duncan_mclaud
New Member
Hi,bijinmb! Can u send a crossover scheme pls?
2 Way Bookshelf (Vifa, Peerless) - Build
- Thread starter bijinmb
- Start date
rajesh srinivas
Active Member
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hi bijinmb
Like to know at what price did you buy these 8x4 green ply exterior grade panelmax mdf sheets??
Do you recommend only greenply brand,or any other brand i can buy for my diy box build,i think hdf can also be used but for a heavy price???
thanks
r/s
saikatbiswas82
Well-Known Member
I purchased unbranded MDF @ Rs. 45/- per sqft. It was more than enough for my sealed sub IMHO.
rajesh srinivas
Active Member
In unbranded the density of wood fibre used will be less compared to branded ones,even the thickness in mm will be not the same as required.if we order for 18mm the actual thickness will be 1 to 2 mm less,that will deteriorate quality of the box.
I enquired Greenply exterior mdf board at my place a 4x8 cost rs. 88/- per square feet.another make "Tesa Action" cost 76/- per sq.ft.
Any idea for box finishing wheather to go for veneer or vinyl or laminates,which is better,according to me veneer costs more but looks great,vinyl also not bad but sanding has to be done properly for smooth finish,laminates the last resort costs low looks not that great.
i require one that can bend to cover the radius we give for edges as done by bijinmb.
thanks
rajesh
saikatbiswas82
Well-Known Member
Are you sure that the density is different? How did you measure the difference in density between branded and a non-branded mdf boards? Did you measure the weight?
Are you sure that greenply sells 19mm mdf only and they are not at all 17mm?
I'm just curious to know.
Sent from my Nexus 5 using Tapatalk
keith_correa
Well-Known Member
Why would one need to sand vinyl?
rajesh srinivas
Active Member
i enquired few shops thats what the shop owners say regarding the density the quality has to be low grade,thats why they cost low and 100% they cheat in the thickness of material.
Green ply sells 17mm and 18mm then comes 25mm,but the thickness will be
accurate and assured one can check with vernier caliper.
sanding the cabinet surface i mean is very much essentiai for a perfectly smooth finish esp. for application of vinyl sheets or otherwise they'll show through.
r/s.
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Great build. Thanks for the pics, they really help. 
I thought I'll chip in with a few points about the physical design and construction.
These are just my thoughts. There are a thousand different ways to do the same thing in DIY.
It's always great to see how much effort you put in for your builds and how well you finish your enclosures. :clapping: I really love well-finished DIY, and I love your dedication to good finishing. Commercial speaker manufacturers apparently spend upto 60% of their costs on finishing of enclosures, I'd read somewhere.
I thought I'll chip in with a few points about the physical design and construction.
- For your next design, I suggest moving the tweeter much closer to the midbass. We strive to get to ideal point sources, and tweeter-midbass distances do make a difference to the coherence of the sound, specially for critical nearfield listening. In fact, the midbass units you used have straight-cut flanges to allow close placement of the adjacent driver.
- Don't put the tweeter on the vertical centre-line of your front baffle -- offset it to one side by at least an inch or so. The theory says that the distances from the two edges should be 1.6:1 or some such ratio. Offsetting it helps even out the SPL by distributing out edge reflections across a wider range of frequencies.
- The largest panels in this enclosure are the side panels. In other words, spurious vibrations are most likely to emanate from them. I would suggest horizontal braces, not vertical, for such enclosures, so that the side walls are properly locked down and stiffened. (If I understood your design right, you have only one brace, which is vertical.)
- Just my preference, but I go with 25mm MDF. I don't see what is to be gained by using thinner, considering how much of a struggle it is to build inert enclosures.
- I suggest not using MDF for braces. Use 20mm (or 18mm, depending on the brand) ordinary commercial ply. And make sure you put a 2" wood screw through the outer wall into the brace plywood edgewise every 4-6 inches, in addition to Araldite. This forces the brace to lock down on the outer wall tightly. My carpenter missed the screws for my Darbari lower enclosure, and I immediately heard the effect and had to force him to put them in.
