Hello. This is my first post. I have been perusing the DIY forums for a few years now. A couple years ago I had completed a build of four of Art Welter's Keystone subs and it's been a steep learning curve, but I'm gettin' there.
I'm working my way into building tops now and I've always been fascinated by Multiple Entry Horns (MEH, Unity horns, Synergy horns, etc). I've been considering building a sort of hybrid MEH/Line Source. The concept is four stacked B&C DCX464 mid/high coax drivers with the new 90 degree waveguide extension WG148-90.10 in their Suggested Designs section to cover 500Hz and above, and then 8 10" drivers to cover the lows and low mids. This design would have a 90 degree exponential horn extending beyond the waveguide extension with 1/4 wavelength ports like an MEH design would have. Right now I'm looking at B&C's 10NW76 as a possible 10" driver choice.
The photo's going to immediately look like a Danley J7 but that's not intentional and I've seen the J7's insides and it's not even close to the same. It's just sort of how this turned out. The waveguides end up stacking to around 39 inches top-to-bottom for the center. Adding the 10" drivers in an MEH-style just sort of ended up this way.
From a design standpoint, I'm trying to create a loud and high-fidelity speaker with good pattern control for live sound applications and a simple 2-way low/high design from a powering perspective (since technically the DCX-464 is already a 2-way driver).
Things I don't know:
1) can I stack line array waveguides like this without too much destructive interference? The person 3-D printing them for me will be modifying the WG148-90 to have zero verticality for the center two HF drivers and then a +20 degrees for the top and +20 degrees for the bottom. My thought is that I would like to gain that acoustic summation similar to a line source, but for all I know there's a reason I haven't seen this design on the forums and that's cuz it just doesn't work with physics.
2) would there be any benefit to mounting the 10" drivers to the horn if I expect the DCX to get down to 500Hz? I can always lengthen the horn and I assume that the horn length needs to be 1/4 wavelength long of the lowest frequency that I want directivity for. This is around 1.42 feet for each side of the horizontal horn right now, which should get me down to 198.7Hz if that's how that works. Again - new to this on the math side of things.
3) do the lows need to be in their own chamber to protect the DCX drivers from internal box pressure? My gut says yes and I've seen other designs that do that. I am guessing that I would need an enclosure that meets the driver's Vas ratings plus a little more.
4) I just don't know what I don't know.
Thanks!
Steve
I'm working my way into building tops now and I've always been fascinated by Multiple Entry Horns (MEH, Unity horns, Synergy horns, etc). I've been considering building a sort of hybrid MEH/Line Source. The concept is four stacked B&C DCX464 mid/high coax drivers with the new 90 degree waveguide extension WG148-90.10 in their Suggested Designs section to cover 500Hz and above, and then 8 10" drivers to cover the lows and low mids. This design would have a 90 degree exponential horn extending beyond the waveguide extension with 1/4 wavelength ports like an MEH design would have. Right now I'm looking at B&C's 10NW76 as a possible 10" driver choice.
The photo's going to immediately look like a Danley J7 but that's not intentional and I've seen the J7's insides and it's not even close to the same. It's just sort of how this turned out. The waveguides end up stacking to around 39 inches top-to-bottom for the center. Adding the 10" drivers in an MEH-style just sort of ended up this way.
From a design standpoint, I'm trying to create a loud and high-fidelity speaker with good pattern control for live sound applications and a simple 2-way low/high design from a powering perspective (since technically the DCX-464 is already a 2-way driver).
Things I don't know:
1) can I stack line array waveguides like this without too much destructive interference? The person 3-D printing them for me will be modifying the WG148-90 to have zero verticality for the center two HF drivers and then a +20 degrees for the top and +20 degrees for the bottom. My thought is that I would like to gain that acoustic summation similar to a line source, but for all I know there's a reason I haven't seen this design on the forums and that's cuz it just doesn't work with physics.
2) would there be any benefit to mounting the 10" drivers to the horn if I expect the DCX to get down to 500Hz? I can always lengthen the horn and I assume that the horn length needs to be 1/4 wavelength long of the lowest frequency that I want directivity for. This is around 1.42 feet for each side of the horizontal horn right now, which should get me down to 198.7Hz if that's how that works. Again - new to this on the math side of things.
3) do the lows need to be in their own chamber to protect the DCX drivers from internal box pressure? My gut says yes and I've seen other designs that do that. I am guessing that I would need an enclosure that meets the driver's Vas ratings plus a little more.
4) I just don't know what I don't know.
Thanks!
