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Old 13th March 2003, 09:32 PM   #1
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Question simulated Linkwitz transform?

I am done with the massive tower of woofers (see thread "my cheap throw-together sub woofer") and I was planning on building a linkwitz transform circuit to get some extension out of the sub. Right now the cut-off (F3) is at about 45 Hz (not very good extension), which is what I was expecting with these cheap woofers. Actually, it's not that bad, considering that these are 8" woofers in a sealed enclosure. Now, for the question:
Since I have a built-in crossover on my receiver at somewhere around 100 Hz, could I use the active crossover on the sub amp to simulate a LT by setting it to 45Hz and boosting the level into the woofer? I am actually doing this now, and it seems to sound pretty good. I was just wondering if I am effectively doing the same thing with the crossover as I would be with a seperate circuit. It is a second order 12db/octave low pass, so it would seem to be effectively the opposite of the closed-box rolloff. I do have more than enough volume. The woofer level is set at less than half, and the receiver level is at -4db, and it is blending very well with my main speakers. Oh yeah, and it will shake everything in the house if I want it to
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Old 13th March 2003, 09:41 PM   #2
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you can put a little bump in the response by using a Chebyshev filter -- not maximally flat in the passband.
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Old 14th March 2003, 12:14 AM   #3
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Your best bet is to knock up a tunable parametric EQ, I have no links to hand, but a google search should give you some circuits to think about.

This will enable you to tune the bass extension, and with the Q, Boost, and Frequency controls you should be able to simulate most LT responses.
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Old 14th March 2003, 02:08 PM   #4
Morph is offline Morph  United Kingdom
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why don't you just make a linkwitz transform circuit. Its extreamly easy you can get a PCB for it form rod's site.
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Old 14th March 2003, 03:35 PM   #5
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why don't you just make a linkwitz transform circuit. Its extreamly easy you can get a PCB for it form rod's site.
That`s what I thought too.
The LRT-circuit is hard to beat in simplicity and a tunable parametric EQ circuit certainly is more complex to build and more difficult to adjust (IMO).
In contrary to Your idea simply to boost low frequencies, the Linkwitz Transform Circuit would also allow You not only to boost but to have influence on driver-Q or better to say box-Q (speak time response) what might be desirable .
As You have an built-in active x-over already the power supply for the LRT-circuit OP-Amp. is already there.
At least for a try, even no need for a PCB - it`s so simple You could breadboard first and see if it`s worthwhile to implement fixed later (maybe with PCB then).
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Old 14th March 2003, 03:44 PM   #6
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So, the popular vote says to build the LT... Thanks guys.
It should be easy enough to do anyway! Maybe a weekend project?
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Old 21st March 2003, 12:18 PM   #7
lubbie is offline lubbie  Canada
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here is a easy one. punch in the info and it will give you graphs and all.. even capacitor values.
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