Exponetial horn gone very wrong

[Piper]

Thanks very much for all your help, i increased the troat size and resealed every thing. These were my final results.



If it wasnt for that huge dip at 115Hz i would have been happy with it. But think im gonna call it a day on this one and start work on a larger coiled horn, no iso loading this time and some more efficent drivers

[Rademakers]

and some more efficent drivers

The efficiency isn't the significant factor when it comes to horns. You can easily have a horn, loaded with a 89 dB/W/m driver giving a higher SPL than a 99 dB/W/m driver, as long as the other T/S-parameters are right.

Btw: Mmd is just in grams

But think im gonna call it a day on this one and start work on a larger coiled horn, no iso loading this time

Sounds like a good idea

Mvg Johan

[footstony]

I have had problems with throat size calculations too.

I use Bruce Edgars version. Same, just less problems with units!

St= 0.8 Fs Qes Vas

where Vas is in cubic feet
St is in square inches
and Fs is the FLARE FREQUENCY

Regards Philip

[Piper]

What are the mian T/S-parameters i should look for in a horn loaded speaker ?

Obviously i would assume the need for a large Vas and Qts.?

[footstony]

I would look for drivers with the lowest Qes. This will give the horn a higher mass rolloff. As you can see by the throat equations, bigger qes and Vas also means a bigger throat and therefore a shorter horn.
small Vas will give a longer horn. A horn needs to be at least 1/4 of a wavelength long to work, longer is even better.
Regards Philip

[Rademakers]

If your making a horn that has to do it on it's own (instead of being designed to work best in multiples), while it's limited in size, it's better to use a driver with a Qts that isn't too low (low would be 0.22 or alike).

In such a case your looking for a driver with a Qts between (about) 0.27 - 0.35 orso and a BL that's normal to high (depends on diametre used) but not exceptional. Very important (espescially) in this case is the Xmax.
More Xmax means more output potential. This translates in higher SPL and/or more low end extension. Look at drivers with at least around 7 mm Xmax, to get low end at desired levels. Serious drivers will have plenty Xmax (say 12 mm+)

If you're making a horn, design it to be used in 1/4 or even 1/8 th space if possible.
Basshorns that work good on there own generally have a large rear chamber.
The bigger the Sd, the shorter you can make the horn for the same cut off, so it's better to use two drivers next to each other rather than isobaric.
The smaller the Sd, the bigger the compression ratio can be, but 4 would be the maximum and rather look for a driver that works good already with a compressionratio of 2 or less.
Simulate the hornmouth to be 6 or 7 times bigger than Sd. Than gradually work it to become smaller, using the compare function to see what the real minimum moutharea is.

Try to simulate with many drivers, some drivers just don't work well, despite good looking T/S-parameters. It will make you understand Hornresp and horn design basics much sooner tho.

BTW: ES is in Volts. So 2,83 (@8 ohm) equals 1 Watt per driver. Doubleclick to get a calculator that translates the power (in Watts) to Volts.

Mvg Johan