raving behemoths

52
Raving Behemoths A Loudspeaker Design Spring 2013 Michigan Technological University Nathan Hunter

Upload: natehunter90

Post on 08-Nov-2014

51 views

Category:

Documents


1 download

DESCRIPTION

Nhunter Speaker Design for Floor Standing PA speakers capable of over 130 dB peaks from an mp3 player

TRANSCRIPT

Page 1: Raving Behemoths

Raving Behemoths A Loudspeaker Design Spring 2013 Michigan Technological University Nathan Hunter

Page 2: Raving Behemoths

2

Table of Contents Functional Description ............................................................................................................................. 5

Figure 1.1......................................................................................................................................... 5

Design Goals ............................................................................................................................................ 6

Size and Shape ..................................................................................................................................... 6

Figure 2.1......................................................................................................................................... 6

SPL Output .......................................................................................................................................... 6

Figure 2.2......................................................................................................................................... 6

Bandwidth ........................................................................................................................................... 7

Voicing ................................................................................................................................................ 7

Directivity ............................................................................................................................................ 7

Design Priorities .................................................................................................................................. 7

Figure 2.3......................................................................................................................................... 7

Visual Aesthetics.................................................................................................................................. 8

Design Consequences .......................................................................................................................... 8

Driver Selection ....................................................................................................................................... 9

Selenium Pro D220Ti Analysis and Selection ........................................................................................ 9

Figure 4.1......................................................................................................................................... 9

Figure 4.2....................................................................................................................................... 10

Dayton Audio D250P-8 Analysis and Selection ................................................................................... 10

Figure 4.3....................................................................................................................................... 10

Goldwood GM-500PB 1" Horn Selection ............................................................................................ 11

Selenium HC23-25 1” Exponential Horn Selection .............................................................................. 11

Figure 4.4....................................................................................................................................... 11

Woofer Analysis and Selection ........................................................................................................... 11

Figure 4.5....................................................................................................................................... 12

Figure 4.6....................................................................................................................................... 12

Figure 4.7....................................................................................................................................... 13

Technical Details ................................................................................................................................... 14

Baffle Step ......................................................................................................................................... 14

Construction ...................................................................................................................................... 14

Inner Layer – Plywood ................................................................................................................... 14

Page 3: Raving Behemoths

3

Outer Layer – MDF......................................................................................................................... 16

Driver Cut-Outs (Katz 2013) ........................................................................................................... 19

Additions ........................................................................................................................................... 22

Amplifier, Port and Handle Cut Outs .............................................................................................. 22

Port ............................................................................................................................................... 23

Paint .............................................................................................................................................. 23

Driver Installation Order ................................................................................................................ 23

Testing and Tuning ................................................................................................................................ 24

Driver Performance ........................................................................................................................... 24

Enclosure Optimization ...................................................................................................................... 25

Figure 5.1....................................................................................................................................... 25

Vent Calculations ............................................................................................................................... 26

Figure 5.2....................................................................................................................................... 26

Cross-over Decisions .......................................................................................................................... 27

Figure 5.3....................................................................................................................................... 27

Final System Documentation ................................................................................................................. 28

1 Woofer Tests .................................................................................................................................. 28

Frequency Response ...................................................................................................................... 28

Harmonic Distortion ...................................................................................................................... 28

Impulse Response .......................................................................................................................... 29

Step Response ............................................................................................................................... 29

Minimum Phase ............................................................................................................................. 29

2 Woofer Tests .................................................................................................................................. 30

Frequency Response ...................................................................................................................... 30

Harmonic Distortion ...................................................................................................................... 30

Impulse Response .......................................................................................................................... 31

Step Response ............................................................................................................................... 31

Minimum Phase ............................................................................................................................. 31

Tweeter Response ............................................................................................................................. 32

Frequency Response ...................................................................................................................... 32

Harmonic Distortion ...................................................................................................................... 32

Impulse Response .......................................................................................................................... 33

Page 4: Raving Behemoths

4

Step Response ............................................................................................................................... 33

Minimum Phase ............................................................................................................................. 33

Overall Testing Results....................................................................................................................... 34

Frequency Response ...................................................................................................................... 34

Harmonic Distortion ...................................................................................................................... 34

Impulse Response .......................................................................................................................... 35

Step Response ............................................................................................................................... 35

Minimum Phase ............................................................................................................................. 35

