Driver Hole Chamfer and Alpair 7

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Any unique recommendations for the Alpair 7 driver hole chamfer. Typically I cut the back of the hole at a 45 degree angle using a router.

Hi Pizzachef,
Yes to 45 degrees. This is a good way to minimise any reflections coming from the side of the baffle back on to the rear of the cone.

The 45 angle is usually easy to do on thicker baffles (over 18-mm). For those guys on thinner baffles (less than 18-mm) who want to use the 7's front cover and recess the driver, the mount behind the driver will be shallow. In these cases, it may be better to round off the back of the baffle opening. A radius of 2mm to 3mm will help minimise any disturbance around the rear of the driver.

Thanks
Mark.
 
Thanks. Sorry to ask such small questions, but I have found Markaudio to be as helpful as any manufacturer I have met to the DIY community. Not to mention having some pretty awesome product. Been running in my bare Alpair 7's at low volume for about 100 hours now, can't wait to get them in a box
 
I believe Troels Graverson did a test of this theory and showed that it did not make a significant difference. I could be remembering wrong.

Hi Buzz, Guys
For Markaudio drivers, it is wise the chamfer the inside of the baffle opening. The rear of the Markaudio driver frames are near wide open to help minimise back wave losses so large side wall with a sharp edge could expose the rear of the cone to reflection.

When I first kicked off making my Gen. 1 Alpair 10's, we kept getting some weird peaks during the anechoic sweep tests. It took me and Evan ages to find the problem. We'd been using a 19-mm thick suspended baffle with a straight cut mounting insert. When we changed to another baffle that used a 3-mm aluminium central mounting plate, ran the sweep test again, the problem was resolved. I'll look at our archive data and see if I've kept an LMS data copy of these tests.

I can't speak for other driver designers since their designs will likely have differing criteria. It could be that for some drivers, chamfering baffle edges isn't needed. But as a handy good practice tip, its usually worth trying to smooth off sharp edges inside baffles, similarly on ports and vents.

Hope this helps.

Thanks

Mark.
 
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Thanks. Sorry to ask such small questions, but I have found Markaudio to be as helpful as any manufacturer I have met to the DIY community. Not to mention having some pretty awesome product. Been running in my bare Alpair 7's at low volume for about 100 hours now, can't wait to get them in a box

Hi Pizzachef,
No need for apologies, helping guys with their ideas and projects is the major part of Markaudio section's purpose. Please accept my apologies for sometimes not being readily available to answer all posts.

I'm hoping that more members will share the knowledge and project build experiences so this section of the Diyaudio forum gets close to being self-supporting, me helping with technical supports on the drivers.

Cheers
Mark.

(PS. keep it nice and gently on the run-in. Soft, easy music and cone's shouldn't move - thanks)
 
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frugal-phile™
Joined 2001
Paid Member
Here is a picture of a driver cutout scheme that leaves more meat for securing/supporting the driver, but does bring the baffle hole closer to the cone (so the champher is even more important).

Note: we don't actually use this technique. As much a thot experiement implemented as anything else. A striking similarity in concept to the foam gaskets shipping with the new CHR/CHP/CHBW. These gaskets are a big improvement.

dave
 

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I thought about this as well, particularly with the CSS EL70. My problem is that there never seems to be enough meat on the baffle where the screw hole has to be, and this does not really solve that problem as the sort of ear-like cutouts are right where the screw holes have to be. Though on the EL70 I thought about using a jigsaw just to cut out slits of the flanges on the driver arms (I am sure I am not using any of the right terms). With very little material removal you could get at least another 3/16 less cutout all the way around. Haven't tried this, though.

My solution, not sure if it is right, is to do a chamfer in four separate arcs such that the area around the screw hole is not chamfered to give the mount, either the T-nut or screw, more wood to hold. Since the area that is not chamfered is also where the driver arms are, I don't think the reflections would be worse or better this way.
 
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I thought about this as well, particularly with the CSS EL70. My problem is that there never seems to be enough meat on the baffle where the screw hole has to be, and this does not really solve that problem as the sort of ear-like cutouts are right where the screw holes have to be. Though on the EL70 I thought about using a jigsaw just to cut out slits of the flanges on the driver arms (I am sure I am not using any of the right terms). With very little material removal you could get at least another 3/16 less cutout all the way around. Haven't tried this, though.

My solution, not sure if it is right, is to do a chamfer in four separate arcs such that the area around the screw hole is not chamfered to give the mount, either the T-nut or screw, more wood to hold. Since the area that is not chamfered is also where the driver arms are, I don't think the reflections would be worse or better this way.



exactly - the photo in Dave's post above was for a different application

I'd describe the process as scalloping the chamfer around the (4) driver arms - somewhere I have a low grade cel-phone picture thereof

if not already obvious, I tend to concentrate on building not photographing
 
frugal-phile™
Joined 2001
Paid Member
I thought about using a jigsaw just to cut out slits of the flanges on the driver arms (I am sure I am not using any of the right terms). With very little material removal you could get at least another 3/16 less cutout all the way around.

I call them basket legs.

Anyway, you don't want to be cutting away at them, particularily the plastic baskets. It would dramatically reduce their stength

dave
 
no, I wouldn't in my wildest dreams start carving on the driver. No, what I meant was that the radius of the driver cutout is really driven by some very narrow flanges on those basket legs. I was thinking about using a jigsaw to make very thin cuts radiating from the center of the driver hole for those flanges, so that the cutout could be smaller.
 
How about a back mount and a radius on the front that is the same as the baffle thickness:
ie: 3/4" baffle thickness and a 3/4" radius.
Peter C.



assuming easy access via removable back panel, I think you'd run into issues of usable length of screws due to the tight spacing of their mounting holes to driver cut-out , or at least need to take great care not to drill pilot holes too deep.



quick sketch attached is not absolutely to dimension as to basket leg details, but is accurate for front flange of current version without extra bezel and optional magnet

when front mounted and rebated for flush mount, the rear chamfers should be scalloped to form pads at the basket legs, as seen here for EL70 :
 

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