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Old 3rd February 2011, 04:30 PM   #321
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Xoc1 View Post
I decided to have a go at plotting out the horn dimensions 'as drawn'
Hi
your constriction seems to assume that the entry width into a bend is similar in width to the exit from the bend.

Surely, if one takes account of the length of taper in the bend that the exist should have width defined by that taper. An expanding taper would automatically lead to the exit width being wider than the entry width.
At mid point in the bend the width from the tip of the divider board to the outside wall of the bend should also take account of the length and taper required.

The width at ~45degress to the axial line will be larger, if no fillet is inserted into the corner. Omitting that fillet only makes for a bigger area not a constriction.
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Old 3rd February 2011, 05:58 PM   #322
soho54 is offline soho54  United States
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There are two constricted spots in the horn. You can clearly see them in Xco1 and my straightened horn pics.

They have nothing to do with the extra corner areas. The ~20cm drop down from the top is too long, and the last corner is smaller at the mouth side.

I'm not quite sure why he used a mid section S3 with a smaller than present Sd, however.

Last edited by soho54; 3rd February 2011 at 06:07 PM.
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Old 3rd February 2011, 06:19 PM   #323
Chaps is offline Chaps  Denmark
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Quote:
Originally Posted by soho54 View Post
There are two constricted spots in the horn. You can clearly see them in Xco1 and my straightened horn pics.

They have nothing to do with the extra corner areas. The ~20cm drop down from the top is too long, and the last corner is smaller at the mouth side.

I'm not quite sure why he used a mid section S3 with a smaller than present Sd, however.
If the 20cm drop from the top is too long, what will be the preferred length? And how much influence wil it have?
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Old 3rd February 2011, 06:33 PM   #324
tb46 is offline tb46  United States
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Hi,

In Post #74 I posted the updated version of the singlesheet enclosure, now called SS15. Jbell approved it in Post #78. It is what it is, what is still in question is why should there be a difference in model response and measurement. If you even out the taper by changing dimensions you are creating a new speaker. There is already at least one minor change in Xoc1's very nice drawing, the front baffle should be slightly inset into the box.

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Old 3rd February 2011, 07:41 PM   #325
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Quote:
Originally Posted by tb46 View Post
It is what it is, what is still in question is why should there be a difference in model response and measurement.
...because we're looking at measurement techniques that are possibly flawed.

FR measurement @10M with 28.3V = nice for confirming peak output, less useful for confirming alignment with a model based on SMALL signal parameters

FR measurement @1M with 2.83V - is this a valid way of measuring the FR of a horn?

What's missing here is the impedance response. It's easy to measure (with a WT3 or something similar), it's more accurate, and it will indicate clearly not only if there's alignment with the model, but if there are other issues that may be contributing to misalignment (e.g. panel flex).
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Old 3rd February 2011, 07:43 PM   #326
soho54 is offline soho54  United States
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Quote:
Originally Posted by Chaps View Post
If the 20cm drop from the top is too long, what will be the preferred length? And how much influence wil it have?
It's not really worth worrying about. It is a minor thing, but it is present in the SS15.

Quote:
Originally Posted by tb46 View Post
It is what it is, what is still in question is why should there be a difference in model response and measurement.
Where are the 1w/1m measurements showing something else?

All I have seen is jbell's 28v@10/m Smaart plot, with a 180Hz LP xover. It follows the HR graph as well as I would expect with a large signal being used. Harmonics 1, 3, 5, and 7 are were they should be, with 5 and 7 being rolled off by the xover. 7 more then 5.

I remember some questioning of the 40-50Hz area rolloff, but this is nothing more than an issue of comparing a small signal sim to a large signal reality. You are seeing an decrease in rolloff due to the greater pressures in the horn that are loading it better down low.
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Old 3rd February 2011, 07:50 PM   #327
soho54 is offline soho54  United States
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Quote:
Originally Posted by Brian Steele View Post
FR measurement @1M with 2.83V - is this a valid way of measuring the FR of a horn?
Yes, unless the horn mouth radius * .5 is 1m or more.
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Old 3rd February 2011, 07:52 PM   #328
jbell is offline jbell  United States
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Quote:
Originally Posted by soho54 View Post
I remember some questioning of the 40-50Hz area rolloff, but this is nothing more than an issue of comparing a small signal sim to a large signal reality. You are seeing an decrease in rolloff due to the greater pressures in the horn that are loading it better down low.
really.... ?????

EVERY box, I've ever tested is worse down low on a 28v10m test vs a 2.8v1m test. If for no other reason than power compression is kicking in. Most boxes when tested 28v@10m quite honestly suck compared to their 2.8v1m readings.

You're saying it's expected to get more output at 28v10m than at 2.8v1m ?? sounds voodoo to me... wonder how I research this???

If there weren't a foot of snow at the moment... I'd bring smaart outside and verify a 2.8v reading.

Last edited by jbell; 3rd February 2011 at 08:16 PM.
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Old 3rd February 2011, 08:16 PM   #329
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Now things are getting interesting. Snowed again here last night and now it's blowing a gale, so no testing outdoors for me.
It's nice to be discussing why things are Better than simulated. Talk about exceeding expectations.
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Old 3rd February 2011, 08:22 PM   #330
soho54 is offline soho54  United States
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Quote:
Originally Posted by jbell View Post
You're saying it's expected to get more output at 28v than at 2.8v ?? sounds voodoo to me... wonder how I research this???
I never said it was always expected.

Have I seen it before in a horn? Yes.
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