L – R Difference Plot ...................................................................................................................... 36

Horizontal Off-Axis Response ......................................................................................................... 36

Positive Vertical Off-Axis Response ................................................................................................ 37

Negative Vertical Off-Axis Response .............................................................................................. 37

Waterfall Plot ................................................................................................................................ 38

Testing Complications ........................................................................................................................ 38

Cross-over Schematics ....................................................................................................................... 39

Low Channel Crossover .................................................................................................................. 39

Low Channel Baffle Step ................................................................................................................ 39

Low Channel Bass Boost................................................................................................................. 40

High Channel Crossover ................................................................................................................. 40

High Channel Sensitivity Equalization ............................................................................................. 41

High Channel 10k Boost ................................................................................................................. 41

Finishing Touches .................................................................................................................................. 42

Materials ....................................................................................................................................... 42

Cable creation ................................................................................................................................... 42

As-built Drafting (Newell and Holland 2007) ...................................................................................... 42

Bibliography .......................................................................................................................................... 52

Page 5: Raving Behemoths

5

Functional Description My speaker design will cater to home entertainment needs. These speakers will be used in a home

theater setting and may be called to play electronic music at small venues. For these considerations, a

wide and equal dispersion is necessary, as well as high SPL and decent bass response. The quality of the

speakers should be such that they make two scenarios give me goose-bumps: the bass rumble to the

movie Inception, and bass drops to some of the DeadMau5 and similar artists’ songs.

Figure 1.1

Page 6: Raving Behemoths

6

Design Goals

Size and Shape My speakers will need to be large enough to have a good bass response with high SPL values. My goal is

to upgrade the speakers to operate on stands with the addition of future monetary expansion. The exact

shape is not important, though a box or diamond shape will probably be used.

Figure 2.1

SPL Output Figure 2.1 shows personal listener levels in a situation with moderate stress. The test took place in a

medium sized room, with reflective surfaces. The listener device was positioned at head level at about

half the critical distance from the speakers, roughly 4 meters. The time was 5:00 pm, and I came straight

from a winning broomball game with increased heart rate and adrenaline. At increased stress levels, like

if I had lost, Average SPL levels would increase by 3 to 6 dB.

Figure 2.2

SPL Listening Levels By Song Average SPL Max SPL Headroom Total

Now or Never by Popeska 90 dBW 96 dBW 6 dB 96 dB

Returning Empty Handed by Underoath 88 dBW 94 dBW 6 dB 94 dB

Half Remembered Dream (Inception) by Hanz Zimmer 80 dBW 92 dBW 14 dB 94 dB

Confront Battle (Sword Art Online) by Yuki Kajiura 80 dBW 88 dBW ~10 dB 90 dB

Page 7: Raving Behemoths

7

This puts a minimum required output at 100 dBW at listener location. Crest factor for PA Speakers is

usually between 10 to 15 dB. Distance from speaker to listener requires another 12 dB since most

listeners will probably be between 4 and 8 meters. The ideal venues these speakers will be used for will

have a critical distance starting to level off at -12 dB.

With budgetary realities, the absolute maximum SPL goal I am placing is 120 dB at 1 meter, with no less

than 110 dB as a requirement.

Bandwidth The Frequencies range I would like is from 40 Hz to roughly 16 kHz. Conducting an experiment using

Logic, I edited two songs with an equalizer slowly cutting away low end until I could notice. At 45 Hz I

began to hear a slight thinning of the low end becoming slightly more noticeable at 50 Hz and

unbearable at 60 Hz. The two songs I tested are Sofi Needs a Ladder by Deadmau5 and Stompbox by The

Qemists.

Voicing Using two woofers, I would like to boost the bass output making the frequency response purposefully

not flat. These speakers will be mostly for entertaining purposes and therefore good sounding songs and

movies are more important than flat frequency response.

Directivity I want the speakers to provide fairly equal coverage across a medium sized room or venue. To do this I

plan on using vertically aligned drivers with a Horn tweeter. The speakers will be designed to set up on

stands for when standing head level is optimal (a rave perhaps), and sitting on the floor for when sitting

is required (home theater).

Design Priorities

Figure 2.3

Design Priorities

Size

Dispersion

SPL

Bass response

Page 8: Raving Behemoths

8

Visual Aesthetics The speakers will have two main uses: home theater and small venue dance club. For this purpose they

shouldn’t be distracting enough to take visual precedence over watching a movie, but they should be

stylish enough to look sharp sitting on some stands at the side of a room. The primary color will be black

with possibly an accent color pin striping.

