HOM's or higher order modes refer to non planar waves reflected off the horn walls and coming out after one or more reflections at skewed angles. With a compression driver and suitably designed phase plug - the sound wave emitted from the compression driver aperture is supposed to be as close to the ideal plane wave as possible. Then the job of the smooth waveguide is to take that and expand it as one big wave with no reflections.
That's fine for a compression driver designed to generate planar waves up to their top bandwidth. There is a paradigm shift when using large scale full range cone drivers to excite the horn. Cone full range drivers are known to be non pistonic above a certain frequency and have complex breakup modes. So they inherently will have non planar waves being generated. It is an accepted fact of listening to full range drivers that they have breakup modes. Some more than others. A well damped cone like the ScanSpeak 10F/8424 has well controlled breakup that is not offensive sounding. The FR58EX and SB65WBAC25-4 are both aluminum cone drivers but they have methods used to control those breakup modes. The SB65 uses pentagonal symmetry embossed ridges on the cone coupled with a large polymer dustcap to absorb the breakup resonances. The FR58EX uses a thick rubber surround that extends halfway into the aluminum cone and uses a thick layer of viscous glue to hold the aluminum dustcap to the cone, and together they prevent nasty resonances from breakup.
With that said, I think what I am saying is that I don't care that there are HOM's as I will take the huge reduction in harmonic distortion that the cone driver offers over the higher HD compression driver which may have lower HOM's. The HD reduction is a more important and more audible effect than HOM's to me. But one can always put reticulated foam in the horn cavity to help filter out the so-called HOM's if needed. Nothing precludes the same technique from being used.
That's fine for a compression driver designed to generate planar waves up to their top bandwidth. There is a paradigm shift when using large scale full range cone drivers to excite the horn. Cone full range drivers are known to be non pistonic above a certain frequency and have complex breakup modes. So they inherently will have non planar waves being generated. It is an accepted fact of listening to full range drivers that they have breakup modes. Some more than others. A well damped cone like the ScanSpeak 10F/8424 has well controlled breakup that is not offensive sounding. The FR58EX and SB65WBAC25-4 are both aluminum cone drivers but they have methods used to control those breakup modes. The SB65 uses pentagonal symmetry embossed ridges on the cone coupled with a large polymer dustcap to absorb the breakup resonances. The FR58EX uses a thick rubber surround that extends halfway into the aluminum cone and uses a thick layer of viscous glue to hold the aluminum dustcap to the cone, and together they prevent nasty resonances from breakup.
With that said, I think what I am saying is that I don't care that there are HOM's as I will take the huge reduction in harmonic distortion that the cone driver offers over the higher HD compression driver which may have lower HOM's. The HD reduction is a more important and more audible effect than HOM's to me. But one can always put reticulated foam in the horn cavity to help filter out the so-called HOM's if needed. Nothing precludes the same technique from being used.
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For anybody looking for the SB2.5 in Aus.
SB65WBAC25-4 Sb Acoustics 2 1/2? Wideband Driver - Au | Wagner Online Store
I think this is the right driver.
Wagner seems to have lots of good drivers for competitive prices down here, but there website search fuction is a bit odd.
They also seem to be one of Australians largest wholesalers of many brands related to audio.
Slightly OT but gotta share it when I find down here.
I'll start looking for suitable horns and mids.
Dean
SB65WBAC25-4 Sb Acoustics 2 1/2? Wideband Driver - Au | Wagner Online Store
I think this is the right driver.
Wagner seems to have lots of good drivers for competitive prices down here, but there website search fuction is a bit odd.
They also seem to be one of Australians largest wholesalers of many brands related to audio.
Slightly OT but gotta share it when I find down here.
I'll start looking for suitable horns and mids.
Dean
That's a scary angle, to be able to see right trough the entire horn like that!
I'll definitely keep my fingers crossed, might do em something like this though, some of the time: \,,/
I'll definitely keep my fingers crossed, might do em something like this though, some of the time: \,,/
Once again, great progress. That woofer mount is definitely a happy face. Let's hope it holds up to its visage when the data comes in. You need a rear chamber on it though otherwise there will be cancellation at distance from port to back of cone similar to open baffle cancellation. So if distance is 10cm from port to mouth, total distance is 20cm. You will have bass falloff same as 20cm baffle so bass will fall off at 6dB/oct from 850Hz. 3 octaves to 100Hz so you will be down -18dB at 100Hz.
My Faital Pro LTH142 waveguide and a pair of Dayton DC200-8's are scheduled to arrive tomorrow. I better get crackin' on the design of the smooth throat adaptor.
Bushmeister: how did you drill the 50mm holes in the WG? From the outside or did you make a pilot hole from inside then drill from outside?
Bushmeister: how did you drill the 50mm holes in the WG? From the outside or did you make a pilot hole from inside then drill from outside?
At the moment I haven't chosen a waveguide, but I am reading this thread to glean some knowledge in that area 🙂
-13 dB? Well that may or may not be an issue for me.
The TB W2-800 are somewhat more efficient than the Fountek, guessing as I cant recall (or search well enough while commuting) but its around 3dB maybe more. And as X says the motors are strong (I think the w2-800 is qts of 0.25)
So whilst you are entirely correct, I think (hope) the motor, increased efficiency and my SPL requirements will mitigate those limitations.
They are drilled with a 60mm hole saw outside to in. The horns inner surface was taped to prevent cracking.
One other option is drilling two smaller holes and using a Dremel tool to cut a hotdog shaped slot of equivalent area. I guess that may be more work and your measurements have shown the plain circle works very well from the HF WG dispersion aspects.
