This is a speaker that's going to be regularly carried around. Mdf is an apallingly bad choice of material on grounds of both weight and weakness. When the bearer collapses of exhaustion, the speaker will break.
Use good quality birch ply. 6mm sheet is just too thin, you'd need to glue several layers together evenly - I'd rather just cut thicker stuff, even with a panel saw, than have to go through all that gluing. The laser isn't any use to you that I can see. Brace it in an irregular and asymmetric pattern as much as you can.
Google "speaker bracing" to get some ideas on what's important here, within the range of what you can reasonably achieve.
I understand that the way the forum index pages work makes it tempting to read only the last few posts before joining in a discussion, but it does often seem to lead to the wrong end of the stick being grabbed and the discussion going off on a tangent of little relevance to the OP's question.
Use good quality birch ply. 6mm sheet is just too thin, you'd need to glue several layers together evenly - I'd rather just cut thicker stuff, even with a panel saw, than have to go through all that gluing. The laser isn't any use to you that I can see. Brace it in an irregular and asymmetric pattern as much as you can.
Google "speaker bracing" to get some ideas on what's important here, within the range of what you can reasonably achieve.
I understand that the way the forum index pages work makes it tempting to read only the last few posts before joining in a discussion, but it does often seem to lead to the wrong end of the stick being grabbed and the discussion going off on a tangent of little relevance to the OP's question.
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For any given section, MDF is heavier and weaker than any reasonable quality plywood. Put it up against good baltic birch ply and there's just no comparison.
If you doubt this, ask at a timber merchant. They'll probably laugh as they answer. If you're not convinced, ask for some offcuts and break them yourself.
Then weigh some.
If you doubt this, ask at a timber merchant. They'll probably laugh as they answer. If you're not convinced, ask for some offcuts and break them yourself.
Then weigh some.
Trade off: what are you trading off to gain the downside of MDF? Heavy is an anti-asset when it comes to keeping box resonances at bay, and an anti-asset when it comes to humping the boxes.
dave
(Acrylic maybe instead of glass? Completely different material I know but.... 
)
Wow, you guys are really passionate about your wood.
OK, so the stiffness/thickness ratio crown goes to ply. Good, I wanted to make it out of ply.
I'm torn between my love of doing thing properly and my love of lasers.
Then again the laser also plays to my love of precision.
I'm thinking of making an outer shell using the laser, because it's so precise, and the battery box will be fine.
I'll either thicken/stiffen the speaker box sides up to 12mm or build a box in a box (but probably the first)
The guy who's helping me is a talented carpenter, so I'm pretty sure he can meet any requirements I need.
Anyway, I can always build it again if it doesn't work (with said carpenters help because I can't carpent for ****)
Anyway, the drivers arrived (woo!) and now we're on to the build at last.
They happen to have rubber surrounds which match the brick-out-house feel nicely.
Still need a battery charger and switches and doo dads but mostly it's wood choppin' time!
J.
)Wow, you guys are really passionate about your wood.
OK, so the stiffness/thickness ratio crown goes to ply. Good, I wanted to make it out of ply.
I'm torn between my love of doing thing properly and my love of lasers.
Then again the laser also plays to my love of precision.
I'm thinking of making an outer shell using the laser, because it's so precise, and the battery box will be fine.
I'll either thicken/stiffen the speaker box sides up to 12mm or build a box in a box (but probably the first)
The guy who's helping me is a talented carpenter, so I'm pretty sure he can meet any requirements I need.
Anyway, I can always build it again if it doesn't work (with said carpenters help because I can't carpent for ****)
Anyway, the drivers arrived (woo!) and now we're on to the build at last.
They happen to have rubber surrounds which match the brick-out-house feel nicely.
Still need a battery charger and switches and doo dads but mostly it's wood choppin' time!
J.
