A narrower dispersion horn is going to be longer if you want to keep the mouth size/low end directivity the same.
That makes sense. But on the spreadsheet, narrowing the dispersion makes the mouth of the horn larger too. Out of interest, why does this happen?
its just geometry. You've got three parameters: H-angle, V-angle and H pattern control limit frequency. Change any of them and the overall ht, width and depth of the horn will change in response. I've observed that holding H angle and Hpclf constant and increase ing V-angle and just the height will increase - mouth gets larger when Vangle gets larger - which is inconsistent with what you said. What parameters other than coverage angles did you change when you saw mouth get larger?
Hmm, maybe I'm misunderstanding the spreadsheet. I'll give an example:
Here's a 90x60 dispersion horn (look at the overall sizes)
By changing the horizontal dispersion to 60 degrees (the only change made), we end up with this:
So, narrowing the horizontal angle makes the horn wider, but also taller.
Here's a 90x60 dispersion horn (look at the overall sizes)
Code:
FILL IN Values that have GREEN background below (see photo): (metric equiv):
ThetaW = 90 [degrees], horizontal coverage angle (90)
ThetaH = 60 [degrees], vertical coverage angle (60)
Fc = 307.5 [Hz], lowest frequency at which horizontal pattern control to be kept (385)
td = 0.972 [inches], side of HF throat (square, needs shaping to round. For 1" driver use 0.707") 0.0246888493777 [meters]
kk = 25306 [Hz*deg*m], Keele's constant 25306 nom.
ratw = 0.65 ratio of final horizontal first expansion width to overall horiz width, 0.6 to 0.7 (0.65)
L12in = 2.25 [inches] synergy port distance from throat (adjust to get vals for HornResp Sim) 0.05715011430023 [meters]
T = 0.465 [inches] board thickness -- USE MEASURED VALUE. 0.01181102362205 [meters]
Overall Size (inside and outside horn): Values to use in HornResp Simulation (for Synergy horns):
width L= 30.000 [inches] 0.7620 [meters] S1 = 4.79 [cm^2]
height J = 19.155 [inches] 0.4865 [meters] S2 = 119.66 [cm^2] Con12 = 5.72 [cm]
depth M = 11.494 [inches] 0.2919 [meters] S3 = 1462.17 [cm^2] Con23= 17.96 [cm]
S4 = 3707.51 [cm^2] Con34 = 5.52 [cm]
Code:
FILL IN Values that have GREEN background below (see photo): (metric equiv):
ThetaW = 60 [degrees], horizontal coverage angle (90)
ThetaH = 60 [degrees], vertical coverage angle (60)
Fc = 307.5 [Hz], lowest frequency at which horizontal pattern control to be kept (385)
td = 0.972 [inches], side of HF throat (square, needs shaping to round. For 1" driver use 0.707") 0.0246888493777 [meters]
kk = 25306 [Hz*deg*m], Keele's constant 25306 nom.
ratw = 0.65 ratio of final horizontal first expansion width to overall horiz width, 0.6 to 0.7 (0.65)
L12in = 2.25 [inches] synergy port distance from throat (adjust to get vals for HornResp Sim) 0.05715011430023 [meters]
T = 0.465 [inches] board thickness -- USE MEASURED VALUE. 0.01181102362205 [meters]
Overall Size (inside and outside horn): Values to use in HornResp Simulation (for Synergy horns):
width L= 40.500 [inches] 1.0287 [meters] S1 = 4.79 [cm^2]
height J = 40.500 [inches] 1.0287 [meters] S2 = 77.21 [cm^2] Con12 = 5.72 [cm]
depth M = 26.144 [inches] 0.6641 [meters] S3 = 4470.99 [cm^2] Con23= 50.30 [cm]
S4 = 10582.22 [cm^2] Con34 = 10.39 [cm]So, narrowing the horizontal angle makes the horn wider, but also taller.
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I see what you are saying and get the same results.
My own result you can see by comparing 90x60 to 90x45 to 90x40.... only the height changes.
If you've got a recent Excel, go to the formulas tab and click "show formulas"
Then you'll see some rows - ~31-48 are hidden. Unhide them and you'll see the formulas that compute the mouth dimensions. Those formulas will tell the story.
Nom Horn calculations:
ts = =+SQRT(PI()*($C$26/2)^2)/39.37 side of squared-off throat, [m]
wnom = =+$C$27/$C$23/$C$25 nominal width per Keele approximation, [m]
@2/3A = =10^(LOG($C$25)-0.176) narrowing frequency per Keele with wnom, [Hz]
ThetaW2 = =180-(90-$C$23/2) second expansion angle, horizontal, [deg]
ThetaH2 = =180-(90-$C$24/2) second expansion angle, vertical, [deg]
D34H = =0.5*(($C$27*($C$23+$C$36)/($C$23*$C$36*$C$25))) adjusted ending width with 2nd expansion, [m]
D23H = =+$C$38*$C$28 beginning width of 2nd expansion, [m]
L34 = =+($C$38-$C$39)/2/TAN($C$36/2*PI()/180) [m]
L12 = =+$C$29/39.37 [m]
D12H = =2*$C$41*TAN($C$23/2*PI()/180)+$C$33 horizontal width at midrange port location [m]
L23 = =+($C$39-$C$42)/(2*TAN($C$23/2*PI()/180)) [m]
D12V = =2*$C$41*TAN($C$24/2*PI()/180)+$C$33 [m]
D23V = =2*$C$43*TAN($C$24/2*PI()/180)+$C$44 [m]
D34V = =2*$C$40*TAN($C$37/2*PI()/180)+$C$45 [m]
My own result you can see by comparing 90x60 to 90x45 to 90x40.... only the height changes.
If you've got a recent Excel, go to the formulas tab and click "show formulas"
Then you'll see some rows - ~31-48 are hidden. Unhide them and you'll see the formulas that compute the mouth dimensions. Those formulas will tell the story.
Nom Horn calculations:
ts = =+SQRT(PI()*($C$26/2)^2)/39.37 side of squared-off throat, [m]
wnom = =+$C$27/$C$23/$C$25 nominal width per Keele approximation, [m]
@2/3A = =10^(LOG($C$25)-0.176) narrowing frequency per Keele with wnom, [Hz]
ThetaW2 = =180-(90-$C$23/2) second expansion angle, horizontal, [deg]
ThetaH2 = =180-(90-$C$24/2) second expansion angle, vertical, [deg]
D34H = =0.5*(($C$27*($C$23+$C$36)/($C$23*$C$36*$C$25))) adjusted ending width with 2nd expansion, [m]
D23H = =+$C$38*$C$28 beginning width of 2nd expansion, [m]
L34 = =+($C$38-$C$39)/2/TAN($C$36/2*PI()/180) [m]
L12 = =+$C$29/39.37 [m]
D12H = =2*$C$41*TAN($C$23/2*PI()/180)+$C$33 horizontal width at midrange port location [m]
L23 = =+($C$39-$C$42)/(2*TAN($C$23/2*PI()/180)) [m]
D12V = =2*$C$41*TAN($C$24/2*PI()/180)+$C$33 [m]
D23V = =2*$C$43*TAN($C$24/2*PI()/180)+$C$44 [m]
D34V = =2*$C$40*TAN($C$37/2*PI()/180)+$C$45 [m]
It basically comes down to the fact that you need a bigger dimension to narrow the coverage angle, if lowest frequency for pattern control stays the same.
The height increases too because that is just determined by vertical angle and also length (which depends on horizontal angle only). For horns wider than tall, the vertical control low freq isn't as low as for horizontal control. At least for horns in that style. You could also make a horn that is longer for vertical than for horizontal to keep min frequencies the same, but I haven't got that spreadsheet going yet (and it will look funny too!).
90 degree horizontal gives a horn that isn't very long and also works well for room horizontal coverage without bouncing off near walls. 90 is too wide for vertical (my opinion) though, as it bounces off ceiling and floor directly to listener.
The height increases too because that is just determined by vertical angle and also length (which depends on horizontal angle only). For horns wider than tall, the vertical control low freq isn't as low as for horizontal control. At least for horns in that style. You could also make a horn that is longer for vertical than for horizontal to keep min frequencies the same, but I haven't got that spreadsheet going yet (and it will look funny too!).
90 degree horizontal gives a horn that isn't very long and also works well for room horizontal coverage without bouncing off near walls. 90 is too wide for vertical (my opinion) though, as it bounces off ceiling and floor directly to listener.
Thanks for the explanation Bill - I'll be interested to see how the horns with wider vertical dispersion patterns function! They would probably be quite useful for certain PA applications, even though by nature (as you've explained here with the ceiling and floor boundaries) they aren't as useful in the home.
Ok, to satisfy xrk971 (because any time I've built one of his designs I've not used foam core!), here are my latest ones:
They were the largest I could fit into a 20x30 inch foam core board sheet (307.5Hz pattern control), requiring four sheets for the pair. The hot melt glue works like solder for me, so gluing these up was a relatively painless process.
The picture shows them 'in situ', though not yet connected. I'll wire them up tomorrow.
Ok, to satisfy xrk971 (because any time I've built one of his designs I've not used foam core!), here are my latest ones:
They were the largest I could fit into a 20x30 inch foam core board sheet (307.5Hz pattern control), requiring four sheets for the pair. The hot melt glue works like solder for me, so gluing these up was a relatively painless process.
The picture shows them 'in situ', though not yet connected. I'll wire them up tomorrow.
Thanks X - I'll tidy them up a little, and then put a coat of polyurethane on them to make them shiny. 🙂
The extra midrange sensitivity has made a subtle difference, but the system sounds even more 'integrated' now...
The extra midrange sensitivity has made a subtle difference, but the system sounds even more 'integrated' now...
I think the extra pattern control has a lot to do with that. The system doesn't (to use a common phrase here) 'go omni' as soon, so there's a greater 'dimension' to stereo recordings.
One concern I had was making the mount for the compression drivers. With a 30oz. magnet they're quite heavy for my cardboard 'adaptor'. So, what I did was glue an off-cut of foam core to the top panel, which then linked to the compression drivers' mounting panel. Apart from covering some sound deadening tasks, it braces the mount well. Ribs anyone?
One concern I had was making the mount for the compression drivers. With a 30oz. magnet they're quite heavy for my cardboard 'adaptor'. So, what I did was glue an off-cut of foam core to the top panel, which then linked to the compression drivers' mounting panel. Apart from covering some sound deadening tasks, it braces the mount well. Ribs anyone?
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