After waiting all night for the glue to dry I've just tried a tap test over all of the box.
Interestingly the only section of the box that doesn't go "tonk" or "clunk" is the bottom panel which has 2 layers of 12mm chipboard glued together.
And this is before I layer the MDF panel over the sides.
It's always been my belief and experience that layering two dissimilar materials together helps damp vibration and I've layered 3 different materials together at times but this is the first time I've done that combined with so much extra stiffening.
Another lesson in box building.
Now I have to figure out how to add some internal damping to the walls with all these battens and sticks in the way and whether of not to add some damping to the port to try and reduce the tuning a few Hertz if that was possible.
Interestingly the only section of the box that doesn't go "tonk" or "clunk" is the bottom panel which has 2 layers of 12mm chipboard glued together.
And this is before I layer the MDF panel over the sides.
It's always been my belief and experience that layering two dissimilar materials together helps damp vibration and I've layered 3 different materials together at times but this is the first time I've done that combined with so much extra stiffening.
Another lesson in box building.
Now I have to figure out how to add some internal damping to the walls with all these battens and sticks in the way and whether of not to add some damping to the port to try and reduce the tuning a few Hertz if that was possible.
Yeah, the goal is to either stiffen it sufficiently to raise box Fs well above its intended pass-band (upper mass corner) or mass load it to push it well below its lower mass corner, which typically means concrete construction for a sub, but you're trying to do both, essentially 'robbing Peter to pay Paul' 
, so maybe better not to add any more mass to the panels.
It will roll it off a little, but mostly just over damps the system, so better to shrink its CSA to suit.
, so maybe better not to add any more mass to the panels.It will roll it off a little, but mostly just over damps the system, so better to shrink its CSA to suit.
Well I can shrink the CSA by 38mm if I use a short bit of the same 19mm*140mm batten and it wouldn't be too far from the equivalent of a 12" pipe.
I only saw this post of yours GM after gluing the extra MDF on.
It's Titebond so I am not going to try and remove it, but it is only 6mm panel so not to much added mass
I only saw this post of yours GM after gluing the extra MDF on.
It's Titebond so I am not going to try and remove it, but it is only 6mm panel so not to much added mass
You did GM, but I sized that shelf port based on the use of a 12" pipe in Box Modeller and got the arithmetic wrong.
In Box Modeller the difference in length between a 12" pipe or tube and a 12.5" tube is more than a few millimetres.
So yes I'll add side inserts to reduce the width
In Box Modeller the difference in length between a 12" pipe or tube and a 12.5" tube is more than a few millimetres.
So yes I'll add side inserts to reduce the width
In the case of plywood, many layers, disimilar in the direction of the grain. The energy has to cross the “glue” gap and then into the next layer.
dave
We usually see some damping stuck or stapled to the walls tho.
Not using any would make finishing this a bit easier but on the other hand I have a few old polyester doonas and pillows sitting unloved in the stash I could insert easily enough
Not using any would make finishing this a bit easier but on the other hand I have a few old polyester doonas and pillows sitting unloved in the stash I could insert easily enough
Damping a speaker is not about dumping some trash inside of it. It has to serve a purpose. In the past, with passive x-overs, often too much high frequency exited Bass cabinets. Today we cross deeper, active. At these low frequency's the usual stuffing- stuff does not work significantly.
At the walls it does not help at all.
Just try it empty and if you think you find a reason, adress the problems you really have. Usually with a DSP instead of an old pillow.
At the walls it does not help at all.
Just try it empty and if you think you find a reason, adress the problems you really have. Usually with a DSP instead of an old pillow.
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Stash NOT trash
😊
But don't you mean HF leaving the box and/or vent?
But I can see that using a steep crossover [ LR 4 using the Behringer CX units] and Bi-Amping there wouldn't be much signal above the selected XO frequency.
Especially if I only use it sub 80Hz but I've also read differing opinions on volume filling large boxes like this.
Experimenting with stuffing etc won't mean anything without being able to measure things accurately tho, and I've still not got around to that stage
😊
But don't you mean HF leaving the box and/or vent?
But I can see that using a steep crossover [ LR 4 using the Behringer CX units] and Bi-Amping there wouldn't be much signal above the selected XO frequency.
Especially if I only use it sub 80Hz but I've also read differing opinions on volume filling large boxes like this.
Experimenting with stuffing etc won't mean anything without being able to measure things accurately tho, and I've still not got around to that stage
After several folks around the world found that even my very modest damping of large Altec cabs was too much for them I got wised up that when they're this big, critically damping the vent is sufficient, though personally still prefer some FG damping at the top, one side, back around the driver as Altec recommended.
