Building the

DELTA 4R5 speaker system

(a.k.a. Audiolab DELTA 4.5)

(web page under work)


Here will be described my construction of the Audiolab Delta 4.5 speaker system. 
The original project is by  Renato Giussani a worldwide recognized italian loudspeaker system designer.

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.

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 it sound is worth even a lot more than that!

I tried to follow the original project (no longer freely available) as close as possible. 


Speaker components

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


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

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

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.


It is a Scan-Speak: D3806/820000.


It is another  Scan-Speak: D2010/851300.

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.

The Final Result

This is one of the completed speaker ...

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.


Project © 2004-2005  Renato Giussani; This page © 2005-2006-2013  R. Lorello    
Page last updated onTuesday, 01-Oct-2013 22:54:26 CEST ;  Number of hits:31935

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