- Make the grill frame from thinner material if possible. I tried making a grill frame once, using stainless steel rods maybe 3-4mm diameter. It worked out really well, because it's strong and very thin. Any metalwork shop which makes stainless steel drawers and cages for kitchens will be able to make them for you.
- I use double-thickness for the front baffle, since that's the most important to get inert, by far. In other words, I use 2 sheets of 25mm MDF stuck together to give me a 50mm front baffle.
- For your next build, don't bother with rounding out the edges of the cutouts in your braces. Sharp edges there shouldn't impact the sound audibly. You have taken enormous pains to do a finely crafted job -- maybe this will save you a bit of labour. Sharp edges versus rounded edges make an impact on the sound only for directly radiating sound which is in front of you and radiating towards you, and this too impacts only high frequencies. If these edges are inside an enclosure, their impact won't be audible outside the box. (Bevelling the rear opening of the midbass cutout is a different matter -- that bevelling (not rounding-out) is needed to avoid standing waves which otherwise may form in the short cylindrical tunnel behind the speaker cone.)
- You've done lovely rounding of the baffle edges, which is the textbook prescription to do. But I am now beginning to feel that just bevelling them 45-degrees will probably give almost identical results acoustically, and are sometimes easier to build -- you don't even need to run a router along the edges. May save you a bit of labour.
These are just my thoughts. There are a thousand different ways to do the same thing in DIY.
It's always great to see how much effort you put in for your builds and how well you finish your enclosures. :clapping: I really love well-finished DIY, and I love your dedication to good finishing. Commercial speaker manufacturers apparently spend upto 60% of their costs on finishing of enclosures, I'd read somewhere.
GeorgeO
Well-Known Member
Saikat
Lower grade i.e. cheaper MDF is fairly easy to identify-it weighs less, for similar spec material.
Lower grade i.e. cheaper MDF is fairly easy to identify-it weighs less, for similar spec material.
saikatbiswas82
Well-Known Member
rajesh srinivas
Active Member
yes GeorgeO
you are right,even i mentioned in my earlier post that the density and quantity or even quality of wood fibre used will be less compared to branded ones.
Always better to go for branded ones if possible physically weigh them and always check the thickness of the sheet as per the specs.
@tcpip, all the points who have mentioned have given me so much of additional imformation in doing my diy box build,in regard to your suggestion i would like to clear my following doubts.
-
using 25mm mdf will be too heavy,why cant we use 18mm with sufficient bracing,its like 25mm with no bracing = 18mm with sufficient bracing.
-
why cant we use mdf as bracing since the ultimate goal is to see that all the four corner of box are linked together in turn to make the box tight,whats the advantage in using ply as bracing,and disadvantage of using mdf
Your suggestion of using screws for every 4in is nice,but instead of Araldite i will be using fevicol.
-
Any pics or video of doing the stainless steel rods as a frame will be great.
-
As i earlier said i will be using 18mm 2 sheets for front baffle as many do,using 25mm as double has any benefits to quality of sound.
-
For your next build, don't bother with rounding out the edges of the cutouts in your braces. Sharp edges there shouldn't impact the sound audibly. You have taken enormous pains to do a finely crafted job -- maybe this will save you a bit of labour. Sharp edges versus rounded edges make an impact on the sound only for directly radiating sound which is in front of you and radiating towards you, and this too impacts only high frequencies. If these edges are inside an enclosure, their impact won't be audible outside the box. (Bevelling the rear opening of the midbass cutout is a different matter -- that bevelling (not rounding-out) is needed to avoid standing waves which otherwise may form in the short cylindrical tunnel behind the speaker cone.)
great advice,but how do you do the bevelling for the rear being spherical for front baffle doing the bevelling at 45-degree is not a problem since i own a circular saw as well a router
thanks
rajesh
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You are right. 25mm MDF bookshelves almost need no bracing at all. With 18mm, you can definitely get similar inert walls with good bracing. It's just that it's cheaper (in all aspects, time, effort, money) to do 25mm and eliminate or reduce the bracing. I've never bothered about reducing weight -- I find that heavier speakers sit on their stands better, and this alone improves sound. But if you want to optimise weight, go for 18mm and bracing by all means.
