Hello,
I got my hands on a line array waveguide with faital compression: the Wg141 and the Hf146R.
I measured the frequency response, and I had a question about it:
You can see a cancellation at 700 and 1400Hz.
What is it due to, a reflection at the mouth and therefore an internal resonance? ( if we consider c/2L it could match )
Faital lists this waveguide as being usable from 800Hz upwards, so does that mean they don't consider this problem to be a problem for use where it's in the frequency band?
Thanks
I got my hands on a line array waveguide with faital compression: the Wg141 and the Hf146R.
I measured the frequency response, and I had a question about it:
You can see a cancellation at 700 and 1400Hz.
What is it due to, a reflection at the mouth and therefore an internal resonance? ( if we consider c/2L it could match )
Faital lists this waveguide as being usable from 800Hz upwards, so does that mean they don't consider this problem to be a problem for use where it's in the frequency band?
Thanks
The waveguide depth, considering the angle along the expansion, and accounting for the depth of the throat section of the driver might account for a dip at 1400Hz.
Were they intended to be used that way without termination or extension?
Were they intended to be used that way without termination or extension?
That was I thought, depth of WG + compensation ( for compression depth and axial deviated path ). Wasn't sure if the open-open case was the right assumption.
Yes, I enteded to use it with a small flare on the exit, and I need to make the crossover as low as I can :/
Yes, I enteded to use it with a small flare on the exit, and I need to make the crossover as low as I can :/
I can't be sure the dip at 700Hz is not connected to your gating.. but assuming it's due to the waveguide you'll want a radius of maybe 12 centimetres.. unless you can use the dip in your cross..?
I'm not sure to understand properly what u are saying. For the radius, u are talking about the flare ? And for the gate u are talking about windowing the measurement ( if yes, it's not connected ). For the dip, I can handle the 700Hz one and work my crossover around, but the 1400Hz sill bother me ^^
Okay ty for your time 🙂 ! So having a 1/4 radius of the wavelenght of the concerned frequency can solve the problem ? Because it allows a sufficient impedance transition to avoid disctinuity?
You could verify the dips are due to a 245mm air column resonance by increasing the horn length and measure if the dips drop in frequency accordingly.
For low level testing, you could cut the four horn extensions pieces from cardboard and tape in place.
A "plane wave guide" such as the WG141 would normally be used with a secondary flare with the desired horizontal coverage angle (it has only ~60 degree coverage above 10k due to the 36.5mm/1.4" exit width), the additional length may put the second dip below 800Hz.
That said, it is assumed line arrays require DSP to correct their on axis response, so a correctable dip at 1451Hz wouldn't be considered much of a problem.
Art