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Multi-Way Conventional loudspeakers with crossovers

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Old 4th November 2007, 12:39 AM   #1
muhy3 is offline muhy3  Australia
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Default Peerless XT25

Hi,

I am building a crossover, and I am having some problems.

The sound level out of the tweeter is too high. I have an L-pad attenuation of 4dB (Rs=1.6ohm, Rp=5.8ohm). I have included some screenshots of my current configuration.

The tweeter diaphram also appears to be moving, which makes me concerned that lower frequencies are making their way to the driver. Perhaps I built the crossover incorrectly?

Thanks!
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Old 4th November 2007, 12:41 AM   #2
muhy3 is offline muhy3  Australia
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Default 2nd pic

My 'predicted' frequency response.

I do not have fancy equipment, but when the sound gets to a point where I like it, I will decide that my crossover is adequate.
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Old 4th November 2007, 07:30 AM   #3
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I don't know a lot, but the tweeter crossover looks a little shallow.
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Old 4th November 2007, 08:54 AM   #4
muhy3 is offline muhy3  Australia
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I figured out that the tracks on my vero-board were not good and it was short circuiting certian sections, and so the whole high-pass section was being by-passed, and the tweeter was passing all the frequencies. I just fixed it up with the dremel, and now they work fine, although the tweeters sound a bit loud -- I will increase the attenuation soon.

-Vlad
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Old 4th November 2007, 09:13 AM   #5
Andy G is offline Andy G  Australia
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The XT25 nearly always requires a notch filter to tame its resonance point. Either that or you need to cross higher and steeper than you expect. A text book calculation wll generally cause distortion at its resonance point, which will often manifest itself as an unpleasant loudness. You really have to make sure the Fs point is very far down.

I can't remember the LRC values required, sorry, but a search should yield some results.
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Old 4th November 2007, 09:50 AM   #6
muhy3 is offline muhy3  Australia
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I don't see how the tweeter (with an Fs=0.5kHz) would need a notch filter since its response at that frequency is around 50dB. Although I will try to put one in next weekend when I have the time, and see what difference that makes. I've never build a crossover before, and so this is all highly experimental at this stage I hope this harshness will go away...

-Vlad
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Old 4th November 2007, 10:13 AM   #7
Andy G is offline Andy G  Australia
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50dB down ?? your x-o diagram states 2500Hz, and its 2nd order, how is that going to give you 50dB down at 500Hz?, more like 25-30dB, I'd say. Even your graph indicates around that value
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Old 4th November 2007, 10:54 AM   #8
muhy3 is offline muhy3  Australia
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I'm sorry I was talking out of somewhere hot gasses come from. So you think a notch filter would still help? 25dB down is what, like 8x less than the average output... i tried incorporating a notch filter centred around 500hz, and didnt seem to affect the response of the tweeter, or overall response.
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Old 4th November 2007, 12:24 PM   #9
rabbitz is offline rabbitz  Australia
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Have a look at the comments on the XT25 in Zaph's tweeter mishmash. The low Fs doesn't work out in the real world.

http://www.zaphaudio.com/tweetermishmash/

Read his comments on it's use.
http://www.zaphaudio.com/ZD5.html
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