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Patrick Bateman 17th June 2010 01:29 AM

Night of The Living Bassheads
 
Here's the plans for a 15hz tapped horn that I'm building.

There are a number of plans on the forums for tapped horns, but this is a bit different. Here's why:
  • I've built a few tapped horns, and I've found that the use of multiple drivers smooths out the response. This one uses two drivers, but it's spaced as if there's three. This offers the benefits of multiple drivers, while maintaining an easy load on the amp.
  • Conventional horns and bandpass subs roll off the highs. The low-pass filter effect of the horn reduces 2nd and 3rd harmonic distortion. Tapped horns don't really work the same way, particularly if the woofers are mounted close to the mouth. In my experiments, I've found that cheap drivers can sound good in a conventional front loaded horn, but tapped horns like a driver with lots of xmax and low distortion. To this end, I've selected a pair of twelves with 24mm of xmax, and shorting rings.
  • To further reduce distortion, I'm using push-pull mounting to lower the 2nd harmonic.
  • I'm using an extraordinarily large box to raise efficiency and smooth out response.

All in all, this tapped horn may be a good candidate for your home theater.


I spent most of the time optimizing the volumes in Akabak, so the plans themselves are kind of rough. (I'll post the Akabak sims later.) The outside dimensions are 102" tall, 24" wide, and 16" deep. That's twenty three cubic feet(!)

Sims coming soon...


MartinQ 17th June 2010 02:13 AM

Whatever you do, don't ... don't ... don't believe the hype. Build it and see! =]

:P

I've been thinking of a similar project. A horn with a replaceable driver panel that could have up to four drivers mounted so I could test combining and spacing. After doing some sims I'm not convinced that there is much merit in it, but I'd love to see how this turns out!

How low can it go?!?

Patrick Bateman 17th June 2010 03:16 AM


This illustration makes it easier to follow what the path is in the horn. While it wasn't intentional, this layout is very similar to The Tower of Power. I didn't even notice until I was reviewing the patent today.

MartinQ 17th June 2010 03:30 AM

Where is the mouth, at the bottom (24 x 12) ?

Patrick Bateman 17th June 2010 05:32 PM

Quote:

Originally Posted by MartinQ (Post 2218900)
Where is the mouth, at the bottom (24 x 12) ?

You can put it anywhere on the bottom; it's 1558 sq cm. (241 square inches.) I haven't decided where to put it yet, because I haven't decided if I'm going to mount it from my wall, or simply put it in the corner.


Patrick Bateman 17th June 2010 05:49 PM

Here's the Akabak model. Note that this is a "true" dual driver model. Hornresp can't do this - it models multiple woofers as if they're radiating from the same point in space. The use of multiple woofers can extend the bandwidth of a tapped horn, and you need Akabak to model that.

Here's the predicted response. This is with 49 volts. It basically has a bandwidth of three octaves, from 16hz to 128hz. That top octave is a bit rough; I intend to roll it off at 80hz.

And the predicted excursion. The driver has 25mm of excursion - we can get down to 15hz or so at house-shaking levels.



System 'S1'

|DATA EXPORTED FROM HORNRESP - RESONANCES NOT MASKED
|COMMENT: th-mini clone, xara file is on other pc, 5/10/09. This one w/MCM 55-2421x2
|================================================= ================================================== =====
|REQUIRED AKABAK SETTINGS:
|File > Preferences > Physical system constants:
|Sound velocity c = 344m/s
|Medium density rho = 1.205kg/m3
|Sum > Acoustic power:
|Frequency range = 10Hz to 20kHz
|Points = 533
|Input voltage = 31.62V rms
|Integration = 2Pi-sr
|Integration steps = 1 degree ... 1 degree
|Integration method = Cross
|================================================= ================================================== =====

