Hi friends
I'll build a troels gravesen 3wc-12 (12 inch 3-way, here)
Troels seems to have his preferences (Baltic Birch), and also recommends MDF and black MDF...
His build guide is straight forward, baltic birch, damping stuff into it et voila.
OTOH, one could find plenty of enhancements (not speaking of experimental stuff like marble etc.):
bitumen glued to the cabinet
sandwiched constructions (but couldn't find details)
making the front-baffle in other materials...
I'm confident the standard build will be very good already...
Still, could it be improved?
What are your opinions, are improvements like above worth the hassle/what are the benefits?
Thanks for your time and opinion!
I'll build a troels gravesen 3wc-12 (12 inch 3-way, here)
Troels seems to have his preferences (Baltic Birch), and also recommends MDF and black MDF...
His build guide is straight forward, baltic birch, damping stuff into it et voila.
OTOH, one could find plenty of enhancements (not speaking of experimental stuff like marble etc.):
bitumen glued to the cabinet
sandwiched constructions (but couldn't find details)
making the front-baffle in other materials...
I'm confident the standard build will be very good already...
Still, could it be improved?
What are your opinions, are improvements like above worth the hassle/what are the benefits?
Thanks for your time and opinion!
While nobody seems interested, and me still researching, another Questions...
I'm tempted to use those Birch-plywood with phenolic resin coating. They're available with a smooth and a very rough side, used as "truck-loading floor"... Has anyone experimented with these, are they suitable/good/even improving things?
I'm tempted to use those Birch-plywood with phenolic resin coating. They're available with a smooth and a very rough side, used as "truck-loading floor"... Has anyone experimented with these, are they suitable/good/even improving things?
When it comes to speaker enclosures, the first and best thing to do is to use braces. Braces, braces, braces!
The next thing (in my opinion) is to use "sandwiches" of materials with dissimilar mass and stiffness, so their resonances / modes will show up at different frequencies (if one material/layer would like to go into resonance, the other will keep it tight). For example, I used aluminium sheets on the insides of the my OSMC enclosures (see photo in Fig. 6 here). I have also used ceramic tiles in the past.
The next thing (in my opinion) is to use "sandwiches" of materials with dissimilar mass and stiffness, so their resonances / modes will show up at different frequencies (if one material/layer would like to go into resonance, the other will keep it tight). For example, I used aluminium sheets on the insides of the my OSMC enclosures (see photo in Fig. 6 here). I have also used ceramic tiles in the past.
Yep, me too. B&W matrix type bracing with simple cheap mdf has worked best for me, even better than the hardly braced at all TG type construction with BB. I did a ton of objective testing years ago with test boxes and an accelerometer.
I only use expensive plys in PA/MI cabs that get moved about a lot. MDF heavily braced makes a heavy cab, but I seldom move mine once set up.
That reminds me of some measurements I did a while ago: https://www.diyaudio.com/community/threads/cabinet-bracing-measurements.284063/post-4554859
Cool, thank you both!
I was hoping for either troels or mbrennwa to chime in (although many others are just as wise!) 😊
The braces already are an integral part of the project (faital 3-wc, http://www.troelsgravesen.dk/Faital-3WC.htm), which in fact has some resembance to the OSMB imho:
http://www.troelsgravesen.dk/Faital-3WC/Faital-1261_1575.png
Nothing between the wood and the aluminium? (Like, alubutyl etc.)?
@mbrennwa I already ate the thread re:measurements, very helpful! Me, I got „concerned“ a bit by some other threads here, as well as the various theories about damping, resonances, stiffness etc… (those BBC-papers etc.), and tried to lure 😇 other builders into commenting about wether to use hdf etc., and eventually siebdruckplatten
(These are just plain birch-plywood, coated with rhat phenol-stuff, which gives it a very hard, very smooth surface, colors vary between a rusty red, a brownish orange and an almost black dark brown… quite nice I think!
I was hoping for either troels or mbrennwa to chime in (although many others are just as wise!) 😊
The braces already are an integral part of the project (faital 3-wc, http://www.troelsgravesen.dk/Faital-3WC.htm), which in fact has some resembance to the OSMB imho:
http://www.troelsgravesen.dk/Faital-3WC/Faital-1261_1575.png
Nothing between the wood and the aluminium? (Like, alubutyl etc.)?
@mbrennwa I already ate the thread re:measurements, very helpful! Me, I got „concerned“ a bit by some other threads here, as well as the various theories about damping, resonances, stiffness etc… (those BBC-papers etc.), and tried to lure 😇 other builders into commenting about wether to use hdf etc., and eventually siebdruckplatten
(These are just plain birch-plywood, coated with rhat phenol-stuff, which gives it a very hard, very smooth surface, colors vary between a rusty red, a brownish orange and an almost black dark brown… quite nice I think!
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Just because he does something a certain way, doesn't mean it can't be improved. I'm not much of a fan.
The Troels 3WC is similar size and uses the same woofer as the OSMC, but that's about it. There are a number of conceptual differences that have been discussed elsewhere (forgot which thread, but the search function may help).
The sandwich needs some ketchup, mustard or other
Ha! I‘ll go with BBQ
@Brett care to point me a direction as to how to improve?
An ordinary, good glue? (No [strike]audio grade[/strike] glue 🦆?)
Didn‘t mean to compare the two, I realized they‘re of different kinds despite the resemblance.
Ah. Thank you. You got me reading but not reading, sorry for that. I stubbornly hoped to read about magic stuff or something.
