Application Note Dynacord C series amplifiers for direct drive - Version 1.1 Authors: J. Plager, Ch. Glück

Application Note
Dynacord C series amplifiers
for direct drive

 Version 1.1

 Authors: J. Plager, Ch. Glück

 Date: 01/02/2021

Communications Systems

Motivation
Dynacord’s C series amplifiers are not only capable of driving low impedance
loudspeakers but can also drive on constant voltage or so called 70/100 V lines in direct
drive (without an output transformer).
70 V or 100 V lines are used to drive a large number of distributed loudspeakers. The
higher voltage results in a lower electric current allowing long cable runs. Direct drives
saves cost and weight of output transformers, the amplifiers drive the 70 V/100 V lines
directly.

Background on 70 V/100 V operation
Loudspeaker for 70 V/100 V lines differ from conventional low-impedance loud speakers
with typical 8 Ω or 4 Ω nominal impedance.
 U2
With: U=R * I and P=U * I => Power = Voltage² / Resistance: P= or U= √P*R
 R for direct drive
 Application Note – Dynacord C series amplifiers

An 8 Ω loud speaker with 100 WMotivation
 power rating, reaches its power maximum with 28 V,
while a 200 W rated loudspeaker will need
 Dynacord’s C series V. So maximum
 40amplifiers power
 are not only capable for the
 of driving low loudspeaker
 impedance loudspeakers but
 can also drive on constant voltage or so called 70/100 V lines in direct drive (without an output
depends on the output voltage oftransformer).
 the amplifier.
 70V
70 V/100 V high-impedance loudspeakers or 100V lines
 onarethe
 used to driveside
 other a largeare
 number of distributed
 designed for loudspeakers.
 a maximum The higher
 voltage results in a lower electric current allowing long cable runs. Direct drives saves cost and
voltage of 70 V respectively 100 weight
 V using an transformers,
 of output internal transformer reducing
 the amplifiers drive the 70 V/100the operating
 V lines directly.
power for the loudspeaker. So the max power handling
 Background on 70 V/100 V operation
 is not determined by the amplifiers
output power, but on the transformation ratio of the internal transformer.
 Loudspeaker for 70 V/100 V lines differ from conventional low-impedance loud speakers with
What might sound a bit confusing offers some serious advantages in fixed installations:
 typical 8 Ω or 4 Ω nominal impedance.
 • loudspeakers with different power handlings can be operated in parallel on one
 
 line (= cable) With: U=R * I and P=U * I => Power = Voltage² / Resistance: = or = √ ∗ 
 
 • adjusting the transformer allows for individual power (= level) adjustments
 an 8 Ω loud speaker with 100W power rating, reaches its power maximum with 28 V, while a
 • thanks to the higher voltage/lower current, long cable runs with lower diameters
 200 W rated loudspeaker will need 40 V. So maximum power for the loudspeaker depends on
 can be used the output voltage of the amplifier.
 70 V/100 V high-impedance loudspeakers on the other side are designed for a maximum
 voltage of 70 V respectively 100 V using an internal transformer reducing the operating power
Important take away: for the loudspeaker. So the max power handling is not determined by the amplifiers output
 power, but on the transformation ratio of the internal transformer.
 • using a 70 V/100 V lineWhat
 does not
 might mean
 sound each loudspeaker
 a bit confusing is advantages
 offers some serious driven with in fixed installations:
 - loud speaker with different
 70 V /100 V. It means that the maximum power handling of the power handlings can be operated in parallel on
 loudspeaker isone line (=
 cable)
 reached when 70 V/ 100 V- are provided
 adjusting to the
 the transformer loud
 allows speaker.
 for individual In (=
 power applications
 level) adjustments these
 - thanks to the higher voltage/lower current, long cable runs with lower diameters can be
 70 V/100 V are signal peaks.used A 100 V line operated at -10 dB below maximum
 runs a little less than 32 V.
 Important take away:
 • many high impedance loudspeakers
 • using a 70 V/100feature a power
 V line does not mean tab,
 eachto adjust isthe
 loudspeaker actual
 driven with 70 V /100 V. It
 max power that speaker canmeans draw. thatThe
 the maximum
 powerpower tabhandling of the loudspeakerfor
 on a loudspeaker is reached
 70 V when
 is 70 V/
 100V are provided to the loud speaker. In applications these 70 V/100 V are signal
 identical to 100 V operationpeaks.
 withAdouble the power.
 100V line operated So
 at -10 dB using
 below 70 Vruns
 maximum vs.a little
 100less V than
 is 32 V.
 a way of reading. • many high impedance loudspeakers feature a power tab, to adjust the actual max power
 that speaker can draw. The power tab on a loudspeaker for 70 V is identical to 100 V
 operation with double the power. So using 70 V vs. 100 V is a way of reading.

