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hornresp's "multiple speakers" simulation


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I've been asking myself if any of you have ever used this feature of hornresp and if it is any good. Here is a comparison of a sub design I'm working on; 1 vs 2 cabs.


That improvement looks really good to me and with 3 cabs the response is ± 1db from 30-200Hz within this simulated environment, which would be stellar. I'm wondering if cabs do perform similarly when stacked and if this feature could be used (trusted) to get a remote impression of what an array of speakers would measure like.

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For non horn loaded speakers each doubling the number of speakers with each speaker driven by the same power when they are within 1/4 wavelength should be +6dB.  You get +3dB for a doubling of the input power and you get +3dB from an increasing in effective radiating area increasing the efficiency.  For horn loaded speakers there can be the additional effect of increasing the effective mouth size which can give more low end extension and efficiency if the mouth was undersized.  Notice how the bottom end is boosted and ripple reduced in the predicted acoustic output of labhorns in multiples; 

One horn:


4 horns:


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So I guess you're trying to say that this feature in hornresp should be pretty accurate assuming perfect conditions like single horn mouths stacked together etc?

My cab would probably behave differently as it is a mirrored design and has two horn sections, so if you stack two you'll end up with only stacking half the horn mouths together.

It also got decent baffle area so there should be some gains to be made in the upper register, which hornresp does not calculate.

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There is some disagreement on whether horns achieve a lower corner in stacks. Most of the " good" measurement data I've seen presented points to no more gains than with direct radiators. Increasing mouth area doesn't lower extension by itself. In fact it raises tuning unless the horn volume AND length are also increased. There was a big discussion about this on DIYaudio forum years ago with data but I can't remember the name of the thread. I recall another big discussion on Prosoundweb years ago as well.


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On 8/5/2019 at 3:01 PM, kipman725 said:

As long as the mouths are within 1/4 wavelength they should act as if they are stacked together.

That's good to know!


1 hour ago, Infrasonic said:

From what I have read, I thought it was that tapped horns will not benefit with additional extension when used in stacks. However, front-loaded horn bass systems will.


I wonder how the SKHorn type of cab would behave (since my design is similar). Probably the same as a BR would? Hornresp shows much more gain in the lower octave thou; the horn contributes to the output down to about 45Hz (where the horn part crosses 95db voltage sensitivity).

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I'm not familiar with the feature, so I am not inclined to comment on it.

However in general, Hornresp reports output in terms of *acoustic power* and not *SPL*, which is important where directivity is not omni-directional (or the 2pi equivalent, as it were).  When you start stacking large cabs, a few things are going to happen regardless of the type of cabinets.  First is that directivity will typically increase for progressively lower frequencies as the size of the array grows.  This means that at a particular location and frequency, SPL may be quite a bit higher or lower than the dB value indicated by Hornresp, for better or worse.  When indoors and in smaller rooms, the acoustic power may be more important than the anechoic SPL output anyway.  Second is that the co-location of multiple sources will tend to boost power output and efficiency, but this depends on the distance(s) between sources and the wavelength.  Because lower frequencies have longer wavelengths, arraying will tend to boost lower frequencies more than higher frequencies.

In short, don't confuse SPL output, which depends on directivity, with acoustic power output, which does not and which is what Hornresp generally shows.  I'm inclined to doubt that a horn stack will increase in LF extension beyond what a single horn can do.  Can it increase output and efficiency down load?  Yes, absolutely, but that's not the same thing.

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