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Multi-Way Conventional loudspeakers with crossovers

Suitable midrange cone, for bandpass mid in Unity horn.
Suitable midrange cone, for bandpass mid in Unity horn.
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Old 30th April 2013, 06:35 PM   #841
nc535 is offline nc535
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Sorry for speaking loosely. The 256 hz pattern loss was horizontal. vertical pattern would be 50% higher. Not quite so big at 3' across the mouth and not overbearing when tucked tightly into a corner.
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Old 30th April 2013, 08:11 PM   #842
JLH is offline JLH  United States
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Originally Posted by nc535 View Post
I ran the 5 to 10 sq. cm. flare rate numbers for a range of horn angles, getting roughly 4 Khz for a 90 degree horn and 2 khz for a 60 degree horn.
I think you might have some miscalculations. When determining the flare rate in the throat of these conical horns, you have to start with a 0.7071" by 0.7071" throat because from corner to corner it is 1". You then sand out the throat to make it 1" in daimeter. The actual starting area for your calculation would be 3.226cm^2 and not 5.067cm^2. Try re-running your numbers with this in mind. You should see those flare rates drop to much lower numbers. I know on a 60 X 40 horn the flare rate the compression driver sees is around 1300Hz.
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Old 30th April 2013, 08:41 PM   #843
nc535 is offline nc535
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Thanks for pitching in, JLH.

that is where I get lost - those little details - because I haven't seen and worked through all the math that they are based on. I understand that construction detail but I'm having trouble relating it to the flare rate calculation. I'm embarrassed to admit that I keep getting this calcuation wrong because you didn't give me explicit directions as to precisely where to click like you did for the mid calcuation.

In hornresp, I just set S1 to 5, S2 to 10, set the FTA to the desired angle, then calcuated the length. Then changed S1 - S2 to Exp and read off the F12. I'm not surprised that is wrong given I was guessing as to the method. But if they are wrong, why do they seem to agree with the hornresp sims I did using YOUR driver model? I know I seem to be a poor student but give me credit at least for trying to validate those results
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Old 1st May 2013, 11:23 AM   #844
JLH is offline JLH  United States
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Originally Posted by nc535 View Post
that is where I get lost - those little details - because I haven't seen and worked through all the math that they are based on.

Itís best to draw out your horn throat and take a ruler to measure it. This way you can be sure what the actual flare rate will be. When you machine out the throat to 1" in diameter, you in effect decrease the flare rate. The throat becomes more like an exponential contour. See attached diagram. Measure the length it takes to go from 5.07cm^2 to 10.14cm^2. For a 60 X 40 horn this should be on the order of about 1300Hz.
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File Type: jpg horn throat.JPG (27.7 KB, 466 views)
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Old 1st May 2013, 02:12 PM   #845
nc535 is offline nc535
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AHA!
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Old 2nd May 2013, 02:11 AM   #846
Patrick Bateman is offline Patrick Bateman  United States
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Originally Posted by natehansen66 View Post
I'll try to explain what I was getting at with the Summa reference. I understand the reasoning that the comp driver won't exert any pressure on the horn walls once its output is past the point in the horn where the circumference is greater than the wavelength of the lowest freq we want to achieve (1200hz in your example). This makes sense since as you've been hammering home the conical horn has a variable flare rate.

Where my confusion lies is with e.g. the Summa's 15" waveguide. From pictures I'd say that 15" includes the radius transition to the baffle. Taking a guess, the radius begins where the waveguide is about 10-12" in diameter. For the Summa to hit 900hz, we're looking at a circumference of about 15", which is a diameter of 4.8". Obviously Earl's waveguides are much bigger than this (4.8" dia), to control the directivity to match a woofer at the xo. It stands to reason in my mind then that the compression driver in the Summa is exerting some pressure on the waveguide walls past the 15" circumference, otherwise it wouldn't need to be as large as it is. I also understand that the radius to the baffle helps control directivity at the low end to prevent waist-banding the polar pattern there, contributing to the larger size.

Drawing that line of reasoning to the Synergy horn, it seems to me that the horn will be constraining the comp driver's directivity past the area where the flare rate no longer loads the device (a catch-22 to your line of reasoning, I know). This would be the region where we are tapping the mids in, and I wonder if at off axis angles approaching the horn wall angle (for a 60x60 then we would say 30į) if the comp driver would in fact "see" the mid ports? Or does the fact that we are using square horns here mitigate that effect like you say? Or is comparing one of Earl's waveguides to a conical horn comparing apples to oranges?

If that isn't clear as mud I'll make some drawings
Click the image to open in full size.
Click the image to open in full size.
[img]
Click the image to open in full size.
Click the image to open in full size.

Your question can be answered by studying directivity sonograms. When I've studied them, I've observed the following:

1) There are waveguides where the sound seems to 'detach' itself from the waveguide. If you look at the sonogram on some waveguides, the directivity sometimes widens or narrows at an unexpected frequency.
2) Sometimes you can have two waveguides which both *appear* to be carefully engineered, but one of them simply works better. It's not as simple as having it 'big enough'; there seems to be a lot of other factors. For instance, I've seen waveguides that seem to 'screw up' the wavefront in the first inch of the waveguide, and directivity along the entire response curve suffers.

