Alpair 10.2 in 8 liter sealed - Too good to be true? - Page 6 - diyAudio
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Old 11th October 2012, 07:46 PM   #51
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Don't know about spheres with Mark Audio Drivers, one guy in Germany says that Alpair 7 does not functions in sphere, why- he couldn't explain...
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Old 8th June 2013, 02:26 PM   #52
rongon is offline rongon  United States
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Well, it's time for Zombie Thread Return From The Dead.

I *finally* (!!) cut the holes for mounting my (now not so new) Alpair 10.2's in 8 liter cabs (salvaged from an ancient pair of B&W DM100). I lost patience and cut the baffle holes with a jig saw, using a blade for cutting curves. It ain't pretty like you other guys do it, but it seems to have worked. I'm in the break-in phase now. They've been playing the radio at a low volume for about 48 hours now. The sound keeps changing. It's crazy. When they were fresh out of the box, they sounded thin, no bass, honky mids. The next morning the highs began to come out. That afternoon they started to make a little bass. Last night they sounded fuzzy, but this morning they've cleared up. I can't wait for 100 hours to be over so I can play them in the main system at a moderate listening level.

Right now, it sounds like they might need some BSC. The mids are still too prominent. It could be my lousy cabinet work, or it could be a break in thing. I guess I won't know until I play them at moderate volume. The whole idea behind this model is that they should not need any BSC network, correct?

I have high hopes for these.

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Old 8th June 2013, 06:20 PM   #53
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Let me first say, I don,t know much about the inner workings of speakers I leave this to my son who has convinced me to build a few boxes. What I do know is furniture & cabinets, so my love for mdf or marine ply is very limited. Building a 6 sided solid wood box has many issues mainly the constant stress on the cross grain glue joints. In my neck of the woods that means that a typical 12” wide red oak plank or panel (for example) will move upwards of 5/16” as our average humidy changes from 6%-12% seasonally. My solution is to build top,bottom and sides of solid and use a sub strait for front and back.I hand cut my own veneer so what ever looks good I can use,the solid carcass on mine will be shedua. We just completed my sons alpair7 s , using one of the plans on marks sight.
Well its time for my pair, over the last number of years (to many to count) most of my listening comes from live music, artists from fusion jazz such as spyro gyra to Dave M &Tim R to Clapton unplugged to note a few. For the last number of years I have been using my “bought new in 1978 “AU417 sansui amp and a pair of energy rc-30 speakers. That amp now needs repair and I have a small 30watt topping chip amp, not quite big enough for its home in the large 600sq space. So with a sound card upgrade to the computer and a new 50ish watt amp I am thinking of buying the alpair10 or even 12s.
I am trying to get away from the cabinet grade look of a typical speaker(no offence intended) and incorporate them into more fine furniture grade stands, I guess you call it a pencil type box but a 36”to 38” tall box would be more appropriate to the design. So any input to speaker choice or cabinet dimensions would be appreciated .
Paul Burchell Woodworking
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Old 8th June 2013, 07:07 PM   #54
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correction: i meant to say 27" to 30" tall cabinet
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Old 8th June 2013, 08:01 PM   #55
cotdt is offline cotdt  United States
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I measure a flat response when there is an 18" inch distance between the front of the speakers and the wall. Some moderate wall loading might be needed for flat response.
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Old 8th June 2013, 08:18 PM   #56
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Quote:
Originally Posted by rongon View Post
I *finally* (!!) cut the holes for mounting my (now not so new) Alpair 10.2's in 8 liter cabs (salvaged from an ancient pair of B&W DM100).
The dims I found would suggest the boxes are closer to 14 liters.

Quote:
Originally Posted by rongon View Post
Right now, it sounds like they might need some BSC. The mids are still too prominent. It could be my lousy cabinet work, or it could be a break in thing. I guess I won't know until I play them at moderate volume. The whole idea behind this model is that they should not need any BSC network, correct?
The boxes are sealed right? You won't get the same bass extension as a vented box.

jeff
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Old 8th June 2013, 09:10 PM   #57
rongon is offline rongon  United States
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Quote:
Originally Posted by vinylkid58 View Post
The dims I found would suggest the boxes are closer to 14 liters.

The boxes are sealed right? You won't get the same bass extension as a vented box.

jeff

Well, I guess I goofed there. I measured 37cm x 22cm x 21cm external dimensions. Subtract 3cm from each dimension for cabinet wall thickness and I get 34 x 19 x 18 = 11.63 liters.

Oops!


Looks like I'd do much better with a 1.5" inside diameter vent, 5" long.

F3 for the 12L sealed box = 73Hz
F3 for the 12L vented box = 51Hz

Does that look about right?

Last edited by rongon; 8th June 2013 at 09:13 PM.
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Old 8th June 2013, 09:31 PM   #58
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Originally Posted by rongon View Post
Looks like I'd do much better with a 1.5" inside diameter vent, 5" long.
Sim shows a bit of a hump centered around 90Hz, so you could go a little longer if this is an issue. 7" long vent would flatten things out nicely if it fits in the box.

jeff
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Old 8th June 2013, 09:57 PM   #59
rongon is offline rongon  United States
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Hmm, that could be a problem. The box is just over 7.25" deep, internally.

What frequency did you tune the box to? About 37Hz?

I'm using WinISD, so it's probably not as accurate as what you're using.

Come to think of it, a bit of a bump around 90Hz wouldn't be such a horrible thing if I don't try to use them with subwoofers.

Last edited by rongon; 8th June 2013 at 10:04 PM.
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Old 8th June 2013, 11:50 PM   #60
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I'm just using WinISD 0.50a7. I allowed 1/2 liter for the driver motor etc., so 11.13 liters @ 38.6Hz. A 6" vent would be 41.2Hz, maybe try that. Don't forget it's just a simulation, so you'll need to experiment if it doesn't sound right to you.

jeff
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