CH 806FC

Altec 806 permanent magnet

Field coil Conversion

CH 806FC 

Altec 806  permanent magnet drivers conversion.

 The newest CH 806FC field coil drivers with the ultra pure iron nucleus, an special field coil, will work very satisfactorily with 6.75V dc at 2.3 Amps with low heat generation (warm to the touch). A variable regulated DC power supply capable of supplying  up to 7V dc at 5A amps or more will be fine for both coils when operated in parallel. They may be operated from 6 up to 7V DC.

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

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

Total  weight, each:  8 Lbs. 
Field Coil weight 2 Lbs.
Field Coil power consumption at recommended 6.75V   14.2W

Shipping Worldwide

Shipped in one double box with an approximated weight of 20 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 806FC 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. 
Small format Type 806, 804 etc.  US $1245.00
Customer provides the drivers, diaphragms must be in good working condition. New diaphragms at extra cost.
  • Conversion with drivers. 
Small format Type 806, 804   US  $1765.00 includes new diaphragms from GPA, all aluminium, same as the original.

Shipping not included in the prices.

 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.

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


Shown in the graphic are the response curves of a CH806FC 7Vdc  Field Coil converted 806 driver with 2.5V, 5.0V,
6.0V, 7.0V and 9.0 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:

Black   2.5V
Gray     5.0V     
Green   6V
Red      7V  
Blue      9V  For testing purposes,  do not  apply higher than 7V for continuous use.

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 6.75V 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 he higher frequencies.  
This frequency response is rarely accomplished with the permanent magnet 806 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  6.5 and 7 Volts applied, only showing  a relatively small  increase of output at the frequency extremes at higher Voltages.

The following graphic compares a unit before and after conversion with the recommended 6.75V dc applied to the field coil.
The red curve shows the response with the Field coil, the gray curve with the Alnico magnet.
Measurements are taken at the throat of a converted driver with no horn at 1/24 octave spectra with an 16 Ohms diaphragm  at 1 Watt  (2.83 Volts RMS) sweep sinusoidal signal  from 100HZ to 22,000 Hz., yielding a very high output well over 110db.  No dividing  network crossover was used.

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