except its not so much the distance from the throat as it is the distance from the CD's diaphragm or perhaps its phase plug which are often a significant distance further back than the throat.
For a straight (constant cross sectional WG) the notch shoud be 1/4, Right?!
Could be that this 1/5 wave length before first cancelation is a result of that the physical distance differs from the acoustic distance. For example: An exponential horn will have a higher cut of frequency than a transmission line for a given length.
Could be that this 1/5 wave length before first cancelation is a result of that the physical distance differs from the acoustic distance. For example: An exponential horn will have a higher cut of frequency than a transmission line for a given length.
The notch is at ~1/4 but I said it's "usable up to 1/5" - there's a margin. Just have a look at the sims.
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How many times we've been through this? It represents the impulse response of the system, which is the response of the system to a pulse, all the time it takes. If there's e.g. a reflection at 1.2 ms, you'll see it, the same way as 10 ms later.
- I think you still confuse e.g. a spectrogram of a song (which changes continuously with time) with a frequency response of a system (such as a loudspeaker).
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Yes I was surprised - last time we discuss it it seems that you thought that a WF was usable and gave som more info.
- Nope, I'm not.
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- Nope, I'm not.
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You have this understanding wrong. Flat FR simply means perfect pulse in, perfect pulse out. Time is out of the picture (or more precisely, all the time is there). I don't know what a WF is.
That's still the same impulse response, but yeah, it can show things that the magnitude response alone (as often shown) won't, that's true.
I don't know, one would expect it to be the other way around. I only hope I got the coordinates right.
I think you got it right. I've noticed the same appear in Hornresp. It also seems like a smaller throat increases the frequency of the first notch.
Maybe the sound travels along the waveguide wall, bounce, and travel fourth. This would explain why the closest of your simulation fits the lambda/4 criteria best and the last, 57 mm simulation, fits the least.
But then we should expect a lower notch frequency, than what is calculated for the axial distance, because the propagation path would be longer. But the simulations show that the notch appears higher than that. Someting else must be at play here. Anyway, is it important to know?
Ha ha, thats right. My bad. Time to go to bed...
It must be the expansion rate then, compared to a constant-crossectional 'tube'. Why? Still don't know...
For me, it is important since the mids may be placed further down the waveguide. It eases the early work of designing.
It must be the expansion rate then, compared to a constant-crossectional 'tube'. Why? Still don't know...
For me, it is important since the mids may be placed further down the waveguide. It eases the early work of designing.
Yep, the most amount of flexibility is the ideal, so that the HF either doesn't have to run as low, or that the entry ports can be further away.
I had the chance to ask Tom what distance from ports determines the notch, the throat or the CD diaphragm. He said the throat, and i asked why not the actual distance to the diaphragm. He said "think about it, all the pressure is going out". I've also seen a comment or two online about the reflection point often being a little out from the throat. I've kinda come to think that just as regular cone drivers have apparent acoustic centers that aren't at the voice coil or dust cap, a synergy has an apparent acoustic throat (with regards to rearward reflections) that is not right at the CD, but a little bit out towards the mouth.
If you created a simulation with only a throat and one that included the conical portion of a compression driver would the 1/4 notch look the same? Or does the simulation separate from reality at that point?
Fulcrum acoustics also go for a coaxial horn aproach: https://www.fulcrum-acoustic.com/au...esources/compression-head-oculus-phase-plugs/
Turbosound have also used coaxial horns but with a complex arrangment of the mid behind the tweeters then directed around the tweeters in a MTM arrangment at the throat of a common horn: https://www.turbosound.com/product.html?modelCode=P0B8K
you can use the notch as part of the mid/high crossover in a synergy horn allowing the mid to go bit higher than expected. You are also not restricted to standard slopes you have quite a large overlap region so you can actualy have the mids and the compresion driver play the same range you just need good summation and for the compresion driver to have sufficent high pass for protection.
Turbosound have also used coaxial horns but with a complex arrangment of the mid behind the tweeters then directed around the tweeters in a MTM arrangment at the throat of a common horn: https://www.turbosound.com/product.html?modelCode=P0B8K
you can use the notch as part of the mid/high crossover in a synergy horn allowing the mid to go bit higher than expected. You are also not restricted to standard slopes you have quite a large overlap region so you can actualy have the mids and the compresion driver play the same range you just need good summation and for the compresion driver to have sufficent high pass for protection.