Design Consequences Due to budgetary constraints, sacrifices will have to be made concerning frequency response and size.

The main factors I require are wide and equal dispersion of sound in a relatively high SPL. Reaching this

SPL will require quite a large speaker body, and being sure to have enough bass response to satisfy my

musical tastes will only push that size even larger.

The frequency response won’t be flat as required for a set of mixing monitors, but since I plan to use

these for non-critical listening purposes, a non-flat response is actually preferred. This does however

have an impact on transient response.

Page 9: Raving Behemoths

9

Driver Selection My drivers need to fill the requirements of being capable to reproduce higher volumes and maintaining

an even spread across a room. I’m looking into a horn for the tweeter for nice dispersion across the

horizontal axis, and two woofers in the 8-12 inch range.

Selenium Pro D220Ti Analysis and Selection The Selenium D220Ti has a lot to offer on the side of a smooth frequency response down to about 1.3

kHz. Since I plan to voice the speakers anyway, the slight drop just above 2 kHz shouldn’t be a problem.

The graph has some serious smoothing going on, however Figure 4.2 shows the response at 5W with a

more accurate level of smoothing.

Figure 4.1

Page 10: Raving Behemoths

10

Figure 4.2

Dayton Audio D250P-8 Analysis and Selection This tweeter shows promise on the side of a detailed frequency response plot; however the response of

the Selenium looks flatter. The Dayton Audio tweeter does extend a decent response down to 1kHz,

with an easy bump to fix with a crossover from 1 to 2 kHz, however the RMS power handling is only 60W

and I feel safer with the Selenium’s 120W RMS power handling.

Figure 4.3

Page 11: Raving Behemoths

11

Goldwood GM-500PB 1" Horn Selection This Horn features a wide dispersion angle and the correct thread type for my tweeter; however the

spec sheet does not specify the dispersion angles.

Selenium HC23-25 1” Exponential Horn Selection This horn has the benefit on being the same manufacturer as the tweeter I like, however the internal

plates are an interesting feature. Figure 4.4 shows the Polar response curve.

Figure 4.4

Woofer Analysis and Selection My woofer selection is Dayton Audio PA301-8 12”. Figure 4.7 shows the difference in frequency

between 1 or 2 woofers per cabinet. Figure 4.5 has extended bass range, and Figure 4.6 shows extended

shelf.

Page 12: Raving Behemoths

12

Figure 4.5

Figure 4.6

Page 13: Raving Behemoths

13

Figure 4.7

Page 14: Raving Behemoths

14

Technical Details

Baffle Step The baffle Step Correction frequency is 249 Hz. (f3 = 380/Bwidth in inches) I chose a middle point on the

Baffle due to the Diamond design. The Baffle width I chose is 18.3 inches, or 1.525 feet.

Construction

Inner Layer – Plywood

Page 15: Raving Behemoths

15

Page 16: Raving Behemoths

16

Outer Layer – MDF

Page 17: Raving Behemoths

17

Page 18: Raving Behemoths

18

Page 19: Raving Behemoths

19

Driver Cut-Outs (Katz 2013)

Page 20: Raving Behemoths

20

Page 21: Raving Behemoths

21

Page 22: Raving Behemoths

22

Additions

Amplifier, Port and Handle Cut Outs

Page 23: Raving Behemoths

23

Port

Using Scraps from the original cuts make a square tube with internal dimensions of 10” by 10” and a

length of 6”. The length can be shaved down later in the tuning process.

Paint

1 Coat Flat Black Primer, rolled on to all surfaces

2 Coats Black Truck Bed Liner Spray

Driver Installation Order

1) Horn/Tweeter Combo

2) Active Digital Amp

3) Upper Woofer

4) Lower Woofer

5) Handles

6) Port

Page 24: Raving Behemoths

24

Testing and Tuning

Driver Performance

Original performance of Woofer hooked up to the PCS 2.4 Amplifier with no filter components.

Original performance with 2 woofers hooked up to the PCS 2.4 Amplifier with no filter components.

Page 25: Raving Behemoths

25

Original performance of tweeter hooked up to the PCS 2.4 Amplifier with no filter components.

Enclosure Optimization The Diamond Shape speaker will have a better frequency curve to a similar rectangular box, however it

does come with some downsides. The extra box materials make having a certain volume, weigh more.

