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Old 4th June 2004, 08:19 PM   #21
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Here's the crossover gain only. Crossover frequency is 80Hz. Again, this is with Q set at 1/sqrt(2). (Ignore the Q=1.9, F=30 label. I forgot to remove it.)
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Old 4th June 2004, 09:42 PM   #22
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Emperial results. If I assume Q=.707 on the crossover, I can duplicate manufacture's frequency response graphs, if I assume that the crossover point varies from 50Hz to 200Hz rather than 40 to 160 as the knob is marked.
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Old 4th June 2004, 10:02 PM   #23
Ron E is offline Ron E  United States
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Right,

You can have the crossover Q anything you want, and yes it is different from the boost Q.

Q=0.707 is the 2nd order butterworth value. Q=0.5 is 2nd order Linwitz Riley

If you call the crossover B(f) as above:
B(f) = 1/sqrt((1-fc2)^2+(fc2/Q^2))

You can square B(f) and if the crossover Q is 0.707, you get a 4th order Linkwitz Riley slope.
LR4(f) = B(f)^2 = 1/((1-fc2)^2+(fc2/0.707^2))

Now you need to add in the woofer equation and you are golden. You are then well on your way to modeling speakers.

Have fun!
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Old 4th June 2004, 10:13 PM   #24
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Quote:
Originally posted by Ron E
Right,

You can have the crossover Q anything you want, and yes it is different from the boost Q.

Q=0.707 is the 2nd order butterworth value. Q=0.5 is 2nd order Linwitz Riley

If you call the crossover B(f) as above:
B(f) = 1/sqrt((1-fc2)^2+(fc2/Q^2))

You can square B(f) and if the crossover Q is 0.707, you get a 4th order Linkwitz Riley slope.
LR4(f) = B(f)^2 = 1/((1-fc2)^2+(fc2/0.707^2))

Now you need to add in the woofer equation and you are golden. You are then well on your way to modeling speakers.

Have fun!
Right arm!

The manufacture's spec sheets for the Part Express plate amps don't say what kind of slope the crossovers have. Do you reckon it's 2nd oder Butterworth?
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Old 4th June 2004, 10:22 PM   #25
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Here's another snapshot of the code and resulting graph.
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Old 4th June 2004, 10:23 PM   #26
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Graph
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Old 4th June 2004, 10:41 PM   #27
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Quote:
Originally posted by Ron E

Remember, a lowpass passes the lows and cuts the highs, and a highpass passes the highs and cuts the lows. The peaking lowpass filter here cuts the lows below the tuning frequency and protects the vented driver below resonance. This is better known as a 6th order alignment.
Note that this should read:
The peaking highpass filter.........
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Old 5th June 2004, 03:21 AM   #28
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This is so cool!

Here's a simulation of a Dayton 8" shielded DVC in a 1 cubic foot sealed box, with 6 dB bass boost at 30 Hz, no crossover rolloff.
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Old 5th June 2004, 05:26 AM   #29
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This is so way majorly cool!

I implemented the ported and passive radiator responses. For starters, I verified that I got lucky on my XLS 10" sub with the passive radiator. It's well behaved (in simulation) to 30 Hz. That's with the default 6dB boost at 30 Hz that the amp comes with.

But wait, there's more. Suppose I change the resistors in the amp to get a different bass boost curve. I can go to 20 Hz easily. The only question is how much I want it to roll off around 20-30 Hz to acount for room lift. Look at the attached chart. Bear in mind that I need a crossover point between 70 and 80 Hz.

I used a boost with Q = 1.3 at 19 Hz, set the crossover to 55 Hz [sic], and turned the volume up 8 dB. Voila!
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Old 5th June 2004, 02:43 PM   #30
Ron E is offline Ron E  United States
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Before you go too nuts with the bass boost, you might want to model excursion. Just because the EQ'd woofer will go flat to 20Hz doesn't mean it will handle much power there.. Make sure to apply boost at the tuning frequency.

Glad you are enjoying yourself!
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