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Old 23rd April 2007, 05:55 PM   #1
mikee55 is offline mikee55  United Kingdom
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Default measuring a tweeter

Hello, I just learnt, with the help of richie00boy, how to measure a woofer. I now want to make a small pair of bookshelves to go on my pc. I will be using an Audax 6" fibreglass driver, which I have measured and I want to use a tweeter which its T?S parameters are unknown. With a 2 way passive in mind, what do I need to measure on the tweeter, to mate it to the mid/bass unit.

Cheers Mike
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Old 23rd April 2007, 07:55 PM   #2
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The rear chamber is sealed on tweeters your likely to look at and likely t/s specs are not listed. A frequency response graph and an impedence sweep would be a good start. The lowest crossover for a tweeter is normally stated as 2*fs or sometimes 3*fs.
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Old 23rd April 2007, 08:02 PM   #3
mikee55 is offline mikee55  United Kingdom
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Default To find Fs

Hi ocool_15, is it a simple matter of finding Fs? And would I use the same technique that I would of used for a woofer?
I used the technique from Readresearch (richie00boy)
And then use that in a crossover calculator?

Sorry for all the questions

Cheers Mike
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Old 23rd April 2007, 08:48 PM   #4
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Finding fs is the same for a woofer or tweeter, I just use a series resistance and measure the voltage drops. The peak voltage drop on the tweeter is then the Fs. A graph like below showing the impedence and frequency response will give you a good start.

You can use a crossover calculator but may find some experimentation is needed. With the woofer especially, make sure you are using the impedence at the crossover point or compensate for the voice coil inductance with a zobel.

Example Dayton Tweeter
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Old 23rd April 2007, 09:35 PM   #5
mikee55 is offline mikee55  United Kingdom
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Default Doh, confused again

Hi ocool_15,

I'm confused again, can you explain this a little clearer. I have to admit because its worded different,( no offence) its harder to understand. I wire up my system like this
Click the image to open in full size.
Quote:
With the woofer especially, make sure you are using the impedence at the crossover point or compensate for the voice coil inductance with a zobel.
Can you explain this any easier.

Cheers Mike.
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Old 23rd April 2007, 09:40 PM   #6
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Use the same technique Mike. Start at 3kHz and sweep roughly to get you in the ball park, then you can sweep with finer resolution once you have honed in on a smaller area.
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Old 23rd April 2007, 09:48 PM   #7
mikee55 is offline mikee55  United Kingdom
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Default bitin my nails

Hi Rich, I've been worried in case you tell me off for using your picture. I'll set up tommorrow and let you know what I find.

Cheers

Mike.
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Old 23rd April 2007, 09:50 PM   #8
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No worries Mike! You are more than welcome and thanks for the acknowledgement where you got it from
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Old 23rd April 2007, 10:08 PM   #9
mikee55 is offline mikee55  United Kingdom
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Default You're Welcome

Noobs click this way.

http://www.readresearch.co.uk/
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Old 24th April 2007, 09:25 PM   #10
mikee55 is offline mikee55  United Kingdom
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Default Measuring a Tweeter

Hello again, I have used my tools and found that I have

Fs=1146.9hz
Re=6.9 ohms

What else do I need to find out to implement this into my design?

Cheers Mike
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