dpaton wrote:
The tuning of the box and it's relationship to the transfer function of your car have more to do with the sound quality of a sub than the driver. Generally critically or slightly overdamped systems (Q = 0.707-0.5) sound tighter, and are easier to tune "flatter". Tuning the box so that you take advantage of the cabin gain of your car is also helpful, since higher dampening systems usually have a higher Fs and a smaller volume. The second thing to look out for is Hoffman's Iron Law: Small, low, efficient: pick two. If you have a small box, you need a big amp and a driver that has a very large Xmax and a larger Xmech to handle the power and displacement required. If you need the bottom octaves and don't have much power, use a big box. If you need it small and loud, it just won't go that low. In my own personal experience, I've had very good luck with 10s and 12s in smallish sealed boxes like yours, so it begs the question, what's wrong with your system now? -dave |
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I guess working for a manufacturer, I gain a different perspective on this. With vehicles, usually you have a set amount of room that you can use, so you must choose a driver that is ideal for your situation, and will give you the Qtc. and extention you desire in the enclosure you have room for.
But beyond that, I believe the driver has a huge impact on how the system will sound. I suppose in the past, most manufacturers used an overhung motor, so all drivers had the same transient response and distortion products. It is rare that you would see an underhung motor used in a driver, so the differences in drivers usually were in the resonance (fs) and Q's offered.
Now that has changed. You can find drivers with better transient response and lower distortion. The former is caused by high inductance. Overhung motors have long coils, and therefore high inductance. But if you find a driver with low inductance, then transient response will be improved.
Several companies now offer low distortion drivers. They do this by optimizing the BL over excursion to stay linear, and thereby greatly decreasing distortion. As Dr. Kipple, David Clark, and several other prominent engineers have shown, 70% of the distortion you hear in a driver comes from a nonlinear BL curve. The rest comes from Cms nonlinearities over excursion (suspension stiffness changing causing about 23% of the distortion you hear), and Le (inductance) distortion (transient errors from high inductance).
To save space, I won't go into the actual designs implimented by each company right now. But I will later if you guys want me to. JL Audio offers a clever way of flattening out the BL curve in their W7. Their downside as compared to the other designs is they aren't very flux efficient. This can be seen by the high Qes. We developed a new motor to offer flat BL as well which we call XBL^2. IMO it is the superior approach, but I can back that opinion with factual data to make it less bias. In our design we gain a very large throw in a shorter motor, have lower inductance (shorter coil), and are much more flux efficient. BTW, the XXX mentioned above uses our XBL^2 motor as well. And finally Orion offers one in their H2 subwoofer. Theirs is just a slightly different version of ours, but is also much less flux inefficient which is why they have such a high Qes.
So in conclusion, I think there are better SQ drivers offered now using these technologies. If you are looking for the best SQ driver, then I would recomend looking at a driver using the technology mentioned above. But I will warn you. We have found that a couple people are used to the distortion other speakers produce, and don't like the transparency the low ditortion drivers offer. So personal preference is a factor.
Steven Kephart
Adire Audio