soongsc said:
In the case of the materials being discussed, there isn't enough of a significant difference between them to evaluate, as most (if not all) of the major speaker manufacturers have already known for a LONG time.
Material choice is more about novelty, setting your product apart from the others and claiming this makes it superior.
Marketing, period.
MJL21193 said:
I partly agree...there are much more important issues to be solved in speaker design
diy cabinet designing has been going on fore a number of years...it still puzzles me why people keep thinking they can make a superiour speaker by making peculiar box design, while at the same time completely ignoring more important issues
A genuine cabinet design doesnt make a good speaker on its own
I will even take it so far as to claim that a well balanced driver/xo/frontbaffle design will still sound good with even the most crappy box design
I do have some doubts about that. Good panel damping is just as important as reduction enclosure internal standing waves. But as dave had mentioned, cost is usually a limiting factor. Even when I do driver testing on an open baffle, I do notice panel resonances in the CSDs, and I can see them change if I do some damping to the baffle.MJL21193 said:
soongsc said:
That's just it: good panel damping. As shown above, the raw materials have nearly identical resonant frequencies. To improve this, you brace to minimize vibration and you damp to reduce the decay time.
All panels resonate. It's up to the designer how much he wants to control it.
But when you start off with the attitude that you are using a superior product, and can cut a few corners, then you are ahead of the game. You have yourself convinced you are building a better box. This isn't the case in reality though.
MJL21193 said:
If that is true, it is clear that the multiply (plywood) used in these tests is better damped than the MDF they used. This is consistent with what Ron said about losing energy across material impedance changes.
Bracing pushes resonance frequency up. The energy available to excite a resonance is inversly proportional to the square of the frequency, so the higher the panel resonance the less likely it will get excited. One has to be careful about adding additional damping, as it adds mass without adding stiffness, lowering panel resonance.
As a designer, my goal is to have a box that dissapears sonically.
dave
planet10 said:
There is no evidence of the multiple veneer layers acting that way though. It certainly doesn't show in the "high rez" tests you pointed to above, as you can plainly see that the decay time for BB plywood is longer.
The material acts as one thick homogeneous sheet, as there is no loss between layers and they are so thin, they could only disrupt very high frequencies.
Bracing strategies work for ALL materials, not just BB plywood. Use the same construction methods for both materials and you have the same results.
The first designs of the Summa on top of being composite fiberglass with 2" thick baffle etc. they had Constrained layer damping. They were very very and very dead. About a year later I deleted the CLD for cost reasons and I can't say as I noticed any difference at all (either audible or measureable) - small crossover changes make big audible differences - large enclosure changes don't seem to make a huge difference - or I have already surpressed them to the point where they are inaudible.
Now I am deleting the composite enclosure and going to pure MDF. I'll see if this makes any notable difference. I'm guessing that it won't.
So here I tend to agree with 1) the need to determine the level of the effect, 2) to get some real data and 3) to quite arguing about things that don't make a difference and worry about those things that do. As far as any data that I have says - the enclosure is grossley overrated as a source of poor sound quality. But then again, most of my enclosures are on the robust side and really cheap of flimsy enclosures may not yield the same results. But clearly there is a point at which this too does not matter and going further is just a waste of cost and time.
Now I am deleting the composite enclosure and going to pure MDF. I'll see if this makes any notable difference. I'm guessing that it won't.
So here I tend to agree with 1) the need to determine the level of the effect, 2) to get some real data and 3) to quite arguing about things that don't make a difference and worry about those things that do. As far as any data that I have says - the enclosure is grossley overrated as a source of poor sound quality. But then again, most of my enclosures are on the robust side and really cheap of flimsy enclosures may not yield the same results. But clearly there is a point at which this too does not matter and going further is just a waste of cost and time.
the above tests are very interesting
nevertheless their scope is limited
why only "18 mm MDF"? that is not much
why not "25 mm MDF" or "50 mm MDF"
I use 50 mm MDF
Would 18 mm plywood be better the 50 mm MDF? Would be 50 mm MDF worse than "plywood plus concrete plus glass wool" etc.
Are there any data?
Would it be AUDIBLY worse?
Does anybody need anything more then 50 mm MDF?
etc.
best,
graaf
planet10 said:
With age comes wisdom.
Dave, you try to get more or better results from your speakers and cabs and that is commendable. In your search, you have obviously formed some strong opinions about certain things. There is nothing wrong with convictions, but to discourage the use of a perfectly fine speaker box material just because you feel it gives unworthy results is not right.
You offer not proof of this other than your subjective opinion and the testimonials of others (clearly within your circle of influence).
Too many here believe it, when it comes from an authority like yourself.
MJL21193 said:
I understand. We can compare and come to conclusion that e.g. 18 mm plywood is better or worse than 18 mm MDF. Ok.
But what is the point of this comparison?
I know people that use 18 mm plywood but all people I know that use MDF use at leat 25 mm MDF, AT LEAST.
planet10 said:
but what is not fine with 50 mm MDF? not 18 mm but 3x18 mm
What is wrong with it?
Why should I use 18 mm plywood instead?
best,
graaf
MJL21193 said:
The wholw point of these forums is to share experience.
And you have no proof (and none could ever be offered -- a discussion of that pont in the thread this was split off from) that MDF is better or as good.
Many i have never met hold the same opinion as me... my feelings on boxes did not come about in isolation.
dave
I have the speaker at homeplanet10 said:
and why shipping? It is DIY, not industry. Fortunaltely I don't need to ship my DIY
planet10 said:
plywood stores energy too, and it wouldn't be easier to lift (or to ship)
it is not an argument for the sake of an argument - I REALLY would like to know what would be the advantage of using 2x18 plywood with bracing over 3x18 MDF
because I would like to have better DIY speakers
give me the data please
best,
graaf
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