Originally Posted by exxxtreme

So about excursion im confused about subs. I keep hearing Sundown, Obsidian, soundqubed. I keep hearing Obsidian is sundown... Is it a lower quality? And what about soundqubed? Tons of talk but do they have just as good of a product as obsidian?

Originally Posted by exxxtreme

Reason I ask is I bought 6 Hifonics HFX12D4 and then realized they only have 7mm of travel. So I returned and am looking for a great sub, for as affordable as possible. With looking for affordable I do want quality.
Main name brands I keep hearing is RE Sex, Alpine Swr, Mb Quarts premium, but then everyone keeps saying soundqubed, obsidian, sundown way better, Im lost with all the forum talk. Looks like the guys on here have way more real hands on experience. Would like some real advice.
Power. I will be running hifonics brutus. Max wattage will be 3 2400. Im thinking more likely to run 2 amps. I did buy a upgraded alternator and 2 caps already. Will be running 12s in a ported box about 2cu ft with port.

Originally Posted by OscarMartinez15

Would a trade between 2 15 inch Memphis Mojo SVC and RE Audio XXX 12's be okay? I have the Mojo's.

Originally Posted by DevilDriver

Excursion is a large contributor to high output in any driver on the market. Typically, larger excursion (seen visually as how far the cone moves in and out) means more sonic output. However, with excursion come challenges.

As the driver moves outward, the voice coil begins to move out of the gap. This causes a drop in the magnetic force (or BL) and results in a few negative effects, including a large theile/small parameter shift, lower efficiency (magnetic flux decreases), less control over the voice coil (transient response increases, making the driver sound sloppy), and introduces distortion into the output.

Knowing these effects, there was a need to design a parameter to describe the limit of excursion while still remaining “linear”. The idea here was to define a point at which all other parameters remain the same and also consider the limits at which disortion becomes audible. This parameter is referred to as Xmax and, although extremely valuable, is highly controversial. The issue comes back to the actual definition.

Overhang
Traditionally, Xmax has been defined by the overhang method. Overhang is the length of coil in mm that extends past either side of the top plate and is determined by the formula:
Xmax = gap height – [voice coil length/2]
The theory here is that this measurement considers the maximum amount of travel the driver is capable of with the same number of windings (of the voice coil’s wire) in the gap. Once the number of windings decreases, the effects listed above will begin to occur. This is still one of the most commonly used definitions and does work fairly well, but it does not consider several factors, including the behaviour of the magnetic fringe field, any suspension compliance non-linearities, any inductance non-linearities, or InterModulation Distortion. From this lack of refinement, several other definitions have come about.

8mm In the Gap
Digital Designs Audio, famous for their high SPL drivers, use an "8mm in the gap" method. In their opinion, the percentage of coil still in the gap is what matters, rather than the overhang. For DD Audio, this is an important method to consider. They typically use tall top plates and, as such, have very long magnetic gaps that cannot be considered by the traditional overhang method of measurement. Using the overhang method has consistently given DD Audio very low numbers, although most newer and more accurate methods do as well. The issue here is that once the coil begins to move out of the gap, there is a drop in BL, whether there are 8mm of coil in the gap or not. Using DD’s measurement method, this drop in BL would not be accounted for. Due to the large gap that DD uses, this drop is not as drastic as others, but it is a drop in BL regardless. This measurement method also does not cover any of the other issues mentioned with the overhang method.

DUMAX and Klippel
There are two revolutionary measurement systems now available: the DUMAX from Dave Clark and DLC Designs, as well as the Klippel, developed by Dr. Wolfgang Klippel. These measurement systems compare BL with respect to x(mm of excursion). They also consider suspension compliance (Cms) as this will create many of the same issues that a shift in BL will. This is done as 1/Cms (which=Kms) with respect to x(mm of excursion). Both of these demonstrate through a graph the measurement of BL and Cms through both the positive and negative strokes. An example of each graph can be found below:
BL from Klippel
Kms (1/Cms) from Klippel
BL and Kms from DUMAX (scroll down to the graph section)

DLC defines Xmax as the smaller of 1: half of the peak to peak excursion over which BL retains 70.7% of it’s rest position value or 2: half of the peak to peak excursion over which Cms retains 25% of it’s rest position value. These values represent approximately 10% distortion, which is often considered the point of audibility. By using this method, we consider the full flux field as well as the suspension’s limits. Xmag is considered half of the peak to peak excursion of the 70.7% limit for BL, Xsus is considered half of the peak to peak excursion of the 25% limit for Cms, and Xmech is considered half of the peak to peak excursion of the absolute limit of the chassis. The smallest of these 3 values is considered Xmax.