 Power Tab 1 2 3 4 5
 Power Tab 1 2 70 V
 3 1.8 W 4
 3.75 W 7.5 W
 5
 15 W 30 W
 100 V 3.75 W 7.5 W 15 W 30 W n.a.
 70 V 1.8 W 3.75 W 7.5 W 15 W 30 W

 100 V 3.75 W 7.5 W 15 W 30 W n.a.

 2 of 8
 June 2020 - Bosch Security Systems, Inc. - Subject to change without prior notice.

Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

Communications Systems

Requirements for direct drive amplifiers in fixed installation
The use of audio amplifiers in direct drive operation has some special requirements
to the amplifier design:
 • the amplifiers needs to be designed for a permanent operation, as fixed
 installations use the equipment in many cases all around the clock.
 • to keep the operating cost low, the amplifier shall have a low idle mode power
 consumption, combined with a high efficiency when driven
 • user interface and connectivity need to suit the application, e.g. power switch
 on the rear to avoid someone turns the amplifier accidentally off, the use of
 Euro-style connectors for easy installation and remote control/supervision via
 a network and/or control ports (GPIOs)
 • the nominal voltage of 70 V / 100 V may not be exceeded, or only very minimal,
 as the transformers are designed for these voltages. Exceeding the voltage
 especially with low frequencies can easily lead to saturation of the transformer
 causing audible distortion, worst case damage the loud speaker.
 • the frequency range needs to be filtered to exclude very low frequencies
 (e.g. 50 Hz, 70 Hz, or 100 Hz) as transformer designs are usually not suited for
 these due to size and cost reasons.
 • the amplifier outputs must not produce any DC. Already a few millivolts on the
 amplifier output can cause the transformers to saturate
 • the amplifiers needs to be stable over the entire load range. A very low signal
 is almost like a no load situation, while maximum output power requires the
 amplifier to drive high and low impedances continuously (see table below).
 • very long cable runs in fixed installations represent a complex load and not a
 pure resistive load. This is a most demanding requirement to prevent dangerous
 oscillations under all load and phase conditions.

Dynacord C-Series with integrated FIR-Drive signal processing are just perfect for these
applications.
Factory presets for 70 V / 100 V that include 3rd order hi-pass filters are available on
dedicated amplifier models. Using the SONICUE sound system software (requires the free
upgrade to firmware 2.x) even more options for e.g. the entire EVID series in 70/100 V are
available.

Selection of the right C series amplifier model
Dynacord’s C series has four different models with different output power. Depending
on the selected operation mode (70 V or 100 V) and the total power handling of all loud
speakers on one line you can select the right model.

The loudspeakers models get selected according their acoustic parameters for a certain
application- then you add up the power handling of all loudspeakers on one line (line).
The output power of the amplifiers needs to be higher than the total power handling
summation.
 U2 (70 V)2 (100 V)2
We have: R(line)= ; R(line)= respect.
 P(total) P(total) P(total)

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Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

Communications Systems

 The following table is showing the relation between a 70 V and a 100 V line and the total power
TheThe
 following table is
 following showing
 table the relation
 is showing thebetween
 relationabetween
 70 V and a
 a 100
 70 VVand
 line a
 and theVtotal
 100 linepower
 and the total
 handling of the loudspeakers:
handling
 power of handling
 the loudspeakers:
 of the loudspeakers:
 Ptotal (W) 1 5 10 15 30 60 100 200 300 600 1250 2500
PtotalP(total)
 (W) (W) 1 1 5 5 10 1015 1530 3060 60 100 100200 200300 300600 600
 1250 1250
 2500 2500
 Rline @ 70 V (Ω) 4900 980 490 327 163 82 49 25 16 8 4 2
Rline @ 70 V (Ω) 4900 980 490 327 163 82 49 25 16 8 4 2
 R(line) @ 70 V (Ω) 4900 980
 RLine @ 100 V (Ω) 10000 2000 1000 490 327
 667 163
 333 82
 167 49
 100 25
 50 16
 33 8
 17 4 8 2 4
RLine @ 100 V (Ω) 10000 2000 1000 667 333 167 100 50 33 17 8 4
 R(line) @ 100 V (Ω) 10000 2000 1000 667 333 167 100 50 33 17 8 4
 The table illustrates why 70/100V loudspeakers with typical power tabs @ 5 – 30 Watts, are
 The table illustrates why 70/100V loudspeakers with typical power tabs @ 5 – 30 Watts, are
 also referred to as “highwhy
 impedance” loudspeakers.
alsoThe tabletoillustrates
 referred 70/100
 as “high impedance” V loudspeakers with typical power tabs @ 5 – 30 Watts,
 loudspeakers.
 are also referred to as “high impedance” loudspeakers.
 To understand better which C series model works best let’s take a closer look at the C2800FDi
To understand better which C series model works best let’s take a closer look at the C2800FDi
 in
 Todirect drive mode
 understand for 70which
 better V andC100 V. model works best let’s take a closer look at the
 series
in direct drive mode for 70 V and 100 V.
 C2800FDi in direct drive mode for 70 V and 100 V.

