Alpair 10 vs Alpair 7 - Open baffle with boxed woofer. Passive Xover.

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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.
 
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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
 
x/o of the woofer at around 250hz

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.
 
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
 
back to speakers, I hope that 3db is enough, I'm thinking most people find a full 6dB BSC too much?
I want to have a certain balance to the sound and not overpower the treble on the alpairs- I'll pad the 10P's at the back anyway, so the output will be reduced slightly, plus the 10% slant on the baffle will tame them a bit

The 10P's have a 50 ohm spike at Fs, which starts to rise south of 200hz.
With a first order at 300-350hz, I hope I can get away with it
 
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I finished up with an Alpair 10.3 M U-frame/shallow open backed box if u like, over an SBA 8 alloy woofer in approx 40 L box. U-frame/Box from epoxy, MDF, porcelain tile. Etc. Port tuned buy ear. Passive XO approx 400Hz, padding on the 10.3M. They weigh 70kgs ea. took me 3 years of spare time in the man cave. I finished 3 months ago. They sound gr8 but are a bit too big for my space: need to be (sound best) further away from the walls than is practical. But I drag them into centre of room for a listening session whenever I get the chance. They have sum large impedance correction on them and you have to put the boot into them a bit to get them singing. I used Troels Gravesen's 'Acapella' as a starting point but just omitted the tweeter. I've invested alot of time and money into them. I'ved finished with speakers for the time being, I still have a small SE valve amp kit to build. Thanks for asking
 
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