Alpair 10 vs Alpair 7 - Open baffle with boxed woofer. Passive Xover. - Page 5 - diyAudio
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Old 22nd May 2013, 03:04 AM   #41
TiMBoZ is offline TiMBoZ  Australia
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G'day Bill poster, blow the dust of this thread...blow, wipe, sneeze

I'm still working on my proper boxes/U-frame, progress is very slow, for lack of man-cave time. Also it's quite an ambitious project for me, digesting, learning which direction to go in, what the speaker is supposed to be and so forth. I'm in no rush.

My suggestions: think very carefully about the flavour of speaker you're trying to make. Your taste in music.

For classical and jazz, mostly acoustic music - I'd just do a nice wide door sized open baffle (as wide as you're allowed/wide as you can ) with a 12P and let it roll off naturally, no filter. Drive them with a good valve amp. It's surprising how satisfying this arrangement is, even without any assist from helper woofer. Depending on baffle width, fill in the bottom <200Hz with a good quality sub (or 2), well positioned with good power and XO filter controls. The wider your baffle is, the less fill you'll need. Soundwise, OB won't get much better than this. IMO.

Hopefully you have a big room, the bigger the room the better it will sound.

With a high 6db XO, active and effectively 2 amps an active woofer will spoil, probably won't integrate very well with the midrange of the open driver. I wouldn't attempt a bi-amp with XO at 6db (425 - 450Hz).

For myself, my speaker is for 1 x powerful S.S amp listening mostly to adult contemporary pop. I'm thinking passive inverted 2 way. XO somewhere between 200 - 400 3rd order, 18db roll off on the woofer. Aiming vaguely like a poor man's love child of a Thiel 2.4 mated with a Nola Baby Grand Reference. No pretence of it being the ultimate speaker, just a concept I really like. It's unusual. I love the look of the Thiels. Anyways I'm just going to finish building it then worry about the XO later.

errr..important points for passive: with a higher XO the drivers must be mounted close together. The XO will be critical.

Make the woofer 'box' as close to sonically invisible as you can make it. Perhaps sealed box. You'll want to roll the woofer off quickly otherwise it will spoil the nice open midrange of the wide range driver above - which is kind of the whole point.

Hope this is helpful.

Last edited by TiMBoZ; 22nd May 2013 at 03:22 AM.
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Old 22nd May 2013, 09:02 AM   #42
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Thanks TIMBoZ for answering, you've got me thinking... If I needed to have a steeper roll off for the woofer, yes I'd rather go for a 3rd over a 2nd, for phase reasons(passive). If I set the x/o of the woofer at around 250hz or so then that wd add some BSC, so cd work well. The full range is effectively mounted in a tube with little to no baffle, almost like a jet engine. The woofer wd be set into a curved enclosure with a smallish baffle
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Old 22nd May 2013, 11:28 AM   #43
TiMBoZ is offline TiMBoZ  Australia
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Quote:
x/o of the woofer at around 250hz
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The full range is effectively mounted in a tube with little to no baffle, almost like a jet engine.
Bill P, I think/suggest you'd have to sketch/draw your idea, as a start. Certainly sounds different/interesting.

I guess the tube starts to become like a back horn/pipe? Would the tube/pipe get the extension of Alpair down low enough to meet the woofer 200 - 400Hz?

I don't know how to calculate for something like this. kind of outside my scope.

I would do the baffle as a shallow box without a back. Like a large flat tray, add the woofer underneath. Ideally, choose a woofer much more sensitive than the Alpair (or as close as poss), for passive.
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Old 27th February 2014, 04:10 PM   #44
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digging this up after nearly a yr - I've bought a couple of pairs of Alpair 10p's and plan to make 2 sets of speakers (one in UK and one in Thailand)

Will use the Alpairs in an open baffle (x/o 325hz) but plan to mount the 2 woofers side firing and slant the baffle about 10 degrees back or whatever it take to time align.
The woofers will be 6.5", about to take the plunge and order 4 Scanspeak 8535-01's for the first build
In parallel, these will output 93dB.

Will post a sketch soon
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Old 27th February 2014, 05:02 PM   #45
chrisb is offline chrisb  Canada
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5 dg is a nice tilt angle - I've used that on at least half a dozen builds

and if budget permits, bi-amping substantially simplifies "FAST" type 2-way systems
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Old 27th February 2014, 05:41 PM   #46
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Quote:
Originally Posted by Bill poster View Post
... 4 Scanspeak 8535-01's for the first build, In parallel, these will output 93dB.
As i understand it that sensitivity will be shy of what you really need for an OB. With A10p at 90, another 3dB or so would be nice if you plan a passive XO... so time to think active.

dave
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Old 27th February 2014, 06:00 PM   #47
chrisb is offline chrisb  Canada
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bill - if no-one's asked yet, what is that interesting contraption in your avatar photo?
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Old 27th February 2014, 08:58 PM   #48
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Originally Posted by planet10 View Post
As i understand it that sensitivity will be shy of what you really need for an OB. With A10p at 90, another 3dB or so would be nice if you plan a passive XO... so time to think active.

dave

sorry didn't explain well, the scanspeaks won't be OB, just the alpairs- 93dB output on the woofers shd be enough? no?
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Old 27th February 2014, 09:08 PM   #49
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Chris it's a Gandini concept from 1970 called the Stratos zero, same guy who designed the Countach and also the Citroen BX in the 80s.
http://4.bp.blogspot.com/-i_tB0l8c1w...os_zero_09.jpg
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Old 27th February 2014, 09:12 PM   #50
chrisb is offline chrisb  Canada
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now that's almost as cool as it is totally impractical - what do you guess, 280 degrees of blind spot?
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