Solid jarrah sounds excellent.It is a really dead sounding timber .I have used it laminated over MDF in larger speakers and as 100% solid in smaller speakers.It sounds much better than MDF or plywood to me.It is also great for turntable plinths and racks.Grado were also using it for some of their most expensive phono cartridges.It seems to have just the right density [medium-to high] and grain structure[short].It also looks beautiful.
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“Why Magico is made out of aluminum? Probably because it is cheap.”
Whether aluminum is cheap or not is besides the point. If you look at all the complexities in the internal bracings that are used and machining of all those pieces and the time and cost to assemble everything you’ll get a picture why they cost so much. It’s certainly hell of a lot easier (and cheaper) to run MDF boards through CNC machines and glue them up together, even when every other component, e.g., drivers, crossover parts, etc., are the same.
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Just make all walls 2.5 inches thick. Brace front to back with old (dry and shrunk) hardwood. And use granite glued onto the front. Voila! Success!!! |
Vinny
What..........you don't enjoy a little ringing???
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It helps to hear, literally, what is going on, by listening to the cabinet’s walls through a stethoscope, playing music and test tones. You find two things: - Flexing of the cabinet walls allows low bass to come through. Out in your room, this adds in phase to the direct sounds coming from your woofer, making the overall presentation warmer, and adding bass ’ambience’ below 80 Hz. The bass is less tight, less defined, of course. Probably makes the hifi sound ’better’ at soft volumes.
For low-bass flexing, braces help, granite helps, thick materials help, thin plywoods do not. Thin carbon fiber does not. Solid hardwood will split given time. Think here about maximizing panel ’stiffness’ or rigidity, not its ’strength’. Cement, concrete? Sure! FYI, paint the inside of wood cabinets with thinned-out wood glue-- as the surfaces of MDF and plywoods are porous, absorbing bass pressure whenever the woofer fires off.
- The other stethoscope discovery is that a cabinet lets voice range sounds, in the 200 to 300 Hz range, come right through. This makes for ’scratchy’ sounds in wood boxes and for ringing sounds in granite and metal. These vibrations do not come from the SPL inside the cabinet (unless there is a large, undamped (loud) standing wave inside). Those 200-300Hz vibrations come from the direct excitation of the cabinet material via the screws mounting ’that’ driver. When you loosen all its screws, all of a sudden, the walls go silent!
One fix is to use rubber-mounted screws, but this makes bass impacts ’rubbery’. KEF and others tried this in the 80’s, giving it up after sales tanked from all that loose bass. The driver could be mounted to a regular inner cabinet with a vibration-isolated cabinet wrapped around it. Unfortunately, this leaves those inner-cabinet vibrations undamped, which get back to the driver, making its cone vibrate (= noise).
When these tones get into the cabinet material via those screws, there is no way to damp them, and no way to brace against them, because they travel inside the cabinet material, not on the surface. If those screws cannot be rubber-isolated, the cabinet material needs to have ’high internal damping’, which is not a property of metal, cement, nor most woods. Cabinet thickness does not matter here, at least for making something to fit in a home.
For a home constructor, I recommend 3/4" Baltic birch plywood cabinets, or at least for its front panel, with braces inlaid 6-8 inches apart, center-to-center. But BB plywood is such a tough wood to work with and to make pretty! Two 1/2" BB layers glued up with Elmer’s Carpenter’s Glue made a front panel that was a bit more dead to those midrange tones getting into it from the screws, but not enough to justify the extra work. It made far more difference to put 1/4" wool felt on the front baffle to suck up the tweeter’s reflections before getting on with designing the tweeter’s crossover. Roy Johnson Green Mountain Audio |