Considering these points is imperative, as BL and Cms distortion accounts for roughly 80-85% of all distortion present in any given driver.

When is linear truly linear?
Dr. Klippel has made a push to consider other factors as well, primarily measuring inductance with respect to x(mm of excursion). This has more to do with how far the driver can be pushed before compromising some level of sound quality, rather than how far the driver can be pushed before compromising excursion. This opens up a possibility to consider cone break up, lead slap, any mechanical noise, air rushing around the basket or pole vent.

The definition of Xmax as defined by the Audio Engineering Society as:
“The voice-coil peak displacement at which the “linearity” of the motor deviates by 10%. Linearity may be measured by percent distortion of the input current or by percent deviation of displacement versus input current.”

On the other hand, Dr. Klippel defines Xmax as such:
“The voice-coil peak displacement Xmax at which either the total harmonic distortion dt or the nth-order modulation distortion (where n=2 or 3) exceeds 10% in the sound pressure radiated by the driver in free air excited by the linear superposition of a first tone at the resonance frequency f1=fs and a second tone f2=8.5 fs with an amplitude ratio of 4:1.
The total harmonic distortion dt assesses the harmonics of f1 and the modulation distortion are measured by the modulation components f2± nf1 according to IEC 60268.”

Summary
With all that said, I personally agree with Dr. Klippel’s definition of Xmax. It considers Total Harmonic Distortion and, as such, seems to closely represent the sonic qualities over excursion. The issue here is that it does not consider Inter-Modulation Distortion and does not necessarily match hearing perception across the board.

To summarize, looking at Xmax can describe potential output while remaining linear, but it is important to understand the application of Xmax and how it is measured. If you see a graph from the DUMAX or Klippel measurement systems, I would be much more inclined to believe the parameters posted. Remember to look deeply into all information provided and that with any audio driver, the whole is greater than the sum of it's parts.

Cheers,
Neil

Originally Posted by almond

the ear is a very unreliable way of determining if sub A is louder or cleaner than sub B. with out any kind of mechanical meauserments it's hard to tell what was really happening.

Originally Posted by Kryptonitewhite

So the solo really is only good up to 24.5mm? After that nothing? As the tutorial said, it's highly debated.

I had several S15L7's and 2 AA 15" Avalanches....both had an Xmech of 32mm, but the Avalanche had 27mm Xmax and the L7 only had 16.5mm.

1: the L7 moved just as far as the Avalanche, and sounded as good, but a little louder ( same excursion but more cone area, and cuz distortion makes louder)
2: 16.5mm Xmax is 1/2 it's 32 Xmech and you couldn't hear much change...more importantly..you couldn't suddenly hear it pass Xmax over 1/2 it's excursion. At full excursion, it sounded just as good as the Avalanche.


If I had the money, I'd love to have an 06' XXX 18 that's within Xmax at full excursion, 54mm... but for a fraction of the cost, and having experienced Kicker vs super Xmax subs...I would simply like to get the Xmech, bull**** and argument free, but I'd be more than glad to have a separate thread to debate the issue.

Funny when someone asks for any spec, at that given moment it's "why? what for? youre doing something wrong. you don't know what youre talking about" but then ask for a diff spec, same thing.

What I mea is I used to have this same argument about Xmax a year ago. When the HaVoc came out (Ascendant Audio) there was a huge fight that Xmax doesn't matter on that sub. Now it's Xmech doesnt matter on this sub. people get this idea that subs only work for 1 application. SPL sub. SQ sub. Bandpass or sealed cuz of EBP. Ported or 6th order.

A sub is a sub. they all have different characteristics that may make it easier to build a more efficient (as in box size or port lenght) box for desired output, but all subs can work in all boxes.

Specs are given for a reason. I want those specs. If I am interested in a motor, don't tell me I don't need to know displacement or torque or horse power. This is a place to go to get info. I want that info. Start a new thread on why, I'll be glad to go there and debate all day :P

Not tryin to be a dick, just never seem to get answers, only static and skepticism

Originally Posted by Dilbeckskate

Ok EXCURSION is pretty much all ur bass output
And a pig part to having big bass and high SPL is having a subwoofer that has alot of excursion,
but that subwoofer also has to be able to stay linear, meaning it has to move up and down rapidly without bending the cone, like you see the videos of the subwoofer trick where the subwoofer looks like a wave or bending, those might have alot of excursion, but the cone is not stable at that high of a linear streach for the woofer