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Old 24th August 2008, 04:24 PM   #161
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Dear Dave,

I just checked the offset horn in the new version of the HORNRESP.
There is something I would like to ask.
If I have a Main Horn (which is the horn usualy from the HF driver to the horn exit) and an area S2 as the offset input of the Mid driver into the main horn, at a distance L12 from the HF.
Now if there is a MF driver, it surely has a front volume and an area (hole on the sidewall of the main horn), which is not necessarely the same area, as the area of the main horn at this distance from the HF driver.

So the question is, if I can modell that configuration where the area of MF "compression driver" output is other (usualy smaller) than the area of the main horn at that special location?

Thanks,

Tamas Tako
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Old 24th August 2008, 05:09 PM   #162
contour is offline contour  Netherlands
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Are you trying to model a Unity style horn?

Best regards,

Walt
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Old 24th August 2008, 05:15 PM   #163
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YES,

Kind of...

Tamas
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Old 24th August 2008, 07:01 PM   #164
GM is offline GM  United States
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Yes, you can, I just modeled a Unity concept with four theoretical mid drivers and it looks good, though no idea how it would measure at this early stage of the project.

GM
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Old 24th August 2008, 07:30 PM   #165
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I didn´t have mich time lately so I missed some steps. Maybe I´m just not looking hard enough?
How do i vary the entrance diameter into the horn after the compression chamber in a unity-style horn? So far I used akabak for things like these, would be nice to get hornresp to do the same.
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Old 24th August 2008, 08:06 PM   #166
GM is offline GM  United States
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Assuming by 'compression chamber' you mean the filter chamber between the driver and horn, then the same way you input a compression horn, input your values in Vtc, Atc and if you're designing an offset driver BLH, then set the compression chamber's Vrc, Lrc = 0, so you can use the COMBINED RESPONSE Tool.

GM
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Old 24th August 2008, 08:12 PM   #167
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Ah thanx Sometimes, I miss the most simple things
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Old 25th August 2008, 06:54 AM   #168
Kolbrek is offline Kolbrek  Norway
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Default Re: The plot thins :)

Quote:
Originally posted by kstrain
Therefore if people do "step up to the podium" demonstrating a measured discrepancy, it is more probable that it is something quite specific in the TH design that causes the problem, such as wrong driver or horn parameters, or perhaps just an error in the measurement.
I measured the parameters of the driver I used, to make sure I was simulating what I was building .

That measured and predicted displacement could differ much puzzled me, since the SPL response was so close to the predictions. And diaphragm displacement is closely related to SPL, as the power delivered by the driver is proportional to diaphragm velocity squared, and diaphragm velocity is again equal to displacement times (2*Pi*f). So if one was off, both should be. I'm happy it turns out that physical relations still holds up .

Quote:
Originally posted by iand

1. Losses in the tapped horn acoustic system lowering the Q at resonance, so cone travel is not reduced to almost zero.
The losses probably plays a role here, but I think that the fact that the driver is "distributed" can have a greater effect. What I mean, is that the Hornresp model assumes the driver to enter the horn in a point, while in practice it enters the horn over an area. This means that the length of each segment is only defined to the precision of the driver diameter, and the resonances will be somewhat distributed and not as sharp as the model predicts.

There is also a difference between measurements and simulations in the magnitude of the peaks in electrical impedance, this may have the same explanation.

Quote:
Originally posted by iand
2. Cone flexure so that even if the average travel over the cone is close to zero the driven centre of the cone (where the accelerometer is mounted) moves one way while the outer section flexes the other way under the opposing tapped horn air pressure.

-- Bjorn, can you make any measurements with different accelerometer positions to check if this is happening?
I did make some tests other places on the diaphragm, and there is definitively a difference. One problem with this approach is that the accelerometer is a single axis device, and when mounted on the sloping cone, it will not get full acceleration in the direction of maximum sensitivity. I could try to make a wedge for it, though.

Bjørn
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Old 25th August 2008, 08:02 AM   #169
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Quote:
Originally posted by ttako
So the question is, if I can modell that configuration where the area of MF "compression driver" output is other (usualy smaller) than the area of the main horn at that special location?
Hi Tamas,

For an offset driver configuration in Hornresp, the area of the "driver output" into the side of the horn is assumed to be equal to Sd if no throat chamber is present, or equal to Atc if a throat chamber is specified. Note that the area is independent of S2. The schematic diagram attempts to show this.

Hope this helps.

Kind regards,

David
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Old 25th August 2008, 08:16 AM   #170
kstrain is offline kstrain  Scotland
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Quote:
Originally posted by Kolbrek


I measured the parameters of the driver I used, to make sure I was simulating what I was building .

Bjørn
Very good work.

Ken
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