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Old 7th April 2005, 04:00 PM   #1
fb is offline fb  Australia
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Default Small sealed box with linkwitz transform

I've been modelling various drivers, mostly Adire Shiva and Peerless XLS12 for use in a roughly 60L box (not limited to that small, just prefer it under 70 anyway). Most likely amp is the AA0501 from http://www.advanceae.com.au/catalog/...oducts_id=2332

I've been using the advice in this post http://www.diyaudio.com/forums/showt...070#post496070 with regards to modelling configurations.

I've been using these filters (as well as the parametric room gain simulation and the LT):
Highpass, Butterworth, n=2, fc=20
Lowpass, Butterworth, n=2, fc=50
Are these the right filters for that amp?

I seem to have gotten a good result with a 60L box + Shiva + LT fp=30 (see attached WinISD project file).

Are there any better amp/driver combinations for the situation?
Particularly to be available in Australia.

Thanks
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Old 7th April 2005, 08:19 PM   #2
simon5 is offline simon5  Canada
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The amplifier you want to use have a bad 6 dB boost at 35 Hz, did you include that in your simulations?

There is no attached file?
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Old 7th April 2005, 10:04 PM   #3
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For some reason it didn't attach the 1st time.

I plan on modding the amp according to the instructions to remove the boost.
Attached Files
File Type: zip shiva60l.zip (1.1 KB, 30 views)
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Old 8th April 2005, 06:40 AM   #4
simon5 is offline simon5  Canada
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I don't know what are you trying to do.

Can you explain?

If you want to be bulletproof for excursion under 20 Hz, use a 4th order butterworth at 16 Hz.

Then you can use your 2nd order butterworth at 50 Hz, I hope you have good tower speakers hehe!

Then for the LT, use 0.25 at 20 Hz with full imput, 240W.

Loot at this graph, it's better.

You will need to remove the bass boost.
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File Type: jpg lt.jpg (75.4 KB, 282 views)
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Old 8th April 2005, 10:50 AM   #5
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Thanks for your help. I am trying to achieve an F3 of 20hz in room response, that is why I am modelling with the parametric eq boost. (Suggested in the post I linked to).

My intention with the high pass filter was to model the 'rumble filter' on the amp. And on second thoughts I should probably bump the low pass filter up to 60hz at least.

What accoustic effect does the .25 vs .707 have for the LT? I notice the group delay seems significantly better.



If any aussies are reading suggestions on alternative amps would be appreciated.
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Old 8th April 2005, 02:24 PM   #6
simon5 is offline simon5  Canada
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You could use a 0.707 filter at 20 Hz but you must stay under 50W or you will have overexcursion. The FR curve is quite similar so I think it's better for you since I didn't know the rumble filter was at 20 Hz.

0.25 have a faster rolloff than 0.707, but excursion is lower for 0.25 so the driver is better protected.
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Old 8th April 2005, 02:36 PM   #7
simon5 is offline simon5  Canada
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I've found even better results.

Use your butterworth 2nd order at 20 Hz and 60 Hz and use LT 0.35 at 20 Hz. You can use your amplifier to full power. Way louder, but the F3 is not at 20 Hz.

Well, good luck!
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Old 8th April 2005, 06:29 PM   #8
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Be careful about excursion and power-handling. Have you looked over the design on Linkwitz's web pages?

http://www.linkwitzlab.com/thor-intro.htm
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