Def_Const |Hornresp Input Parameter Values

{
|Length, area and volume values converted to metres, square metres and cubic metres:
Rg = 0.01e-0; |Amplifier output resistance (ohms)
S1 = 155.00e-4; |Horn segment 1 throat area (sq cm)
S2 = 225.25e-4; |Horn segment 1 mouth area and horn segment 2 throat area (sq cm)
S3 = 296.70e-4; |Horn segment 2 mouth area and horn segment 3 throat area (sq cm)
S4 = 593.40e-4; |Horn segment 3 mouth area and horn segment 4 throat area (sq cm)
S5 = 1558.00e-4; |Horn segment 4 mouth area and horn segment 5 throat area (sq cm)
S6 = 1558.10e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S7 = 1558.20e-4; |Horn segment 6 mouth area (sq cm)

L12 = 30.20e-2; |Horn segment 1 axial length (cm)
L23 = 60.80e-2; |Horn segment 2 axial length (cm)
L34 = 228.6e-2; |Horn segment 3 axial length (cm)
L45 = 274.32e-2; |Horn segment 4 axial length (cm)
L56 = 60.80e-2; |Horn segment 5 axial length (cm)
L67 = 60.80e-2; |Horn segment 6 axial length (cm)

|Parameter Conversions:

Sd = 982.00e-4; |Total diaphragm area for 2 parallel drivers (sq cm)

}

|================================================= ================================================== =====

|Network node numbers for this tapped horn system:

|0-Voltage-1-Resistance-2----------
| x x
| --Driver1------ ---------------------------
| x -Driver2-------------- x
| x x x x
| 8-Segment-9-Segment-10-Segment-11-Segment-12-Segment-13-Segment-14-Radiator
|================================================= ================================================== =====


Def_Driver 'Diyma12'

Sd=491.00cm2
Bl=18.05Tm
Cms=1.21E-04m/N
Rms=8.57Ns/m
fs=27.0000Hz |Mmd = 73.86g not recognised by AkAbak, fs calculated and used instead
Le=2.03mH
Re=3.80ohm
ExpoLe=1

System 'System'

Resistor 'Amplifier Rg'
Node=1=2
R={Rg}

Driver Def='Diyma12''Driver 11'
Node=2=0=9=13
Driver Def='Diyma12''Driver 21'
Node=2=0=10=12

Waveguide 'Horn segment 1'
Node=8=9
STh={S1}
SMo={S2}
Len={L12}
Conical

Waveguide 'Horn segment 2'
Node=9=10
STh={S2}
SMo={S3}
Len={L23}
Conical

Waveguide 'Horn segment 3'
Node=10=11
STh={S3}
SMo={S4}
Len={L34}
Conical

Waveguide 'Horn segment 4'
Node=11=12
STh={S4}
SMo={S5}
Len={L45}
Conical

Waveguide 'Horn segment 5'
Node=12=13
STh={S5}
SMo={S6}
Len={L56}
Conical

Waveguide 'Horn segment 6'
Node=13=14
STh={S6}
SMo={S7}
Len={L67}
Conical

Radiator 'Horn mouth'
Node=14
SD={S7}

chris661 17th June 2010 07:35 PM

Perhaps add a warning sticker?

Seriously, though, I've heard of someone bringing his ceiling down during a party, so perhaps some sort of structural re-enforcement is in order?

zora 17th June 2010 08:45 PM

Are you using the Diyma 12's? Can a person buy one of those anymore?

JP

Spasticteapot 17th June 2010 08:51 PM

That is head-explodingly ridiculous.

Have you considered charging people for the removal of kidney stones? Just give 'em some earplugs and put on your DVD of "Earthquake"...

Brian Steele 17th June 2010 08:59 PM

Quote:

Originally Posted by Spasticteapot (Post 2219708)
That is head-explodingly ridiculous.

Have you considered charging people for the removal of kidney stones? Just give 'em some earplugs and put on your DVD of "Earthquake"...

Or that version of "Clubbed to Death" by Rob Dougan with all the ultra low frequency stuff...


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