Mark's new Alpair 7
Hereís the Alpair 7. In some ways, this might become my favourite driver. Last week, Norio San and me sat down to road test a pair of these in 7.25 litre BR pine-wood boxes, nothing fancy. Powered by a Accuphase E307, source was a Denon S10 CD player, no filters, no cross, just these units, we were blown over by the detail and sheer quality of the reproduction. I wonít say any more because its the future users that will be the final judges. All the same, I was more than pleased with my alchemy and there was a huge smile on Norioís face.
The primary objective of this Alpair is to deliver a very wide range, particularly in the HF. If I had a dollar for all the people that told me itís impossible to take a single cone design of this size beyond 20K, Ií be happily retired by now. I was told whizzers and co-axial were the only ways to go. Well, the Alpair 7 delivers 30-kHz without whizzers, co-ax tweets, phase plugs and all the tricks that came along over the years: The Alpair 7 is a single cone, puristís design.
Cone - Japan 4 mix alloy, re-tempered material. For those with knowledge of Japanís long history in metals, youíll know whatís been done to this cone. Lots of time and effort have gone into this cone and cap. This includes the to 7-10 micron finish. The new Multiform process in full use to make this component, couldn't be done any other way due of its tolerance critical requirement.
Cap - Same material as the cone, thickness down to <0.06-mm. Also made by Multiform. DONíT touch it! (or the cone for that matter).
Front Surround - The softest compliance and the thinnest we made so far. Two additional sets of micro-fibre have been blended into sections of the butyl to retain stability. My thanks to Lui Yi Ping for his hard work, and his particular attention to the tooling used to centre to surrounds on to the cones.
Voice coil - The former has been re-manufactured on a machine to line up the formís leading edges prior to winding. The accuracy is tolerance critical on this design.
Spider - My thanks to Tadashi Matsubara San. As already mentioned in the Alpair 12 launch thread, Matsubara sanís contribution to the Alpair 7 rear suspension is significant, this spider uses the same design concept and production tolerances as the Alpair 12.
The rest - by now, most of you know my approach to building drivers. All the components are 100% custom built. This includes the new connector blocks. The frame is custom, its 135-mm in diameter. I put my time in (along with Evan and Yifan) on the production line, also much time spent at the component suppliers getting this driver made. I smashed allot of early components until the guys got it right, then I stopped smashing and started assembling.
Finally, my thanks to many members of DIYaudio. Your advice and suggestions are important. These contributions have influenced the build and performance of these latest drivers - many thanks to you all.
Alpair 7 Data:
T/S = Alpair 7 MP
Revc= 3.600 Ohm
Fo= 69.0 Hz
Sd= 50.24 cm≤
Vas= 3.48 Ltr
Cms= 913.149u M/N
Mmd= 5.456 g
Mms= 5.660 g
BL= 3.342 T∑M
Levc= 0.0188 mH
No= 0.135 %
SPLo= 84.5 dB
Xmax= 4.4-mm 1 way
Pwr= 20 Watts Nom.
Looks like a candidate for one of Planet10's FAST designs :)
Hi Mark, congratulations on another beautiful driver. I came across some A7 tests on this blog the other day, before you posted this release:
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Has the driver been out for a little while in Asia, or was this a pre-production sample?
Normally I don't care about looks, but these are so cute, I could buy just to look at them!!
Hi Henry, Geek and Peter
Thanks, glad you like the look. I'm trying to help DIYer's gain a "pro" look to projects. There's a front cover that fits over the frame. It's bonded to the frame but could be supplied separate in the future. This would allow users to customise the look (painted cover etc.)
Yes, this driver (Also new CHR-70) is in Japan right now. Germany next week. The Japan version is slightly different in some minor details. But very minor. Both drivers are already selling well.
Sorry I've not called you, (hectic). I'll catch up and call you to discuss.
Here's a pic of the Alpair 7 in a nice cabinet from the Linfof Japan blog site:
I have just begun to look at some of your drivers for a mini-console luggable project I am working on. They look rather nice (haven't run numbers yet but look doable). One concern I have is durability of the light weight materials in the hands of a teenager. Have you found these driver to be pretty rugged.
My application is 4-8W of SE tube power into the mains (preferably sealed or open back) with crossover to sub at around 70-80Hz. Looking to get SPLs in the mid 90s if possible. Have looked at Fostex (Xmax issues), CSS FS125 and Jordan. Of the three I like the Jordan best even though efficiency is not as high as Fostex. Your drivers seem to be very competitive in this application.
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