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10" Tapped horn project

post #1 of 25
Thread Starter 
I have 2 drivers that I would like to use in a tapped horn and managed to come up with this design,

The driver parameters are as follows,
FS: 27.7Hz
Qms: 5.6
Vas: 33L
Cms: .22mm/N
Mms: 150g
Xmax: 23mm
Xmech: 32mm
Sd: 325sqcm
Vd p-p: 1.5L
Qes: .53
Le: .46mH
Z: 8ohm
Bl: 12Tm
Pe: 700W
Qts: .48
1WSPL: 83.3db

Im having trouble with the hump at 30hz, and have no idea of how to fold it, any tips?

My other question is regarding sensitivity. Is there any advantage in this design over a ported box?
post #2 of 25
your tapped horn is...backwards! :-)

s1 is the small enclosed end.

I suppose there is no reason why the large end couldn't be enclosed, it is just atypical.
post #3 of 25
i played around with it for a bit and the driver has no motor, which is why you ended up with a horn that is backwards.

suggest that you find another driver if horns are in your future. :-(
post #4 of 25
Thread Starter 
Hi LTD02,

Just was told that the specs for the driver are incorrect. They are for a dual 4 ohm version, mine are single 8 ohm. Accordingly the BL should be more like 24 and QES .27.

Does that make a difference?

Cheers, Beau.
post #5 of 25
that would make quite a difference...give it another shot!
post #6 of 25
Thread Starter 
Hmmm, cant seem to make it look any good at all now, been playing with sliders for hours...
post #7 of 25
Thread Starter 
Tried a new setup with some older caraudio subs I have, thoughts? 2 driver in series.

Ang=0.5 x Pi
post #8 of 25
"Hmmm, cant seem to make it look any good at all now, been playing with sliders for hours..."

are you sure that you have entered the driver parameters correctly? changing bl will change qes, qtc, fs, vas, and rms. do you have the spec sheet with the t/s parameters on it? what driver is it that you are working with?
post #9 of 25
Thread Starter 
The drivers are acoustic elegance av10h-8 subs. The only specs available are for dual 4ohm versions in series, mine are single 8 ohm. I dont really understand how the parsmeters relate to eachother.
Link to specs.

post #10 of 25
Thread Starter 
The other drivers which I seem to be able to get a decent response out of are these, Audiobahn Alum12s
Le 1.61mh
Fs 21hz
Qms 3.46
Qes .39
Qts .35
Vas 117 litres
Re 2 x 5.4ohm
Xmax 16mm

Vcoils in parallel and 2 drivers in series is the setup above.
post #11 of 25
ah, well, that driver should work and you could enter either the 4 ohm specs from the website or

this version which adjusts for the coil wiring. motor is bl^2/re so that is what goofed you up.

if you want to, try this.

FS: 27.7Hz
Qms: 5.6
Vas: 33L
Cms: .22mm/N
Mms: 150g
Xmax: 23mm
Sd: 325sqcm
Qes: .53
Re: 5.8ohm
Le: .92mH
Bl: 16.97Tm
Qts: .48

but both should model exactly the same. the key is if using the dual 4 ohm, resistance will double, but bl only goes up by root 2 (1.414) and inductance should scale with resistance so 2x resistance = 2x inductance.
post #12 of 25
after a few minutes I gave up with the tapped horn too.

it works in a front loaded horn, but it is extremely sensitive to parameters. I wouldn't suggest it for a first horn attempt.

sometimes it helps to have a "starting point". you can use that one to increase length and so on, but again, it is REALLY sensitive to each adjustment and that makes it very difficult to say with certainty that it will translate once built.
post #13 of 25
Thread Starter 
What about the second driver? The results I came up with seem to be pretty good.
Thanks for your help so far wink.gif
post #14 of 25
well...post 'em up and let's see what you've got there. :-)
post #15 of 25
Thread Starter 
OK results,

The thing im still not sure of is the arrangement of the voice coils. These drivers are also duall voice coil and I don't know if the specs are with the coils in series or not. Is there any way to tell?
post #16 of 25
it will have no effect on the performance in the horn.

that is what i was trying to get at earlier. if you wire and measure the t/s for the coils in series, you get one set of numbers, measured in parallel, you get another set of numbers, but...both will perform identically in the horn, except for the change in sensitivity of course.
post #17 of 25
your tapped horn is looking pretty good...

2 pi space may give a more accurate translation of performance...
post #18 of 25
s2 is the area in front of the driver and divided into sd gives the "compression ratio" of the horn. at 500/425 your compression ratio is only 1.25. you could increase it by reducing s2 and that may help smooth things out a little. compression ratios of less than about 3 are pretty conservative.
Edited by LTD02 - 10/6/13 at 12:09pm
post #19 of 25
Thread Starter 
Had another go. Got a bit more efficiency out of it but couldn't really smooth it any further. Size is just under 1000l smile.gif

Now onto folding, another headache. Any tutorials on that?
post #20 of 25
have you seen lilmike's tutorial? http://www.avsforum.com/t/1212465/simple-tapped-horn-tutorial-using-hornresp

also, for the lengths, using "par" as the expansion rate may better reflect results of a bass horn as it would typically be folded.

for sensitivity, adjusting voltage to provide 1w into the re of the driver in place of 2.83 v may be better.

for space, 2.0 is probably a little better for making comparisons.

that is a lot of wood for such a modest horn and a first attempt...
post #21 of 25
here is one that we folded up using a simple constant expansion rate that is about as big as what you are talking about. should provide some idea of how it can be done. i hope. :-)

post #22 of 25
Thread Starter 
Thanks LTD02. I have had to reduce the size of the box a little. Im planning on putting it inside an old timber dresser so I have fixed dimensions to work with.
Its around 38x118x180cm after the external skin is accounted for. Thats around 800 litres.
post #23 of 25
Thread Starter 
Results, 2 x 12inch drivers.

I hate folding.

post #24 of 25
"Its around 38x118x180cm"

I'm an American...I don't know wtf a centimeter is. :-)~

minor comment...in your model, s4 is smaller than s5. s5 should be larger if the mouth is expanding.

larger comment...keep at it, sometimes it takes a few complete reworks until the right solution pops out.
post #25 of 25
Just a couple quick comments... dealing with 10" drivers, in a pair, you need as much Xmech as you can possibly find to do anything in a tapped horn below 20Hz worth doing. Look for as strong a cone as possible, the smaller the Vas the better (to keep the box size down), the closer you can get to 0.3 Qes the better.

I wouldn't use the AE 10" based on those specs. If they measure better, great, but that's the key - you need confirmed, measured parameters to do a tapped horn well. Sometimes you can get by if the published specs are close to reality.

For 10s that should work well in a TH, I have a list of them in my signature build thread. You're better off with 12s though if you're intent on going below 20Hz.
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