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Main design considerations

Being designed as a generic mfb correction module EVE supports a wide variety of driver, enclosure and 

loopgain choices. Because of this generic setup it is not possible to provide a common set of component 
values, to assist the user with making educated choices the following information is given. 

Servo / Motional 

feedback does not work with 

Helmholtz resonator

 based enclosures such as bass reflex boxes.

 

Servo loop gain

EVE has been designed to offer a theoretical maximum servo loopgain of 20dB, refer to below graph for the 

relation between servo loopgain and a Q0.7 enclosure frequency response. Servo loopgain determines:

The 

F3mfb

, the higher the amount of gain the lower the resulting 

F3mfb

 will be.

Maximum SPL, the 'extra' energy is rerouted to low extension.

The amount of second and third harmonics supression available .

Piratelogic EVE 2020.0 Manual

  

 05/03/2022@07:37:22

Page 7  

Summary of Contents for EVE

Page 1: ...EVE servo evaluation pcb VERSION 2020 0 SUBJECT TO PERMANENT DEVELOPMENT Piratelogic EVE 2020 0 Manual 05 03 2022 07 37 22 Page 1 ...

Page 2: ...test case 11 Basics 11 Example ScanSpeak 12 Free air response 12 Closed box response 12 Loop phase 13 Loop bandwidth 13 Amplifier bandwidth 13 Building EVE 14 Power requirements 14 Choosing Components 14 Onboard Regulators 14 PCB Layout 15 Top layer names 15 Bottom layer names 16 Bottom layer values 17 PCB circuit 18 Driver Selection 19 Overall design considerations 19 Main selection criteria 19 A...

Page 3: ...odule Designing building servo drive systems like described in this manual requires a thorough understanding of and working experience with the underlying electronics An engineering degree and experience with component level board repair is strongly advised This is NO starter project Availability Bare EVE printed circuit boards without components are available for 15 euro a piece by sending an ema...

Page 4: ...ED FC 2012HRK 620D LINE GAIN 5K B25P POTENTIOMETER 652 3362P 1 502LF PXE BIAS 5K B25P POTENTIOMETER 652 3362P 1 502LF PXE GAIN 5K B25P POTENTIOMETER 652 3362P 1 502LF R1 1501 R0805D SMD resistor C4310 0805W8F1501T5E R11 1001 R0805D SMD resistor C17513 0805W8F1001T5E R12 1002 R0805D SMD resistor C17414 0805W8F1002T5E R13 1003 R0805D SMD resistor C17407 0805W8F1003T5E R14 4702 R0805D SMD resistor C1...

Page 5: ...uild around IC1b and IC4b and the 2nd order LPF around IC4a PXE input buffer The pxe input buffer processes the incoming accelerometer current signal and performs the following functions The accelerometer current souce signal enters EVE at PXE IN where it passes rf filter R9 C7 which corner freqency is set to 7234 hz To avoid microphonics make sure to use a NP0 for C7 To adapt for jFet Vgs variati...

Page 6: ... phase inverter IC2B is used to build the symmetric OUTPUT 3 and 1 Power 7812 and 7912 are standard voltage regulators to allow EVE from being operated from the power amp rails Eve s current draw is 40mA max use R33 and R34 to bleed of excessive rails regulator inputs are max 35V Improvements over EVE version 2018 Input buffer Low noise pxe buffer with adjustable accelerometer bias voltage Through...

Page 7: ... not work with Helmholtz resonator based enclosures such as bass reflex boxes Servo loop gain EVE has been designed to offer a theoretical maximum servo loopgain of 20dB refer to below graph for the relation between servo loopgain and a Q0 7 enclosure frequency response Servo loopgain determines The F3mfb the higher the amount of gain the lower the resulting F3mfb will be Maximum SPL the extra ene...

Page 8: ...work to reach the required excursion as such one is discouraged from using Qbox values above 1 as it will limit system efficiency and SPL Low Pass Filter The 3rd step is to decide on a low pass filter frequency Flpf using the drivers datasheet as reference EVE s onboard lowpass filter follows a 2nd order Sallen Key setup as such it is advised to choose Flpfat least 1 octave away from the first occ...

Page 9: ...y too low 3dB 10hz may look nice on your spec list but will severly stress your driver when connected to a 500 watt Class D amp Perform a LF sweep before deciding on how low you want things to go and keep in mind that average electronic music starts at 20hz In case EVE is to be used with existing active enclosures it s build in rumble and lowpass filters may need disabling Disabling the rumble fil...

