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Old 26th January 2012, 07:12 AM   #2531
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I had the same diskussion about port end correction with the german author of Ajhorn. After simulating dozens of designs, building them up for real nad comparing the results, we figured it was not necessary to bother
If one yould be very picky about the behaviour of ports, we would also have to look after the exakt positioning of the port (relaitve to the transducer oder other radiation sources in the same frequency domain), the distance to the end of the port inside the enclosure to the adjancing walls, if the port is close to the floor, etc...
This site hosts a little peace of software conncerning flares on ports, I never checked if the results are any good (I only use some other soft for calculating resonances), but maybe he has some insight no the topic?
Flare-it - Free Speaker Design Software
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Old 26th January 2012, 09:39 PM   #2532
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Hello all

I have a question in regards to the throat chamber, when there is more than one driver.

If I model a horn with e.g two drivers, Hornresp shows the combined area of both SD's , Vtc and Atc. But placing two drivers in the same physical space is somewhat difficult, so obviously I need two throat chambers and perhaps two rear chambers??! (think offset horn with drivers on either side)

My question: Do i simply divide the Atc by two and keep Ltc as it is (thickness of plywood). I'm inclined to say yes, comparing it to reflex ports, but things aren't always as simple as they seem
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Old 28th January 2012, 04:30 AM   #2533
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Quote:
Originally Posted by Twellmann View Post
I have a question in regards to the throat chamber, when there is more than one driver.

If I model a horn with e.g two drivers, Hornresp shows the combined area of both SD's , Vtc and Atc. But placing two drivers in the same physical space is somewhat difficult, so obviously I need two throat chambers and perhaps two rear chambers??! (think offset horn with drivers on either side)

My question: Do i simply divide the Atc by two and keep Ltc as it is (thickness of plywood). I'm inclined to say yes, comparing it to reflex ports, but things aren't always as simple as they seem.
Hi Twellmann,

The important thing is to maintain the same total chamber volumes as used in your Hornresp two-driver simulation.

The two drivers in the actual built loudspeaker can share a single rear chamber of volume Vrc and depth Lrc, or each driver can have its own separate rear chamber of volume Vrc / 2 and depth Lrc.

Similarly, the two drivers can share a single throat chamber of volume Vtc and area Atc, or each driver can have its own separate throat chamber of volume Vtc / 2 and area Atc / 2. The depth Ltc does not change.

Kind regards,

David
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Old 28th January 2012, 12:47 PM   #2534
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Quote:
Originally Posted by David McBean View Post
Hi Twellmann,

The important thing is to maintain the same total chamber volumes as used in your Hornresp two-driver simulation.

The two drivers in the actual built loudspeaker can share a single rear chamber of volume Vrc and depth Lrc, or each driver can have its own separate rear chamber of volume Vrc / 2 and depth Lrc.

Similarly, the two drivers can share a single throat chamber of volume Vtc and area Atc, or each driver can have its own separate throat chamber of volume Vtc / 2 and area Atc / 2. The depth Ltc does not change.

Kind regards,

David
Great, thanks
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Old 3rd February 2012, 06:17 AM   #2535
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Default Hornresp Update

Hi Everyone,

The Help file now has a Find tool. Product Number 2890-120203 refers.

Kind regards,

David
Attached Images
File Type: png Find.png (30.9 KB, 155 views)
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Old 3rd February 2012, 05:58 PM   #2536
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Many thanx David for the ongoing effort!!
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Old 3rd February 2012, 06:02 PM   #2537
Mark Kravchenko --- www.kravchenko-audio.com
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I need all the help i can get.

Great!
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Old 4th February 2012, 08:47 PM   #2538
tb46 is offline tb46  United States
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Hi David,

Thanks again, another useful feature.

How about adding an Isobaric button to the "Driver Arrangement" window? To automatically calculate the proper T/S parameters for an isobaric pair, with the choice of series or parallel drivers resulting from the "Drivers connected..." windows. This might be another really helpful feature.

Regards,
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Old 6th February 2012, 04:27 AM   #2539
mimura is offline mimura  Thailand
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Hi David,.

Help analyze. The Sim's look at what's wrong or not.

Thank you.

.................................................. ....................

ID=28.80
Ang=2.0 x Pi
Eg=2.83
Rg=0.00
Fta=12.40
S1=470.00
S2=800.00
Con=59.10
F12=0.00
S2=800.00
S3=1974.00
Con=66.00
F23=0.00
S3=1974.00
S4=3705.00
Con=71.80
F34=0.00
S4=3705.00
S5=6564.00
Con=51.70
F45=0.00
Sd=1225.00
Bl=27.95
Cms=7.94E-05
Rms=8.76
Mmd=156.26
Le=1.79
Re=5.40
Nd=1
Vrc=91.00
Lrc=16.00
Ap1=0.00
Lpt=0.00
Vtc=4500.00
Atc=1250.00
Pmax=1200
Xmax=5.0
Comment=c18-650el
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Old 6th February 2012, 06:10 AM   #2540
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Quote:
Originally Posted by tb46 View Post
How about adding an Isobaric button to the "Driver Arrangement" window?
Hi Oliver,

To fully integrate a rigorous isobaric model into Hornresp would require a massive amount of work. Given that the configuration is rather specialised and of somewhat limited application, I can't see myself undertaking such an ambitious project :-).

It is already possible however, to generate a reasonably accurate prediction in Hornresp using a simplified isobaric model which ignores the air volume between driver diaphragms.

PROCESS:

To model an isobaric driver array in Hornresp, specify the electrical series / parallel connection using the Driver Arrangement tool, and set Sd equal to the driver diaphragm piston area of a single driver divided by the number of drivers in the array.

For example, if the diaphragm piston area of each driver in an isobaric pair is 500 sq cm then set the value of Sd in Hornresp to 250 sq cm. The Driver Arrangement tool will automatically double this back to 500 sq cm when 2S or 2P is selected.

The attached chart shows the power response from one side of an isobaric driver pair connected in parallel and mounted in an infinite baffle. The red trace shows the Hornresp prediction using the simplified model and the blue trace shows the AkAbak result for the complete model - taking into account the effect of the air chamber between the two diaphragms.

The AkAbak response is marginally lower than the Hornresp response at higher frequencies due to the additional moving mass of the air volume between the drivers. The spike in the AkAbak response at 8600 hertz is due to a half-wavelength resonance in the air cavity.

For the purposes of the simulation the air volume between the drivers is assumed to be 1 litre, with the diaphragms being separated by an average distance of 2 centimetres.

Mass of 1 litre of air = 1.205 grams

Chamber half-wavelength resonance = 1 / 2 x 34400 / 2 = 8600 hertz

Kind regards,

David
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File Type: png Isobaric.png (71.3 KB, 103 views)
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