This document:
Has been designed to present to potential investor (electronic drums builders, artists, sound reinforcement system manufacturers) the idea of the electronic drum acoustic amplification system developped by thomas ANTOINE. It presents the author, the objectives and golas, as well as some construction details concerning the first prototype built by the author. This system is reffered to roomboom system in this document.
The Goals :
Through the development of this system, patent filing and this communication, I intend to find business partner for the industrial development of this idea under business agreements. The first step towards patenting has been done through the filing of a french patent. A one year period starting from oct 1st,2004 gives international priority to the author for patenting outside France.
About the author (roomboom@tiscali.fr)
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My name is Thomas ANTOINE; I am a mechanical
engineer working in noise and vibration. I graduated from the national
Institutes of applied Sciences in Lyon where I specialized in NVH (Noise,
Vibration & Harshness) More precisely, I worked on saxophone reed
design using newer materials than cane, like composite compounds with kevlar,
glass and carbon fibers. Through this study I understood that even if a reed
made of compound materials presented the same vibroacoustic behavior as a
cane reed with enhanced life and consistency, for the saxophone player, it was
not meant to replace the original reed ÉTaking care of some weakness of century old
development of musical instrument does not allow to replace them, but rather
to give the musician a wider choice of his instruments, and that is part of
his art. Today, I am the supervisor for the design
simulation and testing team of Metravib RDS in Lyon, France. We mainly deal
with NVH issue in the industries of energy, transportation, defense and our
activities is based upon testing, signal processing, design and simulation
engineering to solve tricky NVH issues. |
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Drums, drumming and Hi Fi
As for my personal hobbies, I started playing the drums 14 years ago, and I always was interested in the drum equipment and construction. During a stay in the US I bought an old Gretsch kit that I always use.
A few years later, as I was more into Jazz playing, I bought another Gretsch jazz kit the day after a concert where the great AndrŽ Ceccarelli played this kit.
Along with that I have been chasing Hifi components for my own audio system at home for the last 5 years, and got in touch with people providing DIY audio kits.
Electronic
drums
A few years ago, I got a Yamaha DTX 2,0 electronic drum kit.. At the time, this kit was just issued and appeared at a very interesting valueÉI used it as a practice kit in my flat , and rehearsing with other MIDI equipped musicians (keyboard and wind controller).
Later, I equipped some old acoustic drums with mesh heads and trigger, and was happy with the feeling and the look of such a kit.
Lately, I came back to Lyon, met with the band I used to play with and started recording again with my DTXÉonly this time, it was wired to a G4 MAC full of neat samples and got all the neat sounds for the demoÉAfter the recording process, it appeared that keeping some electronic sounds in our tunes was indeed interestingÉbut the problem of reproducing the electronic or sample sounds to the audience arose.
The
idea
So my goal was to develop a PA system dedicated to drums and electronic percussion that would keep the look of a standard kit, and sound as much as possible as oneÉ. From there the idea is pretty straightforward: why not using the drums shell as speakers cabinets?
The answer was to transform an old 22 12 13 16 low quality kit into my Òroom boomÓ system inserting power amplifiers and speakers in the place of carry heads, keeping all lugs and hardware, put some mesh heads on both sides, and have the kit looking just as an ordinary kit, with sound source placed in close vicinity of the original heads to try to reproduce as much as possible of the original sound field from the kit.
The real goal here is to give the electronic drummer full control of his sound intentions in providing him with a sound reproduction system that can match the drum brains capacity for enhanced musical expression to an audience.
On september 4th, 2004, I met by chance Mino Cinelu, world famous percussionist, user of various instruments including some electronic KORG wavedrums. He kindly accepted a chat with me, and I exposed the idea broadly. He confirmed the interest of correct reproduction of electronic percussion along with visual aspects, which gave me even more confidence and motivation in my project.
The
patent
A patent has been filed on octobre 1st 2004 concerning this system. The french INPI has registered this system under nr 0410379 on oct 1st , 2004.
Acoustical
objectives:
The goal in this project is to have a Ç natural È sounding drum kit (as far as shells are concerned, regular cymbals are used along with it to complete the Ç normal È aspect) thus, replacement of vibrating carry head membranes with speakers will help in having some parts of the sound spectrum at the same origin as a real drum.
This kit is also designed to fit most of playing situations : rehearsal, concert in small clubs where the volume of the subwoofer and satellites can be adjusted to meet the acoustical an environment requisites.
An analysis of the sound distribution around a drum was thus necessary. From various books and calculation, some basic principle in the reproduction were kept:
1 Ð the sound
emission from a vibrating membrane is varying a lot as frequency increases
2 - Most modes carrying the ÒimpactÓ sounds are
multi nodal diameter modes, and are radiating mostly in the axis of the shell
(a direction perpendicular to the membrane plane).
3 - Most modes responsible of the distinctive pitch
an character of a membrane are multi nodal lines modes, radiating sounds at
higher frequencies in direction closer to the plane of the membrane.
From those behaviors, it has been decided to place a low/mid speaker in place of the resonant heads for tom toms and tweeters baflleds on the shell.
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The physical radiation from a membrane |
The technical solution : boomers pointing
down (replacing the carry head) and tweeters around the shell |
The Logo.
Construction:
The 22x14Ó bass drum was turned into a 125 W subwoofer, with two air vents (diam 100, length 220mm) tuning the 65 liters volume at 47 Hz, driven by a 15 Ò BEYMA (15K200) speaker fed by an HYPEX 200W parametric amplifier, necessary to boost low frequencies with the tiny load volume (15Ó speakers shall be loaded with 65 Ð 150 liters volumes). The amplifier is attached to the bass drum, making this subwoofer a standalone system (usable for Home cinema application for example).
The 12Óx8Ó and 13Óx9Ò tom toms were similarly equipped with 8Ó BEYMA speakers facing downwards and tweeters on the side. Dedicated crossover filters were developed to match this particular speakers arrangement. Those are fed with an external 4x160W amplifier boosting the filtered signal from the subwoofer amp after active filtering. All hardware concerning this prototype is described in the annex below.
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The Ç bass drum subwoofer È in construction showing the bass drum front wall with two air vent holes and the special cut for the 15K200 Beyma.As weel, the HS200 Hypex plate amplifier |
the 22 È bass drum in construction, showing spacers reiforcing the front panel and drum shell , as well the amplifier Ç box È where the Hypex HS 200 will be housed sealed from the main volume |
The 12 È tomtom with the 8 È Beyma speaker (tweeters are not yet installed / original mounting hardware has been removed and replaced by sturdy Pearl ISS) |
Tweeters are the tricky part. Two tweeters are mounted onto each tom-tom at 180¡ with given phase relationship between them to try to recreate a radiating dipole.
Tom toms can be oriented freely as they are mounted onto Pearl hardware, and the high frequency directivity can thus be onsite optimized for the most natural sound.
All shells have been stiffened inside, particularly the bass drum to handle the high energy vibrations.
Wiring:
Neutrik Speakon connectors have been used to wire the loudspeaket. Those are 4 connectors plugs, and both pairs are used, one for the 8Ó speaker (8 ohm impedance) , the other for both tweeters, serial mounted (16 Ohm total impedance).
Electronics:
To feed properly each speaker and in order to control the sound field, the solution of active filtering and multichannel amplification was chosen. For the prototype, a behringer ultra curve pro and a monacor /Stageline PA1004 are used. The crossover frequency has to be aroud 3 to 4 kHz, with care taken in the gain for the tweeters as those whistand only 30 W program power each and 15W AES power.
ÒLiveÓ tests
Tests have been
conducted in my bandÕs rehearsal room, not the best from an acoustic
standpoint, but the goal was to replace regular shells by the roomboom system
and basically checkout those majors parameters :
¯ The behavior of the system in an Ç acoustically loading È environment, ie bass, guitar and voices played live just like in regular rehearsal situation AND the system sound itself.
¯ The sound level obtained from the system played along with regular percussion instruments (snares, cymbals,É)
¯ The sound quality and Ç coherence È of such a device in live situation.
The system performed remarkabely well from all those points, added with a nicer visual aspect. Several tweakings for EQ (from the sound source) and crossover levels and frequency cutoff lead to Ç natural È sounding kit. No feedback / false triggering due to the acoustic or vibratory environment has been encounteredWith a 300 W bass amplifier and 100W guitar amplifier + 100W voice, playing fairly loud rock nÕ roll, the level from the roomboom system was more than sufficient (way over a normal kit) and the mighty bass shook the guts of the bass player (however, no-one reported sick after the test).