 C2800FDi
 C2800FDi 70 70 V/100
 V/100 V Direct
 V Direct Drive
 Drive Dual
 Dual Channel
 Channel Mode
 Mode
 C2800FDi 70 V/100 V Direct Drive Dual Channel Mode
 0,0
 0,0

 -0,5
 Delta to nominal voltage in dB

 -0,5
 Delta to nominal voltage in dB

 -1,0
 -1,0

 -1,5
 -1,5

 -2,0
 -2,0

 -2,5
 -2,5

 -3,0
 -3,0
 0 500 1000 1500 2000 2500
 0 500 1000 1500 2000 2500
 Nominal load on loudspeaker line in Watts
 Nominal load on loudspeaker line in Watts
 70 V Direct Drive 100 V Direct Drive
 70 V Direct Drive 100 V Direct Drive
 The diagram is showing for 70 V in blue and 100 V in orange the total wattage (Ptotal) that can be driven per amplifier
 channel and the level deviation to nominal voltage.
 The diagram is showing for 70 V in blue and 100 V in orange the total wattage (Ptotal) that can be driven per amplifier
Thechannel
 diagramand
 is showing
 the levelfor 70 V in blue
 deviation and 100
 to nominal V in orange the total wattage (Ptotal) that can be driven per amplifier
 voltage.
 In example:
channel and the level40 loudspeakers
 deviation with
 to nominal voltage. a 30 W power handling in 70 V represent a total
 maximum power handling of 1200 W, so the amplifiers would need a direct drive load
 In example: 40 loudspeakers with a 30 W power handling in 70 V represent a total maximum
In example:
 capability40 of
 loudspeakers
 1200 orwith
 W W, more.a 30Looking
 W powerathandling
 the needin 70 V represent
 C2800FDi V: aone
 totalamplifier
 maximumchannel can
 power handling of 1200 so the amplifiers would a directat 70 load
 drive capability of 1200 W
power handling of 1200 W, so the amplifiers would need a direct drive load capability of 1200 Wentire
 drive
 or more.from 0 W atup
 Looking thetoC2800FDi
 1225 W with 0 dB
 at 70V: onedeviation- 70 V can
 amplifier channel canbe achieved
 drive from 0 Wover the
 up to 1225
or more. Looking at the C2800FDi at 70V: one amplifier channel can drive from 0 W up to 1225
 W withspectrum
 load 0 dB deviation-
 with 70V can be load
 achieved over theofentire load spectrum to with maximum load
W with 0 dB deviation- 70Vmaximum
 can be achievedcapability
 over the entire1225
 load W, equal with
 spectrum 40 loudspeakers
 maximum load
 capability
 @ 30 of of
 W,1225 1225
 or 80 W, equal to 40 loudspeakers @ 30 W, or 80 loudspeakers @ 15 W.
capability W,loudspeakers @ 15 W. @ 30 W, or 80 loudspeakers @ 15 W.
 equal to 40 loudspeakers
 For a 100V line the C2800FDi can drive up to 2500 W per channel, with a deviation of -2.0 dB to
For For
 a 100V100
 lineVthe C2800FDi can drivecanup drive
 to 2500 Wto per channel, withchannel,
 a deviation of -2.0 dB to
 – 3.0adB. Thatline the C2800FDi
 means: all loudspeakers will beup
 driven, 2500 W per
 but their maximum with
 output willa be
 deviation
 2 dB to of
– 3.0 dB. That means: all loudspeakers will be driven, but their maximum output will be 2 dB to
 3 dB below their maximum output level (which is usually a safety margin kept in many
 -2.0 dB to -3.0 dB. That means: all loudspeakers will be driven, but their maximum output
3 dB below their maximum output level (which is usually a safety margin kept in many
 will be 2 dB to 3 dB below their maximum output level (which is usually a safety margin
 kept in many applications). If the maximum SPL of each is required to achieve the desired
 acoustic result,June you
 2020 can
 - Bosch Security
 use eitherSystems, Inc. - Subject in
 the C2800FDi to change
 bridgewithout
 mode,prioror
 notice.
 consider running a
 June 2020 - Bosch Security Systems, Inc. - Subject to change without prior notice.
 70 V line instead.

