ADIRE - EXTREMIS 6.8
MIDRANGE-MIDWOOFER GO BACK TO PRODUCTS PAGE
The Extremis 6.8 is our entry in the high end of midwoofers. Designed to take on - and beat - drivers like the legendary ScanSpeak 8545, Seas Excel offerings, and other high-end European drivers the Extremis 6.8 simply takes everything to another level.
Start with flexible T/S parameters. Parameters that allow use in common monitor boxes. The T/S parameters of the Extremis 6.8 lend themselves to vented boxes in the 14 to 28 liter range, and with tunings in the 30-40 Hz range. Extension to 30 Hz anechoic promises in-room output down to the 20-25 Hz range! Our favorite application: 21 liters, tuned to 33 Hz with a 2" flared port of 8" length. Clean and flat anechoic response to 35 Hz, and in-room extension to the low 20s.
And the Extremis 6.8 backs up that extension, too. The first midwoofer ever with over 1 inch of peak-to-peak LINEAR excursion, the Extremis 6.8 can out-perform many 10" drivers in terms of clean linear output down deep. The linear output of the Extremis 6.8 is a whole new realm - output levels equal to two (or more!) of other company's high end midwoofers, from a single driver.
How does this motor achieve all this performance? Simple - it uses our XBL2 ™ motor structure. This completely unique and patent-pending motor structure allows for extremely high levels of linear stroke without loss of BL, excessive moving mass, or other problems associated with long stroke. With this motor technology, you can have it all - wide bandwidth, low moving mass, and high stroke. Here's a graph of the BL curve of this amazing driver:GO BACK
So the bottom end is there - what about the top end? The first indication that things are right is the extremely low inductance - just 0.13 mH! The inductive roll-off of this driver is up beyond 8 kHz! So the extension potential is there... And we used as much of that potential as possible with a carefully selected exponential flared polypropylene cone, matching smooth-mount polypropylene dustcap, and butyl surround combination with hand-applied edge damping treatment on the rear. The frequency response is free from large breakup modes that plague stiff cones (like metal or honeycomb Kevlar™) - just clean even response to 5 kHz, where the driver has a very mild dip in response as it transitions to a controlled roll-off. The impedance is extremely smooth and flat, making crossovers in the typical 1-3 kHz range very simple:
Here's a few more plots showing the outstanding performance of this driver:
This driver is a natural for crossing over at the 3-4 kHz range, and when used with a 2nd order electrical network at 3.5 kHz, a 6th order roll-off is achieved, meaning the transition to the tweeter is quick and comb filtering is kept to an absolute minimum. The short voice coil, aluminum former (required for something with this much linear stroke), and full copper sleeving all help to widen the bandwidth of this driver.
The impedance is also very flat and free from ripples - as shown on the impedance graph, you can see the impedance doesn't double over minimum until the 7 kHz range! And the very slow impedance rise from 150 Hz to 8 kHz is deliberate - the result of a thick plating of copper on the pole piece. A full 1mm thick copper sleeve is used on the pole of this motor, cutting the inductance above 500 Hz by a tremendous amount.
The Extremis 6.8 has something the other high end drivers don't though: video shielding. The Extremis 6.8 uses a neodymium magnet system which is inherently low in stray flux. In fact, the stray field just 2" from the motor is less than 100 mG (the Earth's magnetic field is 5 times larger!). This driver can be placed within inches of a CRT or magnetically sensitive equipment without a problem. Try that with the other high end offerings, and you'll need to invest in good degaussing coils!
The motor is also extremely compact. Thanks to the large 35mm diameter disc of high-grade neo, the motor is just 70mm in diameter - less than 3"! And the height is very short for the stroke provided - just a scant 42mm (less than 1 ¾"), which is only possible with our XBL² technology. The motor is acoustically hidden from the back of the cone, resulting in the most open, free-flowing, reflection free motor structure available anywhere. The cone never "sees" the motor. Ever.
Contributing to this open structure is a quality cast aluminum basket. This basket is a full 4mm thick at the mounting flange, for an extremely solid and stable mounting platform. The moving assembly is held in perfect alignment. And while there are just four thin basket arms, each basket arm is heavily ribbed for reinforcement, so that the lightweight and compact motor simply can't move, twist, or vibrate.
The suspension is just as advanced - a custom pressed linen progressive roll spider with flat attachment, the spider allows up to 15mm of motion from the driver, but maintains near-perfect linearity over a 26mm range of motion. Combined with a thin, linear shallow roll rubber surround with a custom edge termination, the result is a suspension ideally matched to the capabilities of this motor.
The T/S parameters are as follows:
The Extremis 6.8. Wide bandwidth, high output, amazing linearity. Finally you CAN have it all!