Quote:
Originally Posted by navin If B&T is following this thread...I'd like to see a midbass with a edge wound voicecoil, copper shroting ring, vented pole piece, NdFeb magnet system with the coil outside the magnet system coil dia = 1/2 cone dia, single spider till 6" and dual spider for 8"+, Butyl half roll high damping surround, cast or moulded frame, etc... |
Navin, I am mentioning the following driver from Illusion Audio because it is used for car audio, although there are several other home hi-fi drivers that Peerless makes that would be a closer match.
Illusion Nd series drivers: (aka The Carbon Series)
1. Edge wound, flat-wire, high-temperature, low inductance voice coil.
2. The motor uses an aluminium support tube which doubles up as a pole piece. This sorts out the impedance, although not as efficiently as a copper shorting ring would, due to lower conductivity. No copper shorting ring possible since the driver employs a inverted Nd motor, open-gap design. Only way out is to construct the U-pot (in this case, it doubles as the top-plate) of the motor in copper. However, the product designer was of the opinion that the driver did not show significantly worrying impedance irregularities to incorporate this.
3. One step ahead of the vented pole piece cooling design is the patented open-gap motor. The v/c is not only vented due to construction, it is also vented to the front of the driver rather than the back so as to allow fresh air to continuously cool the driver rather than the warmed air in the enclosure.
4. If the v/c dia on the driver is increased to any larger, the magnet will become large enough to completely cover the front radiating surface of the cone. Illusion drivers cannot use voice coil sizes like the Dynes etc. The 6" still use upto 40-50 mm dia coils, and the largest 15s etc use 3-4" coils. Larger than average, permitting above-average thermal power handling, but not oversized. 65-80mm voice coils would leave very little exposed radiating area.
5. All Illusion drivers were intended for shallow mounting application. Although they are drivers with longest throws for a particular power handling and size, the geometry of the driver will not permit a second spider to be added unless it is incorporated in the front of the subwoofer (somewhat like Strokers). The advantage of the geometry is that the center of gravity of the moving parts is quite vertically centralized due to the inverted voice coil, hence multi-point centering can be easily avoided, and using a progressive spider keeps the excursion in check, and linear. As you would agree, it is difficult to have dual spiders for most neo-based drivers, inverted or not.
6. All inverted motor Illusion drivers use die-cast Aluminium baskets, and symmetrical half-roll, butyl rubber surrounds. The latter is pretty much mandatory for any good car audio speaker, I would think. The overall weight of the driver is very low due to the Nd magnet, plus the magnet isn't directly bolted to the basket. hence the basket uses multiple thin ribs/ spokes. These minimize interference with the back wave and there is no question of ringing. I am sometimes disgusted when subwoofer drivers with a power handling of over 400W rms use stamped steel baskets. They should listen to those guys with the driver mounted upside down. Just in case, this matters, although you didn't bring it up, the spider is vented on the top and bottom too. Most manufacturers overlook this aspect. It causes drivers to behave non-linearly due to pressure build-ups in the chamber.
7. In addition it uses a super light and rigid carbon fiber cone. The drivers do not use mass loading like
all other major SQ subwoofer manufacturers do, to lower Fs at the expense of sensitivity. Add to that, the advantages of having a narrow gap, and a neo motor with practically no flux leakage and the driver easily boasts efficiencies atleast 6dB higher than most conventional drivers. Even in 'in-car' scenarios, they suffer zero flux loss to adjacent metal body parts, which is unavoidable with all other conventional driver formats. They wouldn't handle as much power as some 12W7s etc, but with a 95 dB sensitivity and 400W rms of power handling (for a 12), it doesn't leave much to be desired for SQL buffs. Sure, if you're the dB drag types, you should feel most obliged to buy DD Audio and some earmuffs.