Is there any reason to not use real wood, as opposed to manufactured wood products? I strongly dis like plywood, and MDF/particle board, is not allowed on my property.
Shows why FRs are becomng popular, this list of 10 becomes 6 as items 2-6 become “FR driver”.
dave
I’m a cabinet/furniture maker by trade......engineered products are a lot more stable and easier to work with.
Certain woods lend themselves better to acoustical uses than others.....look at some instrument building sites for good info on that.
But any tight grained, stable, kiln dried wood would do.
Walnut, mahogany, cherry, maple etc......I know people make boxes from pine but I wouldn’t. If want a softer hardwood that’s easier to work try tulip poplar.....relatively cheap tight grained, and very easy to work.
Bob
Yes Dave, and you have been instrumental in introducing me to the advantages of FR units and what they are capable of when treated properly. Nevertheless, I will most often choose the multi-way systems when designing for me. In gaining the understanding of the FR, I now like to start a design it around an FR unit and fill in the top and bottom. 🙂
Thanks Cal pretty much what I expected actually. I have a backlog of conventional speakers to refurb and move out then a wide band midrange maybe waveguided is next, with top and bottom support. Something like Adason's little mtm frinstance.
I think you should use whatever materials you like, or what are available to you.
What has not been mentioned is that irrespective of design or materials used, all speaker cabinets will colourise the sound from a driver to some degree. The question is: what kind of colourisation do you like or want? And instead of of the scattergun approach of trying everything and achieving nothing, it might be better to focus on one type of design and driver, and spend maybe a couple of years trying everything possible before finally calling it a day. You could spend a year building a loudspeaker, and then another year evaluating your achievement - which is where I am now with what I am doing.
Yes, choice of materials and understanding their properties is of vital importance, but of greater significance are the aims and objectives of eventual achievement.
ToS
A knock test is good and simple but it requires the knock to be performed at several locations if all the relevant low frequency modes are to be excited and measured. The frequencies of these modes won't change with knock location (unless you knock too hard and create a nonlinear deformation) but their magnitude will and so some that are too weakly driven to be seen at one knock location will be more strongly driven and visible at another. It won't provide what we would ideally like to see which is the magnitudes of the modes with the speakers driving the cabinet which requires a much more involved and expensive test. But the frequency and damping of the lowest modes is very useful quantitative information.
Your results however seem strange in terms of physics. If the plot on the left is the unbraced cabinet and the one on the right is the braced cabinet then conventional bracing will make a cabinet stiffer and raise the frequencies of the lowest resonances. The frequency of the resonances appears to have gone down which one gets from adding mass not stiffness. So are your braces conventional stiffening ones or perhaps something else?
PS If they are stiffening ones you wouldn't expect the SPL to change significantly just go up in frequency. Damping reduces the magnitude of resonances. Joints introduce damping and so if your braces are not rigidly attached that could explain the reduction in frequency due to mass and a possible reduction in level due to damping but this would need the shape of the resonance to be accurate.
By introducing braces you have changed the set of mode shapes and by considering only a single knock location are no longer performing a like with like comparison. It would be preferable to reveal all the modes by knocking at set of locations over the speaker and then compare the full set. For example, if you are knocking at a location where the new bracing has significantly increased the stiffness that would greatly reduce the amount energy put into the speaker by the impulse and hence the magnitudes in your plot. This reduction would not necessarily be seen when the cabinet is vibrated by the drivers at different locations. I suspect this may have been misinterpreted in your plots.
Whatever, this type of thing when done a bit more thoroughly is solid evidence based engineering of a kind that is pretty rare when it comes to DIY speaker cabinets. Good stuff.
Well I must say I certainly appreciate your assistance with my Large Advents. Without you, I might not know what all the fuss is about. That will not be forgotten.
There ya go. Thanx for the input. Being an "upstart luthier" I'm familiar with the acoustical characteristics of various woods. I've found that water soaked, air dried, and charred, makes for a very clean sound. the soaking removes the sap, which can form in pockets causing varying denseties accross the board, air dry allows the wood to age, and normalize. Charring, seals the grain, and hardens the surface.
I guess, with mdf, you don't need to go through that process, as it's already pretty uniform.
Shorty,
Keep in mind that as a Luthier, you are looking to incorporate characteristics of the materials, while as a loudspeaker designer, you are looking to eliminate those very same characteristics. That is why concrete makes a sonically good speaker cabinet but is a sonofagun for a violin.
Keep in mind that as a Luthier, you are looking to incorporate characteristics of the materials, while as a loudspeaker designer, you are looking to eliminate those very same characteristics. That is why concrete makes a sonically good speaker cabinet but is a sonofagun for a violin.
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I live in an area that used to log old growth cypress in the 1800’s
They moved the logs along the rivers in ‘rafts’ many of these logs sank along the way because some logs were so dense.
They now dive these logs air dry them and saw them into lumber, it’s called sinker cypress.....although expensive ($5-6 bf ) I think it would make some awesome speaker box’s.
I would go with kiln dried though because even this cypress still moves a little....I’m working on building my own kiln drier from a 40’ shipping container.
Bob
They moved the logs along the rivers in ‘rafts’ many of these logs sank along the way because some logs were so dense.
They now dive these logs air dry them and saw them into lumber, it’s called sinker cypress.....although expensive ($5-6 bf ) I think it would make some awesome speaker box’s.
I would go with kiln dried though because even this cypress still moves a little....I’m working on building my own kiln drier from a 40’ shipping container.
Bob
I made some chip board speakers for my mobile disco in early 80's.
Got caught out one night in the rain and despite not being in the rain for long they later started swelling up. I have used plywood since.
Got caught out one night in the rain and despite not being in the rain for long they later started swelling up. I have used plywood since.
PHffffftttttt. That is the sound of the opening of a can of worms. Once out of the can, it is impossible to get them back in.
The mdf vs plywood debate in that video is based on a constant weight approach, allowing for thicker plywood than mdf. It is pretty much the opposite approach of what we witness most of the time on this forum, where thicker mdf is used, weight being considered mostly irrelevant for hifi.
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