the formulas for the T/S parameters here on Wikipedia. Resistively Damped Operation can be accomplished by only driving one coil and using a resistor or potentiometer across the 2nd coil to "change" the Q of the driver. This was the entire premise behind the old Ascendant Atlas driver. Yes, they really are. If you want to calculate the efficiency of your subs (or any other speaker), you would use the formula found here; Efficiency (N0) = 9.64 * 10^(-10) * Fs^3 * Vas / Qes *To express as a percent, multiply by 100 *Vas in liters So, for example the Efficiency of a 12" SSA Icon is; 9.64 * 10^(-10) * 29.9^3 * 43.7 / 0.45 = .002502 .002502*100 = .2502% And to verify, to convert this into SPL 112+10*log(.002502) = 85.98db And the sensitivity of the SSA Icon according to their specs; Spl 86.0 1W/1m TaaDaa!! So the SSA Icon converts .25% of the power you feed it to acoustic power, the remaining 99.75% is spent as heat.

The simplest thing to do to learn the basics is to simply read the instructions that come with the equipment. Every single one of them will tell you how to install the equipment.

Then you can use one or the other. Generally the HU would probably have more flexibility in having adjustable slopes, so that would probably be the better way to go.