Audio Database

S7500
Commentary

Project K2 speaker system using the same module as S9500.

The S7500 uses three modules that are used in S9500 : Base Module B95, Low Range Module 3000M, and High Range Module 4500M. In addition, a 75M top plate is used to increase the coupling between each module.

Each module is connected at a pin point by a pin disk centering system using four pairs of metal pin disks and a point base. In particular, the 4500M module is firmly connected to four pin disks on the top and bottom of the module and the point base by a stainless steel rod passing through the module.


3000M Module

The 3000M consists of a 1400 nd woofer unit and an enclosure.


It is equipped with 1400 nd which is 36 cm cone type woofer in the low range.
Since this unit was developed on the assumption that it can be used as a pair with 475 nd, it is designed with a 14-inch aperture that is well connected with 475 nd in terms of playback bandwidth.
A neodymium magnet is used in the magnetic circuit. With the conventional method, it was difficult to use a neodymium magnet in a woofer, whose magnetic force rapidly decreases when the temperature exceeds the 140 degrees. However, this problem was solved by adopting a unique bent gap cooling method. In this method, three through-holes are provided from the gap part to the rear part of the unit, and the voice coil is forcibly cooled by passing an air flow using the reciprocating motion of the woofer cone itself. Due to the structure of this method, the flow volume of cooling air automatically increases when there is a large amplitude that generates a large amount of heat.
By strengthening the magnetic circuit, we have achieved a top plate width of 25.4 mm in the gap, and by adopting a short voice coil with edgewise winding of a highly flat aluminum ribbon wire, we have achieved quick response speed and large linear motion of the diaphragm.


The enclosure is a ported duct and bass reflex system with an internal volume of approximately 57 liters. The duct is a fold-type pipe duct. The shape is a modified 8-prism designed to match the high-pass module 4500M. In addition to increasing the strength, it also has the advantage of preventing internal standing waves.
The enclosure is made of MDF for the baffle board, high-density particleboards for the other parts, and hard rubber molded sub-baffles for the front unit mounting.

Monster cable is used for internal wiring.

The terminal boards on the back of the 3000M module contains a High Frequency Trim switch and a High Frequency Contour switch.
With the HF trim switch, you can increase or decrease the level of sound above 650 Hz by 1 dB. This control is not a ramp, but a step-by-step control over the range from mid to high.
The HF contour switch can attenuate high frequencies above 5 kHz.


4500M Module

The 4500M consists of a 475 nd driver unit and horn.


The 475 nd is a unit refined for home use based on the professional unit 2450J which uses neodymium magnet and pure titanium diaphragm. The magnetic circuit of the 475 nd has been changed from the external magnetic type used in 2450J to the internal magnetic type. The diaphragm has been changed from the ribbed type to the flat dome diaphragm coated with Aqua Plus in consideration of sound quality. The diaphragm diameter is 4 inches (10 cm) and the diamond edge suspension ensures linear operation.
It also employs a compression driver design with a traditional inverted dome diaphragm layout and a soundpath configuration that connects to a 2-inch (5 cm) diameter throat via a unique equalizer called a coherent wave phase plug.


The horn is a biradial horn with a 2-inch (5 cm) throat and has a cutoff frequency of approximately 500 Hz with a radiation pattern of 60 degrees horizontally and 40 degrees vertically.
The upper and lower parts of the main body of the horn are machined from a solid transparent acrylic block and finished into a large horn with excellent rigidity. The side plate is made of MDF and treated with a mirror-finished anodized aluminum plate.
The throat part is made of cast aluminum, and the complicated shape is precisely finished by cutting processing.


B95 base module

B95 is a pedestal made of molded color concrete, and the weight of the single unit is about 45 kg.

The base module is equipped with four point bases, which are designed to be height-adjustable to allow the system to be horizontal.


Other

The input terminals to the system are located on the rear of the 3000M module.

The crossover network contains both high pass and low pass channels within the 3000M, so the connection to the 475 nd used by the 4500M is via 3000M.

In addition to the normal connection, the power amplifier can be connected by a bi-wiring method.
A multi-amplifier system using an electronic crossover is also possible, in which a bypass switch is provided in each low-frequency module so that the built-in network can be disconnected.

The exterior finish comes in four color variations : black, gray, gunmetallic, and white washed maple.

Model Rating
Method 2-Way, 2-Speaker, Bass Reflex System, Floor Type
Units, etc. For Low Band : 36 cm Cone Type (1400 nd)
For High Frequency : Horn Type (475 nd)
Frequency characteristic 35 Hz to 21 kHz -6dB
Output sound pressure level 91dB/2.83V/m
Nominal input impedance 6 Ω
Maximum allowable input 300W(I.E.C Shaped noise)
Crossover frequency 650Hz(-12dB/oct)
External dimensions Width 590x Height 940x Depth 500 mm
Weight 124kg
<Specifications of 475 nd>
Diaphragm aperture 102mm(4inch)
Impedance 16 Ω
Frequency characteristic 500 Hz to 21 kHz
Output sound pressure level 107dB/2.83V/m (With Horn)
<N1400Nd Specifications>
Aperture 355mm(14inch)
fo 25Hz
Frequency characteristic 20 Hz to 2 kHz
Output sound pressure level 92dB/2.83V/m