Triggering equipment and sound modules :
DDRUM Ç red shot È triggers are mounted onto each tom toms. A K&K Ç sensitive È piezo transducer upon the snare, and the bass drum features a home built sensor made of a small plywood plate onto which a piezo is glued, backed on each side by foam under the head. This system lowers even the noise from the head, and the principle can be applied on all toms, s presented in the picure below :
All batter heads are DDT, carry heads are black triggerheads.
Attempts were made with a YAMAHA DTX 2.0, the roland TD6 module, quickly replaced by a ROLAND TMC 6 trigger to midi converter plugged onto a G3 macintosh with Native Instruments Ç Battery È samples (very nice).
Alternate use:
As the bass drum bears its own amplifier and speaker, it can be used in any X.1 audio sound system. The components constituting this subwoofer have indeed some audio quality (most DIY subwoofer kits use similar or lower power amps).
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Two views of the 22 È bass drum used as a subwoofer for home audio (batter head was not installed at the time) / a regulat mesh heads is plced in front of the loudspeaker for protection and appearance. |
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Sound details:
As the 13x3 piccolo snare used with this kit is a real acoustic drum mounted with mesh head on top, and regular ebony head on bottom (to match the rest of the kit) with the original snare on it, I can even get some ÒdirtÓ on my drums neat sound with the snare buzz for even more presence and natural sounding kit.
ANNEX /1 LOUDSPEAKERS
ANNEX /2
AMPLIFIERS AND FILTERING
Subwoofer (bass drum) power amplifier
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Hypex Electronics B.V. Kattegat 8 9723 JP Groningen The Netherland |
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The HS200 bristles with the same great set of features that
has made the big brother HS500 a hit: true 4th order LR crossovers
(independently adjustable for the satellites and woofer), switchable phase, a
single EQ band, and superior sonic performance. Add in 200W of power
into 4 ohms, and you have a plate amp with few equals. The HS200 includes a few special features not found on it's
bigger brother: speaker-level inputs, for one. The end result is a slick,
slim package that looks top-notch, and is completely functional. It
is advisable to place the amplifier in an airtight compartment ? |
Power
output 200W into 4 Ohms /
125W into 8 Ohms
Subsonic
filter 20Hz/-3dB, 24dB/Oct
THD <0.02%
Damping
factor 600 @ 100Hz/8 Ohm
Input
Impedance 10 kOhm RCA
1
kOhm high power inpu
features :
- overheat
protection
- DC protection
- phase shift 0¡ -
180¡
- power-on at input
signal
Dimensions 175mm x 330mm
Weight 2,5 kg
Warranty 1 year
Satellites (Tom Toms) Active crossover
SUPER-X
PRO CX2310
2-Way
Stereo/3-Way Mono Frequency Crossover with Subwoofer Out
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Satellites (Tom Toms) power amplifier
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STA-1004
Number 24.3160
4-channel professional PA amplifier,
with integrated crossover network and limiter.
* Different
operational modes can be selected (mono, channel groups, 8½ bridge, crossover
network, subwoofer)
* Crossover
network, adjustable crossover frequency 50-2,500Hz (-24dB/oct.)
* Limiter
function can be switched independently for each channel
* Soft
start
* Protection
against short circuit and overheating
* Temperature-controlled
fan
* LEDs
for overheating, overload (clip), output signal, and operation
* Supplied
with 2 covers as a protection against maladjustment
Technical
Facts Amplifiers
Output power
RMS power
Stereo 4½ 4
x 250WRMS
Stereo 8½ 4
x 160WRMS
8½ bridge operation 2
x 500WRMS
Max. power 1,400WMAX
General Information
Inputs 1.23V/30k½
Frequency range 20-20,000Hz
S/N ratio > 80dB
Crosstalk attenuation > 60dB
THD <
0.1%
Power supply 230V~/50Hz/1,800VA
Admiss. ambient temp. 0-40 ¡C
Dimensions 483x90x410mm
Weight 16.2kg
Connections 4
x XLR, bal. 4 x 6.3mm jack, 4 x pair of binding posts
