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guesstimates for home sub enclosure size

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godathunder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote godathunder Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2018 at 3:53pm
my two biggest issues here are that I have two fairly small dimensions to play with - small enough at 264 and 284mm internal that fitting a 12" will require some bodging and that I cant make a bp or other design that is unforgiving in terms of my unknown ts parameters

t line is looking like an attractive option - my understanding is that Im looking to make a 1/4 wavelength tapering pipe stuffed full of enough old underpants and whatnot to damp any unwanted resonances

my driver measures at 28hz so a 1/4 wavelength of around 3m seems about right.
how critical is this measurement? would +/-10% be a reasonable tolerance or do I need to be pretty much smack on?

anyway, 3m seems easy enough to fold into the space Ive got available. so which layout seems more sensible?



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godathunder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote godathunder Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2018 at 3:59pm
this is the table it needs to hide under



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Sypa View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sypa Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2018 at 5:12pm
Check some Martinssons offerings maybe,the tpam series although thats for a 10"...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2018 at 8:43pm
It doesn't have to taper... and depending how you stuff it and the flare itself some people have adjust the length by nearly -20% and still achieved the modelled frequency.

There's a paper on the whole thing some where and I can't quite find the Damn thing...


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mobiele eenheid View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2018 at 8:59pm
Could you turn that 320 mm into 350 mm? In that case you could go for a real easy design.
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godathunder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote godathunder Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2018 at 10:16am
Originally posted by MattStolton MattStolton wrote:

Anything on this site of assistance?

The man of x-over fame himself:

http://www.linkwitzlab.com/thor-design.htm

I like his thinking - of course you could just stick it in a box and eq it to taste - man after my own heart.

iirc, many of his designs were based round compensating for non linearities in one component by using complimentary non linear parts elsewhere in the design

Originally posted by Sypa Sypa wrote:

Check some Martinssons offerings maybe,the tpam series although thats for a 10"...


@ sypa & aman: perhaps Im not looking hard enough but Im struggling to find anything that would fit my footprint


Originally posted by mini-mad mini-mad wrote:

It doesn't have to taper... and depending how you stuff it and the flare itself some people have adjust the length by nearly -20% and still achieved the modelled frequency.

There's a paper on the whole thing some where and I can't quite find the Damn thing...

glad to hear the accuracy isnt too crucial

the taper makes more sense to me as 3m of constant csa sounds like a recipe for resonance problems


Originally posted by mobiele eenheid mobiele eenheid wrote:

Could you turn that 320 mm into 350 mm? In that case you could go for a real easy design.

Id prefer no to but it would be possible to extend the legs of the table to accomodate the extra few mm. 

whats the design? Im all ears
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2018 at 12:31pm
From top till bottom:

35 - 40 Hz, highest sensitivity
30 - 35 Hz, quite flat frequency response
25 - 30 Hz, HT response

Technically the first is a tapped horn, the second a tapped horn/ transmission line hybrid, the third a transmission line with a cavity.

Material thickness is 15 mm, at this angle the gap is just 1 mm, for the angled panel. The height of the cabinet is just enough to fit the 12" (schematic is above view). I've just finished a 12" sub cabinet myself, using 9 mm Baltic birch for the sides, I could have slimmed it down to 340 mm.


Edited by mobiele eenheid - 10 December 2018 at 12:33pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aman Gebru Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2018 at 4:58pm
I would say your third design is a 4th order bandpass.

At some point the front chamber will stop and and the port will begin. Try siming it. You can move the port/front chamber transition point anywhere and still get the same outcome. So if the transition point is close to the driver, you will have a small front chamber that will require a longer port for the tuning freq. If the point is further along then you have a bigger front chamber which requires a shorter port. It's a sliding scale that always has a very similar response at which ever point you take along the pipe. It's the total length of the port/front chamber combination and cross section area, which decides the tuning freq.



Edited by Aman Gebru - 10 December 2018 at 4:59pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aman Gebru Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2018 at 5:05pm
If it were me I would build a cabinet the size you need to fit under the table, and make it a 4th order bandpass.

That way you can tailor the response to get what you need when you design it. The transient response need not be that bad with a 4th BP. I wouldn't want to make a 6th order for home use though, even though you would get much higher sensitivity.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 11 December 2018 at 5:13am
I'd probably go for the second design, the others are basically jpeg-filler material.

Quote It's the total length of the port/ chamber combination and cross section area, which decides the tuning freq
I've been saying this for years, it's good to see someone else who gets it ;)
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godathunder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote godathunder Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2018 at 1:57pm
Originally posted by mobiele eenheid mobiele eenheid wrote:

From top till bottom:

35 - 40 Hz, highest sensitivity
30 - 35 Hz, quite flat frequency response
25 - 30 Hz, HT response

Technically the first is a tapped horn, the second a tapped horn/ transmission line hybrid, the third a transmission line with a cavity.

Material thickness is 15 mm, at this angle the gap is just 1 mm, for the angled panel. The height of the cabinet is just enough to fit the 12" (schematic is above view). I've just finished a 12" sub cabinet myself, using 9 mm Baltic birch for the sides, I could have slimmed it down to 340 mm.

Thanks for the designs, I think Ill give the second one a shot - 
Ill get some mdf cut tomorrow then I have an excuse to hide in the shed while the kids are off school. I take it theres no reason to add wadding to this design
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godathunder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote godathunder Quote  Post ReplyReply Direct Link To This Post Posted: 02 January 2019 at 5:33pm

sawdust time
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