To apply solid basic engineering one needs to either know the basic engineering principles or to closely follow those that do. An engineer would not brace the hell out of everything as is common among speaker DIY folk. Instead they would apply stiffness, damping, mass and isolation where it will make a significant positive contribution to reducing the sound radiation from the cabinet and not where it will do little or even make it worse. If you look at how cabinets are designed by the engineers in the larger pro-audio manufacturers and even some of the more engineering orientated home audio manufacturers (need to be careful because many features in home audio speakers are created to support the marketing not the engineering) one can see the application of basic engineering.
To address the OP, yes the TG design could be improved in several ways in terms of engineering. The cabinet would benefit from damping, rearranging the bracing to primarily stiffen the baffle not the walls, isolating the midwoofer chamber,... Although this would improve the sound radiation from the cabinet it is likely to be a fairly minor change in comparison to most of the other decisions taken when designing the speaker. If you don't know how to improve it yourself and don't have access to reliable information on how to improve it then the wisest way forward is likely to build it as designed or adopt another design.
^^ Thanks, if I wanted a lecture on ME, I would have asked. As I have not shown what I actually use, you have no idea of what I know beyond recommending the basic B&W matrix approach over the minimalist TG one. I studied aeronautics before electronics. I've also done my own test enclosures and measured them in the past so I'm not coming from a woo woo audiophile position and very seldom divulge all the details of my designs. My testing (with accelerometers) showed smaller lattice/matrix braced external sections were much quieter than the relatively large areas in the as designed enclosure for this project. As I and most people don't have to design for the minimum material and weight budget, nor least construction complexity being elegantly efficient like an F1 driver shell is not necessary.
As for pro enclosures, I've seen inside a lot as I ran my own PA for decades and got to repair a lot of other people's gear. Much MI/PA gear is not much more than a hollow box with a minimum of bracing, so I hardly hold it out as being actually good in most instances. Some of the poly moulded enclosures are quite good, but they tend toward the matrix style as well internally and the more easily moulded curved shapes make them more rigid than is easily accomplished with a cuboid box in wood.
As for pro enclosures, I've seen inside a lot as I ran my own PA for decades and got to repair a lot of other people's gear. Much MI/PA gear is not much more than a hollow box with a minimum of bracing, so I hardly hold it out as being actually good in most instances. Some of the poly moulded enclosures are quite good, but they tend toward the matrix style as well internally and the more easily moulded curved shapes make them more rigid than is easily accomplished with a cuboid box in wood.
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Yes, bracing and also double front panels !
Here are the 120l cabinets I made for double 10" woofers.
I used Baltic Birch, stronger and lighter than MDF,
the sawdust from MDF is toxic, always ventilate when working with wood !
I tried to get good damping and cabinets that are not too heavy (relative 🙂), so you can still move them.
As damping material I used a layer of felt and on that basotect pyramids
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I will have the kit and drivers delivered today!
So these tips and informations come in justintime! Yes!
I will consider all this to decide what material I‘ll use, wether I‘ll sandwich and what sauce to use, what to do with the bracing (and the damping materials inbetween), and how to isolate the MD…
Since I have access to a professional workshop, doing a bit more extensive things ain’t no problem.
@danny_66 is this 19 mm BB ply?
So these tips and informations come in justintime! Yes!
I will consider all this to decide what material I‘ll use, wether I‘ll sandwich and what sauce to use, what to do with the bracing (and the damping materials inbetween), and how to isolate the MD…
Since I have access to a professional workshop, doing a bit more extensive things ain’t no problem.
@danny_66 is this 19 mm BB ply?
Ok. I had to take a bit offtime to digest, and read a bit more about bracing and damping, and found some funny methods...
I put it here for further reference. (Basically, I got my answers a few posts above).
But I'm really tempted to try those things. If one of you masters know this would yield bad results please say so!
Troels stated (somewhere on his website) that the cabinet could be made a stand-mount, adding some 36lt to his 70lt cabinet to get a bit more bass. (This can be found in the OSMC-thread, too). But then, somehow contradicting this, he says that if a design was altered, the whole thing would become a different product and would need a different crossover etc.
Can the volume be changed by making the box deeper (instead of higher), or is this a different beast?
(@mbrennwa — I know OSMC is a different beast even if there are similarities, and I do not intend to imitate it. It's just that many things are discussed in the OSMC-thread...)
I put it here for further reference. (Basically, I got my answers a few posts above).
But I'm really tempted to try those things. If one of you masters know this would yield bad results please say so!
- Earl Geddess had an interesting recommendation about decoupling braces (here) (KEF seems to go a similar way)
- and THIS is the thread about CLD ...
- Linkwitzlab has a fascinating way of mounting the woofer (here) (this one is ... I don't know ... )
Troels stated (somewhere on his website) that the cabinet could be made a stand-mount, adding some 36lt to his 70lt cabinet to get a bit more bass. (This can be found in the OSMC-thread, too). But then, somehow contradicting this, he says that if a design was altered, the whole thing would become a different product and would need a different crossover etc.
Can the volume be changed by making the box deeper (instead of higher), or is this a different beast?
(@mbrennwa — I know OSMC is a different beast even if there are similarities, and I do not intend to imitate it. It's just that many things are discussed in the OSMC-thread...)
Changing the box volume is certainly possible. This will change the bass tuning, and hence the impedance curve will be different. The "bass reflex" peaks and the dip in between the peaks will be centered at different frequencies. If the peaks were considered in the woofer xover, the xover will need to be adjusted accordingly. This is explained and discussed on the thread on the OSMC tower version.