Page 10: ...ngstroke drivers with a high Xmax will typically exhibit a relative high signal output when compared to standard drivers To accommodate for this ajust PXE GAIN which sets the gain for the incoming accelerometer signal Highpass filter To avoid problems caused by the difference between the mirror output and opamp input DC levels a capacitor C8 was added to the circuit The lower pole for the accelero...

Page 11: ...tive a closed loudspeaker enclosure behaves like a spring mass system with its response transitioning from compliance dependant controlled by the spider surround to purely mass controlled with F3box as the turning point inbetween From an electronical perspective it behaves similar to a standard second order high pass filter with the corresponding 12 dB Oct slope and 180º phase shift at F3box In or...

Page 12: ... drivers free air resonance frequency F3driver Using this driver TS parameters as a reference the choosen F3mfb frequency would equal 45hz or higher Closed box response The graph on the right shows the impedance phase plot for the driver mounted into a 3 7 Little One closed box both F3box and it s accompaning phase shift have shifted towards 101 hz To assure stable operation the F3box phase shift ...

Page 13: ... for C16 values Amplifier bandwidth When using EVE with third party power amplifiers make sure their lower bandwidth pole starts sufficiently low a too high value may negatively effect loop stability due to the introduction of LF phaseshifts As a rule of thumb make sure your amplifier lower F3 pole is at least 1 tenth of your desired F3mfb As an example please find the following points of attentio...

Page 14: ...ymmetrical psu capable of delivering 15V 80mA minimum such as done by this kit https www tubeland de product_info php products_id 13 Choosing Components EVE s primary goal is to offer a bare bone proof of concept servo loop solution and has been designed with cost effective readily available non exotic parts in mind The used 5532 opamps dates back to 1978 and by no means represents the state of th...

Page 15: ...PCB Layout Top layer names Please note EVE is currently sold as bare PCB only and as such does not contain any components Piratelogic EVE 2020 0 Manual 05 03 2022 07 37 27 Page 15 ...

Page 16: ...Bottom layer names Piratelogic EVE 2020 0 Manual 05 03 2022 07 37 28 Page 16 ...

Page 17: ...Bottom layer values Piratelogic EVE 2020 0 Manual 05 03 2022 07 37 28 Page 17 ...

Page 18: ...PCB circuit Piratelogic EVE 2020 0 Manual 05 03 2022 07 37 29 Page 18 ...

Page 19: ...sign details Cone size material make sure the driver cone maintains pistonic motion in the area mfb will be active in The larger the driver the harder it will be for it to maintain pistonic operation For high SPL designs daisy chaining multiple smaller diameter drivers might yield better results then a single large one small lightweight sturdy cones are favourable over large and heavy ones High BL...

Page 20: ...d 10M brown black blue gate resistor resulting in a lower pole of 10 61hz See the sensor circuit below for more info Without loop compensation the resulting phase shift might introduce subsonic instabilities below 100hz For more information google the 545 service manual and lookup the circuitry around TS549 for further details All StarBass sensors have their lower pole sit at 2 7hz making them sui...

Page 21: ...r Available with 3 primary axis see Motor assembly variants for more info Current status beta 2 samples available Starbass Stripper Low MMS 2P motional feedback accelerometer for use with voicecoil diameters between 20 and 25 mm designed to be mounted horizontally inside the voicecoil former Current status beta 1 samples available StarBass 26 Low MMS 2P motional feedback accelerometer for use with...

Page 22: ...ingOn C1 with 90 primary axis no dustcap disassembly required usability depends on Vctravel risk of unbalanced loading with low MMS cones 2 ClingOn C2 with 45 primary axis no dustcap disassembly required Risk of unbalanced loading with low MMS cones risk of cone breakup information pickup Accelerometer and placement choices for flat panel motor structures ClingOn C3 with 0 primary axis usage of Cl...

Page 23: ... Initial version by CC 19 03 2021 Added warning for photovoltaic effect of limiter leds thx esl63 15 06 2020 Updated schematic captions by CC 16 12 2021 Added warning on microphonics for C2 9 28 06 2020 Added Accelerometer Selection information 05 02 22 Added functional info on C8 08 07 2020 Updated BOM schematics 21 02 22 Added external psu info thx Thoren 05 08 2020 Added engineering degree requ...

Page 24: ...s and formula s are great but witnessing things react the way they do is gold Building well performing MFB systems isn t an easy thing to do but using EVE with an StarBass equipped driver allows you to skip the hardest parts Created from an affordable budget the Little One 2 way system is my proof of concept that MFB is still very much alive and kicking and it s successor the Grown Up 3 way is on ...

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