modding Yamaha NS-150. Measuring small-thiele parameters & new crossover - diyAudio
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Old 24th July 2009, 10:30 PM   #1
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Default modding Yamaha NS-150. Measuring small-thiele parameters & new crossover

Hi!!

I want to improve my 3-way speakers since I damaged the tweeter of one of them.

I opened the speakers enclosure and I was so disapointed with the crossover

Electrolitic capacitors and small inductors.

Click the image to open in full size.

So I decided to do some improvements to the speaker system:

- [DONE] change both tweeters (dome) with new ones (Audax TW010F1) . Since the audax tweeter is not a silk dome like the originals, i have to upper a little the second crossover frequency.
- build an entire new crossover network, with decent inductors and capacitors

I started looking for the small/thielle parameters for each driver but I was unable to find them. So I decided to measure them using this guide:
http://sound.westhost.com/tsp.htm

I got the Fs, but I cannot continue measuring because I dont know what is Is, and the page didnt says.

Click the image to open in full size.

So, if anyone can help me, I have a few questions.

1- what is "Is"? (look at the excel screenshot)
2- what do you think about the driver?
3- both "subwoofer" and "mid" are the same driver. Is that OK ??
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Old 24th July 2009, 10:42 PM   #2
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some pics

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size. Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.
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Old 26th July 2009, 06:06 PM   #3
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why nobody answer my post? I need some help, and there are lot of you that can help me!!
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Old 26th July 2009, 10:25 PM   #4
mjf is offline mjf  Austria
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hello.
holiday...............sitting in the garden (and drinking water or so)........
i am no speaker expert,but
have a look at figure 6 in the text.................
rs = 10 ohm
vref = voltage drop in the linear region above resonant frequency fs (in your diagram around 200.......300Hz; and between 10 and 20Hz)
and Is should be vref/rs (by ohm's law).
the driver has a high fs for a woofer...............no real "deep bass" if your measurement is well done.
looks like this is an "two and a half way sytem" (woofer and woofer-midrange).
have you drawn a schematic of the original network?
perhaps you do not need all this parameters because you have a box with it's speakers - so you only need to upgrade the parts and adapt the network for the tweeter................
greetings...............
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Old 29th July 2009, 12:46 AM   #5
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Quote:
Originally posted by zafira1981
why nobody answer my post? I need some help, and there are lot of you that can help me!!
Right...
http://www.diyaudio.com/forums/showt...65#post1843565
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Old 31st July 2009, 03:09 PM   #6
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Quote:
Originally posted by mjf
hello.
holiday...............sitting in the garden (and drinking water or so)........
i am no speaker expert,but
have a look at figure 6 in the text.................
rs = 10 ohm
vref = voltage drop in the linear region above resonant frequency fs (in your diagram around 200.......300Hz; and between 10 and 20Hz)
and Is should be vref/rs (by ohm's law).
the driver has a high fs for a woofer...............no real "deep bass" if your measurement is well done.
looks like this is an "two and a half way sytem" (woofer and woofer-midrange).
have you drawn a schematic of the original network?
perhaps you do not need all this parameters because you have a box with it's speakers - so you only need to upgrade the parts and adapt the network for the tweeter................
greetings...............
thank you very much, I've figured out how to do it.


I have a new question.

I want to connect a zobel network in the speaker, but according to this page http://sound.westhost.com/lr-passive.htm I have to know the inductance of the voice coil, wich I dont know. Using the excel spreadsheet I know the RLC parallel values of R, L and C, but I dont know the R and L series (I supose that L series is what I need)

Click the image to open in full size.

my question is how to find the L series, and if it is the one that should I use for the calc of the zobel network.

thanks!!!
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Old 31st July 2009, 07:04 PM   #7
mjf is offline mjf  Austria
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hello.
there is annother way to determine a rc network to compensate the increasing impedance in the upper frequency region.........
by experiment and measuring:
first measure the coil res (rvc) with a dmm(ohmmeter).
r in the zobel network should be around 50% bigger than rvc:
r = 1,5 x rvc
(powerrating a few watt).
and second try to find a cap that makes the impedance flat........
i would begin with 10uf (non polar elco) in your case.
build the network onto the speaker and measure the impedance........
change the value of the cap a little bit if it does not fit to find the flattest impedance curve............
greetings............
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Old 2nd August 2009, 03:04 AM   #8
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thank you very much, I will try to find the C by testing like you say.

By the way, I just finished building the box for measuring the VAS.

Greetings from Argentina!
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