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Old 24th December 2012, 06:16 PM   #21
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Thanks for your comments, Scott.

Is lowering the combined resonance a good thing in your opinion?

To everyone: What do you think of using one slot port instead of two? I know it would raise the possibility of chuffing noises as the vent mach would go up a little bit.... any other effects good or bad? I'm thinking something like 0.5" x 8" x 6.24" but keeping it near the driver still rather than at the bottom.
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Old 25th December 2012, 07:16 PM   #22
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Ben_Tech View Post
Thanks for your comments, Scott.

Is lowering the combined resonance a good thing in your opinion?

To everyone: What do you think of using one slot port instead of two? I know it would raise the possibility of chuffing noises as the vent mach would go up a little bit.... any other effects good or bad? I'm thinking something like 0.5" x 8" x 6.24" but keeping it near the driver still rather than at the bottom.

Many quite successful enclosures, commercial and DIY alike utilize a single vent, and none of numerous designs by Scott, Dave, or more recently, Bob Brines' M10-A10, have had issues with "chuffing" or "port-noise complaint"


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While not yet shown on your sketches, or to my recollection described in your posts, don't overlook panel wall bracing - the 10.2 is capable of prodigious amounts of LF energy for its size, and while your slot vent strategy will provide some bracing in the immediate vicinity of drivers, there's still a lot of panel surface for which no amount of fibrous damping will control panel resonances. The designer of these drivers is on record this his own thoughts on the subject of enclosure bracing, which is often left out of drawings for sake of simplicity - that should not be taken as license to omit without consequences.
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Last edited by chrisb; 25th December 2012 at 07:26 PM.
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Old 25th December 2012, 07:44 PM   #23
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Yes, I was thinking of bracing it. Although it is a very shallow cabinet so the pieces will be small so I thought they might not resonate as much. I am aware of shifting the driver's energy to the back panel as a benefit. I think a front to back brace will do it. Thanks for your encouragement to brace, I would probably have been lazy and omitted any additional bracing otherwise.

On the vent issue, do you think, when the speaker is rotated sideways to use as a center channel, that the single vent approach might not be as good as a dual vent approach? One vent is appealing to the lazy woodworker in me, but I don't want to compromise too much either.

Merry Christmas, Chris and Dave.
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Old 25th December 2012, 08:39 PM   #24
chrisb is offline chrisb  Canada
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Originally Posted by Ben_Tech View Post
Yes, I was thinking of bracing it. Although it is a very shallow cabinet so the pieces will be small so I thought they might not resonate as much. I am aware of shifting the driver's energy to the back panel as a benefit. I think a front to back brace will do it. Thanks for your encouragement to brace, I would probably have been lazy and omitted any additional bracing otherwise.

On the vent issue, do you think, when the speaker is rotated sideways to use as a center channel, that the single vent approach might not be as good as a dual vent approach? One vent is appealing to the lazy woodworker in me, but I don't want to compromise too much either.

Merry Christmas, Chris and Dave.
I can only relay my experience with the dozens of Dave's "mini-onken" based designs I've built for Mark Audio and other drivers - when compared to more standard single slot or round ported variants of comparable enclosure volume and tuning, the multiple high aspect ratio vents provide more control of the LF roll-off characteristics, and are to me well worth the effort. What's an extra half hour or so of fabrication time and dollar or two of materials per box in the grand scheme of things?

When you're building multiples of an identical enclosure, what seems like will take a lot of extra time can actually go much faster thank you think - certainly in terms of cutting half a dozen more identically sized pieces. Of course the assembly is a different matter, I don't know anyone with too many clamps or too large a work space.

So in other words, I'd definitely go for the dual slot vents per enclosure.

As to bracing, guess what? there are different schools of thought on that! - i.e. what constitutes a "structural brace" or a "resonance tuning rib" (best example of the latter I can evoke, and have built, is the AudioNote E- a very "tune-full" enclosure indeed)

FWIW, I always seek for each bracing member to each couple to as many of the panel walls as possible, and to place them to not divide the panels at equal intervals . On longer designs such as the Pensils, I usually combine interlocked cross bracing at approx 60/40 length of box, with short perpendicular spars on the longer section. There's pictures of that somewhere, just not on this 'puter.
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Last edited by chrisb; 25th December 2012 at 08:41 PM. Reason: trying to catch the typos - the grammatical structure is another thing entirely!
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Old 25th December 2012, 09:48 PM   #25
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Quote:
Originally Posted by chrisb View Post
There's pictures of that somewhere
This one should get the idea across.

Click the image to open in full size.

dave
Attached Images
File Type: jpg Fonkenbrace.jpg (60.0 KB, 306 views)
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Old 29th December 2012, 07:56 PM   #26
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OK, here is the latest - version 7!

Click the image to open in full size.

As you can see, much harder to build than my previous sketches.

External:
width: 9.5"
depth top: 6"
depth bottom: 10"
height: 39"

3/4" (19mm) plywood cabinet.

Internal (sound chamber only):
width: 8"
depth top: 4.65"
depth bottom: 7.6"
depth driver to back wall: ~ 3"
height: 28.5"

Total volume around 23 liters in the sound chamber. Void space at the bottom.

Off center holey brace shown in gray - approximate volume of brace ~ 1 liter.

2 x slot ports, 5.6 long x 7" wide x 0.25". Tuning frequency ~ 38-40 Hz - approximate volume taken away from sound chamber ~ 1 liter.

The driver magnet and frame and cleats for holding the removable back panel (not shown) will take a bit of internal volume also.

So it should work out to roughly 20 liters.

Please let me know what you think of this latest design.

Last edited by Ben_Tech; 29th December 2012 at 08:00 PM.
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Old 29th December 2012, 08:05 PM   #27
chrisb is offline chrisb  Canada
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looks cool - I'd add a couple of short bracing spars coupling each side of the front to back brace to the side panels - like in the photo posted above

I think you'll find the braces to be the most time consuming part of fabrication
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Old 29th December 2012, 08:19 PM   #28
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Originally Posted by chrisb View Post
looks cool - I'd add a couple of short bracing spars coupling each side of the front to back brace to the side panels - like in the photo posted above
Thanks for your valuable input, Chris - even with an internal width of only 8" (about 20 cm)?
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Old 29th December 2012, 11:36 PM   #29
chrisb is offline chrisb  Canada
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Originally Posted by Ben_Tech View Post
Thanks for your valuable input, Chris - even with an internal width of only 8" (about 20 cm)?
I think so, it's the length of the side panels above the false bottom that I'd be concerned about, and it wouldn't take much to couple them to the longitudinal brace with one or two narrow ( 3/4" x 3") "spars" per side- spaced off center
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Old 29th December 2012, 11:50 PM   #30
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Ok, then! I'll add the spars. I'll start working on a matching center channel drawing over the next few days.
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