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Old 11th February 2008, 11:32 AM   #1141
MaVo is offline MaVo  Germany
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Hi William, as usual, your comments help me alot

Using 1/4WL resonators in a TH is something i would not have thought of. Same goes for using an inductor, as i have no clue about passive components.

With the new wisdom, i made an attempt to simulate the DTS20 under the assumption, that the driver is a lab12. It looks like one and with Tom being the inventor or the dts20 and labhorn, this assumption lies close. The simulation is attached. The volume of the enclosure seems to fit the size of the dts20. The fact that my simulation has two big peaks and the dts20 has two resonators is indicating some similarity between simulation and real speaker.

And if its not the dts20, its at least a nice 20-60, maybe 100, hz labsub TH
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File Type: jpg dts20.jpg (47.7 KB, 1057 views)
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Old 11th February 2008, 04:05 PM   #1142
tb46 is offline tb46  United States
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Default MaVo_LAB12_TH_Hornresp

Hi MaVo: Looks like you added the series inductance to the Le field in the Hornresp input screen, and that is what helped smoothen the response. To be correct you may have to add the resistance of the series inductor to the Rg field.

Maybe David McBean can comment as to whether or not that approach works with his model?
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Old 11th February 2008, 04:24 PM   #1143
MaVo is offline MaVo  Germany
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Yes, i thought that i needed to add resistance, since William also spoke of it, but i dont know how much. As i said, no clue about passive components. Can you give me an equation for this? With added resistance, the horn also needs to be changed. I hope the influence wont be serious
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Old 11th February 2008, 05:02 PM   #1144
tb46 is offline tb46  United States
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Default Series Inductor

Hi MaVo: Here is a link to Parts Express's crossover inductors:

http://www.partsexpress.com/erse-16-gauge-inductors.cfm

it lists typical DCR (ohms).

I still think David McBean's input is needed to see what this does in his Hornresp model.
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Old 11th February 2008, 05:59 PM   #1145
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To filter out-of-band resonances, one can use a compression chamber as a high-pass filter, both on the rear and front of the driver. (I'm tinkering on an AkAbak script for that.) Also, those 1/4WL resonators seem te be connected to the front baffle of the driver, rather than separate tubes. This makes me think they could be bass-reflex-like tubes. (Another thing for later, as a short tryout seemd to be promising.)

As one makes a TH smaller, the upper freq go haywire. To compensate for this, one can use built-in acoustical Lowpass filters, but then the size rises again.
However, as said before, if a TH is only to be used as a rather narrow band LF device, it is very *scalable* and less dependant of the driver, compared to most other cabinets I know of.

For some further size reduction, try putting the length of the first segment to 1 (i.e. use a small compression chamber), as this segment mainly serves like a 1/4WL resonator and LP filter. Your electronic crossover will do that instead.
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Old 11th February 2008, 06:44 PM   #1146
MaVo is offline MaVo  Germany
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Quote:
Originally posted by Cordraconis
To filter out-of-band resonances, one can use a compression chamber as a high-pass filter, both on the rear and front of the driver. (I'm tinkering on an AkAbak script for that.)
I am tempted to ask, why Danley didnt use them, if this is a viable option, since he is the one who knows better than we all do. Well, maybe it is possible but has some tradeoffs he didnt want to make. Please show us the results, if you get some.

Quote:
Originally posted by Cordraconis
Also, those 1/4WL resonators seem te be connected to the front baffle of the driver, rather than separate tubes. This makes me think they could be bass-reflex-like tubes. (Another thing for later, as a short tryout seemd to be promising.)
They are not BR tubes, since they are closed on one end. Ill add a picture which shows that. The open end seems to be right besides the front membrane of the driver.

Quote:
Originally posted by Cordraconis
As one makes a TH smaller, the upper freq go haywire. To compensate for this, one can use built-in acoustical Lowpass filters, but then the size rises again.
With lowpass filter, you mean your proposed compression chambers?

Quote:
Originally posted by Cordraconis
For some further size reduction, try putting the length of the first segment to 1 (i.e. use a small compression chamber), as this segment mainly serves like a 1/4WL resonator and LP filter. Your electronic crossover will do that instead.
The first length has to have the minimum size of the driver radius in most applications. Also, its combfiltering effect will reduce distortion, as it filters out some frequencies above passband, so using it is a good idea. For best effect, set its length = 1/4WL of your upper cutoff frequency or a bit higher, to put the first notch directly above the passband and get rid of the worst distortions.
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Old 11th February 2008, 08:35 PM   #1147
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When surfing on the net i came along the patent about the tapped horn. For someone who`s interested:

http://www.wipo.int/pctdb/en/wo.jsp?...DISPLAY=STATUS

There is nothing new in the document, everything is already explained in detail by Tom on several forums. Stil it is an interesting paper to read.

Cheers,
Marcel
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Old 11th February 2008, 08:58 PM   #1148
MaVo is offline MaVo  Germany
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I am, thanks
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Old 11th February 2008, 09:47 PM   #1149
MaVo is offline MaVo  Germany
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@ Cordraconis: The patent speaks of the use of front and rear chambers, tuned for lowering the out of the passband distortion. so you were right. i hope you can model this in akabak
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Old 12th February 2008, 05:35 AM   #1150
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Default Re: MaVo_LAB12_TH_Hornresp

Quote:
Originally posted by tb46
Hi MaVo: Looks like you added the series inductance to the Le field in the Hornresp input screen, and that is what helped smoothen the response. To be correct you may have to add the resistance of the series inductor to the Rg field.

Maybe David McBean can comment as to whether or not that approach works with his model?
Hi tb46,

As far as Hornresp is concerned, increasing the values of Le and Rg (and/or Re) is the same as placing an inductor and resistor in series between the amplifier constant voltage source and the driver.

Kind regards,

David
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