HD15 Hornresp modellling

Hopefully a quick question for someone please:

I'm trying to model the HD15 in Hornresp to tweak the size of the box, I want to make it the same size as some 18" reflex boxes I use for ease of stacking.

The problem I have is deciding what type of horn flare to model it as.  It looks much more rapid than most horn flares, even taking into account all the flare is on one side.

I'm guessing someone else has done this already, so if you could let me know what parameters you used please I'd be grateful.  Thanks.

As I can't work out how to model the flare as a single curve, I've been trying to use multiple conical segments as that's how I'll probably construct it.  Sticking with the original measurements for now I'm getting CIR > 1 warnings for my final flare segment because of the speed of expansion.  Will this actually affect my simulation results significantly?

I think I've got all the dimensions right  (Including large throat and rear chambers) but the results don't quite seem right, eg the diaphragm displacement is quite large even within the horn passband (2mm @ 150Hz, 1W input).

If anyone has modelled the HD15 in Hornresp and can do a screenshot of the input params please it would save me a lot of frustration.  Thanks in advance.

As I can't work out how to model the flare as a single curve

Post us your input screenshot and wel see whats wrong. I modeled an exponential approximation of it,and it looked similar to the HD15Plot.

Ensure driver parameters are inputted in the right order,ensure cubic centimetres or litres inputted..etc

Note that on finite horns the loading differences arent so apparent.

With one box in 2pi space the excursion can still be high,the horn is too small to support the long wavelengths.

Try modeling an infinite hornor HYPEX horn and compare the acoustic impedence and excursion plot etc to realistic horns.

Edited by tb_mike

the axis of the throat doesn't matter it's just the smallest area the air has to travel through

in the case of the HD15 the throat area is 544.8cm^2

the front chamber is any space between this and the driver including the volume of air contained within the cone itself

on the HD15 the easiest way to figure this out is to use pythagoras' theorum to work out the area of the triangle

ie. you know the size of the baffle 42cm and the distance away from the back panel at the top of it is 20cm

assuming a right angled triangle the sq root of 42^2 - 20^2 gives 36.9cm or the height up the back panel

20*36.9=738 divide that by 2 and you have the area of that triangle or 369cm^2

multiply that by 47.2 and you have 17416.8cm^3 or 17.4 litres

add on 2.5l for the volume of the cone and a rough guess of 20litres for the front chamber would be about right

That sim also comes fairly close at the low end to the measured response.

Cheers, good to know I managed to get the sim somewhere near right.  Been playing with some variations on the original HD15, slightly deeper cabinet for a longer path etc.

I'm not exactly sure, but I think 1xpi is appropriate if you use multiple cabinets together (one HD15 wouldn't be very useful).  For modelling most situations you are right about using 2xpi.

Anyone else care to correct?