Half-size Orelo VS traditional midbass horn (Orelo/Orelino)
Hello, I'm a new user on this excellent forum
I have been planning a midbass horn build for a while, and then I came across the Orelo on this forum. Very late to the party, I know.
The Orelo looks very elegant and easier to build than an exponential flare midbass horn, and if I understand correctly, can be used lower in frequency with some EQ applied.
And I understand the Orelo is a waveguide, so will not have the loading characteristics and efficiency of a horn.
My question is, what is the difference in sound between these two designs? Will the Orelo provide the 'snap' and dynamics of a horn?
For the midbass horn, I was planning on using two Precision Devices PD153ER per side. I guess this may not be an optimal driver for OB application, as it has a very strong motor?
Stronger than the BD15. While horn drivers should have very specific properties, are there any such properties that makes a driver suitable for this application?
Half-size Orelo VS traditional midbass horn
by Bert 
, Saturday, March 02, 2019, 19:48 (1874 days ago) @ RB
Hello RB,
My question is, what is the difference in sound between these two designs? Will the Orelo provide the 'snap' and dynamics of a horn?
Basically yes, perhaps a little less for not being as effecient as a well designed horn can be but with bonus having a bass without colouration and more friendly for bass difficult rooms. Also more efficient in the deepest frequencies... no subwoofer will be needed.
For the midbass horn, I was planning on using two Precision Devices PD153ER per side. I guess this may not be an optimal driver for OB application, as it has a very strong motor?
It depends how low you're going to EQ the bass (think excursion limits) and how loud you're going to play. With two 15" drivers in an Orelo you'll have plenty of headroom for normal domestic use...
Think that the range above 80Hz is very efficient already and at 100Hz just as efficient as a real horn unless it is designed for maximum efficiency at 100Hz of course...
Stronger than the BD15. While horn drivers should have very specific properties, are there any such properties that makes a driver suitable for this application?
The EBP is more important than a stronger magnet although related, the higher the EBP the higher frequency the driver can load a horn without loss ...
... for the rest is does not say much. A very strong magnet driving a relative heavy moving diaphragm will be less dynamic but more efficient in the deeper bass.
The spec's of the driver looks okay for use in the Orelo.
I would not EQ too low but flat down to 30 -35Hz will work out more than OK for most "work".
Bert
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BD-Design - Only the Best!
Half-size Orelo VS traditional midbass horn
Hi Bert, thank you very much for answering my questions! Here are some more when you have the time
The EBP is more important than a stronger magnet although related, the higher the EBP the higher frequency the driver can load a horn without loss ...
EBP=Fs/Qes
As far as I know there are three factors that limit the high frequency of a cone driver in a horn; VC inductance, airchamber in front of driver acting as LP filter and the so called fHM or mass-corner. fHM is defined as 2*Fs/Qts, while EBP is defined as Fs/Qes. So fHM is about twice the value of EBP, I don't understand this relation? Why is the value not the same?
According to this formula for fHM, the BD15 driver only has an upper frequency limit of 300Hz.
What does this really mean? The on-axis respons of the BD15 surely reaches much higher than this..
When I model a driver in Hornresp, the power response shows the effect of fHM as a quickly dropping HF response, but if I model the on axis response the HF of course much higher.
But isn't the on axis response what we are interested in?
Your BD15 driver can reach very high on-axis, so what is it about the fHM that limits it to 300hz in a horn? I guess it has to do with dispersion, but I thought the driver cone diameter was the limiting factor here..
So many questions
Half-size Orelo VS traditional midbass horn
by Bert , Sunday, March 03, 2019, 20:09 (1873 days ago) @ RB
Hi RB,
Your BD15 driver can reach very high on-axis, so what is it about the fHM that limits it to 300hz in a horn? I guess it has to do with dispersion, but I thought the driver cone diameter was the limiting factor here..
On a free radiating panel the driver has a relative flat frequency curve where only the highest frequencies radiate on axis, off axis the diameter of the diaphragm comes in play where the highest frequencies are only present on axis, the lower frequencies spread wider and will still play all as loud.
So there is much more total lower frequency energy radiating when you would avarage everything instead of measuring only on axis.
In a horn there is besides added reflections (pushing the frequencies radiating off-axis forward) also an increase in efficiency (some sort of "amplification depending on the type of horn (Hyperbolic, Exponetial, Tractrix...), mouth size, throat size, rear chamber volume and front chamber volume).
Think it as a "boost" in a limited frequency range...
Cheers,
Bert
--
BD-Design - Only the Best!
Half-size Orelo VS traditional midbass horn
Thanks for the explanation Bert, I appreciate it
Still wondering about the driver specifications needed for this "hybrid" application.
The front would require a typical horn driver with low qts, while the OB back would require a very high qts above 0.5 to work efficiently..
BUT I guess the waveguide nature of this design doesn't actually work as an impedance transformer with a fixed air volume in front of the driver cone, thus no requirement for a very strong motor.
How would this construction behave if using an exponential curve (T=1 for instance)? A more slowly opening flare may provide more loading below 150-200hz?
If we then proceed with putting a top on it, we have a horn
It would be an interesting process to build something like this in iterations, first test it as a waveguide and then see what happens when it turns into a horn!
Half-size Orelo VS traditional midbass horn
by Bert , Monday, March 04, 2019, 21:28 (1872 days ago) @ RB
The front would require a typical horn driver with low qts, while the OB back would require a very high qts above 0.5 to work efficiently...
If you're thinking passive then yes... with an active system it does not matter much, just give the lower frequencies more gain.
With that in mind it will be better to have the strong motor again with the low Mms for a bass with more "punch" and own control instead of flapping wooferen without any control due to their releative weak magnet.
BUT I guess the waveguide nature of this design doesn't actually work as an impedance transformer with a fixed air volume in front of the driver cone, thus no requirement for a very strong motor.
It still does but the "boost" will be in a narrow range which is still good because that boost will be in the crossover range to meet up with the horn on top.
It would be an interesting process to build something like this in iterations, first test it as a waveguide and then see what happens when it turns into a horn!
Sure! 
but closing-in things more makes things resonate more and will add more colouration to the sound.
For real deep bass you'll need a real horn (length, size and surface!).
Bert
--
BD-Design - Only the Best!