Alpair 10 vs Alpair 7 - Open baffle with boxed woofer. Passive Xover. - Page 3 - diyAudio
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Old 30th August 2012, 12:50 AM   #21
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Gotta find the time to get mine out of the boxes
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Old 30th August 2012, 12:57 AM   #22
TiMBoZ is offline TiMBoZ  Australia
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Originally Posted by Monte Verdi View Post
From my experience 22" wide is minimum too avoid mid band suckout. We have built numerous prototypes and found that wings and or wide baffle is the most suitable solution.

Ramon
Thanks Monte,

Can you be more specific with regard to 'mid band suck out'? Wouldn't the woofer(s) in a box operating up to 400Hz and then rolling off @ 6db fill in the 'suck out'?

Wings at the side of driver ( U frame) are possible. But again if they go too far back/sides it starts to defeat the purpose of 'open' to some extent.

Do you have any advise SPECIFIC to this thread topic?

Thanks Monte
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Old 30th August 2012, 04:10 AM   #23
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Originally Posted by TiMBoZ View Post
Thanks Monte,

Can you be more specific with regard to 'mid band suck out'? Wouldn't the woofer(s) in a box operating up to 400Hz and then rolling off @ 6db fill in the 'suck out'?

Wings at the side of driver ( U frame) are possible. But again if they go too far back/sides it starts to defeat the purpose of 'open' to some extent.

Do you have any advise SPECIFIC to this thread topic?

Thanks Monte
Frankly, why do you want too cross a Full Range Driver@ 400? You could'nt have picked a more crucial area IMO. As far as the math goes I believe Martin King may have addressed this, though I may be wrong. You can easily check yourself by taping cardboard too sides extending width and hear for yourself. I suggest a prototype made from cheap ply before final in fine wood.

Ramon
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Old 30th August 2012, 11:30 PM   #24
TiMBoZ is offline TiMBoZ  Australia
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Thanks! That's a great idea Monte re; plywood prototype for baffle, U sides etc. I have plenty of spare 12mm plywood.

The idea of using the Alpair 10 means 'theoretically' I can use 6db (re: simple) XO's. It's a very versatile driver. The Alpair-10 is great. The Alpair-7 may be even better between 400 - 20k. But there are probably trade offs either way between the two. But, their power handling is limited. This is to be expected from very low mass drivers.

By XO at 400Hz, theoretically increase power handling. By relieving the driver of having to pat it's head (make mids/highs) and rub it's tummy (make lows) at the same. With 'full range' theoretically I can go from 400 - 20,000 that's still pretty good.

An 8gram 25mm voice coil/cone can't articulate bass like a 75mm voice coil can. Conversely, a 16gram/cone 75mm voice coil can't articulate mids/upper mids and low treble like a 25mm voice coil can. The 'pro' of full range is no XO's but the con is compromises with the driver's ability to articulate the waveform 20 - 20Khz. They are basically a glorified midrange. Hence the idea, use 6db XO to a helper woofer on the bottom and helper tweeter at top. Now, a lower XO of 150-200Hz is better on paper. Agreed. But then you start talking much bigger inductor values. Rather than a 2 mH for 400Hz, we're now talking about >4.7mH for 200Hz. Not extreme, but just this difference really does start to increase to 'focus/emphasise' the output/balance of sound coming from the woofer. At 400Hz (smaller inductor), the mix/balance between the (Morel) woofer and Alpair-10 is much better. More balanced/natural. XO at 200Hz, the mix/balance is like your listening to the rest of the band, from perspective of the bass player. The power handling is less. You don't want to be adding resistors everywhere trying to correct these imbalances. So XO at 400Hz has practical benefits.

I have practical considerations: I'm trying to keep the baffle width/size as agreeable as possible. My wife won't let me put a really great sounding, but door sized speaker in middle of the lounge room. I need to create something 'presentable', child friendly. I can't have something that looks like a science experiment with inductors, caps, alligator clips etc. lying around permanently. Hubby's generally cool with it, wifey's generally not.
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Old 31st August 2012, 10:40 PM   #25
TiMBoZ is offline TiMBoZ  Australia
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It's Saturday 7:33Am. Epiphany!! Whist I can't make a very wide baffle, I can make a tall deep-ish U-frame. Like 25cm wide and metre tall. Just as point, what are dimensions of the 'pencil'? 940 tall x 370 deep. Ahaaaa to the garage!
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Old 1st September 2012, 04:24 PM   #26
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Timboz,

Please post pictures when you build! Will this be prototype?
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Old 30th October 2012, 04:54 AM   #27
TiMBoZ is offline TiMBoZ  Australia
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Update: (Don't wanna deconstruct my Ziv kit floortsanding TL) so I have bought some SB Acoustics 8 inch woofers for 30 litre sealed box. Qtc: approx 0.8. MDF cabinet/baffle plans @ Mr Plywood for cutting. U/frame baffle at 280mm wide 1200mm tall. Have devised a method for measuring roll off of open A-10 in baffle. Using my electric guitar tuned to concert pitch using front pick-up, into a compressor, into the clean channel on my amp into the A-10. Playing notes in 80Hz (open E) > 500Hz range. This should give me a reasonable idea of what the effective range of A10 is and help to form/tune a XO to sealed SB woofer.
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Old 7th November 2012, 11:52 PM   #28
TiMBoZ is offline TiMBoZ  Australia
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Update: taken the referral from Monte Verdi and have ordered Alpair 12P's after much consideration between Alpair 12 vs 10 vs 7. Will build prototype to test 12P vs 10.2 on 280mm wide open baffle, with U-frame sections with 8 inch sealed boxed woofer. Passive XO. Will start a new thread once prototype is built. End of this thread. Stay tuned...
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Old 25th November 2012, 02:40 PM   #29
zman01 is offline zman01  Bangladesh
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TiMBoz,

How is the project coming along?
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Old 25th November 2012, 08:20 PM   #30
TiMBoZ is offline TiMBoZ  Australia
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Hi there, I have the A12Ps with an 8 inch woofer mounted in a hybrid baffle (probably to deep U-frame) - which looks a but like a Thiel 2.4. Got it up and running yesterday. Managed a modest listen for about an hour or so. Once I have photos I'll start a new thread.
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