Hi all,
After building a test OB out of MDF I'm planning on building the next iteration, hopefully the final version, and account for some needed modifications. Of course, my experimental design has demonstrated that I need more bass which will manifest itself as more, bigger drivers. To this end I was wondering if anyone has experience mounting drivers in a steel baffle?
My thoughts are:
1. More rigidity and weight, which could allow for dual 12" drivers mounted on each panel with fewer bracing/trussing elements to keep the baffle from shaking, wobbling and flexing.
2. More resonance which could possibly be mitigated by gluing a similar 1/4" thick MDF sheet over the face. Each of the two materials might cancel out the other's resonant tendencies, sort of like that acoustic sheet rock which has alloy and fiber laminates within. This MDF veneer would also allow for flush mounting the drivers without having to router the steel.
3. I envision a more spare and elegant baffle/bracket design that economizes on space and looks less bulky, thereby increasing SAR (sure.)
Any thoughts, recommendations, or invalidating experience appreciated. Btw, I have metal and wood working tools to do the job.
thanks,
gary
After building a test OB out of MDF I'm planning on building the next iteration, hopefully the final version, and account for some needed modifications. Of course, my experimental design has demonstrated that I need more bass which will manifest itself as more, bigger drivers. To this end I was wondering if anyone has experience mounting drivers in a steel baffle?
My thoughts are:
1. More rigidity and weight, which could allow for dual 12" drivers mounted on each panel with fewer bracing/trussing elements to keep the baffle from shaking, wobbling and flexing.
2. More resonance which could possibly be mitigated by gluing a similar 1/4" thick MDF sheet over the face. Each of the two materials might cancel out the other's resonant tendencies, sort of like that acoustic sheet rock which has alloy and fiber laminates within. This MDF veneer would also allow for flush mounting the drivers without having to router the steel.
3. I envision a more spare and elegant baffle/bracket design that economizes on space and looks less bulky, thereby increasing SAR (sure.)
Any thoughts, recommendations, or invalidating experience appreciated. Btw, I have metal and wood working tools to do the job.
thanks,
gary
IMO what you need is increased stiffness. Using a denser material like steel will not help in this regard unless the thickness is significant, meaning its very heavy. So maybe a baffle of 3/8" steel could work, but this seems a little over the top. Plywood is stiff because it has glue layers in between the plys that resist flexure. My advice would be to go with 3/4" or thicker Baltic birch ply or equivalent. For damping can be easy added by attaching panels with flexible adhesive or mass added using metal slugs at the top edge. Keep in mind that you are making a big resonant system, and think about the role of stiffness, mass and damping when choosing what to add.
Another good option is butcherblock material. You can get this at IKEA - their NUMERÄR countertop in birch is 1.5" thick. It is quite stiff as well as well damped. In my area there is a butcherblock maker that can supply similar stuff in a wide variety of sizes, a couple of different thicknesses, and three or four different wood species.
I think steel could work well. I would expect a higher resonant frequency if you do have issues. Bracing can be made much smaller having less effect on the audio path around the baffle compared to the typical wood construction. As charlie says though, thickness will be a balance with wieght, cost etc.. I'm using extruded aluminium channel but, my baffle is only 6" wide.
I had some 1/2" aluminum CNC'd for front and rear baffles in order to copy a Magico Mini type translam build. Worked like a charm. Not as hard to work with as steel I would think but still stiff and strong. I think it was some kind of 6000 series aluminum. I've seen people claim that it rings like a bell which is not the case at all. Just to be sure, I did use some damping material on it though.
Thanks for the replies,
I hear the endorsement for ply, butcher block, and mdf. I've built numerous boxes out of MDF and never been dissatisfied with the stiffness/rigidity, especially after putting in dowels or braces between parallel panels.
My concern with this project is that minimizing the width of the OB will leave just an inch or two of reveal at the horizontal axis of the woofers. I'm thinking that steel will provide much more support at this vulnerable spot. I am considering using 1/4 horizontal rods at these points creating a truss back to a rear vertical pole centered behind the drivers. Sort of like ribs. Here is one:
I hear the endorsement for ply, butcher block, and mdf. I've built numerous boxes out of MDF and never been dissatisfied with the stiffness/rigidity, especially after putting in dowels or braces between parallel panels.
