Attached are the cabinet plans for a kit I just built. It sounds very good and I'm not detecting cabinet vibration with music, meaning no excessive upper bass warmth and the cabinets "disappear" properly and form a solid image. However, with such a large box, in your experience, would bracing be beneficial? Or since it sounds good, just leave it be?
If you want to isolate what the cabinet is doing use a mechanics stethoscope.
That drawing helps a project i am working on.
In discussions about the A26 cabinet, bracing should be added. I plan on a redraw (for a couple flat-pak makers at a minimum).
At least 1 brace solidly connecting baffle and bass driver to the top, bottom and back. Side-to-side brace is a bit trickier.
dave
That drawing helps a project i am working on.
In discussions about the A26 cabinet, bracing should be added. I plan on a redraw (for a couple flat-pak makers at a minimum).
At least 1 brace solidly connecting baffle and bass driver to the top, bottom and back. Side-to-side brace is a bit trickier.
dave
David,
See link below, scroll way down to "Enclosure bracing for the Seas A26"
The Seas A26 is similar to a design made by world audio design years ago for the same bass driver, same Dynaco A25 concept, just cheaper tweeter ... I like what they did and as far as I know, the bracing was determined by experienced designers. This is what I would do, honestly, just scaled to my A26 cabinets.
seas Archives - Roderick van Domburg's Blog
I've goofed with that in the past, didn't care for the net effect, honestly.
The part of the cabinet most likely to deflect (vibrate) is the baffle. It has two holes in it, one of which is a very large hole. This reduces the baffle stiffness significantly. Stiffening up the baffle will provide the most improvement of any alteration... it will give you " the most bang for the buck".
There are several ways to stiffen the baffle.
One is to double the baffle thickness. If you do this you must not change the interior dimensions, instead you must grow the cabinet depth by 19 mm.
Another is to fix a brace from the rear wall to the woofer, as GM said.
For me, the easiest and most simple way to stiffen the baffle is with a horizontal brace between the woofer and tweeter, as shown in the photo. This will make the baffle more stiff than if it were double thick. It also seems easier to fabricate than a brace which preloads the woofer (but maybe I am not being envisioning how that would be precisely dimensioned).
There are several ways to stiffen the baffle.
One is to double the baffle thickness. If you do this you must not change the interior dimensions, instead you must grow the cabinet depth by 19 mm.
Another is to fix a brace from the rear wall to the woofer, as GM said.
For me, the easiest and most simple way to stiffen the baffle is with a horizontal brace between the woofer and tweeter, as shown in the photo. This will make the baffle more stiff than if it were double thick. It also seems easier to fabricate than a brace which preloads the woofer (but maybe I am not being envisioning how that would be precisely dimensioned).
Attachments
I am well familiar. Scott and i did a Classic TL (in topology, but using modern modeling).
http://p10hifi.net/tlinespeakers/FAL/box-plans/classicTL-revisited-WD.pdf
If someone wanted to build this today, i think we would like to look at the design again.
dave
If it sounds good i see no reson to add bracings. Bracings seems only to be effective at the braced area so one needs to add many bracings to cover larger areas. The bbc style of enclosure walls seems more attractive , stiff thin walls with thick layer of bitumen damping to get an inert cab. Stiff ceramic cabs looks attractive too but how do we make them in an easy way?
I'd suggest a perforated dividing panel, firmly attached to side walls and rear wall. Fill the space between panel side and woofer magnet with some viscoelastic material (anything a marble doesn't bounce off when dropped upon would do) and mount the woofer with grommets under the bolts/screws and a reasonably thick gasket. Not really simple, but hey, we're DIY.
On the interior damping: I would double the suggested 50g.
Bracing a cab can be tricky if the LF driver is doing alot of the midrange. Once you shift the panel resonance up into the more audible midband area, its harder to mask it. I'm tempted to build a pair of A26 boxes with a sand filled walls. I had a set of old Leaks that were sand filled and they sounded great. Another option is filling walls with epoxy resin, but that may not add enough mass as a constrained layer.
But if you can get it up high there will be little energy up high enuff to get it moving, and if the (potential) resonance is hi Q you are much much less likely to ever get a sufficiently sustained high frequency note to excite it.
The boxes i design are mostly single driver FR speakers. The bass driver goes all the way up.
dave
The boxes i design are mostly single driver FR speakers. The bass driver goes all the way up.
dave
CLD technique doesn't rely on the mass of the layer, but on it's plastic behavior and the bonding with the outer layers. The shear movement in the middle layer has to be 'absorbed' as in: as much as converted to heat as possible.
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