Planning a giant MEH and there is ribbon tweeter from another project that i absolutely love. So i am figuring it out whether i can use the ribbon in this project.
So the question is how much horn dimensions affect how low ribbon tweeter + horn combo goes and can be crossed over?
Situation:
New dimensions for the horn 120cm wide x 80cm height x 50cm deep ( Yes, giant)
So how much lower the ribbon goes on these new dimensions?
The problem is that in these MEH designes midrange reaches to 1khz, 1,5khz absolutely max.
I can use 48db/oct, 96db/oct or even brickwall crossover if needed
Efficiency is given 99db with the original horn, i dont play loud at all, what i mean is that i can plant the extremely steep crossover at the area when the ribbon frequency response is already dropping and then eq the rest all the way down. I use rephase linear phase filters for crossover
I truly want this ribbon in this MEH
And i dont mind the distortion rising, i dont believe that it is audible in these modern levels of distortion
So the question is how much horn dimensions affect how low ribbon tweeter + horn combo goes and can be crossed over?
Situation:
- original ribbon horn is 25cm tall x10cm wide x 10cm deep
- crossover frequency is given originally at 2400hz
- suspect that 2400hz is given for 12db/oct crossover, old school ribbon, no mention of db/oct at 2400hz
New dimensions for the horn 120cm wide x 80cm height x 50cm deep ( Yes, giant)
So how much lower the ribbon goes on these new dimensions?
The problem is that in these MEH designes midrange reaches to 1khz, 1,5khz absolutely max.
I can use 48db/oct, 96db/oct or even brickwall crossover if needed
Efficiency is given 99db with the original horn, i dont play loud at all, what i mean is that i can plant the extremely steep crossover at the area when the ribbon frequency response is already dropping and then eq the rest all the way down. I use rephase linear phase filters for crossover
I truly want this ribbon in this MEH
And i dont mind the distortion rising, i dont believe that it is audible in these modern levels of distortion
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Consider that you get 6dB for each halving of the radiation space, and run that against the directivity of the waveguide. It won't be exact but it will give you a clue what to expect.
Most MEH horns are conical, the length makes little difference in "how low" the horn goes, but the mouth area determines how low the pattern control extends. If the new horn dispersion angles are less than the old horn, sensitivity will increase, and the horn will also go lower.
That said, it sounds like you are planning a wider dispersion horn than the original, so it's low frequency on axis sensitivity may drop.
If you were happy with the SPL you could achieve with the sensitivity of the original horn, the ribbon should be OK, as long as you don't exceed it's excursion capability.
Four times the displacement (excursion) is required for each halving of frequency to maintain the same level.
A six dB drop cuts excursion in half, a 12dB per octave crossover basically maintains the same excursion below the crossover point, while a 24dB reduces excursion at double that rate.
Using a 24dB or greater slope at 1500Hz may reduce excursion compared to the original specifications.
Art
Here’s my take…..as ribbons excel at detail due to the delicate nature of the element, I would not ‘horn load’ a ribbon under any circumstance. Wanna shape the radiation a bit with a shallow waveguide?….fine….but don’t horn load em….use an AMT instead.
mayhem13, most of your concern there is normally a matter of the compression ratio typically used with horn loading. On the other hand, a ribbon probably should (and is more likely to be) put on to a waveguide where the throat equals the diaphragm area, so 1:1 compression.