Single sheet TH challenge

jbell

Member
2003-04-02 4:34 am
.
Ok, so being 'never satisfied' I'm trying to better 'the cube' that I just built a few of.

Since there are several hornresp tapped horn quarterbacks that are better than I.... Here's the challenge.

1. Single 4x8 sheet of plywood. All panels, including bracing/reflectors, etc..
2. Most SPL 'area under the curve' from 40hz-140hz (minimum 100db average +-3db 1W1M)
3. Minimum 125db single cabinet from 'about' 40hz on up in 2pi space (understand, some designs in single cabinet won't 'quite' be able to hit 40hz, that's ok...)
4. Under $200 driver.

Bonus points for a better shape than a cube.

EDIT:

This section of the original post will be used for navigating this thread, and will be updated occasionally.
This sub was designed for the eminence series of drivers, 4015lf, 3015lf, Kappa Pro 15-LF2. Others work too.

cad drawing -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-8.html#post2278081
General Layout -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-6.html#post2273977
cut sheet -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-4.html#post2265677
note about using PL premium poly glue -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-49.html#post2484469
High pass filters and excursion -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-74.html#post2509736
First thoughts on 'cone correction' -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-60.html#post2499741
Directivity Testing -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-85.html#post2525499
Non US driver, (monacor) -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-113.html#post2759432
US Drivers/PowerRatings -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-173.html#post3193764
Nice little comparison chart -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-119.html#post2836328
One of my favorite pics of FlipC's dozen -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-88.html#post2528082
Quick post about construction technique -- http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-43.html#post2470384
 
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polviggen

Member
2009-08-28 5:41 pm
the cubo15 seems to do that pretty ok.

Cubo 15

it's very easy to built, maybe try one and compare to your cube ? I built the extended version with an 3015LF and the output is pretty damn good for that size.

just remembered, the extended version can't be built out of one panel, had to use a leftover piece for that.
 
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the cubo15 seems to do that pretty ok.

Cubo 15

it's very easy to built, maybe try one and compare to your cube ? I built the extended version with an 3015LF and the output is pretty damn good for that size.

just remembered, the extended version can't be built out of one panel, had to use a leftover piece for that.

Just curious - how would you go about simulating the "Cubo" design in HornResp?
 

djk

R.I.P
2001-02-04 4:23 am
USA
I don't buy the performance numbers presented.

MTL-1X.gif


The larger EV MTL-1X with an 18 doesn't go as deep? Isn't as efficient?

Show me the sim !
 

jbell

Member
2003-04-02 4:34 am
.
johan (rademakers) posted something VERY similar to the cubo in one of the TH threads way back.. I'm too lazy to look it up right at the moment. My problem with most of the hybrid cabinets are they are 50hz boxes, and it takes a pile of them to get to 40hz.

Because of that, I have kinda dismissed a hybrid... but maybe I should play around with a large chamber/short horn and see if there is something there I haven't seen in the past. I've also played around with compound horns at 3:1, and found something similar... Just hard to get to 40hz.

The folding is also the trick.. how to most efficiently fold with the fewest boards possible, while still having a good performing cabinet.

any creative thoughts?
 

Xoc1

Member
2008-11-08 8:25 pm
Devon UK
My attempt
12mm Ply 1off 8' x 4' sheet Eminence 3015LF driver
Trouble is that as you tweek the bandwidth and efficiency you loose the low frequency extension. The only way I can see to get it back is to increase the size which would take more timber....
Maybe a longer path length would be possible if the width of the horn was reduced to 400mm:D
Spl response grey line is J Bell Mini TH for comparison.
 

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djk

R.I.P
2001-02-04 4:23 am
USA
The 'iron law' still applies to a TH enclosure.

I don't think 40hz and 100dB are possible from a 2' cube.

50hz, yes, 40hz, no.

#9 is a good example of that at 90dB at 40hz.

"in reality it goes lower"

With room gain, I might buy that. In 2Pi or 4Pi, no way.
 
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Xoc1

Member
2008-11-08 8:25 pm
Devon UK
Certainly I did not use any smoke and mirrors in my attempt. I calculated the path length thru the middle of the bends - not at 0.7 of the bend width which would give a lower response. When I first tried to design a similar cabinet I ended up with a box 700 X 700 X 600 That seemed a better compromise, but would use too much timber for this challenge!
I think that J Bells original simple tapered TH will be hard to beat for its LF response.
 

jbell

Member
2003-04-02 4:34 am
.
The 'iron law' still applies to a TH enclosure.
I don't think 40hz and 100dB are possible from a 2' cube.
50hz, yes, 40hz, no.
#9 is a good example of that at 90dB at 40hz.
"in reality it goes lower"
With room gain, I might buy that. In 2Pi or 4Pi, no way.

This is not restricted to a cube, but to a 4x8 sheet -- A cube just happens to be the shape that lends itself to the taper I drew. I know I can get slightly more volume, and still get all the internal panels cut from a sheet -- but the folding/cut sheet is eluding me at the moment.

BTW -- leaving out the bottom panel and saying "just sit it on the floor" is cheating..... ;)

One last: The cube achieves 100db. [email protected] and [email protected] -- in marketing lingo thats 101db +-3db from 40-140hz.
 
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polviggen

Member
2009-08-28 5:41 pm
The 'iron law' still applies to a TH enclosure.

I don't think 40hz and 100dB are possible from a 2' cube.

50hz, yes, 40hz, no.

#9 is a good example of that at 90dB at 40hz.

"in reality it goes lower"

With room gain, I might buy that. In 2Pi or 4Pi, no way.

the only way to know is to built it and measure, JBells cube measured about 5hz lower then the sim too.
 

djk

R.I.P
2001-02-04 4:23 am
USA
The form-factor (cube) doesn't really matter, it's the net volume you can come up with.

A 2' cube has at best about 180L net volume.

In the past, I've built well braced 12mm Baltic Birch cabinets for subs. I didn't think 12mm was adequate. I think 15mm is adequate, but 18mm is better. Formica (Melamine) on 15mm about doubles the strength, but adds a lot of expense.

I've got a nice Hornresp for the Eminence 4015LF that's ±1.5dB from 40hz~150hz, and 100dB at 50hz. But it's 205L, not 180L. If you remove the external inductor and its DCR, it gives an almost identical response to yours.
 
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I would like to see live FR and Impedance graphs with a correctly dimensioned cab drawing. Like the two posted here, most of
the time the HR sim is not what gets built.

Could you enlighten us?

I, for one, make every attempt to follow the HR sim. Of course I use CONICs and build Parabolics, but the error is small, and I know I'm off a few percent
in the corners.

When I can't follow the HR sim, I go back and update the sim with the as-built information. If the damage is too bad, I scrap the drawing.

Sims are sims, they are one dimensional equations simming a three dimensional world. We're lucky they even come close.