Hi there,
I’d be grateful for any theories here.
I’ve made the above Horn which is an offset entry design/ synergy Horn.
I’ve checked the dimensions carefully and the Horn resp model matches it.
However, the response I’m getting (treated with a sine wave) is this:
I tested this with a sine wave and listened. It might not be as exaggerated as the blue line suggests, but it definitely deviates from the computer model by at least 3-4dB.
I can partially solve the problem by using a 1.2khz crossover with the tweeter (the test was with 2k).
But it would be nice to know why this is occurring.
I would say incorrect chamber volume in front of the mid driver and/or the coupling holes not correctly defined.
Just tried moving the entry hole closer to the start of the Horn and that seems to be pushing the predicted response in the right direction.
Nonetheless, the Horn I have built is definitely the right shape for the model.
Although, I’m reminded now, that I didn’t find a way of changing the entry hole size in Horn resp, so built it to the size indicated to the schematic.
Is there any way of finding the correct area for the entry hole?
Nonetheless, the Horn I have built is definitely the right shape for the model.
Although, I’m reminded now, that I didn’t find a way of changing the entry hole size in Horn resp, so built it to the size indicated to the schematic.
Is there any way of finding the correct area for the entry hole?
Ah, by chamber volume you mean the amount of space directly in front of the cone (behind the hole)?
How do I find out this value?
I made the piece of ply I attached the driver to with plenty of room to rout out some volume in case that was a problem.
How do I find out this value?
I made the piece of ply I attached the driver to with plenty of room to rout out some volume in case that was a problem.
My limited experience with MEH sims and how they align with reality is described here: https://www.diyaudio.com/community/threads/2-way-synergy-inspired-by-spl-runt.378456/
Once properly adjusted, the responses are pretty similar.
My advice would be to change the parameters of the model until they match the measurements of the built thing and then try to draw conclusions.
The top end is the bandpass part, so I would focus on the chamber volume (yes, below cone) and the hole size (diameter, length, profile). My guess would be too much volume and too small hole (but that is just a guess, others may know better). Sharing the Hornresp records would help people to help as well.
Once properly adjusted, the responses are pretty similar.
My advice would be to change the parameters of the model until they match the measurements of the built thing and then try to draw conclusions.
The top end is the bandpass part, so I would focus on the chamber volume (yes, below cone) and the hole size (diameter, length, profile). My guess would be too much volume and too small hole (but that is just a guess, others may know better). Sharing the Hornresp records would help people to help as well.
I have adjusted the model to exactly what I have in front of me.
Is it possible to change the hole size in the Hornresp model I have? This is an offset entry model- I did this because I am only using the one mid driver and one entry point.
Ah - I see I have VTC and ATC set to zero. I think in the computer model stage I tried to increase only VTC, thinking that HR would react to that.
I was thinking the parameters would be visible in the photos I posted, may be wrong.
Thanks for the input, this is definitely helping.
Is it possible to change the hole size in the Hornresp model I have? This is an offset entry model- I did this because I am only using the one mid driver and one entry point.
Ah - I see I have VTC and ATC set to zero. I think in the computer model stage I tried to increase only VTC, thinking that HR would react to that.
I was thinking the parameters would be visible in the photos I posted, may be wrong.
Thanks for the input, this is definitely helping.
Also I think I assumed that HR would take into account the volume of air occupied by the cone shape of the driver when the driver is simply butted against a panel? Guessing this was a wrong assumption.
Edit- indeed increasing VTC along with ATC produces the sort of thing I’m hearing. And it corresponds to my estimate of the volume occupied by the cone shape. Promising!
I think I’ll be able to reduce the volume without the driver touching the enclosure, so I’ll try that.
Thanks!
Edit- indeed increasing VTC along with ATC produces the sort of thing I’m hearing. And it corresponds to my estimate of the volume occupied by the cone shape. Promising!
I think I’ll be able to reduce the volume without the driver touching the enclosure, so I’ll try that.
Thanks!
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Just a note - posting the hornresp records would allow anyone to play around with parameter values and see potentially problematic areas. Hornresp is great, but it does not do anything automatically, all needs to be considered by the user.
Thanks, I will post the exact parameters soon.
I’ve made the following throat adaptor to reduce the air in front of the cone.
The only thing is, although I have reduced the VTC, I have also extended the hole.
In order to remove a little more volume out, would it work to vary the cross-sectional area of the hole?
IE, maybe insert a ring such that the middle cross-section is reduced. Or will this just effectively narrow the hole and mess up the relationship between the throat size and throat chamber volumes?
I’ve made the following throat adaptor to reduce the air in front of the cone.
The only thing is, although I have reduced the VTC, I have also extended the hole.
In order to remove a little more volume out, would it work to vary the cross-sectional area of the hole?
IE, maybe insert a ring such that the middle cross-section is reduced. Or will this just effectively narrow the hole and mess up the relationship between the throat size and throat chamber volumes?
So, my question was answered by Pelanj. Thanks so much for the input.
Adding the throat adaptor has greatly reduced the peak around 600hz- the cause of my mistake was not defining VTC and ATC values in Horn Resp, resulting in a large throat chamber created by the cavity in front of the cone, which was unaccounted for in my Horn Resp simulation.
Adding the throat adaptor has greatly reduced the peak around 600hz- the cause of my mistake was not defining VTC and ATC values in Horn Resp, resulting in a large throat chamber created by the cavity in front of the cone, which was unaccounted for in my Horn Resp simulation.
PS- does anyone know what sort of particle velocity I should be getting with the right sized entry hole?
Feeling around the hole whilst the speaker is working, I can feel a lot of air movement.
Feeling around the hole whilst the speaker is working, I can feel a lot of air movement.