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.

Page 2

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.

Page 3

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.

Page 4

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.

Page 5

Most loudspeakers including the BR-1 use drivers mounted on a flat baffle. One problem encountered here is the fact
that the tweeter’s relativ e acoustic center is set ahead of the woofer’s relativ e acoustic center. In gener al, a flush
mounted tweeter’s acoustic center is aligned with the front baffle . A typical 6.5” woof er’s relative acoustic center is
set about 1-1/2” behind the tweeter . This means that when fed a signal at the crosso ver frequency, the woofer’s
output will be delayed 110uS relativ e to the tw eeter. F or successful filter summation, this m ust be dealt with.

The method used to compensate for this delay in the BR-1 is the use of asymmetrical filters. Normally one would
use the same crossover topology for both high pass and low pass filters. A 3

rd

order high pass acoustic slope is
used with a 2nd order low pass acoustic slope to allow for the time delay. This technique takes advantage of the
phase delay differences between the two filter types and results in a flat summation and allows both drivers to be
acoustically in-phase with one another at the crossover frequency .

The crossover filters were designed to achie ve a flat o v erall response. The BR-1 measures on axis within +/- 2.0dB
from 100 Hz -12 KHz. Flat frequency response is desirable so that all frequencies are reproduced with the same
loudness over the loudspeaker’ s bandwidth. In itself , flat frequency response does not ensure a good sounding
loudspeaker. But targeting flat on axis perf ormance is the first step in designing a high performance loudspeaker .

Another, arguably more important goal is flat off axis frequency response. Man y times a speaker can measure flat on
axis, but the off axis curves suffer from dips in the response. This is due to insufficient driver overlap , usually
caused by using too high of a crossover point f or the lo w frequency driver. Good off axis perf ormance will av oid the
so-called Venetian blind effect. What is the Venetian blind effect? When the seated listener mo v es horizontally from
directly in front of the speaker, the treb le or high frequency response drops off dr amatically. A loudspeaker which
exhibits good off axis response can be listened to well away from directly in front of the speakers and excellent
performance will still be enjoyed.

On/Off Axis Response of BR-1 System

Note that even 60 degrees off axis, the woofer is producing a reasonably flat response without deep nulls or
cancellations throughout the crossover region.

Page 6

Individual Driver and Summed System Response

The above graph was produced with the microphone at a distance of 45", on the tw eeter’ s axis . I pref er to use the
slightly farther then 1 meter (39.37") distance to be more in the far field, to get a better representation of how the
drivers will blend. The response is within the +/- 2.0 dB window to 12KHz. In fact, the response is commendably flat
from 300 Hz to 3.5KHz. It can be seen that the acoustic crossover occurs at 2.1KHz. These curves have been
smoothed 1/6th octave.

The woofer’ s peak at 3,200 Hz is still present, and it should be noted that a par allel notch filter could be used in the
low pass circuit to reduce it’ s effect. One was omitted to keep in the spirit of a low cost design, since this would add
three more crossover components per speaker . I found the peak’s audibility to be relatively benign how ev er .

It’s w orth discussing the parallel notch filter because it is a handy circuit that is used to control frequency response
peaks. A parallel notch filter consists of a capacitor, an inductor, and a resistor all wired in par allel with each other,
then this circuit is placed in series with the driver.

For a 8 ohm woof er with a typical “peak” (about 5 dB), use the f ollowing f ormula for a starting reference.
C = 1/ (33 * freq of peak)

L = .025 / (freq of peak squared * C)
With the 295-305 woofer , mounted on the BR-1 baffle , the peak is centered at 3,200 Hz. So …
C = 1 / (33 * 3200)

C = .0000094 farads or 9.4 uF
L = .025 / (10240000 * .0000094)

L = .000259 henries or .259 mH
To find the value of R, you first must find the Q of the peak. Do this b y finding the –3dB points on both sides of the peak.

For the 295-305, these –3dB points are 2,500 Hz and 3,700 Hz. Now use this f ormula to calculate the peak’s Q.
Q = freq of peak / (Fh – Fl)

Q = 3200 / (3700- 2500)
Q = 2.67

We can now calculate the resistor value by:
R = Q / square root of C/L

R = 2.67 / square root of .0000094 / .000259
R = 14.05 ohms

Page 7

So the values for our proposed parallel notch filter is a 9.4uF capacitor , .26mH inductor , and a 14 ohm resistor.
Unlike the impedance compensation filter discussed earlier, this filter is harder to gener ate from just design formulas.
It is best to use some means of measurement to validate the result. Please note that adding this notch filter to the
existing BR-1 crossover will change the filter roll off and will necessitate a low pass filter redesign.

Reverse Tweeter Polarity

Reversing tweeter polarity is a quick check performed with even order filters to test the overall phase relationship that
exists between the tweeter and woof er. The goal is to achieve a fairly deep , symmetrical null at the crossov er fre­quency when the tweeter polarity is reversed. If one is witnessed when the tweeter polarity is reversed, then it can be
assumed that a good phase relationship exists when the tweeter is connected with normal polarity .

