AKA industrial or cabinet grade particleboard, which for a given thickness has somewhat less stiffness [lower MOE] than MDF [~450 k Vs 527 k/ in^2] , ergo just a fraction of what BB or similar vo void plywoods have [~1.8 m/in^2], so while HDF is a step up from MDF [in general] as I previously noted, its stiffness is a step down, ergo must either be [much] thicker than the others or the driver + acoustic loading must be more under-damped [higher Q [sysQ]] or its intended BW limited to above its natural Fbox to benefit.
GM
GM
It's all particle board with the main difference being chip size and more importantly, the type of binder used, i.e. place a piece of PB, MDF, HDF and for reference, plywood, in water and the PB and MDF quickly begins absorbing it while the HDF will float indefinitely and the plywood eventually de-laminates, so you may want to get a scrap of HDF/whatever and test for what it is before committing it to a project.
GM
GM
Medite is one of those delightfully confusing terms that is the name of an international corporation, registered trademark brand name for a product manufactured by Sierra Pine Company in California and Oregon, and a generic term for (generally) medium density fiberboards.
Most of the major players in the sheet goods business offer a wide range of "MDF / HDF" - Sierra alone has 7 different products in their MDF catalog, and 8 particleboards - each engineered for specific range of applications. They're not all created equal in terms of density, particulate / fibre size, type of resins and tempering of finished faces resulting from the heat and pressure of thermosetting and finish sanding processes. For example some of the latest generation of Ultra-lites are porous enough that the thinner ones (3/8" & 1/4" ) leak some of the vacuum pressure of the bottom mounted suction cups on our CNC. Great for lightweight hinged and sliding cabinet doors, and speaker grille frames, but I'm not sure I'd use them for enclosures.
Most of the major players in the sheet goods business offer a wide range of "MDF / HDF" - Sierra alone has 7 different products in their MDF catalog, and 8 particleboards - each engineered for specific range of applications. They're not all created equal in terms of density, particulate / fibre size, type of resins and tempering of finished faces resulting from the heat and pressure of thermosetting and finish sanding processes. For example some of the latest generation of Ultra-lites are porous enough that the thinner ones (3/8" & 1/4" ) leak some of the vacuum pressure of the bottom mounted suction cups on our CNC. Great for lightweight hinged and sliding cabinet doors, and speaker grille frames, but I'm not sure I'd use them for enclosures.
A 'sign of the times' I guess as back when I last spec'd such materials ['94] the list to manufacturers [at least corporate] were much larger, not to mention one could spec a special order, though don't recall Sierra Pine. We ordered mostly from Ga. Pacific, Weyerhaeuser.
Regardless, AFAIK what I listed are for what one is likely to be available to the average consumer in the USA, which in retrospect I should have noted. No clue about elsewhere in the world.
GM
The MEDEX line from Sierra Pine is stiff for MDF at 600,000 psi.
http://www.sierrapine.com/media/module/content_item/Medex_Spec_Sheet.pdf
I think all most everyone posting to this thread has NO IDEA WHAT HDF IS!
HDF was invented by William H. Mason...AKA Masonite...Mason was a protégé of Thomas Edison. https://en.wikipedia.org/wiki/Masonite
As I posted in the VERY FIRST post in this thread... Joe Rasmussen recommends HDF as the "biggest upgrade" to the cabinet for his Elsinores build when compared to a Dynaudio build using HDF as the "Elite" upgrade since that is the only difference between the speaker I listed in the FIRST POST!!
So....according to a lot of people in the field a lot more qualified than I am, they use HDF as a superior cabinet material to build speaker cabinets from!
All of ACI's speakers were built from 1" HDF and they all had rave reviews!!! I own a pair of ACI's Sapphire III's
So in fact it is not really "my opinion" HDF is the best material since that opinion is held by people in the industry who are far more qualified to know what's the best material than me!
HDF was invented by William H. Mason...AKA Masonite...Mason was a protégé of Thomas Edison. https://en.wikipedia.org/wiki/Masonite
As I posted in the VERY FIRST post in this thread... Joe Rasmussen recommends HDF as the "biggest upgrade" to the cabinet for his Elsinores build when compared to a Dynaudio build using HDF as the "Elite" upgrade since that is the only difference between the speaker I listed in the FIRST POST!!
So....according to a lot of people in the field a lot more qualified than I am, they use HDF as a superior cabinet material to build speaker cabinets from!
All of ACI's speakers were built from 1" HDF and they all had rave reviews!!! I own a pair of ACI's Sapphire III's
So in fact it is not really "my opinion" HDF is the best material since that opinion is held by people in the industry who are far more qualified to know what's the best material than me!
