Driver placement in horn?

[Rademakers]

Hi,

Is there any rule of thumb or guideline, of what to aspect for different driver placements along the horn length axis (i.e. positioned at throat, 1/3 down from throat, 1/2 way, 3/4 way, etc.).

This is my impression up to this point: When you place the driver nearer to the horn mouth the compression ratio "seen" by the driver decreases. In the case of a very large horn the compression ratio would eventually become so small that the driver wouldn't effectvely load the driver anymore. Based on this I would expect a bump around it's 1/4 wavelength resonance and then a dip higher up that becomes larger as the driver is positioned closer to the mouth. What this (if right) would do to the impedance, frequency based excursion and phase repsonse is to far beyond my grasp but I would still like to know

Any thoughts?

Regards Johan

[SubSoniks]

Have a look here, the mathcad scripts are designed to model just this and more.
Jake

[Rademakers]

I was somewhat afraid someone was going to mention that program

I've tried to work with it in the past (when it was still free) without (any) results. Akabak seems a bit more easy to work with, do too more examples floating on the web and Hornresp's conversion ability. Could it be used too and if so is there anybody who wants to shed a light on the system needed?

Wkr Johan

[SubSoniks]

I didn't find the mathcad scripts hard to work with but have been struggling with Akabak.
Moving the driver away from the throat can smooth the response ripples according to the mathcad models.
i have been trying to model my hybrid horn here http://speakerplans.com/forum/forum_...TID=12655&PN=2

Jake

[cowanaudio]

G'day Johan

This series of plots shows the effect of moving the driver from the throat to the mouth. This was a 70 hz horn with a small mouth. You will see the 1/4 wave cancellation notch move down in frequency as the driver moves further from the throat. This is the biggest problem with moving the driver from the throat. The LF corner does not change much. This 1/4WL notch can be used to good effect, say in a Unity design, where it attenuates out of band distortion products from the low frequency drivers. It can also be used to remove the first peak in a tapped horn design.

Driver location in these plots is (from memory) throat-1/3-1/2-2/3-mouth.

Cheers

William Cowan