Steve
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so the big issue with this is that the vertical conical horn expects a curved wavefront and your supplying it with a plane wave so the directivity in the vertical plane is going to be that of a truncated line source controled by your waveguides and not of your desired conical horn. ASFIK the waveguides in the J7 are supplying the correct curvature for their position in the (truncated) vertical plane conical horn, this is making the speaker behave as if its a massive deep conical horn. If we look at the vertical dispersion of a Danley J series horn we can see its not narrowing like a line source would be instead displays constant directivity behaviour:
https://pierreaubert.github.io/spin... J3-64/Danley/index_vendor-pattern-60x40.html
B&C's 10NW76 is a monster ASFIK and a good choice
Danleys inovation with the conical horn was to notice that the flare rate decreases as you approach the mouth of the horn, the flare rate is setting the low frequency cut off so by correct placement of the 10" drivers on the horn you can get some increase in efficiency. Also if you position your 10" sources within 1/3 wavelength at the crossover you can have full range point source behaviour.
the lows don't need to be in their own chamber.
https://pierreaubert.github.io/spin... J3-64/Danley/index_vendor-pattern-60x40.html
B&C's 10NW76 is a monster ASFIK and a good choice
Danleys inovation with the conical horn was to notice that the flare rate decreases as you approach the mouth of the horn, the flare rate is setting the low frequency cut off so by correct placement of the 10" drivers on the horn you can get some increase in efficiency. Also if you position your 10" sources within 1/3 wavelength at the crossover you can have full range point source behaviour.
don't rearly get this they won't work like a point source cluster when arrayed as a line if thats your aim, as you would have to have an apparent common origin for this to work.
the lows don't need to be in their own chamber.
There are much more knowledgeable people here to answer your queries so I'm not going to, but I can tell you Scott Hinson posted a multiple entry horn design using the dcx464 and 10nw76 3 days ago..
It's on his Facebook which is called 'diyrm'.
His design uses 1 dcx and 2 woofers per channel so may not be exactly what you are looking for but I'm sure you'll find his document interesting and he might be able to enlighten you further.
Please do update your thread with any insights you gain there.
It's on his Facebook which is called 'diyrm'.
His design uses 1 dcx and 2 woofers per channel so may not be exactly what you are looking for but I'm sure you'll find his document interesting and he might be able to enlighten you further.
Please do update your thread with any insights you gain there.
I have been thinking about a simlar design recently. Kind of a cross between this and an EAW ANYA. A very large number of compression drivers is used each driving a bent horn 1" high (or less) with the horns having only horizontal expansion, vertically arrayed into a larger conical horn. The large conical horn is open at the top and bottom. Each tweeter has its own amp channel and DSP thus the directivity can be adjusted. Quite a tricky project though due to the need for custom electronics to have all the amp and dsp channels in the box.
forgot this post has details on the J7 tweeter array its not super complicated to fabricate just conical horns alternating left and right and arranged with the curvature expected of a conical horn at that depth in the larger horn: https://www.diyaudio.com/community/threads/constant-curvature-tweeter-array.388439/#post-7149222
you can see the directions the conical horns are facing well in this picture.
you can see the directions the conical horns are facing well in this picture.
Really should sticky this pdf. One of the most, if not the most, informative paper on MEH. Even has a STL file for throat adapter.
Steve,
Going four way (Keystone subs, 10" low mids, 4" high-mid cones, HF compression drivers) would be a better choice for the goal of a loud and high-fidelity speaker. You would save expense, gain in fidelity and output.
You could still go three way using a passive crossover between the high-mid cones and HF compression drivers, though with the price of DSP/amplification compared to crossover components, not much savings, and lots of drawbacks.
That's what they are designed for, though normally they are arrayed in a vertical arc.
The benefit of a multiple entry horn with entries within 1/4 wavelength of each other is they can behave as a virtual point source over a wide bandwidth.
The horn length does not determine directivity.
The directivity of the horn can be approximated with Bill Waslo's Synergy Calculator:
http://www.libinst.com/SynergyCalc/Synergy Calc V5.pdf
No, sealed HF drivers can share the chamber with LF drivers. If you were to use mid cones on the MEH, they would need to be in their own enclosures if they were not a sealed design.
Vas is only one of the TS parameters to be considered..
Me neither
Art
While it's good to see enthusiasm on the subject of MEH design, I do see some significant phase and group delay issues in that design, a subject that Danley himself makes a big deal of--and for good reason.
I also think it's better to put the off-axis woofer ports on top and bottom so that the effects of such large and long woofer ports (as shown) will not end up significantly affecting the horizontal polars by nearly as much.
Which brings up a point: I don't see a polar sonogram--which is a big omission.
There are other issues (including the use of Hypex Fusion). I think a closer reading of Danley's US8284976 patent (Synergy) is wise with respect to its differences with US6411718 (Unity--the patent which actually expired in 2014 due to fee payment issues, not 2019 as the author stated).