System Impedance and Phase

Page 8

The system impedance and electrical phase is quite smooth, with a nominal 8 ohm impedance. This loudspeak er will
be an easy load to drive for most any amplifier. Ho w ever due to the 82.5 dB sensitivity, a minimum of 75 watts per
channel is recommended.

The center to center driver spacing is 5.75", with the tweeter being offset 1" in a mirror image pair . The tweeter is
flush mounted to the baffle, while the woofer is recessed only to the top of the basket. This was done due to the 5/8"
thickness of the enclosure material.

The Cabinet

The Dayton BR-1 cabinet
uses 5/8" thick MDF and
has an net internal
volume of .52 cubic feet.
It utilizes a EBS (ex­tended bass shelf)
alignment and is tuned to
38 Hz with a rear mounted
port. This tuning results in
a f3 of 43 Hz. The box
dimensions are 8-5/8"
wide, 14-1/4" high with a
depth of 11", giving it a
small footprint suitable for
stand mounting. It is
recommended to place
the tweeter at, or slightly
below ear height of a
seated listener.

The center to center
driver spacing is 5.75",
which is an important
consideration. Whene ver
you have two drivers
combining output, as is encountered around the crossover frequency there will be some interf erence patterns. This
interference will create dips and peaks to the frequency response. The greater the distance between the two driv ers,
the more intense this undesirable interaction.

The generally accepted maximum center to center distance between the two drivers is equal to one wavelength
(13,560) at the proposed crossover frequency .

Max center to center distance = 13560 / crossover frequency
So in the case of the BR-1:
Max CTC = 13560 / 2100 or 6.45”
Since the tweeter to woofer distance is 5.75”, the BR-1 is well within the one wavelength tolerance and will provide a

uniform radiation pattern.

Page 9

BR-1 Assembly Instructions

1) Installation T ools Needed

• Phillips Screwdriver • Wire Cutter / Stripper

• Hot glue/gun or RTV Sealant • Small pliers

• Soldering iron • Crimp tool

• Silver or Electronic grade solder • Utility knife

Crossover Assembly Note

Warning!! The correct assemb ly and wiring of the crossovers is critical to the proper operation of this speaker
system. In a worst case situation, an improperly wired network can damage your receiver or amplifier! Please
double and triple check all values and wiring.

Assembling the Crossovers

1. Install all components on the boards in their proper location. When installing R1, position it so that air can
circulate around its body . Before mounting (C3) to the p.c. board, it needs to be “b ypassed”. C3 is actually
two capacitors, one 47mfd. electrolytic bypassed with a .10mfd Dayton poly film/foil. This w as done to
improve the acoustics of the electrolytic capacitor . To bypass the capacitor , simply parallel the tw o capacitors
together and wrap the smaller “poly” cap leads around the larger electrolytic cap leads and solder. Trim
excess “poly” cap leads and use the electrolytic leads to mount the “bypassed cap” to the p.c. board.

2. When positioning components try to keep lead lengths to a minimum. Note: The (L1).40mH inductor should
be mounted on its side to minimize the interaction between the two coils on the board. You can trim the
length of the leads on the (L1) inductor without effecting its’ value. Using a utility knife, scrape off the enamel
coating on the trimmed lead ends so it will accept solder.

Page 10

3. To help reduce the risk of components rattling on the
p.c. board, (especially the inductors) use RTV
sealant or hot glue to mount the components to the
p.c. board. We recommend using hot glue due to its
faster setup time. If you use RTV sealant, you may
need to let it setup over night, before proceeding
with the assembly.

4. Solder all component connections on the p.c. board
using silver or electronics grade (60/40) solder . At
this time, you should also solder the riveted .205
terminal connections. A properly soldered connection
appears shiny and smooth. We recommend using a
soldering iron with a wattage rating between 20­30watts. Using wire cutters, trim off all excess
component leads.

5. Cut the supplied wire into 6 pieces approximately 12"
long. Strip the insulation on all wires back
about 3/8"-1/2".

6. Using a crimp tool, crimp the .205 terminals on the wire leads. To ensure a tight connection, gently squeeze
the push on terminals with a small pair of pliers. Note: If you prefer, you can solder the wires directly to the
p.c. board and drivers instead of using the connectors.

Page 11

7. The locations where the input and driver output wires connect are
clearly marked on the p.c. board. While observing proper polarity
attach all input and driver wires to their respective mounting termi­nals. Example: To attach the input wire, take the positive (+) input
wire and connect it to the “IN+” terminal. Next, take the negative (-)
input wire and connect it to the “In-” terminal. Repeat this step for the
woofer, tweeter and other crossover. Again, it is very important to
observe the proper polarity!

8. At this point, it is a good idea to label each wire to ensure proper
hook-up. Masking tape and a marker will work fine.

3) Cabinet Assembly Instructions
A. Installing the Crossovers

To mount the crossovers we recommend using hot glue due to its faster setup time. If you use RTV sealant, you
may need to let it setup ov er night, bef ore proceeding with the assemb l y. Y ou could also use screws, but they
can be a little difficult to install and you run the risk of driving the screw through the finished side of the cabinet.
No crossover mounting screws included.

