Dayton BR-1 6-1 User Manual

Construction Workbook

BR-1 2-W ay Ref erence

Monitor System

Congratulations on your purchase of the BR-1 2-Way Monitor System. The
BR-1 was designed by lifelong audio enthusiast and speaker builder Paul
Holsopple. Paul has many years experience designing and building high
end systems. Paul w as commissioned b y Parts Express to design a rela­tively low cost system that could rival the high end name brands in sound
quality. The team at Parts Express then took this design and assembled
the components to create a fairly easy to assemble kit that includes de­tailed assembly instructions and in-depth design tutorials so that the
builder actually learns as he/she builds. The end result is a kit that can be
built in a couple of hours and enjoyed for years and years.

Parts Inventory

Carefully unpack the kit, take inv entory of all parts and make sure that nothing was damaged during shipping. Your
BR-1 Reference Monitor System should include the following:

Part # Qty Description

300-645 1 Dayton BR-1 Cabinet Pair
295-305 2 Dayton 6-1/2" Woof ers
275-070 2 Dayton 1-1/8" Silk Dome T weeters
999-200 2 Crossover Boards
027-352 2 47uF-100V Non-polarized Capacitors (C3)
027-452 2 Dayton .1uF-400V By-Pass Capacitor (C3)
004-8 2 8 Ohm 10W Non-Inductive Resistors (R1)
027-418 2 Dayton 3.0uF-250V Polypropylene Capacitors (C2)
266-832 2 1.5mH 18 Ga. P erf ect La y er Inductors (L2)
027-427 2 Dayton 6.2-250V Polypropylene Capacitors (C1)
015-4 2 4 Ohm 5W Resistors (R2)
015-6.2 2 6.2 Ohm 5W Resistors (R3)
260-721 2 .4mH 20ga. Air Core Inductors (L1)
999-201 2 Terminal Cups
100-140 1 6' long 16 Ga. Sound King Wire
095-282 24 .205" (16-14) F-Disconnect 50 PCS.
260-316B 2 Acoustic Foam 1-1/2" 24"x18"
081-422 8 #8 x 3/4" Phillips Pan Head (for woofer)
081-435 14 #6 x 3/4" Phillips Pan Head (f or tweeter & cup)
999-202 1 BR-1 Instruction Manual

Objective

The objective when designing this system was to off er Parts Express customers a great sounding, low cost kit that
can be quickly and easily assembled while offering a basic lesson in speaker design. Although cost was a factor,
the design must offer excellent perf ormance. In short, a Budget

Many of you have a strong interest in building inexpensive loudspeakers, but do not possess the necessary test
equipment to design from scratch. The BR-1 is an effort to provide an inexpensiv e kit that gets the most out of the
chosen drivers.

Even though cost was a factor in the choice of components and in the final crossover design, the end result is quite
satisfying. The design objective was met with flying colors. The overall sound is smooth and detailed, with a wide
soundstage that belies their smallish size. The tonal balance is on the w arm side of neutral, which is pleasing with
most types of music. Bass also is impressiv e for a 6.5" driver, the f3 being around 43 Hz. Your BR-1s will perform
well for living room, family room, or dorm room music listening or in your high end home theatre surround system.

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Reference

system. Hence the name Da yton BR-1.

The Drivers

Included in your kit are two each of the #295-305 6.5" Dayton mid-woofer and the #275-070 Dayton 1-1/8" silk dome
tweeter . Both units hav e been a hot bed of discussion on the
for this project. The woofer incorporates a treated paper cone, coupled to a rubber surround. The response is generally
well behaved, but does exhibit a peak centered around 3.3KHz.

The Dayton 1-1/8" silk dome tweeter is hands down one of the finest tweeters a v ailable in it's price range! The
response exhibits some peakiness, and the driver seems to ha v e a ‘wandering’ Fs, b ut the sound is on a par with
tweeters that cost far more.

Parts Express Tech Talk board and are good candidates

6.5" On Axis Frequency Response

6.5" Impedance Sweep

The impedance is smooth, but due to the rather large amount of voice coil inductance , rises sharply . Note in the
2KHz area, where this driver will be crossed over , the impedance is 25 ohms . F or this reason, an impedance compen­sation network will be used.

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About Zobels

This simple circuit consists of a single resistor and
capacitor. It is commonly referred to as a Zobel
network, named for the Bell Laboratories engineer
whom invented it. An excellent starting point can be
calculated by using this formula.

R = 1.25 x Re
C = Le / R squared

Re is measured voice coil DC resistance in ohms.
Le is measured voice coil inductance in henries

R is in ohms
C is in farads

I measured the individual 295-305 woofer parameters
using the LMS measurement system, and the Le was
found to be 1.87 millihenries. Using an accurate
ohmmeter, the Re was 6.5 ohms . Using the above
formula:

R = 1.25 x 6.5
R = 8.125 ohms
so
C = .00187 / 66
C = .0000283 farads or 28.3 uF

Although these values will give a good result, actual in box impedance measurements indicated an even better
compensation can be had with a 47uF capacitor and a 8 ohm resistor.

6.5" Impedance w/ Zobel Network

As can been seen on the graph above, the impedance is no w very flat through the crossov er region. F rom 250 Hz to
10 KHz, the impedance is 7 ohms +/- 0.5 ohm.

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1-1/8" Dome On Axis Frequency Response and Impedance Sweep

The Crossover Network and Description

Here is the BR-1 crossover schematic.

The low pass filter is a four element filter . L2 and C2 form an electrical 2nd order filter and yields a 2nd order acoustic
response. The impedance compensation circuit consists of C3 and R1 which eff ectively flattens the woof er’ s induc­tive rise, yielding a smooth impedance curve.

C3 is actually two capacitors, one a 47uf non-polarized electrolytic, with a .10uF Dayton film/foil capacitor wired in
parallel. The reason? NP electrolytics are very cost effective , but exhibit high ESR (equivalent series resistance)
and also have some inductive components. Using a small value high quality capacitor placed in parallel with the
electrolytic will also parallel the undesirable resistance and inductance, thus reducing them greatly. This method is
called bypassing.

The high pass filter is comprised of C1 and L1, and is also a electrical 2nd order yet it yields approximately a 3rd
order acoustic response. R2 and R3 attenuates the tweeter’ s output 6 dB to match the w oof er’ s le vel.

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