A lot of performance is being left on the table.
Chris
I also think it's better to put the off-axis woofer ports on top and bottom so that the effects of such large and long woofer ports (as shown) will not end up significantly affecting the horizontal polars by nearly as much.
Which brings up a point: I don't see a polar sonogram--which is a big omission.
There are other issues (including the use of Hypex Fusion). I think a closer reading of Danley's US8284976 patent (Synergy) is wise with respect to its differences with US6411718 (Unity--the patent which actually expired in 2014 due to fee payment issues, not 2019 as the author stated).
A lot of performance is being left on the table.
Chris
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1) "can I stack line array waveguides like this without too much destructive interference?"
The question is better put, "at what frequency will destructive interference become an issue?". At the point where the centerline of the compression driver ports are 1/4 to 1/2 wavelength apart, you will start to see destructive interference, especially off-axis
2) "would there be any benefit to mounting the 10" drivers to the horn if I expect the DCX to get down to 500Hz?"
Yes. It's the difference between an MEH and a multiple aperture multiway loudspeaker.
3) "do the lows need to be in their own chamber to protect the DCX drivers from internal box pressure?"
No. The compression drivers are effectively sealed.
4) "I just don't know what I don't know."
Your hybrid line array design isn't the best of both worlds (multi-aperture multiway vs. MEH), but it will be much less expensive than buying a J7... Your choice.
Chris
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Thanks for reminding the patents. I tried to read them some time ago, but when I read through them again today, it all clicked together. And they also explained some weird things I measured some time ago with one of my builds (reverse phase null). So the next build will be the ultimate one following the rules laid out in the patents.
"that design" = a specific design in this thread or MEH in general? And can it be solved it if it a general problem or do you just live with it?
The design that I was referring to is the one in the PDF file posted above, reportedly from the Facebook source, not the OP's design.
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There seems to be a commonly encountered response to the design of multiway loudspeaker crossover filter networks that always have to use higher order networks. This is the source of the problem: induced phase lag of the lower-frequency drivers due to these "named" crossover filters (e.g., Butterworth, L-R, Bessel, etc.).
The design of an MEH of the "Synergy Horn" class (a trademark that really shouldn't be used by DIYers) calls into question the use of crossover filters of the type that most everyone is familiar with. With these higher performance MEHs, the goal of the design is point source performance (i.e., flat phase response and group delay response).
Can you do something about the problem of phase growth in MEHs? Easily. But you have to know a bit about what you're doing, rather than saying, "well, this MEH design can't easily be made into a point source..."--which is something that I read in the PDF file that I referenced above (that's wrong, of course). It can, very easily, but thinking about what you're doing and what you actually need out of the crossover filters seems to be the problem: not many people are actually thinking about the crossover filter trade-offs when employing MEHs.
When you use multiway loudspeaker components on a flat baffle or on a multiple aperture horn-loaded loudspeaker design, there are simultaneously competing tradeoffs with respect to flat SPL response, polar lobing and phase/group delay growth (all of which are extremely audible).
There effectively isn't any polar lobing in a properly designed MEH. Most people are not thinking about this fact, and what it means to crossover design. Acoustic summation is occurring inside the horn aperture. Think what that means in relation to a multi-way flat-baffle loudspeaker. The MEH represents a huge advantage, acoustically. The effect of having a flat phase/group delay loudspeaker that has virtually unlimited dynamic range (unlike full range drivers), is something that most people haven't even heard. You should hear it. You'll never go back to "conventional" multiway loudspeakers/full-rangers.
I find that most people are not thinking about the huge advantage of acoustic summation of multiple drivers inside the single horn aperture. It doesn't matter that there is increased overlap of drivers' pass bands inside an MEH (and Danley Synergy SH-50 loudspeakers prove this point in spades).
How do you solve the phase growth problem in an MEH design? Don't use higher order crossover filters.
What do you use instead? A crossover filter that provides 90 degrees or less of phase growth from high frequency to lower frequency.
That's pretty easy to conceive and implement. An MEH will actually work with no crossover filters at all in terms of its phase response (each lower frequency driver way leads the higher frequency driver by 90 degrees--which is acceptable).
When using a DSP crossover to implement the MEH balancing (which I recommend with controlled coverage horns and MEHs in general), you don't even have to use a typical crossover filter set. Instead, try using filters that are typically used for EQing only. That way, you can dial in the requisite channel delay needed, which is less than the equivalent of 90 degrees of phase shift. [Note: the US8284976 patent is still in effect, so crossing the lower frequency drivers below their notch frequency is technically a patent violation--even for DIYers.] My MEH designs use the woofers' first notch frequency as part of its crossover structure to achieve ~10 dB/octave slopes (i.e., a non-integer order acoustic crossover).
Chris