What you need from walls is different from what you need from braces. The walls need to be inert, dull (in the sense of vibrations) and "unwilling" to vibrate. What you need from bracings is rigidity -- they shouldn't flex. Rarely will you get both these properties in a single material. 12mm or thicker glass sheet will give you both (for audio frequencies), but glass is damn difficult to work with.
Therefore, 20mm ply being much more rigid than MDF, I feel you should use it for braces. In fact, you can build entire speakers using 20mm ply -- good quality commercial ply available in any good shop. My first speakers, the Asawari 1, were made using ply entirely. (I used EVA sheets to damp the walls, plus did extensive bracing, again with plywood.)
No, Fevicol doesn't have 1/10th the strength of Araldite, and is useless for areas which will face tremendous vibrations. You have to use Araldite there. Fevicol is only useful for sticking large surfaces, e.g. sticking laminate or veneer on plywood. It is of no use where the contact area is small, e.g. where the edges of your bracing come into contact with the walls of your enclosure.
Sorry, I don't have any. I dumped the steel frames too, when I dumped the speakers -- that was an aborted project.
Front baffles are the most susceptible to vibrations, because your drivers are directly coupled to them. Therefore making them deader is more difficult than making dead side walls. Therefore, I try to play safe and do 25mm x 2. My logic is: if I'm taking all this trouble to design, measure and build my own speakers, I should not scrimp on a few mm of material to risk a drop in quality, specially when it's not snake oil -- it's not a case of cryogenically treated cables. :lol:
Rouded-off bevelling and 45-degree bevelling are both done the same way -- choose the right router bit and use a router.
Incidentally, I do 45-degree bevelling for the inner side of the front baffle cutouts -- I don't believe there's anything to be gained from doing rounding-off. In fact, there may be some small thing to lose. See this page from the Darbari pages to get a clearer idea of the router bit I use and the way I do the bevelling.
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tcpip
a couple of things i have noticed in my limited experience
Plywood doesnt work too well for my for braces simply because ply is multiple layers pressed on so it does not take to well with screws nails or even glue applied along the thickness
Also plywood has a very differnt tonality when used for the full box
(that i hope you would concurr)
About thickness of wood used
this is a highly grey area with BBC designs instructing smaller wall thickness etc since
the speaker is actually part of the sound you hear
you can never ask it to be absolutely inert ( unless you are going full open baffle)
so how the box reacts vis a vis the driver is differnt
and thatis where design testing and measurements play their role
Commerical manufacturers dont use thin walls JUST to save costs and make speakers light
the tabaqs infact sound better unbraced and thin walled
So though your thinking is theoretically correct about building an absolutely rigid enclosure ( vibrations free ) its not really the case that that works out
BOX interplay is always a given
ATC and PMC infact factor that in in their designs
all the technical pieces of advice
though are absolutely spot on
a couple of things i have noticed in my limited experience
Plywood doesnt work too well for my for braces simply because ply is multiple layers pressed on so it does not take to well with screws nails or even glue applied along the thickness
Also plywood has a very differnt tonality when used for the full box
(that i hope you would concurr)
About thickness of wood used
this is a highly grey area with BBC designs instructing smaller wall thickness etc since
the speaker is actually part of the sound you hear
you can never ask it to be absolutely inert ( unless you are going full open baffle)
so how the box reacts vis a vis the driver is differnt
and thatis where design testing and measurements play their role
Commerical manufacturers dont use thin walls JUST to save costs and make speakers light
the tabaqs infact sound better unbraced and thin walled
So though your thinking is theoretically correct about building an absolutely rigid enclosure ( vibrations free ) its not really the case that that works out
BOX interplay is always a given
ATC and PMC infact factor that in in their designs
all the technical pieces of advice
though are absolutely spot on
In general, this is true. Plywood will split easily if you insert a screw edgewise. But if you pour Araldite first into the hole, then put in the screw, I am willing to bet that it'll stay that way.
