Thats what I thought, but I figured if it did anything it would dampen vibration. Guess my first guess was right. Thanks for letting us know.
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fEARful Part Eleven (11)
- Thread starter Kelly Lee
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Thats what I thought, but I figured if it did anything it would dampen vibration. Guess my first guess was right. Thanks for letting us know.
This statement illustrates a fundamental failure to understand the physics which describes panel resonance behavior. Any layer added to the panel which gives rise to a significant change in the total mass of the resulting construct will cause significant change in the bending moment of the panel and thus its resonances.
Bill has spent a great deal of time designing clever ways to brace plywood boxes for high stiffness at low additional mass. Stiffness is a fine thing in a plywood box destined to become a speaker cab - but don't let that stick you with the idea that bracing cabs is the beginning and end of vibration control. It just aint so. You can't write [or read] a rational equation for resonance that does not include a variable for the mass - and in the case of panel resonances the visco-elastic properties of the panel and its mounting are also critical. Constructs of extraordinary stiffness [and mass] can ring like a bell.
For example: bells
Dynamat or similar materials, in addition to the damping effect of the visco-elastic properties, add significant mass to the panel - typically from about a quarter up to about a half a pound per square foot. If you add that much mass to a sheet of half inch plywood the resulting panel may approach an overall doubling in mass! This is a BFD fom a vibration perspective. Setting aside the visco-elastic properties, such an addition would give rise to a big difference in mass, and thus a big difference in bending moment, and thus a big difference in panel resonance behavior. If you care stand the weight penalty visco-elastic layers are a great way to reduce panel resonance - especially so in a constrained layer format. In fact in some cases this approach is the lowest weight solution.
Bill keeps advising people with vibration problems to ignore everything but panel [box] stiffness. This is bad advice and pretend physics. In the automotive and aviation industries visco-elastic materials and constrained layer constructs are standard approaches to vibration problems - and it aint because they just aren't clever enough to make a stiff panel.
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Conversely, painting you cab, or adding rat fur, will give rise to only a small change in mass and add little or no visco-elastic damping properties and thus will have only a very small affect on resonances.
...Any layer added to the panel which gives rise to a significant change in the total mass of the resulting construct will cause significant change in the bending moment of the panel and thus its resonances.
...Stiffness is a fine thing in a plywood box... - but don't let that stick you with the idea that bracing cabs is the beginning and end of vibration control. ...Constructs of extraordinary stiffness [and mass] can ring like a bell.
For example: bells
Dynamat or similar materials, in addition to the damping effect of the visco-elastic properties, add significant mass to the panel - typically from about a quarter up to about a half a pound per square foot. If you add that much mass to a sheet of half inch plywood the resulting panel may approach an overall doubling in mass! This is a BFD fom a vibration perspective. ...If you care stand the weight penalty visco-elastic layers are a great way to reduce panel resonance - especially so in a constrained layer format. In fact in some cases this approach is the lowest weight solution.
Bill keeps advising people with vibration problems to ignore everything but panel [box] stiffness. This is bad advice and pretend physics. In the automotive and aviation industries visco-elastic materials and constrained layer constructs are standard approaches to vibration problems - and it aint because they just aren't clever enough to make a stiff panel.
This is probably all good science, but IME, Dynamat would be just as irrelevant as paint vs Duratex or carpet, at least in any practical way with regard to a fEarful used for electric bass.
I've used Dynamat to great effect to reduce ringing in thin unbraced metal and/or plastic panels (car roof, doors, hood, and plastic motorcycle luggage). The difference was immediately audible, changing the sound of the struck panel from a sustaining, high-pitched "ping" for metal, or a more muted drumming sound for plastic, to a dull, short-lived knock.
But the half-inch plywood in a fEarful has more internal damping than a car door. Also, the unbraced areas are much smaller, so any undamped resonances are happening higher in the audio spectrum, where they have less relevance to us as bass players.
As far as I'm aware, there isn't a conventional, decently braced wooden cabinet on the planet, that rings like a bell (or even like the roof of an old Honda Civic). Since we're not hearing sustained, bell-like musical pitches when we strike the panels of a fEarful, there clearly isn't the same need for add-on damping.