Putting a wooden block of approximate conformal shape as the WG on the inside can also be used to prevent splitting when drilling through as well.
Final question - did you holes saw using a hand drill motor or a drill press?
Putting a wooden block of approximate conformal shape as the WG on the inside can also be used to prevent splitting when drilling through as well.
Final question - did you holes saw using a hand drill motor or a drill press?
Yep - that would be a way to cut slots rather than holes, but not with the 3cm of epoxy/horn plastic/MDF the way I did it - I don't think a dremel would do it!
Also - I prefer the idea of tapping the woofers in one spot into the horn - the slot spreads the tap further about the horn profile.
Answer to hole drilling - by hand! 😀
Also - I prefer the idea of tapping the woofers in one spot into the horn - the slot spreads the tap further about the horn profile.
Answer to hole drilling - by hand! 😀
You are a brave man!!!
I forgot about the big lump of epoxy - yes, Dremel tool won't work there. I like round holes too - especially since easy to cut and they work fine on the waveguide.
Sort of an open question for other members as a brainstorn here: are there other ways to interface a flat plywood driver mounting board to a curved plastic waveguide wall securely?
Attach wood panel all the way around horn like a box/dam and fill space with polyester hardening resin? Plaster of Paris? Cement? etc.
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all good questions and more
did you build up the epoxy by layers or all at once?,
did you trowel it on smooth and level to the eye or use forms?
was clamping the MDF in place while glue/epoxy adhered a problem?
....
I guess I'm looking for a blow by blow description of the process before I cut into my expensive waveguides
thanks.
....
did you build up the epoxy by layers or all at once?,
did you trowel it on smooth and level to the eye or use forms?
was clamping the MDF in place while glue/epoxy adhered a problem?
....
I guess I'm looking for a blow by blow description of the process before I cut into my expensive waveguides
thanks.
....
I will give a full account once I know it works!! I have yet to screw the woofer down and try it!
So I don't want to give people bad advice - if it all falls apart 10 mins after cranking the woofer up!
So I don't want to give people bad advice - if it all falls apart 10 mins after cranking the woofer up!
Maybe im a little fool but time ago (for a home plumbing work) i used a type a foam (so strong one but little flexible if compressed) for do a joint in a flat surface with a pipe (both surfaces are PVC plastic). I do that really easy and only had cut the foam shape and the central hole needed with a simple cutter knife (sorry i dont know what is the real english name for that tool).
The foam (if enough strong) can be then compressed with screws (the screws can to do a well sealed joint, and if we need can use some other liquid seleant to make a perfect joint with both surfaces.
Foam was packing a box appliance (think of a refrigerator). It is a very hard foam (reddish).
Similar to this on pic i post:
Pink 1*2M Packing Sponge Foam For Toy / Model 13-50kg / m³ 13-46D
The screws on the part that goes to the tube (in this case the horn) may be coupled to a semi-ring (metal for example) around it.
There are plumbing rings with screws and nuts attached at their ends ready to fix on pipes.
It is much easier to do than to explain here ... at least with my worst level of English.
Im really impresed with all the really good and high level prof of people i find here working on this, and i try do the best (sadly is really poor) to try to help in the littles thinks i can offer.
X asked us for ideas and this is my rain storm ideas ... so sorry about that
Regards to all
The foam (if enough strong) can be then compressed with screws (the screws can to do a well sealed joint, and if we need can use some other liquid seleant to make a perfect joint with both surfaces.
Foam was packing a box appliance (think of a refrigerator). It is a very hard foam (reddish).
Similar to this on pic i post:
Pink 1*2M Packing Sponge Foam For Toy / Model 13-50kg / m³ 13-46D
The screws on the part that goes to the tube (in this case the horn) may be coupled to a semi-ring (metal for example) around it.
There are plumbing rings with screws and nuts attached at their ends ready to fix on pipes.
It is much easier to do than to explain here ... at least with my worst level of English.
Im really impresed with all the really good and high level prof of people i find here working on this, and i try do the best (sadly is really poor) to try to help in the littles thinks i can offer.
X asked us for ideas and this is my rain storm ideas ... so sorry about that
Regards to all
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I continued thinking (apologize for that) a bit more and I think if the two flat superfies for woofers are facing each other (with the horn in the center) just might be screws (or threaded rods) suffciently long to go from a flat surface of a woofer to the other flat surface of woofer and only need tighten the screws on their ends. Foams mentioned earlier would make the joint and would shape adapt to the surface of the horn by just thigthen the screws.
I hope I explained that well enough to understand something ...
Well proably they are useless for the project but will at least some one will make laugh a little ...
I hope I explained that well enough to understand something ...
Well proably they are useless for the project but will at least some one will make laugh a little ...
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Thanks for inputs - exactly the sorts of ideas I was looking for in brainstorming...
I was thinking along similar lines too - a V-clamp basically of two flat boards. One concern is the pressure from the clamp screws may crack the plastic waveguide.
I am thinking maybe build up the epoxy putty on the horn wall until you get a flat surface. Let it harden and then screw the wooden driver board to the formed flat surface rather than relying on the putty to bond the wood to the horn.
Thanks for me explanation was well and understandable, think not method is useless and especially not for a trial setup that sometimes need to be dismantled and adjusted several timed before drivers slope performance are satisfying. So think maybe a good idea for xrk971 that like high speed prototype answers. When leaving prototype grade, feel for a final build that bushmeister's build construction as being stronger and maybe also chance to get more precision into various important distances, but in reality hard to say in that xrk971's various foam core builds looks as good performers.