Tapped Horn Feeding A Unity Horn

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An externally hosted image should be here but it was not working when we last tested it.
Over on one of my other threads, someone posted an interesting new loudspeaker from Danley. It's named the SM-60M and the SM-60F. According the the brochure, "The loudspeaker shall utilize the synergy Horn/Tapped Horn patent-pending enclosure covering three pass bands.
The coverage pattern shall be 60° horizontal x 60° vertical. The loudspeaker shall have an operating rage of +/- 3 dB 270 Hz – 15 kHz. Sensitivity of 100 dBSPL @ 1m."


This is a really interesting device, so I thought I'd take a stab at guessing what's inside.

tapped-unity.jpg

Sorry about the crummy illustration. I'm away from home, and don't have access to my usual array of software :)

Anyways, in a unity horn, you have a compression driver at the apex, flanked by a pair of midranges. The compression driver is easy; the midranges are very tricky. By smooshing them up against the side of the horn, the air under the cone forms a low pass filter, and this chokes off your high frequencies. So you have to use midranges that have a very light cone, along with a powerful motor, to get them to play high.

The documentation on the new device has me thinking there's a tapped horn, and here's my "guess" on how it works. I'm guessing that there's a tapped horn that feeds the output from the back of the woofers cone to the front, just like in a tapped horn.

An externally hosted image should be here but it was not working when we last tested it.
Here's a pic of one of jbell's tapped horns. Imagine this, but shrunk down by 80%, and with the output feeding a Unity horn.

According to the literature, the SM-60M has a coverage angle of sixty degrees, and a 20" mouth. Based on that, the distance from the front to the back of the horn is about 32". (Each side of the triangle would be 20", and you lose about 25% because the output of the tapped horn is offset.)

So lets do the math!

Normally, when you build a horn, you pick a driver, and build a horn to fit it. In this case we already know the horns dimensions[/i]. So instead of picking a horn to fit a driver, we need to pick a driver to fit the horn.

First, we need to figure out what 32 inches is. That's 422hz. (Speed of sound / 32 inches.)

But horns are tuned to a quarter wavelength - so that's 106hz.

Some people on the forums recommend tuning a tapped horn to 0.707 times the driver's free air resonance. I tend to agree with this - it's given me good results. So based on the dimensions of this horn, we'd want to feed it with a woofer that has an FS of 150hz. (150 * .707 = 106hz.)

Here's the specs of the woofer that's purportedly in there:

579403c86d.jpg

  • Resonance frequency Fs Hz 138
    [*]DC resistance Re Ohm 12.2
    [*]Mechanical Q factor Qms 3.4
    [*]Electrical Q factor Qes 0.87
    [*]Total Quality factor Qts 0.69
    [*]Equivalent volume Vas L 1.03
    [*]BL factor BL Tesla m 10.7
    [*]Effective piston area Sd m2 0.0074
    [*]Max. linear excursion Xmax mm 3.5

If anyone has any comments on this, I'm all ears! I'm just guessing here. And the full-range version of this horn seems like a substantial upgrade over the Lambda Unity horns which were popular about ten years ago. This looks like an excellent hifi horn!

 
There are still some issues with coax drivers. The transition between the cone and the tweeter horn is very steep, and then you will have another discontinuity between the cone and the cabinet (even if the angles match).

There is however Tannoy. Those are known to do coaxial the right way. An if you think to the largest cabinet they use, with a rather large front loaded horn, the concept is quite similar.

An externally hosted image should be here but it was not working when we last tested it.


edit: I took a closer look at your drawing. I see now that it's nothing like the westminster... Mhh.. Food for thought..
 
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Curiosity got the best of me, and I threw together an Akabak model for a tapped horn feeding a Unity horn.

The script needs some work - for instance there's no duct to represent the transition from the tapped horn to the Unity horn. So the script exaggerates the size of the holes in the Unity's throat. (I'm assuming the throat is fed by holes, just like in a Unity horn. Without pics, who knows?!)
An externally hosted image should be here but it was not working when we last tested it.

Published response of the SM 60M. I'm guessing the midrange cone is in a tapped horn, crossed over to the compression driver somewhere around 1200hz. This is complete conjecture, of course. Just basing this on what I see on the spec sheet.

An externally hosted image should be here but it was not working when we last tested it.
Here's the predicted response of a tapped horn feeding a unity horn. This one uses four of the W2 852SH woofers from Tang Band, the same ones I used in my Unity in the car. They have a nice set of params for a unity horn, an underhung motor that reduces distortion, and thanks to their small size, it's easy to get them close to the throat.

This thing has a very VERY small footprint, much MUCH smaller than the SM 60M. Less than a quarter of a cubic foot. The mouth measures just 5" x 5".

You get the general idea: higher efficiency than you'd get from a sealed box, along with some directivity control.

Code:
[FONT="Courier New"]System 'S1'

|================================================= ================================================== =====
|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 =  6.15e-4; |Horn segment 1 throat area (sq cm)
S2 =  7.69e-4; |Horn segment 1 mouth area and horn segment 2 throat area (sq cm)
S3 =  9.60e-4; |Horn segment 2 mouth area and horn segment 3 throat area (sq cm)
S4 = 12.01e-4; |Horn segment 3 mouth area and horn segment 4 throat area (sq cm)
S5 = 15.02e-4; |Horn segment 4 mouth area and horn segment 5 throat area (sq cm)
S6 = 18.78e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S7 = 23.47e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S8 = 29.34e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S9 = 36.68e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S10 = 45.85e-4; |Horn segment 5 mouth area and horn segment 6 throat area (sq cm)
S11 = 154.80e-4; |Horn segment 6 mouth area (sq cm)

L12 = 2.54e-2; |Horn segment 1 axial length (cm)
| driver 100 here
L23 = 5.08e-2; |Horn segment 2 axial length (cm)
| driver 101 here
L34 = 5.08e-2; |Horn segment 3 axial length (cm)
| driver 102 here
L45 = 5.08e-2; |Horn segment 4 axial length (cm)
| driver 103 here
L56 = 20.40e-2; |Horn segment 5 axial length (cm)
L67 = 20.40e-2; |Horn segment 6 axial length (cm)
| driver 103 here
L78 = 5.08e-2; |Horn segment 6 axial length (cm)
| driver 102 here
L89 = 5.08e-2; |Horn segment 6 axial length (cm)
| driver 101 here
L910 = 5.08e-2; |Horn segment 6 axial length (cm)
| driver 100 here
L1011 = 15.20e-2; |Horn segment 6 axial length (cm)




|Parameter Conversions:

Sd = 52.00e-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 'TangBand W2-852'

Sd=13.00cm2
Bl=2.31Tm
Cms=1.04E-03m/N
Rms=0.19Ns/m
fs=195.0000Hz |Mmd = 73.86g not recognised by AkAbak, fs calculated and used instead
Le=0.03mH
Re=3.60ohm
ExpoLe=1

System 'System'

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

Driver Def='TangBand W2-852' 'Driver 100'
Node=2=101=9=17
Driver Def='TangBand W2-852' 'Driver 101'
Node=101=0=10=16
Driver Def='TangBand W2-852' 'Driver 102'
Node=2=103=11=15
Driver Def='TangBand W2-852' 'Driver 103'
Node=103=0=12=14


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

Waveguide 'Horn segment 7'
Node=14=15
STh={S7}
SMo={S8}
Len={L78}
Conical

Waveguide 'Horn segment 8'
Node=15=16
STh={S8}
SMo={S9}
Len={L89}
Conical

Waveguide 'Horn segment 9'
Node=16=17
STh={S9}
SMo={S10}
Len={L910}
Conical

Waveguide 'Horn segment 10'
Node=17=18
STh={S10}
SMo={S11}
Len={L1011}
Conical

Radiator 'Horn mouth'
Node=18
SD={S11} [/FONT]
 
I should add this from Tom Danley when he posted the CAD drawing with it, "You can see there are two types of LF drivers shown (the two types that are used in the different versions). The outermost holes / duct are the outlets for a Tapped horn section used in one model. At the rear is the hf and mid source"
 
Aha! You've explained it then.

So there's a coupling chamber in front of the *coaxial*, but the midrange cone of the coaxial is NOT loaded by a tapped horn.

The cone of the woofers ARE loaded by a tapped horn, and the holes near the mouth are the exit points.

This also explains why Danley couldn't build this Synergy Horn until recently. (According to the thread on prosoundweb, this is an old idea he had, but there hasn't been a driver available which was suitable until now.)

If Danley had used something like an eight inch coaxial, a notch would appear in the response because of the distance from the edge of the woofer's cone to the apex. For instance, with an eight inch driver a notch would appear somewhere around 844hz. (Speed of sound / 4" / 4 /) It's 4" and not 8" because you measure the distance from the edge to the center.

But with a 5" cone the notch moves up to 1350hz.

So that's the key. Even a 6.5" cone is a little bit too big. The cone *really* has to be small for the coax to work at the apex.

Very clever!
 
It would be nice to know a non-2007 price on it. I don't think there will be any way around it.

The woofers could be another story. It would be nice to bump the horn and woofer size up a little to push the lowend a tiny bit further down.
 
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OK, I'm getting something like this,

0 Voltage 1 Resistance 2

2 EQ
_ Comp Rear _ Comp Driver _ Comp Chamber _ WG1 _ WG2 _ WG3 _ WG4 _ Radiator (Mouth)

2 EQ
_ Mid Encl. _ Mid Driver _ Mid Chamber _ Mid Port X(x4)

2 EQ
_ Low Encl. _ Low Driver(x2) _ Low Chamber(X2) _ Low Port(x2) X(x2-4 total)

_ Low Tap X(x4)

With the colors indicating node linking, and "_" indication an un-numbered node.
 
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I was thinking something a little different (maybe). Hard to tell, but that waveguide looks to be less than 90 degrees. I envisioned that the waveguide has an insert at the apex, that fits into the compression driver mouth, and swages it down from 90 to say 60 degrees. In this way, the midrange cone does not form part of the waveguide. It is instead radiating into a separate chamber that has entry holes into the waveguide, ala Unity style. This would allow the entry holes to be placed near the apex. Of course a more elaborate tapped horn setup could be used too.

Sheldon​
 
This is the WIP Akabak script I have going. It is built off of Mavo and JLH's old Unity scripts. It follows the tree I put up in post #10.

All inputs are placeholders, but it should streamline working them out. Maybe. ;)

The makeup of the coaxial is in question, so there may be another chamber to add on the compression side. Also, I do not know if the Low Driver taps are tapered. They don't appear to be, but if they are the ducts will have to be switched to WGs. NBD.

Seems sound to me, but I have been looking at it for too long.

Code:
System 'Trial A'

Def_Driver 'CompDriver' | (temp)BMS 4552ND compression driver
Sd=15.52cm2
Bl=6.21Tm
Cms=140E-06m/N
Rms=0.40Ns/m
Fs=850Hz
Le=0.09mH
Re=6.20ohm
ExpoLe=0.618


Def_Driver 'MidDriver' |(temp)Misco Speakers Model KCN5FD 5" mid

Sd=63.62cm2
Bl=5.85Tm
Cms=1.28E-03m/N
Rms=0.27Ns/m
fs=101.336Hz
Le=0.42mH
Re=7.2ohm
ExpoLe=0.618


Def_Driver 'LowDriver' |(possible:check parameters)Faital Pro Model 8PR200 8" woofer

Sd=199.0cm2
Bl=17.11Tm
Cms=0.21E-03m/N
Rms=0.27Ns/m
fs=70.0Hz
Le=0.55mH
Re=5.1ohm
ExpoLe=0.618


Def_Const | Unit is cm
{
Mc_Len=0.865e-2; | Front Mid Chamber length
Mc_Dia=9.0e-2; | Front Mid Chamber diameter
Mp_Len=0.635e-2; | Mid Chamber Port length
Mp_Dia=1.38e-2; | Mid Chamber Port diameter

Lc_Len=1.5; | Front Low Chamber length
Lc_Dia=1.9; | Front Low Chamber diameter
Lp_Len=.2; | Low Chamber Port length
Lp_Dia=2; | Low Chamber Port diameter

Encl_Len=25; | Low Driver Enclosure length
Encl_Vol=10; | Low Driver Enclosure volume (liters)
Encl_Area = Encl_Vol / Encl_Len;


Rt_Len=5; | Low Rear Tap length
Rt_Dia=2.5; | Low Rear Tap diameter


Rg=0.08e-0; |Amplifier output impedance (ohms)


CD_XO = .5; |Comp Driver Crossover 

MD_XO = 11.8e-6; |Mid Driver Crossover 

LD_XO = 1.0e-3; |Low Driver Crossover 


S1 = 1.552e-4; |WG1 throat area Waveguide Bridge(sq cm)
S2 = 5.07e-4; |WG1 mouth area and horn segment 2 throat area Mid Chamber Tap point(sq cm)
S3 = 99.01e-4; |WG2 mouth area and horn segment 3 throat area Low Chamber Tap point(sq cm)
S4 = 1038.48e-4; |WG3 mouth area and horn segment 4 throat area Rear Tap point(sq cm)
S5 = 2141.93e-4; |WG4 mouth area and horn segment 5 throat area Horn Mouth(sq cm)


L12 = 2.25e-2; |WG1 axial length(cm)
L23 = 7.0e-2; |WG2 axial length(cm)
L34 = 20.25e-2; |WG3 axial length(cm)
L45 = 7.93e-2; |WG4 axial length(cm)


CDRC_Vol = 0.08e-3; |Comp Driver Rear chamber volume (litres)
CDRC_Len = 0.84e-2; |Comp Driver Rear chamber average length (cm)
CDTC_Vol = 0.75e-6; |Comp Driver Throat chamber volume (cc)
CDTC_Area = 15.52e-4; |Comp Driver Throat chamber cross-sectional area (sq cm)

CDRC_Area = CDRC_Vol / CDRC_Len; |Conversions for CompDriver
CDTC_Len = CDTC_Vol / CDTC_Area;
}
Driver 'D1' Def='CompDriver' Node=10=0=51=52

Duct 'CompRearChamber' |Comp Driver rear compression chamber
Node=50=51
SD={CDRC_Area}
Len={CDRC_Len}
Visc=0

Duct 'CompFrontChamber' |Comp Driver front throat chamber
Node=52=110
SD={CDTC_Area}
Len={CDTC_Len}
Visc=0


Enclosure 'E2' Node=60 Vb=1.8L Lb=5cm

Driver 'D2' Def='MidDriver' Node=0=20=60=61

Duct 'Mid_Chamber' Node=61=62 dD={Mc_Dia} Len={Mc_Len}

Duct 'Mid_Port1' Node=62=120 dD={Mp_Dia} Len={Mp_Len} 

Duct 'Mid_Port2' Node=62=120 dD={Mp_Dia} Len={Mp_Len}

Duct 'Mid_Port3' Node=62=120 dD={Mp_Dia} Len={Mp_Len} 

Duct 'Mid_Port4' Node=62=120 dD={Mp_Dia} Len={Mp_Len}


Duct 'E3' Node=70=81 SD={Encl_Area} Len={Encl_Len} |Low Drivers Rear Enclosure

Duct 'Rear_Tap1' Node=81=140 dD={Rt_Dia} Len={Rt_Len} 

Duct 'Rear_Tap2' Node=81=140 dD={Rt_Dia} Len={Rt_Len}

Duct 'Rear_Tap3' Node=81=140 dD={Rt_Dia} Len={Rt_Len} 

Duct 'Rear_Tap4' Node=81=140 dD={Rt_Dia} Len={Rt_Len}

Driver 'D3a' Def='LowDriver' Node=30=31=70=71

Duct 'Low_ChamberA' Node=71=73 dD={Lc_Dia} Len={Lc_Len}

Duct 'Low_PortA1' Node=73=130 dD={Lp_Dia} Len={Lp_Len} 

Duct 'Low_PortA2' Node=73=130 dD={Lp_Dia} Len={Lp_Len}

Driver 'D3b' Def='LowDriver' Node=31=0=70=72

Duct 'Low_ChamberB' Node=72=74 dD={Lc_Dia} Len={Lc_Len}

Duct 'Low_PortB1' Node=74=130 dD={Lp_Dia} Len={Lp_Len} 

Duct 'Low_PortB2' Node=74=130 dD={Lp_Dia} Len={Lp_Len}


Resistor 'Amplifier Rg' |Amplifier output impedance
Node=1=2
R={Rg}

Resistor 'CD_XO'
Node=2=10
R={CD_XO}

Capacitor 'MD_XO'
Node=2=20
C={MD_XO}

Coil 'LD_XO'
Node=2=30
L={LD_XO}


Waveguide 'WG1'
Node=110=120
STh={S1}
SMo={S2}
Len={L12}
Conical

Waveguide 'WG2'
Node=120=130
STh={S2}
SMo={S3}
Len={L23}
Conical

Waveguide 'WG3'
Node=130=140
STh={S3}
SMo={S4}
Len={L34}
Conical

Waveguide 'WG4'
Node=140=150
STh={S4}
SMo={S5}
Len={L45}
Conical

Radiator 'Horn mouth'
Node=150
SD={S5}
x=0
y=0
z=0
HAngle=0
VAngle=0
 
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You will want to add the "e-2" back to length/diameter, and "e-3" to volume in the woofer section. Don't know where it went to in this version. :rolleyes:

It was late.

You may also want to use SD instead of dD in some of the ducts. I didn't feel to compelled to get to super user friendly with it at this point.
 
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It's like this:
Noname-7.gif


86 are the ports from the Mid Chamber into the waveguide.

Thanks. That's what I thought from the diagram, but didn't have time to read all the descriptions.

As I understand the tapped horn, there is a chamber around the back of the cone, and that chamber is connected via ports to the waveguide, in order to extend LF response. So the version in the figure is not a tapped horn, but a regular unity. No?

Sheldon
 
Sheldon,

Fig.7 would be a 2way Synergy horn like say the SM-60M. A 3way like the SM-60F, would add a set of woofers with the enclosure interior tapped into the waveguide.

They are a step above the Unity design. There are a few small design parameter changes, and additions compared to the original patent. The end result is an emphasis on phase coherency in the Synergy horns.
 
There is no “Tapped Horn” per se in those new Synergy horns. In figure 7 the highs come from the compression driver and the mids come from the cone of the coax. The extra woofers tap into the horn just like all the other Synergy horns and are bass reflex loaded back into the horn.

The term tapped horn is used loosely in the fact that a Unity/Synergy horn is a form of tapped horn because it taps into the side of the horn and not at the throat. I believe nothing was made into something and got carried away.
 
Cheers!
Just found something that could be of interest for you, a type of tapped horn combined with an unity, maybe you have already seen, take a look:

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.


Unfortunately I have no more information about these designs, but probably someone of you could tell us more about those great builds?!
Would be interesting to know what drivers have been used to run these unity/tapped horn!?
gzg
 
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