Calculating a high and low estimate for the weight of the speakers yielded about 120 to 150 lbs.

Figure 5.1

Page 26: Raving Behemoths

26

Vent Calculations Original calculations shown in figure 5.2 were given for a tuning frequency of 50 Hz.

Figure 5.2

My final decision was to increase the size of the port to a 10” by 10” square port located in the lower

part of the back of the speaker. The length is 5.5”

Page 27: Raving Behemoths

27

Cross-over Decisions For these speakers I have decided to use the Hypex PSC2.400 DSP Active Amplifiers. These will not only

allow for a lot of control in the voicing of the speakers, but also meet my design wish of having active

speakers for ease of operation and portability.

The Crossover frequency will be a 2nd order 1 kHz for the Dayton Audio woofer, and a 1st or 2nd order

crossover at up to 2 kHz for the Selenium Driver

The baffle Step Correction frequency is 249 Hz.

Figure 5.3

Page 28: Raving Behemoths

28

Final System Documentation

1 Woofer Tests

Frequency Response

Harmonic Distortion

Page 29: Raving Behemoths

29

Impulse Response

Step Response

Minimum Phase

Page 30: Raving Behemoths

30

2 Woofer Tests

Frequency Response

Harmonic Distortion

Page 31: Raving Behemoths

31

Impulse Response

Step Response

Minimum Phase

Page 32: Raving Behemoths

32

Tweeter Response

Frequency Response

Harmonic Distortion

Page 33: Raving Behemoths

33

Impulse Response

Step Response

Minimum Phase

Page 34: Raving Behemoths

34

Overall Testing Results

Frequency Response

Harmonic Distortion

Page 35: Raving Behemoths

35

Impulse Response

Step Response

Minimum Phase

Page 36: Raving Behemoths

36

L – R Difference Plot

Horizontal Off-Axis Response

Page 37: Raving Behemoths

37

Positive Vertical Off-Axis Response

Negative Vertical Off-Axis Response

Page 38: Raving Behemoths

38

Waterfall Plot

Testing Complications Testing the speakers proved to be a great complication because of their size. The Radiating Surface of

the drivers is such that getting a good placement of the testing microphone so that it is outside the

radiating surface but close enough to not be affected by early reflections was impossible. No anechoic

chamber was available and therefore the test results may be skewed.

Page 39: Raving Behemoths

39

Cross-over Schematics

Low Channel Crossover

Low Channel Baffle Step

Page 40: Raving Behemoths

40

Low Channel Bass Boost

High Channel Crossover

Page 41: Raving Behemoths

41

High Channel Sensitivity Equalization

High Channel 10k Boost

Page 42: Raving Behemoths

42

Finishing Touches

Materials

1) 2 Sheets of 4’ by 8’ by ½” Plywood

2) 2 Sheets of 4’ by 8’ by ½” MDF Board

3) About 80 FL OZ of Wood Glue

4) 2 sections of 26” by 15” Fiberglass Insulation (for internal dampening)

5) 56 Bolts and Nuts (T-Nuts optional)

6) 2 Powercon Connectors (the Amplifiers Do Not come with power cords)

7) 2 Heavy Duty Extension Cables

8) USB Cable

9) Windows Laptop

10) Cable with Stereo 3.5mm plug to 2 XLR plugs

Cable creation Cut off the Female end of the extension cord. Strip about an inch of the casing, and connect the

Powercon connect to this end.

As-built Drafting (Newell and Holland 2007) All Drafting will be revised to reflect the change in construction. Revisions to increase the stability and

sound proofing of the seams of the box took place during construction.

Page 43: Raving Behemoths

43

Page 44: Raving Behemoths

44

Page 45: Raving Behemoths

45

Page 46: Raving Behemoths

46

Page 47: Raving Behemoths

47

Page 48: Raving Behemoths

48

Page 49: Raving Behemoths

49

Page 50: Raving Behemoths

50

Page 51: Raving Behemoths

51

Page 52: Raving Behemoths

52

Bibliography Katz, Bob. Level Practices (Part 2) (Includes the K-System). January 30, 2013.

Moulton, David. Total Recording. Sherman Oaks, California: KIQ Productions, 2000.

Newell, Philip R., and K. R. Holland. Loudspeakers: for music recording and reproduction. Oxford: Focal,

2007.