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History : the Mylo case..

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A bit of history..

In the past MTZ Audio had the opportunity to gain a first-hand experience on Audax driver units. Three speaker projects, sold as DIY kits, were designed and implemented with the famous aluminium dome TW025A20 tweeter driver and the HM170Z18, HM210Z12 woofer units.

tw025a20v.jpg (25227 bytes)

copyright © AUDAX, www.audax.fr

Many greek DIYers constructed these speakers. Their satisfaction was more than rewarding for the people of MTZ Audio. Since September 2004 Audax has stopped OEM driver sales.

 

The Mylo speaker project..

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

 

Selection of drivers..

The initial idea behind Mylo was to address the acoustic environment of a relatively small listening room. Although there are a lot of opinions on the room area a speaker can 'load' effectively, MTZ Audio people have come to the conclusion that the optimum room area a pair of 6.5'' woofer cones can drive in the low frequency range, is about 9-15 m2.

Another initial intention was to make Mylo achieve sonic perfection in the mid-frequency range where male and female voices as well as wind and string instruments operate.

At that time (late 2003) MTZ Audio staff decided to select the popular aerogel cones of Audax drivers for these difficult tasks. Mylo was designed after the 6'' HM170Z18 driver.

The aerogel cone material made Audax drivers famous for their naturalness, openness and transparency in the mid-frequencies.

Many things are subjective in audio; in that sense MTZ Audio people found aerogel drivers much better than many popular and unexpectedly expensive kevlar- or carbon-fibre drivers manufactured by other well-respected brands.

 

copyright © AUDAX, www.audax.fr

 

The enclosure design..

An old audio proverb says : 'loudspeaker enclosures are difficult to design and hard to construct'. We wouldn't agree more !

Many speaker designers tend to choose increased volumes even for small 6.5'' woofers in order to achieve an extended low frequency response (i.e. a very low cutoff frequency). In this way power handling capacity of the speaker-under-design is severely compromised.

Mylo was given a 24lt net volume. The reflex-port was tuned at 44Hz and the resulting  cutoff frequency (-3dB) was measured at 39-40 Hz.

The enclosure material selected, was a high-density 22mm thick MDF.

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

Driver and cabinet data were input to our simulation software (LFA v5.0) to derive the optimum driver and port positions over the baffle board. Vent emissions were kept to a minimum outside the tuning frequency as illustrated in the following picture:

 

lfa_screen_shot_1.jpg (119731 bytes)

 

Thus Mylo was enhanced with an exceptional sonic purity in the frequency range 120-800 Hz where enclosure standing waves and vent resonances dominate the vast majority of other speaker designs.

A near field SPL measurement in the port's mouth verified LFA prediction with an very good accuracy:

MYLO#1_vent_near_field_SPLs.jpg (73910 bytes)

 

The crossover network..

We at MTZ Audio, believe that crossover networks are intended to manipulate, compensate and align driver responses, not just decorate the interior of a speaker's cabinet. We certainly do not promote minimalism in this area of electronics. Although we respect other design approaches, we definitely do not encourage the excitement of driver's nonlinearities and cone break-up waves that many DIY designers induce through their oversimplified crossover network topologies.

The idea is simple : Intermodulation distortion artifacts never appear in SPL measurements. Crossover networks are not merely 'frequency dividing' circuits. It takes more than a desired SPL curve to really design a speaker system.

MYLO#1vs#2_SPLcor_s.jpg (104725 bytes)

The picture above depicts the anechoic SPL response of a Mylo speaker on tweeter axis, at a distance of 1m, for 2.83Vrms input (Valid measurement frequency range 200Hz-48kHz). No smoothing is applied to this measurement.

Obviously the upper cutoff (-3dB) frequency of Mylo is approx. 30kHz !

The small 'valley' in the 1-7kHz range compensates for early reflections in typical living room environment and enables really loud listening sessions. People that own Mylo are really proud of it !

The exceptional similarity of Mylo speakers SPL response is due to the very low production tolerances of Audax drivers and our careful selection of crossover components.

A hardwired sample crossover network is shown in the following picture:

 

A detailed circuit schematic follows right below:

 

A few words on impedance..

MTZ Audio staff has got an extensive experience on amplifier design hence regards the nature of a speaker's complex impedance very critical for amplifier feedback operation. We all know that amplifier specs are measured across laboratory resistive loads of 4 or 8 Ohms. IEC 268 standard was never revised despite the strong criticism by many researchers and designers involved in the amplification case.

A special impedance correction circuit was engaged in parallel to Mylo's crossover network, to render the latter's impedance as resistive as possible in a wide frequency range. This sub-circuit is shown within the crossover network schematic just above. Its 'healing' properties can easily be understood in the following impedance graph:

In a very wide frequency range (100Hz to 30kHz) a nearly flat impedance for the Mylo speaker was achieved.

At lower frequencies where large impedance resonant peaks occur to absolutely all loudspeaker systems (up to 40 or more Ohms !) such correction circuits demand extremely large inductance and capacitance values and therefore are not feasible. Mylo's impedance correction circuit is surely a decisive step towards sonic perfection, especially for those who do not own highly expensive amplifiers.

 

The assembly procedure..

Sometimes small details make the difference.

Sealing any removable cabinet walls, securing the driver screws with special clips..

354_Img_3988sv.jpg (98134 bytes)

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

..using vibration dampeners and placing high quality absorption lining,

356_Img_3991sv.jpg (46632 bytes)

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

..making robust welding joints on the driver terminals..

357_Img_3992sv.jpg (67574 bytes)

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

..are some of Mylo's small secrets.

358_Img_3994sv.jpg (134080 bytes)

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

..and perhaps of its popularity among DIY enthousiasts.

P8280034s.jpg (124309 bytes)

picture courtesy of an MTZ Audio friend who owns a Mylo pair.

 

Some useful links (in Greek) in AVforum's discussions concerning the Mylo project:

http://www.avforum.gr/showarticles.php3?topic=11&subtopic=16350

 

 


Mylo / Technical Specifications

two-way, two-drivers' design,

vented-box low frequency alignment, port tuned at 44Hz,

high freq. driver: TW025A20, alum. 1'' dome by Audax,

bass-mid driver: HM170Z18, aerogel 6.5'' cone by Audax,

enclosure volume: 24lt net,

speaker ext.dimensions in mm: 244x524x294 (WxHxD),

SPL response cutoff frequencies (-3dB): 39Hz-30kHz,

sensitivity: 85dB SPL / 1m / 2.83Vrms input (anechoic),

power handling capacity: 100W rms per amplification channel,

impedance: 8 Ohms,

crossover frequency 2.5 kHz.

 


Drawings and Assembly Instructions..

Hint : images below, link to downloadable pdf files.

Mylo_Final_Assy_Y12-324_00-005vA_page2s.jpg (50144 bytes)

Mylo_Final_Assy_Y12-324_00-005vA_page3s.jpg (61282 bytes)

 

Copyright © 2005-2007, MTZ AudioTM , website v.7.1, last update : January 27th, 2007

PLEASE READ CAREFULLY THIS DISCLAIMER : MTZ Audio staff do their best to ensure that all material -technical or not- presented in this website is accurate and correct; however MTZ Audio holds no responsibility for this. In a similar manner, should anyone claim to have been harmed directly or indirectly by the use of technical information presented in this website, MTZ Audio will not be liable for such claims.