Curiosity here. What draws your attention and what helps you decide?

Whether the voice coil is silver or copper.

Just kidding.....

Would it help if it was titanium? No way you could blow that up.

Ok, seriously then. Right now, the Tumult looks pretty nice. :drool: Have to see what all is available though.

[This message has been edited by JT Clark (edited May 26, 2004).]

I absolutely hate the way titanium sounds.

funny you bring this topic up elsewhere...

I know darn well I'm not fooling anyone. I won't pretend our exchange didn't partially influence this. I would have started something similar soon anyway.

soundhound, did you have that entire pitcher of margaritas yourself last night? lol I wasn't aware that the voice coil actually emits the sound.

[This message has been edited by JT Clark (edited May 27, 2004).]

How about efficiency and Xmax number on the driver?

Speaking of Xmax, you’d need a yard stick to measure Tumult’s.
If anyone knows a subwoofer driver with that much Xmax distance, please let me know. I’d like to look into it.

Exactly. How much fun would it be to say that your sub displaces more air than your car engine? lol Resonant Engineering is supposed to be making a sub that has 47 mm of Xmax. But that's for cars. I don't know how well it will work for HT. Car subs have to factor in the transfer function of the car in their design. We'll see though.

Xmax is great to look at. Lots of linear response means lots of fun. Especially with a big cone to have massive displacement. Efficiency is alright. The efficiency of the enclosure would be better than that of the driver. Is that what you're saying?

How did you know about that pitcher or Margaritas????

Silver voice coils emit sound, copper ones do not.

On a more serious note.......

One of the tradeoffs of efficiency is enclosure size. Also, woofers that must move great distances forward and back by necessity have very long voice coils - they need this length so that the voice coil does not exit the magnetic gap at any point in it's forward or rearward journey.

The downside of this type of design is inefficiency. This is because of the fact that at any given moment, a good portion of the voice coil is not in the magnetic gap, and therefore is not contributing to the driving of the cone - it is just disapating heat. There are practical limits on how deep the magnetic gap can be to accommodate a longer voice coil. The longer magnetic gaps require correspondingly larger magnets in order to maintain a reasonably high magnetic flux density.

More efficient woofers and subwoofers have shorter voice coils that are completely or mostly contained within the magnetic gap, therefore almost all of the voice coil is instrumental in driving the cone at any given moment. The magnetic gaps are short and the magnetic field is very focused in that small area.

Both approaches are equally good, but one is just more efficient than the other and of course would need less amplifier power. With digital amplifiers that can generate large amounts of power, this amplifier issue is not such a big deal.

The subs that are used in professional applications tend to be of the more efficient type, and are used in large boxes - this generates large output at the cost of a large enclosure.

Inefficient woofers like the Tumult are designed for smaller enclosures that are more acceptable for home environments. To make up for the smaller enclosure (and the smaller piston size - 12" verses 18" for example), these woofers have large front to back excursion capability to move more air.

You either have a large cone with less excursion capability in a large enclosure, or a smaller cone capable of very large excursions in a smaller enclosure.

[This message has been edited by soundhound (edited May 27, 2004).]