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Old 9th October 2009, 07:36 AM   #1
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Default Mark's new Alpair 12

Hi Guys,
Here's the information on my new Alpair 12. Sorry it's taken longer than originally planned but I believe the extra time spent on optimising this driver was well spent.

To my knowledge, the Alpair 12 is the only single cone/cap driver of its size (206-mm or 8") that can reasonably claim to be full range. The Alpair 12 passes 20-kHz at +87dB. Granted there are other similar size drivers that have may the range but they have to employ a co-axial or whizzer to emit the upper frequencies. However, getting a large diameter single design to go this high is unusual.

The main reason why I spent so much time on this design centres around the stability of the cone. The grade of the mixed alloy, the cone and profile and the use of my Multiform process process all came together. Certainly, I couldn't have made this driver to go full range without the Multiform process. The old spinning method is not accurate for this cone size and thickness.

The other point of particular interest will be the spider. I worked with an very interesting fellow by the name of Tadashi Matsubara San. For those who don't know him, Tadashi was one of the lead Fostex designers for some 15 years. The suspensions are therefore interesting and unique in terms of their linear compliance envelope, size, grade and profile to the Alpair 12 and the Alpair 7. I'd like to take this opportunity to thank Tadashi for his efforts.

It's time to thank Evan Yu, my right-hand man. It wouldn't have been possible to make these drivers with his fantastic help. Golden Xu and Yifan who are excellent sample makers, Rebacca and Will on cones and Lui Yi Ping (better known as Jack!), the ultimate front suspension man, Mr C and Jojoe on frames, great mould makers. All these people and more have made it possible to bring the dream of extended frequency range a step closer. And my thanks to many others who've all contributed. This includes members of this forum - thanks fellas for your encouragement, advice and support in these challenging times.

It takes more than one man to make a good driver, I'm happy to share the credit.

So here goes...........

1 - New standard hole M4 metric hole size. The Alpair 12 comes
supplied with high quality Hex drive black powder coated wood screws
and a 2-mm PVA cabinet seal for easy installation.

2 - The frame is 100% custom made. Like other Alpair series drivers,
the Alpair 12 frame is designed to reduce resonance that could be
transmitted to the cabinet. This Alpair also comes with a trim cover
to improve both fit and finish.

3 - The front suspension is a new advanced moulded design, made only
for this driver. The mass of the piston section has been reduced. It's
ultra-thin compared to other drivers. To cope with the new design
demand, the mould was machined to a +/- 5 micron tolerance. This is
critical to maintain the accuracy of the ultra-thin piston wall.

4 - Alpair 12 has an all-new Multiform cone. The low mass, mixed alloy
material is very thin, less than 0.11-mm on the critical sections
along its profile. Much research went into the profile design to take
advantage of the Multiform cone manufacturing process. To our
knowledge, the Alpair 12 is the only current production driver of
single cone, single cap 8" design, capable of reaching 20-kHz at 87dB.

5 - The cap is now directly bonded to the coil former using a A/B
bonding method. This arrangement is very strong. It is a very
efficient method for the transmission of middle and high frequency
responses.

6 - The spider is a custom design. Its profile and the suspension
shapes are specific to this driver. This spider makes a significant
contribution to the fast response of the Alpair 12.

7 - The custom construction of the Alpair 12 is significant. An all
new connector system has been design to make installation easy. Each
connector is colour coded. The system also is also designed to
optimise the damping of the leads that run to the coil.

Alpair 12 parameters
Revc= 7.000 Ohm
Fo= 46 Hz
Sd= 143.14 Cm
Vas= 22 Ltr
Cms= 0.750 M/N
Mmd= 14.886 g
Mms= 15.871 g
BL= 8.752 T.M
Qms= 1.454
Qes= 0.420
Qts= 0.327
Levc= 0.058m H
No= 0.493 %
SPLo= 89.3 dB
X Max= 12mm
Pwr cont= 50 watts

Cheers,

Mark
Attached Images
File Type: jpg Alpair12_img1_detail.jpg (76.6 KB, 3298 views)
File Type: jpg Alpair12_img1_sml-1.jpg (41.9 KB, 3085 views)

Last edited by markaudio; 9th October 2009 at 07:49 AM.
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Old 9th October 2009, 07:39 AM   #2
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Fellas,
Here's the graphs and installation.
A quick reminder, the drivers come with a set of M4 X hex wood screws and a 2-mm seal.
Cheers,
Mark.
Attached Images
File Type: jpg Alp12_fr2.jpg (92.4 KB, 3092 views)
File Type: jpg Alp12_imp1.jpg (112.6 KB, 2978 views)
File Type: jpg Alp12_Dia_sml.jpg (24.3 KB, 2869 views)
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Old 9th October 2009, 07:57 AM   #3
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A 'proper' driver. Love the spec. on it; it's ideal for modest sized BRs etc., for those needing something easy to build, & fine for MLTLs & more complex box types too. Take a look at that cone profile... fantastic bit of work. I like the FR balance that's been engineered into it too; it's going to make it a very natural sounding / forgiving speaker & it gets up remarkably high. Suits me. Looking forward to hearing them.
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Old 9th October 2009, 10:26 AM   #4
alspe is offline alspe  Finland
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There is quite much BSC. Can designer reveal does this work fine in BR enclosure? How close to back wall?

20 l @ 42 hz tuning front ported ?
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Old 9th October 2009, 10:36 AM   #5
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Another winner from M.A.?

Quote:
Levc= 0.058mH
You have a knack for crazy low inductances in driver sizes normally hitting near a mH.

This makes series XO design very simple. Appreciated

Cheers!
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Old 9th October 2009, 11:02 AM   #6
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That's one of the reasons MA drivers have such a wide BW.

They should work v. well in a BR; plenty of possible alignment options.
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Old 9th October 2009, 01:30 PM   #7
Jozua is offline Jozua  South Africa
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Mark

How does it sound and what is the cost?

Jozua
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Old 9th October 2009, 05:21 PM   #8
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Old 9th October 2009, 06:01 PM   #9
tinitus is offline tinitus  Europe
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Looks good
Maybe the long wanted 8" candidate fore a 2way

But why is there no standards of how to spec Xmax, one way or p-p ?

I mean, a calculation or sim use one way Xmax, right ?

Last edited by tinitus; 9th October 2009 at 06:13 PM.
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Old 10th October 2009, 06:05 AM   #10
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Hi guys,

Alpse, Most BR designs tend to be narrow, saving space. Once the driver's in the cabinet, the LF with flatten out. Similarly in TL and some horns. For more exotic designs, some filtering may be needed.

Jozua, I think the 12 sounds great, but the final judging is in the future as audio guys use them. Price depends on local dealers. Send me a private communication via this forum, I'll put in touch with a dealer.

Tinitus, Good question. Like so much in this industry, there's no agreed standard.

Cheers,

Mark.
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