Please explain that in further depth GM.
I'm not quite understanding it.
Do you mean that the bass was too deep?
If so I can live with that.
I'm not quite understanding it.
Do you mean that the bass was too deep?
If so I can live with that.
No, they considered them over-damped in that some of the Altec woofer's super wide range (~5 kHz) 'color'/'definition'/'inner detail'/whatever of the music was 'lost' in the cab for lack of a better description and when after the fact they removed the damping (all in some cases) did the click test, it further 'tightened' them up, so win-win to their collective ears.
Frankly, I would normally have just said fine, to each his own and not mentioned the test, but one was a Roman gent that was apparently a 'who's who' in Rome's symphony/opera houses with permanent front row center seats, so took him and his wife's critique very seriously.
Frankly, I would normally have just said fine, to each his own and not mentioned the test, but one was a Roman gent that was apparently a 'who's who' in Rome's symphony/opera houses with permanent front row center seats, so took him and his wife's critique very seriously.
Here is another question.
Having put so much effort and cash onto building this box, and knowing that the cheap S/H woofer is to be replaced at some stage if this box works as I hope what of the currently available drivers around in Australia might work in this box as it stands?
The SBAudience ?
Or perhaps the cheap Peerless
https://www.ebay.com.au/itm/265096697935
Putting the data into box modeller they both seem to work in a similar fashion; the SB takes more power and goes a little deeper but the cheap Peerless graph seems to show a smoother bottom end and while not exactly cheap enough for good WAF it is a lot cheaper than the SB
Having put so much effort and cash onto building this box, and knowing that the cheap S/H woofer is to be replaced at some stage if this box works as I hope what of the currently available drivers around in Australia might work in this box as it stands?
The SBAudience ?
Or perhaps the cheap Peerless
https://www.ebay.com.au/itm/265096697935
Putting the data into box modeller they both seem to work in a similar fashion; the SB takes more power and goes a little deeper but the cheap Peerless graph seems to show a smoother bottom end and while not exactly cheap enough for good WAF it is a lot cheaper than the SB
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I have another question.
I have just added up all of the costs involved in making this box; including a new bottle of Titebond 2 , 4 heavy duty wheels and a box of chipboard screws I've spent $367- and I've got to buy a new sheet of plywood for the baffle because the HDchipboard flooring isn't going to work.
Is this in line with other Australians recent builds of boxes this large??
How does this compare to costs in other places like the UK, Canada, the EU and the USA?
I have just added up all of the costs involved in making this box; including a new bottle of Titebond 2 , 4 heavy duty wheels and a box of chipboard screws I've spent $367- and I've got to buy a new sheet of plywood for the baffle because the HDchipboard flooring isn't going to work.
Is this in line with other Australians recent builds of boxes this large??
How does this compare to costs in other places like the UK, Canada, the EU and the USA?
Gallon of titebond($25) smaller typical size ~$10
4x8foot(~122/244cm)Sheet of ‘cabinet grade’ high ply count pine ($90.)
Mdf($65)
4x8foot(~122/244cm)Sheet of ‘cabinet grade’ high ply count pine ($90.)
Mdf($65)
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Jeez I wish I could buy for as little as that, even taking exchange rate into account.
A "gallon" of TB2 was $57- plus 10%GST
A "gallon" of TB2 was $57- plus 10%GST
More time waiting for glue to dry.
I don't think that 12mm ply is stiff enough for a woofer this size so I'm glue laminating two 12mm panels together. Only where the driver is tho and not the full 1800 depth. Added some cantilevered feet and wheels so I can move it around and the top now has that 32mm thick bit of MDF glued on.
It will be interesting trying it out but never again will I do a box this large [ well unless we win the lottery and we buy an old church for a music and banqueting room] it's been less that perfect fun with such a small shed to work in.
I don't think that 12mm ply is stiff enough for a woofer this size so I'm glue laminating two 12mm panels together. Only where the driver is tho and not the full 1800 depth. Added some cantilevered feet and wheels so I can move it around and the top now has that 32mm thick bit of MDF glued on.
It will be interesting trying it out but never again will I do a box this large [ well unless we win the lottery and we buy an old church for a music and banqueting room] it's been less that perfect fun with such a small shed to work in.
Attachments
Just in case people think that the 89*19 pine is a bit weak to support the box; they are reinforced underneath with some offcuts of 12mm hardwood marine ply and the cantilever is only 95mm. Each wheel is rated at 50kilos so a safety factor there but I have no idea what this box actually masses but I can't lift it.