 In appendix 1 you find the all diagrams for the 4 C series models in dual channel mode as
 well as bridged mode.
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 Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

Communications Systems

Direct Drive Load Capability of C Series
Choose the matching C series amplifier model depending on your project needs

 Load capability Dual channel mode Bridged mode
 70 V 100 V 70 V 100 V
 C3600FDi not rec. 2 x 2500 W not rec. not rec.
 (-1.5 dB)
 C2800FDi 2 x 1250 W 2 x 2500 W not rec. 1 x 1250 W
 (0.0 dB) (-3.0 dB) (0.0 dB)
 C1800FDi 2 x 1250 W n.a. not rec. 1 x 1250 W
 (-1.5 dB) (-1.5 dB)
 C1300FDi n.a. n.a. 1 x 625 W n.a.
 (0.0 dB)

Or in a different format

 Load capability 70 V operation 100 V operation
 Dual channel Bridged Dual Channel Bridged
 C3600FDi not rec. not rec. 2 x 2500 W not rec.
 (-1.5 dB)
 C2800FDi 2 x 1250 W not rec. 2 x 2500 W 1 x 1250 W
 (0.0 dB) (-3.0 dB) (0.0 dB)
 C1800FDi 2 x 1250 W not rec. n.a. 1 x 1250 W
 (-1.5 dB) (-1.5 dB)
 C1300FDi n.a. 1 x 625 W n.a. n.a.
 (0.0 dB)

n.a.: direct drive is not available for this configuration
not rec.: this operation is not recommended due to efficiency reasons. Please choose next smaller amplifier model for this mode.

Using the factory presets in C series for 70/100 V direct drive
We recommend to use the factory presets on C series for direct drive only if you can’t use
a PC to configure the amplifiers with SONICUE. The factory presets support the direct
drive options with limiter settings for 70/100 V, bridge mode setting if required, as well as
dedicated 3rd order hi-pass filter @ 50 Hz to prevent transformers in loudspeakers from
saturation.

 Factory preset 70 V operation 100 V operation
 Dual channel Bridged Dual Channel Bridged
 C3600FDi not rec. not rec. F10 not rec.
 C2800FDi F08 not rec. F10 n.a.
 C1800FDi F08 not rec. n.a. F10
 C1300FDi n.a. F08 n.a. n.a.

Room EQ and level settings could be made from the front panel – however we strongly
recommend to use SONICUE sound system software with dedicated 70/100 V settings via
the Generic Speaker device, as it will not only have so many more options to better suit
the application, SONICUE also allows a much better tuning result of the system.
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Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

Communications Systems

Using SONICUE to configure C series in direct drive
To operate C series amplifiers you need to upgrade the amplifier firmware on 2.0 (or
higher).
Using SONICUE to configure C series in direct drive

To operate C sound
In SONICUE series amplifiers you need
 system software to have
 you upgrade
 twothe amplifier
 options firmware
 to load on 2.0
 speaker (or higher).
 settings for
direct drive operation to your C series amplifiers:
In SONICUE soundthe
 • connect system software
 amplifier you have
 to speaker in two options
 70/100 to load speaker
 V operation settings
 mode from thefor direct
 device
drive operation to
 catalog your C series amplifiers:
 • connect the amplifier to a generic (passive) speaker and load a sps
 • connect the amplifier to speaker in 70/100V operation mode from the device catalog
 (speaker setting file) from the SONICUE library
 • connect the amplifier to a generic (passive) speaker and load a sps (speaker setting file)
 (C:\Program
 from Files\SONICUE\1.2.0\speakerfiles
 the SONICUE )
 library (C:\Program Files\SONICUE\1.2.0\speakerfiles )

