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Old 8th December 2012, 11:43 AM   #1881
DrDyna is offline DrDyna  United States
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Just for funsies, and because I had the data, here's the Lab12 TH that I've fitted with TC sounds drivers, with and without the 5mH coil that's specified.
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File Type: jpg th-with and without coil.jpg (72.5 KB, 303 views)
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Old 8th December 2012, 01:58 PM   #1882
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Quote:
Originally Posted by epa View Post
hi matthew
if one would ad a coil to the system ,one also need to include the resistance of the coil.
that resistance wil have effect on it aswel

for pa you wil need a verry heavy (expencive ) coil
Yes, It would be A behemoth of gargantuan proportions, a giant wad of copper wire wound around some sort of iron core, expensive but multipurpose because it could also serve as a boat anchor, or a cannon ball

Avoiding the use of such a monstrosity would be the most affordable way to go for sure ... I think my newest revision of the SS-18PS76 doesn't look like it will need a series coil because it is smooth enough to begin with.. I have to wonder though if there are some other designs that require it, Mr Danley uses them for a reason i'm sure ...

Would the DC resistance of the coil take away from the output most significantly at the frequencies where impedance minimums occur? Or would that be an oversimplification? Im also curious about how such a thing would affect the power handling and cone control/damping of the driver?
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Old 8th December 2012, 02:57 PM   #1883
epa is offline epa  Netherlands
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it just changes a little in the curves.
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Old 9th December 2012, 03:43 AM   #1884
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Quote:
Originally Posted by DrDyna View Post
Just for funsies, and because I had the data, here's the Lab12 TH that I've fitted with TC sounds drivers, with and without the 5mH coil that's specified.
Same signal level for with and without the coil?
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Old 9th December 2012, 04:42 AM   #1885
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Quote:
Originally Posted by DrDyna View Post
Just for funsies, and because I had the data, here's the Lab12 TH that I've fitted with TC sounds drivers, with and without the 5mH coil that's specified.
That looks significantly smoother

I have to wonder if the smoother line is what the response will really look like without the inductor ..
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Old 9th December 2012, 07:22 AM   #1886
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Here is a different sort of example where this effect can actually work against you..
This response graph is from a simulation of a reasonably small sized 35hz tapped Horn, straight taper, dialed in for a Dayton PA380-8 15" woofer ..... The design was adjusted using the inductance stated in Dayton's specs list entered into Hornresponse's LE field, the result looked really good being perfectly flat between around 38hz-80hz with a slight dip around 100 and a peak above that, not bad all really ...
Doubling the LE value in this case made the curve look less flat, created gain around 55hz and loss at 65-90hz and also a loss down around 38hz, not nearly as impressive but still useable i suppose.....I'm guessing this cabinet is slightly too small and not quite tuned properly, but i wouldn't have known this if i didn't tinker with the LE value.... I attached the graph for these lackluster results ......

....
Increasing the cabinet size by around 25 liters once again flattened the response with a slight gain over the old cabinet... The newer and slightly larger cabinet looks good with both the initial LE and also the doubled value so i think that its a pretty good indication that I have the cabinet size, ratios and path length pretty well refined ..... A fun exercise ... Its too bad the PA-380 lacks XMAX, it cannot crank out extreme SPLs like some of the other drivers but It might make a good sub for someone who is on a tight budget and wants to have an affordable DIY sub for a small house party or for listening to music in their living room, den or large bedroom ....
The second response graph file is for the larger cabinet...
Attached Images
File Type: jpg PA380-8-2xLE.jpg (66.7 KB, 268 views)
File Type: jpg 312L-PA380-TH.jpg (63.0 KB, 262 views)

Last edited by Matthew Morgan J; 9th December 2012 at 07:26 AM.
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Old 9th December 2012, 11:27 AM   #1887
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by mikeford View Post
Same signal level for with and without the coil?
Yes, the only difference was changing the inductance field.
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Old 9th December 2012, 12:01 PM   #1888
AndrewT is offline AndrewT  Scotland
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Mat,
can you show the input screens for the 4 examples in post1886
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Old 9th December 2012, 12:18 PM   #1889
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by Matthew Morgan J View Post
That looks significantly smoother

I have to wonder if the smoother line is what the response will really look like without the inductor ..
I have a pair of them running now, but using a MiniDSP. If it pleases the court, I can do some measurements later today once the rest of the house is awake, without the MiniDSP, with and without the coil.
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Old 9th December 2012, 05:05 PM   #1890
DrDyna is offline DrDyna  United States
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Ok, here they are. Mic placement was right at the terminus, but all my goofy room modes are in there since I bypassed the MiniDSP.
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File Type: jpg with inductor no minidsp.jpg (92.3 KB, 239 views)
File Type: jpg without inductor or minidsp.jpg (97.3 KB, 233 views)
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