Also, we're talking about a bass cabinet, not a high-end home audio speaker. Dynamat might add a subtle improvement to the clarity way up high, but how much energy are we putting into the structure at 5K to 20K? Not a heck of a lot. This is one of those technical differences that might be measurable with the right test equipment, but would be meaningless on stage.
Finally, the original question was about finishes, not about lining a cab with Dynamat. And as Foz admitted, none of the suggested products carries enough mass to make a pinch of difference.
Seems to me that Bill FM is still right, at least for our purposes as bass players.
Actually, the discussion didnt start about damping a fEarful. All I said was that spray-on bedliner makes a great covering for a cabinet. Then someone asked if it changed the sound-to which I said no, but opined that it may act like Dynamat and lower the resonant frequency a bit. I still think its a good idea. Not only is it tough as nails, it also gives a little, like rubber, and on top of that, its one homogeneous piece so it seals the box completely. Not that it shouldnt be already, but its still a plus.
I don't mean to derail the damping discussing but...
I just received my fEarful 15/6/1 and 12/6/1 tube grill covers from Reliable Hardware -- sweet!
How did you you guys mount these things to prevent rattling at high volumes?
Should I just run gasket material down the inset and screw 'em in? I'd prefer not to have to screw into the baffle (unless it's unavoidable).
Thanks!
I just received my fEarful 15/6/1 and 12/6/1 tube grill covers from Reliable Hardware -- sweet!
How did you you guys mount these things to prevent rattling at high volumes?
Should I just run gasket material down the inset and screw 'em in? I'd prefer not to have to screw into the baffle (unless it's unavoidable).
Thanks!
Back from the camping trip, so I did some work today. Routed roundovers and added putty to any gaps in the dovetails.
Here's how it's looking:
Getting so close to done!
Here's how it's looking:
Getting so close to done!
Hey, ronaldpdbrandt - thanks for the update. I'm still diggin' the dovetails. It's really different to see them in plywood; don't think I've seen that before. Will you do a clear finish?
What kind of nuts are those? They look like something that would be inserted from the back for a front-mounted speaker. Perhaps you were just testing to see that they'll fit the holes.
What kind of nuts are those? They look like something that would be inserted from the back for a front-mounted speaker. Perhaps you were just testing to see that they'll fit the holes.
- Apr 3, 2003
- 35,515
- 19,945
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- Editor-in-Chief, Bass Gear Magazine
Back from the camping trip, so I did some work today. Routed roundovers and added putty to any gaps in the dovetails.
Here's how it's looking:
Getting so close to done!
Nice work!
No big deal, carry on! But they do go on the other side.
I use a C clamp to press the t-nuts firmly into the back of the baffle, saves time and frustration. Some of the T nut flanges may need to be trimmed if they are running into the mid range brace/baffle brace. Tin snips will do it.
I super tight spots and where ever I don't need to hold much weight, like with a speaker grill, I just drill and tap the plywood to take a 1/4-20 machine screw.
The dovetails turned out really cool, I should pull out my dovetail jig and master it.
I use a C clamp to press the t-nuts firmly into the back of the baffle, saves time and frustration. Some of the T nut flanges may need to be trimmed if they are running into the mid range brace/baffle brace. Tin snips will do it.
I super tight spots and where ever I don't need to hold much weight, like with a speaker grill, I just drill and tap the plywood to take a 1/4-20 machine screw.
The dovetails turned out really cool, I should pull out my dovetail jig and master it.
I'm just glad somebody caught my error before I confused myself any further. This project has been a constant learning experience--of all the things one shouldn't do when building a cabinet! I think it's somehow going to end up okay, despite my daily, unintentional self-sabotage.
I received my 1515/66 crossover that Ron Anchak put together for me, and IMHO he does excellent clean work! (Anchak audio works, on the list).
I also bought a pre-made 1212/6 X-over from Leland Crooks, speakerhardware.com, for a non fEarful mod and it was extremely well done.
Both very reliable resources IMHO.
