Designer:

 Phil

Project Category:
 Bookshelf Speakers

Project Level:
Intermediate

Project Time:

1-8 Hours

Project Cost:

Under $100

Project Description:

The Dayton Audio BR-1 is a 6.5″ 2-Way Bookshelf Monitor Speaker. This is an upgrade to its crossover networks. This modification employs the DC-biasing of crossover capacitors to improve sound. It applies a DC offset to each of the capacitors in the network to reduce circuit distortion. A 9-volt battery supplies the voltage.

Design Goals:
The objective of this project is to improve the sound of the BR-1 speakers by improving the linearity of the crossover networks through biasing of the crossover capacitors. The total parts cost is to be less than $40 for the speaker pair.

Driver Selection:

The drivers are those included in the original BR-1 design
Two Dayton Audio DC160-8 6-1/2″ classic woofers
Two Dayton Audio DC28F-8 1-1/8″ silk dome tweeters

Enclosure Design:

The speaker cabinets are the original Dayton Audio 6.5″ 2-Way BR-1CAB.

Crossover Design:

The DC voltage shifts the signal away from zero, so the waveform does not cross the zero point. This linearizes the waveform of the passive components thus reducing the distortion and improving the sound. The audible effects are increased spatiality, detail, and purity.
Because the battery simply supplies a bias through a high value resistor there is no appreciable current consumption. Battery life is the same as with natural discharge or years. The expiration date of the battery coincides with the need to replace it. Each capacitor in the network is in fact made up of two capacitors of equal value connected in series. Although the battery voltage applied to the center connection of the two capacitors biases them both, no DC voltage appears at the output. The result is sound with increase in detail, smoothness, and resolution. A dead battery has no other effect on the network circuitry, and consequently no other symptoms.
It is easy to make biased networks. Here is how to modify the BR-1 crossover network. The original C1 cap was 6.2uf. To set one up biased for the same value, wire two 12uF caps in series. Then place a 2.2 meg resistor between the caps and tie the + side of a 9Volt battery to the other side of the resistor. The negative on the battery goes to ground. The original C2 cap was 3.0uf. Wire two 6.2uF caps in series. Then place a 2.2 meg resistor between the caps and tie the same 9Volt battery (+ side) to the other side of the resistor.

Tips & Tricks:

Pros
All capacitor types improve. You could also upgrade to the Solen brand, also available from Parts Express.
Cons
The $40 cost to implement is because it requires higher capacitance capacitors and double the parts.

Conclusion:
I am pleased with the results of biasing. Some may describe the effect as subtle. However, the BR-1 is considered by many to be one of the finest sounding speakers and deserving of this improvement. I think you will not be disappointed and find that the design goals were accomplished.

About the Designer:
 I am a high-end audio fanatic. I have been building speakers since I was 10. DC-biasing of crossover capacitors is something that has existed for many years. This trick to help improve the sound of passive components goes back to the early 90’s and before when this technique for speaker systems was used.

Project Parts List: