Tapped Horn behavior

[djk]

The equivalent for AkAbak:



a1 = 500e-4; |Area at throat (cm^2)
a2 = 881e-4; |Area at rear of driver (cm^2)
a3 = 3100e-4; |Area at front of driver (cm^2)
a4 = 3200e-4; |Area at mouth (cm^2)
l1 = 20e-2; |Distance from throat to rear of driver (cm)
l2 = 250e-2; |Line distance from rear of driver to front of driver (cm)
l3 = 10e-2; |Distance from front of driver to mouth (cm)

[MarjanM]

Well you surely dont need 24 grand for 6 TH115 :-)
Just a bit more that half of that amount.

[screamersusa]

After some interesting failures, and trying to find a bigger shoehorn, here's the one I'm building to test this weekend.
I gave up on the TH-115 style because unitll I learn how to deal with compression in horn resp It's a waste of time.
I.E. small opening in throat, variable throat using s1 and s2.

I'm using the inductor.
Hopefully it will make a decent PA box.
21 wide
36 deep
about 34 high or less (I'm still working out the last fold.)
I was going to taper everything so no parellel surfaces but I'll wait untill I get the compression thing figured out.
It's kinda looking like an old DJ box, sorta scoopish.

s1 724
s2 834.39
s3 1625
s4 2190.02
l1 24.40
l2 141.9
l3 40.20
l4 24.40

At 2.83v , the sim says....
99 db at 40hz
102-103db from 45 to about 140hz.

Oh yeah.....the driver is mounted INSIDE the cabinet so you don't need to order a hundred dollar grille from california. Stock 15" grille is fine. Good for DIY budgets. Will post pics next week.
This is frustrating and fun.....tylenol time Gnite.

[AndrewT]

a 15inch driver inside a tapped horn does not need a cabinet that is 24inches wide.
Try reducing this to 17 or 18inches wide (just enough to get the driver chassis inside).

[djk]

And you will lose a bunch of gain with the small mouth.

The TH115 has almost 3X Sd for mouth area, make it smaller and it will become less efficient.

[AndrewT]

what small mouth?
55*40=2200cm^2~=2.9*Sd.
or
48*40=1920cm^2~=2.6*Sd.

[djk]

Scripts with the cone coupled to a cavity firing into a throat smaller than Sd. The big one is about 50% bigger than the small one, for 2.7dB more gain at 40hz and only 1dB above there.

|15" scoop?

Def_Driver 'Dr1'
|Eminence 15"
Sd=881cm2
fs=42Hz
Qes=0.41
Qms=6.82
Vas=160L
Re=5.31ohm
Le=0.92mH
system 'S1'

Driver Def='Dr1' Node=1=0=3=4

Waveguide 'W2'
Node=3=4 STh=650cm2 SMo=1600cm2 Len=160cm Conical Vf=28L

Horn 'H1' Node=4 STh=1600cm2 SMo=1800cm2 Len=35cm Conical

|15" scoop?

Def_Driver 'Dr1'
|Eminence 15"
Sd=881cm2
fs=42Hz
Qes=0.41
Qms=6.82
Vas=160L
Re=5.31ohm
Le=0.92mH
system 'S1'

Driver Def='Dr1' Node=1=0=3=4

Waveguide 'W2'
Node=3=4 STh=650cm2 SMo=2400cm2 Len=200cm Conical Vf=20L

Horn 'H1' Node=4 STh=2400cm2 SMo=2600cm2 Len=30cm Conical

[djk]

Going back to the datasheet, the TH115 looks to be about 2845cm^2, or 3.327X Sd.

[screamersusa]

Starting construction today on the "Bull" as I need 4 subs fast.
I have another one named the B.I.T.C.H. That I can take my time on. (Bass Intense Tapped Compact Horn).

The 22.5 x 19 mouth doesn't seem like much of a diffrence, but it gets a small box lower in freq without loosing much DB. Making the path from driver to mouth longer seems to cost more db then shortening it and making the mouth a tad bigger.

The goal is a utility bass bin using an existing driver that may be semi forgiving on driver types. Has enough output for live sound in small to medium venues (having 45hz coming out of it effortlessly is quite an improvement over direct radiators).
Is fairly easy to build while limiting parallel surfaces and excessive bands in the horn path. It has to be vertically stackable and fit under my 22.5 " top boxes.
The hard part. It has to be small enough to fit 4 in a van or more importantly 4 on one end of a standard 5x8 trailer.
It's getting closer to 36x32x24 a I am laying out the last horn section today.

I'm building the first one for size, so the driver is mounted inside the mouth. The version with the driver inside the box is looking like it's about 4 inches taller height and 2 inches shorter depth.
It's a compromise utility box.

From What I can tell, after playing with the theoretical one, the real TH-155 is a complex beast so I won't even try to build one.

[screamersusa]

34x34x24 final size of prototype.
Will finish tonight and test against a double 18 tomorrow.

Tip for physical horn layout mock up.
Home depot has 3/4 inch foam panels. They are about 14.5 x 48 inches and come 6 per pack. Runs about 7 bucks for a pack.
Makes working out angles and clearances a pleasurable experience.
One pack is probably more than enough for one box that has been conceptualized roughly on paper. Took 3 pcs for this one.