CH 802FC

Altec 802 permanent magnet

TO
Field coil Conversion




CH 802FC 


Altec 802, 808 drivers permanent magnet to field coil conversion.
  

 The newest CH 802FC field coil drivers with the ultra pure iron nucleus, and a special potted field coil, for inproved heat dissipation, with  7.5V dc at 2 Amps (warm to the touch). 

A variable regulated DC power supply capable of supplying  up to 8V dc at 5A amps or more is recommended for both coils when operated in parallel.

They may be operated from 6V up to 7.75V DC 


The field coil is a rock solid stand alone coil (no bobbin is used in its construction), potted in the driver body with a special heat transfering epoxy for best heat dissipation, forming together with the central pole piece a solid unit.

For the ultimate in sound reproduction a field coil driver is unsurpassed !. Very musical, warm and smooth !

Total  weight, each:  10 Lbs. 
Field Coil weight 2 Lbs. 7 oz.

Field Coil power consumption at recommended   7.5V   15W


High quality Teflon insuated, silver plated high temperature wire is used for all connections.

Shipping Worldwide

Shipped in one double box with an approximated weight of 22 Lbs. measuring 10 x 10 x 12 inches approximately


A 30-day refund if not 100% satisfied with the CH 806FC field coil drivers. Providing there is no damage and returned in the same condition as received. The buyer is responsible for shipping,
both ways and Custom expenses.
A re-stocking fee of 15% of the total sale price is charged for any returned item.

5 Years limited Warranty.
CH Audio Design  will repair or replace the CH 802FC field coil drivers against any manufacturing defects in materials and workmanship for five years from the delivery date, providing that the field coil drivers are not abused or misused  and kept off rain or water / high humidity or excessive heat, dropped, broken, or modified in any way..



Prices.
 (per pair)

Conversion only.
802 or 808  Type  US $1390.00
Customer provides theit's own drivers, diaphragms must be in good working condition. New diaphragms at extra cost.

Conversion with drivers.

802 or 808  Type  US $1965.00  includes new diaphragms from GPA, all aluminium, same as the original.


Shipping not included in the prices.

CH Audio Design, Co.
FAX  863-229-1683

           





Shown in the graphic are the response curves of a CH802FC 7Vdc  Field Coil converted 802 driver with  Volts DC applied to the field coil. Comparative measurements taken at the throat of the driver very closed to the phase plug. Final frequency response will vary according to the load and frequency characteristics of the horn used.

Measurements taken with color identifying curves and the following field coil applied potentials:


 
The magnetic field strength is directly proportional to the power applied to the field coil up to saturation at which an increase of power to the field coil won't increase the strength of the magnetic field and all that extra energy will be wasted as heat. In this configuration the best compromise is at 7V Volts dc, keeping the heat generation at a minimum with a very flat and high efficiency output throughout the audio response of the driver, extending very well up to the higher frequencies.  
This frequency response is rarely accomplished with the permanent magnet 802 driver.
The frequency response as shown in the graphic is very flat and smooth even using a 1/24 octave spectra  instead of 1/3 as is usually measured for a smoother more forgiving curve.
The frequency response clearly deteriorating as the power to the coil is reduced specially at the top and bottom ends of the frequency spectrum as shown in the gray curve, the response is very similar with  7 and 8 Volts applied, only showing  a relatively small  increase of output at the frequency extremes at higher Voltages.

Measurements are taken at the throat of a converted driver with no horn at 1/24 octave spectra with a 16 Ohms diaphragm  at 1 Watt  (2.83 Volts RMS) sweep sinusoidal signal  from 100HZ to 20,000 Hz., yielding a very high output well over 110db
No dividing  network crossover was used.

The following graphic compares a unit before and after conversion with the recommended 7.5V dc applied to the field coil.
The red curve shows the response with the Field coil, the gray curve with the Alnico magnet.

     


Home Pre-Amps Loudspeakers Drivers Turntables Parts & accessories Technical Papers