OMG...so what Joe actually says makes no difference?! What a joke...you guys are starting to **** me off now...here I'll re-quote it again since nobody actually read what I posted in the FIRST POST!!!!!!!
The following is a quote from Joe...
"But the thing that I believe would improve the box most is the most simple (and yet difficult at the same time), take a look at the newer Dynaudio designs, that baffle of theirs made of high density fibre board. I have heard a pair of Lenehan ML-1 speakers in both standard and 'Signature' versions and this was the only difference. Make the front part of the box structure out of this material and I believe the improvement would be greater than anything I have covered so far, no kidding!"
Of course it makes a difference. In Oz HDF is probably the best material available so a logical choice. Quality plywood is probably better. Certainly in my experience having used both.
dave
re:"it is VERY hard to get good plywood in Australia" - not really, but it's darned expensive, you need to go a specialist supplier like Mr Plywood (Tassie Hoop pine is good). The stuff at Masters is complete cr@p, I often use the Bunnings 18mm ply, which isn't completely void free, but it's convenient, you can usually get some 1200x600 sheets with a good face on them of you sort through the pile, & they fit into my small Honda....
IMHO Australia has always been technology-centric, but there are also some traditional views that amount to making do with what one has that limit the availability of some newer products to a demonstrated market desire for them. I find it often helps to wander outside the field.
Plus we're so far from everyone else that postage is a killer.
Plus we're so far from everyone else that postage is a killer.
Is this a quality of quartz? I assume it isn't related to grain shape as sand seems to also be used in suspension.
From what I've read it's the grains and the grain size. As the sound had to pass from grain to grain, it losses energy.
Sound going thru stacks of different media would also be attenuated, because in each different material the speed of sound changes. The change takes energy. Probably converted to heat? Sand will have 1000s of poor quality transitions, causing large energy losses.
There is probably some good work published on the subject that will confirm or deny this.
Sound going thru stacks of different media would also be attenuated, because in each different material the speed of sound changes. The change takes energy. Probably converted to heat? Sand will have 1000s of poor quality transitions, causing large energy losses.
There is probably some good work published on the subject that will confirm or deny this.
A case based on the properties of HDF and what is needed for speaker cabinets would have been a lot more persuasive. Appealing to what prominent DIYers use and what the manufacturers of highly rated speakers use is an argument against HDF not an argument for it because it is rarely used by either.
Sorry, just read this thread starting at the beginning, but this isn't the way I see it. At all.
The reason is that the main mechanism which makes a loudspeaker wall vibrate is not so much the fluctating pressure differential between the two sides of the wall. The pressure generated inside an enclosure is rather small.
The dominant mechanism are the reaction forces generated when the cone assembly is forced to move. A heavy enclosure will move less under the influence of these reaction forces than a lighter one, a=F/m.
The fluctating pressure differential generates forces which can be contained by having stiff or cleverly shaped loudspeaker walls. The reaction forces cannot be contained, they can only be minimized by having heavy walls, or dissipated by for example a lossy flexible mounting of drivers. The latter solution has its own issues.
I did quite a bit of research using an accelerometer attached to loudspeaker panels of different materials, so this is how I came to this understanding. The device I have is sensitive enough to pick up on the back panel the movements induced by a tweeter mounted on the front.
Now on to the rest of the thread, and I am convinced someone else will have made this argument before me.
Last edited:
At low frequencies the forces due to stiffness will dominate, at high frequencies the forces due to mass will dominate and in between will be a range with low order resonances the size of which is determined by the forces due to damping. There are one or two other bits of physics that may or may not become relevant like the speed of bending waves in the material but normally designing a speaker cabinet follows from which of these regions the passband of the driver lies and what it takes to shift in a favourable direction.
For example, a woofer in a simple wooden box would normally have it's passband in the top part of the stiffness controlled region and the lowest few resonances. Stiffening the box while adding little mass will move the resonances above the passband of the woofer while lowering the magnitude of the deflection at frequencies below the resonances. This looks like a good move. Adding mass will the lower the resonant frequencies increasing their number in the passband while do nothing for the size of the cabinet deflection at frequencies below this. This does not look like a good move.
If inertia is dominant then adding mass will very likely reduce the deflection of the cabinet walls but if it is relatively unimportant then there is a fair chance it will make matters worse like in the example above.
A soft spring between the driver and the cabinet will largely prevent the driver reaction force from vibrating the cabinet. It does not dissipate energy.