Hi thank you very much for this extremely interesting thread that i have discovered just now
As you speak of PA systems i had a chat with an technician/installer of a very big PA equipment shop here in Italy
I was checking the entry level prices of some PA speakers
As i was seeing plastic and wood cabinets i asked the guy which of the two were the best option
He answered that of course if you place them outside the plastic ones have advantages
But purely on a sound basis there is just no comparison The speakers with a wood cabinet (with same drivers and circuits) always sound so much better that is shocking
And unfortunately the heavier they are the better they sound By far
A speaker cabinet must be stiff and above all heavy ... the heavier the better
Some years ago a friend of mine found some lead foils ... i know it is a very toxic material
Anyway he glued and fastened some of these foils inside the cabinet of my speakers The result was shocking
In particular the most amazing improvement were in soundstage and performance with instruments with big low end
At a certain point i had a strong sensation of the speakers disconnect from the amp so much that i checked that ... of course they were indeed playing but the sound was completely detached from them and coming from the space Amazing
A Toccata e fuga in particular was sounding fantastic So much better than on the unmodded speakers
Unfortunately lead is very very toxic But for me it is a God's gift for cabinets
I am sick for soundstage ... i heard an amazing 3D soundstage from a pair of Wilson Audio Cub ... 75 pounds each
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if you knock on a bulletproof glass it would sound extremely dead There are layers of tempered glass alternate with some plastic layers i understandi always wondered how a glass cabinet would sound but it´s a terrible material to work with
There was at least one commercial brand using it
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Recently i heard a statement about the optimum ratio between the cabinet mass and the moving mass of a woofer I was shocked In the thousands
If we consider this driver as an example https://www.scan-speak.dk/datasheet/archive/25w-8565-01.pdf
it has a moving mass of 47g that means 50kg of cabinet to avoid vibrations We have not defined what heavy means by the way
To be honest the designer talked about a ratio of even 5000 I know Its a lot The idea is that the only thing that moves at any SPLs and Hz must be the woofer diaphragm
I have noticed another thing When magazines measure the vibrations of a cabinet usually they forget the more important panel .. the front baffle
If i am not wrong at B&W used laser devices to measure the front baffle vibrations starting with the first 801 models maybe ?
The weight was around 50kg
Clearly domes have a very low mass and so they are not a problem
One really only needs to worry about the box physically moving in space with woofers, and the smart choice is to eliminate that source of “bad” actively by loading them push-push.
One can brute force a baffle by making it very thick, or use clever design to integrate the baffle as part of a rigid structure with the rest of the boxx (the of the purposes of the driver holry brace you see in my designs).
A heavy panel wil resonate at a lower frequency than a lighter panel of the same stiffness. The latter is preferred.
dave
One can brute force a baffle by making it very thick, or use clever design to integrate the baffle as part of a rigid structure with the rest of the boxx (the of the purposes of the driver holry brace you see in my designs).
A heavy panel wil resonate at a lower frequency than a lighter panel of the same stiffness. The latter is preferred.
dave
I see But then why all subs are so heavy ? bracing can be done with light wood i guess However this is a very important point
I have been somewhat misled by this very interesting video found on Youtube
Listen at 14:00 in particular I was shocked
The speaker talks about OB speakers but my guess is that the rule can be extended to any speaker Also subs for instance
Of course this could be an ideal situation with normal situations deviating from the ideality
Again this is for me extremely important to understand rightly ... i am afraid that bracing is a much more challenging task than just adding weight
Because the drivers are heavy. In my push-push SDX10 woofers, one could use 2 fingers in a driver cutout can lift the box (15mm BB), add the drivers and you really would like 2 guys to carry it.
dave
2001 Space Odessy.
We actually did the monolith.
http://wodendesign.com/downloads/HawkingMemorialObelisk-0v81-090418.pdf
In an OB the mass serves a different purpose. He was not able to take advantage of the active force cancelation given the limited number of woofers. 5000:1 is likely overkill.
dave
We actually did the monolith.
http://wodendesign.com/downloads/HawkingMemorialObelisk-0v81-090418.pdf
In an OB the mass serves a different purpose. He was not able to take advantage of the active force cancelation given the limited number of woofers. 5000:1 is likely overkill.
dave