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Old 7th January 2012, 02:48 PM   #1291
tb46 is offline tb46  United States
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Hi David and all,

It's great that you found where the difference was. I found a good source with sound power level and sound pressure level calculators (engineeringtoolbox.com):

Adding Decibels

It still confounds me too, that two horn-style cabinets mounted mouth next to mouth (in fact creating a new mouth with twice the area) would not show an additional increase in the SPL owing to the increased radiator size. Maybe the response peak that results from the foreshortening and the undersized mouth is reduced when the mouth and the horn cross-section are practically doubled. But this should also show in multi-driver cabinet v. single driver cabinet comparison.

I would also expect a slight increase in effective length for the two mouth model, and a slight difference in the directivity.

Some of the measurement differences from theory may come from the different boundary conditions.

Thanks to all for working so hard on this problem.

Regards,
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Old 7th January 2012, 05:14 PM   #1292
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Quote:
Originally Posted by Dag Johansen View Post
I remember mr.Danley talked about the soundwaves coming out of the horn not as a flat wave but more like a sphere/bubble.
Wouldnt this make the horn longer than its physical dimensions?
And because of that, make 4 coupled TH's even longer?
Or does it only apply to FLH's?

In any case, would this difference show up in a impedance-sweep of one and four?

Dag
The TH horn acoustical length is basically the same as the physical path length.
The length does not change in multiples.
FLH do not "grow longer" in length in multiples, but the increased mouth area being shared does increase the LF output slightly compared to the HF.

This effect does not happen with TH or BR cabinets.

Last edited by weltersys; 7th January 2012 at 05:28 PM.
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Old 7th January 2012, 06:10 PM   #1293
Mark Kravchenko --- www.kravchenko-audio.com
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Quote:
Is a "Tapped Horn" really a horn in the bottom octave it operates in?
(I don't think so)
DJK

A tapped horn is not a classical horn. It is a resonant system in the lower end of it's response. You see that when you are trying to design one and you end up with a saddle shaped response. The lower bump is a product of the location of the driver in the tapered line and the amount of air available. It can be quite a boost in the efficiency.

But having compared all of the normally available boxes in a very controlled manner I can say that I prefer the cleaner sound of a true front loaded horn. A tapped horn has a rather distorted character reminiscent of a poorly made vented enclosure.
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Old 7th January 2012, 07:20 PM   #1294
Djim is offline Djim  Netherlands
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Hi Djk,

I think you are right Djk, TH's don't seem to work down low as a horn (pipe). I think if HornResp had the ability to have variable frequency impulse responses (also known as time-stretched Pulses, although used differently in this context) instead of the fixed one, you could show the difference between the direct signal from the driver and the amplified signal of the horn (pipe). It would not surprise me to see that down low the direct signal becomes more prominent after the horn (pipe) start to loose its efficiency.

Last edited by Djim; 7th January 2012 at 07:28 PM.
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Old 7th January 2012, 08:01 PM   #1295
Djim is offline Djim  Netherlands
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Originally Posted by Djim View Post
also known as time-stretched Pulses, although used differently in this context
Edit: sorry, I think it is called Pitch shift instead of time-streched.
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Old 7th January 2012, 08:28 PM   #1296
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Default Historical perspective

This is an interesting short thread that predates Danley's introduction of the tapped horn. It's fairly clear to me he wasn't thinking about it at the time, since he does not make reference or even talk about the idea. But this thread does actually start down that road. It talks about the nature of basshorns being resonant because they are almost always acoustically small even if physically large. There is a link to an article about modifying a horn by placing expansions at key places along the line in order to influence the reactive ripple. Historical perspective:
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Old 7th January 2012, 11:51 PM   #1297
Djim is offline Djim  Netherlands
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Many thanks Wayne,

Your link with Tomís comparison comes exactly on the right moment for me.
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Old 8th January 2012, 02:57 AM   #1298
jbell is offline jbell  United States
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Originally Posted by Djim View Post
Many thanks Wayne,

Your link with Tomís comparison comes exactly on the right moment for me.
back to flutes and clarinets????
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Old 8th January 2012, 03:55 AM   #1299
Djim is offline Djim  Netherlands
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Originally Posted by jbell View Post
back to flutes and clarinets????
Jbell, for the first time I began to see the relation between the local fanfare and my neighbour who hates them; 'flutes and clarinets' and 1/4WL dipole with 'balun' and mirror element. Still following
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Old 8th January 2012, 12:26 PM   #1300
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Originally Posted by David McBean View Post
Hi Art,

Not unless I make a special adjustment, just for multiple tapped horns :-).

Kind regards,

David
Hi Art,

It seems that it will not be necessary to make any special adjustment for multiple tapped horns - the proposed new multiple speakers response calculation method appears to correct the problem automatically :-).

Kind regards,

David
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