LOUDSPEAKER COMMON SPECIFICATIONS

LOUDSPEAKER COMMON SPECIFICATIONS
LOUDSPEAKER COMMON SPECIFICATIONS
AND TECHNICAL PARAMETERS
Marshall Choong Audio
General Cabinet Parameters
Unless otherwise stated, all cabinets are of the closed box
type with low Q factors between 0.5 and 0.6 where size
permits.
The controlled resonance of vented enclosures gives rise
to excessive group delay at low frequencies which should
be avoided.
Fig 1. shows a comparison of typical group delays for MC
loudspeakers with 180, 220 and 270 mm drivers having
3dB frequency points at 80, 50 and 40 Hz respectively.
Fig 1.
Overall panel thickness is 30 mm for the smallest 2 way
speakers, increasing for larger units.
Constrained Layer Damping (CLD)
Panel damping is used on all products with a considered
compromise between panel stiffness and damping
effectiveness. A comparison between typical simple
damped panel cabinets and CLD is shown in Fig 2.
Stiff internal panel
Damping layer
Cabinet wall
Cabinet wall
Traditional panel damping
(not to scale)
A
Constrained Layer Damping
B
C
Fig 2.
Impulse test on typical speaker panel materials
A. Untreated beam, amplitude vs time
B. With traditional single layer damping
C. With Constrained Layer Damping
Note the panel vibration without CLD lasts for up to 300 ms.
(c) Marshall Choong Audio 2010
Common Specifications and Technical Parameters
page 1
LOUDSPEAKER COMMON SPECIFICATIONS
AND TECHNICAL PARAMETERS
M a r s Marshall
h a l l C Choong
h o o n gAudio
Audio
Driver Technology
Woofers and mid range drivers in classic monitor and
classic vented models have shorted turn technology
which is important to reduce distortion across the full mid
range.
All tweeters are soft fabric extended surround types with a
rear added chamber in classic products. Upgraded
classic series tweeters have 6 mm solid aluminium front
panels.
A variety of cone materials are used. Coated paper is
commonly used except where a driver is used for woofer
applications in which case aluminium may be specified.
Crossovers
Low order ‘linear phase’ crossovers are used throughout,
similar to the Bessel type.
Loudspeakers in finite cabinets will always exhibit a
shelving effect giving half the bass output at frequencies
typically below 400 Hz. Correction is applied in all MC
products to compensate for this which sometimes leads
to low overall efficiency (85 dBA).
Air cored inductors and substantial polypropylene or poly
carbonate capacitors are specified.
Cabinet Finishes and Veneers
MC uses real veneers on all products with the standard
0.6 mm thickness. A mixture of traditional materials and
glues are used throughout with a view to using
sustainable sources wherever possible.
Other more expensive exotic veneers are available to
special order at extra cost.
Images of current burr veneer options are available on the
website.
Final finishing is based on natural materials such as wood
oils, shellac and wax polishes.
Standard veneers are as follows:
Cherry, American White Oak, walnut and Ash with a black
ebonising process.
Connectors
Most loudspeakers in the range use a gold plated screw
terminal compatible produced in the UK with spade,
wireor banana connectors.
Most loudspeakers in the range are available with
optional Cardas Patented Binding Posts which give the
most secure connection to spades with any connector
system that we have tested.
We recommend the use of soldered banana plugs such
as the Cardas type CBER.
(c) Marshall Choong Audio 2010
Common Specifications and Technical Parameters
page 2
LOUDSPEAKER COMMON SPECIFICATIONS
AND TECHNICAL PARAMETERS
M a r s Marshall
h a l l C Choong
h o o n gAudio
Audio
Sub Woofer Technology
Some loudspeakers in the range have deliberately limited
bass response so that unwanted excitation of room bass
modes is avoided. This is a necessary compromise
between bass bandwidth and uneven bass response
caused by the room. In any case, bass power bandwidth
in small loudspeakers is usually limited by their bass
drivers.
However, the large 3 way monitors and all vented
products are available with an extended bass response
for customers with that particular requirement.
woofers placed in optimum room positions. Good results
are obtained with 2 units placed behind the main
speakers, and even better subjective results are obtained
with 2 further sub woofers on a rear wall set up to cancel
the build up of standing waves within the room. Further
details are available in a document available in the main
website development section. These are not in our
normal product range but if customers show sufficient
interest in these unique products, they can be provided to
special order.
The 2 way vented monitors are recommended for use
with sub woofers.
Marshall Choong advocates the use of multiple sub
Fig 3. Level corrected slow bass sweep, 20 Hz to 160 Hz.
No sub woofers.
Fig 4. Sub woofer system, 1/6th octave bass tone bursts
Fig.20
3. Hz
Standing
Cancellation
tone
tests long
to 100Wave
Hz, each
tone burst
is burst
2 seconds
Fig 3. Slow bass sweeps are more revealing of room effects than , for example,
pink noise sources. This represents the room response with normally placed
speakers and no sub woofer system.
Fig 4. This is the response of the full sub woofer system with 4 sub woofers and
with standing wave cancellation. The tone bursts have good rise and fall times
largely unaffected by the static room modes and the overall response is far
smoother than in Fig 3.
Fig 5. This is the overall in room pink noise response with the same system as in
Fig 4.
Fig 5. System with sub woofers, in room pink
noise response
10 Hz to 20 kHz
(c) Marshall Choong Audio 2010
Common Specifications and Technical Parameters
page 3
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising