Collaborative Tapped horn project - Page 62 - diyAudio
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Old 26th September 2007, 11:04 AM   #611
Buzzy is offline Buzzy  Singapore
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I need some help pls.
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Old 26th September 2007, 11:33 AM   #612
AndrewT is offline AndrewT  Scotland
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Hi Buzzy,
are there missing labels?
I cannot see L34, is this from Rademakers' link?

Compare your diagram with Rademakers'.
We can see that at the middle of the horn path jast at the end of the dividing mid panel the sizes to each side of this baffle are very different between the two diagrams.
Look at Rade's, on the cone side the gap from baffle end to side panel is less than the baffle end to end panel.
The gap from baffle end to end panel is smaller than gap from baffle end to side panel with the mouth opening. i.e. as the sound wave goes around the corner the cross sectional area gets a little bit bigger to match the expansion of the rest of the route.
In Buzzy's diagram the cross sectional area appears to get smaller as the wave passes around the end of the baffle.

The reflectors should bounce the wave around the corner. They are not intending to maintain cross sectional area. At the very end the two reflectors should meet in the middle and be placed at 45degrees to the end panel (90degrees to each other). But in a horn where the expansion rate is fundamental to the operation of the wave flow this "normal" rule may not apply. The only way to test if constant or expanding cross-sectional area applies or if the reflector rule applies is to build a prototype and listen if the effect is audible.
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Old 26th September 2007, 02:39 PM   #613
Buzzy is offline Buzzy  Singapore
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Rademaker's diagram does not indicate where S1,S2,S3 and S4 are . May i know where these are ?
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Old 26th September 2007, 02:46 PM   #614
AndrewT is offline AndrewT  Scotland
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Hi,
can someone give Buzzy a link to who first defined S1, 2, 3 & 4
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Old 26th September 2007, 03:35 PM   #615
MartinQ is offline MartinQ  Canada
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Buzzy is referring to the values in HornResp.

Press F1 to pull up the help screen and go to page 3. You could also look here:

http://www.diyaudio.com/wiki/index.p...=Hornresp+Help
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Old 26th September 2007, 04:15 PM   #616
AndrewT is offline AndrewT  Scotland
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Hi,
I see a question about speaker impedance earlier.

I have this idea in my head about horn impedance but it seems too good to be true.

Here goes.
If a horn is 50% efficient in it's passband, then half the input energy is dissipated as heat and the other half comes out as sound.
If the 50% that is dissipated as heat is all lost passing through Re then the other half of the input energy must be dissipated as sound driving the effective acoustic impedance of the "horn + driver". This assumes that the amp and cable resistance is near zero, but even 0.1ohms of total resistance in the drive end makes little difference to an 8ohm speaker.

Now let's assume that the Re of this 8ohm speaker is 6r0.
As stated earlier the acoustic impedance, in the passband, must also equal 6ohms (non reactive).
The total impedance seen by the amplifier is thus 12r0 (non reactive).
But horn response does not seem to show anything like this.
Where is my logic going wrong?

Can I assume that we must cut/filter the signal to the amplifier to ensure that the amp sends only a very attenuated signal that is outside the passband for any of the above to hold true?

There is probably going to be a follow up question on amplifier drive voltage once you have put me right on the above.
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Old 26th September 2007, 04:18 PM   #617
Buzzy is offline Buzzy  Singapore
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I have read that guide several times but i don't understand where S1, S2,S3 and S4 are . I will understand better if it was in the form of a diagram like rademaker's.

Thank you.
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Old 26th September 2007, 04:55 PM   #618
AndrewT is offline AndrewT  Scotland
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Hi Buzzy,
hopefully someone will draw a diagram for you.
s1, 2, 3, 4 are the areas that are input into Hornresp at each change in taper/expansion rate.
s1 is at the start of the taper.
s2 is at the cone throat.
s3 is at the mouth where the other side of the cone sends it inverted phase pressure to join up with the delayed pressure wave that travelled along the horn.
s4 is the exit mouth.
Look at the distances in Hornresp.
s1 to s2 is very short. (Rade's diagram= L12)
s2 to s3 is long (R=L23)
s3 to s4 is short (R=L34)

Have I got the description right?

Should we break the taper up to show the discontinuous expansion around the bend/reflector?
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Old 26th September 2007, 05:16 PM   #619
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Hi,
I am also new to this program but this is how I think it should be.
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File Type: jpg tapped_horn.jpg (12.7 KB, 1278 views)
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Old 26th September 2007, 05:17 PM   #620
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Another view maybe more clear?
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File Type: jpg tapped_horn25%.jpg (8.9 KB, 1261 views)
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