The original anthology II construction is out of 19mm mdf and if going with plywood I can either source 18mm or 21mm. I'm worried about going with 18mm since plywood is already less dense than mdf, but is it possible to go with 21mm and address the issues with baffle widening and or internal volume displacement? Or is this already too much of an stretch and would make changes in the characteristics of the speaker? Oooooor... 3mm wider baffle on each side from thicker plywood, veneer and finish doesn't make that much of a difference?
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As stated before, density is not an asset.
A stiff and light material is better than a dense one. Sometimes it comes along with increased stiffness, but it is thwe stiffness that is an asset not the density.
For this boix, if properly braced, quality 15mm ply would do the job.
dave
@planet10 That flew over my head the first time I read it so I didn't remember it hahah.
Turned on the gears in my head and it clicked. What would be the game when bracing? Reducing the distance between surfaces by dividing them into smaller segments using denser, but thinner bracing therefore adding stiffness to the enclosure and reducing vibrations? How should the braces be spaced and in what way do they interfere with the sound waves bouncing inside of the box?
Turned on the gears in my head and it clicked. What would be the game when bracing? Reducing the distance between surfaces by dividing them into smaller segments using denser, but thinner bracing therefore adding stiffness to the enclosure and reducing vibrations? How should the braces be spaced and in what way do they interfere with the sound waves bouncing inside of the box?
Bracing is one of the topics that DIY folk often don't get quite right. Stiffening the baffle will be beneficial in reducing the work put into the cabinet by the drivers hammering away on the baffle. Once the work is in the cabinet it is removed by damping or radiating away as (unwanted) sound. The panel braces above, between and below the woofers in your design are pretty much the best that can be done in this respect.
Bracing the other 5 sides of speakers will stiffen them and reduce the radiated sound in the low frequency stiffness-controlled region but it is the resonances that are loud not the low frequencies. The increased stiffness pushes the resonances to higher frequencies but leaves them about as loud in SPL terms. Unfortunately the higher frequencies may be perceptually more intrusive although this depends on the actual frequencies involved.
What reduces the magnitude of resonances is damping (and radiating away sound!). Both MDF and plywood have low levels of internal damping leading to undamped cabinets having high Q resonances of a large magnitude. This means even fairly modest levels of added (effective) damping can have a significant effect in reducing the magnitude of the resonances and making the cabinet quieter.
Perhaps it should be noted that sound radiated by a reasonable speaker cabinet tends to play only a minor role in the quality of the sound heard at the listening position. Quite a few other factors are more important but it is one that a DIYer has almost full control over.
Bracing the other 5 sides of speakers will stiffen them and reduce the radiated sound in the low frequency stiffness-controlled region but it is the resonances that are loud not the low frequencies. The increased stiffness pushes the resonances to higher frequencies but leaves them about as loud in SPL terms. Unfortunately the higher frequencies may be perceptually more intrusive although this depends on the actual frequencies involved.
What reduces the magnitude of resonances is damping (and radiating away sound!). Both MDF and plywood have low levels of internal damping leading to undamped cabinets having high Q resonances of a large magnitude. This means even fairly modest levels of added (effective) damping can have a significant effect in reducing the magnitude of the resonances and making the cabinet quieter.
Perhaps it should be noted that sound radiated by a reasonable speaker cabinet tends to play only a minor role in the quality of the sound heard at the listening position. Quite a few other factors are more important but it is one that a DIYer has almost full control over.
They are not the most effective orientation.
My goal is to push any poyential box resonances as high as possible, and ideally with a fairly high Q.
I posted Tappan’s results in Post #21 https://www.diyaudio.com/community/threads/anthology-ii-in-mdf-or-plywood.413035/post-7691081
This gives us a reallhy good idea of how best rto orient the bracing.
This likelihood graph is conceptual, the red curve (2nd order) easily supportable but there is enuff to suspect that the blue curve (4th orde) is more likely.
Now consier that with a HF Hi Q resonance it will need significant energy pumped into it in a very narrow frequency band for a sustained period of time. What music do you know that has continous HF bits? And up that high the amount of energy in the signal decreases. Between every pair of adjacent plies is a layer of damping. This is particularly good at eating upo HF.
So any panel resonances are pushed up where there is bvery little chance they will be excited necomes quit unlikely. If it is not excited it is as if they do not exist,
Alps note that due to airapace damping very little acoustic energy reaches the panels thru the air, and any will be at low frequencies. It is easy to show that most comes from the direct connection of the driver to the baffle. The baffle is typically the weakest panel due to the holes, and with a big weight hanging off the back. We typically brace teh woofer magnets to the back, top, bottom of the box creating a rigid enegibneered structure. A brace usually is full width/ height of the box. We target 30-40% holes. Anthology would need some braces from the sides to the front-back brace, these i would leave open behind teh woofers. Depending on the box dimensions more than 1 F-B, 1 S-S brace may noy be sufficient.
