Alpair 12 - Damped Air Coupler box design - Page 6 - diyAudio
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Old 11th March 2010, 06:04 PM   #51
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Originally Posted by Scottmoose View Post
Typically you need ~1 1/4in of HDF to ~match the stiffness of 3/4in of a decent grade of birch ply.
FWIW, using the average MOE of 3/4" MDF and 19 mm, 13 lam BB plywood (527 k psi/1.8 m psi) given me by a local G-P rep sometime in last decade, then based on stiffness increasing at the cube of thickness it takes right at 1-1/8" of MDF to match the BB ply's stiffness, though of course being a more massive material to start with it will have even more damping capability at the expense of being 1.5x heavier .

HDF is somewhat harder, but can't locate where its MOE is 'hiding' in my library ATM, though IIRC it equates to between 7/8"-1" Vs BB ply, so still comes up enough short to be an issue.

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Old 11th March 2010, 07:11 PM   #52
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Thanks for the clarification Greg. Most of my MOE data isn't from 'ideal' sources (fudged from data from a bunch of different suppliers), so I've tended to err on the side of caution.
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Old 12th March 2010, 01:46 PM   #53
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Some photo of the construction of box.DSCN1823_fresatura2.jpg


fresatura massellini schienale con sedi per femmine autobloccanti.jpg
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Old 20th March 2010, 03:34 PM   #54
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Add latest photo up to the box completed.
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Old 20th March 2010, 03:54 PM   #55
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Hi Delrik,
Your Pencil 12 boxes look great. Be interesting to see what they look like when finished.

Here's 2 pics of of the Japanese Walnut boxes. Just completed and delivered.

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File Type: jpg Lux_pencil12.jpg (55.1 KB, 1639 views)
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Old 20th March 2010, 06:41 PM   #56
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Mark, these look great!!
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Old 21st March 2010, 03:20 AM   #57
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Thanks Coleman, glad you like the Pencil 12's

Hi Guys,
We've have another pair of Pencil 12's on their way from Osaka. This time the wood is Japanese White Birch. Should be very interesting to see how they sound.

The Walnut cabs are now in John's place on the south side of HK Island. The room is quite large By HK standards, estimated at 5 metres deep and 8 metres wide. The Pencil's easily cope with this volume. The bass is particularly rich and tonally clear, surprising given the room size while mids and highs are accurate, clean and detailed. The Lux's are very complementary to the Alpair's. It illustrates the importance of time spent to match components. John, Graham and me listened to the same amp and CD player combination in the Lux showroom. They powered a very well known British brand speaker system. These speakers weren't complementary to Ito Ema's rendition of the Bach's Golberg Variations. Canone All Unisono (3rd Variation) was all but "destroyed", to the point where I burst out laughing. The first bars of the 3rd variation were best described as "plink-plonk". My apologies to Ito, she's an excellent pianist since this same recording played with the Lux's and Pencils in John's placed was totally transformed. The "plink and the "plonk" was replaced with caressed strikes of the keyboard. Her recital became balanced, far more accurately reflecting the actual nature of this 1994 musical event.

It goes to show the extent of negative effects that some multi-way systems with crossovers can have on recordings. Upon comparison, it's clear that the crossover wasn't properly sorted, or the tweeter's performance was suspect, or both. The Brit system was simply not up to the task. As a bloke with British blood in my veins, my laughter was replaced by sad reflection; To think that a robust UK brand could ditch acoustic performance to solely favour the bank balance.

I'm familiar with the Golbergs from the live concert perspective. I'm more than glad to hear these Pencils (along with the Lux's) maintaining the musical accuracy of this recital.



John's system consist of:
Amp - Luxman L 590A-11, 30 watt class A:

CD - Luxman D-06

Speakers - Alpair 12 in Pencil 12 Japanese Walnut cabinets.

Cables and connectors.
Speaker cables - Tara Labs Copper with WBT Copper connectors.
CD to Amp - Audio-Quest Copper Black Diamond.

Reference CD:
MA Recordings of Japan: Bach's Golderg Variations
Digital Recording, February 1994
Pianist: Ito Ema
Piano: Steinway Model D - 114571
The Harmony Hall, Matsumoto, Japan
Microphones:Tone Craft 2013 with titanium capsules (1 X pair). Custom line circuitry by Junichi Yonetani San.
Cables:Cardas DCS 900B
D/A Convertor: Nakamichi 1000P. DAT Transport: Nakamichi 1000
Digital Audio Tape: KOA
Balance Engineer: Todd Garfinkle
Director: Takashi Sakurai San
Edited and Mastered: Yukio Kojima
3 format recording:
CD/MO24A: Digital via Tone Craft 2013 (pair) - Omi directional - Yonetani
LP/MO24AV: 180gm pressing of 1/2" analogue tape recording. B&K 4006 (pair)
DAT: 20-bit 48kHz digital recording, B&K 4006 (pair)

Last edited by markaudio; 21st March 2010 at 03:34 AM. Reason: typo mending
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Old 22nd March 2010, 10:39 AM   #58
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Are those dovetail joints on the walnut cabinet? It looks beautiful.
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Old 22nd March 2010, 02:44 PM   #59
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Originally Posted by matt kite View Post
Are those dovetail joints on the walnut cabinet? It looks beautiful.
Hi Matt,
Yes, they are all dovetails. Beautifully made in Osaka, Japan.


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Old 27th March 2010, 03:21 AM   #60
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I have become convinced that these Alpair 12's are the driver's that I will be using for an upcoming project. Some readers here may be aware that I am planning a Clairtone Project G "recreation". It uses 18" diameter globe speakers mounted on either side.

I am looking to figure out an enclosure for these drivers. I'll probably have to make a few boxes/globes to get it right, and I'll probably make a set of Pencil 12s to use for reference. Those walnut boxes look nice, I might build those!

I'd greatly appreciate any advice. Dave from Planet 10 has already made some suggestions, and it is upon his advice that i consider Alpair drivers.
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