I also bought a pre-made 1212/6 X-over from Leland Crooks, speakerhardware.com, for a non fEarful mod and it was extremely well done.
Both very reliable resources IMHO.
Chef
In Memoriam
Howdy!
Thinking about working my way into Fearful land.
I'm pretty sure I know what I want to do, but want some feedback from you.
I think what I probably want is two 12/6/1; but dang if that's not a pricey rig with the new neo prices.
If I went 12/6/1+12sub, am I going to wish I hadn't for "lack of mids and highs?''
In my limited experience, I think I prefer the Alphalite6 over the 18Sound.
I'd like to use the 12/6/1 standalone for smaller jobs, and with my double bass, and the stack for bigger electric jobs
.
In any of the 3 bands I currently work with, my rig "is it," and I don't go thru the PA. One band is using two Bose stick/subs, and the other is using older Peavey stuff. None are hugely loud.
My GK MB-Fusion and two neoII-112's is mostly what I use, but it doesn't have the low end hammer I really like.
thanks for advise;
alan
Thinking about working my way into Fearful land.
I'm pretty sure I know what I want to do, but want some feedback from you.
I think what I probably want is two 12/6/1; but dang if that's not a pricey rig with the new neo prices.
If I went 12/6/1+12sub, am I going to wish I hadn't for "lack of mids and highs?''
In my limited experience, I think I prefer the Alphalite6 over the 18Sound.
I'd like to use the 12/6/1 standalone for smaller jobs, and with my double bass, and the stack for bigger electric jobs
.
In any of the 3 bands I currently work with, my rig "is it," and I don't go thru the PA. One band is using two Bose stick/subs, and the other is using older Peavey stuff. None are hugely loud.
My GK MB-Fusion and two neoII-112's is mostly what I use, but it doesn't have the low end hammer I really like.
thanks for advise;
alan
From what I remember about the early fEarful threads, an alphalite is fine for keeping up with one 3012LF, but if you go up to a 3015LF or to two 3012LF's, the alphalite doesn't have the output to keep up.
The 18sound does produce enough mids to keep up with a 3015LF or two 3012LF's but can overpower a single 3012LF with the mids it produces, so in applications where an 18sound is used with a single 3012LF, you can pad it back around 6db (that's from memory).
I think the conventional wosdom is to have a 12/6/1 with a switchable pad for the 18 sound mid., so that when used as a standalone cab you can pad the mids back, when adding a 12 sub you can let the 18 sound loose
+1 - Spot on! Wits the 3015LF driveres it is a bit of a different story if you want equal volume across the full frequency range, but for the 3012LF drivers, one 18 sound mid is perfect.
BurningSkies
CRAZY BALDHEAD
- Feb 20, 2005
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- 20,348
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- Endorsing artist: Dingwall Guitars
Hey Chef,
The diagram for the 12/6 with the 18 Sound DOES have an option for the switch. I installed one on my 15/6 and it wasn't a matter of too much complexity...beyond the part where I went and had do insert mine in-cab since my crossover, Lpad and input plate were all mounted.
Thanks! Yeah, I've got foam gaskets for the handles.
Today I put a 1/4" round on the grille standoff, painted it brown (I had already painted the baffle the same color), and stapled on the grille cloth. I also added my logo plate. I had designed this logo a while back, and had always wanted to use it on something. I thought this would be a good opportunity!
Chef,
I'd build a pair of mirror imaged 12/6 cubes and use the Eminence 6. Keep it simple.
I use one 12/6 with an acoustic rock act with vocals + acoustic guitar in a Bose system. I can eq like a fool and still bury the Bose with headroom to spare with a Thunderfunk TFB420.
Also, put a tilt back leg on the one built for solo use.
Feel free to PM me for any questions you might have.
Jim
I'd build a pair of mirror imaged 12/6 cubes and use the Eminence 6. Keep it simple.
I use one 12/6 with an acoustic rock act with vocals + acoustic guitar in a Bose system. I can eq like a fool and still bury the Bose with headroom to spare with a Thunderfunk TFB420.
Also, put a tilt back leg on the one built for solo use.
Feel free to PM me for any questions you might have.
Jim
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