In a nutshell, it's not as simple as making it the right size and shape. There appears to be a lot of details that impact the smoothness of the waveguide's directivity, and the overall smoothness of the frequency response.

The pictures and the sonograms above show this. Though the waveguide dimensions and geometry are similar, the sonograms are completely different.

Paul Spencer did a great series of waveguide measurements here:

Red Spade Audio: Waveguide shootout

In my situation, I'm leaning towards using a 'known good' waveguide, instead of building a conical horn. Back in the day when Lambda Acoustics was around, the owner of Lambda made a subtle change to the throat of the Unity horn, and it changed the frequency response of the horn. By quite a bit, iirc.
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Old 2nd May 2013, 05:01 AM   #847
Beau is offline Beau
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I may be completely outta line but why not a SEOS18 or larger with mids mounted appropriately?
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Old 2nd May 2013, 03:35 PM   #848
Sheldon is offline Sheldon  United States
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Originally Posted by Patrick Bateman View Post
In my situation, I'm leaning towards using a 'known good' waveguide, instead of building a conical horn. Back in the day when Lambda Acoustics was around, the owner of Lambda made a subtle change to the throat of the Unity horn, and it changed the frequency response of the horn. By quite a bit, iirc.
There were two changes: The inside corners of the horn were filled and rounded - maybe around 0.5cm radius. And the entry transition was smoothed from the CD exit to the 60 degree angle of the WG, over a cm or so. In my case the CD is a TAD 2001. As I recall, Tom Danley did not smooth the transition, in favor of quicker is better (paraphrasing). In that case disturbances would all be in the upper frequency range, with low audibility. Extending the transition could move them more into the audible range. In polar measurements of my Lambda version, I didn't see any obvious frequency wobbles.

Sheldon
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Old 2nd May 2013, 06:14 PM   #849
Tom Danley is offline Tom Danley  United States
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Hi Guys
Well this is going back a good bit now but here is the thing with the Unity horns kits Lambda sold.
I made the throat sections with a ľ inch aluminum mounting plate and made a conical taper down to where it was about 1/16 inch thick (minimizing the parallel walls). I used a 1 inch smooth tube to form the bondo into the horns corners so that everything had a Ĺ inch corner radius out to the mid holes. The net result after a flap sander was applied was a nice throat radius about 3/8 to Ĺ inch.
Anyway we used the horns in a product where I worked back then and we supplied Lambda with the precut horn parts unassembled. They assembled the horns, filled them in and painted them. They were gorgeous, they did a superb job with the paint and filler, it looked great. That little difference caused two things; The response of the horn was a little different than it had been when the crossover was figured out AND by having the corners more filled in, the mid holes produced a discontinuity which re-radiated around 4KHz then reflected off the horn wall and put a ďblack dotĒ (dip) exactly on axis.
The latter was puzzling as none of the production horns did that and they really werenít that different.

I worked out a new crossover and found 4 triangular absorbing pads put in the center part of each second flare absorbed that reflected sound. Somewhere along in there, a friend of Nickís at Lambda came into a quantity of used TAD drivers and I also worked out at least one crossover for that too.

Fwiw, the mid section is several acoustic parts and if youíre not getting to 1KHz, you might want to mount the driver on a flat board and measure the effect / design of the port / trapped volume = acoustic low pass filter by itself and not in a horn.
Also remember computer models often predict more details than you actually measure and donít include losses (which limit to a real world Q) that depend on your geometry / conditions.

With side mounted drivers, If you measured the return / cancellation frequency on a horn that came to point, you would find the effective end acoustically is not the end where a pencil tip would reach but short of that.
Sheldon, your right ideally there isnít any interaction between the drivers, they should act like one broad band driver in a CD horn, that is kind of the whole point of the design I guess haha. .
Funny thing, even the really big ones, you canít hear any separate drivers even with your head in the mouth.

Here is a full 30Hz to 15Khz map view of the horizontal pattern of an SH-50 which is a large 3 way Synergy horn with mid drivers similar to the Unity horn Nick sold. This is 3 dB per division, taken from the clf data which is averaged to 1/3 oct smoothing.
Best,
Tom
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File Type: png SH-50 H map.png (20.2 KB, 818 views)
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Old 3rd May 2013, 01:05 AM   #850
hulkss is offline hulkss  United States
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Default Synergy Horn Midrange Design Part 1 of 6

Iím progressing on the design of a Synergy horn so I thought I would post my progress here for comment. I would like to get the design on target before I build it. I hope this encourages some more people to try this Tom Danley invention.

This is the reference material I found most applicable to this project:

Synergy Horn Patent: Patent
Unity Horn Patent: Patent
Quadratic Waveguide Patent: Patent
Danley White Paper: The Tapped Horn
Hughes White Paper: Quadratic Waveguide
Horn Sonic Quality: Audioheritage Post

I'll be using the following software:
Hornresp: Hornresp
Synergy Spreadsheet: Calc v5
DATS: DATS brochure
SolidWorks: Solid Modeling
Audiolense: Juice HiFi

For this loudspeaker project I'll be using digital signal processing for crossover and loudspeaker response correction (Audiolense software). Separate amplifiers will power the midrange and high frequency drivers. As such there is no consideration in the design for implementation of a passive crossover network.

In part 2 I'll be working with Hornresp.
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