Building the

Giussani Research DELTA 4R5

speaker system

(a.k.a. Audiolab DELTA 4.5)

(web page under work)

Introduction

Here will be described my construction of the Audiolab Delta 4.5 speaker system.
The original project is by Renato Giussani. Now owner and managing director of a publishing company (Argò), in the 70' and 80' he became the top italian loudspeaker system designer worldwide recognized.

Delta 4.5 is a top-level quality system with a very original and good looking design. It is an up to date version of the Audiolab Delta 4, one of the first Giussani's designs that still now, after more than 30 years, is considered a very good sounding product.
Delta 4.5 original project is available for free to the DIY community at this link (italian).

The picture below is a rendering done during the project phase.

The total budget to build this system is around 1100-1200 €. This is only to cover parts and materials. I think that a commercial version of this system will cost more than 6000 €, but its sound is worth even a lot more than that!

I tried to follow the original project as cose as possible notably for the electroacoustic part. In these pages is detailed my construction phases and the measurements I have made.

Project

Speaker components

This is a 4-way speaker system.
These are the drivers used in the system.

Woofer

The woofer is the 4 ohm NHT 1259, a 12 inch made by Foster distributed by Madisound.

And these are manufacturer's specifications:

NHT 1259 Specifications
Fs	16.5Hz
Nominal Impedance	4 ohm
Mmd	128.0 Grams
Cms	696.48 m/n
Vas	238.4 Liters
Rscc	3.52 W
Leap Krm	3.277 mW
Leap Kxm	10.063 mH
Leap Erm	0.772
Leap Exm	0.743
vcL	1.06mH @1K
Bl	9.574 Tm
Qms	2.680
Qes	0.533
Qts	0.445
Voice Coil Height	34 mm
Air Gap Height	8 mm
Xmax	13.0 mm Peak
SD	0.0491 m 3
Surround	Rubber
Cone Material	Polypropylene
Magnet	59 oz.
Voice Coil	50 mm
Music Power	300 Watts
Sensitivity	90 dB 2.83V/1m
Price	$150.00

In this page there are some measurement I made on my speakers.

The original woofer is now discontinued. Madisound has a new model MAD1259available. This new model has some differences, but is still suitable for the project. The only modification needed is to fill completely the box with absorbent.

These are the new woofer's parameters:

Specifications
Fs 20.13 Hz
Nominal Impedance 4 ohm
Mmd 104.33 Grams
Cms 565.17 m/n
Vas 195.1 Liters
Re 3.524 ohm
Leap Krm 4.033 m ohm
Leap Kxm 11.829 mH
Leap Erm 0.756
Leap Exm 0.727
vcL 1.09 mH@1K
Bl 8.472 Tm
Qms 4.413
Qes 0.663
Qts 0.576
Voice Coil Height 34 mm
Air Gap Height 8 mm
Xmax 13.0 mm Peak
SD 0.0493 m2
Magnet 59 oz.
Voice Coil 50 mm
Music Power 300 Watts
Sensitivity 89 dB 2.83V/1m

Low-Mid (planar)

The low-mid is a planar component, the Bohlender Graebener's Neo8.

You can find it on Parts-Express catalog code 264-712.
Here is the link to the datasheet.

High-Mid

It is a Scan-Speak: D3806/820000.

Manufacturer's site is www.tymphany.com.

Tweeter

It is another Scan-Speak: D2010/851300.

Manufacturer's site is www.tymphany.com.

Cross-over Filter

This is the final v. 5.2 schematic.

xover v. 5.2

On this page there are some measurements I made on my filters and components.

System enclosure

The cabinet is composed by a prism-shaped closed base for the woofer and an upper panel for the remaining 3 components. Two tall frames covered with fabric hide all the inner parts giving the entire system a monolithic look like an electrostatic system.

This is an exploded view from the original drawing of arch. Massimo Massetti.
esploso

Some details of my box are covered in this page.

The Final Result

This is one of the completed speaker ...

with the original Giussani-Research tag!

Acoustical Measures

Here are some room measures.
The mic was positioned in the listening position 2.8 meters from the speaker and 110 cm from the ground.

The first one is pink noise response 1/3 octave. Single speaker (red right speaker, black left one).

The second picture is still pink noise 1/3 octave but both speaker together.
Note the expanded scale.

Last one is MLS reponse, right speaker only.

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