These ar ethe braces we put into Jeff’s SuperPensils, the Anthology would require simialr at a minimum
We have built 100s of boxes with this philosophy with VERY good results.
dave
Can you tell the OP why the baffle is being not being stiffening in a pretty much optimum way by placing stiffeners as close as possible to the forces bending the baffle and orientated edgewise to provide maximum stiffness?
Damping is what changes the Q of resonances. Adding stiffness or mass moves the resonances up or down in frequency leaving the Q unchanged. What do you think is reducing the damping and raising the Q in your approach?
I know which I would choose between an approach with well damped low level low Q low resonances that are inaudible when driven and an approach with large high Q resonances which would be audible and sustained if driven but might not get driven if lucky with the notes present in the music.
Vibrating structures broadly fall into 3 frequency regions: stiffness controlled (low frequencies), resonance controlled (mid frequencies) and mass controlled (high frequencies). The regions are determined by which force (stiffness, damping, inertia) is the largest and hence largely determining the response to applied forces like the drivers hammering away on the cabinet. The mass controlled region is not quite as clear cut as the stiffness controlled region in that it can be influenced by a high number of resonances if they are lightly damped. This can be seen in the current thread about the SB midrange driver with a stiff cone where a high density of lightly damped resonances is raising the high frequency response in a similar manner to wideband drivers. Anyway the point is that adding stiffness when the dominant noise is mass or damping controlled doesn't do anything much to reduce noise because it is not the controlling force.
Probably. It's a subwoofer using 18N862. 130L closed cabinet... no vibration at high spl. Good stuff
I would use 30mm. Lots of bracing, and your good. There would be no "what if" thoughts.
And don't worry about front baffle width. Just route the edges 10mm on each side, either round or 45edge, doesn't really matter
And don't worry about front baffle width. Just route the edges 10mm on each side, either round or 45edge, doesn't really matter
That is what my holey brace does, directly connecting to the driving forceand not some distance from the “executor”.
The horizontal braces do stiffen the bafflebut tappan shows that it does not push any potential resonance as high. So horizontal not as effective as vertical.
Notdirectly comparable since F is diffferent.
dave
Better than the brute force of lotsof bracing and obscenly thick box material, is the use of 2 woofers push-push which gives active reaction force cancelation dramatically lowering the energy pumped intothe cabinet (est 90% reduction. You couldprobably have as good an enclosure using 15mm plywood.
dave
We agree to disagree. About opposing woofer I agree 100%.
15mm-18mm just not my thing
We built a push-push woofer (CSS SDX10) out of 15mm toprove th point. Worked incrediably well, one person could lift the box with a couple fingers inthe driver cut-out, add the drivers it became a 2-man lift.
With 18” i’d use 18mm just to have sufficient meat on the baffle.
dave
With 18” i’d use 18mm just to have sufficient meat on the baffle.
dave
MTM for mids....meh
basic 2nd order
hot tweeter, no .5 for woofers.
Its whatever.
MDF is fine
people worry about magical bracing too much.
When speaker placement and crossover
be actually more important.
Some walls, some braces all done.
Sure the system will be a fun listen.
More direction to go than overthinking material.
After a zillion systems, you realize what actually
sounds better, or just material nit picking.
MDF or plywood I wear a mask regardless.
So = dont care.
Basically non square box, and mainly vertical
braces and a few horizontal.
Unevenly spaced.
Free range, grass feed , organic imported Egyptian hand spun.
Stone ground gluten free wool ...blah blah.
white poly bloop ..done
box , braces, stuff ...Done
basic 2nd order
hot tweeter, no .5 for woofers.
Its whatever.
MDF is fine
people worry about magical bracing too much.
When speaker placement and crossover
be actually more important.
Some walls, some braces all done.
Sure the system will be a fun listen.
More direction to go than overthinking material.
After a zillion systems, you realize what actually
sounds better, or just material nit picking.
MDF or plywood I wear a mask regardless.
So = dont care.
Basically non square box, and mainly vertical
braces and a few horizontal.
Unevenly spaced.
Free range, grass feed , organic imported Egyptian hand spun.
Stone ground gluten free wool ...blah blah.
white poly bloop ..done
box , braces, stuff ...Done
@WhiteDragon interesting take in a community where people focus on details a lot (including myself). You have any good example of proven designs since you don't seem to be into anthology that much?
I found this coloured mdf stuff. apparently it's better than your "regular" mdf. Thoughts? It's density for a board of 19mm is 720 Kg/m3. If my memory serves me right that's better than run of the mill mdf. In all the promotional material it is bare, making me think it might be more durable. With the price tag of 40 euro per square meter it falls between regular mdf and plywood. It is also made in Korea. Is it worth?
This is the site I found it on:
https://iverpan.hr/plocasti-materijali/mdf/mdf-u-boji-zuti-6603
Manufacturer site:
https://www.forescolor.com/en/
This is the site I found it on:
https://iverpan.hr/plocasti-materijali/mdf/mdf-u-boji-zuti-6603
Manufacturer site:
https://www.forescolor.com/en/
It‘s the same stuff, just pigmented. As mdf goes, the colored variety is likely in the upper tier, but it is still the same glorified cardboard.