If your speaker's final sound is being affected by the tonality of the material for the walls, then the walls are not dead enough. You either need to change the material, or add bracing, or increase damping linings, or some such thing.
This is not a grey area in my book, or in Neil Patel's book (Avalon speakers), or in Rockport (the famous Rockport Antares) or the Watt Puppy, etc. Most speaker designers will agree that their aim is to make inert enclosures, and various designers use various techniques to achieve this. All speakers above a certain price point actually achieve this to such an extent that the enclosure's influence on the sound is, for all practical purposes, inaudible.
BBC speakers have a different approach. I don't buy that approach, neither do a lot of talented designers who are far more talented than me. Therefore, yes, people like me always ask for the enclosure to be absolutely inert, and we are able to reach surprisingly high levels of inertness with local Indian materials and carpenters. Some designers (a minority, without a doubt) think otherwise. It's their choice. I don't agree with their choice.
MOST commercial manufacturers use thin walls ONLY to save costs. Some, very few manufacturers use thin walls and still build very expensive speakers. They exist, but they are a very small minority. I am asking you to do a reality check -- check the prices of speakers which have thin(ish), resonant, "live" enclosures. Check how many of them are really expensive. I remember only one in my limited experience: the very expensive Dunlavy speakers.
Ask yourself: how many speaker designers who are able to charge, and get paid, more than, say, $10,000 for a pair of speakers, are using thin walls and "live" enclosures? If you find that most of the thin-wall models are also (relatively) inexpensive, there's your answer.
One of the most important lessons I've learned while interacting with the DIY audio community is this: your "better" may not be the same as my "better". In fact, it's surprising how few DIY audio enthusiasts say "For me, more accurate is better." For most people, it's a very subjective idea which they seek, when they think of "better". I have no issue with such enthusiasts. I respect them 100%.
However, if I have to engage in a discussion with anyone about equipment quality, then I will only do so if "better" can mean "transparent", "uncoloured", "accurate". If you use my definition of "better", then thin-wall boxes don't work. I am so sure of this that my mind is completely closed on this matter.
For instance, I absolutely love the ODAC and O2 for my IEMs. A lot of people on various forums say that they prefer other DACs or headphone amps over this stack. But I've yet to see anyone who agrees to my definition of "better" calling the O2+ODAC mediocre. I have now understood that the O2+ODAC is absolutely top-of-the-line equipment, but only for those who relentlessly seek accuracy and lack of coloration.
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rajesh srinivas
Active Member
Great build. Thanks for the pics, they really help.
I thought I'll chip in with a few points about the physical design and construction.
- For your next design, I suggest moving the tweeter much closer to the midbass. We strive to get to ideal point sources, and tweeter-midbass distances do make a difference to the coherence of the sound, specially for critical nearfield listening. In fact, the midbass units you used have straight-cut flanges to allow close placement of the adjacent driver.
- Don't put the tweeter on the vertical centre-line of your front baffle -- offset it to one side by at least an inch or so. The theory says that the distances from the two edges should be 1.6:1 or some such ratio. Offsetting it helps even out the SPL by distributing out edge reflections across a wider range of frequencies.
- The largest panels in this enclosure are the side panels. In other words, spurious vibrations are most likely to emanate from them. I would suggest horizontal braces, not vertical, for such enclosures, so that the side walls are properly locked down and stiffened. (If I understood your design right, you have only one brace, which is vertical.)
- Just my preference, but I go with 25mm MDF. I don't see what is to be gained by using thinner, considering how much of a struggle it is to build inert enclosures.