My concern with this project is that minimizing the width of the OB will leave just an inch or two of reveal at the horizontal axis of the woofers. I'm thinking that steel will provide much more support at this vulnerable spot. I am considering using 1/4 horizontal rods at these points creating a truss back to a rear vertical pole centered behind the drivers. Sort of like ribs. Here is one:
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baffles? BAFFLES?? We don't need no stink'n Baffles!
The speakers could be attached to a heavy metal skeleton, and any baffle constructed from soft(foam) materials.
If baffle width was not an issue, a counter-force 2-drivers in push-pull W-frame could be built with standard plywood. The LinkwitzLabs site has several historic examples.
Many successful designs use plywood baffles and add metal(or boxed sand) weight to the base. Woofer cones are often 100+ grams Mms, but a typical midbass with 24grams Mms can be managed with just a heavy wood baffle.
The speakers could be attached to a heavy metal skeleton, and any baffle constructed from soft(foam) materials.
If baffle width was not an issue, a counter-force 2-drivers in push-pull W-frame could be built with standard plywood. The LinkwitzLabs site has several historic examples.
Many successful designs use plywood baffles and add metal(or boxed sand) weight to the base. Woofer cones are often 100+ grams Mms, but a typical midbass with 24grams Mms can be managed with just a heavy wood baffle.
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It is not the material you select, it is how you use it. Look in McMasterCarr for all kinds of materials. Garloite maybe?
Myself, I would not use metal just because I don't have shears, brakes, rollers and I sold my torch. But then again I would never put a woofer in an OB. IB maybe, but never OB.
Myself, I would not use metal just because I don't have shears, brakes, rollers and I sold my torch. But then again I would never put a woofer in an OB. IB maybe, but never OB.
Me thinks that soup stone plate would be wonderful material for bass baffle. Heavy, not ringing, easy to work. There are speaker cabinets and diy turntable plinths made of it.
For mids and tweeters lighter material is fine, plywood, aluminium, acrylic, polyamide etc. With dipoles the baffle should be as thin as possible. A supporting frame can be constructed in the backside midline with minimal harm to acoustics.
"Ringing" of a material as a plate is not necessarily a problem with this application (dimensions). Ringing can be damped with eg. laminated bitumen.
Flexing easily leads to sound modulation (IM distortion), to prevent this a supproting stud or frame would be wise.
For mids and tweeters lighter material is fine, plywood, aluminium, acrylic, polyamide etc. With dipoles the baffle should be as thin as possible. A supporting frame can be constructed in the backside midline with minimal harm to acoustics.
"Ringing" of a material as a plate is not necessarily a problem with this application (dimensions). Ringing can be damped with eg. laminated bitumen.
Flexing easily leads to sound modulation (IM distortion), to prevent this a supproting stud or frame would be wise.
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Now we're talking. Those look awesome. I was immediately reminded of the first Terminator movie. (We had better be careful with these...they may take over the world.)
How are the drivers mounted to the chassis? And how do they sound? I'm planning on using 2 DSP modules to dial in the EQ so my baffle serves a cosmetic purpose that can't be underestimated. I'm sure many of us have built our Frankenspeaker only to have it relegated to some distant corner of the house due to an unpopular appearance.
I also have considered an H, W, and V frame for the bottom speakers. My prototypes, (and other actively eq'ed projects) have relied extensively on SL's information. Despite having less force cancellation, I would still like to try mounting the subs in the baffle. Again, the simpler the appearance, the better.
Given the skeleton concept depicted in the pictures, the baffle could be purely cosmetic and suspended superfically to hide the wiring, magnets and spiders behind.
So metal and wood work experience and tools I have. Stone masonry? I'm still in the dark ages.
Looks like Charlie was talking about stiffness compared to weight, good plywood beats aluminum or steel in that regard.
A cubic foot of Baltic Birch plywood weighs about 41 pounds, aluminum 168 pounds, steel 490 pounds.
13 mm Baltic Birch is as stiff as 6.2 mm aluminum or 4.3mm steel, but aluminum is about 4 times the weight, steel 12 times the weight.
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