The first
The firstoption
 optionisisofof course
 course thethe most
 most convenient,
 convenient, asparameters
 as all all parameters are matching
 are matching the
 the speaker:
all EVID settings
speaker: all EVIDinsettings
 the EV database
 in the EV1.1 have 70/100V
 database 1.1 havesettings
 70/100 utilizing the potential
 V settings utilizing of
 theC series
FIR-Drive
potential ofDSP. For any
 C series other speaker
 FIR-Drive we any
 DSP. For recommend option two.
 other speaker In any case option
 we recommend you should
 two.
check
In any and
 caseset theshould
 you amplifiers operation
 check and setmode (dual channel
 the amplifiers or bridged)
 operation mode before
 (dualyou connect
 channel or any
speaker (= loading the speaker setting).
bridged) before you connect any speaker (= loading the speaker setting).

After the
After the amplifiers
 amplifiersare
 aresetset
 to to
 thethe
 right operation
 right mode
 operation (dual(dual
 mode channel or bridged),
 channel select the
 or bridged), generic
 select speaker “passive”
 the generic from the
 speaker “passive”
catalog (Setup > Design) and drag on the workspace
from the catalog (Setup > Design) and drag on the workspace
Go to Connect & Setting and click on the generic speaker: the speaker settings flyout will open.
Go to Connect & Setting and click on the generic speaker: the speaker settings flyout will open.
Click on the upload icon- by default you will be directed to the library in Program Files\SONICUE\1.2.0\speakerfiles. Here you can
select: 70 V or 100 V with hi-pass frequencies (24 dB Butterworth) of 50, 80, 100, 150 or 300 Hz.
Click on thefiles
The speaker upload icon-
 include peakby and
 default
 RMSyou will be
 limiters directed
 matching to application
 their the library mode
 in Program
 and an Files\SONICUE\1.2.0\speakerfiles.
 additional lo-pass filter at 17 kHz
Here youannoying
(to avoid can select: 70Vfrom
 HF, e.g. or 100V with hi-pass frequencies (24 dB Butterworth) of 50, 80, 100, 150 or 300 Hz.
 pilot tones).
The speaker files include peak and RMS limiters matching their application mode and an additional lo-pass filter at 17
kHz (to avoid
The loaded annoying
 speaker HF,
 file will bee.g.
 shownfrom
 as pilot tones).
 a label in the flyout. Click on the speaker and the amplifier (channel) to make the
connection. You can use the Label function to provide a name for your generic speaker.

The loaded speaker file will be shown as a label in the flyout. Click on the speaker and the amplifier (channel) to
make the connection. You can use the Label function to provide a name for your generic speaker.

 6 of 8

Application NoteJune 2020 - Bosch
 – Dynacord Security
 C series Systems,
 amplifiers Inc. -drive
 for direct Subject to change without priorBosch
 ©2021 notice.Security Systems, Inc.

Communications Systems

 Note: speaker settings are being stored in the generic device and are included in copy/paste – while the label is not.
 Note: speaker
Note: speaker settings
 settings are being
 are stored
 being in the
 stored generic
 in the device
 generic and are
 device andincluded in copy/paste
 are setting,
 included – while the
 in copy/paste label is
 –upload
 while thenot.
 label is not.
 Soififyour
 So yourdesign
 designis is using
 using multiple
 multiple speaker
 speaker lineslines that utilize
 that utilize the
 the same same
 setting, you justyou
 havejust have to
 to upload the speakerthe speaker
 file once, file
So if your
 once,use
 then design
 then is using
 use duplicate
 duplicate multiple speaker
 (or copy/paste)
 (or copy/paste) lines that
 to create
 to create more utilize
 more
 speakers the same
 speakers
 with setting, you
 with setting.
 the required just have
 the required setting. to upload the speaker file
once, then use duplicate (or copy/paste) to create more speakers with the required setting.

Once the setting is loaded you can utilize all advantages of SONICUE for tuning your system.
Once the setting is loaded you can utilize all advantages of SONICUE for tuning your system.
Once the setting is loaded you can utilize all advantages of SONICUE for tuning your
system.

 June 2020 - Bosch Security Systems, Inc. - Subject to change without prior notice.
 June 2020 - Bosch Security Systems, Inc. - Subject to change without prior notice.
 7 of 8

 Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

Communications Systems

 Appendix
Appendix 1 1

 June 2020 - Bosch Security Systems, Inc. - Subject to change without prior notice.
 8 of 8

 Application Note – Dynacord C series amplifiers for direct drive ©2021 Bosch Security Systems, Inc.

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