- I suggest not using MDF for braces. Use 20mm (or 18mm, depending on the brand) ordinary commercial ply. And make sure you put a 2" wood screw through the outer wall into the brace plywood edgewise every 4-6 inches, in addition to Araldite. This forces the brace to lock down on the outer wall tightly. My carpenter missed the screws for my Darbari lower enclosure, and I immediately heard the effect and had to force him to put them in.
- Make the grill frame from thinner material if possible. I tried making a grill frame once, using stainless steel rods maybe 3-4mm diameter. It worked out really well, because it's strong and very thin. Any metalwork shop which makes stainless steel drawers and cages for kitchens will be able to make them for you.
- I use double-thickness for the front baffle, since that's the most important to get inert, by far. In other words, I use 2 sheets of 25mm MDF stuck together to give me a 50mm front baffle.
- For your next build, don't bother with rounding out the edges of the cutouts in your braces. Sharp edges there shouldn't impact the sound audibly. You have taken enormous pains to do a finely crafted job -- maybe this will save you a bit of labour.
- You've done lovely rounding of the baffle edges, which is the textbook prescription to do. But I am now beginning to feel that just bevelling them 45-degrees will probably give almost identical results acoustically, and are sometimes easier to build -- you don't even need to run a router along the edges. May save you a bit of labour.
These are just my thoughts. There are a thousand different ways to do the same thing in DIY.
It's always great to see how much effort you put in for your builds and how well you finish your enclosures. :clapping: I really love well-finished DIY, and I love your dedication to good finishing. Commercial speaker manufacturers apparently spend upto 60% of their costs on finishing of enclosures, I'd read somewhere.
I would normally agree about keeping the c-c distances as small as possible, but on a tilted baffle, as long as the listener is a few feet away, it can work... especially with shallow slopes.
Offsetting the tweeter is usually not a good idea, it can make a mess off axis.
I do agree with most of what else is stated here, especially the need for horizontal braces. You could still install some dowels through the driver openings and glue them to the center brace and side walls.
I wasn't aware of multiple types of Araldite. The one I use is the only I've been seeing for the last fifty years. It's a two-part exoxy adhesive which needs to be mixed before applying.
Have you looked on Ebay? This chap is a professional seller, not an individual selling one or two personal items.
I am sorry, but I couldn't understand this point.
There is no need to have a 25mm x 2 thickness baffle to do a 45-degree bevelling. You can have thinner baffles. Similarly, there is no reason to believe that 18mm rounding off is adequate. The rounding-off is not a cosmetic issue -- the radius of the rounding directly impacts how much of edge diffraction you can reduce. The larger the radius, the more useful it is for reducing edge diffraction. The 18mm you saw earlier in this thread is not a magic number. Neither is 25mm x 2.
True.
Whether shallow slopes make listenable speakers with the Peerless woofer used here is of course a different question.
Never heard of this one. Can you point me to something I can read up? (I have Vance Dickason 7/ed, if that helps.) Also, offsetting the tweeter helps reduce (or distribute, to be precise) edge diffraction, which impacts on-axis SPL evenness. I tend to worry about on-axis first, before off-axis. Will wait to hear more from you.
Oh yes. In fact, strips, say 2" wide, cut from 20mm plywood, long enough to stretch from one sidewall to the other, could be inserted through the driver openings. Then, drill the sidewalls and the brace edgewise, then pour Araldite and insert screws. Hate to think what it would do to the finish, though.
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rajesh srinivas
Active Member
Totally unsuitable. It doesn't bond metal. For braces, I want the adhesive to bond plywood, MDF and metal (the screws) permanently.
And even if it did, I'd choose the adhesive with more 'body' in this case than the the thinner one which flows easily. In this application, I need greater mechanical strength, which the lighter, free-flowing adhesives usually have less of.
Typically anything which is labelled "carpenter's glue" is not suitable for the stronger joining applications -- they're good for fitting laminate sheets on plywood, etc.
My web page on the Darbari construction gives a hyperlink to this seller. What happened when you clicked on that link?
Each builder chooses his own optimum points I guess.
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