You don't need a full exponential expansion to obtain the loading characteristics.
Here's an example of a truncated expo horn of 25cm length.
This ao. explains why some people have used the JBL 2380 from <500Hz.
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Found this. I read it and liked that it was not only math... wanted to understand a bit more of the impedance aspects...
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
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https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
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That may be interpreted arbitrarily
I do think loading is important, perhaps not so much around 1000Hz, but definitely around 500Hz.
Maybe you have some OS horns laying around to test with the HF1440 from 500Hz.
One may wonder why manufacturers specify a lower usable limit at all, if this is irrelevant.
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the end of this datasheet specifies power handling as a function of frequency:
ftp://ftp.renkus-heinz.com/Legacy_P..._Drawings/Classic_RH_Drivers/SSD3301_data.pdf
seems to just be excursion limits and thermal with a recommended cutoff of ~0.75 crossover frequency.
ftp://ftp.renkus-heinz.com/Legacy_P..._Drawings/Classic_RH_Drivers/SSD3301_data.pdf
seems to just be excursion limits and thermal with a recommended cutoff of ~0.75 crossover frequency.
Imagine you wanted to use a compression driver without any horn, like an ordinary tweeter - that's perfectly possible (although not very useful or effective - that's beside the point). How would you find out what's the lower usable limit in your particular case? No manufacturer's data to help you.
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Besides measuring distortion there isn't a clear cut answer. Faital Pro does give you gap/winding measurements. Most xmax ratings for tweeters/compression drivers I've seen have been based on the most conservative xmax calculations. Anywhere from 0.1-1.5mm for domes and 0.1-1mm for compression drivers.
Edit: JBL seems to use a different calculation or maybe based on distortion. Seems close to the 1/4 or 1/3 of the gap method. (Winding-Gap)/2+1/4gap
476Be
Piston Excursion calculator
Gives a decent idea of what your working with. Add a few decibels for your typical waveguide depending on the coverage angle and size.
Looks like the HF1440 would come in at 0.8mm using the 1/4 calc. Which is what BMS states for their 3.5" rings interestingly enough. Looks like it would produce about 110db on a flat baffle.
Edit: JBL seems to use a different calculation or maybe based on distortion. Seems close to the 1/4 or 1/3 of the gap method. (Winding-Gap)/2+1/4gap
476Be
Piston Excursion calculator
Gives a decent idea of what your working with. Add a few decibels for your typical waveguide depending on the coverage angle and size.
Looks like the HF1440 would come in at 0.8mm using the 1/4 calc. Which is what BMS states for their 3.5" rings interestingly enough. Looks like it would produce about 110db on a flat baffle.
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As a rule of thumb, it's probably safe to say that a horn provides roughly 1 octave extra bandwith towards the low end.
This is the impedance of the HF1440 mounted on FaitalPRO's LTH142 Horn:
Considering the LTH142 is a fairly small Tractrix horn, the naked driver can probably used from around 1000Hz. This is consistent with Legis' findings.
Absolutely!
If you deal with horns and compression drivers and compare the performance to that of an average dome tweeter, then SPL becomes a relatively insignificant factor. At least for hi-fi.
Nevertheless, the operating range of compression drivers isn't infinite and partly depends on the horn used with it.
If you deal with horns and compression drivers and compare the performance to that of an average dome tweeter, then SPL becomes a relatively insignificant factor. At least for hi-fi.
Nevertheless, the operating range of compression drivers isn't infinite and partly depends on the horn used with it.
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FYI, this could be the "throat impedance" in this case. Maybe you would like to adjust your estimate based on that now
I mean, this curve alone is not really telling you much.
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The radiation impedance doesn't matter much in the end.
Look at your typical direct radiating woofer. They're making all their spl through sheer brute force displacement and very low efficiency at the bottom of their range. This is the reality of small radiators vs. relatively large wavelengths.
Wouldn't get hung up on that unless you plan to do the same for the rest of the system. Luckily prosound drivers in home settings can make you deaf without any effort.
Look at your typical direct radiating woofer. They're making all their spl through sheer brute force displacement and very low efficiency at the bottom of their range. This is the reality of small radiators vs. relatively large wavelengths.
Wouldn't get hung up on that unless you plan to do the same for the rest of the system. Luckily prosound drivers in home settings can make you deaf without any effort.