1. Position the crossov er board on the inside bottom of the cabinet against the bac k wall with the wiring
facing outward.

Page 9

2. Glue the crossover in place.

Page 12

3. Pull the “labeled” input wire through the terminal cup hole and while observing proper polarity connect the wire
to the terminal cup. The positiv e (+) input wire should be connected to the “red” binding post.

4. Orient the terminal cup with the binding posts toward the bottom and install using the small #6 screws and a
phillips screwdriver .

5. Repeat these steps for the other speaker cabinet.

B. Install Acoustic Damping Foam

We’ve included tw o (2) sheets of acoustic f oam, one sheet for each speak er .
Acoustic damping foam absorbs internal standing waves inside the cabinet and prevents reflections to the woofer

cone. You can install the foam using hot glue, R TV sealant or spra y adhesiv e (3M Super77) if a v ailab le.
A simply way to cut the foam is to leave the two sheets “nested” together while cutting. Place the foam on a flat

surface and cut the foam with a straight edge and a utility knife. Make medium depth cuts with several strokes.
Do not try to cut through the entire depth of foam with one cut.

Page 13

1. The foam must be cut to fit internally on the right/left side walls, rear , top and bottom panels . Do not apply it
to the front baffle. Cut the foam to the dimensions shown in Fig. 1

FIGURE 1: Foam Cutting

2. Install the foam on the back of the cabinet first and trim around the port tube. Mak e sure it does not obstruct
the airflow to the port tube, as this will alter the tuning of the box.

3. Next install both sides and then top and bottom. The bottom piece of f oam will simply la y on top of the crosso v er .

4. Position the “labeled” woofer and tweeter lead wires through the f oam and run to their respective driver openings.

Page 14

C. Installing Drivers

Put sealing caulk around the woofers prior to mounting. When applying caulk it is a good idea to first roll the
caulk between your fingers to “thin out” the caulk bead. The tweeter is supplied with a gasket so it does not need
sealing caulk. Putting sealing caulk on the tweeters mounting flange may not allow the faceplate to mount flush
with the baffle.

1. Attach each wire to the appropriate driver terminals while observing proper polarity (positive to positive,
negative to negative). The tweeter has a red paint dot on the positiv e terminal. If y ou decide to solder, be
careful not to apply too much heat to the driver terminals especially the tweeters.

2. Install the drivers using the #8 (large) screws for the woofers and the #6 (small) screws for the tweeters. Be
careful not to over tighten the screws and strip the wood.

Page 15

Speaker Placement

Many loudspeakers are designed without regard to baffle step loss. If a woofer has a midband sensitivity of 88 dB for
example, and is mounted on a large infinite baffle (like your living room wall), it will maintain the 88 db sensitivity right
down to it’s r ated f3. All frequencies, even the large lo w frequency wa v elengths are supported by the large wall.

But speakers are usually mounted in boxes with varying degrees of baffle width. At a given frequency determined by
the baffle dimensions, the lower frequency wa v elengths start to ‘wrap’ behind the baffle . This is called a 2 pi to 4 pi
transition and will result in a 6 dB loss in an anechoic chamber.

This is a complicated subject which I only want to touch upon here, but suffice it to say that a typical two way
speaker in a normal listening room will exhibit more like a 3 to 4 dB loss in the bass region. If left unchecked, most
speakers will sound too thin with too much midrange output.

The BR-1 was designed with 4 dB of baffle step compensation which results in surprising bass output for a 6.5”
diameter woofer . The midband is rolled off to match the woof er’ s natural in-room response to achie ve the e xcellent
bass performance. The trade off is a loss of some midband sensitivity, with an overall sensitivity of about 83 dB.

In most rooms, you will find the BR-1 to sound best placed approximately 3 feet from the rear wall and mounted on
appropriate speaker stands. Ideally you want to place the speakers so they are at least 3-4 ft from side walls if
possible

Special comments from the designer

"I was pleasantly surprised when I fired up these loudspeakers to give them a first listen. I have lived with
the design for a few months now and my opinion remains unchanged. I sincerely believe the Dayton BR-1
gives serious competition to commercial loudspeakers costing two to three times its modest price. Could
they be better? Sure they could. For someone interested in ‘tweeking’, I would suggest using thicker MDF
for the cabinet and brace it adequately. It might be beneficial to replace the 47uF NP
in the lowpass with a
notch filter might be worth exploring too. Upgrading the R2 and R3 resistors to a Axon, Mills or equila v ent
type is a possibility also as I suspect a thin layer of “grunge” will be removed. All in all, I consider the
‘stock’ BR-1 to be an outstanding value and tough to beat as-is." -Paul Holsopple , designer

polypropylene

type as discussed previously in the “Crossover Network” section, a

electrolytic

capacitor

Dayton Loudspeaker Co ., PO Bo x 52, Springboro, Ohio 45066-1158

© October 2001 Dayton Loudspeaker Co.