the Monitor 3
by Andrea Ciuffoli - last update October 16, 2011

To get more information contact me at:
webmaster@audiodesignguide.com

INTRODUCTION

This project born to create a reference monitor loudspeakers to test my new amplifiers without a budget limit.
It is obvious that 3 are the min number of ways to create a true full range loudspeakers so in the future
this system will be integrated with an active MFB subwoofer to get the lower frequency band (20-50Hz).
The midrange driver is responsible of the main frequency range so it should have the max quality possible.
I have used probably the best mid-woofer on the market. It is a 18cm to get a good low frequency band
also without a subwoofer and to keep always a high crossover frequency with the tweeter.
The quality of the high frequency band in the Monitor 2 has been increased using the best Morel tweeter.

 

COMPONENTS >
AudioTechnology Quenze 18 H 52 17 06 SD
 
Resonance frequency - fs: 40 Hz
Equivalent volume - Vas: 28,5 liter
   
Qms| 1,8
Qes 0,39
Qts 0,32
   
Nominal impedance - Zn 8 Ohm
DC resistance - re: 5,6 Ohm
   
Effective cone area - Sd: 137 cm2
Compliance – Cms: 1,09 mm/N
Mechanical resistance – Rms: 2,04 kg/s
Moving mass – mms: 14,6 g
Inductance 1 KHz – Le: 0,13mH
Force factor – Bl: 7,3 N/A
   
Winding height – Hc: 17 mm
Air gap height – Hg: 6 mm
Nominal power – Pn: 150 W
   
Acceleration factor: 499
Efficiency – SPL: 89 dB
Morel ST1308
 
   
   
Resonant Frequency 680 Hz 10%
Moving Mass Mms 0.44 g
Sensitivity 2.83V/1M 91.5dB SPL
Transient Power 10m 1000W
Nominal Power Handling (DIN) 220W/12dB
Overall Dimensions DxH 130 mm (5.12") x 40mm (1.57"
 
 

 

Jantzen Audio Superior Z-cap

Jantzen Audio Z - Superior Caps are high-end components,
delivering a natural, almost holographic soundstage.
I have tested these and compare with my references Solen MKP and
Clarity Cap SA range caps.

In the article of Tony Gee these get a verdict of 10.
www.humblehomemadehifi.com
 

 

Jantzen Air Coils

To get the lower distortion it is necessary use only air coils inductance with a good wire section.

 ENCLOSURE

To create a hi-end loudspeakers it is necessary build an enclosure without compromise and only a person with lot of experience in this filed can create a true good enclosure.

For this purpose I have used www.officinelettroniche.it of Ivan De Cesaris. 

The loudspeakers on the custom stand created by Stand Audio Artigianali on my specification:

In this project I have used the most expensive components available in the market so also for the stand was necessary a product without compromises and with an extreme consistence.
Looking on Internet I have found this good italian craftsman with a lot of experience in loudspeakers stands.
He can create any kind of stand on your specification and the price is very competitive, half cost of the commercial product because you buy directly from the builder.
I like 3 spike instead of 4 to avoid long time in the regulation so this base can be used with 4 and 3 spikes.
Note the special finish of these stands with very precise welds.

The columns of these stands has been filled using fine sand for aquariums, 5Kg for  each stand.

 

 

Bass Reflex Tube HP 50, Speaker terminals VSC 110BW and 2 sheet of MFD (Moulded Foam Dampening)  from Audiokit

CROSSOVER DESIGN

I have used in all the measurements the Clio system by Audiomatica with the Transit by M-Audio to use the USB port of my portable pc (instead of the PCI audio board).

After many test my choice is a constant impedance filter to match any vacuum tube and solid state amplifiers without feedback with low damping factor.

The crossover have a separated box for each channel.

Follows the near field frequency band of the Audiotechnology  to check the bass reflex frequency.

 

OLD CROSSOVER DESIGN

Follows the frequency response of both the drivers without the filter at 1Meter on MLS impulse with a sampling of 48KHz and a size of 4K on my laboratory room, it should be considered from 500Hz to 20KHz

This first design is inspired to the Humble Homemade Hifi design of The Monitor.

Also if is more flat with 10uF + 4.7uF on listen test my friends prefer the filter only 10uF.

The second design is a normal 12-18dB/octave very flat.

The my friends don't like very much this filter probably too flat on medium-high frequency.

 

This new design is a normal 12-18dB/octave with a low  decay on high frequency.

new design in August

The 6.9uF has been created with 4.7uF and 2.2uF in parallel.

The two resistors are
Jantzen Audio.

Filter of August 2011, frequency response at 1.5m