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Old 28th June 2010, 11:44 PM   #1
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Default Alpair 12 - Studio Monitor Plan

Hi Guys,
Scott and Dave have continued this interesting double chamber concept with a version for the Alpair 12. Any guys who've already built BR's, other vented or possibly Pencil 12's, this new plan will be an interesting comparison.

For new builders, this plan would make an excellent candidate for first time or subsequent builds.

I've suggested making the rear panel removable to allow for experimentation of damping materials, or just in case the material isn't positioned quite as you'd like. It's important to keep any material clear of the vents. Given that the lower chamber is a near-closed section, those builders with less experience might find the removable rear panel useful. Builders with more advanced skills may have the confidence to go for a fixed rear panel.

I'll ask Scott and Dave to comment of this option, or if they can offer more or alternative advice.

Cheers

Mark.
Attached Images
File Type: gif MA-Alpair12-DBR-280610-plan.gif (53.6 KB, 1375 views)
File Type: gif A12-DBR-sim.gif (28.4 KB, 1154 views)

Last edited by markaudio; 29th June 2010 at 12:03 AM. Reason: additional info
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Old 29th June 2010, 01:03 AM   #2
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I've been skeptical on a dbr (double reflex) due to the impedance plot and the tuning in the lower midrange. The freq plots of fostex dbr designs show large dips in the freq response.

I know 30hz tuning is far superior than 40hz (speed) on my subwoofer. I have a friend who recommend never tuning above 50hz (2 way or a full range driver) due to the delay............

On the otherhand the multiple tuning really halts the cone motion, which is always an excellent idea (less glare / warble / distortion).

I look forward to any results (I ordered 2 alpair 12 from stereoclarity last week, excellent seller).

Norman

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Old 29th June 2010, 01:35 AM   #3
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Quote:
Originally Posted by norman bates View Post
I've been skeptical on a dbr (double reflex) due to the impedance plot and the tuning in the lower midrange. The freq plots of fostex dbr designs show large dips in the freq response.
I know 30hz tuning is far superior than 40hz (speed) on my subwoofer. I have a friend who recommend never tuning above 50hz (2 way or a full range driver) due to the delay............ On the otherhand the multiple tuning really halts the cone motion, which is always an excellent idea (less glare / warble / distortion).

I look forward to any results (I ordered 2 alpair 12 from stereoclarity last week, excellent seller).

Norman
Hi Norman,
How are you? Long time since we last swopped posts. Scott is better placed to pick up your points but I've found the Pencils exhibit a very smooth delivery. I don't have their plots to hand but from my memory, also had some variance. The plots Scott's produced are software generated rather than measured, so let's hear how they sound.

These double chamber designs are "experimental", hence my suggestion of a removable rear panel to play with the damping. Scott is confident these designs will be effective and musically pleasing.

Yes, Steve's very helpful and does excellent box work. Hope you like my Alp12's. Please remember the run-in period: see -

Running In- Alpair 7 and 12

Cheers,

Mark.

Last edited by markaudio; 29th June 2010 at 01:48 AM.
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Old 29th June 2010, 03:53 AM   #4
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Hello Mark, how are you ?

I'm taking a huge interest in the 12's now that I ordered some.

I was about to print out the pencil 12 thread till I saw this thread.

There is a project using the 4" bamboo called the "bandit". It is a dbr.
Bandit

Looking at the alpair 12 monitor, it should act like a ported but block higher frequencies from coming out of the port. I mistook this design for a dbr design (which is also an option). Actually techincally it is a double reflex (port to second chamber, port to outside world), while the "bandit" is a tripple reflex.

Can I put alpair 12 on an open baffle ?
I run at low volume (usually under 80db). I was able to run a 3" wide open on an open baffle.

Norman

Last edited by norman bates; 29th June 2010 at 03:56 AM.
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Old 29th June 2010, 06:05 AM   #5
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Quote:
Originally Posted by norman bates View Post
Hello Mark, how are you ?

I'm taking a huge interest in the 12's now that I ordered some.
I was about to print out the pencil 12 thread till I saw this thread.

There is a project using the 4" bamboo called the "bandit". It is a dbr.
Bandit

Looking at the alpair 12 monitor, it should act like a ported but block higher frequencies from coming out of the port. I mistook this design for a dbr design (which is also an option). Actually techincally it is a double reflex (port to second chamber, port to outside world), while the "bandit" is a tripple reflex. Can I put alpair 12 on an open baffle ? I run at low volume (usually under 80db). I was able to run a 3" wide open on an open baffle.
Norman
Hi Norman,
Doing OK thanks, busy though preparing Alp6 and Alp 10. Had hoped to be further forward but there's an advantage in taking our time to get the components even better.
Re the A12 Monitor, its going to be interesting to hear how it performs. I'll see Tony later today so I'll him the plan to build in Oakwood, them compare with the Birch Japan Pencil 12's here in the studio. Yup, technically speaking, Scott's made "hybrid" double bass reflex. He might have time to comment a little more later, although its a worthy "experimenter", from which results and impressions may lead on to possible teaks?

Anyway, coming back to A12 in OB, there's a thread in full range where some guys have done some work on this, so its worth using the forum's search facility. From my "makers" perspective, there's potential in the A12, especially for the mids-high (woof for the low). The A12's dispersion and its power-train compliance make it a good candidate for use on O/B.

I think you'll be very pleasantly surprised by the A12 once you've got them up and running.

Cheers

Mark.
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Old 29th June 2010, 07:08 AM   #6
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Hiya Mark, alpair 10 gen 2 should do very well, especially comercial side to speaker sellers (konus audio, aurousal, robyatt audio, etc). Thank you for all your posts.

I've been following the thread on alpair 12 and open baffles.

I'm thinking alpair 12 on a 3' x 4' with a foam box around the back, and my 15's rolling at 80hz at 6db for bass. Not room friendly, but then again neither am I. I'm sure voice will be magical. I do not want the front wall bounce.

Norman
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Old 29th June 2010, 07:48 AM   #7
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Quote:
There is a project using the 4" bamboo called the "bandit". It is a dbr.
Bandit

Looking at the alpair 12 monitor, it should act like a ported but block higher frequencies from coming out of the port. I mistook this design for a dbr design (which is also an option). Actually techincally it is a double reflex (port to second chamber, port to outside world), while the "bandit" is a tripple reflex.
This box (the A12 cabinet) is a Double Bass Reflex enclosure. The 'Bandit' is an Augspurger / Weems style Double Chamber Reflex, where both chambers are vented.

Quote:
Can I put alpair 12 on an open baffle ?
No reason why not, providing you're either a/ not expecting any bass, or b/ supporting them with woofers.

Quote:
My sample was already done by the maker. The rear panel is fixed and can not make it removable. Is there any technique to put damping material into the lower chamber and make it attach onto the rear wall?
Short of building a teleportation device, that's going to be awkward. They'll likely have a peak at Fb & a heavy boom in the bass, although you could probably attenuate this by stuffing the external vent with open-cell foam.
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Old 29th June 2010, 08:46 AM   #8
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The plans in post 1 have been updated. Some glitches fixed and cleats added so that the back can be removed s per Mark's comments.

pdf version of plans

And a bit bigger visualization

Click the image to open in full size.

dave
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Old 29th June 2010, 06:51 PM   #9
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How is it possible to explain my wife that Ill have to build these new monitor -type loudspeakers altough Ive just finished a pair of Pencil 12? Im really interested to play these new monitor speakers with the pair of Pencil 12. If there is someone a bit more lucky than me, should you build a pair of these new loudspeakers and listen them with a pair of Pencil 12 and then tell me and all the other how they sound.

I listened today some heavymetal quite loud and I liked it! With Pencil 12 of course! In my opinion there is no need for woofers with these loudspeakers.
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Old 29th June 2010, 11:27 PM   #10
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scott "This box (the A12 cabinet) is a Double Bass Reflex enclosure. The 'Bandit' is an Augspurger / Weems style Double Chamber Reflex, where both chambers are vented."

ah. Thanks. Getting tricky, all these names for multiple chambers and reflexes.

hornet, you can build 1 of the monitor box and remove 1 of your 12's from your pencils.
Cost will be low.



Norman
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